Tesla's Ambient Heat Engine Theory - Right or Wrong ?

[Bob Smith]

Any kind of energetic imbalance can be harnessed and transformed to power a mechanical or electrical system. This includes temperature imbalance. The example of Peltier modules makes this clear, as does the Sterling engine. The former converts difference in temp to potential difference; the latter to mechanical energy. Tesla's words to this effect seem far from outlandish. In fact, they sound like good common sense.

The question becomes even more intriguing when we look at Viktor Schauberger's work with vortexes and their exothermic properties. Hmmm. Maybe there's more to Tesla's words here than sheer musing.

Onward, I dare say, into the throng of discussion!!   
Bob

[angryScientist]

With the engine you want as high an efficiency as possible while operating at a low temperature differential. That is difficult because the greater the temperature difference the better efficiency.

We want the highest coefficient of performance (COP) from our heat pump. Unfortunately heat pumps operate a low temperature differentials. The higher the temperature differential the lower the COP.

The trick is to find the right technologies. The room for greatest improvement is with the engine.

Here are links to one possible engine and some links to pertinent information on heat pumps.

http://www.infinityturbine.com/ORC/ORC_Waste_Heat_Turbine.html
"Geothermal and Waste Heat Organic Rankine Cycle:
The technology developed using a ORC (Organic Rankine Cycle) can operate off any heat source, with a minimum of 125 deg F temperature differential between the heat source and cool liquid flow heat sink."
"If you have a hot water flow rate of at least 180 F (80 C) and 3 gallons per minute (11 liters/min) then you can produce electricity."
"Typical ORC range for this equipment is 80 - 120 C."


http://www.energy.wsu.edu/Documents/IndustServFactsheet-HeatPumps-May%2009.pdf
Industrial Heat Pumps for Low-Temperature Heat Recovery
"Temperature considerations
Vapor compression heat pumps can achieve maximum temperatures of 220 degrees Fahrenheit with temperatures rises of as much as 100 F. To achieve greater temperature rises, two-stage systems can be used. Each stage uses its own refrigerant designed for a specific temperature range."

http://www.heatpumpcentre.org/en/aboutheatpumps/heatpumpsinindustry/Sidor/default.aspx
"Mechanical vapour recompression systems (MVRs)...
Because one or two heat exchangers are eliminated (evaporator and/or condenser) and the temperature lift is generally small, the performance of MVR systems is high, with typical coefficients of performance (COPs) of 10 to 30. Current MVR systems work with heat-source temperatures from 70-80ºC, and deliver heat between 110 and 150ºC, in some cases up to 200ºC. Water is the most common 'working fluid' (i.e. recompressed process vapour), although other process vapours are also used, notably in the (petro-) chemical industry."

[Tom Booth]

The point is that you cannot operate it like this.  It is impossible to extract all the energy BEFORE it gets to the cold sink at 150K as to do so you'd need a even 'colder sink' than the 150K to achieve it.

Who says?

I think Carnots formula basically says that it would be impossible for your "waste heat" to be colder than your heat sink. Which is only logical.

So to reach Carnot's maximum theoretical efficiency you would have to extract or convert enough energy so that your "waste heat" was exactly the same temperature as your sink. That is as cold as you could go. Carnot does not say that this would be "IMPOSSIBLE". My point is, the numbers or percentages are deceptive if you don't keep in mind that Carnot uses absolute zero as a baseline.

An engine might have 2% "Carnot Efficiency" depending on the TD and still operate as Tesla suggested. In the context of Tesla's proposal Carnot efficiency doesn't mean much of anything.

It would be like saying, I have a machine that can turn sea water into pure gold, unfortunately it can only convert 1%. booo hooo hooo.

Who cares? at 1% efficiency you could produce 1 pond of gold for every 100 pounds of sea water. Would anyone lament over this poor efficiency rating?

[Tom Booth]

There is a guy on YouTube who posted a couple videos that I think warant some careful consideration in this context.

He discovered by accident that he could take the flywheel off one of his little model Stirling engines.

http://www.youtube.com/watch?v=DyPxNNJQo9M

http://www.youtube.com/watch?v=cAyw_dOioMU

My question or observation;

If "ALL" the heat entering the engine cylinder is not being converted, how on earth can the piston make its return stroke, apparently against the heated/expanding air in the cylinder ? Without a flywheel to push the piston back it can, I think, only be assumed that ALL the heat delivered to the cylinder is being converted, and possibly then some, so that the heated and expanded air becomes cold and contracts drawing the piston back. There is no other force involved.

Note that in both engines he had to make provisions to keep the piston from banging against the end of the cylinder on its RETURN STROKE, as it moved BACK TOWARDS THE HEAT SOURCE! To me, logically, this seems to indicate that there is some tendency for this engine to convert MORE HEAT than is being delivered, otherwise it would tend to creep or fly out further and further AWAY from the heat source and out the end of the tube rather than being drawn further and further IN necessitating a rubber bumper or spring be installed to prevent its banging against the end of the cylinder on the return stroke.

Also, a glass test tube makes for extremely POOR heat dissipation, yet this engine is running very rapidly. It isn't waiting for the heat to dissipate through the glass. The heat is somehow "disappearing" in a fraction of a second allowing the piston to return with no flywheel with any stored momentum to push it back inward against what one would expect to be hot expanding air inside the cylinder.

All things being relative, I see no reason why one might not be able to achieve a similar result using Ambient heat as the heat source.

[angryScientist]

Gianna, you look a little confused.
Do you understand what we mean when we say that the heat disappears? It means the heat disappears.

The energy of the system stays the same, the same amount of Joules remain within the system. The amount of heat within the system has decreased. There are less calories or BTU with in the system (for that moment at least) and more Watts or ft/lbs available.

http://cnx.org/content/m42234/latest/?collection=col11406/latest

Perhaps I can point out how that happens in this picture.

Let's say there are 10,000 BTU in figure (a) summing up what is in the source and the sink.

In figure (b) let's say that the engine runs for 1 second (so we can calculate the energy easily) it outputs 1 hp that is .706789 BTU/sec. So after that engine has run there will only be 9999.293213 BTUs left in the system plus 1 hp. There are still going to be 10,550,558.5262 Joules in the system, same as in figure (a).