Environment

Electric cars to become mini power plants in California’s energy grid

Like a mini power plant, this electric vehicle can bid on energy in California's wholesale power market
Like a mini power plant, this electric vehicle can bid on energy in California's wholesale power market
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Customer charging up an electric vehicle as part of SDG&E's pilot program
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Customer charging up an electric vehicle as part of SDG&E's pilot program
San Diego Gas & Electric has begun bidding energy resources from fleets of electric vehicles into the state’s wholesale power market
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San Diego Gas & Electric has begun bidding energy resources from fleets of electric vehicles into the state’s wholesale power market
An electric vehicle in SDG&E's pilot program buys energy and charges up when rates are low
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An electric vehicle in SDG&E's pilot program buys energy and charges up when rates are low
Like a mini power plant, this electric vehicle can bid on energy in California's wholesale power market
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Like a mini power plant, this electric vehicle can bid on energy in California's wholesale power market

The California utility, San Diego Gas & Electric (SDG&E), has begun bidding energy resources from fleets of electric vehicles and storage systems into the state’s wholesale power market. The pilot program, one of the first of its kind, is meant to provide insights into how electric vehicles and other kinds of distributed energy resources can make the grid more reliable and efficient.

The project is expected to end in late 2015, with the planners hoping to glean valuable information on electric vehicle-grid integration and grid energy distribution. This grid-to-vehicle relationship is seen as a key factor in planning a more distributed energy grid, allowing EVs to charge at night when demand is low and acting as a grid resource when demand is high.

The issue with renewable energy, such as wind and solar, is its reliance on intermittent sources, combined with a lack of robust, efficient storage systems. California’s solar panels produce most of their energy during the middle of the day, but taper off in the evening when consumer energy needs are traditionally highest. Meanwhile, electric car batteries and other energy storage systems typically need recharging on a daily basis, if not more often.

The challenge for utilities such as SDG&E is integrating electric vehicles into the grid and efficiently allocating energy resources to the right place at the cheapest time, while benefiting both the customer and the supplier. The idea is to find workable solutions now, while the market is still relatively small. SDG&E says more than 13,000 electric vehicles are in use in its territory, while the state’s Zero-Emission Vehicles (ZEV) Action Plan wants to put 1.5 million zero-emissions vehicles on the road by 2025. The San Diego utility plans to add at least 5,500 EV charging stations during that time.

For the 10-month project, stationary storage systems and EV charging sites are combined at five locations throughout San Diego County and controlled remotely via software that balances charging needs and grid demand. The software provides "demand response" services; in other words, it charges up EVs during off-peak hours when demand is lower by correlating charging activity with wholesale energy prices, a setup that allows energy to be more efficiently spread to customers throughout the region. The cheaper off-peak charging rates are passed on to EV owners at similar prices to what a conventional power plant would be paid.

"The optimization software polls and understands the current state of charge of the vehicles, and each vehicle’s charging needs over a particular time horizon," SDG&E’s Hanan Eisenman told Gizmag.

As an example, a vehicle might be charged at 45 percent, and need a full charge to be completed sometime in the next four hours. Charging can occur (and be interrupted) at any time, as long as the vehicle is completely charged within the specified period. When the "demand resource" is in the market, instructions are sent by the optimization software to stop charging, which reduces demand in that hour. Charging resumes in lower priced hours, and is completed before the deadline set by the customer.

"Similarly, the storage resources stop charging in these hours, and potentially discharge to ensure the quantity of total response matches what was committed to the CAISO (California Independent System Operators) in our bids,” says Eisenman. "By being a direct participant in the CAISO’s markets and committing to reduce demand in certain high price hours, we allow the CAISO to not commit additional conventional resources in those hours.”

SDG&E is also developing a website/mobile app that lets customers set their EV charging preferences in response to rate signals, effectively acting as their own utility that buys from a larger grid power supplier. It’s also an additional piece of information SDG&E can gather and use on their customers’ charging behavior and grid use.

Source: San Diego Gas & Electric

5 comments
Daishi
Germiany is testing a similar program and this graph from the CAISO website helps explain the issue: http://i.imgur.com/3ODI8k8.png There is a 4-5 hour period in the late day of high demand where panels aren't generating much electricity. It's really expensive/inefficient to fire up extra coal plants just to operate for just 5 hours of the day so batteries/storage seems like a good solution to the problem. They don't have to store enough energy to power the grid till the sun comes up, only enough to help cover peak usage until late at night when peak demand levels off again. People pay flat rates per kWh of energy but the cost of wholesale energy for the grid fluctuates based on time of day. One possible solution is to just tie everyone with panels to wholesale pricing fluctuations and let the market adjust based on it (or at least give them the option). This way instead of people sending excess power to the grid at noon or 1 PM when the wholesale pricing (and credits) for the energy is low they can chose to store their excess power in batteries and send it to the grid in the evening instead for a higher price or more credits. If the cost delta between mid day and evening energy grows too much you could even just use energy from the grid, store it, then send it back out later in the day for a profit after subtracting your storage (battery) costs. I think this approach drives innovation for cheaper storage methods. Lithium Ion might make inroads here over the next few years but I'm not sure I see any reason grid scale storage should have to be the same portable, lightweight, and efficient technology we are using for cars. With a surplus of cheap renewable energy in the middle of the day the power could be used for potentially cheaper and less portable storage methods like compressing air, pumping water up hill, winding flywheels etc. Once solar becomes widespread enough that the wholesale price of energy at noon becomes zero I don't see a reason not to use it to pulley massive weights into the air with the intention of using them to drive turbines to generate electricity as the sun sets. The second grid storage companies can operate profitably buying and selling on margins the problem of storage is history. We just don't have enough energy on the grid from green sources to require them yet.
Freyr Gunnar
There's a much simpler and cheaper solution: Just build more nuclear power plants to replace those dirty coal power plants. Solar/wind + batteries + gas power plants won't solve the problem.
Larry English
who pays the owners of the cars for this complication/inconvenience?
Zolartan
@Freyr Gunnar Have you even looked at my response to your pro nuclear comments here: http://www.gizmag.com/solar-powered-pathway-netherlands/34613/ Nuclear power is a very bad choice if you want a cheap, clean and sustainable electricity supply. @Larry English The car owners profit by lower electricity costs for charging and if discharging is allowed they can profit from selling their electricity at higher peak prices.
Daishi
@Zolartan I am not against Nuclear power but I agree with some of of your points about it. If you started the paperwork today on a new nuclear power plant by the time you cleared the courts etc. and actually completed building the thing solar panels would be cheaper to run (in LCOE) The cost of solar is tanking and the cost of nuclear is essentially increasing. Even if you feel nuclear power is safe (and many people do) I think that is the biggest argument against them. Nuclear does provide stable power but it also can't be turned on and off as needed at different times of the day to reduce costs while the load is being supplied by other sources. Natural gas might make a better yin to solars yang until the storage thing is solved. It's still not coal but I think someone would have to be kind of brave to put up the money for a new nuclear power plant today.