Battery Foolishness in Florida


Date: Apr 10, 2019

The largest electric utility in Florida is proposing building the world’s largest battery to smooth the output of solar energy installations.

Wind and solar energy are erratic. Output depends on when the sun is shining or the wind is blowing. If only electricity could be economically stored, wind and solar would be a lot more practical, or at least, less impracticable. With storage, when the sun is shining or the wind is blowing, electricity could be stored for use when the wind or solar was temporarily dead in the water.

There are two methods of storing electricity that are not entirely inadequate: pumped storage and lithium batteries. Pumped storage is best, but it requires two reservoirs at considerably different heights. That’s out of the question in pancake-flat Florida. Batteries are great for computers, cellphones and portable drills. They are even semi-practical for automobiles like Tesla’s products. But batteries are desperately expensive for smoothing out wind or solar energy.

Florida Power and Light (FPL), is proposing that the world’s largest battery that will be connected to a small solar plant. The battery will be capable of storing 900 megawatt hours of electricity. It will cost about $400 million. The solar plant in question has an average output of about 15 megawatts. The battery will be able to store 60 hours’ worth of the solar output. If it is cloudy for more than 60 hours the battery will likely run flat. There are over 100 cloudy days per year in nearby Tampa Florida, so one suspects that is cloudy for more than 60 hours, or 3 days in the row, from time to time.

The electricity exiting from a typical utility scale solar plant, without subsidies, costs about $70 per megawatt hour. Adding the battery to the system will jack up the price to more than $300 per megawatt hour. An interesting sidelight is that the energy stored in FPL’s 900 MWh battery is equal to the energy in 800 tons of high explosive TNT. That is about 1/20th of the energy released by the atomic bomb that destroyed Hiroshima, Japan. Given the many fires traceable to lithium batteries, that is something to think about.

FPL’s proposed battery is capable of supplying 400 megawatts for 2 hours. That is a high rate of discharge, making the system more expensive. So, perhaps, the battery is actually intended to be a peaking generator pressed into service when electricity consumption peaks briefly. I suspect that this is the case and all the blather about solar energy is a cover story to make the battery fit in with green psychology. The beauty of painting something green is that it makes foolish projects desirable. The problem with the battery as a peaking generator is that for about the same money one can buy a combined cycle natural gas plant that can supply 400 megawatts for as long as you want, not just for two hours. Further the electricity from the gas plant will cost $50 per megawatt hour, not $300.

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