Pursuing Cutting-Edge Renewable Energy Projects

Renewable energy from natural resources such as sunlight, wind and water is quickly becoming a critical component of California’s power supply. As a water supplier, the Water Authority pursues a variety of hydroelectric, energy storage, and solar energy projects to help reduce energy costs and stabilize water rates.

Program Focus Areas

Hydroelectric Energy

The Water Authority owns and operates the Rancho Peñasquitos in-line hydroelectricity facility, which has been providing clean, renewable energy to the electric grid since December 2006.

The power is generated using a single 4.0-megawatt horizontal turbine. The facility provides an average of 10,000 megawatt-hours (MWh) of renewable energy annually, enough electricity for approximately 2,400 San Diego households.

The Rancho Peñasquitos facility not only acts as a source of clean energy for San Diego, it also offsets about $1 million annually of the Water Authority’s energy costs at the Claude “Bud” Lewis Desalination Plant through SDG&E’s Renewable Energy Self-Generation Bill Credit Transfer (RES-BCT) Program tariff. The hydroelectric power displaces electricity from fossil fuel power plants eliminating the equivalent of greenhouse gas emissions from more than 900 passenger cars.

Solar Energy

The Water Authority used a power purchase agreement to install photovoltaic solar panels at its headquarters in San Diego, its operations center in Escondido, and at the Twin Oaks Valley Water Treatment Plant in 2010.

The power purchase agreement with a developer enabled the Water Authority to install solar power systems at no cost. The developer owns and operates the systems and sells the energy to the Water Authority at a reduced rate with an annual price escalation factor.

The solar power systems installed at the Water Authority’s Kearny Mesa headquarters, Escondido Operations Center and Twin Oaks Valley Water Treatment Plant produce an estimated 2.5 million kilowatt-hours of renewable energy each year. The 20-year agreement with CleanCapital will save the Water Authority approximately $3 million over the lifetime of the agreement and supports the agency’s commitment to sustainability. 

Energy Storage

In 2017, the Water Authority received a $1 million incentive from the California Public Utilities Commission to build an energy storage project that is expected to save the Water Authority nearly $100,000 per year in energy costs by using commercial-sized batteries at the Water Authority’s Twin Oaks Valley Water Treatment Plant.

The batteries store low-cost energy – either excess solar energy or retail energy purchased during off-peak hours – for later use during high-demand periods, maximizing the value of energy generated at the treatment plant. The energy storage project was developed through a no-cost Power Efficiency Agreement with ENGIE Storage to install a 1 megawatt/2 megawatt-hour energy storage system at the Twin Oaks Valley Water Treatment Plant.

ENGIE Storage owns, operates, and maintains the system for 10 years or until 2029, after which the Water Authority can choose to extend the agreement, purchase the batteries, or have ENGIE Storage remove the batteries and return the site to its original condition.

San Vicente Energy Storage Facility

One of the most promising pumped energy storage solutions in California is the San Vicente Energy Storage Facility under consideration in San Diego County. As proposed, the potential project could store 4,000 megawatt-hours per day of energy (500 megawatts of capacity for eight hours). This potential project would have a small footprint by taking advantage of the existing San Vicente Reservoir owned and operated by the City of San Diego. The Water Authority, which owns approximately two-thirds of the reservoir’s water storage capacity, is partnering with the City on this potential project.

The project would create a small upper reservoir above the San Vicente Reservoir, along with a tunnel system and an underground powerhouse to connect the two waterbodies. The powerhouse is proposed to contain up to four reversible pump turbines. The upper reservoir would be in an area with no natural lake or stream. During off-peak periods – renewable supplies from wind and solar facilities exceed demand – turbines would pump water to the upper reservoir where it would act as a battery of stored potential energy. During peak energy use, the system would discharge energy as water from the upper reservoir flows downhill through the turbines. The exchange between the two reservoirs would not consume water.

Planning and investing for large-scale energy projects like the San Vicente Energy Storage Facility takes time. It is important to begin undertaking the necessary steps now to ensure this potential project can help California realize a clean energy future.