Tesla has completed the installation of a 2MWh Powerpack system for Pacific Gas & Electric in Browns Valley near San Francisco, making it the second utility-scale Powerpack project the company has completed in California.
The Browns Valley project, designed and installed by Cupertino Electric, is made up of 22 Tesla Powerpack systems which use battery cells manufactured at the company’s Gigafactory plant in Nevada. Total capacity of the system is half a megawatt — enough to power 380 homes for up to four hours. Demand can shift from moment to moment. Batteries can respond to such transitory needs instantaneously in a way that a peaker plant cannot.
The California legislature requires utility companies to use storage solutions for excess electricity produced by solar panels during the day so it can be used later when demand spikes — usually in the late afternoon and early evening hours when people are getting home from work. This approach, known as “time shifting” — reduces the need to build so-called peaker plants, generating facilities that sit idle most of the day but get fired up whenever extra electricity is needed.
Electrical storage is not a new idea. Since 1984, PG&E has relied on a pumped storage facility in the Helms Valley high up in the Sierra Nevada mountains east of San Francisco. That installation uses excess electricity to pump water uphill during the day so it can flow back downhill later, turning hydroelectric turbines as it falls. It has a total capacity of 1.2 megawatts.
But such projects require years of planning, permitting, and construction. So do natural gas fired facilities. The allure of battery storage is that it can be completed quickly and can be sited close to the grid structure it serves. “It’s pretty modular — you can scale up and down as you need,” said Mike Della Penna, PG&E’s project manager for the Browns Valley installation.
Battery storage is still relatively expensive (neither PG&E nor Tesla would reveal the cost of the Browns Valley installation reports the SF Gate), but the speed with which battery storage facility can be designed, built, and brought online helps to offset some of that additional cost. Taking a longer view, firing up a peaker plant is expensive. Eliminating that cost over a period of years will help balance out the initial investment.
And battery costs are dropping faster than most people anticipated. The second generation Tesla Powerwall home battery system came on the market barely one year after the original went on sale. It has double the capacity but actually costs less because the inverter is built in. Tesla does not reveal the cost of its grid scale Powerpack batteries, but it is a safe assumption that a similar drop in price applies to them as well.
Grid scale battery storage is still in its infancy and all stakeholders are exploring the least expensive and most efficient way to make use of it going forward. PG&E and Tesla are working together on a pilot project that uses Powerwall batteries in homes and businesses in the Bay Area. The total capacity of the distributed storage will be equal to that of the Browns Valley project. PG&E will be able to study the performance of both systems — one distributed and one centralized — to learn how each benefits the local grid. “They’re each with their own challenges and opportunities,” Della Penna says. “We’ve structured it so we’ll have a lot of really good learning here.”
Elon Musk has said he expects the storage battery business to be larger than Tesla’s automobile business one day. The lessons learned from projects like Mira Loma and Browns Valley will become the foundation for the Tesla’s grid storage business in the future.
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