Rather than rebuild distribution lines damaged by fire, PG&E is working with BoxPower to install a renewables-based microgrid to provide clean, resilient power for customers in Briceburg, California. The solar + storage system is the first of 20 proposed for development through PG&E’s new Remote Grid Initiative.
Briceburg, California is a picturesque community near Yosemite National Park in Mariposa County. In 2019 the Briceburg Fire burned 5,563 acres in the area, damaging electrical distribution lines and five customer meters, and interrupting Pacific Gas and Electric Company (PG&E) service to the community. In response, PG&E brought temporary diesel generators online to meet Briceburg’s power needs. The historical line route is challenging to rebuild through the last 1.3 miles of rugged, High Fire Threat District terrain. So instead, the utility is working with BoxPower to install a renewables-based remote microgrid system to restore power to these customers without the need to rebuild the overhead line.
Beyond mitigating wildfire risk, the on-site power system will improve the community’s energy resilience while lowering greenhouse gas emissions with the solar + propane backup system providing up to an estimated 89 percent renewable energy.
This remote hybrid system is designed, installed, and operated by BoxPower and owned by PG&E. It has a solar array consisting of a nominal PV power of 36.5 kW and a 69.12 kWh lithium ferro phosphate battery bank. It includes 27.2 kW of continuous power output and a surge capacity of up to 48 kW. The system has two integrated 35 kVA propane prime power generators and a fire suppression system to protect the hardware. PG&E and BoxPower will be able to monitor and control the system via satellite, with remote performance monitoring, reporting, and automated fuel delivery capabilities.
Microgrid Modelling for Optimal Results
The team kicked off the design process with a site-visit to determine the meteorological conditions at the deployment site. This was essential, according to BoxPower’s Director of Applications Engineering Alexander Asante, in order to determine the solar access and the minimum number of solar panels needed to meet a target renewable fraction of 70% in year 10 as required by the PG&E request for proposal (RFP).
They were able to determine the ideal location for the containerized hybrid energy system using a solmetric SunEye and uploaded the shading data into PVSyst to determine the net production from the solar panels. Then engineers imported the annual available energy output from the PV into HOMER for a microgrid analysis.
The team determined the final system configuration after a multi-year techno-economic analysis in HOMER Pro. By accounting for a 2% annual load growth, the projected load profile in the tenth year was used to determine the minimum combination of photovoltaic (PV) panels, inverters and batteries required to ensure that 70% of the energy delivered by the standalone power system on an annual basis is derived from renewable sources.
The optimization model also factored in the inevitable decline in efficiency of the solar array by applying a 0.6% annual degradation rate to the monocrystalline silicon PV panels used for the project. With the help of HOMER’s Modified Kinetic Battery Model, the model factored in the effects of time, temperature and cycle fatigue on the degradation of the batteries. The combination of PV, inverters, batteries and generators from the optimization results in HOMER were then translated into a BoxPower containerized system.
PG&E Builds a Portfolio of Remote Grid Systems
The Briceburg microgrid project is one of the initial remote grid installations PG&E will deploy as part of its 2021 Wildfire Mitigation Plan (WMP). The utility set a projected target of 20 operational remote grid sites by the end of 2022, according to its plan submitted to the California Public Utilities Commission.
In a public regulatory filing, PG&E said that it has identified the potential for “an eventual portfolio of several hundred Remote Grid line segment opportunities in total… [that] would serve a small but significant number of locations at the edge of the distribution system where energy use is low, but delivery infrastructure challenges are high.”
Across PG&E’s 70,000-square-mile service area, there are pockets of isolated small customer loads served today by long electric distribution lines. In many circumstances, these lines cross High Fire Threat District areas. The energy provider is exploring the efficacy of reducing fire ignition risk by deploying remote grid projects.
As outlined in PG&E’s 2021 Wildfire Mitigation Plan, a Standalone Power System (SPS), or Remote Grid, is a new utility service concept that PG&E is developing using decentralized energy sources and utility infrastructure for permanent energy supply to remote customers as an alternative to energy supply through hardened traditional utility infrastructure.
PG&E is providing initial Remote Grid services to willing customers and using the results of those initial installations to refine Remote Grid costs and technology configurations. These initial Remote Grid projects will serve as a testbed to aid in the development of the policies, tariff structures and operating procedures necessary to integrate remote grids as a feasible product for wires elimination.
PG&E is targeting 20 operational remote grid sites by the end of 2022 with additional sites in High Fire Threat Districts in El Dorado, Madera, Fresno, Tulare, Santa Barbara, Yuba and Sierra counties currently being assessed. The Briceburg Remote Grid system is the first and is slated to come online in May.
PG&E believes these initial sites may be successful from an operational feasibility standpoint while also delivering wildfire ignition risk reduction in a more cost-effective manner.
UL Solutions’ HOMER® Pro is the leading pre-feasibility design software for modeling microgrids, with more than 250,000 users in more than 190 countries. It provides engineering and financial analyses of remote, off-grid and grid-tied complex distributed energy systems, helping reduce financial risk for owners and developers. Learn more about HOMER Pro and download a complimentary trial.