Sun on the roofs: Study about solar potential of the roofs in existing buildings

Abstract

The purpose of this master’s thesis is the study of the solar potential of the roofs in existing buildings in Europe and the determination of the main factors that affect the use of solar systems together with their environmental impact and financial analysis. In order to carry out this goal, three variables that can affect the implementation of solar photovoltaic (PV) and thermal systems are included in the analysis. They are latitude, type of building and subsidy or support received from the government. Barcelona, Berlin and Gothenburg are the three cities chosen. These cities are located in south, central and north part of Europe respectively and the type of support system differs from each other. Four types of buildings are included in the analysis and they are divided into the ones for domestic use (single-family houses and block of flats or multi-family buildings) and non-domestic use (commercial centers and industrial buildings). The methodology followed is divided in two parts: first, the analysis process to study the power installed on the roofs of the buildings and second and using the results of the previous phase, the evaluation of the environmental benefits in terms of CO2-eq emissions savings and, the economical feasibility of the systems. In the first stage, it has been determined flat roofs have better solar roof quality and systems performance is better in southern latitudes. Concerning the environmental analysis, solar systems reduce CO2 emissions. This contribution is more notable when larger are the cities and when more fossil fuel dependant is the energy mix of the country. In the case of Berlin with more than 20 million tons CO2-eq of savings, results are significantly better than in the other two cases. Studying the economics of the system, investment subsidies have a positive effect when the electricity generated by PV systems is for self-consumption. Contrary, FIT policies gives better results when the electricity is sold in to the grid but they are not decisive for the implementation of solar PV systems. Solar thermal option is not competitive at all compared to the heat produced by gas or district heating (DH). However, results are much better than for photovoltaic even without considering subsidies, when they substitute electricity. In general terms, results are more attractive when solar thermal systems are used in domestic buildings.