Advantages of operation flexibility and load sizing for PV-powered system design

With their autonomous operation and low environmental impact, solar photovoltaics (PV) are an attractive power source for off-grid systems. However, the variable nature of solar energy is not well-suited to power conventional loads. Without careful consideration of the time-dependent power generation of PV, this discrepancy results in systems that are either over-designed and expensive, or compromise reliability. To accelerate the adoption of PV into new areas, it is essential to design PV-powered systems that are persistent, predictable, and affordable. In this paper, we analyze the cost reductions enabled by design optimization through time-flexible operation and improved load sizing. We consider two cases: (i) an idealized reference system, operating 8 h per day at 1 kW, generating an unspecified accumulable output, and (ii) a village-scale PV-powered electrodialysis desalination system, designed to generate 10 m3 of drinking water per day. We found that time-flexible load operation reduced the power system cost of the idealized reference system by 39%, from $2662 to $1628, and designing its electrical load to operate for an optimal period of time enabled an additional cost reduction of 5% (to $1503). For the village-based desalination system, we found that flexible operation paired with expected large decreases in membrane cost (from $150 to $20 per unit) reduced the associated power system cost by 57.6% from $8935 to $3788.