Stanley Reed for the NY Times:  A new cash crop has sprung up on Nicholas Beatty’s enchanting farm near here. Rows of gray solar panels range over about 25 acres, turning sunlight into electricity, as dog-size muntjac deer hop by.

The panels themselves, trouble-free money earners that feed into the electric grid, are no longer unusual on farms in Britain or other countries. What’s new in Mr. Beatty’s field is a hulking 40-foot-long shipping container.

Stacked inside, in what look like drawers, are about 200 lithium-ion cells that make up a battery large enough to store a substantial portion of the electricity the solar farm puts out.

The battery and its software give Mr. Beatty an advantage over other solar panel farmers. Power prices in Britain and elsewhere rise and fall, sometimes strikingly, during the day and over the year, depending on the supply and demand.  Cont'd...