Performance Optimization Of Building Integrated Photovoltaics And Its Interaction With Urban Microclimate

Energy and environment are major issues in this world today and are essential for sustainable development. BIPV (Building Integrated Photovoltaics) has progressed in the past years and become an element to be considered in city planning. The paper consists of two parts. Part one discusses the influence of different integration PV roof on the PV power output and the building cooling load/heating load through the roof. Part two deals with the interaction between the BIPV and microclimate in urban environments.The first presents the performance analysis of different PV roofs in the built environment. BIPV has significant influence on the heat transfer of building envelope because of the change of the thermal resistance by adding or replacing the building elements. The four different roofs are used to assess the impact of BIPV on the PV output and building heating and cooling loads, which are ventilated air gap PV roof, non-ventilated (closed) air gap PV roof, close roof mount PV roof and the conventional roof with no PV and no air gap. To evaluate the system performance of the different roofs, the one-dimensional transient models of four cases are derived and experimental apparatus are set up. It shows that the experimental data fit well with the estimated values according to the mathematical models. The experimental and simulation results indicate that PV roof with ventilated air gap is suitable for the application in summer because this integration leads to the low cooling load and high PV conversion efficiency. The PV roof with ventilated air gap has high time lag and small decrement factor in comparison with other three roofs. In winter, PV roof of non-ventilated air gap is more appropriate due to the combination of the low heating load through the PV roof and high PV electrical output. Then, performance optimization of the combination of PV roof with ventilated air gap in summer and non-ventilaed air gap in winter is investigated. An increase of air gap is beneficial to the PV output and the cooling load/heating load through PV roof. The PV electrical output and cooling load falls as the emissivity of roof exterior surface in the air gap increases. And the roof resistance is an important factor to influence the system performance.The second provides the analysis of the interactions of PV and urban thermal environment. On the one hand, three different models of PV power are used to investigate the effects of urban climate on the PV performance. The results show that...