The St. Petersburg Times reported this weekend on efforts by researchers at the University of South Florida St. Petersburg to develop generator-sized batteries that can store power from solar panels.

Those efforts could provide a crucial step toward overcoming one of the main hurdles to replacing our current power system with one that runs primarily on renewable energy. The challenge is making the energy available when it’s needed most. As the environmental blog Grist explains:

There’s a certain amount of demand for electricity that is steady and reliable. Above that, there are fluctuating “peaks” of demand each day, usually evening, when everyone gets home and starts watching TV and running the dishwasher, or in hot areas, the afternoon. For that steady core of demand, we have “baseload” power plants — in the majority of cases, large coal or nuclear plants. Once they’re built they’re pretty cheap to operate and you can run them around the clock. In nerdspeak, they have a high “capacity factor.” However, they’re not well suited to ramping up and down in response to short-term fluctuations. (It takes days to turn a nuke plant off and back on.) To supply power during the fluctuating peaks, we have, appropriately enough, “peaker” plants, which can be turned on and off quickly. (Nerdspeak: they’re “dispatchable.”) Generally speaking, these are natural-gas plants, which are smaller and easier to cycle, though the power is somewhat more expensive.

So you’ve got your baseload plants and your peaker plants. The fundamental problem with renewables, according to conventional wisdom, is that they are neither. They are variable and intermittent, with low capacity factors, so they can’t satisfy baseload demand. But the wind and sun are not dispatchable, so they can’t reliably satisfy peak demand either. They are an unholy mutt, a square peg for a system with two round holes.

One possible part of the solution, which Grist explores, is to create an interlocking patchwork of different sources of renewable power (wind, solar, biomass and so on) that’s robust enough to mimic the reliability of the current power system.

The batteries described in the Times article offer another approach — making it possible to absorb the sun’s energy when it’s most available (typcially during the early afternoon, when the sun shines brightest) and store it until it’s most needed (typically during the evening, or perhaps when someone plugs in a hybrid vehicle that needs recharging).

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