HOMER Energy Support

Biogas energy content

Last Updated: Jul 21, 2016 03:09PM MDT

I am a regular user of the homer software. I have some doubts related to the lower heating value of biomass gasifier fuel.  In homer, it is a sensitivity variable. If I give different values to LHV, the results did not reflect any variation. There is no change in cost of energy, fuel cost, specific fuel consumption, etc. for different LHV of fuel.

 

In HOMER, for a generator that consumes biogas, you specify the fuel consumption in terms of quantity of biogas versus electrical output.  Using the gasification ratio, HOMER can calculate the resulting quantity of biomass feedstock consumed to produce electricity.  You specify the price of the biomass fuel in terms of dollars per quantity of biomass feedstock.

HOMER does not use the LHV of the biogas in those calculations, so that variable does not affect the consumption or cost of biomass, and hence it does not affect the cost of energy.  HOMER uses that LHV variable only to calculate the resulting efficiency of the biogas-fueled generator.  If you look at the generator tab in the Simulation Results window, you will see that the ‘mean electrical efficiency’ does change as you change the value of the LHV-of-biogas variable.

In the real world, the LHV of biogas affects the fuel curve inputs.  The lower the energy content of the biogas, the more biogas the generator will require to produce a fixed amount of electricity.  So even though HOMER makes it easy to do so, one should not change the energy content of the fuel without also changing the fuel consumption of the generator that burns that fuel.  You can us a ‘linked sensitivity’ to make the fuel curve inputs change with the LHV of the biogas.  For more information, please look up ‘linked sensitivity’ in the index of the help file.

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