... Efficiency of ~60% conversion of heat to
electricity have been achieve in full size power plants. I was not talking about
Co-gen. The use of a car size ICE no matter the fuel being NH3 or CH4 have an efficiency of
18-20%! ...
Ok Yes one can get higher over all conversion efficiency by using the exhaust heat of the upper stage as the input heat for a second lower stage, but doing that adds to the capital cost, which is the main part of the electric bill.
You say this has been done - where? and for what price do they sell their electric energy? The efficiency achieved is no greater than a single engine operating between the higher temperature heat source and the lower temperature heat sink.; however there are no single "working fluid" that can span the same temperature range that two different cascaded thermal engines with two different working fluid can.
Also I must ask you why you credit the ICE with less than half the efficiency that modern car ICEs have. Do you dispute the Stanford University study I quoted and gave link to? If you do, I can find many others than show more than twice the efficiency you state is possible. Lets have a little supporting MODERN references, instead of just claimed numbers.
Summary: co generation, when there is a need for heat, is very economical and is very widely used, but rarely if ever, I think is Combined cycle used commercially, because you have the capital cost of two power plants for only a modest increase in fuel conversion efficiency.
I note you second link is from 2008 when car's ICEs were not so efficient: Here is a graphic from 15 April13 article based on British Governent tests:
and here is some text form the article:
http://www.autocar.co.uk/car-news/industry/why-your-cars-diesel-engine-more-efficient-power-station said:
it may come as a surprise that a modern diesel engine is more efficient than a traditional coal-fired power station. The British government’s figures say 38 per cent of the energy put into a coal-fired power station comes out as useful work, whereas a good modern diesel engine is about 40 per cent efficient (at least when running steadily at its optimum speed). The latest Mercedes-Benz 2.2-litre diesel hits 42 per cent. Even the website of the Energy Saving Trust advocates the domestic use of Stirling* engines and diesels to generate energy rather than relying on conventional utilities. ...
So how can a relatively cheap diesel engine run as efficiently as a multi-million-pound power station? The answer, according to Roelant de Waard, Ford of Europe’s marketing sales and service boss, is electronic controls. He says: “The microchip has made it possible to control a car engine as precisely as the most complex power source.”
and as I mentioned in post 3163 that 38% power plant output is further reduced due to "extra losses in transmission lines, AC to lower voltage DC conversion, the charging and discharge loses of the battery (at economically reasonable rates with electrode polarization loss due to high current densities, not ideal "trickle" charge and discharge rates),..."
* The Stirling cycle is the only one than can CONCEPTUALY get to the Carnot efficiency limit, but is much too expensive - too many heat eachangers recuperators etc. The combind cycle also has twice as many of those - it is two separate heat engines - That is why I asked if it is ever actually used in a commercial market where cheaper power per watt is easily achieved.
