energies

Article New Energy Corridors in the Euro-Mediterranean Area: The Pivotal Role of

Salvatore Favuzza 1 ID , Mariano Giuseppe Ippolito 1, Fabio Massaro 1,* ID , Liliana Mineo 1, Rossano Musca 2 and Gaetano Zizzo 1 ID

1 Department of Energy, Information Engineering and Mathematical Models, DEIM, University of Palermo, 90128 Palermo (Pa), ; [email protected] (S.F.); [email protected] (M.G.I.); [email protected] (L.M.); [email protected] (G.Z.) 2 Neplan AG, Oberwachtstrasse 2, CH-8700 Küsnacht (ZH), Switzerland; [email protected] * Correspondence: [email protected]; Tel.: +39-(0)912-386-0295

 Received: 5 May 2018; Accepted: 29 May 2018; Published: 1 June 2018 

Abstract: The present paper deals with the new opportunities deriving from the interconnections of the European and North African transmission systems. In order to achieve a single international market for electricity exchanges, interconnections between networks in different countries are becoming increasingly important and Sicily, for its geographical position in the middle of the , will undoubtedly play an important role as an electrical bridge between and the North Africa in the near future. The paper, presenting the actual electro-energetic context of Tunisia, reports the new important interconnection already realized in South Italy (in particular in Sicily) and describe the planned interventions of the near future. In the second part of the paper, using the Neplan software package (10.7.4, NEPLAN AG, CH-8700 Küsnacht (ZH), Switzerland) for simulating the grid, some load flows are carried out to check some operating scenarios (2020 and 2025) considering energy flows from north to south, avoiding system violations.

Keywords: Sicily– interconnection line; Sicily–Italy doubling connection; RES integration; Mediterranean interconnection; transmission systems; EUMENA (European Union-Middle East and North Africa)

1. Introduction Electricity will play an increasingly important role in the near future on a regional and intercontinental scale [1]. Everywhere there are innovative projects to connect large-scale electrical systems and to share electricity produced from renewable sources in far-flung regions. Photovoltaic (PV) systems are replacing conventional generation. Reduced system inertia and lack of dynamic grid support from PV are the main issues that could have a detrimental impact on the transient response in power systems when critical contingencies arise [2]. Recent research presented a model of a utility-scale photovoltaic unit (USPVU) enhanced with an embedded hybrid energy storage system (HESS), suitable for stability studies in transmission systems [3]. Renewable energy sources should be exploited on sites where they are most available and where electricity production plants are more compatible (e.g., in the sunniest deserts); then the electricity should be distributed far away, where needed, through innovative, highly-efficient power lines, able to minimize transmission losses. Among the projects in this field Global-RT Superlab has just started to connect the electrical systems on an Atlantic scale, creating a submarine cable between the US and the EU, using high voltage direct current. At the Politecnico di Torino the Italian node of the Global-RT Superlab initiative is active to conduct experiments and simulations simultaneously in all the laboratories of the network, connected through the Atlantic in smart mode, thanks to computer tunneling on the Internet [4]. In 2015

Energies 2018, 11, 1415; doi:10.3390/en11061415 www.mdpi.com/journal/energies Energies 2018, 11, 1415 2 of 14

China launched another ambitious project to electrically connect the Asian regions with the European, Australian, and African ones: the “Global Energy Interconnection” (GEI) plan [5]. The European Union also launched the “Connecting Europe Facility” (CEF) program in 2013 to promote an innovative trans-European power line system; the Brussels plan is integrated with the so-called “Energy Union” package. For example, according to this program, Italy should develop super-interconnections with France, Switzerland, Austria, Slovenia, and Montenegro. Speaking of super smart-grids, the authors remember DESERTEC, the project to connect Europe with the Middle East and North Africa (the EUMENA macro-region). In this Mediterranean macro-region, with the Italian peninsula in the center, several electricity production plants powered by renewable sources should be connected to high voltage direct current lines (high voltage direct current, HVDC), offering a vision of sustainable development for the entire Mediterranean basin, which does not only concern energy, but also socio-economic prosperity, and the availability of food and water everywhere in EUMENA. All the changes mentioned before are modifying the logic of the development of the interconnections of electrical systems by the ENTSO-E (European Network of Transmission System Operators) [6] and proposing new issues related to system reliability and resilience [7,8]. With the prospect of a single European market for energy exchanges and an increase in RES, the interconnections between different countries’ electricity systems are becoming increasingly important. In fact, in recent years, the collaboration between Italy and Tunisia has increased thanks to the Italy-Tunisia Program. This program is part of the cross-border cooperation component (CBC) of the European Neighborhood and Partnership Instrument (ENPI) [9]. It involves five Sicilian provinces and six coastal regions of Tunisia. The main objective is to promote economic and social integration between the Sicilian and Tunisian territories through a process of joint and sustainable development based on a cross-border cooperation center. The authors actively participated in the ENPI 2007–2013 project, consolidating a scientific collaboration between the two territories through the research project DE.DU.ENER.T. (Le DEveloppement DUrable dans la production ENERgetique dans le Territoire) [10–13]. Both Italy and Sicily, its main island, geographically located in the heart of the Mediterranean Sea, will play an important role as a bridge between Central Europe and the North African area. The African continent will benefit from this interconnection thanks to the possibility of promoting the rise of new RES-based power plants [14–16]. The delicate political situation of the regions of North Africa, recorded in the last few years, causes some uncertainties about the development of renewables in that area. For some years, however, in particular in Tunisia, there has been an increase in the demand for energy and, therefore, as mentioned, Italy and Sicily can play a fundamental role in feeding these countries (in the close future), guaranteeing a lowering of the prices of electricity and, at the same time, limiting the emissions of climate-altering gases caused by power plants present in North Africa; in the event that, instead in a farther future, there will be a real development of renewable sources, Sicily and Italy will represent a corridor to dispatch this energy [17–21]. To pursue the three most important objectives of the European Union’s energy policy (EU) (system competitiveness, environmental sustainability, security of energy supply), the interconnection between the countries of North Africa and Europe is certainly an important priority [22]. In pursuing the EU 2020 and 2050 sustainability goals, particular attention is focused on the countries of the MENA region (Middle East and North Africa), which are located near the Mediterranean sea, and which can significantly contribute to the generation from renewable energy sources. For this reason the MSP (Mediterranean Solar Plan) was launched in 2008 by the European Union. The success of the initiatives are closely linked to the possibility of the European high-voltage network to dispatch energy from Africa. These choices could also increase other large energy flows coming from RES from Southern Europe, mostly due to the upgrading of photovoltaic systems. It is, therefore, clear that Italy and Spain are the main actors, geographically close to the African continent. Lastly, it is noted that the injection zones, geographically closer, for the importation of energy (the major islands: Sicily and Sardinia) are Energies 2018, 11, 1415 3 of 14 both electrically connected to the mainland. For these reasons, Italy is a candidate to assume a pivotal role in the Mediterranean basin. This paper is organized as follows: in the first part, European submarine interconnections, and the actual electro-energetic context of Tunisia, are reported; in the second part of the paper, using the Neplan software package for simulating a network model, some load flows are carried out to checkEnergies some 2018, 11 operating, x scenarios (2020 and 2025) considering energy flows from3 of 14 north to south, avoidingThis system paper is organized violations. as follows: In the in the conclusion, first part, European the results submarine obtained interconnections, show that and these new interconnectionsthe actual allow electro a‐energetic deeper context integration of Tunisia, of renewableare reported; in sources the second (meaning part of the a paper, lower using electricity the zonal prices) andNeplan a significant software package reduction for simulating in emissions a network from model, traditional some load units. flows are carried out to check some operating scenarios (2020 and 2025) considering energy flows from north to south, avoiding 2. Europeansystem Submarine violations. In Interconnections the conclusion, the results obtained show that these new interconnections allow a deeper integration of renewable sources (meaning a lower electricity zonal prices) and a significant In thereduction Mediterranean in emissions Sea, from there traditional are already units. some submarine electrical interconnections. Almost all the existing connections use HVDC technology, as it is an economically more advantageous solution 2. European Submarine Interconnections compared to high voltage alternating current (HVAC) in submarine links longer than some tens of km. In the Mediterranean Sea, there are already some submarine electrical interconnections. Almost The oldestall connecting the existing electricalconnections infrastructure use HVDC technology, in the as Mediterranean it is an economically dates more back advantageous to 1965, the SACOI connectionsolution that electrically compared to connectshigh voltage mainland alternating Italy, current Corsica, (HVAC) in and submarine Sardinia; links in longer 1987 than it became some the first multi-terminaltens of HVDCkm. The oldest scheme connecting with the electrical addition infrastructure on the in main the Mediterranean 200 MW/± dates200 back kV linkto 1965, of a 50 MW station in Corsica.the SACOI The connection original that mercury electrically arc connects valves mainland of the conversion Italy, Corsica, stations and Sardinia; were replaced in 1987 it in 1992 by became the first multi‐terminal HVDC scheme with the addition on the main 200 MW/± 200 kV link thyristor valves;of a 50 MW at the station same in time Corsica. the The conversion original mercury stations arc were valves increased of the conversion to 300 MW.stations were The oldestreplaced submarine in 1992 by thyristor HVAC valves; connection at the same in the time Mediterranean the conversion stations Sea is, were instead, increased comprised to 300 of the line connectingMW. Morocco-Spain (2 × 700 MVA/400 kV), commissioned in 1997 and 2006. The mostThe modern oldest submarine connections, HVAC connection also in in the the Mediterranean,Mediterranean Sea is, have instead, used comprised HVDC of the technology: line connecting Morocco‐Spain (2 × 700 MVA/400 kV), commissioned in 1997 and 2006. ± GRITA betweenThe most Italy modern and Greece connections, (500 also MW/ in the Mediterranean,400 kV) commissioned have used HVDC in technology: 2001, the SAPEIGRITA between mainlandbetween Italy and Italy Sardinia and Greece (2 (500× 500 MW/± MW/ 400 kV)± 500 commissioned kV) commissioned in 2001, the SAPEI in 2009 between and 2011mainland and Romulo between mainlandItaly and Sardinia Spain and (2 × the500 islandMW/± 500 of MallorcakV) commissioned (400 MW/ in 2009± 250 and kV) 2011 commissioned and Romulo between in 2011 [23,24]. Figure1 showsmainland the Spain interconnected and the island networks of Mallorca in (400 2017 MW/± [6 ].250 kV) commissioned in 2011 [23,24]. Figure 1 shows the interconnected networks in 2017 [6].

Figure 1. Interconnected networks in 2017 [6]. The red circles show the interconnections under Figure 1. Interconnectedinvestigation. networks in 2017 [6]. The red circles show the interconnections under investigation.

The newThe line new of connection line of connection with with Malta Malta consists consists of of a a220 220 kV kV HVAC HVAC submarine submarine cable which cable stands which stands between thebetween electrical the electrical station ofstation Marina of Marina di Ragusa, di Ragusa, in Sicily, in Sicily, and and Maghtab, Maghtab, in in Malta. Malta. ThisThis new electrical electrical infrastructure (Figure 2) significantly improves the stability and reliability of the island’s infrastructure (Figure2) significantly improves the stability and reliability of the island’s electricity system, preventing, among other things, the use of the two existing thermoelectric power plants that are very polluting. The electric line begins in the 220 kV electricity station in Ragusa. The Energies 2018, 11, 1415 4 of 14 Energies 2018, 11, x 4 of 14

firstEnergies partelectricity consists 2018, 11system,, x of an preventing, underground among cable other that things, extends the use for of 19 the km, two reaching existing thermoelectric Marina di Ragusa power4 of 14 (RG), whereplants the submarinethat are very cable polluting. runs The for electric a length line of begins about in 98the km.220 kV The electricity Maltese station end ofin Ragusa. the line The reaches the 220electricityfirst kV/133 part system,consists kV Maghtab preventing,of an underground station among [25 othercable]. In things,that the extends near the use future for of 19 the another km, two reaching existing HVAC Marina thermoelectric submarine di Ragusa cablepower (RG), is also plantswhere that the aresubmarine very polluting. cable runs The for electric a length line of begins about in 98 the km. 220 The kV Maltese electricity end station of the inline Ragusa. reaches The the being planned between Sicily and Malta, thus creating a double interconnection circuit. The new first220 partkV/133 consists kV Maghtab of an underground station [25]. cableIn the that near extends future anotherfor 19 km, HVAC reaching submarine Marina cable di Ragusa is also (RG), being transmissiblewhereplanned the submarinebetween power willSicily cable be andruns 400 MWMalta,for a length [26 thus]. In ofcreating additionabout 98 a km. todouble the The above, Malteseinterconnection the end scenario of the circuit. line in reaches the The near newthe future also220 providestransmissible kV/133 kV for powerMaghtab two other will station be links: 400 [25]. MW one In [26]. the for In near Tunisia addition future (Figure to another the above,3 )HVAC and the the scenariosubmarine other in for thecable Libya. near is also future The being also first is alreadyplannedprovides contained between for two in other aSicily development links: and oneMalta, for plan, Tunisiathus while creating (Figure the seconda3) doubleand the is interconnection stillother under for Libya. examination Thecircuit. first The is and already new analysis. Thetransmissible submarinecontained in cable power a development between will be 400 Tunisia plan, MW [26].while and In Italy theaddition second through to theis still Sicilyabove, under is the a scenarioexamination 200 km in long the and HVDCnear analysis. future (400 also The kV) link withprovidessubmarine a transport for cable two capacity otherbetween links: of Tunisia 1000 one MW;for and Tunisia Italy the Sicilianthrough (Figure Sicily extreme3) and is the a 200 of other the km for connectionlong Libya. HVDC The (400 will first kV) be is link connectedalready with to the electricalcontaineda transport stationin capacitya development of Partanna of 1000 plan,MW; (TP). whilethe The Sicilian the link second betweenextreme is stillof Libya the under connection and examination Sicily will is a be HVDCand connected analysis. submarine to The the link (500submarine kV)electrical with station cable a length between of Partanna of 550 Tunisia km, (TP). and with The Italy link a transport through between Sicily Libya capacity is and a 200 ofSicily km 1000 longis a MW; HVDC HVDC the submarine (400 electric kV) link stationlink with (500 is the onea locatedkV) transport with in a capacity Chiaramontelength of of 550 1000 km, Gulfi MW; with (RG). the a transportSicilian In the extreme remaindercapacity of of the of1000 connection this MW; work, the willelectric due be to connectedstation the delicate is theto theone political electricallocated in station Chiaramonte of Partanna Gulfi (TP). (RG). The In thelink remainder between Libya of this and work, Sicily due is to a theHVDC delicate submarine political link moment (500 moment experienced by the Libyan country, the authors consider the realization of this link (Libya) to kV)experienced with a length by the of Libyan550 km, country, with a transportthe authors capacity consider of 1000the realizationMW; the electric of this stationlink (Libya) is the toone be be unlikelylocatedunlikely in and, and,Chiaramonte therefore, therefore, Gulfi willwill (RG). not be In considered considered the remainder in in the of the loadthis load-flow work,‐flow studies.due studies. to the Table delicate Table 1 shows1 politicalshows the main the moment main data data of theexperiencedof new the new connections connectionsby the Libyan [27 [27].]. country, the authors consider the realization of this link (Libya) to be unlikely and, therefore, will not be considered in the load‐flow studies. Table 1 shows the main data of the new connections [27].

Figure 2. Sicily–Malta electrical connection (operating) [28]. Maghtab station is indicated by the red circle. Figure 2. Sicily–Malta electrical connection (operating) [28]. Maghtab station is indicated by the red circle. Figure 2. Sicily–Malta electrical connection (operating) [28]. Maghtab station is indicated by the red circle.

Figure 3. Sicily–Tunisia cable planned route [29].

FigureFigure 3.3. Sicily–Tunisia cable cable planned planned route route [29]. [29 ].

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Table 1. Interconnections data.

From To Cable V (kV) Capacity (MW) Submarine Length (km) Sicily Italy HVAC 400 3000 38 Sicily Malta HVAC 220 400 98 Sicily Tunisia HVDC 400 1000 194 Sicily Libya HVDC 500 1000 550

New Connection: Sicily–Italy The new “Sorgente-Rizziconi” power line, which connects Sicily to Calabria, represents a fundamental energy infrastructure for the national electricity system but, at the same time, will play a crucial role in European and Mediterranean terms, for a network at the cutting edge of technology and ever smarter, even from an environmental point of view, thanks to the full integration of renewable energy sources. The Energy Union is a topical issue at the center of the debate at the continental level: a priority project for the unification of the European electricity markets, which, once completed, will guarantee citizens and businesses greater electrical safety and a lower cost of electricity. The “Sorgente Rizziconi” project benefited from the European Union’s financial support under the European Energy Program for Recovery Program (EEPR). Together with the other electricity interconnections that Terna (the Italian transmission system operator) is carrying out, including those with Montenegro (which represents the first electric bridge with the Balkans) and France (another unique project in the world for innovation and technology), and in anticipation of other borders with foreign countries (including Tunisia), the new “Sorgente-Rizziconi” power line is a further step in the strategy of making Italy a real electricity hub at the European and Mediterranean levels for the transmission of electricity. This is an ideal platform—also given the peculiar geographic conformation—to connect North Africa and the south bank with each other of the Mediterranean basin with Central and Northern Europe. The goal of cross-border electricity interconnections, priority structures in European energy policy, is to provide greater security for the national and international electricity system, diversify the fuel mix, reduce dependence on a small number of energy-supplying countries, and decrease costs for businesses and citizens, as well as fully exploiting, by integrating them into the network, the production of energy from renewable sources, which can thus be transported from wind and photovoltaic parks to consumption centers. Terna is already committed to the integration of production from renewable sources into the electricity grid, a fundamental step to reach the targets set by the Paris agreement on emissions, renewables and energy efficiency. The theme of climate change imposes a change, as well as a stimulus, to achieve sustainable growth in the long term. A fully-interconnected European electricity grid with more cross-border interconnections, greater storage potential and smart grids to manage demand and ensure a secure supply in a system with higher shares of variable renewable energy is precisely the goal of the Energy Union. To achieve this, an ambitious goal has been set: 10% interconnection by 2020, a target measured as the ratio between the interconnection capacity on interconnections and the electricity production capacity installed in the member states. Italy currently has a level of interconnection of around 8%. In implementation of the European objectives, Terna’s commitment is to integrate the European electricity market, with the development of interconnections and the launch of “market coupling”, and the strengthening of the network in Italy and the identification of selective investments. The new connection is long 105 km (38 km in submarine cable), Figure4, and it is comprised of six 400 kV submarine cables that will triple the connections between Sicily and the continent, with a new capacity up to 1100 MW; the investment has reached over 700 million euro. The submarine part consists of a total of six cables each 38 km long, under the water of the Tyrrhenian Sea, at a maximum depth of 376 m. The submarine cables are insulated in fluid oil, the most reliable technology for this type of connection, and are kept at constant pressure under continuous control by means of compensation stations. They were also protected from external agents for the whole of the track Energies 2018, 11, 1415 6 of 14 throughEnergies 2018 techniques, 11, x made with specific machines designed for the pressure drilling of rocky or sandy6 of 14 sediments in order to dig the trench that now houses the submarine cable. The distance between the cables (up to about 250 m) is such as to guarantee reliable maintenance of of the the cables cables in in the the future. future. From Scilla, in Calabria, there is a doubledouble cablecable connectionconnection that, through a dedicateddedicated underground work, dugdug into into the the mountain mountain of of Favazzina, Favazzina, and and it arrives it arrives at the at beach. the beach. This work This consistswork consists of the longest of the verticallongest wellvertical of itswell kind, of its 300 kind, m deep 300 withm deep a diameter with a ofdiameter 7 m, which, of 7 m, due which, to the due difficult to the geological difficult conditions,geological conditions, has been dug has from been top dug to from bottom, top whileto bottom, generally while proceeding generally proceeding in the opposite in the direction opposite to similardirection depth. to similar The power depth. stations The power of the stations “Sorgente-Rizziconi” of the “Sorgente power‐Rizziconi” line are power four: line two are on four: the Sicily, two Sorgente,on the Sicily, and Sorgente, Villafranca and Tirrena Villafranca sides, andTirrena two sides, on the and Calabria, two on Scilla, the Calabria, and Rizziconi Scilla, sides. and Rizziconi The first threesides. were The first built three inside were a building built inside with SF6 a building technology with designed SF6 technology to facilitate designed rapid installationto facilitate and rapid to reduceinstallation the volume and to reduce of occupation the volume on the of ground, occupation and on able the to ground, withstand and voltage able to values withstand up to voltage 550 kV thatvalues are up generated to 550 kV due that to overvoltagesare generated (electrical due to overvoltages transients), characteristic(electrical transients), of such a characteristic long submarine of link.such a The long station submarine of Sorgente, link. The in station particular, of Sorgente, is a record in alsoparticular, because is thea record armor also is placedbecause outside the armor the buildingis placed and,outside to ensure the building the necessary and, to ensure protection the necessary and allow protection easier maintenance, and allow haseasier been maintenance, designed a self-propelledhas been designed cover, a self composed‐propelled from cover, several composed easily removable from several sections. easily Even removable the Scilla sections. station Even reflects the technologicalScilla station reflects excellence technological thanks to excellence the uniqueness thanks of to the the armored uniqueness vehicle of the built armored inside vehicle it, which built is currentlyinside it, which the largest is currently in Europe the of largest its kind. in OtherEurope important of its kind. Italian Other investments important in Italian the grid investments with regard in the 2007–2013grid with regard Interregional the 2007–2013 Operative Interregional Program (POI Operative Energia), Program with a financial (POI Energia), allocation with of 1071 a financial billion euro,allocation financed of 1071 1.887 billion projects euro, in Italy financed of public 1.887 administrations projects in Italy and of companies public administrations of the Convergence and Regionscompanies (Calabria, of the Campania,Convergence Puglia, Regions Sicily) (Calabria, (Figure5 ).Campania, The investments Puglia, made Sicily) with (Figure the resources 5). The ofinvestments the Program made concern with the energy resources efficiency of the and Program the production concern energy of energy efficiency from and renewable the production sources, investmentof energy from support, renewable upgrading sources, of the investment network, carrying support, out upgrading studies, andof the assessing network, the carrying potential out for energystudies, development. and assessing the potential for energy development.

Figure 4. Figure 4. Sorgente–Rizziconi cable route [[30].30].

Energies 2018, 11, 1415 7 of 14

Energies 2018, 11, x 7 of 14

Figure 5. POI Energia 2007–2013: Convergence regions in Italy [31]. Figure 5. POI Energia 2007–2013: Convergence regions in Italy [31]. 3. Tunisian Electro‐Energetic Context 3. Tunisian Electro-Energetic Context Tunisia, like most of the countries of the Middle East and North Africa, has an energy mix based Tunisia,almost exclusively like most on of traditional the countries fossil of sources; the Middle the percentage East and of North installed Africa, power has supplied an energy by mix basedrenewable almost exclusively sources is only on a traditional few percentage fossil points sources; (Figure the 6) percentage [32]. In the last of installedtwenty years, power this suppliedcountry by renewablehas been sources characterized is only by a few a continuous percentage growth points in consumption (Figure6)[ 32 (Figure]. In the 7), so last much twenty so that, years, as a this natural country has beengas exporter, characterized starting byfrom a 2011 continuous it became growth an importer. in consumption The energy dependence (Figure7 ),from so foreign much socountries that, as a naturalis about gas exporter, 30%, but it starting is believed from that 2011 in the it becamefuture the an progressive importer. increase The energy in consumption dependence will from increase foreign countriesthe deficit is about between 30%, butproduction it is believed and total that demand. in the future In particular, the progressive the Tunisian increase energy in system consumption is will increasecharacterized the deficitby a strong between dependence production on natural and total gas, demand.which Tunisia In particular, receives through the Tunisian the Trans energy‐ Mediterranean methane pipeline from Algeria to Italy. In 2013, oil consumption grew by 2% compared system is characterized by a strong dependence on natural gas, which Tunisia receives through the to the previous year, as did the consumption of natural gas (+7.4%). The contribution from biofuels has Trans-Mediterranean methane pipeline from Algeria to Italy. In 2013, oil consumption grew by 2% also increased slightly. Renewable sources cover a negligible fraction of the primary needs, while the compareddemand to thefor previouscoal has been year, absent as did since the consumption 1999. Under the of naturalpressure gas of (+7.4%).economic The development contribution and from biofuelsimprovement has also increased of the standard slightly. of living, Renewable the demand sources for coverelectricity a negligible has also increased fraction rapidly of the primary (about 5% needs, whileat the year, demand reaching for a value coal hasof 15.6 been TWh absent in 2013, since about 1999. 1430 Under kWh per the inhabitant, pressure settling of economic in 2012 developmentat 22% of and improvementthe total final energy of the standardconsumption, of living, and 44.5% the demand of the total for primary electricity energy has alsoconsumption. increased In rapidly 2015 (the (about 5% atlast year, available reaching statistics a value on the of IEA 15.6 website), TWh in the 2013, installed about capacity 1430 kWh is about per 5 inhabitant, GW, of which settling 312 MW in 2012 at 22%related of the to total plants final powered energy by consumption, renewable sources and 44.5%(245 MW of thewind, total 62 primaryMW hydroelectric, energy consumption. 15 MW In 2015photovoltaic). (the last available Due to its statistics geographical on the position, IEA website), Tunisia theholds installed considerable capacity wind is and about solar 5 GW,potential, of which 312 MW related to plants powered by renewable sources (245 MW wind, 62 MW hydroelectric, 15 MW photovoltaic). Due to its geographical position, Tunisia holds considerable wind and solar potential, Energies 2018, 11, 1415 8 of 14 whichEnergiesEnergies is not 2018 2018 currently, ,11 11, ,x x adequately exploited; the country enjoys intense direct solar radiation,88 of equalof 14 14 to 1800 kWh/m2 year in the north and 2600 kWh/m2 year in the south. There are also numerous sites whichwhich is is not not currently currently adequately adequately exploited; exploited; the the country country enjoys enjoys intense intense direct direct solar solar radiation, radiation, equal equal to to suitable18001800 for kWh/mkWh/m the construction22 yearyear inin thethe north ofnorth wind andand farms, 26002600 kWh/mkWh/m and there22 yearyear is inin significant thethe south.south. There potentialThere areare also linkedalso numerousnumerous to biomass sitessites and geothermalsuitablesuitable sources. forfor thethe constructionconstruction By virtue of ofof these windwind considerations farms,farms, andand therethere (dependence isis significantsignificant on potentialpotential foreign linkedlinked countries toto biomassbiomass and enormous andand potentialgeothermalgeothermal of renewable sources. sources. By resources,By virtue virtue of of these solarthese considerations considerations in particular), (dependence (dependence the Tunisian on on foreign foreign government, countries countries starting and and enormous enormous from 2009, has givenpotentialpotential a strong of of renewable renewable impetus resources, resources, to the development solar solar in in particular), particular), of renewable the the Tunisian Tunisian energy government, government, sources, starting starting tracing from from a 2009, road-map2009, has has to self-productiongivengiven aa strongstrong development. impetusimpetus toto thethe From developmentdevelopment these sources, ofof renewablerenewable and articulating energyenergy sources,sources, a development tracingtracing aa roadroad‐‐map planmap toto called selfself‐‐ the “Tunisianproductionproduction Solar development. development. Plan”, strongly From From oriented these these sources, sources, to the and and development articulating articulating a a development development of the solar plan plan source, called called a the the resource, “Tunisian “Tunisian today, Solar Plan”, strongly oriented to the development of the solar source, a resource, today, almost not used almostSolar not Plan”, used strongly at all. Furthermore, oriented to the thedevelopment Tunisian of parliament the solar source, recently a resource, launched today, a seriesalmost ofnot initiatives used atat all. all. Furthermore, Furthermore, the the Tunisian Tunisian parliament parliament recently recently launched launched a a series series of of initiatives initiatives aimed aimed at at promoting promoting aimed at promoting energy efficiency and the use of renewable sources throughout the country. energyenergy efficiency efficiency and and thethe use use of of renewable renewable sources sources throughout throughout thethe country. country. TheThe targettarget is is to to be be ableable to to The target is to be able to cover 30% of the electricity demand by renewables by 2030, thus reducing covercover 30% 30% of of the the electricity electricity demand demand by by renewables renewables by by 2030, 2030, thus thus reducing reducing the the use use of of traditional traditional sources sources the useandand of increasing increasing traditional its its energy energy sources autonomy. autonomy. and increasing Even Even more more its ambitious ambitious energy autonomy.objectives objectives envisage envisage Even even more even greater greater ambitious installations installations objectives envisageofof renewablerenewable even greater sourcessources installations (especially(especially of PV)PV) renewable inin TunisiaTunisia sources andand inin (especiallyNorthNorth AfricaAfrica PV) inin general. ingeneral. Tunisia TheThe and authors,authors, in North inin thethe Africa in general.continuationcontinuation The authors, of of this this work, work, in the will will continuation hypothesize hypothesize some ofsome this energy energy work, scenarios scenarios will hypothesize that that will will be be simulated somesimulated energy on on the the scenarios network network that will bemodel.model. simulated on the network model.

FigureFigureFigure 6. Tunisia 6. 6. Tunisia Tunisia Energy Energy Energy production—(IEA) production—(IEA) production—(IEA) [32]. [[32].32]. *: *: *:Share Share Share of of TPES TPES of TPES (Total (Total (Total Primary Primary Primary Energy Energy Energy Supply) Supply) Supply) excludesexcludesexcludes electricity electricity electricity trade. trade. trade.

FigureFigureFigure 7. 7. Electricity7. Electricity Electricity generation generation generation in in Tunisia Tunisia (IEA) (IEA) (IEA) [32]. [32]. [32 ].

Energies 2018, 11, 1415 9 of 14

4. Simulation of Near Future Scenario In order to simulate future scenarios (2020 and 2025), the authors developed a network model in Neplan® [33], representative of the transmission network in Sicily considering the new interconnections with Italy, Malta, and Tunisia, as reported in Figure8. The proposed model is made by:

• 336 nodes; • 346 lines; • 90 transformers; • 66 synchronous machines; and • 47 RES production systems. Energies 2018, 11, x 10 of 14

Figure 8. Network model implemented in Neplan. Figure 8. Network model implemented in Neplan. 5. Results The 220 kV lines are indicated in green, the 400 kV lines are indicated in red, and the 150 kV lines are indicatedThis paragraph in purple. shows The the blueresults arrows of the indicate simulations the windpreviously power described. plants. TheThe objectivegoal of the of the presentanalysis study of is the to hypothesizeload flow is to some verify, scenarios in both ofscenarios, operation with of N the‐1 nearcriterion, future the (2020–2025) lack of violations in which in the terms of transits and voltage values on the Sicilian electrical system. In the 2020 scenario Sicily must energy flows will be directed from Europe to Malta and to the North-African continent. The analysis produce 679 MW (minimum value) from traditional generation to avoid violations; in the 2025 of the load flow is, therefore, aimed, in both cases, on the verification, with N-1 criterion, of the lack scenario the minimum value is 653 MW. In the first scenario (2020), a single connection with Malta is of violationsconsidered in with terms a flow of transits of 150 MW, and a voltage connection values to Tunisia on the with Sicilian a flow electrical of 800 MW, system. Sicilian With demand iterative simulations,of 2300 MW, the minimum and a RES productiongeneration of value 2000 MW. has beenIn the verified second scenario from traditional (2025) a double sources connection in Sicily that doeswith not give Malta rise is toconsidered problems with of operation. a flow of 300 The MW, N-1 a Criterion connection is ato criterion Tunisia with where a flow the Grid, of 800 following MW, a credibleSicilian contingency demand of event 2530 MW, (e.g., and loss a of RES a single-circuit generation of 2150 interconnection MW. Tables 2 or and loss 3 report of a single the results transformer), for is requiredthe “inner” to be generation, capable to operatei.e., Sicilian within generation a certain (traditional minimum and/or performance. pumped storage), needed for Theavoiding reinforcement violations in of the system. infrastructure The authors connecting also investigated Sicily to Northern the voltage Italy profiles and continentalof buses in the Europe will besimulated able to providescenarios: different Table 4 and operating Figure conditions9 (for 2020 ofscenario), the Sicilian Table electricity 5 and Figure system, 10 (for with the particular2025 scenario) report the buses that present a value of voltage less than 95% of the rated value. Note that reference to the import-export of power. The new HVDC connection of North Africa with Tunisia will for high‐voltage systems the violation is recorded for variations over 10%. Exceeding the 5% allow the dispatching of energy from Europe to the North African continent, instead, through the new threshold is only an indicator of attention. It should be noted that, in the 2020 scenario, all the nodes connectionthat are with less than the 95% island (but of very Malta close (second to this value) scenario, are all 2025), the nodes Sicily near will the exportconnection power with towards Tunisia. this, In that area a synchronous compensator is installed which, if necessary, could be used to regulate the voltage. In the 2025 scenario, the number of nodes below 95% grows and now, besides those close to Tunisia, present the lowest values (90–91%) compares to those close to the connection with Malta which, in this scenario, has doubled the power transit (300 MW). Additionally, in this case, there are many possibilities for voltage regulation in that area. The second scenario (2025) also considers the completion of some reinforcement works on the system, such as the installation of HTLS (high temperature low sag) conductors on some high‐voltage lines, and the use of DTR [34]. As demonstrated in [25] these new interconnections allow an important improvement in the integration and dispatching of the power generated by RES of the Sicilian territory, a better operation

Energies 2018, 11, 1415 10 of 14 with a maximum limit of 400 MW. All data concerning the consumption of electricity, the diffusion of renewable sources, and the production from traditional units must be subject to a reliable forecast for a near future scenario [25]. For the studies concerning the RES impacts on the Sicilian electrical system, authors used data correctly evaluated by the statistical office of the transmission system operator through some probabilistic analysis. A growth rate is assumed for the demand for electricity equal to 2–2.5% for the next years. A reduction in the value of electricity consumption should also be considered, thanks to the simultaneous increase in production from RES, in particular from PV plants directly connected to the MV network. Therefore, considering these two contrasting trends and an average electricity demand of 2100 MW in the last year, the simulations presented in this paper were performed considering a power consumption of 2300 MW (2020 scenario) and 2530 MW (2025 scenario). The 2020 scenario foresees a wind generation of 3200 MW, but at the same time a reduction factor is assumed that takes into account the non-simultaneous generation throughout Sicily; therefore, in the 2020 scenario, approximately 2000 MW are considered coming from wind farms; instead, for the 2025 scenario, the authors foresee a wind generation of 3500 MW (a saturation of the sector is hypothetical), but, at the same time, a reduction factor is assumed that takes into account the non-simultaneous generation throughout Sicily; therefore, in the 2025 scenario, approximately 2150 MW are considered coming from wind farms. Not having enough information on the exact location of the new plants to be installed in near future, it is assumed that the wind farms today installed in the network and implemented on the Neplan model will produce all the aforementioned power. However, it is believed that this hypothesis is correct as it is plausible that the future expansion of wind farms will affect the windy areas in which wind turbines are currently installed and where investors feel more cautious thanks to the existence of complete anemometric and economic studies.

5. Results This paragraph shows the results of the simulations previously described. The goal of the analysis of the load flow is to verify, in both scenarios, with N-1 criterion, the lack of violations in terms of transits and voltage values on the Sicilian electrical system. In the 2020 scenario Sicily must produce 679 MW (minimum value) from traditional generation to avoid violations; in the 2025 scenario the minimum value is 653 MW. In the first scenario (2020), a single connection with Malta is considered with a flow of 150 MW, a connection to Tunisia with a flow of 800 MW, Sicilian demand of 2300 MW, and a RES generation of 2000 MW. In the second scenario (2025) a double connection with Malta is considered with a flow of 300 MW, a connection to Tunisia with a flow of 800 MW, Sicilian demand of 2530 MW, and a RES generation of 2150 MW. Tables2 and3 report the results for the “inner” generation, i.e., Sicilian generation (traditional and/or pumped storage), needed for avoiding violations in the system. The authors also investigated the voltage profiles of buses in the simulated scenarios: Table4 and Figure9 (for 2020 scenario), Table5 and Figure 10 (for the 2025 scenario) report the buses that present a value of voltage less than 95% of the rated value. Note that for high-voltage systems the violation is recorded for variations over 10%. Exceeding the 5% threshold is only an indicator of attention. It should be noted that, in the 2020 scenario, all the nodes that are less than 95% (but very close to this value) are all the nodes near the connection with Tunisia. In that area a synchronous compensator is installed which, if necessary, could be used to regulate the voltage. In the 2025 scenario, the number of nodes below 95% grows and now, besides those close to Tunisia, present the lowest values (90–91%) compares to those close to the connection with Malta which, in this scenario, has doubled the power transit (300 MW). Additionally, in this case, there are many possibilities for voltage regulation in that area. The second scenario (2025) also considers the completion of some reinforcement works on the system, such as the installation of HTLS (high temperature low sag) conductors on some high-voltage lines, and the use of DTR [34]. As demonstrated in [25] these new interconnections allow an important improvement in the integration and dispatching of the power generated by RES of the Sicilian territory, a better operation Energies 2018, 11, 1415 11 of 14 of traditional Sicilian generation units, a lower electricity zonal prices and a significant reduction in emissions from obsolete fuel oil thermal units located in Malta.

Table 2. The 2020 scenario.

Data Operational Conditions [MW] Import from Italy 600 Sicilian Traditional generation + pumped storage 679 Sicilian RES generation 2000 Sicilian Demand 2300 Export to Malta 150 Export to Tunisia 800

Table 3. The 2025 scenario.

Data Operational Conditions [MW] Import from Italy 850 Sicilian Traditional generation + pumped storage 653 Sicilian RES generation 2150 Sicilian Demand 2530 Export to Malta 300 Export to Tunisia 800

Table 4. Voltage profile (under 95%) in the 202 scenario.

Bus Number Bus Name V% 1 Marsala 94.96 2 Matarocco 94.85 3 Fulgatore 2 94.81 4 Trapani CP 94.68 5 Ospedaletto 94.70

Table 5. Voltage profile (under 95%) in the 2025 scenario.

Bus Number Bus Name V% 1 MELILLI 2 94.93 2 S. Ninfa 94.9 3 Salemi 94.87 4 Chiaramonte Gulfi 2 94.71 5 Ribera 94.82 6 Ragusa 3 93.21 7 93.19 8 RAGUSA 2 93.21 9 Castiglione 94.65 10 Castroreale 94.99 11 Francavilla 94.8 12 Sciacca 94.76 13 Augusta C.LE 94.97 14 Siracusa Est 94.69 15 Siracusa 1 94.62 16 Siracusa Nord 94.75 17 Lentini 94.94 18 Giarre 94.57 19 Giardini 94.59 20 PARTANNA 2 94.99 21 Castelvetrano 94.9 22 Rosolini 91.33 23 Pozzallo 90.22 Energies 2018, 11, 1415 12 of 14 Energies 2018, 11, x 12 of 14 Energies 2018, 11, x 12 of 14 Scenario 2020

100% Scenario 2020

100%99%

98%99%

97%98%

96%97%

V % 95%96%

V % 94%95% Voltage profile Voltage profile 93%94%

92%93%

91%92%

90%91%

90% 0 1 2 3 4 5 6 0 1 2 Bus Number3 4 5 6 Bus Number Figure 9. Voltage profile (under 95%) in the 2020 scenario. Figure 9. Voltage profile (under 95%) in the 2020 scenario. Figure 9. Voltage profile (under 95%) in the 2020 scenario. Scenario 2025 96% Scenario 2025

96% 95%

95% 94%

94% 93%

V% 93%

V% 92% Voltage profile

92% Voltage profile 91%

91% 90%

90% 89% 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 89% Bus Number 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Bus Number Figure 10. Voltage profile (under 95%) in the 2025 scenario. Figure 10. Voltage profile (under 95%) in the 2025 scenario. Figure 10. Voltage profile (under 95%) in the 2025 scenario. 6. Conclusions 6. Conclusions 6. ConclusionsEverywhere worldwide there are innovative projects to connect large‐scale electrical systems and toEverywhere share electricity worldwide produced there fromare innovative renewable projects energy tosources connect (RES) large in‐ scalefar‐flung electrical regions. systems The Everywherepresentand to sharepaper worldwideelectricity presents theproduced there new areopportunities from innovative renewable deriving projects energy from to sources connect the interconnections (RES) large-scale in far‐flung electrical of the regions. European systems The and to shareandpresent electricityNorth paper African presents produced transmission the from new renewableopportunities systems. After energy deriving describing sources from (RES)thethese interconnections ininterconnections, far-flung regions. of the the European Theauthors present paperdevelopedand presents North a the Africannetwork new opportunities transmissionmodel using Neplansystems. deriving and After fromsimulate describing the two interconnections operational these interconnections, scenarios of the of European the the near authors future and North African(2020–2025)developed transmission a in network which systems. the model energy using After flows Neplan describing will beand directed simulate these from two interconnections, Europe operational to Malta scenarios and the to authors theof the North near developed African future a networkcontinent.(2020–2025) model The in using whichanalysis Neplan the of energy the and load flows simulate flow will verifies, be two directed operational with from N‐1 Europesafety scenarios criterion, to Malta of theandthe nearlackto the of future North violations African (2020–2025) in continent. The analysis of the load flow verifies, with N‐1 safety criterion, the lack of violations in in whichterms the of overload energy flows and voltage will be values directed on the from Sicilian Europe electrical to Malta system. and With to the iterative North simulations, African continent. the authorsterms of verifyoverload the andminimum voltage production values on thevalue Sicilian from electrical traditional system. sources With in iterativeSicily that simulations, does not give the The analysis of the load flow verifies, with N-1 safety criterion, the lack of violations in terms of riseauthors to problems verify the of minimum operation. production The results value obtained from showtraditional that these sources new in interconnectionsSicily that does notallow give a overload and voltage values on the Sicilian electrical system. With iterative simulations, the authors deeperrise to problemsintegration of of operation. renewable The sources results into obtained the Italian show system that and, these therefore, new interconnections lower electricity allow zonal a verifyprices.deeper the minimum Aintegration greater use production of ofrenewable renewable value sources energy from into sources the traditional Italian (RES) system will sources obviously and, in therefore, Sicily also produce that lower does electricity positive not give effects zonal rise to problemsonprices. CO of2 Aemissions operation. greater use into of The the renewable atmosphere results obtainedenergy as the sources RES show will (RES) that replace, will these inobviously particular new interconnections also in Maltaproduce and positive North allow Africa,effects a deeper integrationtraditionalon CO2 ofemissions renewable plants (ininto particular the sources atmosphere by into obsolete the as Italianthe fuel RES oil systemwill thermal replace, and, units). in therefore, particular The realization lowerin Malta of electricity theseand North connections zonal Africa, prices. A greaterwouldtraditional use make ofplants the renewable European (in particular energy and by the obsolete sourcesNorth African fuel (RES) oil thermalelectricity will obviously units). systems The alsorealizationsafer, produce more of efficient, these positive connections and effectsmore on would make the European and the North African electricity systems safer, more efficient, and more CO2 reliable.emissions Finally, into thegreater atmosphere harmonization as the of RES the cost will of replace, electricity in particularcould be achieved. in Malta The and presence North of Africa, traditionalthesereliable. plantsnew Finally, interconnections—Sicily—Italy, (in greater particular harmonization by obsolete of fuel the Sicily–Malta, oilcost thermal of electricity units).and couldSicily–Tunisia—according The be realization achieved. ofThe these presence connectionsto the of these new interconnections—Sicily—Italy, Sicily–Malta, and Sicily–Tunisia—according to the would make the European and the North African electricity systems safer, more efficient, and more reliable. Finally, greater harmonization of the cost of electricity could be achieved. The presence of these new interconnections—Sicily—Italy, Sicily–Malta, and Sicily–Tunisia—according to the authors, Energies 2018, 11, 1415 13 of 14 allows a decrease in the zonal price of electricity in this area, and will also permit a greater flexibility of the electricity market by a significant decrease in the HHI (Herfindahl-Hirschman index).

Author Contributions: Conceptualization: S.F.; Data curation: F.M., L.M., R.M., and G.Z.; Formal analysis: S.F., F.M., and L.M.; Investigation: F.M.; Methodology: S.F., M.G.I., F.M., L.M., and R.M.; Software: R.M. and G.Z.; Supervision: M.G.I. and F.M.; Validation: M.G.I., F.M., and G.Z.; Writing—original draft: F.M.; Writing—review and editing: F.M. Conflicts of Interest: The authors declare no conflict of interest.

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