POWER AND WATER CORPORATION SOLAR/DIESEL MINI-GRID HANDBOOK This project is supported by the Australian Government through the Australian Renewable Energy Agency (ARENA). ARENA is an independent agency established to make renewable energy technologies more affordable and increase the amount used in . ARENA is supportive of all renewable energy technologies and invests along the innovation chain – from research in the laboratory to large scale technology projects, as well as activities to capture and share knowledge. More information is available at www.arena.gov.au.

Power and Water Corporation (PWC), through its not-for-profit subsidiary Indigenous Essential Services Pty Ltd (IES), is responsible for the provision of energy, water and wastewater services to 72 nominated remote Indigenous communities and 66 outstations across the (NT). To service these communities, PWC operates over 50 isolated mini-grid power systems, most of which rely on for power generation. Electricity demand in remote NT communities is continuing to increase, as a result of Government infrastructure development, service improvement and housing programs and population growth. At the same time the price of diesel fuel is highly volatile, being affected by global supply constraints and exchange rate movements. An ongoing reliance on diesel fuel for remote power generation represents considerable and increasing financial risk. integrated, efficient solar/diesel hybrid powersystemsacross Australia. operation. This approachto foster isintendedthe ongoingdevelopment ofhighquality experience inhybrid andexpertise mini-gridsystemplanning, implementation and PWCto strengthen knowledgesharinginorderthe collectiveto industry iscommitted portfolio,the hybridisationthe entire to includesolar. with of dieselmini-gridfleet capacity ofover 1.7megawatts. initsremote PWC generation ispursuingastep-change concentrating photovoltaic plate dishesandflat solarsystemswithaninstalled elevenservicing communities. These incorporate arangetechnologies including ofsolar in remote Indigenouscommunities. There are currently solar/diesel eight hybrid systems PWC hasanovertrack 20year record ofowningandoperating solar/diesel hybrid systems fuel anddrive downoperational expenditure. technologies presentto reducethe reliance solar recognises ondiesel the opportunity Indigenous communities andhas longpursuedalternative source energy options. PWC PWCto delivering iscommitted least-cost, reliableto remote andsafe services electricity favouring byPWC orARENA. necessarilyconstitute orimplyitsendorsement, doesnot otherwise recommendation or commercial product,trade process by name, orservice trademark, manufacturer, or herein orany apparatus, orprocess product disclosed. Reference herein to any specific accuracy, completeness, orusefulnessofany views, information oradviceexpressed any warranty, express orimplied, orassumesany legalliabilityorresponsibility forthe general guidanceonly. NeitherPWC, norARENA,their employees norany of makes ARENA. the interestThe Handbookisdisseminated in ofinformation exchange and Daly River SolarResearchthe Australian by supported Governmentthrough Project The Solar/DieselMini-GridHandbook(theHandbook)was prepared byPWCthe under Disclaimer power and and power water corporation

Solar/Diesel Mini-Grid Handbook 3 1 ACRONYMS

4 1:Acronyms MJ/m LCOE –LocalLAN area network kWh –Kilowatt hour kW –Kilowatt –IndigenousEssential PtyLtdIES Services PVPSIEA –International Agency Energy Photovoltaic Power Systems Program Hz –Hertz GSS – GridStabilitySystemTKLN SolarProject GHz –Gigahertz StorageESS –Energy System ESO –Essential Operator Services CSO –Community Obligation Service CPV BOM AVR –AustralianARENA Renewable Agency Energy PWC PPA O&M –Operation andMaintenance NTG NT NPV NPC MWp MWh MW TKLN – Ti Tree, Kalkarindgi, Lake SolarProject) Nash(TKLN SCADA control –Supervisory anddata acquisition RPM – Northern –Northern Territory –Power Purchase Agreement –Concentrating SolarPhotovoltaics – voltage regulator – Net present –Net cost –Megawatt – Northern –Northern Territory Government – Net present –Net value –Revolutions perminute –Power and Water Corporation –Levelised Cost ofEnergy –Bureau ofMeteorology –Megawatt peak –Megawatt hour 2 –Megajoulespermetre-squared power and and power water corporation

Solar/Diesel Mini-Grid Handbook 5 2 CONTENTS

6 2: Contents 1 2 6 5 4 3 7 9 8 ACRONYMS. CONTENTS. 6.2 6.1 . MINI-GRIDS DIESEL 5.1 INTRODUCTION. Acknowledgments...... FOREWORD. GLOSSARY. OFDEFINITIONS 7.2 . MINI-GRIDS SOLAR/DIESEL 5.2 7.1 7.3 9.4 . 9.3. 9.2 9.1 . APPENDIX CONCLUSION. 9.6 . 9.5. PWC Diesel Engines...... Mini-Grid Definition...... 7.2.1 Constraints...... Northern Benefits...... 7.2.2 7.2.3 7.2.4 7.2.5 7.3.1 Design Considerations...... 7.3.2 7.3.3 7.3.4 7.3.5 7.3.6 7.3.7 StorageEnergy –AliceSpringsInvestigation...... Utility ScaleSolar/DieselMini-GridsInAustralia...... Remote IndigenousCommunities byPWC Serviced Load Management ...... DieselMini-Grids...... SupplyRequirementsQuality of ...... Legacy Infrastructure...... Remoteness Intermittency...... System Financing...... Solar Penetration andControl...... Solar Resource, Generators...... StorageEnergy ...... Load Control...... Modelling Other Factors...... Territory Context ...... Technologies...... Tools...... – –DalyRiver Preliminary Investigation...... Technologies...... Climate and ...... Technology Choice ...... power and and power water corporation 60 40 68 64 46 30 30 50 29 70 62 36 65 36 28 63 58 34 34 22 47 25 23 32 35 53 16 73 14 12 15 13 6 8 4

Solar/Diesel Mini-Grid Handbook 7 3 GLOSSARY OF DEFINITIONS

8 3: Glossary of Definitions times andprovide penetration annualenergy 30per cent overall. For example, asolarsystemmay reach instantaneous 80percent powerpenetration at [kW/kW])the fraction ofpowersolarprovides is the powersystem.to instantaneously usually assessedonaperannum basis. Power penetration (instantaneous penetration, penetration,the system, solarprovidestotal energy the fractionto of [kWh/kWh])is numbers: penetration energy andpowerpenetration. penetration Energy (average Penetration: Solarpenetration two typically classified by inhybrid mini-gridsystemsis supply withpowerconsumption. and controls linevoltage andfrequency, real andreactive powerflow and balancespower Mini-grid: Refersto anisolated powersystemwhichoperates autonomouslyi.e. manages the engines. tear on causeexcessivein loaddonot cycling ofgenerators, wearand whichinducesunnecessary beforethe control take offline. systemcan it Thissettingensures smallfluctuations that Minimum runtime: Referstime agenerator the minimumlengthof beonline to must a smallergenerator,the loaddemand. to whichisbettersuited loading onanenginereachesthe minimumloadfactor, the control systemwillcallonline theorderspecification ofnameplate of40percent andcanbein rating. the Typically if or rebuilding. The minimumloadingofdieselenginesisamanufacturer-recommended factor whichmay reduce engineperformance andcausepremature enginemaintenance engine. Dieselenginescanbedamagedbyextended operation the minimumload below Minimum loading: Refersthe minimumrecommendedto loadfactor (percent) ofadiesel intermittent solaroutput. system operation, for exampletimes of to managepowerstation stabilityduring controllingrelatesthe direct to andinterrupting to optimisepower ofloadsinorder generator ornetworkperformance.the Handbook, In specifically loadmanagement Load management: Refersthe contextto where to optimise the loadismanagedinorder reasonable comparison. to enablea bekept consistenttheytechnologies across must assumptionsso to input technologies withdifferent operating characteristics; however results are highlysensitive calculate LCOE,the level dependingon offinancialdetail. LCOE isusefulin comparing the existing dieselinfrastructure represents a ‘sunk cost’. There are multipleways to the solarcomponent.the capitalcostshowever of typically onlyincludes This isbecause incorporates allongoingsystem costs (for bothsolaranddieselinfrastructure), the systemover itslife (typically20years). LCOE for hybrid solar/diesel systems the samepresent hasofbuildingandoperatingthat total cost valuesupplied the as Levelised (LCOE): Cost Energy of ($/kWhor$/MWh) cost Aconstant unit ofelectricity and flywheels. different applications includingbatteries, pumpedhydro, compressed air, super-capacitors solar/diesel mini-grid. There to aretypes suited various storage energy technology periods,over short ofasolarsystemin the intermittent output suchassmoothing in smallsolar/battery systems. Short-term storage energy to provide isused power Long-term storage energy to provide isused over energy longperiods, suchasovernight a later stage. Typically storage energy isclassifiedaseither ‘long-term’ or ‘short-term’. storage:Energy Refersto away ofkeeping areserve canbeusedat that ofenergy the required(and hence CSO) isalsoincreasing. increasing supplyqualityexpectations andaginginfrastructure), the shortfall gap communities (associated withincreasing dieselfuelcost, increasing demand, electricity from customers.the increasingto remote to ofproviding cost Due services electricity inremoteto supplyelectricity the revenue Indigenouscommunities and recovered paymentthe NTG providesthe cost to PWCthe shortfall between to fund inorder Community Obligation Service (CSO):the Handbook, In term CSOrefersthe the to are regulated not the NTUtilitiesCommission. by the NTGto levelsthese minimumservice reports however they onperformance against wouldbeexpectedthat inothersimilarsized andlocatedthe NT. communities in PWC NT. levelsto beprovidedThe minimumservice byPWC outcomes arethe service basedon (power,services water andwastewater)to 72remote Indigenouscommunities the across Agreed Levels: Service PWC hasresponsibility forthe provision ofreliable essential power and and power water corporation

Solar/Diesel Mini-Grid Handbook 9 10

3: Glossary of Definitions Power Purchase Agreement (PPA): Refers to a contract between two separate entities regarding the supply and purchase of electricity. PWC utilises PPA contracts with independent third parties for the supply of electricity to six remote Indigenous communities. Under these PPA models, PWC procures only kWh units from the third party. This means, crucially, that PWC is responsible for providing, maintaining and operating the distribution infrastructure in the community (i.e. the grid network) and providing retail services (including managing the connection and disconnection of services, metering and billing, supporting the connection of small-scale customer-owned solar PV systems, informing and educating customers about water and energy efficiency etc). Under the PPA models that relate only to the supply of solar energy (i.e. the TKLN Solar Project), PWC is responsible for the provision of reliable power overall. This means that PWC continues to operate and maintain the diesel and all related power distribution infrastructure, as well as providing the aforementioned auxiliary services (retail, metering and billing etc). Under this model, PWC also ensure that sufficient diesel generation capacity exists to supply reliable power in the event that the station is offline. Power station: Refers to the primary site of power generation in remote communities serviced by PWC. PWC operates over 50 mini-grid power stations, the majority of which rely solely on diesel fuel for power generation. These power stations vary in size from 300kW up to 5MW. Quality of supply: PWC is contracted to provide reliable, safe, utility-grade power with a minimum level of service that equals the service outcomes that would be expected in other similar sized and located communities in the NT. PWC reports to the NTG on performance against agreed minimum service levels, however remote community grids are not regulated by the NT Utilities Commission. Remote Indigenous Communities: Refers to the 72 nominated remote Indigenous communities that PWC (via its not-for-profit subsidiary IES) is responsible for providing essential services (power, water, wastewater) to, on behalf of the NTG. For a map of these locations, refer to Appendix 9.1. NTG for subsidises electricity remotethe CSO. community customersvia in remotethe uniform communitiestariff represent via doesnot full cost-recovery. The of remotethe highcost to powergeneration,Due the revenue recovered from customers the NTpaythe samepricefor ($/kWh).(non-contestable) customersin electricity Uniformtariff: TheNTG operates auniformtariff policy, all that whichmeans existing dieselgenerators andassociated infrastructure. maintenance andfuelsupply. System include doesnot cost ‘sunk costs’ the suchas (LCOE),energy the lifetime supplyincludingconstruction, whichmeans electricity cost System cost: From aPWC perspective,the levelised isbasedon systemcost of cost the event (suchasduringacloudevent). ofareduction insolaroutput systems, additionalspinningreserve may berequired loadin any unmet to service inorder to manage normal communityorder loadfluctuations. thecaseofsolar/diesel In hybrid and availableto instantaneously additionalload. service Spinningreserve iscarriedin Spinning reserve: Refers ofsparethe amount to dieselgenerator isonline that capacity elsewhere. exist that betweensolar/dieselexist those the NTand mini-gridsin generation andauniformtariff. Attempts have whereto highlight beenmade similarities and associated legacyinfrastructure, demand-driven supplyexpectations, centralised andinternationallyjurisdictions include:the pre-existence ofadieselpowerstation from othersolar/dieselthem apart hybrid set that mini-gridsystemsoperating inother Indigenous community byPWCthe NT. serviced in these mini-grids The characteristics of hybrid mini-gridpowersystemusingsolaranddieselgeneration operating inaremote Solar/Diesel mini-grid:term solar/dieselthe the Handbook mini-griddescribesa In technology.thermal solar Solar:term the the Handbook In ‘solar’ refersto solarphotovoltaictechnology, (PV) not storage systems. during intermittent cloudevents. iscommonlyThis function provided byenergy Smoothing: fluctuations ofreducing Refersthe acutenessofsolaroutput the act to

power and and power water corporation

Solar/Diesel Mini-Grid Handbook 11 12 4: Foreword

4 FOREWORD Reliable power supply underpins all aspects of community development and provides the foundation for all economic and social development objectives. While diesel fuel will continue to play a fundamental role in providing reliable power supply to remote Indigenous communities, PWC’s commitment to least cost electricity service provision in remote communities is driving a progression to solar/diesel hybrid power systems. engagement andconsultation,engagement testing. andsystemacceptance and safety considerations, cultural awareness, material supplyconstraints, community key information whichmay beincludedinfuture revisions are occupational health where deliverythese requirements andspecify service differ across jurisdictions. Other regulatory, standards, service process andotherrequirements relatingto off-grid energy design, implementation andoperation specificcurrent anddocument technical, across remote Australia;to capturethe state ofknowledgeandexperience insystem efficiencytechnologies andenergy practicesenergy beingimplemented inmini-grids to includeotherrenewablethe Handbookscope expand to further isalsointended It tool. as aknowledgesharing informationtechnical systemconfiguration, on outcomes project andlessonslearnt CommunityARENA andRegional Renewable (CARRE) Energy Program, providing increases. the additionofcasestudiesprojects delivered This includes the under implementing, operating andmaintaining solar/diesel hybrid mini-gridsystems technologies improve andourcollective knowledgeandexperience designing, the Handbookbeupdated infuture that isintended It assolar, dieselandstorage • • • • • • • the Handbook: Thanksthe following areto organisations due the development whocontributed to of Acknowledgments Epuron (ownerof TKLN Solar PtyLtd) Alaskan Centre for and Power Energy University ofNewSouth Wales Centre for Renewable Energy, University CharlesDarwin CAT Projects Australian Renewable Agency Energy Power and Water Corporation Manager–Sara (Project Johnston) power and and power water corporation

Solar/Diesel Mini-Grid Handbook 13 14 5: Introduction

5 INTRODUCTION In recent years, the price of solar system components has reduced to the point that solar/diesel hybrid generation has now become economically viable for remote mini-grid generation in the NT, relative to diesel-only generation. Solar is fast becoming the lowest cost, lowest risk technology option for reducing diesel fuel consumption for remote power generation. Systems (IEA-PVPS), whichmay beofinterestto readers have beenhighlighted. Handbook,the International suchasreports publishedby Agency Energy Photovoltaic Power addressing otherareasthe solar/diesel of covered not hybrid mini-gridspectrum the in text.the main boxestext Inaddition,to this in adjacent note key sources ofinformation inAustraliain otherjurisdictions and/or internationally, attempts have to beenmade (NTG). the Handbook, Throughout where content isrelevant alsofor mini-gridsoperating remoteservicing the Northern Indigenouscommunities onbehalfof Territory Government the Handbookisfocused that primarily onmini-gridsownedandoperated byPWCthe NT, in world whichhave attributes andconstraints. distinct Therefore, to emphasise isimportant it There aretypes anddesignsofmini-gridsystemsoperating amyriad of the around associated with challenges andopportunities ‘hybridising’ existing dieselmini-grids. developersthe off-gridtap into keento the general market and publicinterested the in to newentrantsoverview the solar/diesel in mini-gridspace, includingon-gridsolar and provide solutionsfor remote powergeneration. The Handbookprovides acontextual suppliersdevelop renewablehybrid technology systemdecisionmakingandassist energy useful referencetool forthe Australian off-grid solar/diesel industry,to aidsolar/diesel diesel hybrid mini-gridsystemsinremote Australia. to bea The Handbookisintended technical, design, implementation andoperational considerations whenplanningsolar/ The overarchingto providethe Handbookis information objectivethe key of about 5.1 • • studies referredto arethe DalyRiver SolarResearch the and Project TKLN SolarProject. demonstratethe considerations application of andissuesdiscussed. case The primary the Handbook, Throughout casestudiesofexisting hybrid systemshave to beencited diesel mini-grids across the NT.diesel mini-gridsacross –implementationTKLN SolarProject ofhighpenetrationthree solarinto existing the existingsolar into dieselpowerstation DalyRiver. at Daly River SolarResearch –apreliminary Project feasibility ofintegrating assessment 300 kilowatts –5megawatts (kW) (MW). remotethe NTwithgeneration Indigenouscommunities in capacitybetween The Handbookisfocused on(2), specificallydieselmini-gridsservicing (3) (2) (1) are recognised internationally: between mini-gridsofdifferentthree scale broad classifications ofmini-grids characteristics andconstraints ofmini-gridschange.to distinguish Inorder sizes andlevels ofcomplexity however withincreasingthe operating systemsize group ofcustomers’. to powersystemsofvariousterm mini-gridis applied The the entire supplies that demandofalocalised distribution network electricity generators and, possibly, storage energy systemsinterconnectedto a The International Agency Energy definesamini-gridas ofelectricity ‘a set MINI-GRID DEFINITION MINI-GRID of internationalof work insolar/diesel mini-gridsystems. control methods. for PVPS point IEA aliterature isagood starting review or decentralised generation; AC, DCorAC andDCcoupling; andmini-grid solar/diesel mini-gridsystem architecture options, includingcentralised a good source information of regardingthe strengths andweaknesses of These canbefound www.iea-pvps-task11.org/. at PVPS IEA Task 11isalso to small-scale solarhomesystems andlarge networks. urbanelectricity the characteristics hybrid of on reports a numberof mini-grids relative InformationFurther : PVPS IEA Task 11–PV HybridsandMini-Gridsproduced urban gridandoperate autonomously). operations; oflargethe from orsections urbangridswhichcandisconnect Urban/industrial mini-grids(e.g. isolated remote gridsservicing communities across Australia Diesel mini-grids(e.g. isolated remote gridsservicing Indigenous supplying limitedpowerfor basicneeds) Village micro-grids (e.g. rural electrification indeveloping countries, power and and power water corporation

Solar/Diesel Mini-Grid Handbook 15 5.2 NORTHERN TERRITORY CONTEXT In the NT, PWC via its not-for-profit subsidiary Indigenous Essential Services Pty Ltd (IES) is responsible for the provision of reliable utility-grade electricity services to 72 nominated remote Indigenous communities and 66 outstations across the NT. To achieve this, PWC operates and maintains over 50 diesel mini-grid power stations between 300kW and 5MW capacity with a total installed diesel capacity of over 74MW and over 1 000km of power distribution lines. Of these mini-grid systems eight are solar/diesel hybrids, supplying electricity to eleven communities. These systems use a range of solar technologies, including concentrating photovoltaic (CPV) dishes and flat plate photovoltaic (PV) solar systems and have an installed capacity of over 1.7MW. The key characteristics of PWC mini-grids are outlined below. • Diesel is the primary source of power generation: this is the case even in the 16 solar/diesel hybrid systems operating. This is a key distinction from mini-grids whose primary source of power is renewable energy (e.g. solar), with the diesel generators used solely as back-up or standby supply. This distinction has operation and design implications. 5: Introduction • • the solar feeder between the solar system and the switchboard.the solarfeederthe solarsystemand between the mainswitchboard,to connected typically noloadsareto connected system interfacethe solarfeederthe powerstation and occursin is on acontinuous automated basis.the solar-diesel instances Inmost Full-automated control andSCADA: remote powersystemsare managed they are controlled not asnegative andessentially act load. the powerstation;no communicationsthese systemsand linkbetween the centralisedthe scaleof to comparison dieselpowerstation. There is customer-owned rooftop solar),these systemsare relatively smallin distributed generation isincreasing inremote communities (i.e. the dieselpowerstation.to is situated adjacent the levelWhile of grid.the caseofhybrid solar/diesel In systems,the solarpowerstation Generation iscentralised:the mini- asinglepowerstation services power and and power water corporation

Solar/Diesel Mini-Grid Handbook 17 • PWC-owned: almost all mini-grid infrastructure and assets in major remote Indigenous communities is owned by PWC including power stations, electricity distribution networks and fuel storage; the exception being some solar power stations which are operated under a PPA with a third party. PWC is responsible for providing generation, distribution and retail functions to remote community customers. • Quality of Supply: PWC is contracted to provide reliable, safe, utility-grade power and meet service outcomes that would be expected in other communities of similar size and remoteness. • Mini-grid design and operation is demand-driven: customer supply expectations are high and PWC must design and operate the power system in order to satisfy customer demand. This is distinct from mini-grids which are supply-driven whereby the design and operation are driven by the availability of the solar resource and the size and operating costs of the diesel 18 generator(s) (i.e. the supply). • PWC is licensed by the NT Utilities Commission to provide electricity to customers in remote Indigenous communities and regulated retail electricity prices are set by the NTG. The NTG has a uniform tariff policy, meaning that all non-contestable electricity customers pay the same electricity tariff. The electricity tariff is lower than the cost to produce electricity in remote Indigenous communities. • The cost to supply electricity services is much higher than revenue recovered through tariffs. The NTG provides a subsidy to PWC in the form of a community service obligation (CSO) payment to fund the shortfall. 5: Introduction • The performance of the diesel mini-grid is not regulated by the Utilities Commission, however PWC is required to satisfy minimum service levels (acceptable voltage and frequency). • PWC mini-grids are isolated systems i.e. they are not interconnected into larger networks. PWC has interconnected remote Indigenous communities into small regional mini-grid networks supplied by a single power station, where it has been economically efficient to do so. For more information regarding the operation of PWC’s remote mini-grid power systems, refer to 6.2 PWC Diesel Mini-Grids. A map of the 72 remote Indigenous communities serviced by PWC is included in Appendix 9.1. 3 2 accessed 14.05.13 Source: Victoria DalyShire www.victoriadaly.nt.gov.au/service-centres/centre/nauiyu-daly-river Source: www.bushtel.nt.gov.au accessed09.09.13 T IMORSEA fromthe community people, wholive bothinNauiyuNambiyuandat Wooliana downstream the DalyRiver. of The Traditionalthe area Owners of arethe Malak 630 Daly River (also known asNauiyuNambiyu)hasapopulation about of COMMUNITY OVERVIEW ASSESSMENT FEASIBILITY CASE STUDY: DALY PRELIMINARY RIVER COMMUNITY SOLAR/DIESEL development asolar/diesel of hybrid system. solely ondieselfuelfor power generation however PWCthe ispursuing with apeakdemandapproximately 660kW. DalyRiver currently relies DalyRiver demandat The annualelectricity isapproximately 3000MWh the community.also attract manyto visitors 5 000visitors. Renowned fishing competitions are DalyRiver held that at show withanevening carnivaltoMay attract up asports concert andart store, ahealthclinic,two schoolsandanairstrip. primary Every year in 2 andissituated approximatelythe banks on Darwin 230kmsouthof ISLAND MELVILLE COX PENINSULA

BUNTINE TIMBER CREEK T ANMI D ESRT BATCHELOR MUTIJULU KINGS CANYON

ISLAND BATHURST TANAMI

KINTORE DALY RIVER

DARWIN ROAD ADELAIDE RIVER 3 KATHERINE . Town available services inDalyRiver includealocal

LASSETER HWY PINE CREEK MATARANKA

ROAD

ROPER

HIGHWAY STUART

TI-TREE

ELLIOTT HIGHWAY SANDOVER HIGHWAY ALICE SPRINGS CREEK TENNANT

PLENTY T ABLEND A RFUSE

BARKLY B ARKLY

BORROLOOLA

HIGHWAY PLENTY TABLELANDS

CALVERT S IMPON HIGHWAY D ESRT HIGHWAY

ROAD CARPENTI

HIGHWAY EYLANDT GROOTE G ULF OF power and and power water corporation

Solar/Diesel Mini-Grid Handbook 19 CASE STUDY: TKLN SOLAR PROJECT The TKLN Solar project involved the integration of high penetration solar systems at three remote NT communities (Ti-Tree, Kalkarindgi and Lake Nash (Alpurrurulam)), to the existing diesel power stations. The populations of these communities are approximately 1704, 3405, and 4406 respectively.

TKLN Solar Project – map

A R A F U R A S E A

MELVILLE BATHURST ISLAND ISLAND

COX PENINSULA 20 DARWIN

BATCHELOR ADELAIDE RIVER T I M O R S E A

DALY RIVER PINE CREEK GROOTE EYLANDT

KATHERINE

HIGHWAY G U L F MATARANKA ROPER O F C A R P E N T A R I A

TIMBER CREEK

BORROLOOLA 5: Introduction

STUART

HWY TABLELANDS

kalkarindji ELLIOTT ROAD BUNTINE

HIGHWAY CALVERT

B A R K L Y

T A B L E L A N D HIGHWAY

BARKLY HIGHWAY

TENNANT CREEK

TANAMI HIGHWAY

D E S E R T ROAD lake nash T A N A M I (alpurrurrulam) ti-tree

SANDOVER HIGHWAY PLENTY PLENTY

ROAD KINTORE 4 Source: www.bushtel.nt.gov.au accessed 23.10.13 ALICE SPRINGS 5 Source: Australian Bureau of Statistics Census 2011 accessed 23.10.13 HIGHWAY 6 Source: AustralianKINGS Bureau CANYON of Statistics Census 2011 accessed 23.10.13

S I M P S O N LASSETER D E S E R T MUTIJULU • • • The the Handbookbecause: isincludedin TKLN SolarProject them fromdistinguishes otherhybrid systems inAustralia. their highrenewablethese systemssize and of contributions energy the average requirements dailyenergy these communities. of The large power demand at a given which instant contributesto 30 up per cent of The systems are of designedwithsolarproducingto 85percent up Alpurrurulam. turbines at 402kW, Ti Tree 324kW, wind and45kWof Alpurrurulam266kW) communities exceeds 1MWp, consisting solar(Kalkarindgi 992kWof of total renewableThe capacityinstalledacrossthe energy TKLN price volatility. security by providing future ahedge against weather events anddiesel displacing dieselconsumption withsolarwould improve supply fuel deliveries weather.to inclement due was It recognised that threethe communitiestimes suffered hadinrecent restrictions in had loadgrowth Significant recently twoof beenobserved and Renewable Remote Power Generation Program (RRPGP). the formerGovernment under providedthe project to $5million costs. NTGthe Australian and providedthe project to $4million three generationthe communitiesterm electricity andreducethe long driver project wasThe primary to minimisedieselfuelconsumption at across Australia andindeveloping countries. to play amajorrole infuture remote delivery area service electricity the assolar/dieselTKLN SolarProject hybrid mini-gridsare expected isbelievedthereit isvalue insharingknowledge andinformation on documented in detailbefore asolarsystemof PPA inamini-gridhybrid been system hasnot Epuron of owned Ltd). subsidiary Pty The development andoperation the solarpower stations, the owner of TKLN Ltd SolarPty (a wholly to perannum(MWh) purchaseagreement energy of anamount with isbasedonaPPAit contract model, withPWC entering into an government grants) using commercially available components by (part-funded significant of dieselwithhighpenetrationvolumes solar of displacing technical andfinancialviability isanexamplethe it of power and and power water corporation

Solar/Diesel Mini-Grid Handbook 21 6 DIESEL MINI-GRIDS Diesel engines have a long history of supplying remote power generation in Australia. This chapter presents the key characteristics of technology that have led to its ubiquitous use in this challenging operating context. It also outlines some of the advantages and disadvantages associated with using diesel fuel for remote power generation.

22 6: Diesel Mini-Grids 6.1 • • • • • • • • diesel enginesfor remote powergeneration relativeto othergeneration options. remote mini-grids. Listedbelowarethe key characteristics andadvantages of common generationDiesel enginesare electricity the most methodusedin DIESEL ENGINES Quick installation –dieselenginesare relativelyto install. easy increasingthe fueldelivery andfuelstorage requirements. volumes offuelwouldberequiredto generate ofelectricity,the sameamount higher that densitywould mean densityoffuel–alowenergy High energy ofdieselengineoperation.long history (O&M) requirethe prevalence doesnot to highlyspecialisedskillsdue and skillsareServicing common –dieselengineoperation andmaintenance linear). curve isnot their idealloading(~80percent) withreasonable efficiency (i.e. efficiency loadefficiencies loadsbelow –dieselenginesare toservice Good part able load fluctuations. Good loadfollowing capabilities–diesel enginesare responsiveto load. to accept required andrequiretime before minimalwarm-up beingable andloading–dieselenginescanbebrought onlinequicklyif Quick start thereforemaintenance isbasedonrunhoursand fairly predictable. to harshoperatingsuited environmentsthe NTclimate. suchas Engine High reliability –dieselenginesare robust, proven, sturdy machines, well Lowtheir widespreadto capitalcosts application –due andmanufacturing. power and and power water corporation 23 Solar/Diesel Mini-Grid Handbook 24 6: Diesel Mini-Grids

The main disadvantages associated with relying primarily on diesel fuel for remote power generation are the high operational cost of diesel fuel (and diesel fuel transportation) and the significant risk exposure to fuel price increases. Diesel fuel is currently the single largest expense of PWC for remote community service provision, representing approximately a third of the entire PWC remote community operational budget (which covers power, water and sewerage services). Another disadvantage is the ongoing maintenance requirements of diesel generators. There are limited technical service capabilities available locally in remote communities. PWC contract an Essential Services Operator (ESO) in each community to perform basic operation and maintenance of infrastructure, including the power stations. The role of the ESO includes accepting fuel deliveries, recording fuel tank levels, changing the engine oil and maintaining the power station compound. All ESOs are required to have a minimum of a Certificate II qualification in Remote Area Essential Services within 12 months of the contract commencing. PWC, in partnership with a registered training provider have developed an accredited training program (Certificate I – IV) designed to provide ESOs with a structured career path in remote area essential service provision. 6.2 kW 600 400 200 300 500 700 100 0 Typical PWC Mini-GridGenerator Sizing season). loads insummer/wet to highcooling (primarilydue to 5:1 the NTcanvarycommunities in between3:1 power consumption. The ratioto minimumbaseloadinremote ofpeakload communities where significant variation occursinseasonal (and annual) the wideloadrange iscommonthat inremote to service in order Indigenous redundancyto ensure continuous supply. This isadeliberate designdecision match load(avoidto best station generatorto provide underloading)and PWC utilisesmultiplegenerator setsofdifferent sizes eachmini-gridpower at enginesizing Diesel inChapter7Solar/DieselMini-Grids. discussed further influencesignificant theoperation over ofasolar/diesel hybridsystem, thisis time. anyon at Minimumloadfactor andspinningreserve parameters have turned canbe that the community loadin the knownhighest determined by time. Inpractice, for PWCthe spinningreserve mini-grids isgenerally setpoint the minimumvalue beavailable ofspinningreserve must that any onlineat is online. The spinningreserve isacontrol setpoint systemparameter sets that thermal efficiency. Spinning ofspare theamount that reserve is dieselcapacity ofrated50 and90percent to avoid capacity these issuesandmaximise engine maintenance orrebuilding. Generatorstypically operate between ‘cylinder glazing’ whichreduce engineperformance andmay require premature (‘underloaded’) cancauseconditions knownas ‘blow by’, stacking’‘wet and to avoid violating warranty conditions. Extended operation lowloads at operatingnot enginesfor prolonged loadfactor periodsbelow40percent generator dividedbyitsrated capacity. enginemanufacturers Most recommend which generator isonline.the the current of Anengineloadfactor is output (‘minimum loading’)andspinningreserve. These parameters largely determine Two key dieselengineoperational parameters are minimumloadfactor PWC DIESELMINI-GRIDS Generator SizeSequencingPhilosophy

GEN A UNDERLOADED OPTIMAL LOAD GEN B SPINNING RESERVE GEN C power and and power water corporation

25 Solar/Diesel Mini-Grid Handbook Configuration characteristics: • three or four generators with ascending power ratings • the 70 per cent load point of a small engine ideally corresponds to the 40 per cent load point of the medium engine • the small size plus medium engine size is usually 125 per cent of the larger engine size, providing (N-1) redundancy in the event that the largest engine fails • generators nominally rated to operate between 60 per cent and 80 per cent of their prime power rating, delivering an average load factor of 70 per cent giving optimal life and operation • generators are called in turn when the load nears the capacity of the 26 operating set. Similarly the generators change down when the load drops below the ‘call-down’ set point of the operating set, provided a minimum run time has been achieved to prevent the generation plants ‘hunting’ the . A benefit of this approach is that generally only one engine is required at any time (over the entire load range). Operating only one engine (as opposed to two in parallel), reduces the accumulation of engine run hours and therefore minimises O&M costs and potentially delays capital expenditure on engine replacement. A disadvantage of this approach is that if the small engine fails, it may be necessary to run the medium engine underloaded until the small engine is repaired. This issue is part-mitigated by the community load profile in that

6: Diesel Mini-Grids typically underloading of the medium engine would most likely only happen overnight (which is when lowest loads are experienced). During the day, when loads are higher, the medium engine would operate closer to its ideal loading and any negative effects from operating at low load (underloaded) the previous night are generally able to be ‘reversed’ (higher loads help ‘clean’ cylinder liners).

ALTERNATIVE DESIGN APPROACH One alternative engine-sizing approach is to utilise multiple engines of one size (sometimes two sizes). This approach requires multiple engines to operate simultaneously to serve the load. A benefit of this approach is that generator call-up scheduling can be optimised to share run hours across similar set sizes or prioritise run hours of particular sets. Another advantage of this approach is that there exists additional set redundancy, reduced parts type count and greater flexibility to schedule maintenance/repairs. A disadvantage is the additional investment in capital for engines, switchboards, controls and ancillaries. Another potential disadvantage is reduced overall operating efficiency due to the limited matching between load and set sizes that is possible. In a highly regulated grid, this generator sizing configuration may be preferable, as this configuration is associated with carrying much higher spinning reserve margins under normal operating conditions. training andsupport. efficiencies inserving consumables, holdingstock ofspares andoperator PWC hasstandardised all remote powerstations bymanufacturerto achieve meets international emissionsstandards. PWC procures incorporatethat engines that current highefficiency technology marginal ofproduction). cost lowest When newgeneration isrequired, plant demand (toachieve possibleoverall highest powerstation efficiency and combinationbest the communityto match ofsolaranddieselenginesize the NT,mini-grids across asgenerators may bemovedto achieve aroundthe ofsolarintothe wide-scalerollout policy iscomplementary existingto diesel life isapproximately 50000hours(around 12years). This generator rotational nominal life cycle. In2012, approximately 12engineswere relocated. Engine to operate inpowerstations where for growth the powerdemandoutpaces the whole-of-lifeto maximise the need ofgeneratorstoo small becomethat as required eachpowerstation.the loadat match to best This stemsfrom lifeasset isachieved, of175enginesismovedthe fleet between communities efficientwithin itsmost range. To managecapital costs andensure thefull replacement programto ensurethe generation acommunity at plant operates Plan, Management Under itsAsset PWC managesanenginerelocation and engineassetmanagement Diesel power and and power water corporation 27 Solar/Diesel Mini-Grid Handbook 7 SOLAR/DIESEL MINI-GRIDS The overarching objective of implementing solar into an existing diesel mini-grid is to achieve diesel fuel savings to reduce on-going operational costs and diesel fuel price exposure. This chapter highlights the key benefits, constraints and design considerations associated with implementing solar into existing diesel mini-grids in the NT.

28 7: Solar/Diesel Mini-Grids7: 7.1 BENEFITS

operational andmaintenance costs. reduced runtime hoursonlarger generators, potentially resulting inreduced generator (operatingthe load. inparallel withsolar)services This canresult in Incorporating asmallerdiesel that solarinto adieselmini-gridcanmean value proposition ofincorporating solarinto anexisting dieselmini-grid. Energy Target. Revenue raised from renewable the enhances certificates energy traded the which can be certificates Australian under Government’s Renewable greenhouse gasemissions. Furthermore solarsystemscreate renewable energy Generating powerfrom insteadofdieselfuelalsoresults solarenergy inreduced the storedtime fuelcanlast, increasing supplysecurity. generation. to offsetThe useofsolar dieselfuel consumption maythe extend season,the wet time during months a at andrely onstored dieselfuelfor power power supplysecurity. Many remotethe NTare mini-gridsin inaccessiblefor Incorporating solarinto existing dieselmini-gridsmay alsoincrease community • • NT are: The key benefitsofincorporating solarinto the existing dieselmini-gridsin include alternative sources, energy suchassolar. the remotethis riskbydiversifying community powergenerationto portfolio considerable andincreasing to PWC theNTG. financialrisk and PWC mitigates reliance ondieselfuelfor remote powergenerationtherefore represents affected byglobalsupplyconstraints andexchange rate movements. Ahigh reduced fuelpriceriskexposure –dieselfuelpriceishighlyvolatile, being diesel savings. inPWCthat Note grids, replace solardoesnot dieselcapacity. begenerated must that solar reducesthe kWh usingdieselfuel, resulting in 100 200 300 400 500 during cloudevents. storage may berequiredto ensure overall system stabilityandreliability generatorthe load(inparallel withsolar), isonlineservicing that energy the solar/diesel if that Note system designresultsthe inchanging wouldthat berequired a450kW load.to service online how incorporating DalyRiver solarat maythe generatorthe size of alter 450kW,capacities of 600kWand800kW. below illustrateThe charts Daly River powerthree station ismadeupof dieselgenerators with DALY RIVER CASE STUDY: ASSESSMENT PRELIMINARY FEASIBILITY SOLAR/DIESEL 0 (450kW) GEN 1 Daly River450kWload Diesel PowerSystem (600kW) GEN 2 (800kW) GEN 3 100 200 300 400 500 0 SOLAR Solar/Diesel HybridPowerSystem Daly River450kWload (450kW) GEN 1 (600kW) GEN 2 power and and power water corporation (800kW) GEN 3

29 Solar/Diesel Mini-Grid Handbook 7.2 CONSTRAINTS Introducing solar into an existing diesel mini-grid, particularly at medium to high penetrations, increases system complexity and introduces different risks to the power system which need to be managed. These factors must be considered early in the system design and planning phase, so that appropriate measures can be put in place to ensure the hybrid system delivers the expected results (reduced fuel consumption, increased overall power station efficiency and cost ($/kWh)). Presented below are four of the key constraints that should be considered for solar/diesel mini-grid design and implementation for remote mini-grids in the NT. To an extent, these constraints are transferable to most other solar/diesel mini-grid contexts.

30 7.2.1 QUALITY OF SUPPLY REQUIREMENTS As mentioned, PWC has responsibility for the efficient and effective provision of essential services (power, water and wastewater) to remote Indigenous communities. PWC must provide a quality of electricity supplies consistent with national standards and at a minimum:

Nominal voltages: High Voltage (HV) 11kV, 22kV Low Voltage (LV) 240V, 415V LV variation range: steady state within +6%/-10% Nominal frequency: 50Hz 7: Solar/Diesel Mini-Grids7: Frequency variation range: within 5%; +/-2.5Hz or at times when the solar system is takenthe solarsystemis offlinetimes when or at for maintenance. evening/night-timethe day throughout duringcloudevents peakloadsandalso demand. to ensurethe eventthe supplysecurityismaintainedThis isdone in of the community’sdiesel capacityisretained to service inorder entire electricity mini-grid, dieselcapacityi.e.to displacedieselfuelnot the objective is sufficient whensolarisimplementedthat intoto note aPWC isalsoimportant diesel It supplyisimportant. electricity the qualityandreliabilityeventsthe community’s on of withminimal impact shutdown. The careful configuration the these control of tohandle system cause agenerator into overto shoot frequency (lowloadingongenerator) and unload ageneratorthis event quicklyduring (openafeeder). Howeverthis may to stall. To avoidthe generator stalling,the control to systemcanbedesigned the generator’s step-loadcapabilityisinsufficient, theengine thiscancause the generator down(lowfrequency) beforethe generator overload kicks in. If timeframe. Dropping alargetimeframe loadonagenerator candrag inashort to physically beable must ‘pick-up’ the additionalloadwithinavery short spinning reserveto cover duringcloudevents, solaroutput the generators generator(s).the needfor Notwithstanding generators sufficientto becarrying andsteploadresponsethe onlinediesel the inertia capabilitiesof is Another key consideration inregardsto meetingqualityofsupplyrequirements managed. to bestrictly diesel mini-gridsystemneed the risksto which associatedthe extent withintroducing and the solarinto requirementsthe ramifications largely determine associated withsuch events, total systemoutage(powerstation blackstart).and causea Qualityofsupply the controlof the overallthe stabilityof system) canjeopardise powersystem (beyondthe powerstation’s available spinningreservethe response or capability the intermittent naturethe solarresource. of Arapid changeinsolaroutput and spinningreserve methodology. the riskassociated with to This islargely due configuration standards canhave on asstrict control impact asignificant cost Quality ofsupplyrequirements ofsolarsystemdesignand part are animportant significantly differ from other communities ofsimilarsize and remoteness. Furthermore,to supplyinterruptionsthe numberandlengthofelectricity isnot may impact the feasibility asolar/dieselmay of impact hybrid system. requirements thedesignandoperation influence themini-gridand of differ accordingthe levelto regulation of the grids. imposedon These Across Australia supplyrequirementsthe qualityof for dieselmini-grids ALTERNATIVE QUALITY OFSUPPLY REQUIREMENTS: power and and power water corporation

Solar/Diesel Mini-Grid Handbook 31 7.2.2 LEGACY INFRASTRUCTURE

The existing mini-grid infrastructure including the generator capacities, grid network and control system is another key constraint, as explained below.

Existing diesel generators – minimum loading and spinning reserve

The capacities of the existing diesel generators will limit the solar penetration level achievable. The primary constraint is diesel engine minimum loading. As mentioned, diesel engines can be damaged by extended operation at low loads and to avoid this, the minimum loading of diesel engines is typically between 40 and 60 per cent (of nameplate power rating). This varies depending on engine characteristics such as age, manufacturer, RPM and (electronic or mechanical). Due to the fact that a diesel generator must remain online at all times, the 32 minimum load factor represents a portion of the community load that is essentially reserved for diesel generation and cannot be replaced by solar generation. Diesel generators therefore have a limited capacity to ‘accept’ solar. The table and chart below illustrates this point for three different sized generators with a minimum load factor of 40 per cent servicing a 100kW load. Please note this is for illustrative purposes only. The determination of acceptable minimum loading limits on a diesel generator must be assessed on a case-by-case engine-by-engine basis taking in to consideration the engine characteristics outlined above. Furthermore it is important to note that following a period of operation at minimum load, diesel generators may require a period of high loading in order to ‘recover’ from the effects of low loading.

Example impact of diesel engine size on solar penetration (100kW load) – for illustration 7: Solar/Diesel Mini-Grids7: Minimum Resultant Loading solar power Rated (40 per cent Net load ‘available’ to penetration Generator Capacity load factor) be serviced by solar (instantaneous) 40kW A 150kW 60kW 40% (100kW – 60kW) 20kW B 200kW 80kW 20% (100kW – 80kW) 0kW C 250kW 100kW 0% (100kW – 100kW)

Solar system design ImpactExample: of Impactdiesel engineof diesel size engine on penetration size on penetration – illustration

300

250

200

k W 150

100

50

0 GEN A (150kW) GEN B (200kW) GEN C (250kW)

DIESEL SOLAR upgradethe entire of board. solar feeder, requiring anexpensive station a to connect switchboard the existing beroom power in not required. Furthermorethere may control systemmodifications are to which the extent will determine constraint. The solarpenetration control systemmay beanother the mini-grid,into the existing to beintegratedsolar system the the scaleof Depending on main switchboard Control system and suboptimal outcomes for bothsolaranddieselassets. planning systemsize andidealgenerators sizes, asanoversized systemcanhave to overestimate not Furthermore isimportant when projected loadgrowth it the existing dieselgenerators berespected. must to facilitatesystems highpenetrations ofsolar,the minimumloadconstraint of eventhat storagethe inclusionofenergy Note with insolar/diesel hybrid 2. 1. There aretwo optionsfor solarsystemdesign: upon overallto significantlypotential impact hybrid systemeconomics. this relationship.consider wellconsidered, Ifnot this constraint the has bothenginesizethat decisionsandsolararray iscrucial It capacitydecisions

penetration level (i.e.the generators thesolardesign. are tosuit modified an appropriately-sized generator isinstalled,to achieve inorder desired solar generators) or minimum loadconstraint the (i.e. tosuit the solardesignismodified the solarsystemsize isbasedonconsiderationthe existing generators of power and and power water corporation 33 Solar/Diesel Mini-Grid Handbook Distributed generation

The existence of distributed generation (such as customer-owned rooftop solar) is also a key consideration, as remote Indigenous communities are relatively small and therefore the geographical distance between distributed generation (i.e. customer-owned rooftop solar systems) is insufficient to mitigate or ‘balance out’ the intermittency of the output of these systems. This is unlike the case in larger grids such as Alice Springs, where recent ARENA-funded research undertaken by CAT Projects suggests that the geographical diversity of distributed solar generation reduces the ‘net variability’ of their output. In existing diesel mini-grid systems, a key determinant of the ‘maximum allowable size’ of customer-owned solar is the spinning reserve setpoint of the diesel generators. The extent to which the spinning reserve margin is already ‘fully exhausted’ by distributed generation is therefore a consideration for 34 the development of solar/diesel hybrid systems; particularly low penetration systems which incorporate no ‘smoothing’ mechanism such as energy storage.

7.2.3 REMOTENESS

The sheer remoteness of the mini-grids serviced by PWC is another crucial consideration when planning and developing a solar/diesel hybrid system due to the costs involved with maintaining infrastructure in remote areas. There is often limited on-site technical support available for maintenance work on remote power stations and as such there is an additional cost associated with mobilising staff and/or contractors to conduct this work. This should be a consideration for solar/diesel hybrid system development as different solar technologies have different O&M requirements, which could significantly impact overall system economics.

7: Solar/Diesel Mini-Grids7: 7.2.4 INTERMITTENCY

The integration of solar power into diesel mini-grids can be challenging; largely due to the intermittency of solar output (during cloud events). In the absence of energy storage, the diesel generator online must cover the customer load that the solar system is no longer able to service during cloud events, i.e. it must ramp up power at the same rate that the solar system reduces power in order to compensate and meet the load. While diesel generators are quick starting, it is not possible to start and synchronise an engine to pick up this additional load in the short time available during such an event. This constraint effectively puts a limit on the total power output of the solar system. Control hardware and software can be incorporated into the system to mitigate this effect by managing solar output depending on the current station operating parameters and spinning reserve available (see 7.3.1 Solar Penetration and Control). The figure below illustrates solar system output intermittency experienced at one of the TKLN Solar Project sites.

Illustrating solar intermittency (PWC 2013)

Generally, diesel engines are capable of this ramp rate (i.e. the rate of change is within its step-load capabilities), however if the overall load is greater than the engine’s capacity the overall power system stability is jeopardised.

included in the financialanalysisused theinvestmentincluded in for decisionmaking. upgrades orswitchboard expansion beconsidered costs must upfront and analysis. Furthermore any integration costs orauxiliary suchascontrol system penetrations,the initialhybrid systemfinancial beincludedin must this cost or upgrade anexisting dieselgeneratorto achieve inorder highersolarenergy the existing dieselgenerators 7.2.2). (seeSection to change Ifadecisionismade As mentioned,the solarsystemdesignmay beconstrainedthe capacityof by and powerstation infrastructure. ofexistingthe sunkcost infrastructure,the existing dieselgenerators suchas replacementand asset end-of-life at (generators, inverters etc). LCOE excludes fuel, operating costs, repairs andmaintenance (onbothdieseland solarassets) calculations. LCOEthe real isconducted on value offuture costs includingdiesel commonly basedonLevelised Cost (LCOE) ofEnergy Present andNet Value (NPV) achieved.displacement Solar/diesel financialanalysisis hybrid systemproject design andconfiguration penetration/diesel thesolarenergy andultimately fuel The amount of capital or other financing options available the system influences 7.2.5 • • • • have beensharedthose involved by the negotiations: in contractsthe PPA the basisof whichis price. The following lessonslearnt the PPA clearlyallocated risk. The projects were usingfixed price built took inexcessto 12months complete. of tender documents and The PPA negotiation commencedtender was afterthe awarded. This process TKLN PROJECT: SOLAR PPA CONTRACT MODEL –LESSONSLEARNT tolerance. tightlymonitoring specifiedwithacceptable solutionshouldbe error a singlevariable (irradiance). Therefore, inaPPA situationthe chosen However, basedon isvery modelsolaroutput to perfectly difficult it requires management good asset accurate measurement irradiance. of Solar system performance monitoring whetherfor PPA purposesor timeframe the systemsthis. behaviourallowedthe project of had calculations would have informed beenfurther by adetailedsimulation The relationship control setpoint of to solarramp rate penalty tender documents wouldthe have designdevelopment. supported dieseloperatingInclusion of principles(suchasminimumloadlevels) in the PPAto include tender documents. with PPA negotiation may have proceeded more quicklyifPWC hadelected SYSTEM FINANCING power and and power water corporation 35 Solar/Diesel Mini-Grid Handbook 7.3 DESIGN CONSIDERATIONS As mentioned, the key constraints which influence solar/diesel hybrid system design decisions in the NT are quality of supply requirements, legacy infrastructure, remoteness and system cost. Presented below are some design considerations in the context of these key constraints. Note that while solar systems are promoted for their modularity, an investigation into the most suitable design for a specific hybrid system is always required on a case-by-case basis.

7.3.1 SOLAR PENETRATION AND CONTROL

Solar penetration is typically classified by two numbers: energy penetration and power penetration. Energy penetration (average penetration, [kWh/kWh]) is the fraction of total energy solar provides to the system, which is generally assessed 36 over a fixed period (commonly per year). Power penetration (instantaneous penetration, [kW/kW]) is the fraction of power solar provides instantaneously relative to the total power being provided by all generation sources. These terms are illustrated in the charts below with examples of 15 per cent annual energy penetration and 60 per cent instantaneous power penetration.

15% Annual Energy Penetration (kWh)

1200 1000 800 Over the year, solar services approx 15% of 600 kWh total electricity demand 400 200 7: Solar/Diesel Mini-Grids7: 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

DIESEL SOLAR

60% Instantaneous Power Penetration (kW) 600 500 At times solar is 400 servicing up to 60% k W 300 of the instantaneous 200 electricity demand 100

0 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 19.00 20.00 21.00 22.00 23.00

DIESEL SOLAR kW 600 400 200 300 500 100 0 Note: this chart depicts a single point in time in asinglepoint Note: depicts this chart communities essentially operate aslowpenetration systems. controls integration required. isnot Customer-owned solarsystemsinremote configuration, a the solar anddieselsystems communications linkbetween the lowpenetrationto installedsolarcapacityunder applied the limit to Due Example Low Penetration System: integration 400kWloadwithout system configuration. savings potential) achievable isseverely limitedunderalowpenetration As illustratedthe figure in below, thepenetration level therefore (and dieselfuel spinning reserve). online dieselgenerator would ‘pick up’the additionalloadwithinitsavailable there wouldbenonegative onoverall impact powersystemstability(i.e.the wereto reduceto zerooutput instantaneously from output fulloutput 30 and80kW). Low penetrationthe solar systemsare if that designedso the static spinningreservethe powersystem(typically between margin of In alowpenetration solar/diesel hybrid system,to solarcapacityislimited Low penetration universally defined. terms are these not that to note hybrid systemhowever isimportant it Outlined belowisalow, mediumandhighpenetration solar/diesel complex systemcontrol algorithms. With increasing penetrationthe needfor comes andmore equipment auxiliary the levelon ofadditionalengineeringrequiredto maintain systemstability. Penetration levels are generally classifiedaseitherlow, mediumorhighbased SOLAR ENERGYISLIMITEDTOPOWERSTATIONSPINNINGRESERVEPARAMETER SOLAR SUPPLY 30 SOLAR ABLETO MAXIMUM k W DIESEL GENERATOR IDEAL RANGE60-80%) (OPERATING WITHIN CAPACITY 450kW DIESEL GENERATOR power and and power water corporation 370kW POWER GENERATING CAPACITY ONLINE 80kW SPARE

Solar/Diesel Mini-Grid Handbook 37 Medium penetration

In a medium penetration solar/diesel hybrid system, the solar and diesel system components must be integrated in the power station control system. The control system sends a dynamic set-point signal to the solar system, stating the maximum solar output the power system will accept. In determining this value, the control system considers instantaneous power system values including the spare capacity available (i.e. the dynamic spinning reserve) and the minimum load constraint of the online diesel generator(s). The control system operates the diesel generation that would be required to meet the load if no solar were available. This ensures there is sufficient spinning reserve to cover 100 per cent of the solar output in case there is a rapid reduction in solar output (e.g. a cloud event). Voltage and frequency inverter trip settings may also be adjusted as required to maintain stability during transient cloud events. It has been estimated that diesel fuel savings up to 20 per cent per annum can be 38 achieved with medium penetration system configurations.

Example Medium Penetration System: 400kW load with integration

DIESEL GENERATOR CAPACITY 450kW (OPERATING NEAR MINIMUM LOAD 45%) 600

500

400

270kW SPARE 300 CAPACITY ONLINE 7: Solar/Diesel Mini-Grids7: k W

200

SOLAR ABLE GENERATING 100 TO SUPPLY UP TO 220kW 180kW POWER

0 SOLAR DIESEL GENERATOR

SOLAR ENERGY CAN PROVIDE MORE THAN 7 TIMES MORE THAN THE 'WITHOUT INTEGRATION' CASE

Note: this chart depicts a single point in time

High penetration

In a high penetration solar/diesel system energy storage is required to smooth the solar output during periods of intermittency. The use of energy storage means that the diesel generators are not required to carry additional spinning reserve to cover the entire solar output. During a cloud event the energy storage system provides power for a sufficient period to allow a larger engine to be started which is able to compensate for the reduced solar output. In order for high penetration solar/diesel hybrid systems to work efficiently full integration is required between the solar and diesel control systems. be reduced unnecessarily. to the solaroutput insteadcaused enhance performance but didnot that forthis responsiveness there was werethat many Power Reducer changes so rapid responseto events like feedertrips would occur, however the cost followthe setpoint. Ononehandsensitive following setpoint was needed ‘unnecessary’ power reducerto tried stepswerethe GSS occurring as examination early system of was performance many datathat it noted power reducer step,take whichwould another20secondsto respond. By 5kW. to decrement one theGSS besufficientThis swing might to cause a few seconds, wouldthe setpoint suddenlydecreasethen increase 5kW the community 5kWloadin isswitched offa modest andbackonwithin dynamic control. Furthermorethe GSSrespondsto every value. setpoint If complex control codeto manage development andprovidethe GSS inside be conveyedto allstringinverters. This response latency required some takes approximately 20seconds for anew Power Reducer valueto (step) The Power Reducer designedfor system isnot rapid control. setpoint It contribution solarenergy of wouldcurtailment besignificant. the setpoint.to was It recognisedthis overthat the lifethe project of a rate approximately of 12kW(halfapower reducer stepsize) relative the dieselgenerator. Onaveragethis approach would underdeliver at would beforgone solaroutput 24kW of to avoid a1kWunderloadingof whichwouldthan 13(350kW) exceed by 1kW.the setpoint this example In was 349kW, power reduced ratherthe GSSwould step12(325kW) select the dieselgenerator. underloading of For example valuethe setpoint if to ever The decisionnot exceed valuethe setpoint wasto intended avoid Powerthe nearest Reducerselect value.the setpoint stepequalorbelow step sizes, e.g. Kalkarindgi. 25kWat The GSSwasto initiallydesigned coincidesthe withoneof unlessit to matchthe setpoint GSS isunable calculatedthe dieselpower station bythe singlekW. isroundedto The solar array could becontrolledtolerance.the singlekW to The setpoint Reducer stepcorrespondedto 25kW. Stepsize hasimplications.the Ideally defined by 16steps. the~400kWsolararrayFor at Kalkarindgi each Power regulatingcapable of the range in solarinverter 0–100percent output A SMA Power Reducer device was incorporated into system design experience isoutlinedbelow. Project,these behavioursto manage hasbeendeveloped. amethod This technical performance.and Through experiencethe under TKLN Solar regulationof methodanditsdynamicbehaviour willaffect economic excess isrequired solaroutput to ensure system stability. The choice As ahighpenetration system design,to regulatethe ability ordump CONTROLSOLAR METHOD to dosorisks power station stabilityandincursafinancialpenalty. to ensureis designed anacceptable rate change of ismaintained. Failure alarger generatorto start system ifnecessary. The PPA penaltyscheme the increasingthe controlto loadand generator to adjust time enough change.output the diesel This behaviourto allow hasbeendesigned output. The contributionthe GSSreducesthe effective of rate solar of System (GSS). When acloudevent occurs,the solar the GSSsupplements solaroutput.supplement Epuronthe GridStability coinedthis system The incorporatesTKLN SolarProject storage anenergy to system CASE STUDY: TKLN PROJECT PENETRATION SOLAR HIGH –EXAMPLE SYSTEM power and and power water corporation 39 Solar/Diesel Mini-Grid Handbook To address this the setpoint calculation rounds the setpoint value to the best fit power reducer step value (e.g. at Kalkarindgi 25, 50, 75kW) and the setpoint value remains stable for one minute unless a disruptive event occurs, such as a feeder shed. This avoids unnecessary step changes. If a feeder shed occurs the system reverts to a simple difference calculation so the GSS can respond dynamically to this event. The performance of these changes was modelled and validated using real system data prior to implementation. Note that since the TKLN systems were designed, refined methods for controlling string inverters have been developed. New communication schemes allow sub-second communication to inverters and linear control (versus stepped control). 40

7.3.2 SOLAR RESOURCE, CLIMATE AND TECHNOLOGY CHOICE

Assessing the available solar resource is a logical first-step when it comes to investigating the potential to implement solar into an existing diesel mini-grid. The characteristics of the solar resource, the local climate and weather patterns all influence the system configuration design, solar technology choice and system economics and as such having access to good quality, high resolution solar resource data is critical. While one minute or one hour solar resource data is sufficient to estimate system performance and economics at a high level; smaller interval solar data (<= 1 second) is required in order to appropriately design a hybrid system, mitigate system performance risk and make an 7: Solar/Diesel Mini-Grids7: informed investment decision. This is because there are many variables that influence the nature of cloud effects (and subsequently the solar resource), which can change significantly within a one minute interval, including local weather patterns, cloud size, frequency, altitude, edge shape and wind speed.

SOLAR RESOURCE DATA The Australian Government Bureau of Meteorology (BOM) has been measuring a range of solar parameters for decades. One minute solar data is available for 29 locations across Australia. This data includes a range of statistics including global, diffuse, direct and terrestrial irradiance and sunshine-seconds. To find out more go to www.bom.gov.au/climate/data/oneminsolar/about-IDCJAC0022.shtml Annual AverageSolarRadiation in the figurein below, theNT of receives most on average to24MJ/m up ofAustralia)The NT(and indeedmost hasvery goodsolarresource. Asshown BOM SolarResource Data (2009) summer howeverthe seasonalvariation asgreatthe isnot asin Top End. to belowzero. candrop night at Ingeneral community loadsare higherin temperatures are often experiencedtemperatures duringsummerandinwinter immediately precedingthe infrequent summerstorms. Prolonged highambient Humidity isgenerally lowyear-round periodsofhigherhumidity withshort The southernareathe NT(Central of Australia) experiences anaridclimate. primarily causedbyhighcooling loadssuchas airconditioners. rainfall israre. season,the wet community Ingeneral loadsoccurin the highest frequently; season(Maythe dry –September)humidityisrelatively in lowand seasons. season(October-April)the wet In rains humidityisvery highandit The Toptropicalthe NTexperiences climate, a Endof anddry wet withdistinct MEGAJOULES/M² PERDAY 12 17 16 15 14 13 PERTH 120° 24 22 21 20 19 18 EXISTING SOLARPOWER > 100KW DARWIN TRANSMISSION LINES 1000 -2000KW 600 -1000KW 300 -600KW 100 -300KW 130° ADELAIDE MELBOURNE 140° HOBART 0 SYDNEY 150° power and and power water corporation 2 BRISBANE perday. 750KM AERA 10.1 30° 20° 10° 40°

Solar/Diesel Mini-Grid Handbook 41 CASE STUDY: TKLN SOLAR PROJECT – SOLAR RESOURCE ASSESSMENT As highlighted, the characteristics of solar resource variation (rate of change and scale of change) influence the design of the output ‘smoothing’ equipment; in the case of TKLN this relates to the size of the battery inverters. There was a lack of site specific solar resource reference data to use during the design stage of the TKLN solar systems and the technical review of the proposed design. As a consequence, while the tender documents specified solar output performance requirements (in terms of acceptable rate of change of solar system output during cloud events), they did not include data indicating how quickly the solar resource might vary during a cloud event. Reference data sets were sourced during the 42 design process from a range of locations to inform the system design decisions. The only publicly available one second solar system output dataset was from a test site in Hawaii, which indicated that within a one minute interval the worst case output variation was 40 per cent. The design of the TKLN ‘smoothing system’ was based on this variation, with the inclusion of a safety margin; specifically it was designed to exceed 40 per cent of array nominal peak output. Since the commissioning of the TKLN sites, solar output variability data has become available and is showing that clouds can reduce solar output by up to 80 per cent in six seconds. Both the magnitude and the rate of solar output reduction experienced at the TKLN sites are much greater than those experienced at the Hawaii test site. This is in part due to difference in system array size, the Hawaii system is 1.5MWp, i.e. five to six times larger than the TKLN solar systems. This is consistent with research which shows that as solar system array sizes increase there is an 7: Solar/Diesel Mini-Grids7: averaging or low pass filter effect that reduces the magnitude and rate of change i.e. solar output variability is inversely proportional to array size. This is similar to the filter effect that is achieved by geographically dispersing solar systems. CAT Projects is currently undertaking research to analyse variations in instantaneous weather effects across Alice Springs and quantifying the extent to which the effects of intermittency can be reduced in this way. This research is ARENA funded; preliminary results can be found in Appendix 9.3. Experience at Kalkarindgi has shown that in peak summer conditions when solar output is at its maximum, large highly opaque clouds can reduce the solar output beyond the capacity of the ‘smoothing’ system. During the TKLN testing and commissioning phase, cloud events such as this resulted in a station . In order to address the magnitude of solar variability and avoid future black start events, the Kalkarindgi system maximum solar output has been partially limited. This risk mitigation strategy is expected to result in less than 0.5 per cent yield loss. monitored, resulting inapotential saving. cost transported,to be modules willneed installed, maintained (cleaned)and may bepreferable. ofhighefficiency that Anotherbenefit modulesis fewer modules). Therefore ifavailable landisalimitingfactor, highefficiency modules than lowerefficiency (kWh) modules(suchaspolycrystallinesame output silicon) require(such asmono-crystalline asmallerarray areato achievethe Another consideration isoverall moduleefficiency. Higherefficiency modules the NT.such as technologiesare climatesthin-film generally tohot that bettersuited meaning typically havetemperature a higher technologies; coefficient thin-film solar than ofoperating asafunction temperature.output silicon Crystalline solarmodules temperaturemodule coefficient represents the rate ofchangemodulepower temperatureas cell rises, voltagethe cell.to adrop of inopen-circuit due The technologies incurincreasingAll solarmodule lossesinmoduleperformance Solar modules specific location. trade-offs these Some of and considerations are outlined below. beconsidered appropriatemust a at to implement the most whendetermining Furthermore,there aretrade-offstypes which technology betweenmodule climates,to particular operating conditions andenvironmentsthan others. technologies andsystemcomponentsSome solarsystem canbebettersuited would have enabled the GSS design to support solar output variations. solaroutput would haveto support the GSSdesign enabled including siterelevant solarvariability informationtender intothe the solarresourceUnderstanding variabilitythe at TKLN sitesand changes.solar output received. The GSSperformance was improvedto respondto quickly response could ingenerator result overload was before GSSsupport GSS. operating incertain that conditionsThis meant the delayed GSS the responsethe and of the initialreduction solaroutput of between responses. Early there field that experience showed was latency consequencethe GSScontrol loopswere optimisedfor not fast for calculation rates of change of andpenaltycalculations. Asa The PPA was document to consider structured oneminuteintervals power and and power water corporation 43 Solar/Diesel Mini-Grid Handbook 44

Inverter size

The solar system configuration including size and number of inverters should also be considered in the context of the remoteness factor. A large number 7: Solar/Diesel Mini-Grids7: of small inverters (rather than a small number of large inverters), may be preferable so that replacement inverters can be cheaply stored on site. This would mean that if there was an inverter failure, the inverter could be swapped out relatively quickly and easily. Furthermore, this approach would minimise the impact that a single inverter failure would have on overall system output performance. These are important considerations due to the system remoteness, as there may be a delay before an appropriately qualified service technician can mobilise to site. A disadvantage of this approach that needs to be considered is higher efficiency losses.

Tracking arrays

The use of tracking arrays might also be considered to maximise the amount of solar output. As mentioned above, one of the key constraints for the communities in which PWC operates is that they are often very remote and therefore the value of additional solar generation that can be harnessed using tracking arrays needs to be carefully compared against the additional cost associated with maintaining tracking arrays. Presently for remote applications, the higher O&M costs associated with tracking arrays are often seen to outweigh any benefits in additional solar power generation. Tracking arrays also potentially increase the risk of solar output intermittency, particularly for the Top End region of the NT. This is due to tracking arrays’ higher system output in the mid-late afternoon, when cloud events are most common. Fixed array solar systems provide a partial hedge to this intermittency, because solar output for these systems is generally highest at midday, not in the mid-late afternoon. It is important also to review the climate zone for the hybrid system, noting that cyclone-prone regions have additional structural certification requirements which can limit array options. substantially increase the impact ofintermittentsubstantially cloudcover increasethe impact onsystemoutput. areas. onbeamradiation Furthermoretechnology the reliance may ofCPV also the moreO&M associated with complex system, whichiscostly inremote beconsidered must the increased of inlight technology the CPV harnessed by tracking arrays, canbe that andasnotedabovethe additionalsolarpower Australia where cloudcover isminimal. said,That technologies require CPV requires beamradiationthe aridclimate direct inCentralto andsoiswell-suited threein remote Indigenouscommunities byPWC. serviced technology CPV Concentrating solarphotovoltaicstechnologies are (CPV) currently utilised Concentrating solar photovoltaics were considered. the DalyRiver annualloadprofile. Arrayof 10, tilts 15, 20and25degrees over usablesolar power output most ayear, onaverage,the context in of PVsyst modellingresults a10degree indicatethat array producesthe tilt to undertake repairstechnician personnel andmaintenance. overtracking arrays,the coststo associated due withmobilising The remoteness DalyRiver of contributed fixedthe choice of to arrays the preferredwereto be deemed option. toxicitythe to associated telluride, withcadmium arrays monocrystalline output,telluride modulesachievedcadmium the highest however due providedthe most ‘usable’ solarenergy. The resultsthe indicatedthat technologies andarraymodule to determine whichcombinationtilts PVsyst modellingsoftware (www.pvsyst.com) wasto compare used between fixed tracking or arrays. comparisontechnologies and wasthree panel types of madebetween A solarfeasibility for assessment DalyRiver was undertaken inwhicha TECHNOLOGY ASSESSMENT DALY ASSESSMENT PRELIMINARY FEASIBILITY RIVER: SOLAR/DIESEL power and and power water corporation 45 Solar/Diesel Mini-Grid Handbook 7.3.3 GENERATORS

Two engine technologies – ‘low load’ and ‘variable speed’ engines – may enhance diesel engine ability to accommodate increasing the potential solar energy contribution. While these technologies are not in widespread use, they are under active commercial development and they may find widespread use in the future. These technologies are outlined below.

Low load diesel engines

As mentioned, most diesel engine manufacturers for stationary applications recommend a minimum loading to avoid contravening warranty conditions. Generally speaking diesel engines can run at low loads for limited durations with negligible effects however on-going operation at low loads can result in engine damage including cylinder ‘glazing’ and increased ‘blow-by’. Operating at low load 46 means less fuel is burned, this means reduced cylinder pressure during combustion and reduced energy dissipated. Lower cylinder pressure means the cylinder rings are not forced out to seal the cylinder as effectively. This allows greater ‘blow-by’ of combustion products into the oil sump. This also means that more oil remains on the cylinder surface. Over time this oil carbonises and the grooved cylinder lining surface becomes clogged with carbon. That said, there are degrees of ‘low load’ and successful operational experience outside of manufacturers’ recommended minimum load ratings has been reported. A small number of remote power system operators in Australia have used diesel engines at low load in wind/diesel and solar/diesel systems. These operate down to very low loads (approximately 10 per cent) but operate at higher loads other times to ‘undo’ the effects of low load operation, using oil sampling to monitor for deleterious effects. Reportedly, operational experience to date (mostly with wind diesel systems) has demonstrated no increase in O&M costs while achieving high renewable energy penetrations. 7: Solar/Diesel Mini-Grids7:

Variable speed diesel engines

An alternative way of providing low load operation is to allow diesel engines to operate at variable speeds. Variable speed generator operation is common in large wind turbine systems and the same technology has been employed in diesel engines to allow variable speed constant frequency operation. Power electronics technology allows the diesel engine speed to vary with loading. The power electronics can produce a stable 50 or 60Hz output over a wide range of speeds. The key benefit of this approach is that the deleterious operating conditions of fixed speed low load operation are avoided, ensuring engine longevity. Engine part-load efficiency is improved when speed varies according to load, compared to fixed speed low load operation. The main disadvantage of this technology is the need for power electronics to convert the variable frequency alternator output into a fixed frequency output. This technology exists but it adds expense and complexity compared to a simple diesel engine – alternator- AVR combination. There are a number of companies offering variable speed generators but to date the largest size commercially offered is 125kW, too small for many mini-grid systems.

3. 2. 1. provide anumberofdifferent functions. are:these functions Most-commonly storageEnergy systemscanbeincorporated into solar/dieselto mini-grids 7.3.4 diesel generators. theoreticallythis can allowextendedsystems operation withsmaller(orno) the solarsystemwithpeakdemand. of peak output Inhighpenetration storageEnergy systemsfor loadshifting applications areto match used Load shifting available. level andsuppliesacertain ofshort-term predictabilityoutput ofsolarpower a smallerdieselgenerator. Effectivelythe solar this achievesthe smoothingof thus canbeconsidered aform ofspinningreserve whichallows operating with to hours)periods (minutes of reduced orincreased production solarenergy and storageEnergy systemsfor loadfollowing applications areto buffer used short Ramp rate smoothing frequency andvoltage excursions couldthat to gridstability. bedetrimental ramp rates ongenerating bothsolaranddiesel, equipment whichlimits thus relativelyand smallamounts ofenergy. Effectivelythis achieves reduced amountssignificant theorder ofpower tominutes, ofseconds timescaleson for type ofapplication,this in to provide storagethe energy to beable systemhas high for dieselgeneratorsto match instantaneous changes. Characteristically operationtoo the variability is the mini-gridwhen ofsolarsystemoutput of storageEnergy systemsfor powerqualityapplications areto ensure used stable Power quality areThese functions outlinedinmore detailbelow.

higher powerpenetration (‘short-term storage’) energy the rampto smooth ratethe event in ofvariability ofsolaroutput andenable storage’)energy to regulate powerquality(voltage/frequency/reactive power)(‘short-term energy penetration)energy storage’). (‘long-termenergy to bettermatchto shift solarresource load withdemand(enablinghigher and they canberatedand capacityandpower by energy capacity. electrochemical, electrothermal, electromechanical, andelectromagnetic; Technologies usedfor storage energy systems canbeclassifiedas ENERGY STORAGE power and and power water corporation 47 Solar/Diesel Mini-Grid Handbook 48

There are various energy storage technology types suited to different applications including batteries, pumped hydro, compressed air, super-capacitors and fly wheels. Further information about ESS technology options can be found in Appendix 9.4 Energy Storage Technologies. 7: Solar/Diesel Mini-Grids7: The main drivers for the cost of energy storage are cost per unit of storage capacity ($/kWh) and cost per unit of charge/discharge capacity ($/kW). For a good comparison of various storage options it is important to factor in the expected number of cycles the system can undergo before major replacements are required. Thus, depending on system requirements a storage technology may be economically feasible in a low energy, high power application, or vice-versa, or take the middle ground between the two. Only careful assessment can reveal the actual economics of a particular solution under a given use case. Also note that any economic viability must also yield to technical viability for the intended application. Many different energy storage solutions are offered which can make it quite challenging to choose the correct system for the desired application. In the selection process it is important to determine: • the desired service the energy storage system will provide; different types of energy storage technologies are more suited to certain functions. For example, pumped hydro storage is not suitable for power quality applications. • the energy and power capacities of the energy storage system and whether these are adequate for the intended application. Not all energy storage applications require large amounts of energy. For example in power quality applications the amount of power available is of more significant importance than the amount of energy. • • • • • 100 percent. nominalcharge current accept batteries willnot level astate at ofcharge near charge anddischargeto bewellunderstood. states has For example, most storagethe energy the behaviour of to bepossible allprobable systemat this to beintegrated has it the overall into control strategythe mini-grid. of For storage ofanenergy technical andeconomic benefit the system maximise the control requirements andmanagement storagethe energy of system. To storageenergy technologies. mature. Thus, aconsiderable ofriskcanbeinvolved amount in choosing technologies offered have beenoperated not sufficiently tobe considered long decades however, consolidated andmanythe moment the market isnot at development storagetakenthe energy over has place in the past sector storagethe energy the maturitytechnology. of Muchresearch and the overall of make portion upasignificant storage ofanenergy cost system. requiredto integrate the powergrid.them into can equipment This ancillary AC power. Thus, (inverters, additionalequipment transformer, controls) are the powergrid. Many storage devices operate onDCorvariable frequency required equipment the ancillary to integrate storagethe energy systeminto ofavailablethe amount to know for energy important sizingpurposes. Similarly, aflywheelcanonlyprovide powerinagiven range ofspeed. is It state 40percent ofchargebelow about willhave life ashortened cycle. number canbemisleading. For example, isdischargedthat aleadacidbattery storedenergy storage inanenergy systemas itscapacity. However,this content.the usableenergy Generally, manufacturerstotal the willstate the manufacturer’s designlife for storagethe energy device israrely achieved. systems. Furthermorethe harshoperating the NTare conditions that of such standards were adheredto bymanufacturers ofemerging storage energy and reported basedongiven standards, always isnot similar that it clear while cycle life fortraditional storage energy (leadacid batteries) is assessed in considerationthe overall of systemeconomics andfeasibility. Inaddition, thereforeto includereplacementon asolarsystemand cost isimportant it to calculate for paybackthe fullperiodused last Often these devices donot electrochemical storage devices (i.e. batteries), whichhave alimitedcycle life. the expected cycle life storagethe energy of system;the caseof especiallyin power and and power water corporation 49 Solar/Diesel Mini-Grid Handbook 7.3.5 LOAD CONTROL

LOAD MANAGEMENT The term load management generally applies to the field of electricity service provision where the load is managed in order to optimise generator or network performance. There is a myriad of methods by which load management can be achieved, including supply-side and demand-side driven responses. For the purpose of the Handbook, the term load management is synonymous with load control, by which loads are directly controlled by the power station control system when required in order to manage grid stability during cloud events.

50 As discussed, a challenge with solar systems operating in mini-grids is that when a cloud passes over the panels causing shading, their power output can drop at a very high rate which can cause power system stability issues. Load management techniques such as load control may help mitigate this risk, by providing the power station control system the ability to instantaneously switch off loads temporarily if a cloud-event occurs or a rapid reduction in solar output is detected. Effectively being able to directly control loads increases the power system spinning reserve, as they can be taken offline instantaneously should solar power be lost (e.g. due to a cloud event). In terms of the power system, this results in the diesel generators not being required to suddenly ‘pick-up’ this additional load (that the solar system was no longer able to support), reducing the risk of power system instability. There is also the potential for load control to increase the amount of solar power that can be ‘accepted’ by the control system under normal operating conditions (i.e. not 7: Solar/Diesel Mini-Grids7: only during a cloud event), by effectively increasing the amount of spinning reserve available in the power station. Essentially, this application of load management performs a similar role to that of energy storage in solar/diesel hybrid systems; it provides a buffer between solar output intermittency and the diesel generator response time.

ENERGY EFFICIENCY PWC is actively involved in improving the efficiency of the operation of its infrastructure in remote communities. PWC is also committed to assisting customers to better understand energy and make informed decisions about managing their energy use. For more information go to: www.powerwater.com.au/sustainability_and_environment/ save_on_power further information.further Please seeAppendix9.6Load – Management Technologies for or checkbitssimilar. communicationtask bywaythis protocols manage that ofsignalencryption the desired that communication isachieved.the various Often is it and alsofrom noiseandinterference, electrical canbeguaranteed it that so transmissionsignal issecure. This issecure from botha ‘hacker’ perspective the the communicationtechnologies is to allof iscrucial that One aspect example airconditionersturn off whichareto over scheduled night). load (amps oreven orkW) the load(for informationtime schedulingof about the powerconsumptionthe actual the load(onoroff),the status of of such as system informationbi-directional the central canbefedto back control location, one-wayleast (from central ideallyisbi-directional. controlthe load)but to Ina the controllableor buildingswith loads. This communication to beat needs transmit informationthe central from controlthe individualhouses to location network,In aloadmanagement amethodofcommunication isrequiredto chargers andotherappliances. thereheaters pressure andpoolpumps isindustry vehicleto includeelectric hardware. towardstargetedThe standard is residential air-conditioners, water they are that capableofcommunicatingso control withloadmanagement concerned orAustralian withimposingstandards onimported goods electrical to standardisegroupstechnology. smart-grid Australian Standard AS4755 is There isgrowing pressure from industry, conservation utilitiesandenergy the powersupplyduringcloudevents.increasedto riskinginterruptions without power ifrequired.this way, In the systemcanbe the solarcontributionto asteadyrate.on at Alarger generatorto supplyadditional turned on wouldbe switched off.the controller loadsback time Afterthe select wouldswitch ashort the onlinespinningreserve isinsufficient to cover thefullload, loadsare select the solar.of the overall If the dieselgenerator’s loadapproaches capacity and the controller. When acloudevent occurs,the controller the ramp rate detects turn areswitches in connected viacommunications (hard-wired orradio) with appliances) incustomers’ premises areto powerviaswitches. connected The the grid.providingto power Anetworkofindividualcontrollable loads(typically informationtheir current on operatingthe control parametersto system, while control systemmay workinamini-grid. The solaranddieselgenerators feed The schematic above illustrates asimplifieddiagram load ofhowadirect Schematic: Possible configuration load controlof adirect system DIESEL GENERATOR SOLAR GENERATOR CONTROLLER LOAD SWITCHES CUSTOMER LOADS power and and power water corporation

Solar/Diesel Mini-Grid Handbook 51 CASE STUDY: DALY RIVER – PRELIMINARY ASSESSMENT OF LOAD MANAGEMENT POTENTIAL Due to increasing costs associated with remote essential service delivery, consideration of opportunities for efficiency gains and performance improvements via better load management is paramount. Therefore undertaking a load assessment is a critical component of solar/diesel hybrid system design. A preliminary investigation into the potential for load management to overcome the identified barriers to higher solar energy penetration in mini-grid systems and improve the overall efficiency of a solar/diesel hybrid power station has been undertaken, based on a case study of Daly River. The overarching objective of the preliminary investigation was to determine if load management (direct control and interruption) should be further pursued as way of optimising 52 the performance of a hybrid solar/diesel power station at Daly River. Presented below is a summary of the results and key findings. Please see Appendix 9.5 Load management – Daly River for further details. Study key findings and outcomes • Preliminary results indicate there may be potential for up to 200kW available to be utilised for direct load control at Daly River to increase solar penetration and overall efficiency in a hybrid mini-grid system. These findings suggest there is scope for future investigation into load management opportunities at Daly River. • Attempts to introduce load management must be done without negative impact to the price that customers pay for electricity or the quality and reliability of the electricity service provided.

7: Solar/Diesel Mini-Grids7: • Prior to the commencement of a load management trial a comprehensive communications program is required to educate and inform customers. This should include the proposed duration and frequency of switch-off periods and incentives to participate. • A generic load assessment model is a good starting point however considerable effort needs to be invested in customising the load management options to suit each specific community, in this case Daly River. • Customers were generally supportive of the use of solar power to reduce diesel fuel consumption. • Customers were generally interested in participating in a load management scheme, particularly if there was some incentive provided. • Key appliances identified as suitable for load control included: • airconditioning units • air-handling or ventilation systems • stand-alone fridges and freezers • cool rooms • electric water heaters • irrigation water pumps and pool pumps

3. 2. 1. types. distinct These are: investigation,tools werethe hybrid powersystemmodelling classifiedinto four werethat tools usedinternationally.hybrid systemmodelling Followingthis 2011, PVPS IEA Taskthe to gainanunderstandingof asurvey 11undertook systems,the complexityto involved due the designofsuchsystems. in In the development in ofhybrid mini-grid aspect Simulation isanimportant 7.3.6 4.

system over agiven period tools,simulation the the behaviourto simulate data of whichuseinput data (loadandclimate data andsystemcomponents) tools,dimensioning the basisofinput whichcalculate systemdimensionson distribution system. tools,design the mini-gridelectrical the designof with whichassist complete simulation ofdifferent systemsfor research purposes researchtools withahighdegree offlexibility and configurability toallow very kW (brown shadedarea). contributionto a450kW DalyRiver loadat loadcontrolthe useof by below illustratesthe potentialThe chart increase insolarpower 200 300 350 400 450 500 MODELLING TOOLS 250 100 150 50 0 WHICH WAS200kW NOTE: NOMINALLOADMANAGEMENTCAPACITYOF25%SURVEYEDPOTENTIAL Solar/Diesel HybridPowerSystem Daly River:450kWloadwithLoadManagement SOLAR ANDADDITIONALCAPACITY MADE AVAILABLETHROUGHDIRECT LOAD CONTROL(SHEDDABLELOAD) GEN 1(450kW)AND SPINNING RESERVE power and and power water corporation 53 Solar/Diesel Mini-Grid Handbook Due to the complexity involved in analysing hybrid mini-grid systems and the vast dimensions of mini-grid design and operation that can be analysed (as demonstrated by the distinct model types above), most software modelling tools are designed for a specific purpose, to investigate a specific aspect of hybrid systems and as such there are strengths and limitations associated with each. The modelling purpose will largely determine the most appropriate tool to use – RETScreen is good for general dimensioning and preliminary feasibility studies, HOMER for high level economic assessment, PVSyst for detailed technical configurations and Hybrid2 for system analysis. Other characteristics that influence the choice of modelling tool include cost (e.g. free, one-time purchase, annual license or maintenance fees), licencing policy (e.g. open-source, freeware, shareware, commercial), availability (downloadable, available by order, internal use only) and availability and quality of user interface and documentation.

54

HOMER is a steady-state time-step simulation program that incorporates system optimisation functionality. HOMER simulates the annual performance of multiple system configurations for a specified set of energy sources to find a configuration that satisfies the technical constraints at the lowest life-cycle cost. HOMER allows users to determine sensitivities, such as solar capacity to assist the optimization process. HOMER is available from homerenergy.com. 7: Solar/Diesel Mini-Grids7: • • • mini-grid operation data. ASIM canbeusedfor arange offunctions, including: improvethe accuracythe results. of ASIM hasbeenvalidated PWC usingactual the control system, modify their particular to simulate algorithms whichwill aslowerrateat for analysis. SinceASIMto isopensource users willbeable time stephoweversystems onaonesecond iscapableofgenerating it statistics analyse andinterpretthe data withinaspreadsheet. ASIM modelshybrid afastthen simulationto conduct runand the user system model)enable ASIM componentstwo distinct (ExcelThe spreadsheetsthe C#power and • • • • • • • • tools include: The key from attributes currently distinguishit that ofASIM available model also available. ASIM Reference Manual, ManualandConfiguration QuickStart Guideare website (www.powerwater.com.au). documentation Supporting including support).ASIM (withARENA ASIM isavailablethe PWCto downloadvia To address agapinavailabletools, modelling PWC recently developed ASIM spinning Reserve/PV set-point optimisation whole oflife financialanalysis PV/diesel hybrid systems management/investment planning asset (e.g. station blackouts)transient andother the onesecond behaviour level. at conducts onesecond modelling;therefore systemstabilityissues willdetect flexible; economic parameters (suchasdieselfuelprice)canbeescalated to haveintended autilityviewofcosts to bemodifiedwithnew controlable methods interpreted one, whicheffectsthe model the speedof based onacompiled andconcurrent/parallel implementation ratherthan an typical performance willbeoneyear onesecond at in<5minutes time-stepped the modelisvariable speednot the results operationactual the systembeingsimulated, of improvingthe accuracy of system characteristics (suchasgenerator scheduling),the to bettermatch their specificpower to simulate it to modify userscanchoose that means the controlthe GPL the modelisopensource under of aspect V3. This power and and power water corporation 55 Solar/Diesel Mini-Grid Handbook 56 7: Solar/Diesel Mini-Grids7: ASIM AND HOMER: COMPLEMENTARY HYBRID MODELLING TOOLS FOR SOLAR/DIESEL FEASIBILITY ASSESSMENTS ASIM and HOMER are complementary hybrid system analysis tools and PWC utilises both to conduct solar/diesel feasibility assessments and design comparisons. HOMER is a useful tool to undertake multiple optimisation and sensitivity analysis under a single simulation and determine the optimal system configuration and initial economic results given a set of high-level constraints (number and capacity of generators, solar system capacity etc). The HOMER-recommended configuration can then be modelled in ASIM, incorporating more specific input data (diesel fuel price escalation, generator call-up sequencing, load growth projections etc), to refine the cost estimate provided by HOMER and to assess how the system would work in detail (based on a one second analysis). the useof TMA. ASIM for visualisation.the ASIM framework require that itselfdoesnot Note isanopensource (GPL project it that V3) andhenceissuitablefor usewithin Analyst, MATLAB andOSIsoft PIProcess Book. TMA differsthe above from in Other available Processtools fortime seriesvisualisation includeCitect quality plotssuitablefor systemanalysis. overthe year output anddisplay the actual it)andcangenerate reasonable calculations overtime (e.g. the difference calculate and the setpoint between used inASIM. TMA isalsocapableofstatistics including andanalysisfunctions valuableparticularly for larger data setsofirregularlytime values sampled as time seriesdata.manipulation (suchasscalingor smoothing)of This is TMAto allowvisualisation inorderthe ASIM project and isusedwithin TMA –timeseriesvisualisation,analysisandreporting power and and power water corporation 57 Solar/Diesel Mini-Grid Handbook 7.3.7 OTHER FACTORS

VAr Sharing

When solar is added to a diesel mini-grid it is important to consider VAr sharing. A solar generator at unity will in effect reduce the diesel generator power factor. This occurs because the VArs continue to be supplied by the diesel generator while the diesel share of kW decreases. The net effect is a power factor reduction. Generally speaking, can operate with poor (<0.8) power factors as long as they are lagging and assuming that the generators are not fully loaded. Of greater concern is a leading power factor. Alternator voltage regulators (AVRs) cannot regulate voltage with anything but a very small leading power factor. Refer to the figure below for typical AVR stability regions.

Typical operating region of a generator 58 P

Leading kVAr limit characteristic kW

0.9 0.9 0.85 0.8 0.85 0.8

t Stator current limit i

m i l

y t i l i b a t Rotor current limit s l Operating a ic 7: Solar/Diesel Mini-Grids7: t region c ra P prime mover Active power limit power Active of Q

kVar leading (under-excited) kVar lagging (over-excited) all stages. The benefitedfromTKLN project constructive used stylesofengagement at to findamutuallyacceptablesolution.approach ensures work allparties challengesarise,When project they doininnovative as projects, acollaborative a common visionforthe project’s success. TKLN project, collaborationthe project’s throughout goodwilland delivery built approach isaneffective way uncertainties.to hedgeagainst the Aswitnessedin projects information wheretechnology imperfect In high exists, acollaborative Collaboration to contributedynamically allowinginvertersto VAr sharing. In future, more vendors willofferto controlthe ability solarinverter powerfactor power factor isrecommended. cause stabilityissues.then aunitysolarinverterthis riskcanbenegated Unless penetration,the greater afixedthat inverter lagging the risk power will factor forcethe generator to leadandriskstability. powerfactor The greaterthe solar the loadpowerfactor approached unity,then afixed inverter power factor could to anominalvaluefactor suchas0.9 lagging. This shouldbedonewithcare. If providednot bymany vendors. theinverter power to fix maytempting It be however PWC’sthis level that experience ofsolarinverter hasbeen control is the solargeneratorIdeally the dieselgenerator and share VArs proportionally power and and power water corporation 59 Solar/Diesel Mini-Grid Handbook 60 8: Conclusion

8 CONCLUSION hybrid systems. Australia andinternationally,to more leading widespread applications ofsolar/diesel and foster aknowledgesharing culturethe solar/diesel within in mini-gridindustry the Handbookwillbedeveloped,of byPWC and/or others, develop,to further strengthen maintaining areliable, utility-grade service. electricity isanticipated futurethat It editions with implementing solarintoto achieve anexisting dieselmini-grid fuelsavings while the remote communitypublic about powersupplycontextthe challengesassociated and to informThe Handbookisintendedthe broader solarindustry, the general academiaand the existing solar/dieselof hybrid systems. experience andknowledgePWCthrough development, hasgained designandoperation the improvingThis hasbeenmadepossibleby solareconomics inrecent the years and power generation portfolio,the hybridisationthroughthe entire of dieselmini-gridfleet. remains relatively small. To addressthis, the remote in PWC ispursuingastep-change in aremote NTcommunity mini-grid,total solarcontribution these mini-grids the in Despite beingover solar/dieselthe first 20years since hybrid system was implemented power and and power water corporation

Solar/Diesel Mini-Grid Handbook 61 9 APPENDIX

62 9: Appendix 9.1 Wadeye P or t Nama western australia K ea ts Cr Mistak Energy SourceEnergy Map2012 REMOTE INDIGENOUS COMMUNITIES SERVICED BY PWC Amanbidji Kildurk Pirlangimpi eek In Gar Docker Riv Kaltukatjara v Kin Walangkura er den P Gudabijin e w tor Wudapuli Daguragu W Bathurst Island a Bulla oin P Nganmaryanga y e a alumpa W er Peppimenarti ttie Cr T Nyirripi t anami aite Cr T Wurrumiyanga imber Cr Nauiyu Daly Riv Ba eek Delisa Belyuen eek Bunbidee tchelor P Adelaide igeon Hole Melville Island Yarralin er Milikapiti Riv ville eek Amunturangu Snak Lajamanu Hook Kings C er Kybrook Farm Moun C e Ba darwin ooper Y Downs V Yuendumu er Cr ular ic W Kalkarindji y Acacia Gap Acacia Larrakia toria Riv t Liebig a an eek field Cr v Rockhole a e Hill y on K a Springs eek therine Cur er Mulga P Papunya Haasts Bluff Ikuntji Binjari P tin

T

r Hermannsbu ine Cr op Springs Areyonga

ark Ntaria

Gorge Camp

u so eek Imanpa Barunga Daly Moun Yuelamu Larrimah T

Cr Minjilang g Willowra R Iwupataka i-

enner Springs

a th T ok Jabiru W r t Nturiya ee Sta Allen E Manyalluk er Island Napperby Laramba a v Ja a ters Maningrida V y Cr Oenpelli Gunbalanya Ma T alle Beswick W Uranda tion

ennan

s u Mungkarta allace R eek McLar tar y Thr Duck Cr Jilkminggan Dunmarr Yathalamarra K Goulburn Island Warruwi

ank tralia ulger T Newcastle ee T Pmara Jutunta t i- en Cr Weemol katherine i- Cr ockhole T T a W r

r Rittarangu Elliott region ee e eek eek a a eek Stirling Wilora /Six Mile ys alice springs

a

r U Amoonguna Neutr Tara

Milingimbi apunga Maryv Titjikala W Ramingining a Ali-Curung Warrabri ters al Junc An Santa Teresa Numbulwar Alc Engawala ale Hodgson Downs thon Gulin Bulman R Miniyeri oota

oper Riv

Apatula F

tion

k in Arlparra Murr Imangara R Milyakburra y Lagoon

ose Riv e Ngangalala Borroloola Galiwink'u er a Elcho Island Amar Ampilatwatja y Downs Har Atitjere Gapuwiyak er Bick ts R Lak oo Wandangula er southern ange e E Epenera Wutunugurra ton Angurugu region v Mungoobada ella McAr C Orwaitilla anteen Cr R obinson Riv thur Riv Alyangula eek Ski Beach/ Gunyangara E Gr er er ylandt Alpurrurulam oote Nhulunbuy Umbakumba power and and power water corporation T Avon Downs obermor Yirrkala W Marngarr Lak ollogor e Nash e y ang

queensland IES COMMUNITIES DISTILLATE MAJOR TOWNS PWC POWERNETWORK GAS PIPELINES PWC GRID GRID/SOLAR DISTILLATE/SOLAR IES GRID PRIVATE GRID 63 Solar/Diesel Mini-Grid Handbook 9.2 UTILITY SCALE SOLAR/DIESEL MINI-GRIDS IN AUSTRALIA Presented below is a brief list of operational utility-scale solar/diesel mini-grids in Australia. Note that some of these systems are owned by a third party, not the utility.

Solar System Utility Location Capacity (kWp) Technology Ergon Energy Doomadgee, 264 Flat plate, Queensland fixed array Ergon Energy Windorah, 130 Concentrating Queensland PV dishes, dual axis tracking Horizon Power Nullagine, 200 Flat plate, single- 64 Western Australia axis tracking Horizon Power Marble Bar, 300 Flat plate, single- Western Australia axis tracking Hydro Tasmania King Island, 100* Flat plate, Tasmania fixed array Power and Water Bulman, 56 Flat plate, Corporation Northern Territory fixed array Power and Water Kalkarindji, 402 Flat plate, 9: Appendix Corporation Northern Territory fixed array Power and Water Kings Canyon, 225 Flat plate, Corporation Northern Territory fixed array Power and Water Lajamanu, 290 Concentrating Corporation Northern Territory PV dishes Power and Water Lake Nash 266* Flat plate, Corporation (Alpurrurulam), fixed array Northern Territory Power and Water Ntaria 192 Concentrating Corporation (Hermannsburg), PV dishes, dual Northern Territory axis tracking Power and Water Ti Tree, 324 Flat plate, Corporation Northern Territory fixed array Power and Water Yuendumu, 240 Concentrating Corporation Northern Territory PV dishes, dual axis tracking

* These hybrid mini-grid systems also incorporate 9.3 1000 1000 1000 1000 100 200 300 400 500 600 700 800 900 100 200 300 400 500 600 700 800 900 100 200 300 400 500 600 700 800 900 100 200 300 400 500 600 700 800 900 0 0 0 0 • Date 15 July2013 Insolation analysis–highvariability –scattered cloud cover day – guaranteedthe day. across combined insolation however indicates abaselinesolargeneration couldthat be troughs different at the daytimes of for eachsite. The graphthe showing scattered cloudcover. Clearlyshownarethe variable insolation peaks and the stationsthe insolationThe following onaday sixof at graphs of chart greater availability ofbaseline solargeneration. distributing solargenerationturn guaranteesthis in the gridand around a the effects that ofintermittency aresuggest greatly reduced byphysically threePreliminary months thefirst findingsfrom ofinsolation data gathered demonstration facility. 15km radius, KnowledgeAustralia centredthe Desert SolarCentre on (DKASC) grid.of anelectricity The weather stations weretwo ringsof5kmand located in variations ininstantaneous weather effectsthe geographical across boundaries withresearchcommissionedto assist around AliceSprings analysing aimedat in instantaneous weather effects), nineweather stations were recently research supported (Analysisofvariations project ofanARENA As part INVESTIGATION DISTRIBUTED GENERATION –ALICESPRINGS Nth StuartHwy TIMESTAMP Ross Hwy TIMESTAMP Ilparpa Rd TIMESTAMP Stephens Rd TIMESTAMP Solar insolation across individualsitesinAliceSpringsRegion 15/07/2013 7:49 15/07/2013 7:49 15/07/2013 7:49 15/07/2013 7:49 15/07/2013 8:09 15/07/2013 8:09 15/07/2013 8:09 15/07/2013 8:09 15/07/2013 8:29 15/07/2013 8:29 15/07/2013 8:29 15/07/2013 8:29 15/07/2013 8:48 15/07/2013 8:48 15/07/2013 8:48 15/07/2013 8:48 15/07/2013 9:08 15/07/2013 9:08 15/07/2013 9:08 15/07/2013 9:08 15/07/2013 9:28 15/07/2013 9:28 15/07/2013 9:28 15/07/2013 9:28 15/07/2013 9:48 15/07/2013 9:48 15/07/2013 9:48 15/07/2013 9:48 15/07/2013 10:07 15/07/2013 10:07 15/07/2013 10:07 15/07/2013 10:07 15/07/2013 10:27 15/07/2013 10:27 15/07/2013 10:27 15/07/2013 10:27 15/07/2013 10:47 15/07/2013 10:47 15/07/2013 10:47 15/07/2013 10:47 15/07/2013 11:07 15/07/2013 11:07 15/07/2013 11:07 15/07/2013 11:07 15/07/2013 11:26 15/07/2013 11:26 15/07/2013 11:26 15/07/2013 11:26 15/07/2013 11:46 15/07/2013 11:46 15/07/2013 11:46 15/07/2013 11:46 15/07/2013 12:06 15/07/2013 12:06 15/07/2013 12:06 15/07/2013 12:06 15/07/2013 12:26 15/07/2013 12:26 15/07/2013 12:26 15/07/2013 12:26 15/07/2013 12:45 15/07/2013 12:45 15/07/2013 12:45 15/07/2013 12:45 15/07/2013 13:05 15/07/2013 13:05 15/07/2013 13:05 15/07/2013 13:05 15/07/2013 13:25 15/07/2013 13:25 15/07/2013 13:25 15/07/2013 13:25 15/07/2013 13:45 15/07/2013 13:45 15/07/2013 13:45 15/07/2013 13:45 15/07/2013 14:04 15/07/2013 14:04 15/07/2013 14:04 15/07/2013 14:04 15/07/2013 14:24 15/07/2013 14:24 15/07/2013 14:24 15/07/2013 14:24 15/07/2013 14:44 15/07/2013 14:44 15/07/2013 14:44 15/07/2013 14:44 15/07/2013 15:04 15/07/2013 15:04 15/07/2013 15:04 15/07/2013 15:04 15/07/2013 15:23 15/07/2013 15:23 15/07/2013 15:23 15/07/2013 15:23 15/07/2013 15:43 15/07/2013 15:43 15/07/2013 15:43 15/07/2013 15:43 15/07/2013 16:03 15/07/2013 16:03 15/07/2013 16:03 15/07/2013 16:03 15/07/2013 16:23 15/07/2013 16:23 15/07/2013 16:23 15/07/2013 16:23 15/07/2013 16:42 15/07/2013 16:42 15/07/2013 16:42 15/07/2013 16:42 15/07/2013 17:02 15/07/2013 17:02 and power water corporation 15/07/2013 17:02 15/07/2013 17:02 15/07/2013 17:22 15/07/2013 17:22 15/07/2013 17:22 15/07/2013 17:22 15/07/2013 17:42 15/07/2013 17:42 15/07/2013 17:42 15/07/2013 17:42 65 Solar/Diesel Mini-Grid Handbook Nth Stuart Hwy 1000 900 800 700 600 500 400 300 200 100 0 TIMESTAMP 15/07/2013 9:28 15/07/2013 7:49 15/07/2013 8:09 15/07/2013 8:29 15/07/2013 8:48 15/07/2013 9:08 15/07/2013 9:48 15/07/2013 10:07 15/07/2013 10:27 15/07/2013 10:47 15/07/2013 11:07 15/07/2013 11:26 15/07/2013 11:46 15/07/2013 12:06 15/07/2013 12:26 15/07/2013 12:45 15/07/2013 13:05 15/07/2013 13:25 15/07/2013 13:45 15/07/2013 14:04 15/07/2013 14:24 15/07/2013 14:44 15/07/2013 15:04 15/07/2013 15:23 15/07/2013 15:43 15/07/2013 16:03 15/07/2013 16:23 15/07/2013 16:42 15/07/2013 17:02 15/07/2013 17:22 15/07/2013 17:42

Stephens Rd 1000 900 800 700 600 500 400 300 200 100 0 TIMESTAMP 15/07/2013 7:49 15/07/2013 8:09 15/07/2013 8:29 15/07/2013 8:48 15/07/2013 9:08 15/07/2013 9:48 15/07/2013 9:28 15/07/2013 10:07 15/07/2013 10:27 15/07/2013 10:47 15/07/2013 11:07 15/07/2013 11:26 15/07/2013 11:46 15/07/2013 12:06 15/07/2013 12:26 15/07/2013 12:45 15/07/2013 13:05 15/07/2013 13:25 15/07/2013 13:45 15/07/2013 14:04 15/07/2013 14:24 15/07/2013 14:44 15/07/2013 15:04 15/07/2013 15:23 15/07/2013 15:43 15/07/2013 16:03 15/07/2013 16:23 15/07/2013 16:42 15/07/2013 17:02 15/07/2013 17:22 15/07/2013 17:42

Ilparpa Rd 1000 900 800 700 600 500 400 300 200 100 0 TIMESTAMP 15/07/2013 7:49 15/07/2013 8:09 15/07/2013 8:29 15/07/2013 8:48 15/07/2013 9:08 15/07/2013 9:48 66 15/07/2013 9:28 15/07/2013 10:07 15/07/2013 10:27 15/07/2013 10:47 15/07/2013 11:07 15/07/2013 11:26 15/07/2013 11:46 15/07/2013 12:06 15/07/2013 12:26 15/07/2013 12:45 15/07/2013 13:05 15/07/2013 13:25 15/07/2013 13:45 15/07/2013 14:04 15/07/2013 14:24 15/07/2013 14:44 15/07/2013 15:04 15/07/2013 15:23 15/07/2013 15:43 15/07/2013 16:03 15/07/2013 16:23 15/07/2013 16:42 15/07/2013 17:02 15/07/2013 17:22 15/07/2013 17:42

Ross Hwy 1000 Ross Hwy 1000900 900800 800700 700600 9: Appendix 600500 500400 400300 300200 200100 1000 0 TIMESTAMP TIMESTAMP 15/07/2013 7:49 15/07/2013 8:09 15/07/2013 8:29 15/07/2013 8:48 15/07/2013 9:08 15/07/2013 9:48 15/07/2013 9:28 15/07/2013 10:07 15/07/2013 10:27 15/07/2013 10:47 15/07/2013 11:07 15/07/2013 11:26 15/07/2013 11:46 15/07/2013 12:06 15/07/2013 12:26 15/07/2013 12:45 15/07/2013 13:05 15/07/2013 13:25 15/07/2013 13:45 15/07/2013 14:04 15/07/2013 14:24 15/07/2013 14:44 15/07/2013 15:04 15/07/2013 15:23 15/07/2013 15:43 15/07/2013 16:03 15/07/2013 16:23 15/07/2013 16:42 15/07/2013 17:02 15/07/2013 17:22 15/07/2013 17:42 15/07/2013 9:28 15/07/2013 7:49 15/07/2013 8:09 15/07/2013 8:29 15/07/2013 8:48 15/07/2013 9:08 15/07/2013 9:48 15/07/2013 10:07 15/07/2013 10:27 15/07/2013 10:47 15/07/2013 11:07 15/07/2013 11:26 15/07/2013 11:46 15/07/2013 12:06 15/07/2013 12:26 15/07/2013 12:45 15/07/2013 13:05 15/07/2013 13:25 15/07/2013 13:45 15/07/2013 14:04 15/07/2013 14:24 15/07/2013 14:44 15/07/2013 15:04 15/07/2013 15:23 15/07/2013 15:43 15/07/2013 16:03 15/07/2013 16:23 15/07/2013 16:42 15/07/2013 17:02 15/07/2013 17:22 15/07/2013 17:42

Deepwell Rd 1000 900 800 700 600 500 400 300 200 100 0 TIMESTAMP 15/07/2013 7:49 15/07/2013 8:09 15/07/2013 8:29 15/07/2013 8:48 15/07/2013 9:08 15/07/2013 9:48 15/07/2013 9:28 15/07/2013 10:07 15/07/2013 10:27 15/07/2013 10:47 15/07/2013 11:07 15/07/2013 11:26 15/07/2013 11:46 15/07/2013 12:06 15/07/2013 12:26 15/07/2013 12:45 15/07/2013 13:05 15/07/2013 13:25 15/07/2013 13:45 15/07/2013 14:04 15/07/2013 14:24 15/07/2013 14:44 15/07/2013 15:04 15/07/2013 15:23 15/07/2013 15:43 15/07/2013 16:03 15/07/2013 16:23 15/07/2013 16:42 15/07/2013 17:02 15/07/2013 17:22 15/07/2013 17:42

Brewer Rd 1000 900 800 700 600 500 400 300 200 100 0 TIMESTAMP 15/07/2013 7:49 15/07/2013 8:09 15/07/2013 8:29 15/07/2013 8:48 15/07/2013 9:08 15/07/2013 9:48 15/07/2013 9:28 15/07/2013 10:07 15/07/2013 10:27 15/07/2013 10:47 15/07/2013 11:07 15/07/2013 11:26 15/07/2013 11:46 15/07/2013 12:06 15/07/2013 12:26 15/07/2013 12:45 15/07/2013 13:05 15/07/2013 13:25 15/07/2013 13:45 15/07/2013 14:04 15/07/2013 14:24 15/07/2013 14:44 15/07/2013 15:04 15/07/2013 15:23 15/07/2013 15:43 15/07/2013 16:03 15/07/2013 16:23 15/07/2013 16:42 15/07/2013 17:02 15/07/2013 17:22 15/07/2013 17:42

Sum global insolation of 7 sites with half hourly minimums 6000

5000

4000

3000

2000

1000

0 15/07/2013 7:30 15/07/2013 7:47 15/07/2013 8:04 15/07/2013 8:21 15/07/2013 8:38 15/07/2013 8:55 15/07/2013 9:12 15/07/2013 9:29 15/07/2013 9:46 15/07/2013 17:27 15/07/2013 17:45 15/07/2013 10:03 15/07/2013 10:20 15/07/2013 10:37 15/07/2013 10:55 15/07/2013 11:12 15/07/2013 11:29 15/07/2013 11:46 15/07/2013 12:03 15/07/2013 12:20 15/07/2013 12:37 15/07/2013 12:54 15/07/2013 13:11 15/07/2013 13:28 15/07/2013 13:45 15/07/2013 14:02 15/07/2013 14:20 15/07/2013 14:37 15/07/2013 14:54 15/07/2013 15:11 15/07/2013 15:28 15/07/2013 15:45 15/07/2013 16:02 15/07/2013 16:19 15/07/2013 16:36 15/07/2013 16:53 15/07/2013 17:10

SUM OF SUM TOTAL RADIATION (W/M2) SUM OF MIN HALF HOURLY RADIATION (W/M2) 1000 2000 3000 4000 1000 5000 2000 6000 3000 4000 5000 6000 1000 1000 1000 1000 1000 1000 100 200 300 400 500 600 100 700 200 800 300 900 400 500 600 700 800 900 100 200 300 400 500 600 100 700 200 800 300 900 400 500 600 700 800 900 100 200 300 400 500 600 100 700 200 800 300 900 400 500 600 700 800 900 • 0 0 0 0 0 0 0 0 Alice SpringsRegion. Combined solarinsolation across geographically dispersedsitesin Brewer Rd Deepwell Rd Deepwell Rd Ross Hwy Ross Hwy 15/07/2013 7:3015/07/2013 7:30 Sum globalinsolationof7siteswithhalfhourlyminimums Sum globalinsolationof7siteswithhalfhourlyminimums TIMESTAMP TIMESTAMP Brewer Rd TIMESTAMP TIMESTAMP TIMESTAMP TIMESTAMP 15/07/2013 7:4715/07/2013 7:47 15/07/2013 7:4915/07/2013 7:49 15/07/2013 7:4915/07/2013 7:49 15/07/2013 7:4915/07/2013 7:49 15/07/2013 8:0415/07/2013 8:04 SUM OFTOTALRADIATION(W/M 15/07/2013SUM OFTOTALRADIATION(W/M 8:2115/07/2013 8:21 15/07/2013 8:0915/07/2013 8:09 15/07/2013 8:0915/07/2013 8:09 15/07/2013 8:0915/07/2013 8:09 15/07/2013 8:3815/07/2013 8:38 15/07/2013 8:2915/07/2013 8:29 15/07/2013 8:2915/07/2013 8:29 15/07/2013 8:2915/07/2013 8:29 15/07/2013 8:5515/07/2013 8:55 15/07/2013 8:4815/07/2013 8:48 15/07/2013 8:4815/07/2013 8:48 15/07/2013 8:4815/07/2013 8:48 15/07/2013 9:1215/07/2013 9:12 15/07/2013 9:0815/07/2013 9:08 15/07/2013 9:0815/07/2013 9:08 15/07/2013 9:0815/07/2013 9:08 15/07/2013 9:2915/07/2013 9:29 15/07/2013 9:2815/07/2013 9:28 15/07/2013 9:2815/07/2013 9:28 15/07/2013 9:2815/07/2013 9:28 15/07/2013 9:4615/07/2013 9:46 15/07/2013 9:4815/07/2013 9:48 15/07/2013 9:4815/07/2013 9:48 15/07/2013 9:4815/07/2013 9:48 15/07/2013 10:0315/07/2013 10:03 15/07/2013 10:0715/07/2013 10:07 15/07/2013 10:0715/07/2013 10:07 15/07/2013 10:0715/07/2013 10:07 15/07/2013 10:2015/07/2013 10:20 15/07/2013 10:3715/07/2013 10:37 15/07/2013 10:2715/07/2013 10:27 15/07/2013 10:2715/07/2013 10:27 15/07/2013 10:2715/07/2013 10:27 15/07/2013 10:5515/07/2013 10:55 15/07/2013 10:4715/07/2013 10:47 15/07/2013 10:4715/07/2013 10:47 15/07/2013 10:4715/07/2013 10:47 15/07/2013 11:1215/07/2013 11:12 15/07/2013 11:0715/07/2013 11:07 15/07/2013 11:0715/07/2013 11:07 15/07/2013 11:0715/07/2013 11:07 15/07/2013 11:2915/07/2013 11:29 15/07/2013 11:2615/07/2013 11:26 15/07/2013 11:2615/07/2013 11:26 15/07/2013 11:2615/07/2013 11:26 15/07/2013 11:4615/07/2013 11:46 15/07/2013 11:4615/07/2013 11:46 15/07/2013 11:4615/07/2013 11:46 15/07/2013 11:4615/07/2013 11:46

2 15/07/20132 12:0315/07/2013 12:03

) ) 15/07/2013 12:0615/07/2013 12:06 15/07/2013 12:0615/07/2013 12:06 15/07/2013 12:0615/07/2013 12:06 15/07/2013 12:2015/07/2013 12:20 15/07/2013 12:2615/07/2013 12:26 15/07/2013 12:2615/07/2013 12:26 15/07/2013 12:2615/07/2013 12:26 15/07/2013 12:3715/07/2013 12:37 15/07/2013 12:4515/07/2013 12:45 15/07/2013 12:4515/07/2013 12:45 15/07/2013 12:4515/07/2013 12:45 SUM OFMINHALFHOURLYRADIATION(W/M 15/07/2013SUM OFMINHALFHOURLYRADIATION(W/M 12:5415/07/2013 12:54 15/07/2013 13:1115/07/2013 13:11 15/07/2013 13:0515/07/2013 13:05 15/07/2013 13:0515/07/2013 13:05 15/07/2013 13:0515/07/2013 13:05 15/07/2013 13:2815/07/2013 13:28 15/07/2013 13:2515/07/2013 13:25 15/07/2013 13:2515/07/2013 13:25 15/07/2013 13:2515/07/2013 13:25 15/07/2013 13:4515/07/2013 13:45 15/07/2013 13:4515/07/2013 13:45 15/07/2013 13:4515/07/2013 13:45 15/07/2013 13:4515/07/2013 13:45 15/07/2013 14:0215/07/2013 14:02 15/07/2013 14:0415/07/2013 14:04 15/07/2013 14:0415/07/2013 14:04 15/07/2013 14:0415/07/2013 14:04 15/07/2013 14:2015/07/2013 14:20 15/07/2013 14:2415/07/2013 14:24 15/07/2013 14:2415/07/2013 14:24 15/07/2013 14:2415/07/2013 14:24 15/07/2013 14:3715/07/2013 14:37 15/07/2013 14:4415/07/2013 14:44 15/07/2013 14:4415/07/2013 14:44 15/07/2013 14:4415/07/2013 14:44 15/07/2013 14:5415/07/2013 14:54 15/07/2013 15:1115/07/2013 15:11 15/07/2013 15:0415/07/2013 15:04 15/07/2013 15:0415/07/2013 15:04 15/07/2013 15:0415/07/2013 15:04 15/07/2013 15:2815/07/2013 15:28 15/07/2013 15:2315/07/2013 15:23 15/07/2013 15:2315/07/2013 15:23 15/07/2013 15:2315/07/2013 15:23 15/07/2013 15:4515/07/2013 15:45 15/07/2013 15:4315/07/2013 15:43 15/07/2013 15:4315/07/2013 15:43 15/07/2013 15:4315/07/2013 15:43 15/07/2013 16:0215/07/2013 16:02 15/07/2013 16:0315/07/2013 16:03 15/07/2013 16:0315/07/2013 16:03 15/07/2013 16:0315/07/2013 16:03 15/07/2013 16:1915/07/2013 16:19 15/07/2013 16:2315/07/2013 16:23 15/07/2013 16:2315/07/2013 16:23 15/07/2013 16:2315/07/2013 16:23 15/07/2013 16:3615/07/2013 16:36 15/07/2013 16:4215/07/2013 16:42 15/07/2013 16:4215/07/2013 16:42 15/07/2013 16:4215/07/2013 16:42 power and and power water corporation 15/07/2013 16:5315/07/2013 16:53 15/07/2013 17:0215/07/2013 17:02 15/07/2013 17:0215/07/2013 17:02 15/07/2013 17:0215/07/2013 17:02 15/07/2013 17:1015/07/2013 17:10 15/07/2013 17:2215/07/2013 17:22 15/07/2013 17:2215/07/2013 17:22 15/07/2013 17:2215/07/2013 17:22 2 2 ) ) 15/07/2013 17:4215/07/2013 17:42 15/07/2013 17:4215/07/2013 17:42 15/07/2013 17:4215/07/2013 17:42 15/07/2013 17:2715/07/2013 17:27 15/07/2013 17:4515/07/2013 17:45 67 Solar/Diesel Mini-Grid Handbook 9.4 ENERGY STORAGE TECHNOLOGIES Technologies used for ESS can be classified as electrochemical, electrothermal, electromechanical, and electromagnetic; and they can be rated by energy capacity and power capacity. The main technologies currently utilised are outlined below. While it is a rapidly changing field, this information provides a good starting point for investigations. A multitude of electrochemical ESS are available, with many more under development. Lead acid batteries (flooded or valve regulated) and Nickel-Cadmium batteries can be considered the most mature technologies. However, even within these there are significant differences in type of manufacture based on intended application. This can significantly impact energy and power capacities and thus the suitability for intended use. Other mature technologies are Lithium Ion and Lithium Polymer batteries, 68 which can offer high energy and power densities at high energy density. However, their use in stationary applications is currently not attractive due to their high cost. Furthermore, several large-scale sodium-sulphite (NaS) battery installations exist. Many new battery manufacturers are pushing into the market. Closest to maturity are several types of ‘advanced lead acid’ batteries which promise extended cycle life, higher energy density and increased power levels. Also potentially close to maturity are several types of flow battery. Various chemistries have been developed for this concept. It is hard to say which of 9: Appendix these currently is the most likely to succeed. from whichsteamisgeneratedturbines.to drive available for large scalesystemswhere isused asastorage moltensalt medium isonly to electricity Electrothermal storage back to return energy designed input the latentcooling offusionrequired heat loadis ice. to melt times more 80 volumeabout efficient, a themain tomeet contribution as electrothermal cooling systemsusechilledwater orice.this context In iceis Electrothermal heaters employ bricks orwater storagethe energy as medium; useinheatingdirect orcooling applications,to drive industrialprocesses. or Electrothermal systemseitherstoreto bereleased orcold heat later eitherfor requirementsenergy or anotherform byelectricity ofenergy. usuallymet for anelectricity-storage-electricityapplication, ratherthey makethermal useof Unlikethe otherESSdescribedabove, mostelectrothermal are ESS designed not they are onlyutilisedinpowerqualityapplications. application isgenerallyto very smallamounts limited storedthus ofenergy and storage (SMES), rely onhighlyspecialised andcostly materials.their this to Due of electromagnetic ESS, supercapacitors andsuperconducting magneticenergy Electromagnetic ESSare generally highlyefficient, very but expensive. types Both ESS options. Thus,these systemsrely onlocalorregional geographical features. reservoir volume have sizeto beofsignificant toprovidefor suchsystems viable two waterbetween reservoirs different at elevations. Elevation difference and Pumped hydro-electric poweroperatesthe potential difference energy on date. However, generallythan several systemssmaller MW are considered. not Pumped Hydro effective cost ESSarethe most large scalesystemsavailableto commercial operation. smaller above-ground CAES systemshave beenproposed. However, noneare in power plants andhenceareto 1000sofMW.the order of100s in Recently 1979, and1991respectively. The systemsare usedfor loadshifting ofnuclear mines.two suchsystemshave At beenincontinuous least operation since CAES systemsusuallymakethe underground useof caverns ofabandoned technologies. are stilldealingwith ‘teething problems’to advanced due bearingandmotor lifethe shorter cycle ofacheaperESS. Inaddition, many composite flywheels ismoreto determineifit to operate economical aflywheel ESS, toaccept or flywheels issignificantly higher. Thus, acaseby comparisonis required to electrochemical ESSinpowerquality applications. However, forthe cost long cycle life, fast response andhighpowerlevels, flywheelsare superior demonstrated andimplemented inpowerqualityapplications.their to Due and composite rotor, highRPM flywheels. technologies have Both been Flywheels canbecategorisedtraditional into steelrotor, lowRPM flywheels are more suitablefor storage. long-termenergy short-term storage powerqualityapplications, whileCAES andpumpedhydro storage (CAES) andpumpedhydro power. Flywheelsare generally employed in threeThe majorelectromechanicalare ESS flywheels, compressed airenergy than 100000hours. less cell isgenerally measured not incycles,to besignificantly canbeexpected but electrolysers are rather inefficient (<20–50percent). The lifeexpected ofafuel to generatethe fuelcell then consumedelectrolysis in andis power, however, investment, highlossrates. exhibit but Hydrogen gascanbegenerated by these systemsishydrogencomponent of tanks, whichare cheapininitial Special casesofelectrochemical storage are hydrogen fuelcells. The storage technical andeconomic viabilityisachieved. research lab, orwherethey have, needconsiderable more development before technologies areOther underdevelopment, however somehavethe left not power and and power water corporation 69 Solar/Diesel Mini-Grid Handbook 9.5 LOAD MANAGEMENT – DALY RIVER PRELIMINARY INVESTIGATION As mentioned in Section 7.3.5 Load control, the use of load management can introduce operating/operational efficiencies into a hybrid power system and allow for greater solar penetration. Following is an overview of the results of the Daly River preliminary load management investigation. The overarching objective of the preliminary investigation was to determine if load management (direct control and interruption) should be further pursued as way of optimising the performance of a hybrid solar/diesel power station at Daly River.

Study context

There are 145 electricity customers in Daly River and in 2011, the total metered consumption was approximately 2 510MWh. The combined annual consumption 70 of the top 19 commercial electricity customers, who represent 11.7 per cent of all electricity customers, was 1 395MWh, which equates to 55.6 per cent of the total electricity consumed in 2011. Out of the top 19 commercial electricity customers identified, 12 were involved in the preliminary investigation. These customers were a mix of government facilities, local council facilities and private commercial enterprises. The total consumption of these 12 facilities in 2011 was 1 104MWh, which represents 44 per cent of the total consumption. 9: Appendix 2011 ANNUAL CONSUMPTION (kWh) 200,000 250,000 100,000 150,000 50,000 0 used inafuturetrial. loadmanagement datato collect onspecific and consumer applianceswhich could potentially be the DalyRiveroperation powerstation appliances(via control ofselect system) the notionofPWC and ofloadmanagement the concept controlling about the the customers the viewsthe sitevisitswere of to understand objectives of Site visitswerethe premises conducted customers. at of12participating The and availability thesitevisit to confirm was themanagerorowner. made of time. visit the community Around visit, oneweekaheadof asecond phonecall planned sitevisit. The customerswere asked forto asite aninitialcommitment investigation theloadmanagement the specificobjectives of the with and contacted.this initialconversation In the overall was project described, along the sitevisits.in Where possible,the facilitythe managerorownerof was the researchinformthem of to beinvolved objectives anddeterminewillingness investigation werethe sitevisits, contactedto viaphoneprior to provideto the In December2012customersidentified in aspossible participants the research. in participate PWCthat objectives andnoting wouldbeinviting commercialto customers River community was provided factsheet, withaproject the project outlining the DalyRiver SolarResearchWhen was Project launchedinJuly2012,the Daly Study approach in yellow. customers inDalyRiver 50Largest electricity those surveyed (2011)with 1 6 11 16 21 CONSUMER 26 31 36 41 power and and power water corporation 46

Solar/Diesel Mini-Grid Handbook 71 During the site visits, high-power appliances at consumer premises were identified. Data was collected on the high-power appliances which may be able to be switched off for brief periods without impacting on the customers’ level of comfort or service. The rated power for the devices was noted from equipment labels, but where these were not visible or present, the load was estimated by the consultant based on similar equipment. Appliance usage patterns were also discussed with customers; including whether the appliance was in use all year or seasonally or for certain periods of the day. The consumer was also asked about their overall patterns of power use. During the site visit, customers were also asked survey questions to determine their willingness to participate in a potential load management trial. The survey included their views on solar power, load management and whether an incentive would be required to encourage them to participate in a future trial.

72 Customers were provided with energy and water efficiency information and PWC merchandise during the site visits. Following the visits and analysis of the survey and load management assessment results, follow-up letters and a factsheet were sent out to participants. The letter outlined some brief recommendations for energy efficiency improvements which were noted during the visit. The factsheet included preliminary findings from the initial investigation and next steps.

Daly River Load management – preliminary indications of potential by

9: Appendix customer-type.

Diversified load, available for Load Management (kW)

5%

GOVERNMENT / COUNCIL-OWNED PREMISES

44% 51% LEISURE FACILITIES OTHER PRIVATE BUSINESS 9.6 controller andloadcontrol unitsfor switchingandmetering. Utility level platforms:these includeusercontrol software, data handling controls for room air-conditioners. network.management They are targeted specifically at replacing remote of respondingto radio ofaload communication andinternet signalsaspart air-conditioningSmart-grid-enabled thermostats: thesedevices may becapable single circuit. device connects directlyto controlthe switchboard into allappliancesona Devices level circuit capableof controlthe loadswitching andmonitoring: and suitablefor appliance-level loadcontrol. capability. These are often remote-controllable vialocalradio communication 240V loadcontrol alsohavethat switches consumption energy measurement Residential devices management energy –appliance controllers: for example, software packages currently available: The followingtypes ofhardware isabriefoutlineofsome prominent and/or • • • the followingcomprise key elements: A complete systemfor loadcontrol networkwould inaloadmanagement should provide for point ausefulinitialstarting investigations. solar resource. While,the information belowmay quicklybesupersededit networkforloads inaloadmanagement the specific application ofoptimising currently availablethe marketplace, in whichwouldbecapableofcontrolling integration isanemerging field. The following isadescriptionofequipment, techniques for Applying loadmanagement optimising renewable energy LOAD MANAGEMENT – TECHNOLOGIES management networkappliances management andproducingthe load networked programedto loadsetc.) output premises, capableofreceiving datathe powerstation, (from input the hardware andsoftware networkoperator’sthe loadmanagement located at the hardwarethe operator’s at andconsumer’s premises. transmit (wiredto orwireless) communicationstechnology signalsbetween individual applianceoracomplete onandoff circuit hardwarethe consumer’s located at premises, capableofswitchingan TaskXVNetworkDrivenDSMLoadManagementDatabase.aspx. a detaileddatabase currently of available products: www.ieadsm.org/ For acomprehensive list,the International Agency Energy maintains power and and power water corporation

Solar/Diesel Mini-Grid Handbook 73 There are also various load management communication technologies. Each has advantages and disadvantages. To provide an optimal solution, often several technologies work in unison. The following is a short overview of some of these technologies: Ripple control is a very common form of load control that has been available for a long time. It is most commonly used to control off-peak hot water or space-heating systems. It works by superimposing a higher-frequency signal (usually between 100 and 1 600Hz) onto the standard 50Hz power supply. When the signal is received by devices connected to the controllable load, they switch off the load until the signal is disabled or another frequency signal is received. Traditionally, ripple control has been a one-way system, but more recently two-way systems are also being implemented where the consumer devices send information back to the utility, such as for billing purposes. Ripple control 74 has a high capital cost but relatively low operating and maintenance costs. A related technology is power-line carrier, which uses the power lines (conductors) as a means to establish a network, over which protocols such as TCP/IP or X10 can be used to communicate with devices, i.e. a Local Area Network (LAN) over power lines. This works more readily in a bi-directional fashion than ripple control. It is more commonly used within buildings than across distribution networks because of the absorption of the signal in transformers. Traditionally, telephone based systems use dial-up modems, where the central control device can connect to a remote load via modem. Various 9: Appendix communication protocols are possible over the modem link, to achieve different tasks. A more modern version of this uses mobile phone system based modems (GSM, 3G or 4G). These systems are effective when communications are only required sporadically, such as downloading data from a power meter once a month. Systems have a modest capital cost (provided the phone line or mobile phone system is already in place at the consumer end) however can have a high operating cost, especially if communication has to occur frequently or to many customers at the same time. As it is a one-to-one form of communication, it is less suitable for load control across a larger number of customers at the same time. There is also a substantial lead time in establishing communication to the end device (dialling, answering and responding). Traditionally this technology uses analogue signals, which limit the maximum throughput and reliability of the system. Another technology that uses the wired phone system in a more advanced way is that of ADSL, which is how the majority of households receive their internet connection. More modern installations can use an optic fibre link which has a higher possible throughput than ADSL which is over copper wire. The advantage of both of these types is they are an ‘always on’ system, so no ‘dial-up’ is needed when a communication is required. It is therefore also ideally suited as a communication channel for demand control. tools at acustomerlevel,tools at bothfor utility- andcustomer-initiated actions. ZigBee-based networks increasingly to useasdemandmanagement popular to becontrolled.the networkandishard-wiredthe device to to This makes switch ormeasurement communicatesthat devicethe ZigBee specification via systems. There are alsomany add-ondevices available asa essentiallythat act transceiver in, built suchasinrefrigerative airconditioners water andsomehot More andmore appliancesare nowmanufactured withaZigBee-compatible Bluetooth orWi-Fi. less expensivethan other Wireless Personal Area Networks (WPANs), suchas the ZigBee specification definedby tobesimplerand is technology intended thus conservethe radiostime and means power. can beoffthe muchof The Transmission andreception withinaZigBee networkare synchronised. This requiringthe networkwithout higherpowerlevels. the vicinity,to otherdevices in signal on the physicalthus extending range of hub orgateway, individualdownstreamthe asrouters andpass devices canact ratherthat to communicatemeans than allenddevicesto acentral needing (dependingthe building’s on inameshnetworkfashion. construction) but This transmission system.transmission Data canoccuroverto 150m distancesof15 The ZigBee specification isintended asalow-cost, low-power, low-data remote sites. The cheaperdevices are often discarded andreplacedthey fail. if especially whendevicestested onsite, haveto be requiringtravel staffto the to power level andcomplexitythe system. of The maintenance costs canbehigh, for distanceapplications. shorter variesThe capitalcost the dependingon for longerdistanceapplications andhigherfrequencytransmission systems aretransmissions, suitablefor orlongerdistance shorter andFM withUHF transmissionthe frequencyDepending on (and powerlevel)the systems with currenttechnologies. transmissionthese usedigital protocols andarethus readily compatible (transceiver), communication.thus easilyenablingbi-directional of Most Oftenthe devicestransmitter comprise a andreceiver inoneunit (~477MHz),UHF FM (~100MHz)orsimilarbasedsystems. These canbe WiFi (2-5GHz), Bluetooth(2.4GHz), ZigBee (800MHz–2.4GHz), in various communicatethat locations witheachotherbyradio waves. Radio Frequencytransmitters basedsystemsworkbyhaving andreceivers the availability ofexcellent algorithms, encryption for particularly digitalsignals. than wirelesstechnologies, hasbeenmorethis distinction orlessremoved with While wiredtechnologies havetraditionally beenconsideredto bemore secure power and and power water corporation 75 Solar/Diesel Mini-Grid Handbook Contact us

Call 1800 245 092 Email [email protected] Visit powerwater.com.au Follow PowerWaterCorp on Twitter ABN 15 947 352 360

Head office

Level 2, Mitchell Centre 55 Mitchell Street, Darwin GPO Box 1921 Darwin NT 0801

Customer service centres

Shop 28, Ground Floor, Mitchell Centre 55 Mitchell Street, Darwin

Shop 21, Palmerston Shopping Centre 10 Temple Terrace, Palmerston

Ground Floor, Government Centre 5 First Street, Katherine

Shop 8, Alice Plaza 36 Todd Mall, Alice Springs