One major advantage of the energy sources that are currently prevalently used in the world is their inert nature. We can store coal and biomass in open room-temperature air, or gas and petroleum products in tanks. Even plutonium, while radioactive, can be stored in special containers. However, it is quite obvious that mankind has not yet perfected techniques for storing energy from the sun or the wind. The June 2009 Discover Magazine article ‘Lightning in a Bottle’ examines several new energy storage techniques, some of which may help to mitigate the storage problems inherent in solar and wind energy generation.
The new technologies take varying approaches:
One type of technology uses energy to pump compressed air into a sealed cavern. The compressed air can be released to turn a turbine at will, thereby generating power; however, dependence on outside power in order to pump the turbine system decreases the overall efficiency of this system. Furthermore, the compressed air system has the inherent problem of leakage, as well as the perquisite of an extremely large cavernous space to store compressed air in. Currently both of the two examples of the compressed-air energy storage utilize rare natural salt dome formations. Developers have proposed that other large underground spaces, including an abandoned limestone mine and an empty aquifer, could be used. Also Georgianne Peek, an advocate of sealed-air energy storage, speculated that oil wells and natural gas reservoirs could store compressed air as well, the article said. One might also wonder if other rock quarries, for example granite or marble quarries, could serve a similar purpose- based on simple hardness, such rock would seem to be to be less porous than limestone.
The article also looks at molten salt technology, which can be used in combination with a large solar power plant. Some questions regarding the nature of the salts occurred in my mind immediately: seeing that the salts are mixed with nitric acid, they would presumably be corrosive? Furthermore, are the salts toxic? In the article, a US Department of Energy official said that the use of molten salt-based storage technology can increase the amount of time that a plant is fully operational in a year ‘from 25 percent to up to 70 percent’, thereby nearly tripling the amount of time that such a plant would be active. Naturally the power generation system would need to rely on other power sources for the other ~30% of the time, but implementation of such storage techniques on a large scale could greatly increase the viability of solar power generation.
The article also examines sodium-sulfur batteries, which may be a good method of storing wind energy due to the relatively higher energy density and longevity of such batteries compared to traditional lead-acid batteries. Other developers are working on batteries which would use zinc bromide or vanadium oxide. Such technologies may prove extemely useful due to their relatively small size, because they could be combined with small-scale wind farms in order to increase the overall efficiency of the wind power generation. A new hydrogen ion generation system developed at MIT could prove to be the key to allowing hydrogen to perform similar energy storage functions, with the added benefit that the materials required are cheaper, the article said.
Finally, the article discusses the issues surrounding implementation of battery powered cars, including battery life range and charger infrastructure. After finishing the article, I had the further thought that one other consideration for new power sources would be benefits that could be had by implementing either a superconducting electric grid or effective measures for miniaturizing some or all of these power storage systems. Either of these two technologies would lead to great gains in efficiency of energy use due to lower transport costs. Amory Lovins of the Rocky Mountain Institute has written extensively on ‘micropower’, which uses mainly small-scale energy generation equipment. Micropower equipment would give a great amount of flexibility in energy production if it could be properly implemented and does not require government-level capital projects in order to be implemented. On the other hand, a nuanced approach involving a superconducting smart grid would also help alleviate the problem of new energy storage and transmission. Suppose a future when, through the use of computers, a utility company can track a car’s energy usage so that when it parks, through the use of computer-linked charging systems, which would refill the car’s battery while it is parked and bill the driver for the refill automatically through a debit or credit payment.
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