Storing Energy as Heat is Feasible

Storing Energy as Heat is Feasible


In October 2014, the State of California required local publicly owned utilities to report the feasibility of energy storage in their districts. They all told the state that they could not identify any feasible way.

Nearly everyone I hear says that it is not feasible to store energy in quantities to offset the peaks and valleys of intermittent wind and solar generation. They say that is why clean energy will not be able to replace coal for power generation.     

Storage is not only feasible now, it has probably been feasible for at least 100 years. Yet nearly all the publicly owned utilities in California seem unaware of this. The Turlock Irrigation District did mention that the Solana Concentrating Solar project in Arizona is storing energy as heat in molten salts. But they didn’t seem to understand that the storage could also be feasible for their own and other local districts.

The storage of energy in molten salts is so practical that the Solana project can install and operate 2,000 acres of solar concentrators as well as the storage facilities and still sell electricity at a profit. That means that the storage part alone must be feasible and cost effective for energy storage.

Wikipedia says that a volume of about 150,000 cubic feet of such salts can hold enough energy to be able to run a standard type 100 megaWatt turbine generator for four hours.
The floor area of the Alameda Target store is about 139,000 square feet.  If that area covered a tank about 30 inches deep, the volume could hold more than 1,300 megaWatt hours of energy. That is about what the utility provided to all of its customers on the average day a few years ago. So, storage doesn’t take much space.

Heat can also be stored in cast- iron bricks, in granite rubble, in concrete and in dirt. Heat can be used to produce electricity. It can also be used directly as heat to replace the room heating and hot water for residents and businesses. It can drive refrigeration or air conditioning.

It can be used for commercial and industrial processes. It can be used for water desalination. “Forward osmosis” is more efficient and less costly than reverse osmosis such as is used in the Carlsbad desalination plant in San Diego.

Reverse osmosis has become so efficient that it now costs no more to desalinate sea water in San Diego than to pump water from Lake Shasta to Southern California. Forward osmosis is even more efficient. Heat energy can be obtained from solar collectors. Solar collectors should be required for every new construction and for refitting of most large, existing buildings.

Even in cold climates stored- heat systems are practical. The Drake Landing housing outside of Calgary in Canada meets nearly all of its yearly energy needs from heat collected in the summer and used in the winter.

Energy can also be collected from waste heat. In one of their proposals, the developers of site A at Alameda Point mentioned the ways of reclaiming heat which would otherwise be lost. They also have been involved in at least one notable carbon-neutral or carbon-negative business in the Harbor Bay Business Park.

Heat can come from other clean sources. The California grid administrator quotes the cost of electricity at one cent or less per kWh during low demand times of the day. At other times the cost is about seven cents per kWh. The energy should be taken when it is available and cheap.

Available cheap wind and solar energy can be used to drive heat pumps. Heat pumps can provide about five times as much heat energy as the electricity needed to drive the pumps. So every one kWh of electricity can be used to generate about five kWh of heat. That heat could offset the heat now provided by burning natural gas or by electrical resistance heating. The cost of natural gas is about five cents per kWh. So the use of heat pump heat using electricity costing of about one cent per kW hour can avoid burning 5 kiloWatt hours of fossil fuel at a cost of 25 cents.

This coming year, publicly owned utilities are again required to work up reports on the feasibility of storing energy in their district areas. 

Let’s hope that this time they will consider the storage of energy by heat.