Autonomous energy system of a remote house using renewable energy sources

I. Gelegenis, Autonomous energy system of a remote house using renewable energy sources, Diploma thesis, July 2022.



In this Diploma Thesis, the technical feasibility and the economy of an autonomous energy system to supply a remote house in Greece by the use of renewable energy sources (RES) is in depth investigated. By the term “remote” we define a house lying away from the available energy networks (electrical network, natural gas supply network, district heating network etc.); in this sense the house should anyway be autonomous by using one from two alternative means: (a) by either using conventional fuels or (b) by using RES. The second possibility (b) is exactly the subject of the present Thesis, while the first possibility (a) constitutes the basis for the economic evaluation of the autonomous RES system. Due to the significant variety of weather conditions across the Country (eg. when moving from the South to the North we have at first the warm zone A where climate is mild, reaching finally to the colder zone D where extremely low temperatures prevail in winter time and the heating needs are many times greater), the case studies approach is selected as the appropriate research method. To this aim, an assumed typical 100 m2 house is examined to become autonomous at two regions at these extreme cases, namely Ierapetra (it belongs to zone A) and Florina (zone D). The heating and cooling energy needs required for the Energy Study are resulted by the use of an appropriate software package (TEEKENAK), while the assumed profile of the electrical load is based on published results of statistical research. The conventional system, which is used for comparison purposes, constitutes of a diesel generator (in combination with batteries and an inverter), and oil boiler for space heating and for production of sanitary hot water. On the other hand, the RES system, which arises as a result of techno-economic optimization, comprises a hybrid electrical system combining photovoltaic station with a wind generator, solar collectors for the production of sanitary hot water and a biomass boiler for space heating. By applying the presently prevailing energy prices (which are very volatile at this period) we found out that the RES systems for both case studies -although much more expensive at their initial costs- are significantly more economical than the conventional systems, achieving lower levelized energy costs for both thermal and electrical energy. So, at Florina the conventional levelized energy prices are 0.1853 €/kWhth and 0.6469 €/kWhe respectively, while by the use of RES system these are further decreased to 0.1080 €/kWhth and 0.4194€/kWhe correspondingly. The same happens with Ierapetra, where the conventional levelized energy prices are 0.2389 €/kWhth and 0.6174 €/kWhe , and by the use of RES system these are further decreased to 0.1820 €/kWhth and 0.3265 €/kWhe. In the same context, the over cost for the RES system is paid back very soon (within 5 years, by assuming a 7% discount rate) and the achieved internal rate of return (IRR) on this over cost is in the range of 25% for both cases (26.5% for Florina and 24.9% for Ierapetra). Since these results refer to two extreme cases along the Country (which had been selected as representative to cover the whole Country), we could generalize this encouraging outcome (achievable IRR of the RES system in the range of 25% all along the Country), a fact which is very encouraging for the development of RES driven autonomous houses in remote -from the networks- areas in Greece. This very positive result can be attributed to (i) the high conventional energy prices that the houses in remote areas should cope with (ii) the significant RES potential all along the Country as a whole (iii) the economy of RES technologies which can nowadays compete the conventional energy systems without the need of grants and (iv) the recent increase of conventional energy prices. As related to the last fact, steadily increasing energy prices were noticed during the period of elaboration of this Thesis; if we had applied the prices prevailing at the starting period of this research, the calculated IRR values would be a little lower, namely 18.0% for Florina and 19.2% for Ierapetra, which are anyway still economically attractive.

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