Yenilenebilir enerji kaynakları ile mikro şebeke tasarımı ve optimum çözümünün HOMER ile incelenmesi
Design and optimal configuration of renewable sources grid-connected microgrid at the rural area in Turkey by using HOMER
Yazar: SEZEN BEYARSLAN
Danışman: PROF. DR. BELGİN TÜRKAY
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Elektrik Mühendisliği Ana Bilim Dalı / Elektrik Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2021
Konu: Elektrik ve Elektronik Mühendisliği = Electrical and Electronics Engineering

Özet:
Güvenilirlik, elektrik kalitesinin en önemli parametrelerinden biridir. Yenilenebilir enerji çevre dostu olmasına rağmen, tek bir tür yenilenebilir enerji kaynağının güç çıkışı 24 saat boyunca yükleri karşılayamaz. Bu nedenle enerji depolama sistemleri ile rüzgar türbini, hidroelektrik santrali, fotovoltaik panel gibi yenilenebilir enerji kaynaklarının mikro şebeke adı verilen hibrit bir enerji sisteminde birleştirilmesi gerekmektedir.
Uygun depolama sistemleri ve çeşitli yenilenebilir enerji kaynaklarını içeren hibrit enerji sistemlerinin tasarlanması, dengeli ve güvenilir elektrik enerjisi sağlar. Hibrit enerji sistemleri, güvenilirlik dezavantajı olmayan uygun depolama sistemi çözümü sayesinde, fosil yakıtların yanmasını azaltarak küresel ısınmanın başlıca nedeni olan karbon emisyonunu azaltmaktadır. 
Yenilenebilir enerji kapasitesinin yetersiz kaldığı özellikle geceleri enerji depolama sisteminin önemi daha da belirgin hale gelmektedir. Pil depolama sistemleri yaygınlıkla kullanılmakla birlikte, pil depolama sistemlerine olan bağımlılığı azaltmak için yakıt hücreleri de depolama sistemi olarak kullanılmaktadır. Bazı hibrit enerji sistemleri, elektriksel güvenilirliği sağlamak için dizel jeneratör kullanmayı da tercih edebilir, ancak atmosfere ve çevreye zarar verirler.
Bu çalışmanın amacı, şebekeye bağlı bir köyde ekonomik bir çözümle elektrik maliyetini ve karbon ayak izini azaltmaktır. Bu nedenle köy için günlük güç ihtiyacı (talep), tepe yük, güneş radyasyonu ve rüzgar hızı verileri toplanmıştır. Daha sonra elektrik yükü ve fotovoltaik modüller (PV), rüzgar türbinleri, küçük hidroelektrik santrali, batarya veya elektrolizör, yakıt hücreleri ve hidrojen depolamanın herhangi bir kombinasyonundan oluşan optimal bir mikro şebeke sistemi tasarlanmıştır. Analizler için bileşen fiyat bilgisi IRENA (Uluslararası Yenilenebilir Enerji Ajansı) 2019 yenilenebilir üretim maliyetinden alınmıştır. Hem şebeke katkılı hem de şebekeden bağımsız sistemler için analizler HOMER (Enerji Kaynakları için Hibrit Optimizasyon Modelleri) programı kullanılarak yapılmış ve kaynakların gerilim seviyeleri optimize edilmiştir. 
Maliyetleri sırasıyla 429.000 $, 1.800.000 $ ve 3.300.000 $ olan 330 kW E33 türbin, 1500 kW Leitwind LT90 türbin ve 3000 kW E82 E4 türbin olmak üzere 3 tip rüzgar türbini arasından en uygun olanı seçilerek analizler yapılmıştır. Analizler sonucunda çok sayıda Enercon E33 330 kW rüzgar türbininin yetersiz kapasitesi nedeniyle elektrik talebini karşılamak için kullanılması gerektiği gözlemlenmiştir. Bu çok sayıda E33 sadece enerji maliyetini olumsuz etkilemekle kalmadı, aynı zamanda köyün büyük rüzgar türbini tesisi kurmak için yeterli yeri yok. Enercon E82 3000 kW rüzgar türbinlerinin kapasitesi çok büyüktü ve uygulanabilir bir çözüm değildi. Bu nedenle bu çalışmada en uygun rüzgar türbini olarak 1500 kW LT90 seçilmiştir. 
Çevresel kaygılarla tasarlanmış şebekeden bağımsız sistemde normal çalışmada hidroelektrik santral, fotovoltaik paneller ve rüzgar türbinleri yük talebini besler. Bu sistemde batarya kullanımı ayrıca analiz edilmiştir. PV ve rüzgar türbininden gelen fazla enerji elektrolizöre beslenir. Elektrolizör hidrojen üreterek hidrojen tankında depolanır, PV, hidro ve rüzgar türbini yükü karşılamadığında yakıt hücresi yedek sistem olarak devreye girer. Yakıt hücreleri hidrojen tüketir ve talep edilen elektriği karşılar. Şebekeden bağımsız sistem %1, %5 ve %10 kesinti kapasitesi ile tasarlanmıştır. Analiz sonuçlarına göre %10'luk kesinti kapasitesi daha ekonomik olmasına rağmen elektrik sürekliliği için uygun değildir, bu nedenle daha uygulanabilir, ekonomik ve kabul edilebilir bir çözüm için %5'lik kesinti kapasitesi seçilmiştir. 
Ekonomik açıdan optimum sistemi bulmak için tasarlanan şebeke katkılı sistem, Hidroelektrik santral, PV ve 1500 kW LT90 rüzgar türbini ile yedek ve depolama sistemi olmadan tasarlanmıştır. HOMER sisteminde herhangi bir şebeke kullanım sınırlaması olmaksızın, şebeke bağlantılı sistem düşük fiyatları nedeniyle şebeke elektriği kullanmayı tercih etmiştir. Amacımız sadece ucuz elektrik sağlamak olmadığı için, karbon emisyonlarını azaltmak için çoğunlukla fosil yakıtlı kaynaklardan oluşan şebeke kullanımı sınırlandırılmıştır.
Ayrıca, PV ve rüzgar türbini maliyetlerinin beklenen oranlarda düşürülmesi, şebeke elektrik fiyatlarının arttırılması, izin verilen kıtlık kapasitesinin değiştirilmesi gibi bireysel ve çalışma durumlarının kombinasyonları oluşturularak hem ekonomik hem de çevre dostu çözümler üretilmiştir.

Abstract:
Reliability is the one of the most important parameters of electrical quality. Despite renewable energy is environmentally friendly, the power output of a single type of renewable energy resource cannot meet the loads for 24 hours. For that reason, energy storage systems and renewable energy resources such as wind turbine, hydroelectric power plant, and photovoltaic panel need to be combined together in a hybrid energy system called micro-grid. 
Designing hybrid energy systems, which include appropriate storage systems and a variety of renewable energy resources, provide balanced and reliable electrical energy. Thanks to the appropriate storage system solution without any reliability disadvantages, hybrid energy systems reduce the carbon emission, which is the principal cause of global warming, by reducing the combustion of fossil fuels. 
The importance of energy storage system becomes more evident, when renewable energy capacity is insufficient, especially at nights. Battery storage system solutions are commonly used in hybrid system. Fuel cell systems are used to reduce the dependence on requirement of battery storage systems. Some hybrid energy systems can also prefer using diesel generators to ensure electrical reliability, but they harm to the atmosphere and the environment. 
The aim of this study is to reduce the cost of electricity and carbon foot print with an affordable solution on a grid connected village. Therefore, data such as daily power requirement (demand), peak load, solar radiation and wind speed were collected for the village. Then an optimal microgrid system, which consists of electrical load, and any combination of photovoltaic modules (PV), wind turbines, small hydroelectric power plant, as a storage system electrolyser, fuel cells and hydrogen storage and battery system, has been designed. For analyzes, components price information was taken from the IRENA (International Renewable Energy Agency) renewable generation cost 2019. Analyzes for both on-grid and off -grid systems have been performed by using HOMER (Hybrid Optimization Models for Energy Resources) program and the penetration levels of resources have been optimized. 
Analyzes have been made to select the most proper one among 3 types of wind turbines such as 330 kW E33 turbine, 1500 kW Leitwind LT90 turbine and 3000 kW E82 turbine with costs of $429.000, $1.800.000 and $3.300.000, respectively.  As a result of the analyzes, it has been observed that a large number of Enercon E33 330 kW wind turbines had to be used in order to meet the electricity demand due to its insufficient capacity. 
This large number of E33 not only affected cost of energy negatively, but also village has no enough place to set up large wind turbine plant. The capacity of Enercon E82 3000 kW wind turbines was very large and not a feasible solution. For that reasons 1500 kW LT90 has been selected as the most appropriate wind turbine in this study. 
In normal operation on off-grid system designed only with environmental concerns, hydroelectric power plant, photovoltaic panels and wind turbines feed the load demand. The excess energy from PV and wind turbine is fed to designed storage system. In this Project there have two designed and analyzed storage system. One is, the excess energy from PV and wind turbine is fed to Electrolyser produced hydrogen and stored in hydrogen tank, when PV, hydro and wind turbine don't satisfy the load, the fuel cell is activated as a back-up system. Fuel cells consume hydrogen and meet demanded electricity. Second option is, off-grid system also designed with battery as an alternative storage solution. 100 kWh capacity Lithium-ion battery has been selected for high energy capacity. When PV, hydro and wind turbine can not meet the load, battery system is activated for demanded load.
For storage system analyzes have been made to select proper and affordable system. Storage system components for one of designed system is electrolyser, hydrogen tank and fuel cell. Their costs are given respectively, 2000$ per kW, 715$ per kg and 3000$ per kW. One of designed storage system is lithium-ion battery and it cost 450$ per kWh. When comparison has been made for two type of storage system, it is obvious that battery storage system is much cheaper than fuel cell system, because of the low component price. For that reasons 100 kWh capacity lithium-ion battery has been selected as the most appropriate storage solution in this study. 
Off-grid system has been designed with 1%, 5% and 10% shortage capacity. According to the results of analyzes, even though 10% shortage capacity is more economic, it is not appropriate for electricity continuity, for that reason 5% shortage capacity was selected for more feasible, affordable and acceptable solution. 
Chosen acceptable solution as an economically for off-grid system was 1500 kW Leitwind90 wind turbine, lithium-ion battery and %5 shortage capacity. For satify the village demand, analyzes result of usage of components for off-grid system were given respectively. 7293 kW PV, 5 pieces (7500 kW) wind turbine, 22400 kWh battery, 3157 kW converter and 212 kw hydro power plant. The cost of unit energy of this system was 0,249 $. When the most economic result was analyzed, the number of wind turbine number was decided to limited at 3. Analyzes result of limited wind turbine was given following, 11131 kW PV, 3 pieces (4500 kW) wind turbine, 26600 kWh battery, 3621 kW converter and 212 kW hydro power plant. The cost of unit energy of this system was 0,269 $. Cost difference between those two system was %7.
On-grid system, created only with economic concerns, has been designed with Hydroelectric power plant, PV and 1500 kW LT90 wind turbine without any back-up storage system. Without any grid usage limitation on HOMER system, grid connected system preferred to use grid electricity because of its low prices. Since our aim is not just to provide cheap electricity, the use of grid, which is mostly fossil fueled sources, has been limited in order to reduce carbon emissions. 
Chosen most environmentally friendly solution for on-grid system was 4000 kW grid limitated system and 1000 kW sell-back limited system. Related analyzes results was following 1615 kW PV, 7 pieces (10500 kW) LT90 wind türbine, 212 kW hydro power plant and 723 kW converter. The cost of unit energy of this system was 0,113 $ and yearly carbon emission was 2.471.529 kg. When the most economic result was analyzed, the number of wind turbine number was decided to limited at 3. Analyzes result of limited wind turbine was given following, 17812 kW PV, 3 pieces (4500 kW) LT90 wind türbine, 212 kW hydro power plant and 1964 kW converter. The cost of unit energy of this system was 0,167 $ and yearly carbon emission was 2.312.578 kg. With limited wind turbine, electrical energy has been mostly produced in PV. It caused price difference between two analyzes.  
Furthermore, both economic and environmentally friendly solutions were produced by creating individual and combinations of study cases such as increasing 25% solar radiation rate, 25% wind speed and 25% stream flow rate. Off-grid sensitivity analyzes have been performed for all renewable energy resources. Sensitivity analys was performed for reason that when renewable energy potential increased 25%, in order to catch on-grid system prices. 
As a result of sensitivity analyses, 25% increase in wind speed shows the most positive effect on economical perspective among the renewable energy sources. Analyzes result of limited wind turbine was given following, 6067 kW PV, 3 pieces (4500 kW) LT90 wind türbine, 212 kW hydro power plant, 21000 kWh battery and 4771 kW converter. The cost of unit energy of this system was 0,220 $. The cost differences between current condition and 25% increased wind speed analyzes was 18%.
To conclusion of the study was even increased renewable energy sources potantial at off-grid system, it has been not feasible like grid connected hybrid system for economically. In this Project grid connected 4000 kW grid limitated and 1000 kW sell-back limited hybrid system was chosen, as both economic and environmentally friendly solution was chosen as a feasible and affrodable system.