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Was: Moss/Lichen on roof, now we are into pollution.
Franz Heymann wrote:
I have read a report one experimental fuel cell unit installed in Holland, where it was mentioned that "At the point of shutdown, the unit was also sustaining a power generating efficiency of more than 46 percent, well above a conventional combustion-based power plant that typically generates electricity at efficiencies of 33 to 35 percent". That is typical of an old station running coal or gas, built to 60's standards. Noit a modern set. That does not sit well with whoever it was who recently said something about conventional power stations operating at 60%. Depends on what you mean by conventional. The key to efficiency is getting your working fluids temperature and pressure way up, and the final exhaust way down. Steam turbines with ultra superheated steam going through multistage turbines with condensors on the back end to get the back end temp way down will do better than 50%. Gas turbines with extremely high combustion temperatures, whose exhaust then heats water to drive a steam turbine, do even better. If the coolant water at around 40-60C is then fed to housing next door for heating purposes...you are getting up towards 75-80% usage of thermal energy released. And the last little bit goes to help you farm fish in the cooling tanks :-) So, two points - in an overall energy and fuel conservation analysis, efficiency is not the primary problem. If you can use waste heat to save heating oil being burnt - example, build a bakery next door and use the heat to run the proving process, and bake bread at the edge of the furnace, or use waste heat to heat greenhouses to grow vegetables, or to farm fish or whatever - then you have an *ovearall* more efficient system anyway. - in an overall carbon neutral scenario, you want to reduce the conversion BY ANY MEANS of fossil fuel to carbon dioxide. I am not sure what fuel cells produce, but the carbon has to end up somewhere. If they are running on fossil fuels they don't really solve the problem. Whereas burning waste paper in a combined heat/power set can be extremely inefficient, as long as the heat ends up reducing fossil fuel usage and generateing SOME power. Because paper comes from carbon that has been taken OUT of the air by trees. The trouble is that neither the governments nor the power industry has any real incentive to either do the OVERALL analsysis, nor to embark on co-operative projects to utilise e.g. waste heat. If someone could only come up with a plant that I simply stuffed full of junk-mail and which heated my house, generated most of my electricity, and allowed me to run a few pipes rund the garden to grow vegetables in winter from....at similar cost to an oil boiler... Franz |
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