Battery system will be able to light 2,500 homes

Battery system will be able to light 2,500 homes
Considered one of the most advanced microgrids in the world, the UC San Diego microgrid generates 92 percent of the electricity used on campus annually.

One of the largest, most environmentally-friendly, battery-based energy storage systems in the nation will be installed at the University of California, San Diego the campus announced today (Sept. 29).

The 2.5 megawatt (MW), 5 megawatt-hour (MWh) system—enough to power 2,500 homes—will be integrated into the university's microgrid, which generates 92 percent of the electricity used on campus annually and is considered one of the world's most advanced microgrids. A microgrid is a small-scale version of a traditional large power grid that controls energy from clean sources such as wind and solar power, as well as from conventional technology. It can be connected to a larger electric grid, but can also work independently.

"UC San Diego is committed to practices that promote sustainability and innovation, not just on our campus, but in our community and our world," said Gary C. Matthews, vice chancellor for resource management and planning. "Energy storage has the potential to transform the global energy landscape. It can help make more reliable and is critical to a resilient, efficient, clean and cost-effective grid. We are proud to help advance this technology."

Energy storage systems are technologies that convert electricity into another form of stored energy and then convert the energy back to electricity at another time. Energy storage helps integrate intermittent renewable resources, such as solar power, and provides power when it is needed for consumption. The technology is considered key to enhancing grid reliability as well as grid resiliency in the face of adverse conditions.

Energy storage is considered so important that the California Public Utilities Commission (CPUC) decided last year to establish an unprecedented target: 1.3 gigawatts (GW) of energy storage is to be procured and installed by three of the state's investor-owned utilities by 2024. The CPUC's mandate broke new ground by trying to establish a regulatory system in which utilities, third-party storage providers and potentially customer-owned storage assets can play an integrated role.

The 2.5 MW, 5 MWh at UC San Diego was purchased from BYD, the world's largest supplier of rechargeable batteries. BYD's energy storage system uses high performance lithium-ion iron-phosphate batteries that are known for being highly reliable and environmentally-friendly. The company's rechargeable batteries contain no heavy metals or toxic electrolytes and, during the manufacturing process, all caustic or harmful materials are avoided. The batteries are also considered non-explosive and fire-safe, even in direct flames. The company has supplied more than 100 MWh of fixed energy storage stations around the world.

"UC San Diego is renowned for their efforts in green energy production technologies and we are thrilled to partner with them," said Stella Li, BYD senior vice president. "Together, we seek to ensure that renewable power can be utilized as a reliable generation source enabled by environmentally-friendly battery storage."

The 2.5 MW, 5 MWh energy storage system is the latest addition to UC San Diego's portfolio of energy storage devices—one of the most diverse energy storage portfolios of any university in the world. Other devices currently in place include the following with additional energy storage projects being planned as well:

  • 30 kilowatt (KW) ultracapacitor-based energy storage system from Maxwell Technologies, Inc. The system will be combined with Soitec's Concentrated Photovoltaic (CPV) Technology, which is already installed on campus.
  • Second-life battery demonstration site. Although electric vehicle batteries usually only have a vehicle lifetime of eight to 10 years, they still have significant capacity left for alternative uses, such as stationary energy storage.
  • 3.8 million gallon . Waste heat from the plant also is used as a power source for a water chiller that fills a 4 million gallon storage tank at night with cold water. The water is used during the warmest time of day to cool campus buildings.

Once the 2.5 MW, 5 MWh advanced energy is installed in spring 2015, UC San Diego will be eligible for up to $3.25 million in financial incentives through the Self-Generation Incentive Program (SGIP). SGIP is a California ratepayer-funded rebate program that provides incentives for the installation of clean and efficient distributed generation technologies.


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Oct 01, 2014
enough to power 2,500 homes


It isn't.

2.5 MW divided by 2,500 is 1 kW which is far too little for an average home, unless you discount all the space and water heating or cooling.

We're expected to believe that you can "power" a home with 9000 kWh a year, when in most places you actually need 20,000 - 25,000 kWh a year, and the average Californian home too uses 18,000 kWh a year, electricity and heating fuels combined.

Every single time I see an article referring to powering a number of homes, it's always misleading or plain wrong. You can't say you've powered a home with something if you don't actually meet its energy demand.

In reality the system is good for about a thousand homes, or for about a hundred if you intend to power them all day, because there's technically only 2 hours worth of energy at full power in the system.


Oct 07, 2014
Eikka: It's 2500 MW system, meaning that's the peak power it can produce. Yes that means a maximum instantanious draw of 1kW from each of 2500 homes. Unless every single house all put their AC units on at the exact same time you won't meet that - and that's just coming from the batteries. And it's ONLY those times when everyone runs a high load that you even need batteries. During the day the solar should more than meet the consumer demands AND charge the batteries with plenty of headroom.

It will store 5MWh which is 5,000 kWh. Every time you fully charge the batteries that's 5000kWh available to the grid. Assuming every day the sun comes up and every night it goes down, that's 5,000kWh every day that should be available to power the homes every night... when you don't need much air conditioning because... well the sun isn't up.

Do you really use more than 1 kW of power all night when the sun goes down? You and ALL 2500 of your neighbor houses? Well that's why it only meets 92%.

Oct 08, 2014
Unless every single house all put their AC units on at the exact same time you won't meet that


Your microwave oven or your electric kettle uses 1 kW. Even a hairdryer or a vacuum cleaner uses more than 1 kW. An AC would use significantly more than 1 kW. There are plenty of things that require plenty more power, and even the small things add up quite nicely.

Do you really use more than 1 kW of power all night when the sun goes down?


Many people do in the afternoon and early evening when there's neglible solar output. Turn on the oven to cook dinner, and there you have it.

The average Californian home is using an average of 2.05 kW throughout the day with all heating, cooling and electric devices combined.

Oct 08, 2014
Assuming every day the sun comes up and every night it goes down


Yep. Assuming.

But what if it's overcast all day?

Whoops.

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