In an update for the Sustainability by Numbers web site, Hannah Ritchie takes a new look at the late Prof. David MacKay’s influential 2008 energy study, ‘Sustainable energy without the hot air’, based on a recent study from the Oxford Smith School of Enterprise and the Environment, which found that renewables are much better placed now. She says it shows that the potential for solar PV and wind, on and offshore, are much larger than MacKay thought, with floating wind adding an extra new resource, and public acceptance now much higher, while costs are very much lower. It does seem that, a result of these and other changes, MacKay’s conclusions that renewables were not very viable now looks very dated.
The Smith School study estimated that the UK could produce 2,895 TWh of electricity each year from solar and wind. That’s almost double its estimate for final energy demand in 2050 and very much more than the 203TWh MacKay calculated for the ‘practical’ resource. It’s even more than the 2697TWh he estimated might be the theoretical UK ‘technical’ resource.
The new calculations assume offshore wind spread over 10% of the UK’s exclusive economic zone, while onshore wind would be used on 5% of UK land, where it can be combined with farming activities. 2% of land would also be used for solar PV, combined with farmland in ‘agrivoltaic’ projects. Roof top solar would be in addition, using no new land. But even if some of these land-use figures prove to be unacceptable, the practical renewable resource would still seem to be very large.
In its latest report, the National Infrastructure Commission (NIC) is also quite enthusiastic about the future, but says it will need sustained effort and ambitious targets: over the next 30 years the UK needs ‘a larger electricity system running mostly from renewable power sources like wind & solar,’ with ‘heat pumps and networks to replace gas boilers in homes and businesses’, cars and vans ‘fuelled by clean electricity & charging infrastructure to replace petrol stations’ and ‘industry running on electricity where possible, but, where it’s not, new infrastructure to supply clean hydrogen, or capture & transport the carbon emitted from burning fossil fuels to underground stores’.
Things have certainly moved on for renewables since MacKay’s study, but the NIC warns that there will be ‘costs as well as the benefits of transforming the UK’s infrastructure’. Although it says ‘making these investments will help lower costs for households and keep them lower in the longer term. These upfront investments will be paid for by consumers in their bills over the coming decades, not all at once.’
NIC rules out the use of electrolytic green hydrogen for home heating in preference for heat pumps, which it says are much more efficient, and although most commentators agree with that point now, not everyone agrees that all hydrogen for heating – along with the gas grid - should be ditched. Mike Foster, CEO of the Energy and Utilities Alliance, the body that represents most of the heating industry, reportedly said ‘it’s disappointing to see the NIC wedded to outdated thinking, but not a surprise as they have been saying the same thing for years’. He felt that we ‘will need a wide range of technologies to achieve net zero, heat pumps, heat networks and hydrogen boilers. That’s what current government policy states and that’s what we will work towards until told otherwise.’
UK gas company Cadent, which, amongst other things, is backing offshore wind to green hydrogen conversion, also insists that ‘both heat pumps and hydrogen are likely to play a key role in decarbonising heating in the UK’ and given that some have said there would not be sufficient wind capacity, they had taken ‘a fresh look at the data.’ Their conclusion is that ‘there could be enough wind capacity to decarbonise domestic heating using hydrogen. To supply every home currently connected to the gas network with green hydrogen for heating by 2050 would require 80 GW of offshore wind capacity, assuming the same level of energy consumption (which is a conservative estimate as properties should in future be better insulated). The overall efficiency of the process to convert electricity into hydrogen and then into heat generated is estimated at 66%,’ this being calculated by dividing heat demand by electricity output .
However, that’s just the start of their revision. They say that the 80 GW ‘would reduce further to around 40 GW by recognising that hydrogen will be only one of the long-term technologies for decarbonising heating and that many homes may choose to install heat pumps or other heating solutions. A pragmatic assumption would be to assume that half of the homes currently connected to the gas network are converted to hydrogen (and use the same amount of energy for heating). This aligns with the Climate Change Committee’s ‘headwinds’ scenario, where hydrogen demand for residential heat is 145 TWh/ year in 2050, around half of current annual residential natural gas demand’.
Well we will have to wait to if that can be accommodated. 40GW is certainly much less than was suggested as being needed in an earlier study of hydrogen heating. But even if desirable (opponents will say it will still waste green power), 40GW may not be possible in practice. The UK is likely to fall short of its target of meeting its 50GW offshore wind capacity target, potentially impacting progress towards net zero emissions, says Cornwall Insight, which suggests offshore wind capacity is expected to rise from 12.5GW in 2023-24 to 47.1GW in 2030, narrowly missing the government’s target.
Hopefully we will get back on track with offshore wind, and also on-shore wind, but, although few greens would be happy with the fossil gas-derived blue hydrogen option, however you read the cards in relation to green heating, or indeed green hydrogen use for vehicles and industry, it may be a bit early to start digging up the gas grid...
The energy world is changing fast, so it may not be surprising if some of MacKay’s conclusions may have turned out to be if not wrong then overstated. In his final interview, just before his untimely death from cancer in 2016, MacKay backed nuclear and said the ‘idea that renewable energy can power the UK is an appalling delusion’. It is wise to be cautious when looking at new technologies. However, it now seems he may have over-done it as far as some key renewables go. He did back heat pumps though....
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