Electricity from heat exchangers?

[crazyoldfart]

I have conducted several experiments with heat exchangers and reclaiming heat lost from home electronics. I built a cabinet that pulled the heat off 3 desktop computers with 4 hard drives each. the temperature was a pretty constant 110 degrees. this went thru a heat exchanger with water (closed loop like a car radiator ) water temp was 107 degrees . Now if we replace the water with a technology over a hundred years old, the first refrigerators, we could get pressures that could drive a turbine.
How big a turbine you ask, I have no Idea. it takes money to build brand new untested hardware and make it work.
And unfortunately I don't have a lot of extra money, so it's not developed 
So yes there are many ways to reclaim lost energy from heat, It's a matter of funding that makes it work or not

[crazyoldfart]

Yes, it is many ways to harness the potential between two temperatures. What you mention are a very good way of doing it. I will consider using the groundwater which is only 2 meters below the surface under my house. Drill a hole and put some pipes down there. Water can circulate with a small pump and supply a sterling engine with constant temperature on one side, and a variable temperature on the other side. The good thing is that the engine works better in the winter time where the temperatures up here reach below -30 degrees celcius some times. The machine will generate enough power to heat up the house

Peltier devices may be a good alternative to heat exchanger if your outside temp gets real low. heat exchangers also work well with peltier devices when designed properly

[Low-Q]

You can't.

You can extract energy from an environmental temperature difference, but there is absolutely no way to create a temperature difference using a heat exchanger then use that difference to generate more energy than was required to power the heat exchanger in the first place.

You're right. At least not in a closed insolated loop. I still believe it is possible in open air without violating any laws. Mechanical work out on expence of colder atmosphere - and it's lots of air to take that heat from. I'll bet that someone will figure out how ;-)

Vidar

[jfilmmusic]

Reading everyone's comments in this thread inspired me to take some basic measurements on a simple heat engine - one that runs constantly in a normal household ambient environment, makes and uses only a ~2 degree temperature difference (by itself), and runs reliably 24/7 for months on end. To break it down I have made no attempt to create or use any available temperature difference to enhance the process, so I hope this is useful data.


Starting at the smallest scale using a tiny 6 inch 'drinking bird', which is successfully able to lift (in addition to it's own weight) a 6g ND magnet twice a minute by 7.62cm verified over several days, (attached underneath it's bottom, just for known weight, not magnetic properties):


Potential Energy (Work):
0.006kg * 9.8m/s * 0.0762m = 0.00448056 J (4.48mJ)


Power:
The lifting occurred on days with 60% average humidity about twice a minute (every 30 seconds):
0.00448056 J / 30s = 0.000149352 Watts  (0.149352mW)


Under these isolated, micro circumstances, it would take roughly 10,000 tiny 6 inch birds to create about 1.5 Watts of electricity. Yes, that would be absurd to scale it that way.


Luckily there are so many physical and chemical principals at play (check out the 'drinking bird' Wiki), it would seem there are many opportunities to re-think a system solely for the purpose of power generation. I read (and saw photos/videos) that an artist built a working 6.5 foot high version (vs the dainty 6 inch one tested here), which was again for 'art and novelty', not power generation. This shows at least the physical scalability.


However small at this level, it does show measurable, clean, free energy that runs reliably over long periods - and dosen't challenge any known science.


Hope this is of some relevance here.

[Tom Booth]

You can't.

You can extract energy from an environmental temperature difference, but there is absolutely no way to create a temperature difference using a heat exchanger then use that difference to generate more energy than was required to power the heat exchanger in the first place.

Why wouldn't this work?

A heat engine converts heat into work, Right?

If, just for the sake of argument, or a place to start as an example, you have a very efficient heat engine that can convert 70% of the heat delivered to it into useful work output with 30% waste heat and a Heat Pump with a COP of 3 or higher.

The heat pump can remove 3 times more waste heat from the engine than the energy required to run the heat pump. (It can remove the 30% waste heat with just 10% of the heat engines 70% work output).

That leaves 60% work output from the heat engine to be used for other purposes such as generating electricity.

If the heat engine is running directly from ambient heat, then the heat pump is not needed as a source of heat/energy to run the engine. All it has to do is remove the waste heat not converted into work by the engine.

If you had an engine only 40% efficient leaving 60% waste heat to be removed, you would still only need 20% of the work output to remove the waste heat and have 20% left over for the production of electricity.

Heat pumps can have a COP of much grater than 3. Some are as high as 10.

And please say something other than it violates the second law of thermodynamics.