I am currently conducting thermodynamic analyses of a small-scale ORC with a biomass boiler as a heat source. To get reasonable and realistic results, I need the typical values of the biomass boiler's efficiency with the heating values of its fuel. It is known that the heating values differ from kind to another (woodchips, wood pellets, logs or agricultural materials such as straw), but the most used ones are ok. I found some providers through the web with efficiency up to 90-92%, however, articles what I need as a source of these information.
I highly appreciate your reactions
A biomass boiler may show less efficiency than a coal-, oil or gas-fired boiler. A typical thermal efficiency may be about 70 %. Reasons for loss of efficiency are:
- moisture (and ash, e.g., in case of straw firing) in the fuel.
- excess of air.
- entrance of uncontrolled air.
- relatively small-scale.
- incomplete combustion.
Are you only interested in heat, or combined heat and power? What scale do you refer to as small scale? Biomass boilers are generally much smaller than fossil fuel boilers, but I am not sure if you mean industrial scale or smaller, as in farm scale.
If you look at industrial scale boilers for CHP you can find typicall power to heat ratios in
DIRECTIVE 2012/27/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL
of 25 October 2012 on energy efficiency, amending Directives 2009/125/EC and 2010/30/EU and repealing Directives 2004/8/EC and 2006/32/EC
(annex 1) It also has ranges of heating values for different types of fuels. Beware that the total conversion efficiency is often related to the lower heating value of the fuel, leading to total efficiencies of more than 100% in some cases where flue gas condensation is applied in biomass boilers.
Thank you Alfons for your answer. Do you have some references for these values?
Niclas, The size I need is to power about 10KWe net output from an Organic Rankine Cycle. I mean to use the heat source to power the ORC. So, some article will be very appreciated.
No, these are experience factors - so much depends on design, fuel, and operation (full load, partial load)...
Thank you Carlos for you contribution. But without supported reference to any used parameters, it will make a doubt.
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