Save energy in lime CaO

[magi]

Hello.

I am at my university working on an idea if it would be possible to store heat energy in quicklime CaO.
We are to use a solar parabol to concentrate the sunlight and get a temperature in focus around 1000 C degres.

In that temperature it is possible to burn limestone to quicklime and then save it in a airtight storage.
1000 kg have about 320 kWh and can be bought in my country for around 45 $/1000 kg.
Does anyone know if we are wrong about this becouse it seems to easy to save energy this way.
The parabol need to be around 25 m2 to be able to burn enough CaO in one summer.
To save energy to heat a house I need to burn around 15000-25000 kg to be able to heat a house over the winter.
1000 kg CaO takes around 1-1.5 m3 so big storage is needed.


After the winter the reaction with water have turned CaO to Ca(OH)2 and it can be burned again (only this time at 550 degrees) to store energy for the next winter.

If it works you dont ever need to buy heat to your house again.

Do you think it is possible?
Have anyone heard if someone does something like this?
Nobody have tried it in my country so I hope someone out there know something.

I found a PDF-document that NASA did about it, so it seem possible.

http://purl.access.gpo.gov/GPO/LPS58424

Regards Magi

[mgopilot]

It sounds like a good idea, but then, why isn't it done?
I do know that to make the CaO as a basis for even cheaper Portland Cement takes heating limestone to over 2,000 F along with crushing. Then it must be protected from humidity, and of course, water. The reaction creates heat, but no where near the heat it took to make it.
On the moon with solar energy and already powdered rocks of the right type, no humidity to worry about (or getting the stuff in your eyes or on your skin), it sounds like it could work. However it does suck a LOT of water, which would have to be transported there.

[magi]

They hope to find water on the moon.
Maybe thats why they thought of burning CaO on the moon.

[magi]

Hi.

Reviving this becouse I think it is important.

Regards Magi

[Richard]

It's been a long time since I did chemistry but I suspect that in principle the idea you outlined is okay. I suspect the main reasons it hasn't been done is:

1) Cost - there are cheaper ways to heat a house
2) Practicality - there's often a big difference between an idea in theory and an idea in practice

As a experiment it sounds worthwhile. In practice I suspect that it's just too complicated and expensive.

As for similar schemes - I have heard about an idea where exterior walls that face the sun during the day are impregnated with waxy-type substances that absorb solar energy and melt during the day (but are retained within the wall) and solidify at night, released their stored latent heat as they do and keeping the house warm. The are quite a few other ideas at the moment which relate to using stored heat or chemical energy.

This kind of think is quite rare at the moment but is likely to become more common in the future, especially if energy costs continue to rise.

[magi]

Hi.
Why I think it is interesting is because it will also be able to run a steam engin with generator becouse you get 400 C when you poor water on CaO and turn it to Ca(OH)2.

So with a compleat system you get free heat and electricity for years.

[mgopilot]

Originally Posted by mgopilot

It sounds like a good idea, but then, why isn't it done?
I do know that to make the CaO as a basis for even cheaper Portland Cement takes heating limestone to over 2,000 F along with crushing. Then it must be protected from humidity, and of course, water. The reaction creates heat, but no where near the heat it took to make it.
On the moon with solar energy and already powdered rocks of the right type, no humidity to worry about (or getting the stuff in your eyes or on your skin), it sounds like it could work. However it does suck a LOT of water, which would have to be transported there.

Even with water there, unless there is a large amount the hydrated lime would have to be turned back to quicklime at a net energy loss of over double.
It would be better to use solar concentrators to heat thermal mass (rocks), and to use the water in recycling steam turbine generators.
With unlimited easy and close CaO and H2O, plus easy and close room for the waste hydrate (and unlimited strong sunshine)--it is feasible, but those conditions do not exist as a set.

[magi]

I have been talking to a some people at a company that burn lime for use in cement and concreate.

They think the idea is very good and somebody should really try it out.

The first time you need to burn lime you dont get back as much enery as you load it with but when you recycle the Ca(OH)2 it only need to be burned at 550 C degrees and you then get back a lot of the energy you use to load it.

Please try to discuss this with energy people and lime companies and make some real tests becouse the people ive been talking to think it chould work.

Regards Magi