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Archive for the ‘DER Calculation’ Category

Biodiesel will almost certainly be a recognised fuel under to upcoming changes to building regs, opening the door to biodiesel CHP as a way to meet increasingly stringent limits on emissions. While a number of big urban developments will breathe a sigh of relief at the news, it’s not all plain sailing. (more…)

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The new SAP has a revised carbon intensity for grid electricity (set in the consultation at 0.591 kgCO2/kWh, up from 0.422). This has a big impact on the resulting carbon emissions from heat pumps, in most cases making them higher than emissions from the worst boiler you can legally install. This goes for both air source and ground source.

You can see from the graph above that at a grid carbon intensity of 0.591 even a GSHP with a COP of 4 is struggling to outperform an 86% efficient gas boiler. The real world COPs seen at Barratt’s Chorley scheme (2.6 for GSHP) and recent field trials by Mitsubishi  (3.0 – 3.4 for ASHP according to a letter from Mitsubishi in the latest CIBSE mag) mean that heat pumps would emit significantly more carbon than the boiler.

And yet in the low carbon transition strategy, DECC state that heat pumps will be eligible for the Renewable Heat Incentive (pdf – see para 1.22), rewarding them for being a renewable energy source! What the hell are they thinking?

Here’s how I did the numbers:

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Love them or hate them, liquid biofuels are increasingly being put forward as a renewable fuel for CHP. Currently they’re eligible for ROCs and so appear to be considered renewable by BERR and OFGEM.

But when I spoke to the SAP team at BRE, not only did they confirm that liquid biofuels aren’t considered under SAP, they also said that “because of mounting doubts over the extent of emissions from biofuels”, you have to use the emissions factor for oil when carrying out your SAP calcs. Did they expect the treatment of biofuels to change for the 2010 review of SAP? Adamantly, they did not.

Then I called the BREEAM helpline. They told me that liquid biofuels also aren’t considered under the Code for Sustainable Homes. So no help in scoring points under ENE1 or ENE7.

So liquid biofuel CHP is eligible for ROCs but will do little for your Part L and Code requirements. Without achieving these requirements, the case for biofuel CHP for new buildings is severely undermined. Obviously this situation could change. With CLG on the lookout for ways to meet the 2016 zero carbon homes target, there might be considerable pressure applied in favour of making biofuel renewable under SAP. But for now the official line is that biofuels are not a solution for carbon reduction in new build.

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I’ve been spending some quality time with spreadsheets and have an update on the way building regs for housing treats CHP. It’s not as simple as I thought here, although the result is similar. The incorrect method I wrote about a few weeks back is still in use, but it’s different from what’s happening in SAP 2005. Here’s a breakdown:

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Following on from here, I have been chasing BRE & CLG to clarify the situation. The sorry response is that no-one was really aware of the potential implications of this piece of policy. So it’s official, at this point it is not possible to include the power output from communal on-site wind turbines, even where connected via a private wire network.

I have been tasked by Ted King, Head of Building Regs at CLG, to formally write to all stakeholders highlighting the issues so that they can be considered (not necessarily resolved) during the revisions for SAP 2009/10 for the next Part L update. The good news is that this work is already underway to be ready for the consultation process in January 2009. So, no comfort for my client, but perhaps others will be able to avoid this.

For what it’s worth, I also contacted the BWEA to check whether they were aware of the situation, and no they were not but obviously very interested to make sure that their industry is not penalised in this manner in the future.

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