Nemiah Valley photovoltaic-diesel mini-grid: System performance and fuel saving based on one year of monitored data

Abstract

Abstract-Canada's first battery-free photovoltaic (PV)-diesel mini-grid was installed in the Nemiah Valley of British Columbia, Canada in the fall of 2007. Since loads in this community are relatively small (peak load of ≈75 kW), photovoltaic penetration on the mini-grid is much higher than what has been achieved in any large-scale centralized grid: the 27.36 kW of PV represent 36% of peak load, and supply roughly 11% of the electricity used in the community on a yearly basis. The goal of this research was both to assess the performance of this PV-diesel mini-grid over a one year period, as well as to highlight some of the lessons learned and inform the design and operation of other such systems. In particular, this case study examined fuel savings that were achieved through a number of modifications to a pre-existing mini-grid, including the addition of photovoltaics, the removal of a dump load, the reconfiguration of the commercial load feeder and the use of a smaller genset during weeknights and weekends. The fuel savings achieved amount to about 26,000 L per year, or a reduction of ≈25% over business-as-usual. With respect to photovoltaic systems performance, the main issue encountered was the occurrence of conditions under which PV output would, if not curtailed, exceed system load. It was estimated that the PV system would deliver about 10% more energy on a yearly basis if all of its output could be absorbed (as in the case of connection to a large, centralized grid). Given that this effect will worsen as PV penetration levels are pushed beyond this system's, a number of avenues for mitigating this loss are discussed