The energy that needs to be stored is wind. That is the type of energy that is abundant at the worst time for the electricity market. Solar energy peaks at almost exactly the same time as the electricity market. Storing that energy is a waste of time, money, and effort. Just use it when generated.
William Quaintance
I agree with Ken Silverstein that energy storage is very important in matching the output from intermittent renewables such as solar to demand on the grid.
Rather than focusing on putting batteries at individual homes that have solar electric systems a more effective approach is first to allow utilities to shift loads away from times when load on the grid is maximum by using thermal energy storage. If someday intermittent renewables make up a substantial fraction of generation on the grid then the utility could store energy from these sources using thermal energy storage. A simple and low cost form of thermal energy storage is ice.
This is already being done in many large installations and will soon be available for individual homes from Trinity Thermal Systems using a product called, "IceCycle" (I have no financial interest in this company).
Unlike battery storage ice storage doesn't use toxic materials and has a long life. It can be easily scaled to large or small systems.
Widespread use of thermal energy storage using ice could, with the proper incentives, substantially shave peak power use on the grid and facilitate adding large amounts of intermittent renewable energy to the grid.
Michael Winkler
Schatz Energy Research Center
Energy Storage is going to become more and more important as we move away from fossil fuels toward renewable energy sources. Sources like solar and wind energy are, by their nature, not consistent. The ability to store their energy and release it as needed may be the most important issue in the conversion away from oil and coal. There is certainly much research in this area, including one promising alternative called 'flow batteries'. I expect there will be a number of different solutions for different situations.
Jim Colleran
Salem, VA
Glad to hear about renewed interest in an old idea. The value of storing energy generated far more cheaply off-peak for use during peaks has been well-understood by utilities for at least 100 years and is not unusual in Europe. In the late seventies, many US utilities became serious about these projects as the first wave of nuclear generation came to a close. The term "peak-shifting" briefly gained favor. Most of these projects took the form of pumped storage involving two reservoirs close together but at very different elevations. Virginia's Bath County Pumped Storage Station, which came online in the mid-eighties, is perhaps the most well-known example and has provided huge "peak-shaving" value so far. Typical efficiencies for pumped storage are around 70%, so with the difference in cost to generate the next kilowatt varying between peak and off-peak by factors of ten, the value of these projects is pretty straightforward (straightforward enough for state regulators to understan d). Another form of pumped storage, compressing air into naturally occurring underground caverns, got a lot of attention in that same time period as well.
The concept, beautiful as it was from an engineering perspective, died out as the specter of deregulation undermined the economics. The same logic that caused utility executives and the capital markets to decide that transmission construction was suddenly quite risky -- the benefits might flow to someone else, even to the owner's competitor -- also made it uncertain if the owner would gain the benefits of peak shaving.
Two points did not come out in your article that may be good topics for a follow-up: First, what is the efficiency of battery array storage these days, counting periodic replacement costs? It is surely lower than pumped storage efficiency, but there may be an offsetting capital cost advantage, particularly since most pumped storage hydro sites require at least one of the reservoirs to be built. Second and more fascinating is the fact that battery array storage offers peak shaving for transmission as well as for generation, a benefit that pumped storage cannot offer. So the same benefits that distributed generation offers in offsetting new transmission capacity are also offered by battery storage, which makes the promise even more powerful in California with its well understood (now) transmission congestion problems.
Hack Heyward
The discussion on battery storage is interesting yet, as most would agree, battery technology will not be widely viable for several years in the future. There is a technology available today that provides energy storage and a valuable commodity at the same time -- TES (Thermal Energy Storage).
The most widely available systems are ice and chilled water storage. Hot water storage is a third system and one where solar can work quite well when coupled to large storage systems. Batteries also present environmental issues for recycling whereas ice and cold water thermal storage also have their own environmental issues. All of which can be minimized but not eliminated. In certain installations chilled water storage can provide additional benefits, such as in areas where fire hydrants are not available the chilled water tank acts as a very large fire hydrant.
TES is a viable product on the market today with many manufacturers and suppliers so costs can be quite competitive. While TES requires more kWh to produce, the energy being used is "off-peak" when the cost is less expensive and the utilities are at their lowest point on the energy demand curve. Building that off-peak valley is important to stabilizing and maximizing generation costs. Utilities need to be encouraged to provide greater differences in on-peak and off-peak rates to promote the installation of TES systems.
States such as California, Florida, New York and others should be maximizing these technologies since systems now exist for residential, commercial and industrial applications. In addition to money being spent on solar, wind, geothermal and other modes of power generation that fluctuate based on Mother Nature, TES systems can produce now and fill the void until battery technology catches up. To maximize savings of TES systems, one can use solar to power DC motors wired direct, during the peak daylight hours, instead of using AC power which requires an inverter that consumes about 25% of the energy produced. Marrying existing technology with advanced technology will stretch available resources further and continue the incremental advancements until the big breakthroughs in technology occur.
The "Deming" philosophy at work.
Rick Chalker, C.E.M.
Executive Accounts Manager
FPL
I have serious concerns about placing lots of 'battery packs' around to store excess energy. One concern is a significant amount of energy stored in a 'battery pack' becomes an attractive target for terrorists. Another is hazardous waste generation issues -- the last thing we need is another 'PCB' debacle created by utility companies trying to make a buck without fully considering total life cycle impacts and costs. We, as a nation, have a habit of allowing Corporations to pass 'end of life' costs on to taxpayers instead of taking it from the (excessive?) compensation of those corporate executives making those decisions.
On the other hands, serious research and sound engineering analysis over 15 years ago proved the economic and safety attractiveness of superconducting magnetic energy storage. A facility only 100 yards in diameter 10' deep, in the ground, concrete lined circular trench would store the entire daily output of a 1000 mega-watt power plant. A few of those located in key power distribution junctions could serve as safe, environmentally benign 'batteries.'
Keith E. Bowers
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