Measure | Instead of | £/tonne CO2 saved | Notes and assumptions |
---|---|---|---|
Renewable heat | |||
Air source heat pump | Oil fired central heating | 568 | RHI at 7.3 p/kWh assuming COP (coefficient of performance) is 3.2 |
Ground source heat pump | Oil fired central heating | 1462 | RHI at 18.8 p/kWh and assuming COP of 3.2 |
Biomass | Oil fired central heating | 504 | RHI at 12.2 p/kWh |
Solar hot water panels | Oil fired central heating | 719 | RHI at 19.2 p/kWh |
Renewable electricity | |||
Solar PV panels | Gas power station | 450 | FiTs at 15.4p/kWh plus half the export tariff of 4.5 p/kWh |
Solar PV panels | Coal power station | 194 | as above |
Wind turbine 1MW | Gas power station | 365 | FiTs at 9.8p/kWh plus half the export tariff of 4.5 p/kWh |
Wind turbine 1MW | Coal power station | 157 | as above |
Onshore wind farm | Gas power station | 101 | Renewable Obligation certificates (ROCs) - latest price £44.10 /MWh. Onshore wind gets 0.9 ROCs per MWh. |
Onshore wind farm | Coal power station | 44 | as above |
Insulation | |||
External wall insulation | Gas central heating | 289 | £11,000 cost paid for by ECO grant, savings 1.9 tonnes/year according to the EST, over 20 year lifetime [2] |
External wall insulation | Oil central heating | 201 | As above |
Cavity wall insulation | Gas central heating | 45 | £500 cost, grants only available to qualifying householders under the ECO, saving 0.56 tonnes/year according to the EST, 20 year lifetime [3] |
Cavity wall insulation | Oil central heating | 31 | As above |
Cavity wall insulation is easily the biggest win, however, a lot of that has been done already and DECC seems to think there aren't many more easy fill cases left [4]. External wall insulation savings are comparable with FiT levels for PV and wind. Grants for external wall insulation come from the Energy Companies Obligation (ECO) which is linked to the Green Deal. You do not need to be on benefits to qualify for help with these. However, grants for cavity wall insulation are now means tested (see Green Deal teething problems).
The RHI carbon savings are expensive compared to the others. It will be interesting to see if the RHI triggers lower prices, as happened in the case of PV panels: when the FiTs were introduced there was massive take-up followed by rapidly decreasing costs. The result was the FiT tariffs came down very quickly. However, this scenario is much less likely in the case of the RHI because the technologies are not particularly high-tech and expensive to make.
The RHI is aimed at households off the gas grid, which is why I have used the oil fired central heating case to calculate savings: in a home with gas the carbons savings will be a little lower and hence the costs per gram saved higher.
You will notice that it makes a big difference if you consider our solar panels to be displacing gas power stations or coal. I consider it highly unlikely they will displace nuclear because we mainly use nuclear for base load and the older power stations are being decommissioned anyway. The carbon savings would be minimal in that case. In 2012 the proportion of our electricity generated from coal increased from 30% to 43% [5]. This is because the global price of coal is much reduced which is in turn due to the USA exporting more because of their increasing use of shale gas. So their cheap gas is putting up our carbon emissions.
Carbon savings from wind are much cheaper than from PV panels, plus wind turbines work all year round whereas PV panels do almost nothing for half the year. Still, PV panels are much more popular. The installed base of PV panels increased by 1270% between 2010 and 2011 compared to a 15% increase in onshore wind. Offshore wind gets more than twice the subsidy compared to onshore: 2.0 ROCs/MWh versus 0.9.
Notes on the table
I have ignored the carbon emissions due to manufacture and installation of any of these. This omission is most serious for PV panels but even then it only comes to about 50 g/kWh generated [6], compared to more than 900 saved for coal power stations.
My estimates are based on carbon emission from DUKES [7]
fuel oil for central heating | 267 g/kWh |
gas for central heating | 185 g/kWh |
electricity - overall mix | 443 g/kWh |
coal power stations | 912 g/kWh |
gas power stations | 392 g/kWh |
The COP values for heat pumps are high values taken from an EST field study [8] which is a little out of date. Arguably GSHP should do better than this - say 4.0 which would make the savings £1200/tonne.
[1] The Heat is On for Householders (www.gov.uk 12 July 2013)
[2] Solid Wall Insulation Energy Saving Trust
[3] Cavity Wall Insulation Energy Saving Trust
[4] Estimates of home insulation levels in Great Britain (www.gov.uk)
[5] UK energy statistics show big jump in coal-fired electricity last year The Carbon Brief Feb 2012
[6] Energy and Carbon Emission: the way we live today Nicola Terry (UIT Ltd. 2010)
[7] Digest of UK Energy Statistics (www.decc.gov.uk, 2012)
[8] Getting Warmer - a field trial of heat pumps (EST, 2010)
No comments:
Post a Comment
Comments on this blog are moderated. Your comment will not appear until it has been reviewed.