Solar Thermal with Storage Capacity

Saturday, March 29th, 2008

One obvious concern about solar power is that it’s only available during daylight hours on cloudless days, but solar thermal power can run off of stored heat, which is remarkably cheap and efficient to store:

The ability to utilize solar thermal technology after the sun sets is made possible by a storage system that is up to 93% efficient, according to Ausra’s executive vice president John O’Donnell.
“My favorite example in comparing energy storage options is on your desktop,” said John O’Donnell. “If you have a laptop computer and a thermos of coffee on your desk, the battery in your laptop and the thermos store about the same amount of energy. One of them costs about $150 and the other one costs maybe $3 to $5. On the wholesale level, storing electric power is at least 100 times more expensive than storing heat.”

Of course, even without storage, solar power production peaks during almost the same time as consumption — but not quite:

The maximum amount of electricity demand on the power grid occurs during weekday afternoons and evenings in the summer months in most regions of the United States. This is largely caused by air conditioning loads, which gobble up electricity. Solar energy availability however starts to drop in the late afternoon, before peak load has started to wane.

Because the electric grid needs to be able to handle these peak loads, capacity is built to specifically handle these loads. Natural gas typically comes to the rescue to produce this electricity. Although these plants are expensive to operate, they are cheaper to construct than most of the alternatives. They are fast to start, producing power in 30 minutes or less.

Additional power plants are constructed just to generate electricity for the times when it is needed most. This causes peak electricity to be more expensive. A kilowatt hour of electricity at 3 pm and 3 am does not come with the same price tag to the utility company.

Naturally, peak electricity should cost the consumer much, much more than non-peak electricity, but it typically doesn’t.

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