by Jack Jenkins

Created on: July 29, 2008

How to make a solar powered water battery

Wouldn't it be nice if we could meet our rising energy demands using sources that are clean and abundant. Ohh say . . . . water and the sun. Well that dream is becoming reality. Amazingly enough, the technology is being driven by extraterrestrial dreams!
I recently read an article on NASA's website that described a technology they think will be quite useful when establishing a permanent base on the Moon (supposedly going to happen in the next couple decades). This technology makes use of the abundant solar energy illuminating the Moon's surface. The problem comes when night falls. The answer, a water battery of course!

Well, not exactly the battery you and I think of every day. Really though, the purpose of a battery is to store energy. So how can we use water to do this on the Moon. The technology discussed in the article was called a closed fuel cell. A fuel cell, at least the one discussed in the article is a device that takes hydrogen gas and combines it with oxygen to form water. Anyone who has seen this done will be able to tell you this reaction packs a powerful punch. In fact, hydrogen and oxygen can be used as rocket fuel. That however is not the purpose in this case. The energy released during this reaction would be used to power generators for electrical power and heat generation on the Moon during times of low or no solar illumination. Ok great but how is that a battery? Well while the Sun is up solar panels would be used to produce not only enough electrical power for the bases consumption, but also enough to split water into hydrogen and oxygen gas. These gasses would then be stored separately. When solar illumination fell below the threshold necessary to power the base, the hydrogen and oxygen gasses would be burned together to power the base!
The reason the technology is called a closed fuel cell is because the water produced by the reaction is recaptured and stored. Then the water is split again into hydrogen and oxygen during the day. In this way solar power is providing all of the energy required, both night and day, and water or at least its constituent gasses acts as a battery, storing energy during the day to be used at night! This way of storing energy has an advantage over storing heat in water since there is no loss of captured energy over time due to thermal radiation. For instance, one cubic meter of water at 203 degrees Fahrenheit (95% of the way to boiling from freezing) radiates four kilowatts of energy assuming a non-insulated container of the smallest radiating area. Of course insulation can be used and would help greatly, but the fuel cell doesn't need this insulation at all. However, storage of hydrogen gas is more dangerous than storage of hot water. This risk is one of the reasons opponents of fuel cell vehicles claim. For a stationary system though, this risk is minimal.
In conclusion, a closed cell hydrogen fuel cell in conjunction with solar power will be a great way of extending the useful ness of clean solar energy technologies into the night and cloudy days her on Earth as well as in future endeavors beyond our atmosphere!

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