From Science Daily:

A new study shows that wind, water and solar generators can theoretically result in a reliable, affordable national grid when the generators are combined with inexpensive storage.

Over the last few years, Mark Jacobson, a Stanford professor of civil and environmental engineering, and his colleague, Mark Delucchi of the University of California, Berkeley, have produced a series of plans, based on huge amounts of data churned through computer models, showing how each state in America could shift from fossil fuel to entirely renewable energy.

In a new study published today in Proceedings of the National Academy of Sciences, they use the data from those single-state calculations of the number of wind, water and solar generators potentially needed in each state to show that these installations can theoretically result in a reliable, affordable national grid when the generators are combined with inexpensive storage and “demand response” — a program in which utilities give customers incentives to control times of peak demand.

An underground effort

The proposed system relies on the ability to store and retrieve heat, cold and electricity in order to meet demand at all times.

Summer heat gathered in rooftop solar collectors could be stored in soil or rocks and used for heating homes in winter. Excess or low-cost electricity could be used to make ice, which would be used for later cooling when the price of electricity is high.

Excess electricity could also used to make more electricity, by supplementing the energy-producing mechanisms that drive concentrated solar power…

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