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How to model biomass boiler?

asked 2015-08-27 10:17:12 -0500

Waseem's avatar

updated 2015-11-12 15:29:34 -0500

What is the best way to model Biomass boiler in EnergyPlus? Is it by using OtherFuel1 and FuelFactor objects or there is another way of doing it? If it is using FuelFactor then from where I can find all the values that needs to input in this object (e.g. C0$_2$ emission factor, CH$_4$ emission factor etc.)?

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answered 2015-08-27 13:37:22 -0500

updated 2015-08-27 19:02:54 -0500

Using OtherFuel1 is how I've done it in the past. I was only concerned with energy so didn't look at setting fuel factors. Given that you're also not particularly interested in the emissions, you can safely ignore the FuelFactor as all it does is feed into the reports, AnnualBuildingUtilityPerformanceSummary - Site and Source Energy table, EnvironmentalImpactFactors, and SourceEnergyEndUseComponentsSummary. It has no effect on the energy model.

If you were interested in GHG emissions, say for predicting a carbon footprint, the values you use will depend on what you're using it for. @JasonGlazer has already answered with an EPA source so I'll give an answer reflecting research/business reporting in a UK context using the Defra emissions factors for company reporting which are available from here.

Scope 1 emissions are those produced by burning fuels. In this methodology, biomass CO$_2$ emissions are considered to be reabsorbed by new growth so the GHG potential from that CO$_2$ is set to zero. The scope 1 GHG emissions are therefore only those from N$_2$O and CH$_4$ produced during combustion which are not considered to be reabsorbed.

scope 1 emissions from biomass
Scope 1 (product of combustion) GHG emissions from biomass

Scope 2 emissions are from electricity used directly in the organisation so not relevant here.

Scope 3 emissions are upstream emissions - the embodied carbon of producing and delivering the fuel. This would include agricultural emissions from growing the trees and fuel used in delivering the biomass to the building.

image description
Scope 3 (upstream) GHG emissions from biomass

Out of scope For completeness, although the direct CO$_2$ emissions from burning the biomass are considered to be out of scope for the purposes of calculating a carbon footprint, there are some figures provided for this as out-of-scope emissions. The factors recommended are in this table.

image description
Out of scope (expected to be reabsorbed) GHG emissions from biomass

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Thanks @Jamie Bull for your detailed answer, if someone is interested in only energy consumption (like you in past) so he/she should not be worried about fuel factors and only setting OtherFuel1 and using correct efficiency curve can do the job?

Waseem's avatar Waseem  ( 2015-08-27 14:57:25 -0500 )edit

That's right. You might also want to look at the system setup - a buffer tank for long slow burns is usual.

Jamie Bull's avatar Jamie Bull  ( 2015-08-27 15:00:25 -0500 )edit

@Jamie Bull: Yes, there is a buffer tank, which is also connected to gas boilers as well. See This for configuration.

Waseem's avatar Waseem  ( 2015-08-27 15:08:12 -0500 )edit

answered 2015-08-27 12:03:36 -0500

I think using a Boiler:HotWater and setting the FuelType to OtherFuel1 would be a reasonable approach. As far as a source for the emission factors needed in the FuelFactor object you could use:

But the problem is that these only reflect the carbon released when burning biomass and not the carbon absorbed. Of course unless the biomass is gathered on site a significant amount of indirect emissions may occur for processing and transporting. You might want to look at this paper:

CO2e Emissions from Biomass and Biofuels

It is a difficult question that requires some significant analysis for the particular type of biomass and location. You might want to ask the vendor who will be supplying the biomass.

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Asked: 2015-08-27 10:17:12 -0500

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Last updated: Aug 27 '15