Electric Rickshaw Charging Stations As Distributed Energy Storages for Integrating Intermittent Renewable Energy Sources: a Case of Bangladesh

energies

Article Electric Rickshaw Charging Stations as Distributed Energy Storages for Integrating Intermittent Renewable Energy Sources: A Case of Bangladesh

A.S.M. Mominul Hasan

Department of Energy and Environmental Management, Europa-Universitaet Flensburg, 24943 Flensburg, Germany; mominul.hasan@uni-ﬂensburg.de; Tel.: +49-461-805-2555

Received: 30 October 2020; Accepted: 20 November 2020; Published: 22 November 2020

Abstract: This exploratory research outlines an opportunity for increasing renewable energy share in Bangladesh by using electric rickshaws (e-rickshaws) as a catalyst. The overall objective of this research is to show how to utilise an existing opportunity, such as e-rickshaws, as energy storage options for integrating renewable energy sources. It proposes a grid-connected local energy system considering a battery swapping and charging station (BSCS) for e-rickshaws as a community battery energy storage (CBESS). This system was simulated using the HOMER Pro software. The simulation results show that such systems can help communities signiﬁcantly reduce their dependency on the national grid by integrating solar PV locally. The proposed BSCS also shows an opportunity for battery demand reduction and circular battery management for electric rickshaws. The research also discusses the economies of scale of the proposed method in Bangladesh, and pathways for implementing microgrids and smart energy systems. The innovative concepts presented in this research will start a policy-level dialogue in Bangladesh for utilising local opportunities to ﬁnd an alternative energy storage solution and provide momentum to the researchers for further studies.

Keywords: electric rickshaw; battery swapping station; battery energy storage system; community energy storage; renewable energy integration; microgrids; smart energy systems

1. Introduction The intermittent characteristics of renewable energy (RE) sources, especially solar and wind, is a major challenge for integrating them into the grid [1]. Energy storage systems are considered to beg the most suitable add-ons along with variable energy technologies for technically and economically safe integration in the grid [2]. The literature oﬀers a diversity of energy storage options, such as pumped hydro, batteries and compressed air, some of which are considered to be economically attractive in the current time horizon [3]. However, there is a serious lack of studies in the literature that outline suitable energy storage options for developing countries, such as Bangladesh. Bangladesh is considering using hydro resources from Nepal and Bhutan through cross-border electricity trade for meeting its increasing energy demand, which can also be used as storage to handle the variability of local renewable resources [4]. However, this option is still in an initiation phase and lacks suﬃcient economic, technical, and geopolitical studies. Realising a need for studies to foster RE integrations in developing countries, the Energy Sector Management Assistance Program (ESMAP) of the World Bank Group has launched a new initiative in 2019 called Energy Storage Partnership (ESP) for developing energy storage solutions [5]. Similarly, the Asian Development Bank (ADB) has also released a handbook on battery energy storage systems (BESSs) in 2018 for the promotion of RE integrations [1]. This book mentions several options for BESS and emphasises lithium-ion technology considering the market growth due to electric vehicles (EVs). However, this study completely overlooks the proliferation

Energies 2020, 13, 6119; doi:10.3390/en13226119 www.mdpi.com/journal/energies Energies 2020, 13, 6119 2 of 28 of informal EVs, such as electric rickshaws, and consequent growth of lead-acid battery market. Considering these facts, taking Bangladesh as a case country, the author scrutinises how existing opportunities, such as electric rickshaw, can be utilised as energy storage options with the help of modern technologies. The remainder of this article continues with a background study on electric rickshaws and renewable energy situation in Bangladesh, a comprehensive technology review for developing suitable storage option, simulation of a case using HOMER Pro software and results, and discussions on the result showing implications, economies of scale, and perceived challenges. The conclusions section summarises the ﬁndings and contributions of this work.

2. Background Study and Research Objective

2.1. Electric Rickshaw and Relevant Issues Battery-powered three-wheelers, also known as electric rickshaws, tuk-tuks or easy bikes, are one of the prevalent modes of public transports in developing Asian countries, such as India, Bangladesh, Cambodia, and Vietnam [6,7]. E-rickshaws are popular in these countries for first and last-mile connectivity. Nowadays, it is also one of the predominant means of daily commuting for people in many urban, semi-urban, and rural areas [7,8]. In this study, the term ‘e-rickshaw’ is chosen to address all the battery-powered three-wheelers available in developing countries. In Bangladesh, a typical e-rickshaw uses 4–5 lead-acid batteries that offer around 4.8–6 kWh of energy at 48–60 V. On average, an e-rickshaw can carry 4–6 passengers. The market for e-rickshaws in developing countries is thriving without proper planning to meet the growing transportation demand [9,10]. The deployment of e-rickshaw also lacks appropriate legislation. Because of unplanned growth, it puts on an additional burden on the existing energy infrastructure [7,11]. For example, in Bangladesh, while brownouts are frequent events because of insufficient energy supply to the grid, the additional energy demand of over a million of e-rickshaws adds fuel to the fire [12,13]. Considering energy issues, the Government of Bangladesh has already taken initiatives to promote solar photovoltaic (PV)-powered charging stations. However, so far, only 14 charging stations have been built, which have an aggregated capacity of less than 300 kW. All these charging stations are built off-grid and offer plug-in charging options, which is time consuming and does not add any other value. The author argues that with the help of modern technologies, the charging of e-rickshaws can be improved significantly from the technical and economic points of view. Lead-acid batteries (LABs) are the commonly used energy carriers for e-rickshaws in Bangladesh. Recently, the domestic market size of LABs in Bangladesh has grown to nearly 1 billion USD [14]. At the same time, in India, the market is expected to reach 7.6 billion USD by 2030 [15]. In [14,15] the authors point out that this boom is especially due to the proliferation of local electric vehicles (e.g., e-rickshaws). Bangladesh alone hosts more than 25 LAB manufacturers. The retail battery market is the primary procurement source of e-rickshaw batteries. The lack of proper standardisation of e-rickshaw batteries causes considerable quality variation in the retail market. Also, there is no distinct policy for battery take-back and recycling for the used lead-acid batteries (ULABS) of e-rickshaws. In Bangladesh, despite some recognised recycling facilities, most ULABs are poorly managed. As a result, ULABs end up in scrap material businesses near human settlements. A study on toxic site identification in Bangladesh by Pure Earth 2018 identified that ULABs are predominantly responsible for 175 toxic sites located in different places in the country [16]. Some other sources [17,18] have reported a similar situation in India. According to the report, the Indian capital of Delhi alone discards nearly 1 million e-rickshaw ULABs annually. Therefore, despite offering zero tail-pipe emissions, e-rickshaws are also considered a threat to the environment because of the unregulated disposal of ULABs [17,19]. In [17,20], the authors identify the short battery life as one of the predominant factors behind the high disposal rate. They also find that e-rickshaw batteries typically last less than one year, Energies 2020, 13, 6119 3 of 28 and sometimes only 4–6 months. From a technical point of view, poor battery quality (in terms of Energies 2020, 13, x FOR PEER REVIEW 3 of 28 materials), and inadequate depth of discharge (DOD) and state of charge (SOC) management are the major causes of this short battery life [21]. There are several factors that may cause poor DOD and major causes of this short battery life [21]. There are several factors that may cause poor DOD and SOC management. For example, inadequate knowledge about battery health and poor quality charge SOC management. For example, inadequate knowledge about battery health and poor quality charge controllers [22]. The LABs used in e-rickshaws typically take 8–10 h until full charge, which affects the controllers [22]. The LABs used in e-rickshaws typically take 8–10 h until full charge, which affects working hours of e-rickshaw drivers. As a result, drivers often deep discharge the batteries to extract the working hours of e-rickshaw drivers. As a result, drivers often deep discharge the batteries to every Ampere before recharging [22]. extract every Ampere before recharging [22]. Being an informal and unregulated mode of transport, issues related to e-rickshaws, such as Being an informal and unregulated mode of transport, issues related to e-rickshaws, such as battery demand, battery disposal and relevant economic and health impact, are rarely addressed battery demand, battery disposal and relevant economic and health impact, are rarely addressed in in national statistics and research. Newspapers and the grey literature are the primary sources of national statistics and research. Newspapers and the grey literature are the primary sources of information on this sector, which lacks acceptance in different entities, such as science. Therefore, information on this sector, which lacks acceptance in different entities, such as science. Therefore, the the author urges immediate action by policy makers and researchers to identify and address these author urges immediate action by policy makers and researchers to identify and address these issues issues of serious importance. The author also argues that with the help of modern technologies and of serious importance. The author also argues that with the help of modern technologies and innovative battery management, the problems related to e-rickshaws can be turned into a catalyst for innovative battery management, the problems related to e-rickshaws can be turned into a catalyst for sustainable development. sustainable development. 2.2. Renewable Energy in Bangladesh 2.2. Renewable Energy in Bangladesh Bangladesh is the home of over 160 million people, with a population density greater than Bangladesh is the home of over 160 million people, with a population density greater than 1100 1100 persons per square kilometre. The country’s electricity generation is highly reliant on fossil persons per square kilometre. The country’s electricity generation is highly reliant on fossil fuels, fuels, especially on its own natural gas, which represent over 60% of the total energy mix as shown in especially on its own natural gas, which represent over 60% of the total energy mix as shown in Figure Figure1[ 23]. To date, renewable energy penetration in Bangladesh is below 5%, although the country 1 [23]. To date, renewable energy penetration in Bangladesh is below 5%, although the country aimed aimed to achieve 10% penetration by 2020 [4,24]. to achieve 10% penetration by 2020 [4,24].

Figure 1. Grid energy generation mix of Bangladesh in financial year 2018–2019. Total generation was 70.53Figure GWh, 1. Grid which energy includes generation imports mix from of Bangladesh India [23]. in financial year 2018-2019. Total generation was 70.53 GWh, which includes imports from India [23]. Solar energy is the most available and proven renewable energy resource in Bangladesh. GlobalSolar horizontal energy irradianceis the most (GHI) available is between and proven 4–6 kWh renewable/m2/day. energy However, resource up to in September Bangladesh. 2020, Global only ahorizontal tiny portion irradiance of the potential (GHI) is hasbetween been 4–6 realised. kWh/m The2/day. total However, installed up capacity to September of solar 2020, PV technologies only a tiny isportion slightly of overthe potential 400 MWp, has including been realised. over 4 millionThe tota solarl installed home systemscapacity forof osolarff-grid PV electrification technologies asis shownslightly in over Figure 4002 [MWp,25]. Land including scarcity over and 4 grid million constraints solar home are the systems major hindrancesfor off-grid forelectrification implementing as expandedshown in Figure solar energy2 [25]. Land technology scarcity use and [4 grid]. To constraints cope with theare landthe major scarcity hindrances issue, the for Government implementing of Bangladeshexpanded solar has announcedenergy technology a net metering use [4]. policy To cope in2018 with to the promote land scarcity rooftop issue, solar PV.the TheGovernment nationwide of potentialBangladesh of rooftophas announced solar PV is a estimated net metering to be overpolicy 8000 in MW 2018 [26 ].to Sincepromote variability rooftop of solarsolar energy PV. The is a majornationwide challenge potential to integrate of rooftop solar solar PV in PV the is grid, estimated it is not to practical be over to8000 implement MW [26]. the Since entire variability potential of solar PVenergy considering is a major the challenge existing to grid integrate infrastructure solar PV and in the system grid, stability. it is not Thus,practical to solveto implement these issues the comprehensiveentire potential studiesof solar arePV necessary,considering which the existing calls for grid immediate infrastructure action. and system stability. Thus, to solve these issues comprehensive studies are necessary, which calls for immediate action.

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Figure 2. Installed capacity of RE technologies forfor electricityelectricity generationgeneration inin BangladeshBangladesh asasof of2020 2020 [ 25]. [25]. 2.3. Rationale of This Study 2.3. RationaleGrowing of demand This Study for transportation and mobility deficit in Bangladesh offers the opportunity to introduceGrowing electric demand mobility. for transportation To date, the and people mobility of Bangladeshdeficit in Bangladesh have successfully offers the grabbedopportunity this opportunityto introduce andelectric introduced mobility. electric To date, mobility the peop in thele form of Bangladesh of e-rickshaws. have However, successfully this grabbed introduction this wasopportunity neither and formal introduced nor planned. electric As mobility a result, in the e-rickshaws form of e-rickshaws. may soon becomeHowever, a nationalthis introduction burden. Onwas theneither other formal hand, nor the planned. Government As a result, of Bangladesh e-rickshaws is preparingmay soon become for an ambitious a national targetburden. for On solar the PVother implementation hand, the Government without addressing of Bangladesh technological is preparing challenges, for an such ambitious as variability target of for solar solar energy PV generationimplementation [26,27 ].without The author addressing aims to coupletechnological both these ch issuesallenges, to findsuch a scientificallyas variability sound of solar pathway energy for widergeneration adoption. [26,27]. The The author author argues aims that to couple e-rickshaws both canthese be issues a catalyst to find for achievinga scientifically the renewable sound pathway energy targetsfor wider of theadoption. country. The The author approach argues of thisthat studye-rickshaws will help can to be promote a catalyst microgrids for achieving for decentralisation the renewable ofenergy power targets systems. of the The country. outcome The of this approach study is of expected this study to start will policy help levelto promote dialogues microgrids and opening for newdecentralisation research avenues. of power systems. The outcome of this study is expected to start policy level dialogues and opening new research avenues. 2.4. Objective 2.4. Objective 2.4.1. General Objective 2.4.1.The General overall Objective objective of this research is to outline a pathway to utilise an existing opportunity, such as e-rickshaws, as energy storage options for integrating renewable energy sources. The overall objective of this research is to outline a pathway to utilise an existing opportunity, 2.4.2.such as Specific e-rickshaws, Objectives as energy storage options for integrating renewable energy sources. To assess relevant technology and practices that can be materialised to find a scientific approach •2.4.2. Specific Objectives for creating a nexus among technologies, e-rickshaw, and renewable energy related problems. • To assess relevant technology and practices that can be materialised to find a scientific approach To assess suitability of the identified approach through a case study in Bangladesh that can address • for creating a nexus among technologies, e-rickshaw, and renewable energy related problems. the general objective and address the problems discussed in the background section. • To assess suitability of the identified approach through a case study in Bangladesh that can 3. Technologyaddress the Review general objective and address the problems discussed in the background section. 3.1. Battery Energy Storage System (BESS) for Integrating Renewable Energy (RE) Sources 3. Technology Review BESS is considered being a significant catalyst for integrating RE into the grid globally [1]. BESS3.1. Battery offers Energy several Storage technical System features (BESS) that for canIntegrating provide Renewable adequate Energy support (RE) to Sources the grid to handle the variabilityBESS is of considered wind and solarbeing energy a significant sources, catalyst such asfor energy integrating time-shifting, RE into the voltage grid globally ramp up [1]. or BESS load following,offers several frequency technical regulationfeatures that and can peak provide shaving adequate [1,2, 28support–31]. to In the [30 grid], the to authorshandle the recognise variability 13 servicesof wind thatand cansolar be energy offered sources, by BESSs. such The as authors energy alsotime-shifting, identify relevant voltage stakeholders ramp up or whoload canfollowing, benefit frequency regulation and peak shaving [1,2,28–31]. In [30], the authors recognise 13 services that can be offered by BESSs. The authors also identify relevant stakeholders who can benefit from BESS, such

Energies 2020, 13, x FOR PEER REVIEW 5 of 28 as independent system operators, utilities, and customers of the power system (see Figure 3). Apart from load shifting, most ancillary services required for RE integration are instantaneous power- Energies 2020, 13, 6119 5 of 28 dependent and less energy-intensive [1]. Therefore, the authors in [1,30] point out that single application of BESS may not offer a net economic benefit, hence a stackable value proposition is necessary.from BESS, such as independent system operators, utilities, and customers of the power system (seeTypically, Figure3). BESSs Apart are from configured load shifting, as stationary most ancillary and batteries services are required assembled for REin containers. integration An are aggregatedinstantaneous form power-dependent of the batteries of andelectric less vehicles energy-intensive (EVs) at a [ 1single]. Therefore, point can the also authors be compared in [1,30] pointas a BESS.out thatHowever, single this application opportunity of BESS is rarely may explored not oﬀer in a the net literature economic for beneﬁt, providing hence RE a integration stackable valueand otherproposition ancillary is services. necessary.

Figure 3. Illustration of 13 services offered by BESS to three main stakeholders: (1) Utility, Figure(2) Customer, 3. Illustration (3) Independent of 13 services System offered Operator, by BESS ISO to or three Regional main Transmission stakeholders: Organizers, (1) Utility, RTO.(2) Customer,Source: Fitzgerald (3) Independent et al. 2015 System [30]. Operator, ISO or Regional Transmission Organizers, RTO. Source: Fitzgerald et al. 2015 [30.] Typically, BESSs are configured as stationary and batteries are assembled in containers. 3.2.An Community aggregated Energy form of Storage the batteries (CES) of electric vehicles (EVs) at a single point can also be compared as a BESS. However, this opportunity is rarely explored in the literature for providing RE integration and Similar to community energy phenomenon [32], community energy storage (CES) is an existing other ancillary services. concept to make communities self-sufficient in energy. In Europe, there are a handful of CES systems providing3.2. Community several Energy services Storage to differ (CES)ent communities [33]. A case study reported in [33] identifies that the major actors of CES are network operators, such as local utility companies, energy cooperatives, and housingSimilar associations. to community For energy further phenomenon adoption of [ 32CES,], community the authors energy in [34] storage mention (CES) that is social an existing and behaviouralconcept to makeaspects communities need to be actively self-suffi addressedcient in energy. as well In as Europe, techno-economic there are a handfulissues. The of CES authors systems in [34]providing present severalthree configurations services to diff oferent CES, communities which can be [33 implemented]. A case study for reportedcommunities in [33 in] identifies rural areas. that Thethe first major configuration actors of CES in the are table network “shared operators, resident suchial energy as local storage” utility companies,is comparable energy with cooperatives,the concept ofand a peer-to-peer housing associations. solar energy For sharing further network adoption of ofthe CES, company the authors SOLSHARE in [34] mentionin Bangladesh that social [35]. andIn thisbehavioural network, aspectsenergy needgenerated to be activelyby solar addressed home systems as well (SHS) as techno-economic is stored batteries issues. at The different authors households.in [34] present Then three the configurationsenergy is shared of among CES, which the ho canuseholds be implemented connected for in communitiesthe network. inThe rural second areas. configuration,The first configuration “shared local in the energy table storage”, “shared residential which is are energy suggested storage” to install is comparable behind the with local the electric concept transformer.of a peer-to-peer Energy solar flow energy in this sharing configuration network remains of the company mostly within SOLSHARE the community in Bangladesh for enhancing [35]. In this self-sufficiencynetwork, energy and generated surplus production by solar home is either systems exported (SHS) isto storedthe grid batteries or curtailed. at different However, households. dual purposeThen the of energystorage is is shared rarely amongstudied the in householdsthe field of CES connected for example in the network.use of electric The secondvehicle configuration, batteries as CES.“shared The author local energy argues storage”, that this configuration which is are suggested can also be to imagined install behind with the the concept local electric with aggregated transformer. batteriesEnergy flowof EVs/e-rickshaws in this configuration at a single remains point mostly within the community for enhancing self-sufficiency and surplus production is either exported to the grid or curtailed. However, dual purpose of storage is rarely studied in the field of CES for example use of electric vehicle batteries as CES. The author Energies 2020, 13, 6119 6 of 28 argues that this configuration can also be imagined with the concept with aggregated batteries of EVs/e-rickshaws at a single point

3.3. Battery Swapping Station (BSS) The battery swapping concept stands for replacing discharged batteries with a fully charged one, especially in an EV. This technology is nearly 100 years old. Because of the rapid growth of fossil fuel based vehicle and less use of electric vehicles (EVs), this technology could not flourish like petrol stations [36]. Today, battery swapping stations is becoming popular again to avoid charging time for EV. China is already in the forefront of this movement for offering battery swapping services to electric cars and motorcycles [37]. BSSs offer an energy service model rather than battery ownership, which minimises the risks of low battery lifetime to the vehicle owners [38]. BSSs also offer less investment compared to distributed EV charging points [39]. However, this option is rarely explored for e-rickshaws. Similarly, the concept of using BSSs as BESS or CES for integrating variable renewable energy sources in the grid is also seldom considered.

3.4. Microgrid and Smart Energy Systems Nowadays, microgrids are a popular concept for decentralisation and democratisation of power systems. This concept offers utilisation of local renewable energy resources to increase self-sufficiency at the same time reduce dependency on national grid. It has a significant potential to improve reliability of electric power system, which is a wide discussion in Bangladesh [40]. In [41] the authors claims that the microgrid can also act as an electric vehicle aggregator to integrate EVs into power systems, and provide additional storage services. However, in Bangladesh, the microgrid concept is only studied for off-grid electrification. Considering the proliferation of e-rickshaws in Bangladesh, the author argues that e-rickshaws can help enhance the adoption of the microgrid concept in Bangladesh. Sector coupling is one of the major pillars for smart energy systems towards maximising the share of renewable energy in the energy mix [42]. EVs are recognised as a potential pathway for coupling electric energy system with transportation. However, in developing countries, introducing formal EVs, such as cars and trucks, is still challenging for various reasons, such as availability of EVs, cost, technological challenge, infrastructure, and the availability of energy in the grid [43]. E-rickshaws and e-bikes are, on the other hand, bypassing these barriers and growing informally. The authors in [44] demonstrate that vehicle to grid (V2G) technology as an option for integrating RE sources in the grid. However, due to capacity constraints, the impact of a single EV on the grid is insignificant while investment cost for charging infrastructures for numerous EVs is very high [45,46]. Unlike formal EVs, the potential of V2G and G2V technologies for informal EVs (e.g., e-rickshaws) is highly underexplored from the perspective of smart energy systems. The potential reasons behind this could be bulky battery size (e.g., lead-acid battery), lifetime, and low energy content of batteries among other. Therefore, the author envisages an opportunity to explore the potential of an e-rickshaw BSCS to grid concept, which can initiate the process of smart energy systems in rural areas. Such smart energy systems can enable coupling other sectors, such as electric river transportation (e.g., ferryboats), agriculture and productive use of energy.

3.5. Potential Application of Existing Technologies for EVs/E-Rickshaws The literature reviews on different scientific approaches and technologies presented above, can be stacked on each other to create an innovative approach for addressing the problems described in the background of this study. Figure4 below shows an option for systematic application of the above mentioned technologies that can help to address the problems sustainably. The figure summaries that the first step is to switch from traditional plug-in charging to swap charging by establishing a BSCS. Then using the BSCS as a CES, which can adopt the technology advantages of BESS for RE integration. Then the CBESS enables the process of implementing microgrid and smart energy system. Energies 2020, 13, 6119 7 of 28 Energies 2020, 13, x FOR PEER REVIEW 7 of 28

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Figure 4. Application of existing technologies in this research to address the problems. Figure 4. Application of existing technologies in this research to address the problems. The author argues that the novel approach can oﬀer several outcomes as outlined in Table1. An exampleThe author ofFigure this argues novel 4. Application that approach the novel of existing is shownapproach technologies in Figurecan offe in5 this,r in several research terms outcomes ofto address an energy the as problems.outlined system in in rural Table area. 1. An example of this novel approach is shown in Figure 5, in terms of an energy system in rural area. TableThe 1. Stackable author argues technologies, that the theirnovel applications, approach can and offe implicationsr several outcomes for e-rickshaws as outlined and REin Table promotion. 1. An Tableexample 1. ofStackable this novel technologies, approach is shown their inapplications, Figure 5, in andterms implications of an energy forsystem e-rickshaws in rural area. and RE promotion.Technology Application Implication Table 1. Stackable technologies, their applications, and implications for e-rickshaws and RE Technologypromotion. - Saving Application time needed for charging Implication e-rickshaws/EVs BSCS -Saving time needed for charging e- - Supports for RE integration, such as Technology - E-rickshaw Application battery management -Supports forenergy-time RE Implication integration, shift, reduce such curtailmentas energy- BSCS -Saving timerickshaws/EVs needed for charging e- and ancillary services. -Supportstime shift, for reduceRE integration, curtailment such as and energy- ancillary BSCS -E-rickshaw- Storingrickshaws/EVs battery energy management from locally generated - Extend battery life and reduction of time shift, reduce curtailmentservices. and ancillary -Storing-E-rickshawenergy energy battery from from RE management sources. locally battery disposal CBESS -Extend batteryservices. life and reduction of battery CBESS generated- -StoringBattery energy energy management from from RE locally sources. -Extend battery life anddisposal reduction of battery CBESS generated energy from RE sources. -Battery management disposal - -BatteryAggregating management local RE generators, -Aggregating local RE generators, -Increase- Increase RE share RE sharein local in localenergy energy mix mix -Aggregatingstorages, local and RE grid generators, to meet -Increase RE share in local energy mix MicrogridMicrogrid storages, and grid to meet local -Reduce- Reduce dependency dependency on national on national grid. grid. Microgrid storages,local and demands. grid to meet local -Reduce dependency on national grid. demands. -Enhance- Enhance reliability reliability of power of power system. system. demands. -Enhance reliability of power system. -Migration- Migration from fossil from fuel-based fossil fuel-based system to Smart Energy Systems - Sector coupling in rural areas -Migration from fossil fuel-based system to SmartSmart Energy Energy system to electrical energy system. -Sector-Sector coupling coupling in in rural rural areasareas electricalelectrical energy energy system. system. SystemsSystems

FigureFigure 5. The 5. The concept concept of of rural rural smart smart energy energy systemssystems usin usingg a aBSCS BSCS for for e-rickshaws. e-rickshaws. Major Major components components includeinclude e-rickshaw e-rickshaw or or similar similar transports, distribu distributedted/rooftop/rooftop solar solarPV, local PV, grid, local local grid, utility, local and utility, andFigure auxiliaryauxiliary 5. The batteryconcept battery sets setsof asrural as community community smart energy battery battery systems energy energy storage usin storageg asystem BSCS system (author’sfor e-rickshaws. (author’s illustration). illustration). Major components include e-rickshaw or similar transports, distributed/rooftop solar PV, local grid, local utility, and auxiliary battery sets as community battery energy storage system (author’s illustration).

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Energies 2020,, 13,, xx FORFOR PEERPEER REVIEWREVIEW 8 of 28 4. Case Study with the Identiﬁed Approach 4. Case Study with the Identified Approach 4.1. Case Formulation 4.1. Case Formulation This case study considers a small grid-connected rural community in Bangladesh to realise the conceptThis case in study terms considers of an energy a small system. grid-connected The case community rural community assumes in aBangladesh household to stock realise of 500the householdsconcept in terms and 50 of e-rickshaws an energy system. for e-mobility. The case With community this two demandassumes groups,a household an energy stock systemof 500 architecturehouseholds wasand designed50 e-rickshaws as shown for ine-mobility. Figure6. For Wi theth this sack two of simplicity, demand commercialgroups, an energy and industrial system sectorsarchitecture was kept was outdesigned of scope. as shown Solar PV in Figure technology 6. For and the gridsack were of simplicity, considered commercial as energy and sources industrial in the system.sectors was Electric kept rickshawsout of scope. were Solar integrated PV technology in the systemand grid through were considered a BSCS which as energy is represented sources in in the a combinationsystem. Electric of a rickshaws CBESS and were e-rickshaw integrated charging in the load.system through a BSCS which is represented in a combination of a CBESS and e-rickshaw charging load.

Figure 6. Figure 6. Architecture of the system for HOMER Pro softwaresoftware (author’s(author’s illustration).illustration). It assumes the BSCS comprises two sets of batteries for each e-rickshaws. The nominal operating It assumes the BSCS comprises two sets of batteries for each e-rickshaws. The nominal operating voltage of a typical e-rickshaw in Bangladesh is 48 V DC, which is achieved using four LABs in series. voltage of a typical e-rickshaw in Bangladesh is 48 V DC, which is achieved using four LABs in series. Hence, the battery requirement for 50 e-rickshaws is 200. To oﬀer one swap per day for 50 e-rickshaws, Hence, the battery requirement for 50 e-rickshaws is 200. To offer one swap per day for 50 e-rickshaws, the BSCS requires 400 batteries i.e., two battery sets or battery packs for each e-rickshaw. Figure7 the BSCS requires 400 batteries i.e., two battery sets or battery packs for each e-rickshaw. Figure 7 shows the daily operations of two sets of batteries. shows the daily operations of two sets of batteries.

Figure 7.7. Daily operation of two sets of batteries. 4.2. Simulation Software 4.2. Simulation Software ® For simulation and analysis, this case study uses the HOMER Pro microgrid® software by HOMER For simulation and analysis, this case study uses the HOMER Pro® microgridmicrogrid softwaresoftware byby Energy. HOMER Pro is a widely used simulation software for renewable energy systems. HOMER HOMER Energy. HOMER Pro is a widely used simulation software for renewable energy systems. Pro can perform three main tasks, such as simulation, optimisation, and sensitivity analysis. HOMER HOMER Pro can perform three main tasks, such as simulation, optimisation, and sensitivity analysis. pro uses least cost optimization model. It determines best possible mix of energy resources to deliver HOMER pro uses least cost optimization model. It determines best possible mix of energy resources to deliver least-cost solutions. During simulation when a system configuration is found sufficient to meet the demand, it calculates the life cycle costs for that system configuration. Details of the

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Energies 2020, 13, x FOR PEER REVIEW 9 of 28 least-cost solutions. During simulation when a system configuration is found sufficient to meet the demand,simulation it calculatesmodel and the calculations life cycle costs can for be that found system in [47–50]. configuration. The following Details of section the simulation describes model the anddifferent calculations input canparameters be found infor [47 the–50 ].simulation The following. The section subsequent describes section the diff erentdescribes input parametersimportant forassumptions the simulation. for this The case subsequent study. section describes important assumptions for this case study.

4.3. Defining Deﬁning System Demands Household Energy Demand for thethe Community:Community: Electricity consumption of the community was assumed as as per per the the bottom bottom line line of of Tier Tier 3 3energy energy consumption consumption (1 (1kWh/household/day), kWh/household/day), according according to tothe the multi-tier multi-tier framework framework of the of theWorld World Bank Bank [51] [51. The]. The aggregated aggregated electricity electricity consumption consumption for the for thecommunity community was wascalculated calculated to be to 500 be kWh/day. 500 kWh/ day.Figure Figure 8 shows8 shows the average the average daily daily community community load. load.The load The curve load was curve determined was determined by using by the using built-i then built-incommunity community load profile load of proﬁle HOMER of HOMERPro software Pro software[47]. For simplicity, [47]. For simplicity, seasonal variation seasonal variationwas omitted. was omitted.

Figure 8.8. AverageAverage daily daily total total load load of theof the system. system. The totalThe total is the is sum the of sum community of community load and load e-rickshaw and e- batteryrickshaw charging battery load.charging The load. annual The demand annual wasdemand calculated was calculated to be 256,595 to be kWh. 256,595 kWh.

Energy Demand for E-rickshaw: ForFor each each e-rickshaw, e-rickshaw, a 7.2 kWh battery capacity was considered, which comprisescomprises fourfour batteries,batteries, each each having having a a capacity capacity of of 150 150 Ah Ah at at 12 12 V. V. Daily Daily total total energy energy demand demand for 50for e-rickshaws50 e-rickshaws was was calculated calculated at 203 at 203 kWh kWh considering considering DOD DOD 50% 50% and and a charging a charging eﬃciency efficiency of 89% of 89% [21]. The[21]. estimatedThe estimated daily energydaily energy demand demand for 50 e-rickshaws for 50 e-rickshaws or 200 batteries or 200 was batteries kept constant was kept throughout constant thethroughout year. The the load year. curve The was load determined curve was bydetermined using the by charging using the power charging required power at 0.1 required C charging at 0.1 rate C ofcharging typical rate lead-acid of typical batteries, lead-acid which batteries, can be which found incan [52 be]. found Figure in8 also[52]. showsFigure the 8 also load shows proﬁle the of load the e-rickshawprofile of the battery e-rickshaw charging battery load. In charging the load curve,load. In the the charging load durationcurve, the was charging considered duration during was the typicalconsidered sunshine during hours the typical of a day sunshi whenne grid hours have of morea day energy when grid from have solar more PV. energy from solar PV.

4.4. Solar Resource The solar irradiation data was collected from a location (geographic coordinates: 23.97N, 23.97N, 90.88E) 90.88E) in Bangladesh, which isis a potential site for BSCS development. The data is shown on Figure9 9.. AnnualAnnual 2 average GHI waswas foundfound toto bebe 4.65 4.65 kWh kWh/m/m /2day./day. The The data data was was populated populated using using integrated integrated function function of dataof data collection collection in in HOMER HOMER Pro Pro software, software, which which collects collects data data from from NASANASA surfacesurface meteorologymeteorology and solar energy.

Energies 2020, 13, 6119 10 of 28 Energies 2020, 13, x FOR PEER REVIEW 10 of 28 Energies 2020, 13, x FOR PEER REVIEW 10 of 28

Figure 9. Monthly average daily solar irradiation for the assumed system location. Figure 9. MonthlyMonthly average daily solar irradiation for the assumed system location. 4.5. System Components and Costs 4.5. System System Components and Costs PV systems: The PV system size was determined by using the HOMER Optimizer™ algorithm, PV systems: TheThe PV PV system system size size was was determined by by using using the HOMER Optimizer™ Optimizer™ algorithm, which calculates the economically optimised capacity of the PV array required for meeting the which calculatescalculates the the economically economically optimised optimised capacity capa ofcity the of PV the array PV requiredarray required for meeting for themeeting demands. the demands. The capital investment cost of PV system was considered is 600 Euro/kWp, which includes Thedemands. capital The investment capital investment cost of PV systemcost of wasPV system considered was isconsidered 600 Euro/ kWp,is 600 whichEuro/kWp, includes which PV modulesincludes PV modules with an efficiency of 20% [26]. The annual operation and maintenance cost was set to be withPV modules an efficiency with an of 20%efficiency [26]. Theof 20% annual [26]. operation The annual and operation maintenance and maintenance cost was set tocost be was 8 Euro set/ kWp.to be 8 Euro/kWp. From the implementation point of view, rooftop PV systems were considered for the 8From Euro/kWp. the implementation From the implementation point of view, rooftoppoint of PV view, systems rooftop were PV considered systems were for the considered system as for shown the system as shown in Figure 5. systemin Figure as5 .shown in Figure 5. Battery energy storage or CBESS: For battery energy storage or CBESS, flooded lead-acid batteries Battery energy storage or CBESS: For battery energy storage or CBESS, flooded flooded lead-acid batteries were considered. A total of 200 batteries were considered in the system as storage. The nominal were considered. A A total total of 200 batteries were consideredconsidered in thethe systemsystem asas storage.storage. The nominal capacity of each battery is 1.8 kWh. The aggregated capacity of the battery bank results to be 360 kWh. capacity of each battery is 1.8 kWh. The The aggregated aggregated ca capacitypacity of of the the battery battery bank bank results results to to be be 360 360 kWh. kWh. The capital investment of the battery bank was considered is 153 Euro/kWh and 110 Euro/kWh as The capital investment of the battery bank was co considerednsidered is 153 Euro/kWh Euro/kWh and 110 Euro/kWh Euro/kWh as replacement cost. The annual cost of operation and maintenance was set to 5 Euro/battery. replacement cost.cost. The The annual annual cost cost of operation of operation and maintenance and maintenance was set towas 5 Euro set/ battery.to 5 Euro/battery. Considering Considering 4 years of lifetime, the DOD was set to 60%, and a round trip efficiency is assumed to be Considering4 years of lifetime, 4 years the of DODlifetime, was the set DOD to 60%, was and set ato round 60%, and trip eaffi roundciency trip is assumedefficiency to is beassumed 80%. to be 80%. 80%. System converter: Like the PV systems, the HOMER Optimizer™ was also used for calculating the System converter: Like the PV systems, the HOMER Optimizer™ was also used for calculating optimumSystem capacity converter of: the Like system the PV converter. systems, HOMER the HOMER calculates Optimizer™ converter was capacity also used based for on calculating maximum the optimum capacity of the system converter. HOMER calculates converter capacity based on theDC loadoptimum and maximumcapacity of AC the load system need toconverter. be served HOMER from storage. calculates It was converter assumed capacity that the converterbased on maximum DC load and maximum AC load need to be served from storage. It was assumed that the maximumcan perform DC the load functionalities and maximum of BESS AC forload VRE need integration. to be served Therefore, from storage. the capital It was cost assumed of the converter that the converter can perform the functionalities of BESS for VRE integration. Therefore, the capital cost of wasconverter set to can 300 Europerform/kW the with functionalities an efficiency of 95%BESS and for aVRE lifetime integration. of 10 years Therefore, [1]. the capital cost of the converter was set to 300 Euro/kW with an efficiency of 95% and a lifetime of 10 years [1]. the converterLocal grid: wasHOMER set to 300 advanced Euro/kW grid with option an efficiency was considered of 95% for and the a lifetime grid component. of 10 years The [1]. HOMER Local grid: HOMER advanced grid option was considered for the grid component. The HOMER advanceLocal grid grid: option HOMER allows advanced energy grid import option to and was export considered from thefor the local grid grid component. according toThe a dynamicHOMER advance grid option allows energy import to and export from the local grid according to a dynamic advancerate definition, grid option as shown allows in Figureenergy 10import. To simulate to and ex theport actual from situation the local of grid the according rural electricity to a dynamic system rate definition, as shown in Figure 10. To simulate the actual situation of the rural electricity system ratein Bangladesh, definition, as a reliabilityshown in Figure factor was10. To also simulate considered. the actual The situation mean outage of the frequency rural electricity was set system to be in Bangladesh, a reliability factor was also considered. The mean outage frequency was set to be 200 in200 Bangladesh, times/year witha reliability a mean factor repair was time also of30 considered. min. The mean outage frequency was set to be 200 times/year with a mean repair time of 30 min. times/year with a mean repair time of 30 min.

Figure 10. Dynamic rate deﬁnition of grid electricity price (power price and sellback rate) and conditions Figure 10. Dynamic rate definition of grid electricity price (power price and sellback rate) and Figurefor CBESS 10. dispatch.Dynamic rate definition of grid electricity price (power price and sellback rate) and conditions for CBESS dispatch. conditions for CBESS dispatch. 4.6. Key Assumptions 4.6. Key Assumptions

Energies 2020, 13, 6119 11 of 28

4.6. Key Assumptions

4.6.1. Battery DOD and Capacity Selection The overall DOD of batteries was set to be 60%. It assumes that when batteries are used in e-rickshaws, it can be discharged up to 50%. To keep a reserve for immediate grid services, 10% more DOD was set when batteries are returned to the BSCS. To select the value of the operational DOD of batteries, the life cycle vs. DOD curve of the LABs from the e-rickshaw battery manufacturer and literature were studied. It was found that at 60% DOD; the batteries oﬀer around 1700 cycles, which can be translated into 4 years and 240 days considering one cycle per day [53,54]. Considering DOD of 50%, required battery capacity was calculated to be 150 Ah, which oﬀers around 8 h of operation per day. For the calculation of operation hours Equation (1) was developed. The equation uses technical parameters of e-rickshaw presented in [55]. The authors in the reference claim that average energy consumption of an e-rickshaw is 34 Wh/km at an average speed of 13 km/h.

E % DOD Operation time (h) = batt × (1) L aS batt × where Ebatt is the total capacity of e-rickshaw battery in kWh, Lbatt is average energy consumption in Wh/km, and aS is the average speed of e-rickshaw in km/h.

4.6.2. Battery Charging and Discharging For charging and discharging of the batteries, the Homer Kinetic Battery Model [47] was used. The mathematical model for the kinetic battery model is provided in AppendixA. Table2 shows the parameters and respective values that are used in the kinetic battery model.

Table 2. Parameters for Kinetic Battery Model in Homer Software.

Parameters Value Nominal Voltage (V) 12 Round Trip Eﬃciency (%) 80% Minimum State of Charge (%) 40% Maximum Charge Rate (A/Ah) 1 Maximum Charge Current (Amp) 15 Maximum Discharge Current (Amp) 300 (considering 2C rate)

4.6.3. Local Grid A dynamic rate was set considering the electricity tariff based on the time of use (TOU) approach. In Bangladesh, TOU is defined as off-peak (23:00–17:00) and peak (17:00–23:00) hours for commercial users [56]. The values of TOU were set in the grid component primarily to prohibit charging of CBESS during peak hours when sunlight is rarely available. Currently, in Bangladesh, there is no sellback price policy. However, the sellback rate was set in the simulation to prohibit energy selling from battery to the grid between 23:00 and 05:00. During this period, energy demand in the grid is very low, and PV systems are inactive. The sellback rate was considered allowing the batteries to be charged from the grid if SOC is below 100% before swapping. This the value of the considered sellback rate is comparable with the retail electricity price in Bangladesh. The sellback rate was also used for calculating the value of excess electricity to be sold to the grid.

4.6.4. Control Logic of Grid-Connected Solar PV The simulation assumes the grid-connected solar PV operates independently regardless the demand in the system, any surplus power is considered to be exported to the grid. An equivalent ﬂowchart is given in AppendixB. Energies 2020, 13, 6119 12 of 28

4.6.5. Operational Strategy and Control Logic of CBESS The CBESS is assumed to offer different services required for solar PV integration in the grid, suchEnergies as 2020 energy, 13, x FOR time-shift PEER REVIEW and PV output smoothing. Figure 11 shows daily operations of the12 of CBESS 28 which is controlled by the time of a day. An equivalent flow chart is also presented in AppendixC. which is controlled by the time of a day. An equivalent flow chart is also presented in Appendix C. However, the dynamic rate as shown on Figure 10 is used in HOMER Pro software as a control logic of However, the dynamic rate as shown on Figure 10 is used in HOMER Pro software as a control logic the functionalities. of the functionalities.

Figure 11. Time-based daily operational strategy of CBESS. Batteries are charged mainly during the Figure 11. Time-based daily operational strategy of CBESS. Batteries are charged mainly during the day at the same time it provides grid services. day at the same time it provides grid services. 4.6.6. Economic Assumptions 4.6.6. Economic Assumptions The following parameters are used for economic calculations in HOMER Pro software: The following parameters are used for economic calculations in HOMER Pro software: Discount rate: 12% •• Discount rate: 12% • Inﬂation rate: 5.7% • Inflation rate: 5.7% • Project lifetime: 25 years • Project lifetime: 25 years

5.5. Results and and Discussion Discussion of of the the Case Case Study Study The simulation results results to to be be discussed discussed here here were were chosen chosen based based onon a maximum a maximum capacity capacity of system of system converterconverter in didifferentfferent system configurations, configurations, wh whichich was was found found to to be be 93 93 kW. kW. The The maximum maximum capacity capacity of theof the converter converter was was chosen chosen to to assume assume thethe maximummaximum supports supports for for ramping ramping up up of ofsolar solar PV PVoutput output for for compensatingcompensating active power power during during moving moving cloud. cloud. The system configurations configurations as as shown shown in in Table Table 3 3were were sorted sorted from from a list a list of ofresults results by byRE RE fraction fraction andand PVPV capacities capacities at at a positivea positive cost cost of energyof energy (COE). (COE). All these All these configurations configurations include include similar similar capacities ofcapacities converter, of converter, batteries, batteries and similar, and energysimilar energy demand. demand. The system The system configuration configuration with with no solarno solar PV or gridPV or only grid was only considered was considered as the as base-case the base-case to compare to compare the results the results with diwithfferent different RE fraction RE fraction options. REoptions. fraction RE abovefraction 94.4% above showed 94.4% ashowed negative a negati COE becauseve COE ofbecause very highof very negative high negative operating operating cost, which iscost, not which realistic. is not Hence, realistic. those Hence, results those were results omitted. were omitted.

TableTable 3. 3. SelectedSelected system system configurations conﬁgurations from from the the simulated simulated results. results. Annual Demand Converter Capacity Annual Demand Converter SystemSystem Configuration Conﬁguration Solar Solar PV (kWp) PV (kWp) RE Fraction RE Fraction (%) (%) (kWh) (kWh) Capacity(kW) (kW) 1 Grid Only (Base Case) 0 0.0 2 1 Grid RE 74.8% Only +Grid (Base Case) 235 0 74.8 0.0 3 2 RERE 87.2% 74.8% + Grid+Grid 469 235 87.2 74.8 256,595 93 3 RE 87.2% + Grid 469 87.2 256,595 93 4 RE 89.3% + Grid 563 89.3 4 RE 89.3% + Grid 563 89.3 5 RE 94.4% + Grid 1079 94.4 5 RE 94.4% + Grid 1079 94.4

The simulation result shows that a community of 500 households and 50 e-rickshaws can achieve moreThe than simulation 70% RE resultpenetration shows by that integrating a community 235 ofkWp 500 of households solar PV in and the 50 local e-rickshaws grid. Figure can achieve 12 morecompares than the 70% energy RE penetration balance of by different integrating system 235 kWpconfigurations. of solar PV According in the local to grid. the figure, Figure 12solar compares PV thecan energyhelp such balance communities of different to meet system the energy configurations. demand for According households to and the e-rickshaws. figure, solar Integration PV can help suchof PV communities can significantly to meet help thesuch energy communities demand reducing for households dependency and e-rickshaws.on fossil fuel-based Integration national of PV cangrid. significantly In addition, the help community such communities can also export reducing a significant dependency amount on of fossilenergy fuel-based to the grid nationalwhich can grid. help generate local economic benefits. For example, the system configuration 3 with 87% RE offers COE of 0.036 Euro, which is less than 4 Bangladeshi Taka (BDT) and less than the retail grid energy price. This configuration allows the community to export nearly 640 MWh of energy to the grid

Energies 2020, 13, 6119 13 of 28

In addition, the community can also export a significant amount of energy to the grid which can help generate local economic benefits. For example, the system configuration 3 with 87% RE offers COE of 0.036 Euro, which is less than 4 Bangladeshi Taka (BDT) and less than the retail grid energy price. Energies 2020, 13, x FOR PEER REVIEW 13 of 28 ThisEnergies configuration 2020, 13, x FOR allowsPEER REVIEW the community to export nearly 640 MWh of energy to the grid against13 of 28 90 MWh of import annually. By exporting this amount of energy, the community can generate an against 90 MWh of import annually. By exporting this amount of energy, the community can generate incomeagainst 90 of MWh nearly of 15,000 import Euro annually. in each By year. exporting this amount of energy, the community can generate an income of nearly 15,000 Euro in each year. an income of nearly 15,000 Euro in each year.

Figure 12. AnnualAnnual energy energy balance in the systems in different diﬀerent system conﬁgurations.configurations. Figure 12. Annual energy balance in the systems in different system configurations.

According to to the the base base case case configuration, conﬁguration, annual annual CO CO2 emission2 emission is about is about 17 t/year 17 t/year because because of high of According to the base case configuration, annual CO2 emission is about 17 t/year because of high highemission emission factor factor (670 (670g/kWh) g/kWh) in the in national the national grid. grid. By charging By charging the thee-rickshaw e-rickshaw using using the thegrid, grid, e- emission factor (670 g/kWh) in the national grid. By charging the e-rickshaw using the grid, e- e-rickshawsrickshaws are are also also responsible responsible for for significant signiﬁcant indirect indirect CO CO22 emissions.emissions. Therefore, Therefore, inclusion inclusion of of solar PV rickshaws are also responsible for significant indirect CO2 emissions. Therefore, inclusion of solar PV in the system can help the community achieve net negative CO2 emission balance through electricity in the system can help the community achieve net negative CO2 emission balance through electricity export andand operating operating e-rickshaws. e-rickshaws. Figure Figure 13 shows 13 sh thatows when that REwhen fraction RE reachesfraction 87%, reaches the community 87%, the export and operating e-rickshaws. Figure 13 shows that when RE fraction reaches 87%, the achievescommunity net achieves negative net CO negative2 balance CO of 4102 balance t/year. of 410 t/year. community achieves net negative CO2 balance of 410 t/year.

Figure 13. CO2 emission balance in the systems. The balance was calculated considering grid emission Figure 13. COCO2 emissionemission balance balance in in the the systems. systems. The The balanc balancee was was calculated calculated considering considering grid emission factor of Bangladesh,2 which is 670 g/kWh. factor of Bangladesh, which is 670670 gg/kWh./kWh. Figure 14 compares net present cost (NPC), capital investment, and respective cost of energy for Figure 14 compares net present cost (NPC), capitalcapital investment, and respective cost of energy for each of the configurations. Surprisingly, the base case shows that by charging the e-rickshaws from each of the conﬁgurations.configurations. Surprisingly, the base case shows that by charging the e-rickshaws from the grid, the community pays higher price for electricity. This also results in very high net present the grid, the community pays higher price for electricity. This also results in very high net present costs. The economic parameters can be improved substantially by integrating solar PV in the system. costs. The economic economic parameters parameters can can be be improved improved subs substantiallytantially by by integrating integrating solar solar PV PV in in the the system. system. For example, integration of 469 kWp of solar PV in the system can help reduce the cost of energy as For example,example, integrationintegration of of 469 469 kWp kWp of of solar solar PV PV in in the the system system can can help help reduce reduce the the cost cost of energy of energy as low as low as 0.036 Euro/kWh, which is still lower than the minimum retail grid electricity price in aslow 0.036 as 0.036 Euro/ kWh,Euro/kWh, which which is still loweris still than lower the than minimum the minimum retail grid retail electricity grid priceelectricity in Bangladesh. price in Bangladesh. The main reason for the very low COE is because of a dramatic reduction in solar PV Bangladesh. The main reason for the very low COE is because of a dramatic reduction in solar PV installation costs, which have fallen by 40% in the past 3 years in Bangladesh [26]. installation costs, which have fallen by 40% in the past 3 years in Bangladesh [26].

Energies 2020, 13, 6119 14 of 28

The main reason for the very low COE is because of a dramatic reduction in solar PV installation costs, whichEnergies have2020, 13 fallen, x FOR by PEER 40% REVIEW in the past 3 years in Bangladesh [26]. 14 of 28

Figure 14.14. Net present cost (NPC), capital investment andand cost of energy (COE) in didifferentﬀerent systemsystem conﬁguration.configuration. Right axis shows the cost of energy while the left axis shows NPC (grey bars), capital investmentinvestment forfor thethe wholewhole systemsystem (orange(orange bar)bar) andand PVPV capitalcapital costcost (yellow(yellow bar).bar).

To implementimplement anyany of thesethese configurationsconfigurations mentionedmentioned in Table 3 3 with with solarsolar PV,PV, the the microgrid microgrid concept can be adopted. adopted. Thanks Thanks to to the the grid-connect grid-connecteded configuration configuration of ofthe the BSCS, BSCS, which which can can also also be beused used as asa CBESS a CBESS to tohelp help integrate integrate solar solar PV PV smoothly. smoothly. Relevant Relevant supports supports required required for for solar PV integrationintegration is discusseddiscussed inin followingfollowing subsections.subsections. To implement solar PV systems, both tooftop and ground-mounted centralisedcentralised systems can be considered.considered. Figure Figure 55 inin thethe earlierearlier sectionsection showsshows thethe rooftop solarsolar PVPV systemsystem concept. concept. Since Since the the current current policy policy of of Bangladesh Bangladesh does does not not off offerer asellback a sellback price price to theto the households, households, household-based household-based rooftop rooftop PV development PV development will not bewill attractive. not be Therefore,attractive. communityTherefore, ownedcommunity ground-mounted owned ground-mounted system and large system rooftop and solarlargePV rooftop programs solar can PV beprograms accelerated. can be In Bangladesh,accelerated. aIn solar Bangladesh, PV system a solar of 469 PV kWp system would of require469 kWp a surfacewould require area around a surface 3700 area m2. Thesearound surface 3700 m areas2. These can besurface the rooftops areas can of be shared the rooftops facilities of inshared rural facilities areas, such in rural as roofs areas, of such schools, as ro andofs of rural schools, marketplaces. and rural Themarketplaces. suitable location The suitable for the location BSCS can for be the identified BSCS ca byn consideringbe identified solar by considering PV injection solar points PV in injection the grid andpoints common in the grid hub and for e-rickshaws.common hub for e-rickshaws.

5.1. Supports for solar Solar PV PV integration Integration As discussed in the literature review, stackablestackable valuevalue streamsstreams werewere recommendedrecommended forfor BESSBESS business models to makemake themthem economicallyeconomically attractiveattractive [[1,30].1,30]. The stackable value streams cancan alsoalso be imaginedimagined for thethe CBESSCBESS businessbusiness model.model. The BSCSBSCS as a CBESS cancan supportsupport solarsolar PVPV integrationintegration mentioned aboveabove by by stacking stacking two two potential potential services services of of BESS. BESS. These These services services are electricare electric energy energy time-shift time- andshiftancillary and ancillary services. services. 5.1.1. Electric Energy Time-Shift 5.1.1. Electric Energy Time-shift. Typically, the main operation hours of e-rickshaw and sunshine-hours occur at the same time. Typically, the main operation hours of e-rickshaw and sunshine-hours occur at the same time. Hence, to use solar energy in mobile e-rickshaws, a time-shift of PV generated energy is necessary. Hence, to use solar energy in mobile e-rickshaws, a time-shift of PV generated energy is necessary. To cater for energy services of 50 e-rickshaws, it is necessary to shift 203 kWh of energy daily. Thanks to To cater for energy services of 50 e-rickshaws, it is necessary to shift 203 kWh of energy daily. Thanks the BSCS concept, which makes the time shift easier without compromising working hours for battery to the BSCS concept, which makes the time shift easier without compromising working hours for charging. Figure 15 shows two time-shift options. battery charging. Figure 15 shows two time-shift options.

Energies 2020, 13, 6119 15 of 28 Energies 2020, 13, x FOR PEER REVIEW 15 of 28 Energies 2020, 13, x FOR PEER REVIEW 15 of 28

FigureFigure 15. 15. Renewable Renewable energy energy time-shifttime-shift optionsoptions for poweri poweringpoweringng e-rickshaws. e-rickshaws. Option Option 1 offers1 offers offers same same day day time-shifttime-shift and and Option Option 2 2 ooffers ffoffersers nextnext next dayday day timetimetime shift.shift. 5.1.2. Capacity Firming/Solar PV Output Smoothing 5.1.2.5.1.2. Capacity Capacity Firming/Solar Firming/Solar PV PV Output Output SmoothingSmoothing Since the system was considered grid-connected, the integration of a higher amount of solar Since the system was considered grid-connected, the integration of a higher amount of solar PV PV canSince potentially the system lead was to considered instability. grid-connected, Because of moving the integration clouds, the of output a higher of amount solar PV of fluctuates solar PV can potentially lead to instability. Because of moving clouds, the output of solar PV fluctuates throughoutcan potentially a day, lead which to instability. is the predominant Because of cause moving for the clouds, instability. the output For example, of solar it PV causes fluctuates active throughoutthroughout a aday, day, which which is is the the predominant predominant cause foforr thethe instability.instability. For For exam example,ple, it itcauses causes active active powerpower and and frequency frequency fluctuations fluctuations in in thethe powerpower system. Thus, Thus, solar solar PV PV integration integration requires requires ancillary ancillary power and frequency fluctuations in the power system. Thus, solar PV integration requires ancillary servicesservices for for smoothing smoothing variable variable solar solar PV PV output.output. Figure 1616 shows shows an an example example of of PV PV output output smoothing smoothing services for smoothing variable solar PV output. Figure 16 shows an example of PV output smoothing usingusing energy energy storage. storage. using energy storage.

Figure 16. Figure 16.Example Example of of solar solar PVPV outputoutput/ramp/ramp rate smoothi smoothingng using using battery battery energy energy storage storage on on a cloudy a cloudy day between 9:00–15:00 in California [57]. Blue line shows the fluctuating output of a PV system. Figureday between 16. Example 9:00–15:00 of solar in CaliforniaPV output/ramp [57]. Blue rate line smoothi showsng the using fluctuating battery output energy of storagea PV system. on a cloudyRed Redline line shows shows desired desired output output of a ofPV a system PV system against against its variability. its variability. The green The greenline shows line showscharging charging and day between 9:00–15:00 in California [57]. Blue line shows the fluctuating output of a PV system. Red anddischarging discharging of the of the storage storage for forsmoothing smoothing PV output. PV output. line shows desired output of a PV system against its variability. The green line shows charging and Thedischarging proposed of the BSCS storage as afor CBESS smoothing can PV play output. a vital role for by providing services such as active The proposed BSCS as a CBESS can play a vital role for by providing services such as active powerpower control, control, voltage, voltage, and and frequency frequency regulationregulation wh whileile batteries batteries are are charging charging during during the the day. day. On On a a The proposed BSCS as a CBESS can play a vital role for by providing services such as active timetime window, window, these these services services require require shortshort durations,durations, which which is is instantaneous instantaneous power power (kW) (kW) intensive intensive power control, voltage, and frequency regulation while batteries are charging during the day. On a ratherrather than than energy energy (kWh) (kWh) [ 1[1].]. Therefore, Therefore, toto oofferffer these services, services, a a CBESS CBESS may may not not need need to tohave have a high a high leveltimelevel ofwindow, SOC.of SOC. Throughput these Throughput services based based require calculation calculation short ofdurations, batteryof battery life which life can can beis usedinstantaneous be used to identify to identify power the impactthe (kW) impact onintensive battery on liferatherbattery due than to life grid energy due services. to (kWh) grid services. [1]. Therefore, to offer these services, a CBESS may not need to have a high level of SOC. Throughput based calculation of battery life can be used to identify the impact on 5.2.battery5.2. An An Opportunitylife Opportunity due to grid for for Reducingservices. Reducing BatteryBattery DisposalDisposal TheThe lack lack of of suitable suitable battery battery managementmanagement results in in a a shorter shorter battery battery life life leading leading to tohigher higher battery battery 5.2. An Opportunity for Reducing Battery Disposal disposal.disposal. The The BSCS BSCS concept concept can can play play a significanta significant role role in in better better battery battery management management and and extend extend the the life The lack of suitable battery management results in a shorter battery life leading to higher battery disposal. The BSCS concept can play a significant role in better battery management and extend the

Energies 2020, 13, 6119 16 of 28

Energies 2020, 13, x FOR PEER REVIEW 16 of 28 ofEnergies e-rickshaw 2020, 13 batteries., x FOR PEER To REVIEW manage DOD of batteries, the battery swapping and charging station16 of 28 can setlife a pre-defined of e-rickshaw maximum batteries. DOD To manage values DOD in the of battery batteries, boxes. the Thebattery control swappi mechanismng and charging can be similarstation to life of e-rickshaw batteries. To manage DOD of batteries, the battery swapping and charging station can set a pre-defined maximum DOD values in the battery boxes. The control mechanism can be thecan concept set a pre-defined of a prepaid maximum solar home DOD system. values However, in the battery in this boxes. case, The e-rickshaw control mechanism drivers will can have be to similar to the concept of a prepaid solar home system. However, in this case, e-rickshaw drivers will returnsimilar their to batteriesthe concept to of the a BSCSprepaid before solar thehome batteries system reach. However, the pre-defined in this case, DOD. e-rickshaw drivers will have to return their batteries to the BSCS before the batteries reach the pre-defined DOD. haveFigure to return 17 shows their lifebatteries expectancy to the ofBSCS batteries before in the di ffbatterieserent DOD reach levels. the pre-defined According theDOD. graph, a battery Figure 17 shows life expectancy of batteries in different DOD levels. According the graph, a can beFigure used more17 shows than life 4 years,expectancy if 60% of DODbatteries is maintained. in different DOD Using levels. this DODAccording value the and graph, lifetime, a battery can be used more than 4 years, if 60% DOD is maintained. Using this DOD value and lifetime, it wasbattery found can be that used e-rickshaw more than battery 4 years, use if 60% demand DOD is can maintained. be reduced Using by 3-foldthis DOD without value compromisingand lifetime, it was found that e-rickshaw battery use demand can be reduced by 3-fold without compromising energyit was services. found that e-rickshaw battery use demand can be reduced by 3-fold without compromising energy services. energy services.

FigureFigure 17. 17.Depth Depth of of discharge discharge vs vs cyclecycle lifelife (orange(orange line) and and equivalent equivalent life life expectancy expectancy (blue (blue dots) dots) of of Figure 17. Depth of discharge vs cycle life (orange line) and equivalent life expectancy (blue dots) of LABsLABs used used in in e-rickshaws. e-rickshaws. The The grey grey barsbars showshow marginalmarginal cycles cycles for for every every 10% 10% additional additional DOD DOD [53]. [53 ]. LABs used in e-rickshaws. The grey bars show marginal cycles for every 10% additional DOD [53]. FigureFigure 18 18below below compares compares the the requirement requirement of batteries of batteries for e-rickshaw for e-rickshaw between between status status quo (battery quo Figure 18 below compares the requirement of batteries for e-rickshaw between status quo life(battery 1 year) life and 1 BSCSyear) optionand BSCS (battery option life (battery 8 years). life From8 years). the From ﬁgure the it canfigure be seenit can that be seen over that the over lifetime the of (battery life 1 year) and BSCS option (battery life 8 years). From the figure it can be seen that over the thelifetime project, of battery the project, demand battery can be demand reduced can signiﬁcantly be reduced by implementingsignificantly by a BSCS.implementing Compared a toBSCS. status lifetime of the project, battery demand can be reduced significantly by implementing a BSCS. quo,Compared the BSCS to optionstatus quo, can the save BSCS nearly option 3500 can batteries, save nearly which 3500 will batteries, eventually which reducewill eventually battery reduce disposal. Compared to status quo, the BSCS option can save nearly 3500 batteries, which will eventually reduce It isbattery important disposal. to mention It is important here that to mention in BSCS optionhere that battery in BSCS life option was set battery to be li 8fe years was set since to be each 8 years battery battery disposal. It is important to mention here that in BSCS option battery life was set to be 8 years completessince each a cyclebattery in 2completes days. For a example,cycle in 2 whiledays. For one example, set of batteries while isone powering set of batteries e-rickshaw, is powering other set e- of since each battery completes a cycle in 2 days. For example, while one set of batteries is powering e- rickshaw, other set of batteries are being charged at BSCS. And the next day battery sets are altered. batteriesrickshaw, are other being set charged of batteries at BSCS. are being And thecharged next at day BSCS. battery And sets the arenext altered. day battery sets are altered.

Figure 18. Annual battery requirements for 50 e-rickshaws. The blue bars represent status quo, which FigureFigure 18. 18.Annual Annual battery battery requirements requirements forfor 5050 e-rickshaws. The The blue blue bars bars represent represent status status quo, quo, which which is no swapping and no battery management and considering 1-year lifetime. Orange bar represents is nois no swapping swapping and and no no battery battery management management andand consideringconsidering 1-year 1-year lifetime. lifetime. Orange Orange bar bar represents represents battery requirements for BSCS with one swap a day with battery management to maintain 60% DOD. batterybattery requirements requirements for for BSCS BSCS with with oneone swapswap a da dayy with with battery battery management management to tomaintain maintain 60% 60% DOD. DOD. Battery lifetime was set to be 8 years considering one cycle in two days. BatteryBattery lifetime lifetime was was set set to to be be 8 8 years years considering considering one cycle in two two days. days. 5.3. An Opportunity for Creating a Sustainable and Circular Value Chain for E-Rickshaw Batteries 5.3. An Opportunity for Creating a Sustainable and Circular Value Chain for E-Rickshaw Batteries

Energies 2020, 13, 6119 17 of 28

5.3. An Opportunity for Creating a Sustainable and Circular Value Chain for E-Rickshaw Batteries Energies 2020, 13, x FOR PEER REVIEW 17 of 28 To oﬀer energy services to e-rickshaws through a BSCS, batteries need to be purchased in bulk To offer energy services to e-rickshaws through a BSCS, batteries need to be purchased in bulk quantity. Therefore, a BSCS can enable a sustainable value chain of e-rickshaw batteries shown quantity. Therefore, a BSCS can enable a sustainable value chain of e-rickshaw batteries shown in in FigureFigure 19 19..

Figure 19. E-rickshaw battery value chain for BSCS option. Figure 19. E-rickshaw battery value chain for BSCS option. For example, to procure batteries for the BSCS, the owner/operator can arrange contracts with the For example, to procure batteries for the BSCS, the owner/operator can arrange contracts with batterythe manufacturer battery manufacturer/supplier/supplier directly. directly. Instead Instead of the of retail the supplyretail supply chain, chain, bulk quantitiesbulk quantities of batteries of can bebatteries purchased can be through purchased an through open tendering an open /tenderbiddinging/bidding processes. processes. This process This process can includecan include speciﬁc standards,specific quality, standards, and quality, take-back and take-back ULABs. ULABs. The existing The existing business business model model of ULABof ULAB take-back take-back inin SHS programSHS inprogram Bangladesh in Bangladesh can be can consulted be consulted to implement to implement the the sustainablesustainable value value chain chain of e-rickshaw of e-rickshaw batteriesbatteries [58]. [58].

5.4. Economies5.4. Economies of Scale of Scale Currently,Currently, in Bangladesh, in Bangladesh, there there are are over over 1 1 million million of e-rickshaws e-rickshaws and and the the number number is still is stillgrowing growing considerably.considerably. According According to to the the battery batterylife life inin status quo, quo, annual annual demand demand of th ofe batteries the batteries is around is around 4 million. The amount of battery disposal is also in the similar range, however, there are no clear or 4 million. The amount of battery disposal is also in the similar range, however, there are no clear official statistics for this. The aggregated capacity of one million e-rickshaw batteries is around 5 GWh, or oﬃconsideringcial statistics four for batteries this. The per aggregatede-rickshaw and capacity each battery of one having million a e-rickshawcapacity of 100 batteries Ah at is12 aroundV. 5 GWh,Therefore, considering the economies four batteries of scale per for e-rickshawimplementing and BSCS each for battery all the e-rickshaws having a capacity in Bangladesh of 100 is Ah at 12 V. Therefore,substantial. theFor economiesexample, if ofthe scale simulated for implementing system is implemented BSCS for allforthe all e-rickshawse-rickshaws around in Bangladesh the is substantial.country, there For is example, a potential if thefor implementation simulated system of 20,000 is implemented BSCS and CBESS. for all These e-rickshaws CBESS can around help the country,stable there integration is a potential of nearly for 5 GWp implementation of solar PV in of the 20,000 grid which BSCS can and help CBESS. the country These achieve CBESS its can RE help stabletargets. integration Table 4 of below nearly shows 5 GWp economies of solar of scale PV in ofthe the gridsimulated which system can helpfor whole the country Bangladesh. achieve To its RE targets.determine Table this,4 below values showsof the economiessimulated system of scale we ofre thescaled simulated linearly. systemAccording for to whole the table, Bangladesh. the To determinemarket size this, of the values BSCS of concept the simulated is more than system 1.6 billion were Euro, scaled which linearly. can potentially According open to thea market table, the for solar PV a worth of 8 billon Euro. Nationwide scaling up the concept have a potential for reducing market size of the BSCS concept is more than 1.6 billion Euro, which can potentially open a market for 68 million batteries in 25 years, which is equivalent to 13.6 billion Euro (nominal). solar PV a worth of 8 billon Euro. Nationwide scaling up the concept have a potential for reducing 68 million batteries in 25 years,Table 4. which Economies is equivalent of scale of the to simulated 13.6 billion system Euro (linear). (nominal).

Economies of Table 4. Economies of scale of the simulated system (linear). System Parameters Simulated System Scale Unit Economies(Bangladesh) of Scale System Parameters Simulated System Unit Battery swapping and charging station (BSCS)(Bangladesh) Total e-rickshaw 50 1,000,000 Nos. Battery swapping and charging station (BSCS) Battery swapping station 1 20,000 Nos. IndividualTotal e-rickshaw battery capacity 50 1.8 1,000,000 1.80 kWhNos. Battery RequirementBattery swapping considering station 1 Swap/day (2 sets 1 20,000 Nos. 400 8,000,000 Nos Individualof batteries/e-rickshaw) battery capacity 1.8 1.80 kWh Battery Requirement considering 1 Swap/day (2 Capacity available for CBESS 400 0.36 8,000,000 7200 MWh Nos sets of batteries/e-rickshaw)

Energies 2020, 13, 6119 18 of 28

Table 4. Cont.

Economies of Scale System Parameters Simulated System Unit (Bangladesh) Battery swapping and charging station (BSCS) Capacity available for CBESS 0.36 7200 MWh Converter capacity 93 1,860,000 kW Required initial investment for battery € 55,000 € 1,100,000,000 Euro Required initial investment for system converter € 27,900 € 558,000,000 Euro Estimated total investment for BSCS € 82,900 € 1,658,000,000 Euro Solar PV integration ConfigurationEnergies 3 (RE 2020 87.2%, 13, x FOR+ Grid)PEER REVIEW per system 0.469 938618 of 28 MW Required initial investment (Configuration 3) € 0.28 € 5632 Million Euro Configuration 2 (RE 76%Converter+ Grid) percapacity system 0.235 93 1,860,000 4693 kW MW Required initial investmentRequired initial (Configuration investment for battery 2) € 0.14 € 55,000 € 1,100,000,000€ 2861 Euro Million Euro Required initial investment for system converter € 27,900 € 558,000,000 Euro Estimated total investmentReduction for BSCS of battery disposal € 82,900 (25 years) € 1,658,000,000 Euro Battery savingsSolar PV integration 3400 68,000,000 Nos. Cost savingsConfiguration for batteries 3 (RE (Nominal) 87.2% + Grid) per system € 0.68 0.469 € 9,38613,600 MW Million Euro Required initial investment (Configuration 3) € 0.28 € 5,632 Million Euro Configuration 2 (RE 76% + Grid) per system 0.235 4,693 MW 5.5. Microgrid andRequired Smart initial Snergy investment Systems (Configuration in Rural 2) Areas € 0.14 € 2,861 Million Euro Reduction of battery disposal (25 years) Battery savings 3400 68,000,000 Nos. Despite achievingCost savings remarkable for batteries progress (Nominal) in expanding € 0.68 grids for €energy 13,600 access, Million gridsEuro in many developing countries remain unreliable. According to [59], about 1.5 billion people globally, especially in developing5.5. countries, Microgrid experienceand Smart Snergy frequent Systems in brown Rural Areas and blackouts in their local grid. Lack of reliability promotes the deploymentDespite achieving of fossil remarkable fuel backup progress generators in expanding and grids redundant for energy systems.access, grids The in many CBESS can play developing countries remain unreliable. According to [59], about 1.5 billion people globally, a vital role to enhance the reliability in local grids. As a result, dependency on secondary or redundant especially in developing countries, experience frequent brown and blackouts in their local grid. Lack supply systemsof reliability will reduce. promotes Implementation the deployment of offossil microgrid fuel backup cangenerators be a potentialand redundant pathway systems. forThe enhancing reliability in powerCBESS systemscan play a combiningvital role to enhance different the reliability local and in regionallocal grids. stakeholders.As a result, dependency on secondary or redundant supply systems will reduce. Implementation of microgrid can be a potential The planning of smart energy systems is necessary towards decarburisation of energy sector. pathway for enhancing reliability in power systems combining different local and regional The conceptualstakeholders. CBESS presented can be a central component for realising such smart energy systems in rural areas as illustratedThe planning inof Figuresmart energy 20. Thesystems overarching is necessary towards application decarburisation of such of smartenergy sector. energy systems The conceptual CBESS presented can be a central component for realising such smart energy systems can create potentialin rural nexusareas as amongillustrated di inff Figureerent 20. sectors, The overarching such as application transportation, of such smart agriculture, energy systems productive use of electricity. can create potential nexus among different sectors, such as transportation, agriculture, productive use of electricity.

Figure 20. ConceptFigure 20. ofConcept smart of smart energy energy systems systems in inrural rural areas areasconsidering considering the BSCS/CBESS the as BSCS a central/CBESS as a central component.component.

Energies 2020, 13, 6119 19 of 28

5.6. Implementation Pathway and Business Bpportunities To offer seamless energy service for e-rickshaws/EVs, a network of BSCS is required combining neighbouring communities. The network of BSCS also offers the opportunities for implementing clustered microgrids. If the BSCSs are implemented together with microgrids, new business avenues will open in rural areas. For example, energy services for e-rickshaws, grid services for local utility, energy arbitrage, and virtual power plants (VPPs). Table5 summarises the potential business opportunities according to the business model canvas. The table shows that community, local entrepreneurs, and local utilities can play significant roles as stakeholders to generate local benefits. The BSCS business model can be realised as the business model of energy service companies (ESCOs), which can help reduce battery-related burdens of e-rickshaw owners/drivers. For example, drivers or owners need not think of the life of the battery, brand, price, place of purchase, and disposal of the batteries. E-rickshaw drives only need to pay for energy services and rent for batteries. Such a business model can help reduce the capital cost for purchasing e-rickshaw/e-vehicle since vehicle can be purchased without batteries. As a result, additional momentum can be created for phasing out combustion engine-based and human pulled traditional public transports that can be purchased without batteries. Lack of local human resource capacities and technology awareness, among others, are the major challenges for encouraging investment in renewable energy in rural areas in developing countries [60]. To overcome these challenges, a rural virtual power plant (RVPP) can be established either by the local utilities or the independent aggregators. RVPPs can help better management of energy in the local grids, ensuring maximum benefits for all stakeholders. At the same time, it can promote investment in the productive use of energy in rural areas. For example, it can bring rural power loads, such as rice husking, crushing mills, milk processing, and cottage industries under renewable energy supply through smart contracts and smart meters.

5.7. Challenges and Outlook There are several challenges that need to be addressed before adopting the BSCS and CBESS concept. For example, the simulated system considers a barrier-free export of excess energy to the neighbouring community or elsewhere through the grid. Grid constraints may be a hindrance for export and import of power. Spatial analysis on the grid capacities and demand in the neighbourhood, excess energy can be optimised using site-specific design. Bulky lead-acid batteries can be a major challenge for implementing BSCSs. This might result in a higher cost of retrofitting and a longer time for swapping. Battery swapping automation system can help reduce the time for swapping, but it would put additional investment costs. At the same time, achieving 8 years of life-time from lead-acid batteries would also be a challenge. For the sake of simplicity, these factors were omitted in this research. The author calls for an in-depth study on the economies of lead-acid battery swapping station. The study can also scrutinise issues with battery life. Battery swapping may lead to voltage-current transients in the system and different level of battery voltage in the same bus. To study the swapping effect in details, a power system analysis is required with high-resolution data. Similarly, to realise the scale of economy geographically, a comprehensive spatial study is also necessary to identify suitable locations for the BSCSs. The author considers these issues as outlooks of this paper to initiate further studies and to attract other researchers to explore this opportunity for its applications. Energies 2020, 13, 6119 20 of 28

Table 5. Stackable business opportunity of the BSCS and CBESS based on business model canvas.

Stackable Business Opportunities with the CBESS Battery Swapping and Grid Services Energy Arbitrage Rural Virtual Power Plant (RVPP) Charging Station

- E-rickshaw/electric - Community - Local PV System owners vehicle owners - Local utility - PV system owners - Local Utility Potential Stakeholders - Existing charging stations - Local entrepreneurs - Potential investors - Independent aggregators - Local entrepreneurs

- Renewable Energy - Renewable - Peak shaving - Battery packs for the - Forecasting capacity ﬁrming - Energy time shift for using e-rickshaws/e-vehicles - Trading Key - Energy time-shifting during peak hours - Energy services for the - Curtailment management Activities/Products/Services - Frequency regulation - Energy services during e-rickshaws/e-vehicles - Maintenance of distributed - Voltage regulation grid outages systems in rural area

- Investment cost for battery - Investment for converter - Additional investment for - Investment cost - Investment cost for - System BESS inverter for batteries ﬁxed infrastructure communication infrastructure - - Investment cost Cost Structure - Investment cost for - Meteorological infrastructure retroﬁtting Communication infrastructure for converter - Capacity development existing e-rickshaws - SCADA - Energy purchase - Battery swapping automation system

- Energy - Rent of battery packs - Sales of services based on - Rent of battery packs - Demand supply Revenue Streams for e-rickshaws Energy Power for e-rickshaws balancing charges - Sales of energy Service duration - Sales of energy - Fees for maintenance services of PV systems Energies 2020, 13, 6119 21 of 28

6. Conclusions To promote RE integration, especially in developing countries, this research presents the potential of taking advantage of an existing opportunity as a distributed energy storage option. Taking Bangladesh as a case country, first, it identifies the growing concerns about e-rickshaws and the challenges for RE integration. Second, through a comprehensive literature review on different technologies, it identifies that combining several technologies can help deliver a multipurpose solution that can offer several value propositions. For example, a battery swapping and charging station for electric vehicles can also be used as a community energy storage. Such community energy storage can potentially create an ecosystem for microgrid and smart energy systems, especially in rural areas. The literature also supports that concept of utilising battery swapping stations as battery-to-grid (B2G) and grid-to-battery (G2B) power transactions. In [61,62], the authors presented a similar study on battery swapping stations. The authors concluded that G2B- and B2G-enabled BSCS can benefit both customers and the utility through energy trading and eliminating the cost for new infrastructure, respectively. The case study presented here shows an innovative control procedure for the proposed CBESS. A pre-set value of DOD and time of the day are the core control variables of this proposal. This method helps battery management and extends the operational lifetime of batteries. The method for calculating battery capacity for e-rickshaw, grid-connected configuration of the BSCS, and the concept of next day time shift ensure adequate energy services for e-rickshaws and extend battery lifetime by reducing cycle use. It also helps in keeping the e-rickshaw energy service independent from the effect of intermittent solar PV generation. The microgrid simulation shows the RE integration potential in a small community. The simulation result revealed that integration of RE not only reduces the cost of energy, but also helps generate income through exporting energy. It also shows how such communities can become carbon neutral. The economies of scale show that currently there is a potential for 20,000 BSCS in Bangladesh. Following the CBESS approach of this research, the BSCSs can create a network of distributed energy storages throughout the country. Bangladesh has more than 60 thousand villages, therefore the network of BSCSs can be implemented either in each village or combining neighbouring villages based on household density and number of e-rickshaws in the vicinity. Since e-rickshaws and similar modes of transports are on the rise in many developing countries, especially in South and South East Asia, there is a significant potential for wide-scale adoption of this method. Finally, the outlook of this study shows a new avenue of research that will attract further researchers not only in e-rickshaws but also exploring other social opportunities for energy storage in developing countries.

Funding: The author acknowledges financial support for publication of this research by Land Schleswig-Holstein within the funding programme Open Access-Publikationsfonds. Acknowledgments: The author would like to express gratitude and thank warmly to the primary supervisor Bernd Möller, for his extended support for this research development and prompt reviews on the writing process. The author also extends thanks to Nasimul Islam Maruf and Jonathan Mole for their thoughtful comments and reviews in the earlier version of this paper. Further special appreciation goes to the colleagues of the Energy and Environmental Management department of the Europa-Universitaet Flensburg for their valuable comments that significantly improved this research article. The author is responsible solely for any error, and that should not tarnish the reputations of these esteemed persons. Conflicts of Interest: The author declares no conflict of interest. Energies 2020, 13, 6119 22 of 28

Appendix A

Appendix A.1. Kinetic Battery Model [47]

Total battery capacity Qmax Qmax = Q1 + Q2 (A1) where Q1 is the available energy and Q2 is the bound energy, which is bounded by limit of depth of discharge (DOD)

Appendix A.1.1. Kinetic Battery Model (kbm) for Determining Maximum Discharging (dmax) Power (Pbatt)

k∆t k∆t kcQmax + kQ e + Qkc 1 e − 1 − − − Pbatt,dmax,kbm = (A2) 1 e k∆t + c(k∆t 1 + e k∆t) − − − − where Q1 is the available energy [kWh] in the Storage Component at the beginning of the time step. Q is the total amount of energy [kWh] in the Storage Component at the beginning of the time step. Qmax is the total capacity [kWh] of the storage bank. c is the storage capacity ratio [unitless], c = 1 DOD, − depth of discharge. k is the storage rate constant [h 1]. And ∆t is the length of the time step [h]. − Maximum discharging power considering discharging eﬃciency

Pbatt,dmax = ηbatt,dPbatt,dmax,kbm (A3)

Appendix A.1.2. Kinetic Battery Model (kbm) for Determining Maximum Charging (cmax) Power (Pbatt)

kQ e k∆t + Qkc 1 e k∆t 1 − − − Pbatt,cmax,kbm = (A4) 1 e k∆t + c(k∆t 1 + e k∆t) − − − − where Q1 is the available energy [kWh] in the Storage Component at the beginning of the time step. Q is the total amount of energy [kWh] in the Storage Component at the beginning of the time step. c is the storage capacity ratio [unitless], c = 1 DOD, depth of discharge. k is the storage rate constant − [h 1]. And ∆t is the length of the time step [h]. − Maximum battery charging power considering maximum charge rate (Ah/h) αc∆t 1 e− (Qmax Q) P = − − (A5) batt,cmax,mcr ∆t where αc is the storage’s maximum charge rate [A/Ah] and Qmax is the total ca’acity of the storage bank [kWh]. Maximum battery power considering number of batteries in the storage bank

NbattImax,Vnom P = (A6) batt,cmax,mcc 1000 where Nbatt is the number of batteries in the storage bank. Imax = the storage’s maximum charge current [A] and Vnom is the storage’s nominal voltage [V]. Maximum storage charge power is the power considering’charging eﬃciency MIN Pbatt,cmax,kbm, Pbatt,cmax,mcr, Pbatt,cmax,mcc Pbatt,cmax = (A7) ηbatt,c Energies 2020, 13, x FOR PEER REVIEW 23 of 28

Maximum battery power considering number of batteries in the storage bank

𝑁𝐼,𝑉 𝑃 = (A6) ,, 1000 where Nbatt is the number of batteries in the storage bank. Imax = the storage’s maximum charge current [A] and Vnom is the storage’s nominal voltage [V]. Maximum storage charge power is the power considering’charging efficiency

Energies 2020, 13, 6119 𝑀𝐼𝑁(𝑃,,,𝑃,,,𝑃,,) 23 of 28 𝑃, = (A7) , Appendix B Appendix B

Figure A1. Flowchart for export and import from and to the grid. Figure A1. Flowchart for export and import from and to the grid.

Appendix C

Energies 2020, 13, 6119 24 of 28

Appendix C Energies 2020, 13, x FOR PEER REVIEW 24 of 28

FigureFigure A2. A2.Flowchart Flowchart of the CBESS control control strategy. strategy.

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