Commentüs on: CHP and SAP - part II http://carbonlimited.org/2008/03/20/chp-and-sap-part-ii/ low carbon energy and engineering Fri, 05 Dec 2008 11:38:27 +0000 http://wordpress.org/?v=MU hourly 1 By: Richard http://carbonlimited.org/2008/03/20/chp-and-sap-part-ii/#comment-575 Richard Fri, 25 Apr 2008 15:18:38 +0000 http://carbonlimited.wordpress.com/?p=248#comment-575 Just a quick note to say I'm glad to see I'm not the only one with some concerns over how SAP treats CHP and the +40% assumptions frequently being made about reductions in CO2 emissions achievable via CHP. As application of benchmark SAP and other standardised data is commonplace in assessing energy demand and potential reductions at the feasibility stage many professionals could obviously exploit this problem in SAP as a method of achieving the 20% renewable obligation in London (under the revised London Plan) as the London Plan allows reductions in CO2 via CHP to be deducted from overall emissions prior to the inclusion of renewables. Just a quick note to say I’m glad to see I’m not the only one with some concerns over how SAP treats CHP and the +40% assumptions frequently being made about reductions in CO2 emissions achievable via CHP.

As application of benchmark SAP and other standardised data is commonplace in assessing energy demand and potential reductions at the feasibility stage many professionals could obviously exploit this problem in SAP as a method of achieving the 20% renewable obligation in London (under the revised London Plan) as the London Plan allows reductions in CO2 via CHP to be deducted from overall emissions prior to the inclusion of renewables.

]]> By: Casey http://carbonlimited.org/2008/03/20/chp-and-sap-part-ii/#comment-570 Casey Mon, 21 Apr 2008 14:23:33 +0000 http://carbonlimited.wordpress.com/?p=248#comment-570 Thanks for spotting that Jack. The problem is in the first equation rather than the second. The first should be: ((Eg / ηe) - Ee) / (ηh / ηe). Looking forward to discussing this with you. -C Thanks for spotting that Jack. The problem is in the first equation rather than the second. The first should be: ((Eg / ηe) - Ee) / (ηh / ηe).

Looking forward to discussing this with you.

-C

]]> By: Jack http://carbonlimited.org/2008/03/20/chp-and-sap-part-ii/#comment-569 Jack Mon, 21 Apr 2008 11:49:06 +0000 http://carbonlimited.wordpress.com/?p=248#comment-569 hi, I'd like to have a discussion on the break down of the calculation. But here is a mistake I found in your explanation. ((Ee / ηe) - Ee) / (ηh / ηe) Where: Ee is the emissions factor for electricity offset (0.568 kgCO2/kWh for SAP) ηe is the electrical efficiency of the CHP engine ηh is the thermal efficiency of the CHP engine Conceptually, this is pretty convoluted. Another way to get to the same result is this: Eg / ηh - Ee x (ηe / ηh) I would think that if two expressions have the same results, Eg in the second expression should be Ee. Would you think this will affect your other calculation? Cheers, Jack hi, I’d like to have a discussion on the break down of the calculation. But here is a mistake I found in your explanation.

((Ee / ηe) - Ee) / (ηh / ηe)

Where:

Ee is the emissions factor for electricity offset (0.568 kgCO2/kWh for SAP)
ηe is the electrical efficiency of the CHP engine
ηh is the thermal efficiency of the CHP engine

Conceptually, this is pretty convoluted. Another way to get to the same result is this:

Eg / ηh - Ee x (ηe / ηh)

I would think that if two expressions have the same results, Eg in the second expression should be Ee.

Would you think this will affect your other calculation?

Cheers,

Jack

]]> By: SAP and CHP - a dangerous muddle? « carbon limited http://carbonlimited.org/2008/03/20/chp-and-sap-part-ii/#comment-552 SAP and CHP - a dangerous muddle? « carbon limited Thu, 20 Mar 2008 21:42:57 +0000 http://carbonlimited.wordpress.com/?p=248#comment-552 [...] gives misleadingly high emissions savings for CHP, I got the methodology wrong. See an updated post here. Points 3 and 4 below are still [...] [...] gives misleadingly high emissions savings for CHP, I got the methodology wrong. See an updated post here. Points 3 and 4 below are still [...]

]]> By: emissions from CHP: the standard method is wrong « carbon limited http://carbonlimited.org/2008/03/20/chp-and-sap-part-ii/#comment-550 emissions from CHP: the standard method is wrong « carbon limited Thu, 20 Mar 2008 21:34:33 +0000 http://carbonlimited.wordpress.com/?p=248#comment-550 [...] emissions from CHP: the standard method is wrong [update 20 March: I’ve looked further into how SAP treats CHP and written it up here]  [...] [...] emissions from CHP: the standard method is wrong [update 20 March: I’ve looked further into how SAP treats CHP and written it up here]  [...]

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