Jul 21 2012

Storing Renewable Energy

Published by under Student blog entries

A group of ultracapacitors

Since several sources of renewable energy are intermittent, such as wind, wave, and solar, there is a strong need for a way to store the energy during times when the energy sources are low.  For instance, in February of 2008, Texas, which relies heavily on wind power, had a production drop of 1200MW due to the lack of wind.  During this time, power plants had to scramble to make up the difference.  It is for this and many other reasons that finding a way to store renewable energy is so critical.

A number of different batteries have been developed for long=term storage.  Lead-acid batteries are commonly used.  While they only store a small amount of energy, they are both inexpensive and reliable.  Lithium-ion batteries are also being used more and more as they have a high energy density and can be charged over and over with little degradation.  Flow batteries are a third type in which charged chemicals are pumped into storage tanks, back into the active portion of the battery, and drawn when needed.   Additional energy can be stored as more and more tanks are added.

In addition to batteries, other energy storage techniques are being explored.  Ultracapacitors are devices that store energy in an electric field rather than a chemical reaction, as batteries do.  This allows the devices to be charged far more times than batteries; however, they are not able to store as much energy.

Another new process was recently discovered by Jeffrey Grossman and Alexie Kolpak of MIT.  The two discovered an azobenzene-functionalized carbon nanotube molecule which is able to convert solar energy, store it indefinitely, and release it when met with a catalyst such as heat.  The molecule changes shape when met with sunlight, the solar energy is stored in chemical bonds, and once a catalyst is introduced, the molecule releases the energy and returns to its original state.  This is a very recent discovery which may prove to be huge breakthrough in solar energy storage.  Other technologies are constantly being explored in order to increase the efficiency of renewable energy devices and to have plenty of energy at the ready during times of lower energy sources.







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