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(1)AGH University of Science and Technology in Cracow Faculty of Management Department of Engineering Management. PhD thesis: MODEL OF ENERGETIC COOPERATION BETWEEN ELECTRICAL VEHICLES AND SOLAR OFFICE BUILDING. by: Magdalena Jurasz. Supervisor:. Prof. Jerzy Mikulik, PhD. Cracow, June 2020.

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(3) Abstract With an increase in urbanization becoming a global trend, rise in energy demand is observed worldwide. Cities are usually characterized by a very high population density and simultaneously very low self-sufficiency in terms of food, water and energy. At the same time, the ever increasing climate changes heavily affect the characteristics and the structure of the energy demand. These changes are noticeable on both a country and an individual consumer’s level. Actions are being undertaken to counteract the unavoidable consequences of rising air temperatures and see water levels. One of the key aspects which is envisioned as a solution enabling stopping the climate change is the transformation of the energy system to the one characterized by very low or almost zero CO2 emissions. The transformation also refers to the transportation sector, which should in the future be based entirely on electrical energy or its environmentally friendly alternative, like hydrogen. This dissertation is dedicated to the topic of the potential use of photovoltaic (PV) systems, operating as office buildings (OB) partial energy supply source, whilst the office building is also equipped with an electrical vehicle (EV) charging station. Such a station is a part of the OB infrastructure. The motivation to undertake such a topic is as follows: •. Office buildings have a particular load pattern, which is to a substantial extent driven by cooling demand. The number of office buildings across the globe is increasing and this trend can also be observed in Poland.. •. The cooling demand tends to match very well with the photovoltaics energy generation profile, as usually the days with high temperatures (what leads to a high cooling demand) are characterized by high irradiation values (usually greater energy yield from photovoltaics).. •. The office buildings due to a large glazed area of facades and substantial roof area have the potential to accommodate a certain capacity of photovoltaic installation that is worth considering and thereby contribute to covering the OB electrical load. Although an off-site PV station is a promising alternative.. •. Electrical vehicles are becoming an economically interesting option in cities, which aim at improving their air quality by reducing the number of conventional fuels powered cars entering the city. It can be expected that companies’ cars/fleets may become fully electric in the future.. 3.

(4) •. Companies residing in office buildings/office building owners may want to provide their employees/renters with additional benefits/services like EV charging stations.. Considering the above in this dissertation, a model of an energetic cooperation between EVs and OB with a PV system was developed. From the modelling point of view, five different models have been presented. Namely: •. A benchmark model, which aims at recreating the most commonly observed current situation, which is an office building, connected to the electricity grid without energy supply from PV system and EV charging load.. •. A modified model where the office building is simultaneously supplied in energy from the national grid and own PV installation. The exact location of the PV system is however outside the scope of the analysis.. •. A model where the office building has an EV charging station. However, it uses only the electricity from the national grid. Although, the energy flow is not enabled from the EV to the office building.. •. Similar to the above model but with an option to supply part of the load (both the office building and electrical vehicles) from a PV installation.. •. The final model, which is an improved version of the last model by allowing the energy flow from the electrical vehicles to the office building. Therefore, this model considers the opportunity of using EVs as mobile energy storage.. For the simulation and optimization purposes the models were implemented in MS Excel and Matlab software. To solve the linear optimization problem a freeware Open Solver software was used with an academic license for the Gurobi linear solver, and Matlab for linear programming (optimproblem – Matlab 2019a). The models were provided with historical data regarding electrical load, irradiation and temperature. The precise location of the office building cannot be disclosed due to the confidentiality policy although it can be mentioned that the building is located in Cracow (Poland). Based on the simulations, the following results/conclusions were drawn: •. Electricity tariff C21 is the cheapest option for office buildings without PV installation.. •. Adding PV system reduced the total electricity cost by roughly 0.06 PLN/kWh (0.015 Euro/kWh assuming 1 Euro = 4 PLN) and ensures higher resilience in case of expected energy prices increase in the future. 4.

(5) •. PV system significantly modifies the office building energy demand pattern. There is a good daily match between generation and demand. On a weekly basis, an oversized PV system may produce more energy than consumed by the building.. •. From the national power system perspective, the PV system has potential to shave the observed peak load – which is a huge benefit for the power system, where the peak load is observed during hot days when simultaneously the efficiency of conventional generators is lower.. •. Charging a fleet of 50 EVs naturally increases the total cost of electricity in the office building (considering that the charging station is its internal part). However, this increase is different depending on the energy tariff: from 2.9% for C21 to 3.0% for C22b.. •. The charging strategy can and should be optimized in such a manner that its negative impact on the residual (if PV system is present) load is minimized. A simplified charging strategy (charging immediately upon arrival) results in an increase in the observed peak demand.. •. The optimization of the charging strategy focused on minimizing the total electricity cost undoubtedly increases the overall variability of the office building (with PV and EV) load profile.. •. The potential future increase in electricity prices significantly rises the role of EVs as a mobile energy storage in the case of office buildings.. •. The future implementation of the proposed concept will clearly require a powerful informatics system which will enable an information exchange between weather forecasts, PV yield forecasts, electricity prices forecasts (if tariffs are not present), building electrical load forecast, expected duration of EV trips and resulting electricity consumption along with expected time of arrival and later departure.. 5.

(6) Extended abstract in Polish Na świecie obserwuje się rosnące zapotrzebowanie na energię. Energię zarówno elektryczną, cieplną jak i tę „zmagazynowaną” w paliwach wykorzystywanych na potrzeby transportu. Rozwój gospodarki (aczkolwiek z coraz silniejszymi trendami związanymi z szeroko rozumianym rozwojem zrównoważonym) pociąga za sobą rosnącą presję działalności człowieka na środowisko naturalne. Poprzez fakt, iż cywilizacja jest fragmentem całego ekosystemu planety Ziemia coraz częściej dostrzegamy, że każda nasza akcja pociąga za sobą reakcję. Znamiennym tego przykładem są zmiany klimatu. Zmiany, które chociaż obserwowane od milionów lat, to na przestrzeni ostatnich dwóch wieków uznaje się za będące w znacznej mierze efektem antropogenicznych emisji dwutlenku węgla do atmosfery i towarzyszącym im efektem cieplarnianym. Efekt ten prowadzi do wzrostu temperatur powietrza oraz coraz większej liczby ekstremalnych zjawisk pogodowych. Globalny konsensus co do przyczyn zmian klimatu jest osiągany ze zmienną skutecznością, którego analiza wykracza coraz częściej poza ramy debaty nauk ścisłych. Należy jednak uznać, że chociaż zgoda co do przyczyn globalnego ocieplenia klimatu pozostaje nieosiągnięta, to jego skutki obserwujemy już dzisiaj. Coraz częściej raportuje się rosnącą liczbę gwałtownych zjawisk pogodowych dotyczących pożarów, tornad, huraganów, powodzi czy też susz. Jak przekłada się to na funkcjonowanie gospodarki globalnej? Zmienność warunków, w których funkcjonuje dany system, poza granice dla których ten system został zaprojektowany powoduje, iż ciężko jest przewidzieć jego zachowanie/reakcję. Może się zdarzyć, iż system nie będzie w stanie funkcjonować lub osiągnie tylko część swojej oczekiwanej wydajności. Poprzez system możemy rozumieć tutaj fragmenty gospodarki realizujące z góry założone funkcje. Na przykład system energetyczny (czyli układ elektrowni, sieci przesyłowych, magazynów energii, odbiorców oraz różnych rozwiązań technicznych) został tak zaprojektowany, by zaspakajać w każdej chwili zapotrzebowanie odbiorców na energię elektryczną. Jeśli w środowisku funkcjonowania systemu wystąpią zjawiska ekstremalne, takie na które system nie został przygotowany (np. ze względu na zbyt duże koszty utrzymywania niezawodności) dojść może do sytuacji, w której nastąpi przerwa w dostawie energii elektrycznej.. 6.

(7) Jednym z rozwiązań, które ma przeciwdziałać skutkom globalnego ocieplenia klimatu jest rozwój odnawialnych źródeł energii. Ponieważ cechują się one niewielką lub bliską zeru emisyjnością CO2 docelowo mogą pozwolić na zatrzymanie postępującego wzrostu temperatur. Jednakże, ich rozwój w ramach wielu systemów energetycznych nie jest sprawą oczywistą. Biorąc pod uwagę powyższe akapity należy podkreślić, że prezentowana rozprawa doktorska tematycznie dotyczy trzech kluczowych sektorów gospodarki. Mianowicie energetyki, transportu oraz budownictwa. Ze względu na rozmiar tych sektorów ich dogłębna analiza w pojedynczej rozprawie doktorskiej nie jest możliwa. Z tego też względu sektory te w rozprawie reprezentowane są poprzez odpowiednio fotowoltaikę (sektor energetyki), samochody elektryczne (transport) oraz budynki biurowe (budownictwo). W rozprawie analizę przeprowadzono z perspektywy polskiej. Wybór elementów poszczególnych sektorów jest podyktowany faktem, iż: •. Budownictwo odgrywa znaczącą rolę w krajowym (co jest również trendem światowym) kształtowaniu się profilu oraz finalnego zapotrzebowania na energię elektryczną oraz cieplną.. •. W polskich miastach obserwuje się dynamiczny rozwój budownictwa biurowego, co bezpośrednio przekłada się na profil lokalnego oraz krajowego zapotrzebowania na energię elektryczną.. •. W ramach funkcjonowania polskiego systemu energetycznego w sposób dynamiczny wzrasta rola energetyki odnawialnej w postaci systemów fotowoltaicznych. Sytuacja ta ma miejsce na skutek rosnących cen energii elektrycznej oraz krajowych programów wspierających rozwój takich systemów pozyskiwania energii.. •. Obserwowany jest powolny wzrost liczby samochodów elektrycznych w ramach krajowej floty samochodowej. Należy jednak podkreślić, iż obecnie jest to w skali globalnej niewiele znaczący ułamek. Jednak lokalnie można spodziewać się znacznego wpływu ładowania samochodów elektrycznych na funkcjonowanie systemu energetycznego.. Wspólna płaszczyzna, na której znajdują się te trzy sektory gospodarki to budynek biurowy wyposażony we własną instalację fotowoltaiczną oraz stację ładowania samochodów elektrycznych będących częścią floty samochodów najemcy budynku biurowego. W rozprawie budynek biurowy „generuje” zapotrzebowanie na energię elektryczną (zużycie wynika z realizowanych w budynku procesów). Zapotrzebowanie to cechuje się swoistym dobowym, 7.

(8) tygodniowym oraz rocznym profilem. Instalacja fotowoltaiczna może pokryć część tego zapotrzebowania, a uzysk jej energii w sposób korzystny koreluje z zapotrzebowaniem na energię elektryczną w dni o wysokiej temperaturze (gdy konieczne jest wykorzystanie klimatyzacji). Budynek należy, bądź jest wynajmowany przez organizację, której część pracowników posiada samochody elektryczne (lub jest to flota firmowa). Samochody te po przyjeździe pracowników do pracy są podłączane do stacji ładowania pojazdów elektrycznych. Ich ładowanie wpływa na profil zapotrzebowania na energię elektryczną w budynku. Samochody elektryczne stanowią jednocześnie czasowo dostępny magazyn energii elektrycznej. By szczegółowo przeanalizować pracę takiego układu zaproponowano w modelowaniu podejście krokowe. Mianowicie na wstępie zaproponowano model najprostszego układu, do którego następnie dodawano kolejne elementy. W rezultacie zaprezentowano następujące modele: •. Punkt odniesienia - model mający na celu odwzorowanie najczęściej występującego przypadku, czyli budynek biurowy bezpośrednio połączony z siecią energetyczną, bez instalacji fotowoltaicznej ani stacji ładowania samochodów elektrycznych. W modelu tym skupiono się głównie na analizie kosztu zakupu energii w ramach różnych jej taryf.. •. Model zmodyfikowany, w którym rozważono możliwość wykorzystania instalacji fotowoltaicznej. Uwzględniono koszt pozyskania energii z systemu PV.. •. Model budynku biurowego ze stacją ładowania samochodów elektrycznych, ale bez instalacji fotowoltaicznej. Pobór energii odbywa się wyłącznie z sieci.. •. Model budynku biurowego wyposażanego w instalację fotowoltaiczną oraz stację ładowania samochodów elektrycznych. Przepływ energii pomiędzy samochodami elektrycznymi a budynkiem (stacją ładowania) odbywa się jednokierunkowo – wyłącznie ładowanie.. •. Model finalny, w którym umożliwiono przepływ energii z samochodów elektrycznych do budynku biurowego.. Na potrzeby symulacji oraz optymalizacji zaproponowane powyżej modele zaimplementowano w środowisku arkusza kalkulacyjnego MS Excel oraz Matlab. By rozwiązać problem optymalizacji liniowej wykorzystano ogólnie dostępny dodatek do programu MS Excel w postaci Open Solver oraz akademicką licencję solwera Gurobi, oraz programowanie liniowe w środowisku Matlab (kod w załączniku). Modelowanie oparto o dane historyczne dotyczące 8.

(9) zapotrzebowania na energię elektryczną oraz warunki atmosferyczne (nasłonecznienie, temperatura). Dokładna lokalizacja budynku biurowego (poza wskazaniem na miasto Kraków) nie może zostać ujawniona. Na podstawie przeprowadzonych analiz sformułowano następujące wnioski: •. Taryfa C21 jest taryfą najkorzystniejszą pod względem finansowym dla wybranego budynku biurowego (bez instalacji fotowoltaicznej).. •. Wykorzystanie systemu fotowoltaicznego w budynku biurowym może obniżyć koszt jednostki energii o 0,06 PLN/kWh oraz zwiększyć niewrażliwość na wzrost cen energii na rynku.. •. Źródło generacji fotowoltaicznej znacząco modyfikuje profil zapotrzebowania budynku biurowego na energię elektryczną. Wynika to z faktu, iż profil generacji PV jest zbliżony do zapotrzebowania budynku biurowego w ujęciu dobowym oraz rocznym. Należy jednak podkreślić, iż w ujęciu tygodniowym przewymiarowany system PV może generować znaczne nadwyżki energii elektrycznej, w szczególności w dni wolne od pracy.. •. Z punktu widzenia krajowego systemu energetycznego system PV ma potencjał redukcji obserwowanego szczytu zapotrzebowania na energię elektryczną w budynkach biurowych. Obniżenie zapotrzebowania szczytowego jest szczególnie istotne, jeśli następuje. w. dni. o. wysokiej. temperaturze,. gdy. sprawność. generatorów. konwencjonalnych (które dominują w krajowym systemie energetycznym) jest obniżona. •. Ładowanie floty 50 samochodów elektrycznych w sposób naturalny podnosi koszt energii elektrycznej w budynku biurowym. Całkowity wzrost rocznego kosztu energii kształtuje się na poziomie 2,9% dla taryfy C21 oraz 3,0% dla taryfy C22b.. •. Strategia ładowania samochodów elektrycznych powinna być zoptymalizowana w taki sposób, by jej wpływ na obciążenie rezydualne (obciążenie - generacja PV) zostało zminimalizowane. Uproszczona strategia ładowania (tj. ładowanie natychmiast po dotarciu do stacji ładowania) powoduje wzrost porannego szczytu zapotrzebowania na moc elektryczną.. •. Strategia ładowania oparta na minimalizacji całkowitego kosztu energii elektrycznej prowadzi do zwiększenia się zmienności krzywej zapotrzebowania na moc elektryczną budynku biurowego z instalacją PV oraz stacją ładowania samochodów elektrycznych.. 9.

(10) •. Możliwy wzrost cen energii elektrycznej w przyszłości znacznie zwiększa rolę pojazdów elektrycznych jako mobilnych magazynów energii dla budynków biurowych. Oznacza to, że wartość mobilnego magazynowania energii elektrycznej jest większa z punktu widzenia kosztu energii w budynku biurowym. Przy cenach energii elektrycznej sięgających 200% ich poziomu z 2017 r., udział pojazdów elektrycznych w pokryciu obciążenia budynku sięga ponad 2% w skali rocznej.. •. Potencjalna przyszła implementacja zaproponowanej koncepcji budynku biurowego z systemem PV oraz stacją ładowania samochodów elektrycznych będzie wymagała systemu wspierającego wzmożony przepływ informacji takich jak: prognoza pogody, prognoza uzysku energii z instalacji PV, prognoza zapotrzebowania na moc elektryczną budynku, prognoza cen energii elektrycznej (jeśli taryfy nie są jej obowiązującym źródłem), oczekiwany stopień naładowania samochodów elektrycznych po dotarciu do stacji ładowania oraz w momencie odjazdu.. Rozprawa jest ustrukturyzowana w następujący sposób: •. Rozdział pierwszy – Wprowadzenie, umiejscawia rozprawę w szerszym kontekście obecnych kierunków naukowych i trendów gospodarczych oraz kończy się sformułowaniem hipotezy oraz celów badań.. •. Rozdział drugi - Przegląd literatury, prezentuje najważniejsze prace związane z tematyką doktoratu oraz podsumowanie dotyczące wkładu rozprawy w stan wiedzy naukowej.. •. Rozdział trzeci – Metody oraz dane, poświęcony jest sformułowaniu modeli matematycznych opisujących analizowane systemy oraz przedstawia dane wejściowe oraz założenia użyte w symulacjach.. •. Rozdział. czwarty. –. Wyniki,. koncentruje. się. na. prezentacji. rezultatów. przeprowadzonych symulacji oraz optymalizacji funkcjonowania poszczególnych układów. W rozdziale czwartym można wyróżnić istotny fragment czyli Dyskusję, która dedykowana jest pogłębionej i krytycznej analizie otrzymanych wyników z perspektywy ich implementowalności oraz znaczenia. •. Rozdział piąty - to podsumowanie zrealizowanej dysertacji, określenia ograniczeń pracy oraz przyszłych kierunków badań.. Pracę wieńczy spis literatury oraz załącznik w postaci kodu użytego do optymalizacji mocy zainstalowanej w układzie oraz pracy poszczególnych komponentów. 10.

(11) Content Abstract ................................................................................................................................................... 3 Extended abstract in Polish ..................................................................................................................... 6 Thesis structure – brief overview .......................................................................................................... 13 Nomenclature table................................................................................................................................ 14 1.. 2.. Introduction ................................................................................................................................... 17 1.1.. Aim ........................................................................................................................................ 23. 1.2.. Hypothesis and research goals............................................................................................... 23. Litereature context ......................................................................................................................... 25 2.1.. 2.1.1.. Photovoltaics ................................................................................................................. 26. 2.1.2.. Office buildings ............................................................................................................. 27. 2.1.3.. Electrical vehicles .......................................................................................................... 29. 2.2.. 3.. Context .................................................................................................................................. 26. System subcomponents ......................................................................................................... 35. 2.2.1.. Photovoltaics in buildings ............................................................................................. 35. 2.2.2.. Electrical vehicles in buildings ...................................................................................... 42. 2.2.3.. Use of photovoltaics for EV charging ........................................................................... 46. 2.2.4.. Photovoltaics in office building which has an EV charging station .............................. 54. 2.3.. Research on electrical vehicles in Polish literature ............................................................... 57. 2.4.. Novel contribution ................................................................................................................. 58. Methods and data........................................................................................................................... 59 3.1.. Conceptual configurations of considered systems................................................................. 59. 3.2.. Mathematical formulation of the systems operation ............................................................. 63. 3.2.1.. Scenario B (Benchmark): OB – GRID (Office building and electrical grid) ................ 63. 3.2.2. Scenario A1: PV–OB–GRID (Office building with PV system and connected to electrical grid)................................................................................................................................ 63 3.2.3. Scenario A2: (OB, EV) – GRID (Office building with electrical vehicles charging station connected to the electrical grid) ......................................................................................... 64 3.2.4. Scenario A3: (OB, EV) – PV– GRID (Office building with electrical vehicles charging station and photovoltaic installation connected to the electrical grid) .......................................... 66 3.2.5. Scenario A4: OB–EV–PV–GRID (Office building with electrical vehicles charging station and photovoltaic installation connected to the electrical grid with enabled power flow between electrical vehicles and building)...................................................................................... 66 3.3.. Mathematical formulation of models subcomponents........................................................... 69. 3.3.1.. Electricity tariffs ............................................................................................................ 69. 3.3.2.. PV and EV charger investment and operation costs...................................................... 70. 3.3.3.. Energy generation from PV system ............................................................................... 70. 3.3.4.. Charging and discharging of EVs’ battery .................................................................... 71 11.

(12) 4.. 3.4.. Input data (visualization) ....................................................................................................... 71. 3.5.. Parameters ............................................................................................................................. 74. 3.6.. Software................................................................................................................................. 75. 3.7.. Scenarios, objectives and modelling approach ...................................................................... 76. Optimization results ...................................................................................................................... 77 4.1.. Benchmark scenario (B) – present cost of electricity ............................................................ 77. 4.2.. Office building with PV installation – scenario A1 .............................................................. 80. 4.2.1.. Maximal capacity of PV system .................................................................................... 81. 4.2.2.. PV impact on load curve ............................................................................................... 82. 4.3.. Office building with EV charging station – scenario A2 ...................................................... 88. 4.4.. Office building with EV charging station and PV installation – scenario A3 ....................... 95. 4.4.1.. Linear model for scenario A3 ........................................................................................ 97. 4.4.2.. Scenario A3 – analysis of residual load after linear optimization ................................. 99. 4.5.. Office building with EV charging station and PV installation– scenario A4 ...................... 105. 4.5.1. 4.6.. 5. Loosening some constraints ........................................................................................ 115. Discussion ........................................................................................................................... 126. 4.6.1.. Operation of EVs ......................................................................................................... 126. 4.6.2.. Cost of energy from PV system................................................................................... 129. 4.6.3.. Degradation of batteries .............................................................................................. 131. 4.6.4.. Information exchange with power supplier ................................................................. 132. 4.6.5.. Increasing utilization of charging station .................................................................... 132. 4.6.6.. Improving system operation with life data .................................................................. 133. Conclusions ................................................................................................................................. 136 5.1. Summary and main findings ................................................................................................ 136. 5.2. Novel contribution ............................................................................................................... 140. 5.3. Further research directions .................................................................................................. 141. 6. References ................................................................................................................................... 142. 7. Appendix – Matlab code for system optimal sizing .................................................................... 150. 12.

(13) Thesis structure – brief overview. INTRODUCTION. BACKGROUND AND MOTIVATION, PRESENTATION OF HYPOTHESIS AND OBJECTIVES. LITERATURE REVIEW. PRESENTATION OF WORKS RELEVANT IN THE FIELD AND IMPORTANT FROM THE THESIS PERSPECTIVE. METHODS AND DATA. INTRODUCTION OF MODELS, TOOLS AND DATA USED FOR THE PROBLEM SOLUTION. RESULTS AND DISCUSSION. PRESENTATION OF RESULTS FOR INDIVIDUAL MODELS AND DISCUSSION. CONCLUSIONS. A BRIEF SUMMARY OF WORK COMPLETED OUTLINE OF FUTURE RESEARCH DIRECTIONS. APPENDIX. MATLAB CODE USED FOR SYSTEM SIMULATION AND OPTIMIZATION. 13.

(14) Nomenclature table Abbreviation, parameter, index. η𝑃𝑉 𝐴𝑡 𝐶𝐹𝑡 𝐸𝐸𝑉_𝑆 𝐸𝑉_𝑆𝑂𝐶 𝐸𝑀𝑎𝑥 𝐸𝑉_𝑆𝑂𝐶 𝐸𝑀𝑖𝑛 𝐸𝑉_𝑈 𝐸𝑖,𝑗,𝑘=8 𝐴 𝐸𝑖,𝑗,𝑘 𝐸𝑉_𝑂𝐵 𝐸𝑖,𝑗,𝑘 𝐸𝑉_𝑆𝑂𝐶 𝐸𝑖,𝑗,𝑘 𝐸𝑉_𝑈 𝐸𝑖,𝑗,𝑘 𝐺_𝐸𝑉 𝐸𝑖,𝑗,𝑘 𝐺_𝑂𝐵 𝐸𝑖,𝑗,𝑘 𝑂𝐵 𝐸𝑖,𝑗,𝑘 𝑂𝐵_𝑅 𝐸𝑖,𝑗,𝑘 𝑃_𝐸𝑉 𝐸𝑖,𝑗,𝑘 𝑃_𝑂𝐵 𝐸𝑖,𝑗,𝑘 𝑃𝑉 𝐸𝑖,𝑗,𝑘 𝑃𝑉_𝐵 𝐸𝑖,𝑗,𝑘 𝑃𝑉_𝐶 𝐸𝑖,𝑗,𝑘 𝑃𝑉_𝐸𝑉 𝐸𝑖,𝑗,𝑘 𝑃𝑉_𝑂𝐵 𝐸𝑖,𝑗,𝑘. 𝐸𝑡 𝐻 𝑆𝑇𝐶 𝐼𝑜 𝑀𝑡. 𝐶ℎ𝑎𝑟𝑔𝑒𝑟. 𝑃𝑀𝑎𝑥 𝑃𝑃𝑉 𝑃𝑖𝑀𝑎𝑥 𝑇𝐶 𝑇 𝑁𝑂𝐶𝑇 𝑇 𝑆𝑇𝐶 𝑇𝑎 𝑒𝑐𝑡. Meaning, description. Unit. overall efficiency of the PV system annual total cost net cash flow in period t standard electricity consumption per 1 km of driving maximal electrical vehicle battery state of charge the minimal acceptable level of the batteries state of charge energy used by the EVs in the morning home-work journey. % PLN PLN kWh kWh kWh kWh. aggregated energy demand (office building and EV) energy from the EV batteries used to cover the office building load electrical vehicle battery state of charge. kWh kWh. energy used from the EV’s batteries during normal operation (driving) energy used to charge the electrical vehicles. kWh. energy demand of the office building covered by the national power system (grid) during month i, day j, hour k. energy demand in office building in month i, day j and hour k office building residual load. kWh. energy from the grid (additional generator) used to charge the EVs office building load covered from the grid. kWh. PV generation energy generation from a PV system with a nominal capacity of 1kW curtailed PV generation. kWh kWh. energy from PV system used to charge EVs. kWh. energy demand of the office building covered by the PV installation. energy consumption during given hour irradiation in standard testing conditions initial capital expenditures produced electricity in year t the maximal charging power of the charging station installed capacity in PV generator maximal energy demand declared for given month operating temperature of PV modules temperature in normal operating conditions PV modules operation temperature in standard testing conditions air temperature vector representing hourly energy cost per unit of energy. kWh. kWh. kWh. kWh kWh. kWh. kWh. kWh kWh/m2 PLN kWh kW kW kW °C °C °C °C PLN/kWh 14.

(15) 𝑡𝑗,𝑖,𝑘 𝜂𝐶 𝜂𝐶𝑜𝑜𝑙 𝜂𝐷 𝐻𝑒𝑎𝑡 𝜂 A/S A1-A4 AC/DC ANN B BEMS BEV BIPV C21, C22a, C22b CAPEX CO2 DER-CAM EC EV EVC G2V GRG GUS BDL GW GWh ICE kW kWh kWp l LCOE MW n OB OBEMS OPEX PEV PHEV PSO PV PVC r SOC t TEC TWh. outdoor temperature charging efficiency of the EVs charging station increase in energy consumption due to the cooling needs discharging efficiency of the batteries increase in energy consumption due to heating needs ancillary services four configurations of the system layout development (scenarios) Alternating/Direct Current Artificial Neural Network Benchmark scenario Building Energy Management System Battery Electric Vehicle Building-Integrated Photovoltaics electricity tariffs. °C % kWh/°C % kWh/°C -. investment cost carbon dioxide Distributed Energy Resources Customer Adoption Model energy cost electrical vehicle EVs’ charger cost grid-to-vehicle General Reduced Gradient Central Statistical Office, Local data bank gigawatt, power unit gigawatt hour, energy unit internal combustion engines kilowatt, power unit kilowatt hour, energy unit kilowatt peak, peak power of a PV system or panel real interest rate levelized cost of electricity megawatt, power unit life time office building Office Building Energy Management System operation and maintenance cost plug-in electrical vehicle plug-in hybrid electric vehicle particle swarm optimization photovoltaic annual cost of PV installation discount rate State of Charge periods (usually years) total energy cost terawatt hour, energy unit. PLN PLN PLN % year PLN % % year PLN -. -. 15.

(16) URE V2G V2H 𝐶𝐶 𝐻 𝑁𝑃𝑉 𝑄𝐶 𝑅𝐸𝑆𝐶 𝑆𝐶 𝑇𝐶 𝑉𝐶 𝜇. Energy Regulatory Office vehicle-to-grid vehicle-to-home constant charge irradiation net present value quality charge renewable energy charge subscription charge transition charge variable charge temperature depended efficiency reducing coefficient. PLN/kW kWh/m2 PLN PLN/kWh PLN PLN PLN PLN %/°C. 16.

(17) 1. Introduction The global economy is becoming increasingly complex. Despite the fact that big corporations dominate the world and the transportation of goods is faster than ever before, the availability of energy is still subjected to many constraints. Energy is vital for every civilization. Without energy it is impossible to create a prosperous nation, which will give its citizens a high quality of life. Energy is fundamental for all life related processes, starting from agriculture, through transport and ending in powering sophisticated manufacturing facilities, which deliver mandatory goods for the modern society. Energy can be even used these days to power the desalination plants, which can provide fresh water in areas, which due to its scarcity could not support a thriving civilization. A progress in renewable energy sources in terms of efficiency as well as cost leads to a situation where they can on an economically justified terms fuel the desalination processes – making the access to the fresh water of a lesser importance than access to the energy. However, to fuel the civilization supporting processes the energy has to be available in many different forms. Therefore, currently the access to stable, diversified and certain supply of fuels is a foundation of many countries energy security policy. Especially those in which the locally available conventional fuels have been already exploited or have never been sufficient. An example of such fuel/energy source might be natural gas, which is a vital component of many industrial processes as well as a major heating fuel in many countries. Figure 1.1 visualizes the change in gas prices in Europe and USA relative to the price level in 2010. On this figure, one can observe how on average the gas prices in Europe are significantly higher than those in USA. In Europe, the gas prices can decrease in two years by 60% and then again rise in two years by 50%. Whereas in USA which has access to its own gas resources (particularly shale-gas which extraction started in 2008) the variability is much smaller. What can be the conclusions from such data/chart? Europe is more vulnerable to prices changes of natural gas and therefore its industry is subject to bigger threats. Furthermore, such vulnerability is another crucial signal that it is vital to depart from conventional fuel-based economy and start focusing on renewable energy sources.. 17.

(18) Figure 1.1 Normalized (with respect to 2010 levels) natural gas prices development in the USA and Europe. Data source: World Bank. Graph: own elaboration.. The earlier example focused on USA and Europe in general. Which is quite far away from the Polish context of this dissertation. Therefore, Figure 1.2 presents the fluctuations of coal prices in Poland over more than last 10 years on a monthly basis. Clearly, the data has some seasonality on an annual scale – the coal is most expensive in the heating season and cheapest in summer. However, more striking is even the general trend. Over considered 13 years the coal price increased almost by 100% harming not only the individual customers (which now have to pay more for heating) but also industry and electricity generation. An increasing coal price (a resource which is theoretically very abundant in Poland), which for many years was believed to be the foundation of Polish energy security is a threatening situation which may be considered as a symptom, indication that coal industry is not catching up with the trends observed worldwide. Namely a growing awareness of man-caused climate change (and resulting introduction of CO2 trading market mechanisms) as well as global tendency of transitioning power systems to those based mostly on low-carbon or zero-carbon technologies, which already often can provide energy at a cost lower than conventional generators.. 18.

(19) Figure 1.2 Monthly average coal prices in Poland. Starting January 2006 till September 2019. Data source: GUS BDL. Graph: own elaboration.. The issue of cost is visualized on Figure 1.3. For that purpose, a metric of the levelized cost of electricity has been considered which in simple terms is the amount of energy provided during lifetime over the total costs. The color bars represent each renewable technology for the year 2010 and 2017. The bottom of the bar is the minimal and the top is the maximal observed price. A black rhombus indicates the mean value. Red arrows show the observed change in mean cost for each technology. The long horizontal grey line is the fossil fuel generation range. From the Figure 1.3 we can make the following observations: •. Four out of seven major renewable energy sources had a decreasing trend in terms of mean energy provision cost. The highest absolute cost drop was observed for photovoltaics and exceeded 0.25 $/kWh.. •. For two technologies (geothermal and hydropower) the mean cost of energy slightly increased. This might be attributed to the following. In case of geothermal, there are not so many projects that are currently being realized and therefore a higher variability of cost can be expected. For the hydropower, there is an increasing number of environmental concerns regarding this energy source. In addition, the number of potential sites is decreasing therefore the rise in cost can be expected.. •. No significant change in mean cost had been observed for biomass.. •. Only two out of seven technologies (concentrated solar power) and offshore wind cannot currently provide energy at a cost lower than the conventional generation. 19.

(20) •. Currently (as on 2017) five out of seven major renewable energy sources could provide the energy at a cost lower than the conventional generation. Furthermore, this cost is usually at the lower end side of the cost of energy from fossil fuels.. 0.45. Photovoltaic Concentrated solar power. 0.4 0.35. Hydropower Offshore wind. Cost [$/kWh]. 0.3. 0.25. Onshore wind. Biomass. 0.2. Geothermal 0.15 0.1 0.05 0 2010 2017 2010 2017 2010 2017 2010 2017 2010 2017 2010 2017 2010 2017 Fossil fuel generation cost range. Average value. Figure 1.3 Global levelized cost of electricity from utility-scale renewable power generation. Source: IRENA Renewable Energy Cost Database. Graph: own elaboration.. For the observations provided regarding Figure 1.3 a following comment is mandatory. The values presented in this figure are capacity weighted average levelized costs of electricity for power plants commissioned in given year. The local costs of capital, labor, capital expenditures and most importantly potential of renewable energy may vary strongly. Therefore, it is important to note that usually the lowest values are achieved for perfect sites with an abundance of solar or wind energy where such power stations achieve very high values of capacity factors. The trends in energy cost from renewable generators have a direct impact on their installed capacities worldwide as it is shown on Figure 1.4. However, there is no wonder of course that the renewable energy sector is dominated by hydropower as this was an important energy source for many countries for decades. What is indeed remarkable is the increasing role of other renewable sources, particularly wind and solar. Currently renewables other than hydropower supply more than 1/3 of the total energy provided by renewable energy sources. 20.

(21) Figure 1.4 Global renewable energy consumption. Other: biomass, geothermal and other modern technologies such as wave and tidal. Source: BP Statistical Review of Global Energy. Graph: own elaboration.. Owning to the decreasing prices of renewables and the growing social awareness of the climate change, it seems that the transformation of the power systems is unavoidable. However, considering their great role in countries’ economies, such transformation is not a process that in all cases can be realized smoothly and without obstacles. Apart from the social aspects1 of each transformation, the technical issues have to be resolved as well. In case of renewables, the most commonly addressed problem is how to integrate the intrinsically variable renewable energy sources (such as wind and solar) to the power system? The issue of the variable nature of solar and wind generators is very problematic because the existing power systems were build based on the assumption that it is the demand side that is the variable one2 and based on the forecasted load the generators can be optimally dispatched considering the economic criteria. However, with the advent of large-scale variable solar and wind generators also the supply side. 1. For example, a large number of people directly involved in the conventional power generation – coal mines or coal burning power stations might naturally be against the transformation of the power system to that one based on renewables. As replacing the conventional generation with renewables means in theory that their jobs will not be longer necessary. Therefore, that is why this process should be termed as transformation not revolution of the power system. 2 For the supply side of the power system naturally a certain variability can be expected as well. For example, outage of power stations or a failure of transmission network.. 21.

(22) became variable3. Owning to the fact that the renewable generators often gained priority in the energy system (the energy generated by them has a priority access to the grid and is consumed first) the reality of conventional generators became harsh. Considering above over the recent years many research papers have been dedicated to the issue of an efficient integration of variable renewable generators to the power system (Jones, 2017). One of the often-raised concepts is to use the electrical vehicles as a means of their integration (Jacobson and Delucchi, 2011; Delucchi and Jacobson, 2011). On the one hand, the electrical vehicles are from the perspective of the power grid just another load. A load that is to some extent variable and characterized by significant and sudden increase in power demand (fast charging). On the other hand, the electrical vehicles can be considered as an energy storage medium which is simply not available (cannot be charged, discharged) all the time, but only when it is connected to the charger. Therefore, it is clear that when large number of EVs will start appearing in the power system some additional problems with the charging patterns may arise. However, simultaneously we should consider the EVs as an opportunity for the integration of variable renewable generators. Their storage potential might be an option to store the surplus energy from renewable sources or to shave some peak loads. The importance of renewable energy sources is particularly important in cities. In recent decades, cities became the centers of human activities. However, from the sustainability perspective they cannot provide themselves with neither agricultural nor energy related products. One of the energy sources that can be exploited in cities on a larger scale are photovoltaics. This energy source can be easily applied to existing roofs or facades. In consequence, at least part of the citywide energy demand could be covered by renewable sources. Following this reasoning, we can state that a city is made up of buildings. Each one of them is characterized by its individual load pattern. Furthermore, the buildings are divided in many classes depending on their utilization. One of them, which is recently gaining on popularity (especially in bigger polish cities) is office building. In cities (despite the municipality authorities’ efforts) a large part of commute is made by own cars. Currently these are cars with internal combustion engines. However, in the future one may expect that electrical vehicles will replace them. An assumption can be made that at the forefront of this. 3. The variability of solar and wind generators can be to some extent overcome by prediction models or spatial distribution of generators which smooths their generation curves.. 22.

(23) transportation transformation will be standing bigger corporations, which will invest in EV based fleets. Considering above a potential synergy can be exploited by coupling the building, transport and energy systems. In this thesis, such coupling is realized by investigating a PV installation operating as an energy source for an office building with a EV charging installation. The remainder of this thesis is organized as follows: the next two subsections introduce the aim of the thesis, hypothesis and main research questions. Section 2 focusses on the literature review, which is a basis for a) further research b) claim of this thesis novel contribution to the science. Section 3 presents the formulated mathematical models and input data. Section 4 describes in detail the obtained results. Section 5 summarizes the results and provides conclusions from the work performed. The thesis ends with the list of references and an Appendix, provides the Matlab code implemented for optimal system sizing and dispatching.. 1.1. Aim The purpose of this work is to investigate whether the electrical vehicles can be used as a mobile energy storage for office buildings with PV installation. The thesis focusses on a set of possible scenarios considering energy tariffs and the optimization approach.. 1.2. Hypothesis and research goals Based on the literature review of relevant works the following hypothesis was formulated: Passenger electrical vehicles can serve as “mobile energy storage" mediums for solar office buildings For better understanding of the hypothesis formulation, a brief definition of the concepts mentioned is as follows: “Electrical vehicle” – also referred to as EV is a mode of transport, which uses electric motors for propulsion. In this thesis, the EVs powered by a self-contained battery are considered. For the simulations purposes a generic EV model was selected as a reference with battery capacity of 50 kWh.. 23.

(24) “Serve” – here should be understood as a potential use of energy stored in the EVs batteries for covering the part of the office building load. “Mobile energy storage” – this concept assumes that the energy storage is not available onsite the whole time. The EVs batteries can be used for covering the office building load only during specific hours. The concept of mobile energy storage is also developed in case of islandic/offgrid communities4 “Solar office building” – the term solar building was first coined for a building located in Albuquerque in New Mexico5. This particular building was heated by solar energy. Here this concept is a little bit extended to the use of solar energy to generate electricity (by means of photovoltaics system) to cover part of the building load. The building is specified to be an office building. In this thesis, it is assumed that the PV system does not necessarily has to be located in the close proximity of the office building nor be integrated with the building. To verify the validity of the above presented hypothesis the following research goals were formulated: •. Establishing the energy cost in office building for a benchmark scenario for different energy tariffs.. •. Analysis of electricity cost for different configuration and charging strategies of electrical vehicles.. •. Analysis of the impact of different system layouts and operation strategies on the residual load curve.. •. Formulating a linear programming model to investigate the possibility of using EVs as energy storage.. The next section presents in detail the current state of knowledge in area of EVs integration with buildings. Results from investigated studies enabled to formulate the above presented hypothesis and made relevant assumptions during modeling activities.. 4 5. https://www.manasecurityandpower.com/power-storage https://en.wikipedia.org/wiki/Solar_Building. 24.

(25) 2. Litereature context The investigated in this thesis topic, which has been formulated as “Model of energetic cooperation between electrical vehicles and solar office building”, touches at least three potentially broad research areas. To these one can include: photovoltaics and office buildings (or buildings in general); electrical vehicles and office buildings; and finally photovoltaics and electrical vehicles. The potential relationships between these topics are for clarity visualized on Figure 2.1. Clearly, the focal point (the common area) for all three of them is simultaneously the subject of investigation undertaken. Considering the above, it has been decided that a good literature review, will indicated the research gaps and simultaneously the novel contribution of this thesis should in detail describe research articles which addressed all these concepts (PV+OB, OB+EV and PV+EV) and finally present papers which dealt with the final system structure namely: PV+EV+OB. Bearing in mind the need to present the broader context of research conducted literature review section starts however with presenting the recent advances in area of photovoltaics, office buildings and electrical vehicles separately.. OB. EV. PV. Figure 2.1 Relationship between individual subsections of the literature review is presented in form of basic Venn diagram. Such presentation clearly highlights the existence of strong connections as well as the fact that the subject of this thesis is their focal point.. 25.

(26) 2.1. Context This section focusses on providing the basic information regarding the photovoltaics, office buildings and electrical vehicles. The focus is paid on their recent status and development in Poland. The situation in foreign countries is only briefly mentioned to see if the general trends match. 2.1.1. Photovoltaics With the observed technological progress and economy of scale the photovoltaics systems are becoming an important energy source on a both local (households) and bigger (national power systems) scales. The reduction of PV modules costs and efficiency increase leads to a situation when they are cost competitive with conventional generators (Yan et al., 2019). Figure 2.2 visualizes the change in installed capacity in PV systems in Poland over the last 10 years. The data for 2019 is as on 31st of May. Clearly an upwards trend can be observed. The growing popularity of household and industrial (+1MW) scale PV systems in Poland may result from: growing electricity prices, increasing social awareness of the need to utilize sustainable energy sources, decreasing cost of PV system, support incentives organized by the government in form of net-metering, feed-in tariffs, subsidies and auctions.. Figure 2.2 Installed capacity of PV systems in Poland accordingly to the Energy Regulatory Office (URE). Source: own elaboration based on URE. In 2019 data until June. URE recognizes installations with a concession for power generation which does not include prosumers or smaller installations. Accordingly, to PSE (www.pse.pl) the installed capacity in May 2020 exceeded 1800 MW (of all PV installations).. 26.

(27) The trends observed in Poland are in general following the ones present worldwide (as shown on Figure 2.3). However, the order of magnitude is of course different as it is expected that by the end of 2020 the cumulative installed capacity in the world will exceed 650 GW.. Figure 2.3 Worldwide installed capacity in PV systems. Data for 2018 and 2019 are tentative estimates. Source: https://en.wikipedia.org/wiki/Growth_of_photovoltaics. Graph: own elaboration.. 2.1.2. Office buildings An office building is a form of a commercial building that needs to meet certain legal (required amount of light) and infrastructural (network connection) requirements. The primary objective of the office building is to provide the working place for administrative and managerial employees. Over the recent years in Polish cities, one could easily observed a rapid growth in the number of office buildings. They are being located in various parts of the cities often on postindustrial sites. Currently, the cumulative area of office buildings in Poland is reaching approximately 10 000 million square meters and the capital city (Warsaw) has more than 50% of this number. The next is Kraków and Wrocław (as shown on Figure 2.4).. 27.

(28) Figure 2.4 Office buildings area in major polish cities. In total, it constitutes to roughly over 95% of total available office space in Poland. Source: http://www.qbusiness.pl/uploads/Raporty/colbiura12018.pdf. Graph: own elaboration:. Considering the growing number of office buildings, it is quite clear that they have heavy impact on the urban areas in terms of traffic flows as well as energy system. This impact needs to be addressed in order to achieve the goals of sustainable development. As described in (Mikulik, 2018) office buildings have some typical daily, weekly and seasonal demand patterns which are driven by both weather and work regime. The load pattern of the building considered in this thesis is later described in detail. The role of building sector (which included the office building) in total energy consumption is quite clear as shown on Figure 2.5.. 28.

(29) Figure 2.5 Structure of energy consumption by sectors in USA (Poland is presented in later part of this section). Source: http://buildingsdatabook.eren.doe.gov/. Graph: own elaboration.. 2.1.3. Electrical vehicles Electrical vehicles are not a modern concept. They came into the existence in the mid of 19th century when the electricity was the preferred fuel in the transportation sector. In the 21st century, a renewed interest EV is observed mostly due to the technological advancement (mostly battery energy storage) and stronger focus on sustainability and efficient utilization of renewable energy. The total number of registered EVs in Poland as on 31.05.2019 reached 4000 meaning that over last 6 months on average 200 EVs were registered per month (as shown on Figure 2.6). The dominant EV (in terms of sells number in 2018) was a Nissan Leaf followed by BMW i3 as shown on Figure 2.7.. 29.

(30) Figure 2.6 Cumulative number of EVs registered in Poland. Data: CEPIK. Graph: own elaboration.. Figure 2.7 Electrical vehicles sold in Poland in 2018 by type. Data: IBRM Samar. Graph: own elaboration.. The trends observed in Poland (Figure 2.6) are similar to those observed worldwide. As shown on Figure 2.8 the annual growth in the number of cars is clearly exponential and as on end of 2018 the fleet of EVs exceeded 5 million vehicles. Such a big fleet of EVs has an immense 30.

(31) impact on the worldwide electricity consumption. Accordingly, to the International Energy Agency in 2018 the EVs “consumed” 58 TWh of electricity, which is roughly 1/3 of the total electricity consumption in Poland.. Figure 2.8 Worldwide cumulative number of EVs registered. Source: https://webstore.iea.org/. Graph: own elaboration.. Currently in Poland, the transport sector has very small share (Figure 2.9) in the total electricity consumption (around 5 TWh that is 3% of total electricity consumption). However, it must be noted that this consumption should be attributed mostly to trolleys, trams, underground systems, freight trains and heavy rail transport. Currently, the share of EV is so small that it has a minor role in the electricity consumption. Although, local differences might be obviously observed.. 31.

(32) Figure 2.9 Electricity usage by different economy sectors in Poland from 2001 to 2017. Source GUS BDL. Graph: own elaboration.. Figure 2.10 Structure of electricity usage in 2017 considering different economy sectors in Poland. Source: GUS BDL. Graph: own elaboration.. Referred above Figures 2.9 - 2.10 present numbers concerned the electricity consumption in transport sector. However, currently the overwhelming part of the transport activities are. 32.

(33) realized by use of fossil fuels (mostly oil, petrol and gas). As shown on Figure 2.11 the primary energy consumption in the transport sector in Poland oscillates around 200 TWh.. Figure 2.11 Primary energy consumption in transport sector in Poland over the years 2010-2015. Source: Eurostat. Graph: own elaboration.. Considering the above, lets design a simple thought experiment related to 100% electric transport sector in Poland. Obviously, we cannot simply say that current 200 TWh of primary energy consumed by transport sector will be equal to 200 TWh of electricity consumed by a fully electric transport sector. This would mean more than doubling the current electricity consumption in Poland (current consumption 170 TWh as on 2018 accordingly to www.pse.pl) and naturally could not be covered by available electricity generating capacity6. However, the total consumption of primary energy in case of transport sector results from the overall low efficiency of the internal combustion engines (ICE). In which, only roughly 25-30% of the primary energy is converted into power – actual movement of the vehicle. Considering the above, we can estimate that in case of the fully electric transport the electricity consumption should be equal to 35-45% of the primary energy bearing in mind the charging losses (a rough estimate which neglects for example the heating provided by ICE but which requires higher. 6. Especially considering the fact that the EV charging may significantly alter the energy demand pattern and the observed peak load.. 33.

(34) energy consumption per kilometer in case EV7). Considering the above, it becomes clear that in the future the electrification of the transport and especially the reemergence of EV will have an immense impact on the operation of the power system. Summarizing the above, in this dissertation the challenging and already present problems related to the broadly understood energy system have been addressed. Therefore, it seems like mandatory solutions on a development and management level should be proposed. In this thesis, a specific topic has been undertaken, which combines above (sections 2.1.1 – 2.1.3) discussed concepts. The next section presents a tabular overview of research articles dedicated to buildings, photovoltaics and electrical vehicles.. 7. This issue is however properly modelled in the later sections of this thesis.. 34.

(35) 2.2. System subcomponents This section of the literature review deals in detail with the available literature on the following topics: photovoltaics coupled with buildings (especially office buildings); buildings and electrical vehicles; photovoltaics and electrical vehicles. The final section is dedicated to the concepts simultaneously considering photovoltaics, electrical vehicles and office buildings. The literature is selected in such a manner that it acts as a representative sample.. 2.2.1. Photovoltaics in buildings Photovoltaics are a modular and flexible technology, which enables an efficient conversion of solar energy into the electricity. The PV systems are easily scalable and can be adapted to various environments. The recent developments in terms of efficiency and the economy of scale (which decreases the price of PV modules) enabled them to reach grid parity and offer electricity at prices often lower than that from the national grid. Photovoltaic systems can play especially big role in the urban environments, which are characterized by a high population density, high land value and scarcity of available ground areas. In such circumstances, the strength of PV systems is particularly apparent. Namely, the PV modules can be installed on buildings’ roofs, cover-parking areas or become facades of buildings. Situating PV systems in such sites locates them in a close proximity to the load that they can serve and thereby (usually), potential transmission losses can be also reduced. Over the recent years, many research papers have been dedicated to the concept of the use of photovoltaics in buildings. Significant part of these research actions focused on the issue of using hybrid photovoltaic/thermal systems (providing simultaneously electricity and heat), building integrated photovoltaics using semi-transparent photovoltaics panels or the issue of self-consumption and peak shaving by means of photovoltaics. The below presented literature review is of course not exhaustive and its aim is to give a general insight in this research area. The review is structured in a chronological manner starting from a paper published 10 years ago.. 35.

(36) Table 2.1 A review on papers dedicated to the concept of using photovoltaic systems in buildings.. Reference. Li et al., 2009 Energy and cost analysis of semitransparent photovoltaic in office buildings. Description. This paper was dedicated to the energy and cost analysis of semi-transparent photovoltaic in office buildings. The Authors addressed the issue of daylighting schemes and solar energy conversion systems and their important role in producing clean energy, reducing peak demand, reducing cooling demand and minimizing the total energy cost in given building. For that purpose, a semi-transparent PV system is integrated as a part of building façade. The paper studied the thermal and visual properties of such system. By using the recorded results, essential parameters pertaining to the power generation, thermal and optical characteristics of the PV system were determined. The findings showed that such an integrated system could produce electricity and cut down electric lighting and cooling energy requirements to benefit the environmental, energy and economic aspects.. Yoon et al., 2011. In this paper, a dye-sensitized solar cell technology was used as one of the most promising technologies in the area of. building integrated PV systems. Such technology enables different level of transparency, which makes it particularly Application of transparent dyesuitable for window application in buildings. Authors of this paper investigated the relationship between different levels sensitized solar cells of transparency and the efficiency of such solar cells. Their research has shown that the lower transparency of such cells to building integrated results in higher efficiency and it does not necessarily translate into higher overall efficiency of the building. The Authors photovoltaic systems summarize that the optimum conditions/parameters should be carefully designed in terms of simultaneously energy generating and daylighting. Another finding is such that the different orientations of wall affect the optimal parameters of such PV cells. Sun et al., 2012 Optimum design of shading-type. In this paper one can read that the building integrated photovoltaics systems can simultaneously operate as energy generators as well as shading and insulation devices. The Authors addressed the research gap of a limited knowledge. 36.

(37) building-integrated photovoltaic claddings with different surface azimuth angles Hwang et al., 2012 Optimization of the building integrated photovoltaic system in office buildings— Focus on the orientation, inclined angle and installed area Lu and Law, 2013 Overall energy performance of semi-transparent single-glazed photovoltaic (PV) window for a typical office in Hong Kong. about the impact of orientations and inclinations of PV modules on the combined energy output in terms of energy savings and energy generated. A case study was designed and investigated for climatic conditions of Hong Kong. The results reveal that building integrated PV systems can bring benefits simultaneously on energy generation and saving level. This study addressed the potential of building integrated PV system to cover an electrical load in office building located in Korea. The Authors considered different inclination angles and directions of PV modules. The available solar insolation has been calculated for various facades of two office buildings. The effect of shading resulting from modules self-shading as well as shading from nearby buildings was also considered. The results show that PV system can cover approximately 1-5% of the building annual load. However, the Authors make a remark that not total technical potential for PV system has been considered in their work. The Authors of this paper developed a general method for analyzing the thermal and power behavior of semitransparent photovoltaic windows used in office buildings in Hong Kong. To estimate the energy performance of such system a total heat gain, power output and daylight illuminance are taken into the consideration. For the simulation purposes four years of weather data from nearby meteorological station was used. The overall annual electricity benefits from such PV windows are 900 kWh and 1300 kWh for respectively water and air – cooled air-conditioning systems. The Authors highlight the fact that using semitransparent PV glazed windows can not only benefit the building in terms of energy delivered by it also can reduce the cooling load.. Ban-Weiss 2013. et. Electricity production and cooling energy savings from. al., As already indicated the research of building integrated photovoltaics show that such systems can play multiple roles. In this study the Authors considered the possibility of mounting the PV system on the office building roof. The results show that the solar absorbance of the roof can significantly decrease and in consequence the summer roof temperature can be reduced by 5 degrees. In terms of electricity production, the PV system generated about 25% of building daily load in. 37.

(38) installation of a building-integrated photovoltaic roof on an office building Chae et al., 2014 Building energy performance evaluation of building integrated photovoltaic (BIPV) window with semitransparent solar cells. Tse et al., 2016 Performance evaluation and economic analysis of a full scale waterbased photovoltaic/thermal (PV/T) system in an office building Lang et al., 2016. summer. For that particular building the major benefit of employing PV system is in energy generation not reduction of the cooling load. In this paper the Authors investigated the impact on semitransparent PV cells on the energy and optical parameters of typical medium size commercial building in various climate zones. For the purpose of this study such solar cells have been manufactured. Also, the paper in details deal with the optical parameters of the cells in different sun wavelengths. The results of the research indicated that the optical properties of the cells should be adjusted to the local climate conditions to ensure the maximal benefits to the building.. The above referenced paper focused on optical, energy and insulation/shading properties of PV systems. However, it is clear that the hybrid PV/thermal system are superior to their singlehanded alternatives. The efficient use of thermal collector can absorb the excess heat from PV panels and lead to their increased efficiency. In this study the Authors analyzed the benefits of such solution in case of office buildings. The economic analysis reveals that such system is characterized by a positive net present values and should be considered as an investment (at least in a subtropical climate of region of Hong Kong). This paper addresses and important issue of the self-consumption in office buildings which are utilizing PV systems. The. models of self-consumption enable researchers to decouple the economic performance from policy support (for example Profitability in absence of feed-in tariffs). In this study the Authors considered four different types of buildings (residential, commercial each small subsidies: A technoand large) in Germany, Switzerland and Austria. The results indicate that self-consumption is an interesting alternative economic analysis of rooftop photovoltaic for buildings in Central Europe even if there is a lack of PV system regulatory support. The Authors indicate that an self-consumption in 38.

(39) residential and important factor is how the ratio of PV production and electricity demand and how the production curve matches the commercial demand one. buildings Martín-Chivelet & This paper can be considered as a follow-up of the Lang et al., 2016 study. Here the Authors mention how important is Montero-Gómez, the potential of the PV systems integrated with office buildings in reducing the use of the electricity from the grid. The 2017 paper focusses on the importance of matching the PV generation profile with the load in order to reach a 100% selfOptimizing consumption. By doing so a nearly 100% self-consumption can be achieved which improves the buildings self-sufficiency photovoltaic selfconsumption in without energy storage or load management. The paper develops a method for designing the building with integrated office buildings photovoltaics. The Authors show the role of different facades in the local PV production. For Northern hemisphere the recommendation is to first consider the facades that are not facing north. Later system should be designed in such a way that maximizes the production/consumption match. Thür et al., 2018 Smart grid and PV driven ground heat pump as thermal battery in small buildings for optimized electricity consumption Marańda, 2019 Analysis of selfconsumption of energy from gridconnected photovoltaic system for various load. In this paper the authors have shown how the intelligent use of the building thermal masses can increase the energy selfconsumption from a PV system. For that purpose, a simulation model was prepared which considered the: building thermal inertia, PV systems, heat pump and thermal storage (water tank). By applying different control strategies, the use of solar energy increased from 11% to 61%. Also, the running cost of the heat pump decreased. This paper indicates how reasonable control strategies and use of existing technologies can improve the economic performance of PV system.. In this paper Maranda addressed the problem of a bidirectional energy flow in case of buildings with photovoltaic installations. The bidirectional flow results from the fact there exists a mismatch between electricity production from PV panels and building load. The Author points out that the PV systems should be carefully adjusted to the observed local profile in such a manner that the self-consumption is increased. The paper gives an important insight into the methodology of sizing the PV/battery systems for systems of any size.. 39.

(40) scenarios with short-term buffering Satsangi et al., 2019 Real time performance of solar photovoltaic microgrid in India focusing on selfconsumption in institutional buildings Jurasz and Campana, 2019. In this paper a case of India is investigated. The Authors show that in the recent years an exponential growth of PV systems has been observed in India. However, this does not apply to rooftop systems. The Authors assume that this fact results from the lack of incentives for energy storage. Considering above the Authors decided to investigate an issue of special importance in such situation, which is the self-consumption. The study shows that unlike the residential buildings the commercial ones consume the majority of energy when the PV systems are operating. The results show also that the microgrid under consideration has a very high ratio of self-consumption (89%). In this paper a small office building in Poland was considered as a case-study. The Authors investigated the potential of photovoltaic system to: reduce the observed peak load and to reduce the overall cost of electricity. The results show that. The potential of photovoltaic systems to reduce energy costs for office buildings in timedependent and peakload-dependent tariffs Jurasz and Mikulik, 2019. the PV system can minimize the energy total cost by 1.2% to 5.8% (depending on energy tariff). The analysis of residual. Energy selfconsumption from PV systems: estimations for two office buildings in Krakow (Poland). exceeded 1 GWh. The results of this study indicate that the PV systems’ generation profiles (in general) match perfectly. load shows also significant potential of PV system to shave the peak loads, which is of special importance to the Polish power system.. This paper can be considered as a continuation of research on the self-consumption in office buildings with PV installations. In this study, the Authors selected two office buildings located in Cracow. In both cases the annual load. the electricity load profiles in office buildings. It was additionally shown that a 100 kW PV system can cut the peak demand from 171 kW to 169 kW (relatively low production from PV) in January and from 333 kW to 255 kW in June. Installing a PV system with a capacity of over 500 kW results in a complete reversion of load profile and now the highest 40.

(41) demand is observed not in summer but in winter. The Authors conclude also that the technical potential of PV systems might be much smaller than assumed in the analysis. Aguacil et al., 2019 Active surfaces selection method for building-integrated photovoltaics (BIPV) in renovation projects based on selfconsumption and self-sufficiency Luthander et al., 2019 Graphical analysis of photovoltaic generation and load matching in buildings: A novel way of studying selfconsumption and self-sufficiency. In this work, the Authors address the problem of misconceptions with regard to the operation of rooftop PV systems in urban areas. A methodology is developed to select appropriate building surfaces, which shall be used for PV systems during building retrofitting process. Based on this methodology a trade-off is made between the self-consumption and self-sufficiency of a building. The methodology also considers the storage needs resulting from different PV system orientations. The result show that for buildings with higher façade to roof ratio it is mandatory to consider wider range of irradiation values (600-800 kWh/m2). The results indicate that retrofitting projects should be addressed on individual buildings level. The paper by Luthander et al., investigated the issue of on-site renewable energy supply. In particular, the solar energy converted into electricity by photovoltaics. The Authors admit that the matching potential is most commonly expressed by using the load matching indicators (self-sufficiency and self-consumption). The Authors propose the energy matching charts, in terms of both time and size. The further simulations show that energy storage has significantly larger potential to increase the matching than load shifting. Authors conclude that the PV systems may help the buildings to reach the nearly zero energy buildings requirements however application of storage makes achieving this goal much more likely.. 41.

(42) 2.2.2. Electrical vehicles in buildings Buildings are intrinsically connected to their occupants. They can be either their homes or places that they visit occasionally or on a daily basis (like workplace). Since the public transport is quite often far from perfect, or it is not an option of personal choice then the part of journeys is made by using private/shared vehicles. Currently, internal combustion engines power the majority of cars and refueling is realized by using conventional fuels. With the advent of electrical vehicles, it is obvious that the refueling patterns will be changed and they will impact the operation of the power systems and also the buildings. Therefore, in this section a subset of papers that dealt strictly with electrical vehicles in the context of build environment is presented. Table 2.2 summarizes recent relevant works.. 42.