According to research conducted by the Massachusetts Institute of Technology, renewable sources of energy such as the sun and wind could become economically competitive with traditional sources of energy via the use of “liquid batteries”.
Sayda Wind Park – Obtained with thanks from Eclipse.sx on Wikimedia Commons: http://commons.wikimedia.org/wiki/User:Eclipse.sx
This is the first time that I have heard MIT announce that they officially have the answer to the solar and wind intermittency problem. They made many announcements in the past of inventions of theirs that could potentially be cheaper than traditional energy storage systems such as the lithium-ion or lead-acid batteries in use today, but never this.
Primer: The sun does not always shine, the wind does not always blow, wind speeds fluctuate, and the amount of sunlight we receive varies due to clouds. According to the United States Department of Energy 2011 Annual Energy Outlook, the average cost of wind power in the U.S is only 9.7 cents per kWh (kilowatt-hour) of electricity that wind farms generate.
What this translates to: Wind power’s problem is no longer the cost to generate it. It is now mainly intermittency. Fluctuations in the amount of power generated by a wind farm can be compensated for by adjusting other hydroelectric, or fossil fueled natural gas, nuclear, or coal power plants. If a wind farm generates more than necessary, other power plants can be turned down to compensate for that, and back up again when there is less than enough wind power available.
The ability of fossil fueled power plants to adjust is very limited because they take long to make major adjustments in power production and energy storage enables wind farms to independently supply power without the help of other power plants.
This can be achieved with lithium-ion or lead-acid batteries, but these are too expensive. The cost issue associated with lead-acid batteries is because of their short lifespan and and inefficiency. They have to be replaced frequently, waste too much electricity, and this cost of these adds up.
According to MIT, liquid batteries are inexpensive and have a longer lifespan than traditional batteries. The three materials contained in the liquid batteries each settle in separate layers due to the difference in their densities, which, in this case, is a good thing. They have to be separate to work correctly.
This project was conducted with the importance of material availability and abundance in mind. All three layers of the battery materials used are abundant and inexpensive.
“We explored many chemistries,” Sadoway says. The negative electrode (anode) is in the top layer and is made of magnesium, the middle layer, which is the electrolyte consists of a salt mixture containing magnesium chloride, and the bottom layer which is the positive electrode (cathode) is made of antimony.
This battery operates at a temperature of 700 °C, which is 1,292 °F.
Discharging: The battery generates an electric current as each magnesium atom (this is in the negative electrode) loses two electrons, then they are magnesium ions which travel to the other antimony electrode. The magnesium ions then reacquire two more electrons and become magnesium again because of this. This causes an alloy to form with the antimony.
Charging: When the battery is supplied with an electric current, this process is reversed and the electrons are driven out of the antimony electrode, and back to the magnesium electrode.
As I say sometimes, batteries do not store electricity, they generate it. When you charge a battery, you supply it with an electric current that drives a chemical reaction of which the one mentioned above is an example. You reverse that process to make the battery generate electricity.
Source: MIT News Office