Posted 21 April 2010 - 12:16 AM
Posted 22 April 2010 - 06:01 PM
We don't have data on that yet, but we can make some approximations:
According to EnviroHarvest [link], a diesel engine releases 35% of the used fuel energy as heat through it's radiator. I've heard similar figures for water cooled engines. Lets use 35% as a figure.
For this calculation, lets say the engine runs at 25% efficiency. So, at 10 kWe, we're consuming 40 kW of gas heating value. 35% of that heat is 40 kW * 35% = 14 kW_thermal. Over one hour, that's 14 kWh_thermal, which converts to ~48 X 1000 BTU per hour. Which is less then the Yazaki systems you mentioned would need. But, their specs would seem to suggest you could get about 6.7 gpm of chilled water from a smaller system. There are also interesting places to recover even more heat from the system beyond the engine cooling water, but that is the quickest route.
I'm not yet fully versed on CHP systems, but I think they have a very interesting potential for integration with the systems we're designing. We'll definitely be looking at this in more detail in the future.
Posted 29 June 2011 - 03:32 PM
I also couldn’t found info about total efficiency…
This two facts are very important here in EU, because the licenses and supports depends on that…
Posted 10 July 2011 - 08:01 AM
OK 25% ENGINE efficiency for 10 kW el, means we are loosing 80% somewhere as heat. If we state that 35% are released by the radiator, another 45% are the difference to 80%. So about 35 to 40% of the headt can be expected from exhaust gas and other not removed heat along the motor and generator. Thats why modern CHP systems are very good isolated not only for nois, but for heat recovery.
In a good chp about 5 to 7% of the heat are realy lost. But how much heat you earn depends on the heat recovery system, the heat exchanger system in place and make.
But I have another concern regarding heat-production:
I recently canceled a project as consultant because the client did not provide any ideas about what to make with the heat. In today CHP's I follow the 1 : 2 = 20 kW el and 40 kW th theory. Even this is not the best CHP. I canceled the project because if you realy go only for electricity and do not consider any of the 40 kW th, that would mean:
You take 3 pices (kg) equally sized wood, 1 (kg) converts nicely to electricity and 2 (kg) are just droped badly away as heat, i.e is release to environment.
Can we afford this? Do we not have a greater responsibility regarding biomass usage?
Small GEK's can have a greate future too if the can be used to heat up a boiler and switch of if the temperatur is reached, and switch on if the temperatur of the return water drops below a certain °C. In this case your GEK is not running 8760 h/a but your make efficient use of energy and can still provide some electricity to the grid.
Or you may include a proper sized GEK into a system where you need process heat i.e. for fermentation processes, or drying processes, sludge-drying for gasification, milk powder production, pool heating. Producing thermal water for big community pools where heating costs are a major obstacle today.
Hence instead of taking the gas for a motor, I am looking too for a way to convert it to a liquide by yeast or bacterias i.e. "Clostridium carboxidivorans" and others.
From the 7 regenerable resources we have, 6 are best suited for electricity and thermal output. Only 1, the biomass, has the capability to be converted into liquieds to be used widely. Hence biomass plays the most important role of the 7 sources.
Josef - the swiss
Posted 23 December 2011 - 05:48 PM
Moreover I would like to know whether, in order to use both coolant and exhaust waste heat, it is better to use two separate heat exchangers or if there is another way.
Posted 12 June 2012 - 03:25 PM
You may safely assume that the coolant temperature is between 70C and 90C (I think GM reports that for their 3.0l Engine). The difficult question is the temperature of the exhaust gas. In an other part of the forum I asked this question, but no views even (probably the wrong part ) If we know this number we can make very educated guesses of where we should extract the heat and (as you suggest) whether we should use both heat flows. To me this is a very critical question for small gasifiers, as the heat is the determining factor for small gasifiers where they beat the huge beasts used elsewhere..
I hope this is read by one of the APL staff and that they can take action to measure that temperature,
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