Hybrid car as generator-on-wheels

CNet News is running a photo-story titled Hybrids that give back to the grid. The article centers on heavily modded hybrids exhibited at the Alternative Energy Solutions Summit at AMD headquarters in Sunnyvale, CA. One of them is the well known PRIUS+, a plug-in hybrid project from CalCars. More intriguing is the concept car from Pacific Gas & Energy, where the car can feed power back to the grid. Intended application is to reduce the power drawn from the grid, or even profit by a type of electricity arbitrage over time. During the day when air-conditioners are running full blast and stores are open, power demand is higher– and so are prices– compared to evenings. Charging at night with mains power (or simply charging from normal driving) and selling the surplus back to the grid at peak pricing time has the potential to turn every driver into a micro power-plant operator.

But a more mundane application could turn out to be the prime driver: supplying emergency power in the case of an outage. Typically power can be drawn from a vehicle in a  variety of ways:

  • From the cigarette-lighter adapter, for low consumption needs (<150 W) from charging a cell-phone to running a laptop. Unless the gadget has its own car adapter, this requires an inverter to convert DC from the battery into 110V AC that electronics in North America expect.
  • Directly from the battery, using a beefier inverter. One popular manufacturer’s models go up to 3000W. This is good enough to run most appliances, including microwave, large TVs, PCs, vacuum and even power hungry dishwashers although running them all at once may be a challenge.  (This page from the Dept of Energy lists typical consumption of gadgets.)

Neither can cope with the demands of a water-heater or clothes dryer which can go up to 5000 watts. Enter hybrid vehicles. Batteries in a bone-stock Prius are rated at around 20 kilowatts, indicating that the bank of batteries is capable of supplying all the power required to run a house. Plug-in hybrids have even more powerful batteries since they are designed to be able to run ~40 miles without having to start the internal consumption engine. But the  those batteries may not have been designed to supply large amounts of power continuously. In ordinary driving the “electric assist” kicks in occasionally for heavy acceleration or low-power cruising. (The car can always fall back on the ICE to drive the alternator and generator more power for charging the batteries as needed.)

Either way serious mods are necessary before the Prius in the garage can replace the trusty generator during an outage, which is the vision that PG&E has advocated. It is a promising concept and may well become cost-effective for buyers, considering that a moderate size 5000W generator lists over $3K. This would be one more reason for increased hybrid sales in hurricane-prone areas such as coastal Florida.


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