Multi-objective optimisation for building integrated photovoltaics (BIPV) roof projects in early design phase

Building-integrated photovoltaics (BIPV) is an excellent renewable energy application for building envelopes. In Australia, BIPV roofing is considered to be promising because of recent major concerns about fire risks of façades. However, the integration of PV into building envelope elements is a complicated process which, if not done properly, may lead to failure of the BIPV system. Therefore, feasible BIPV design solutions need to be examined in terms of life-cycle cost and energy performance from the early design phase of a BIPV envelope project. There have been few investigations of the identification of feasible BIPV design options in the early design phase to enable product selection and parametric tests. This study explores a multi-objective optimization method which formulates feasible BIPV envelope design options which have relatively high energy generation and low life cycle costs to informed decision making. The optimisation process has four segments: data inputs, simulator, optimizer and pareto front based optimised BIPV solutions. The proposed multi- objective optimization process is applied in a BIPV roof application using a case study in Australia with roof sheets and skylights. The results demonstrate seven optimum roof sheet BIPV design solutions and fourteen optimum skylight BIPV design solutions to enable design makers to compare and select the most appropriate. The life cycle cost, life cycle energy, CO2 emissions avoided, net present value, payback period, and levelized cost of energy of BIPV solutions vary based on the BIPV modules, tilt angles and placement locations. The proposed optimization method is a helpful guide for BIPV design professionals to identify suitable BIPV design options in the early design phase instead of relying on rule-of-thumb experience.