Grid Decarbonization & Decentralization
California has made significant progress shifting its electricity away from fossil fuels. In 2018, renewables, including hydropower, accounted for 42% of the state’s electricity. To reach 100% clean electricity by 2045 will require an unprecedented transformation entailing higher levels of variable and dispatchable renewable generation and ample energy storage. Aggregated distributed energy resources (DERs) and smart grid solutions to manage this clean energy mix will also contribute.
Featured Research Topics
Variable Renewable Generation
Variable renewable generation resources such as solar photovoltaic (PV) arrays and wind turbines will need to evolve to help achieve the state’s greenhouse reduction goals. For wind, areas of research include more durable and efficient wind turbines for land-based applications, as well as the development of off-shore wind farms with turbines on floating platforms. Research to scale-up PV focuses on materials that can convert higher levels of sunlight to energy and can be installed on a wider range of surfaces and rooftops. Perovskite, a material with the potential for improved efficiency in solar cells, is the focus of a CEC-funded project that seeks to increase production and reduce manufacturing costs to help commercialize the technology.
Zero-carbon Dispatchable Generation
Flexible, dispatchable generation to balance the variability of solar and wind generation is typically provided by cycling fossil fuel power plants—increasing or decreasing a plant’s output or turning it on or off. Geothermal power plants and concentrating solar power (CSP) plants coupled with thermal energy storage have the potential to provide these same grid-balancing services but without the emissions. The potential for flexible geothermal generation is the focus of a CEC-funded project at the Geysers Geothermal Field in Sonoma and Mendocino counties.
Scaling up the use of renewable generation is essential to meeting California’s greenhouse gas emission reduction goals. However, neither wind nor solar can provide energy on a 24/7 basis. Energy storage technologies that can balance the intermittency of renewables include batteries, flywheels, compressed air, pumped hydro, and thermal energy (such as molten salt or ice). However, most commercially-sold energy storage is lithium ion, which has had safety and supply chain issues. Different types of storage are needed to provide an even supply of electricity and ensure the stability of the grid. For example, some technologies can respond more quickly to changing grid conditions than others, while some, although slower to respond, can store larger amounts of energy.
The CEC is focused on diversifying the portfolio of technologies available to the state and increasing the duration of the storage. Most current storage is designed for four-hour duration. The CEC recently awarded eight projects to demonstrate 10 hour of duration by non-lithium ion technologies. The longer duration should provide more benefits to the grid and to the end users. A CEC-funded project is developing a high-efficiency non-flammable, non-toxic battery with the potential for safe, cost-effective distributed energy storage.
Virtual Power Plants
The electricity industry is evolving from a centralized system powered mainly by large remote generating plants to a more decentralized system of smaller distributed energy resources (DERs). DERs can include energy efficiency and demand response resources, renewables, energy storage, electric vehicles and charging facilities, building automation, and microgrid systems. Aggregation of DERs refers to combining multiple DERs from varying locations to act as a single unit that provides or withdraws electricity to and from the grid. For this reason, aggregated DERs are sometimes called “virtual power plants” or VPPs. A CEC-funded project is demonstrating a VPP that consists of solar PV, energy storage, and microgrids located at various sites within the City of Lancaster.