Methodology for Optimization of Stand-Alone Solar Photovoltaic Systems

The concept of Net-Zero Energy in building refers to a building which has an annual balance of energy flow at the utility meter of zero. The concept implies that the building may consume energy from an external provider at times in order to satisfy the building demands, but at other times it must produce enough on-site energy to compensate for this energy. The use of renewable energy technologies is implicit as the source of energy to compensate for any energy used from an external provider. Solar photovoltaic is a proved technology for achieving Net-Zero Energy building but economic factors has limited its broad use. The design stage of a solar photovoltaic project is critical to make a project feasible. In the design stage, the equipment sizing must be optimized in order to reduce the initial capital cost and, therefore, improve the economics of the project. For houses, which is the focus of this paper, a stand-alone solar photovoltaic system must supply the house energy demand at all times since it is not connected to the electric grid. As a means to size the system, data of solar energy availability must be used to ensure that the system will provide enough energy to satisfy the energy demand as well as provide energy to charge the batteries that will provide the energy required when the solar energy is not available. In this paper, a methodology to optimize the size of the photovoltaic array and the battery bank is proposed. The methodology accounts for Typical Meteorological Year data (TMY3) to ensure that the system, based on accepted statistical data, will be able to satisfy the energy demand at all times. An example that uses energy demand data obtained from the simulation of a house using the software EnergyGauge is used to illustrate the implementation of the methodology.