ARCHIVED - Nemiah Valley Photovoltaic-diesel Mini-grid: System Performance and Fuel Savings Based on One Year of Monitored Data

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Authors:
Sophie Pelland and Dave Turcotte, CanmetENERGY
George Colgate, XeniGwet'in Enterprise
Andrew Swingler, Schneider Electric

CETC code: 2011-075

Publication date: 2012-05-29

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 to the supply mix. In addition, the performance of the gensets and PV was studied and compared to relevant benchmarks. The fuel savings achieved amount to about 26,000 L per year, or a reduction of ~25% over business-as-usual. This corresponds to greenhouse gas emissions reductions of about 73 tonnes per year, or the equivalent of taking 21 cars off the road – or about 1 car off the road per household connected to the mini-grid! These fuel savings were realized in part by replacing what was essentially a “dump load” operated to keep the main (95 kW) gensets sufficiently loaded during weeknights and weekends by reduced weeknight/weekend loads supplied by a smaller (30 kW) genset. The load reduction was clearly economical for the Nemiah mini-grid; it highlights the need to better understand genset behaviour at low loading, and to consider alternatives to costly "dump loads" in similar systems. With respect to system 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 were discussed.

For more information about international R&D collaboration on photovoltaic hybrid systems within mini-grids, see the project fact sheet.