Alternative Energy Forums

Since it takes a lot of energy to heat up water, it must follow that hot water (say at 70 deg Celsius) must be "storing" a lot of energy that could be turned into electricity.

Now - you realize that I am NOT talking about super-heated steam from under the earth - just normal hot water.

Hot water can easily be gathered on sunny days using hot water solar panels mounted on roofs.

How could this hot water be made to give up its energy and how to convert it into electricity ?

I have thought of one idea.
As the water heats up on the panels, it rises up to the hot water tank. This effect is used to push cooler water into the bottom of the panels and therefore the water keeps getting hotter.
Could this motion be used to drive a kind of small turbine connected to a generator?

I think that the circulation is quite slow and therefore the power output from the water motion would be small.

That is why I wanted to know if there is anyway of using that hot water to get electricity?

Any thoughts?

Davvit

I think is much better to use this 70 degrees hot water at your house for warming or cooling purposes than converting that heat to energy.

Damon

70 degrees of heat in water is not enough for the conversion to be fruitful. You will not get a desired output, rather your experiment of moving a turbine with that energy is not feasible.

I don't think the motion of the water in your example would be nearly enough to create power from a turbine. However, I do think this is a good point of discussion.

If you're using a solar tube array to heat water for your water heater, on some sunny days there would be excess heat. As the water heats up and meets the desired temperature in your water heater, you probably have a 3-way valve to bypass the tank and keep the water cycling through the solar tubes, as to prevent over heating at the panels. I've heard of applications using some sort of radiator outside in the shade to reject this excess heat, but this seems like a waste of energy. It would be useful if there was a way to create electricity with this excess hot water, but with current technology I just don't see how...

I am a bit rusty on thermodynamic calculations but I'm sure that if you heat up cold water it expands. If you can contain say 20 degree water in 1 metre cube volume and heat it up to say 70 degrees on a very sunny day. You could use that pressure through a water jet to drive a small turbine.

(P2.V2)/T2 = (P1.V1)/T1

I found P2 = 4 bar. Look at it this way. If it doesn't work you'll still have a very cool water pistol and you can keep your neighbours dog off your lawn.