carbon limited

Via Tom N, a great article in BSJ on whether CHP (and CHP + cooling) actually has as much potential to reduce carbon emissions as the industry (and Ken Livingstone) would have you believe.

In general, I agree with James Thonger’s conclusions. However…

…it’s cheeky of him to use the carbon intensity of grid electricity from a CCGT instead of either the SAP figure of 0.422 or the actual figure of 0.455kgCO2/kWh. He’s just doing it to make a point and in doing so he adopts the same methods as the argument he’s trying to debunk. Shame.

Interestingly, the graphs showing carbon savings (or lack of) only consider the energy needs met by CHP. Plenty of heat and power will be coming from backup systems (grid and backup boilers) to meet total demand, which waters down the percentage of carbon savings from the whole scheme. So even if your CHP gives you carbon savings of 20% on the energy needs it meets, it might only reduce total scheme emissions by 5%.

How about display meters instead and save 10-20% of your carbon much more cheaply?

Like James, the carbon intensity that you use for building regs (and that the GLA ask for) of 0.568kgCO2/kWh for grid electricity displaced through local generation makes me uneasy. I spoke to BRE about this last year and they said it was so high because you’re reducing base load AND lowering the requirement for future generation plant. This can lead you to calculate that a scheme is carbon neutral when in fact it’s still a net energy consumer from the grid, which is plainly crap. We’re not worried about abstract future carbon – we’re worried about carbon today.

Alan Jones and team down there at the London Climate Change Agency are no dummies. They must know the score already. So why does the GLA continue to push so hard for CHP and tri-generation? I suspect it’s to get developers to fund the bulk of a communal heating and cooling network in London. This is a noble aim as it lets you switch to lower carbon energy sources in the future (fuel cells, biomass, energy from waste); but why don’t they just require communal heating and cooling? Then they can get off their bums and bring us all that lovely heat that’s going up the flue at SELCHP.