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Renewables vs shale gas

By Dave Elliott
As a parting shot, after standing down as DECC’s Chief Scientific Advisor at the end of July, Prof David MacKay produced a comparison of renewables (wind and solar) and shale gas:

The headline figure (as picked up by the Telegraph: was that wind farms cover around 700 times more land area /kWh of energy produced at the site than shale gas wells. However, as usual with renditions of MacKay’s approach to land-use comparisons, this simple statistic is arguably a little misleading. As he admits, the actual area covered by wind turbine bases and access roads is very much less that the area covered by the wind farm, most of which can be farmed as usual. So, using his figures, the wind turbine /gas well land use ratio falls from 700:1 to 18:1

There are also other aspects that need to be considered in the comparison, some of which he covers in side notes. The energy content of the shale gas emerging from the well isn’t the same thing as the electricity output of a wind farm (or solar farm)- the gas has to be burnt in a power plant to generate energy (at 50% efficiency at best) and that also takes up room. This might reduce the wind turbine /gas land use ratio from 18:1 to perhaps 9:1 or less. And unless we condone the release from the gas-fired power plant of CO2 to the air, there will also have to be a carbon capture plant and a CO2 gas storage system- taking up a large area somewhere, and reducing the efficiency of the gas plant. That might add another factor of 2 or more, so maybe we are down to a ratio of 4:1 or less.

Hydraulic fracking also uses very large amount of water– that has to come from somewhere. It also creates large amounts of contaminated water, which has to be stored and/or treated, presumably somewhere else. It’s hard to know how to take these factors into account in land use terms. Another factor of 2? In the final analysis, overall, there might not be that much in it, if the land-use comparison is done fairly, at least for on-land wind, depending on location. And of course the whole land-use comparison collapses if we are talking about offshore wind. Or for that matter, offshore shale wells.

MacKay also looks at ground-mounted solar farms. Certainly solar farms (as opposed to roof-mounted PV arrays) do take up land space, on MacKay’s figures, around 8.5 times more than for wind turbines/kWh, although less than the total equivalent wind farm area. But, rebalancing the comparison, the Solar Trade Association has pointed out that much of this land can be grazed and most (perhaps 95%) of it can be used for wild flower growth, aiding biodiversity:

MacKay also looks at the truck movements associated with each option. His figures for solar and wind (nearly all during construction) seem high, those for shale gas low: he assumes all water is piped to and from the shale gas well site, but surely some water, and certainly fracking chemical fluids, would have to be tanked in throughout the operation, while some wastes would have to be tanked out. As for visual intrusion, his choice, for comparisons sake, of 10 temporary shale gas-drilling towers, may well be perceived as uglier but less invasive overall than his choice of 87 much taller 2MW wind turbines, though it will surely depend on the location. Some people positively like the look of wind turbines, seeing them as elegant symbols of low-impact energy extraction. It’s hard to see drilling rigs like that, although we have yet to have major shale gas projects in the UK to test that out. If, as it has been suggested, the UK may have 1000 wells started each year, attitudes may harden, as projects attempt to go ahead and impacts become apparent. My favorite unknown is whether excess gases will have to be flared off. That would make for quite a spectacle in rural areas…

At it stands, DECC’s most recent public opinion survey found that 79% of those asked backed renewables like wind and solar (82% backing solar, 67% on-land wind) while only 24% supported shale gas extraction:

There are also wider strategic issues: an emphasis on shale gas could undermine the development of renewable energy and efforts to respond to climate change. Scientists for Global Responsibility (SGR) and the Chartered Institute of Environmental Health (CIEH) have produced a report reviewing current evidence associated with shale gas extraction. SGR Director and report co-author, Dr Stuart Parkinson, said: ‘The evidence we have gathered shows that exploiting yet another new source of fossil fuels such as UK shale gas is likely to further undermine efforts to tackle climate change. We need to focus on low carbon energy sources, especially renewables, together with concerted efforts to save energy.’ The report calls for rethink, arguing not only that impacts may be high and regulatory oversight insufficient, but also that on-land wind power may be cheaper than shale gas.

The governments current decarbonisation policy envisions fossil gas being replaced as a heating option by green electricity from wind and solar and by nuclear electricity, used to power heat pumps. See my next post. That could make for a huge saving in gas – and emissions. And it would reduce the need to import increasingly expensive gas as north sea reserves dwindle. There will still of course be a need for gas to run electricity generating gas turbines, with some of those being used at times to balance variable renewables like wind and solar. However, although some new more flexible gas plants may be needed as old ones retire and renewables expand, the extra gas required for balancing, over and above what is used by the gas CCGT units at present, will be relatively small. And, as the Pugwash 2050 scenario explored, using the DECC calculator, if UK renewables expanded to 70% and alternative supply and demand side balancing options were developed, the need for gas for power generation would fall, so that, with proper commitment to energy saving, by 2050 well under 10GWof gas fired capacity would be needed. And increasingly it could use green gas- from biomass/waste AD and also possibly via surplus wind/PV to gas conversion, some of this also being use at high efficiency in CHP plants feeding district heating networks. There are disagreements about how much biomass could be available and used, but the Tyndall Centre says that by 2050, 44% of the UK’s energy requirements could be met by the increased utilisation of biomass, including household waste, agricultural residues and home-grown energy crops i.e. with no imports:

It is possible than gas could find a new market in transport, assuming the governments plan to see that electrified via a shift to electric vehicles is not successful. Certainly SNG/CNG could play a helpful role in fuelling trucks and large vans. But, as the Tyndall report suggests, much of this could be green gas. So why exactly do we want all this shale gas? Perhaps, with, tragically, renewable expansion already being constrained by government policies, it’s to compensate for that and also in case the nuclear expansion programme fails to materialize.

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