Sterling Engine to Utilize The Wasted Heat Energy in Thermal Power Plant

According to Wikipedia the eficiency of Sterling engine is upto 40% besides one of the cylinder is to be kept heated and the other one cold.

Economiser (feed water heater) is used with boilers and Heat Recovery Steam Generators are used with gas turbine.

Yes, but many power plants just waste the heat energy of the steam coming out of the turbine by exchanging the heat with a open water cycle(cooling tower) and then use condenser to bring the fluid into working state.

I certainly disagree with you, in all of todays power plants Economizer is there prior to the cooling tower.

I assume that since you can readly see the cooling towers ejecting hot gases while the economizer is there to be pointed out by some one to you therefore you have this misconception.

yes I do know that they use some of the heat energy for economizer, but nevertheless I thought even the remnant heat could be utilized in a better way. Not only a stirling engine, may it be any other method.

Because I feel there should be something that can make use of the wasted energy. Some use it for district heating, etc. By this they handle the remnant heat in a better way.

Andyarok: It will probably be easier to understand that modern power generation is already highly optimized, once you include a couple more vital factors into your analysis of 'efficiency'. Currently, your analysis leads to the ideathat modern power generation schemes are not highly optimized, creating significant and avoidable waste (noting the heat expelled to the atmosphere from cooling towers). Essentially you are arguing that because methods exist to generate more electricity from each unit of fuel used to heat the plant, the plant is not optimized. What you analysis is missing are the other significant costs. Depending on the system, fuel costs can run the gambit from dominant, to zilch. Many times the lifetime fuel costs are dwarfed by capital required for construction, regulatory hurdles, logistics challenges, staffing, and maintenance. While there are numerous ways to extract more energy from each unit of fuel, it would be wasteful in most cases to do so. The additional cost to build staff and maintain the stirling engine and attached generator, would increase in revenue from additional electricity. Another thing to consider is that heat engines require a difference in temperature to operate, so real heat engines will always expel heat, there is no known way to use all the heat generated by the fuel, and so it will always appear that heat is being wasted (to the uninitiated). BBB

You are so right on the reasons for the fact that most electricity generation plants efficiency is somewhere between 30 and 40%: the cost to go higher in efficiency is not worth the gain.

Just learn the base thermodynamics behind the whole picture: Forget which cycle it is and learn the base rules in thermodynamics.

Sterling engines are not different from all the other: they indeed have shown efficiencies in the range 50 to 55% and even higher. But these are specific lab results.

It all comes down to the difference between the high and the low temperature source: the higher this gets the higher the potential efficiency can get. On top of this you add the carnot efficiency, which can be ugly: this reperesents how nice you can realise the energy tranfer between the thermal sources and your working fluid.

In internal combustion engines this is acceptable. In external combustion systems this can get enormously ugly as you have the get the heat out of the burning process into the steam or gas. You rapidly loose a few 100°s

To improve the total efficiency of a thermal electricity generation plant it is important to find other uses for the heat which is still at an acceptable level.

http://www.epa.gov/chp/

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http://www.google.com/search?hl=&q=combined+heat+and+power+efficiency&sourceid=navclient-ff&rlz=1B7GGLL_enUS387US387&ie=UTF-8&aq=3&oq=Combined+Heat+and+Power

Thank You all for making me understand. I had this doubt when I was visiting a power plant in India. I thought they were not using the heat content effectively. I thought of making of something like district heating, but I realize that, as the temperature here already soars past 40 more often than not its not gonna be much of an use. May be in cold countries will be an option(Techniques like District heating, etc)...

Looks like you are on the right track, Andy...

Another way to look at the situation is that a "little bit" of heat energy at 1000F is much. much more economically attractive than "a lot" of heat energy at 120F.

The usage of "low grade" heat (even of it is free) thermodynamically requires "big equipment" and large capital expenses.

Yes......we as engineers have recognized that, this seems very wasteful....but there is no other way.

And, yes....chp systems make a lot of thermal sense.. ( Suggest that you review the planning and organization of CHP systems cities and towns in Scandinavia)

This question has been asked many, many times before. Most recently by US Congressmen.

BTW, if you develop a material that still has strength at 2000-2500F and can be used in boilers and power plants.....the world will eat a path to your door !!!

-MJC

Hi All, a working prototype arrangement was being tested by a UK racing engine company Prodrive, I understand it was quite successful