California’s goal is to produce at least 33% of its electricity from renewable sources, and while there’s plenty of sunshine and wind, their production fluctuates throughout the day, sometimes producing more than needed and other times falling short. Regardless of what’s creating the baseload electricity, peaker plants are needed to provide quick demand response. When Southern California Edison (SCE) sent out a request for bids on a 100 megawatt peaker plant, they received over 1800 responses. The winner turned out to be AES, an energy company that builds power plants of nearly every flavor: coal, diesel, gas, oil, wind, etc. What might be surprising is that the chosen technology isn’t any of those - it’s the world’s largest battery.
Most peakers burn natural gas to fire turbine generators. But gas-fired plants have disadvantages: they’re expensive to build, they depend on a fossil fuel whose price is in constant flux, and they take several minutes to come online. After weighing the costs and benefits, SCE decided that battery storage is the most reliable and cost-effective solution, so they awarded AES Energy Storage a 20 year contract to install and operate grid-connected 100 MW “peaker plant” battery bank. Neither AES nor SCE will release the financial terms of the contract.
Image courtesy of AES Energy Storage
Pros and Cons
The cost of a grid-level battery storage unit is roughly comparable to that of a gas peaker plant (depending on size), but with no moving parts, the battery bank needs less maintenance. It also requires no fuel, making its long-term cost of operation more stable and predictable. In fact, it’s almost certain that the cost of gas will increase while the cost of batteries will decrease. A battery bank can respond to power demand almost instantly - less than a millisecond as opposed to several minutes. Where a gas turbine is strictly an energy generator, a battery bank can also store surplus energy. Finally, a battery bank is scalable; more units can be added as needed.
There are drawbacks to batteries, however. First and foremost, they don’t generate “new” energy, they simply store energy that came from other sources such as solar and wind. As such, they’re limited to the amount of energy that’s stored, where a gas peaker plant can generate power indefinitely. Considering the fact that many peaker plants only operate for a few hours per day, this isn’t a big problem. Batteries have a limited lifespan, especially when operated at a large depth of discharge. AES uses efficient, long-life batteries from a variety of sources. Their storage units are technology-independent, so when better batteries become available, they’re easy to incorporate. And although batteries take energy and materials to produce, most are recyclable. (And let’s remember that it takes energy to drill for, transport, and refine natural gas.)
Peakers and Beyond
Rechargeable battery technology continues to improve as consumers demand longer life, reduced cost, and quicker charging for computers, phones, and electric vehicles. Advancements in one area, such as batteries for consumer electronics, affects others. For example, Tesla Motors uses the same Li-ion batteries that are typically found in laptop computers. Variations of Li-ion technology are found in grid-level storage units as well. As these industries feed off of one another, costs will plummet and quality will improve. That’s good news for everyone … except the fossil fuel industry.