All we need is free level 1 charging -- the kind you get from a standard household plug. That and a fleet of plug-in hybrid cars equipped with bi-directional chargers that can cycle power between the cars' batteries and the electric grid, in order to level the renewable power supply that we'll be getting.
Frank has an economic interest in making plug-in hybrids successful because he holds patents on the technology -- he's co-founded a company in Palo Alto called Efficient Drivetrains Inc. and has been working on plug-in hybrids for 30 years.
"If we took the production of the Chevy Volt and sold it to Hawaii, in 15 years we'd have enough plug-in hybrids to store energy from wind and get the entire state off fossil fuels entirely," he said last month at an electric car conference in San Jose.
Here's how he'd do it.
Consider the island of Hawaii, where nearly 90 percent of electricity comes from petroleum. Make all cars plug-in hybrids (UC Davis's PHEV Center has been converting gas-fueled cars to plug-ins for years) and plug the cars in whenever they're not being used -- about 21 hours a day.
The average car in Hawaii drives about 20 miles a day and would need about 10 kilowatt-hours of electricity, Frank figures, which it could get from a standard electrical plug in about six hours.
Plugs would be everywhere, and charging your car would be free. Frank points out that the Bay Area Rapid Transit system (BART), for instance, would incur no cost by letting commuters charge 3,500 cars in its parking lot and could even save $1.5 million per year, based on the amount of power it pays for now.
That's because BART has to predict its electrical loads and pay for them ahead of time, and it tends to overestimate what it needs so it doesn't run out, he says.
Then make sure that the electricity is generated from renewable energy -- in Hawaii, that would be wind. (Frank calculates how many wind turbines would have to be built in Hawaii to accomplish this in 15 years).
Since wind and solar power vary with weather and time of day, use the plugged-in cars' batteries to store energy for the grid and level the power supply. Cycle energy between the batteries and the grid by using a bidirectional charger that can convert stored energy from the batteries (DC) into AC energy and vice versa. If the cars need extra range, run them on biofuels instead of gasoline.
Frank figures that a typical home would have two hybrids -- one short range and one longer range. One car could be charging at home while the other car charges at work.
"These vehicles can be integrated into the existing vehicle fleet a year at a time, or continuously over a 15-year period," Frank writes in a white paper he's published on this scheme. "...the public would not replace an existing vehicle until it is worn out, which is about 15 years. This rollout period for the plug-in hybrid replacing the entire fleet in a 15-year period is reasonable due to the buying habits of the public and the life of the cars."
Convinced? It could work if we were all willing to forgo trading in our cars for new models! Frank's paper is not online, but if you want to see his calculations, you may be able to get the paper here.