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Renew your energy: September 2010 Archives

Solar farming

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Solar farms seem to be catching on with farmers - stimulated by the Feed-In Tariff which offers a good income if you have the money to invest and space for large PV arrays. Madeleine Lewis of Farming Futures, a body backed by the Department for Environment, Food and Rural Affairs (Defra), the NFU and Forum for the Future, the environmental group, told the Daily Telegraph (14/8/10): "A year ago, farmers thought of solar as not very profitable and that's obviously changed. They are now very keen to invest in renewables. They are using a lot of energy, prices are going up and that has hit their businesses hard. Renewables projects insulate them against rising prices and provide a new income. There's a lot of buzz around it."

According to the Telegraph's report, nearly 40 farmers in Cornwall 'have already inquired about planning permission for solar projects in the county and more are likely to follow. Installations are also being planned in Herefordshire, Somerset and even the North East of England, despite there being 20% less sun than in England's south-western foot.'

It noted that Michael Eavis, the high-profile farmer and host of the Glastonbury music festival, is installing a £550,000 project using 1,100 panels on the roof of his cow barn. It will be the biggest solar roof in the country. In Herefordshire, a group of eight farmers is clubbing together through advisory company 7Y Energy, owned by 450 farmers, to buy solar panels for their barn roofs. Another group of 35 are undergoing surveys to see if their sites are suitable.

The Telegraph noted that one of the most ambitious investors in solar energy in the UK is MO3 Power, which is already engaged with 15 farmers and wants to have 100 sites generating 500 MW of energy within five years. A typical site would it says cover 13–15 hectares, generating 5 MW with the potential to give an annual income of £50,000 a year for farmers leasing their land for the solar farm.

And as I noted in an earlier blog, Ecotricity also has plans for solar farms – 500 MW in the SW. And it has recently also submitted a proposal for a 1 MW 'sun farm' at Fen Farm, Conisholme, near Grimsby, on land next to a 20-turbine wind farm. It would consist of 59 rows of south-facing solar panels on a 4.7 acre site. It's also applied for permission to install five more wind turbines and sees the project 'one of the first combined wind and sun energy parks in the world'.

However the first to go ahead seem likely to be a 5,000 panel project developed by 35 Degrees, occupying 7.3 acres of Wheal Jane, a Cornish tin mine, abandoned in 1992. It's expected to generate 1.34 million kWh each year. It has evidently just got approval from Cornwall Council planners. Cornwall Council has estimated that solar power developments could bring up to £1 bn in investment. Lucy Hunt, a manager at Cornwall Development, commented: 'We're seeing the start of a Cornwall solar gold rush as developers need to have built their farms, with full planning consent, by April 2012 to take full advantage of the Government scheme.'

35 Degrees says that it plans to install 100 MW of solar farms in due course.

Another project, Benbole farm in St Kew in Cornwall, is also well advanced. It has applied for planning permission for a 2 MW array in a seven-acre field. It's being backed by Penzance-based renewables specialist Renewable Energy Cooperative (R-ECO), along with the commercial arm of the University of Exeter, in a consortium of local companies calling itself "Silicon Vineyards", which has a wider £40 m programme aiming for 20 MW of capacity with 10 solar farms.


The NFU evidently believes that as many as 100 farmers will be setting up major solar projects by next year with many more already planning small-scale developments. The NFU is encouraging farmers to mount PV panels on barn roofs or to use land around the edge of fields for solar panels rather than using fertile agricultural land for so-called 'solar vineyards'. Dr Jonathan Scurlock, the NFU's chief adviser on renewable energy, told the Telegraph that farmers could graze chickens, geese or even sheep underneath field-based panels to maintain agricultural use.

The Campaign to Protect Rural England, which has opposed the construction of many wind farms, said it would prefer that 'car parks and factory roofs' were considered first when siting these sorts of projects. However, R-ECO says that it is 'very carefully selecting sites that will not impact the local environment, either visually or through impacting on natural ecosystems. As a co-operative business, we understand and respect the importance of maintaining natural beauty of our environment and we are working diligently to ensure that our farms visual impact will be mitigated through bush and tree plantation which in turn will act to offset the carbon footprint caused by our developments.'

Commenting on Benbole Energy Farm, R-ECO told the Guardian (18/5/10) that 'the visual interference will be negligible. It's very low to the ground and the surface of the panels are matt rather than reflective. No planning concerns have been raised by the local planning authority after initial inspections.' It added 'the array will be hidden from view behind willow coppice or by traditionally built Cornish hedge rows by our in-house Cornish Hedger'.

R-ECO says that around 10% of the income from the scheme will be set aside for a community fund, and they also keen to support local community-owned solar farms. It says it is 'going to open up the doors to PV farms to everyone by developing solar farms paid for by communities and individuals. This will allow anyone and everyone to benefit from the financial rewards of solar PV even if they do not own their own home, do not have a south-facing garden, live in a flat/apartment and do not have the thousands of pounds to invest in their own system.'

It adds: 'Our community solar farms will allow anyone to invest any sum of money and get the lucrative financial rewards for doing so as well as be satisfied that their investment has gone towards bettering the environment and improved fuel security.'

Biochar reviewed

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'Contemporary interest in biochar is, first and foremost, driven by its potential role as a response to the problem of climate change, through the long-term storage of carbon in soils in a stable form.' With that preamble in mind, and noting that it could also reduced the use of fertilisers, the Biochar Research Group at Edinburgh University was commissioned by DEFRA to review the potential of biochar. and in particular to look at some major uncertainties surrounding its impacts upon soils and crops, its overall performance and its costs compared to other carbon mitigation options. As the preamble put it 'whilst biochar might improve productivity, is this effect really understood well enough that we can factor-in a long-term enhancement of the carbon sink in vegetation and soils?'

As I indicated in an earlier blog, there were also uncertainties as to whether it would be as effective in terms of carbon dioxide gas abatement as other ways of using biomass, including use simply as a carbon-neutral fuel, offsetting fossil-fuel emissions. There were also concerns that if it did prove effective, the result might be vast biomass plantation undermining biodiversity and competing with food production.

The final report on Pyrolysis-Biochar Systems ('PBS') from the project has now emerged. It says that it provides 'preliminary evidence that PBS are an efficient way to abate carbon, and tend to out-compete alternative ways of using the same biomass (in terms of carbon abated per tonne of feedstock, or in terms of abatement per hectare of land).' It suggests that you can get abatement of 1.0–1.4 t CO2eq per oven dry tonne feedstock used in slow pyrolysis. 'Expressed in terms of delivered energy PBS abates 1.5-2.0 kg of CO2eq/ kWh, which compares with average carbon emission factor (CEF) of 0.5 kgCO2eq/ kWh for the national electricity grid in 2008, and current CEF for many biomass feedstocks of 0.05–0.30 kgCO2eq/kWh. Expressed in terms of land-use, PBS might abate approximately 7–30 t CO2eq/ha/yr using dedicated feedstocks compared with typical biofuel abatement of between 1–7 t CO2eq /ha/yr.'

And so it concludes, provided the Carbon Stability Factor (the proportion of total carbon in freshly produced biochar, that remains fixed as recalcitrant carbon over a defined time period), remains above 0.45, 'PBS will out-perform direct combustion of biomass at 33% efficiency in terms of carbon abatement, even if there is no beneficial indirect impact of biochar on soil greenhouse-gas (GHG) fluxes, or accumulation of carbon in soil organic matter'. But it says there is also 'an, in principle, credible case that biochar deployment in UK soil will produce agronomic gains (and possibly suppress GHG emissions)' so it's doubly blessed, though, perhaps inevitably, the report says that more research is needed to be sure.

There are also some other caveats (e.g. on costs, which it puts at maybe £42/t CO2). It says that: 'Biochar is, currently, an expensive way of abating carbon, although the costs would likely come down with investment'. It notes that: 'There has been relatively little attention to the logistics of PBS, even though this is likely to be very important to the economic and practical viability. The issues raised include the need for (and cost of) storage, the acceptability of truck movements, and how economies of scale in producing and distributing biochar might be achieved. Biochar is currently expensive to produce due to feedstock, capital and operational costs. Extensive PBS implies an extensive infrastructure, involving pyrolysis units probably at a range of scales that will take some time to be built and operated, especially given the current lack of dominant design.'

Nevertheless it says 'Biochar could, however, increase quite significantly the opportunities for carbon abatement in the agriculture and land-use sectors. In the UK the availability of land is unlikely to present an absolute barrier to biochar deployment, although the land potentially providing the highest returns from biochar addition (such as horticulture) is relatively small in extent. The supply and cost of biochar also depends upon the extent to which organic waste feedstocks could be utilised. There are some 'niche' areas where PBS could have particular advantages over alternative ways of dealing with organic residues, even within current economic conditions.'

The Centre for Alternative Technology came to similar conclusions in its 'Zero Carbon Britain 2030' study: see my earlier blog. They saw biochar playing a key role.

Although the Edinburgh study does highlight some potential problems and unknowns (e.g. on cost and how long carbon will stay trapped), it calls for more pilot projects and it does look like biochar, if sensibly managed, could be a winner. However, somewhat oddly, DECCs new '2050 Pathways' report only sees biochar as playing a fairly limited role, as one possible geo-sequestration option – perhaps trapping 1Mt CO2 p.a. in the UK by 2050.

By contrast a US study, 'Sustainable biochar to mitigate global climate change' is very positive. Biochar could it says offset 1.8 bn tonnes of carbon emissions annually, in its most successful scenario – around 12% of current global greenhouse-gas emissions – without endangering food security, habitat or soil conservation.

The DEFRA/Edinburgh Biochar report is at:

Wind power enthusiasts sometimes point to Denmark as a good example of what can be done- claiming that it gets around 20% of its electricity from wind. Wind opponents also sometimes point to Denmark, claiming that in fact not much of this is actually used in Denmark since it's often available at the wrong time, when demand is low, and so has to be exported. Worse still, Denmark has to import power (mainly from hydro) from Norway and Sweden, to back up it's wind plants when they can't deliver enough and demand is high. This costs them more than they get from their exported wind. So wind is a net financial loss, and a drain on the Danish economy. A debate on this issue has been raging on the Claverton Energy Group website and e-conference over the past year.

Some say it's all because Denmark has a small, inflexible energy system. It's been pointed out that a major effort was made in Denmark to move away from oil over to coal. Much of the coal capacity consists of large centralised Combined Heat and Power (CHP) plants, which although more efficient that conventional electricity plants, can't easily be used to balance the variable wind output. Worse still, heat is often needed when there is no major demand for electricity. In these circumstances some CHP electricity has had to be exported, along with any excess from wind. Unfortunately this will be when there is likely to be a surplus of wind power in the surrounding countries, so the price which is offered is quite low.

Against that, these exports will be reducing the amount of fossil fuel which is used in places like Germany. In Norway and Sweden though this electricity may sometimes only be replacing (zero carbon) hydro, but that depends on the timing – if their hydro reservoirs are low, it can be used to pump them up, in effect storing wind power and excess CHP power for later use. On this view all is well in climate terms, though it does cost the Danes more: what's really needed is a pan-EU balancing system, with perhaps a Cross Feed tariff to ensure that using stored power in not prohibitively expensive. More flexible generation/load management in Denmark would be good too. Along with better interconnections- and an economically synchronised market system covering all the participating and connected countries (e.g. the Baltic states and Germany). Certainly, some say that Denmark is too small to be treated as a coherent energy system, but others say that being small is actually a great advantage for them, it means that wind can be backed-up (via interconnectors) by larger grid neighbours – something that would be much more difficult in UK's case.

Lessons for the UK

Some argue though that, being larger with a range of flexible back up plants, the UK could in fact do much better than Denmark – although they accept that it must strengthen its grid and interconnections. But even without much of that, there should be no need for extra backup for some while: you could add 30 GW wind and use existing UK fossil plants as back up – you don't need to build 30 GW of new plant and therefore "pay twice", as some anti-wind people claim. We already have it – and have paid for it. And some of it is already used as back-up – for conventional and nuclear plants, and to deal with the daily demand peaks. On this view, basically, when available, what wind power does is replace some output from the existing power system – so you don't need to build any extra back-up for when wind is not available.

Although the probability of zero wind output is relatively low, as things stand at present, we would have to retain all, or most of, the existing system – wind has a low capacity credit, perhaps 15% depending on the total capacity. However, more existing capacity could be retired if we had a more flexible system, with more load management, more storage and more interconnections, plus inputs from firm non variable renewables like biomass and geothermal, though the optimal mix is as yet undetermined. There is also the problem that operating fossil plants occasionally at lower power means they are run inefficiently, part loaded, which adds to costs. But they may not have to run often and the cost penalties will therefore be low. Inputs from other renewables could also help (e.g. although they are variable/cyclic, wave and tidal availabilities are phased differently from wind). Inflexible nuclear however just gets in the way. At least Denmark doesn't have that problem!

You can join the debate at

Energy from the air

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Rather than seeing excess carbon dioxide in the atmosphere as a problem to be dealt with, by, for example, expensive carbon capture and underground storage, why not make use of it to produce fuel? The basic chemistry is simple, assuming you have some spare hydrogen: CO2 + H2 = CO + H20. The CO can then being converted to hydrocarbon fuel, for example by via the Fischer–Tropsch process. That of course needs more hydrogen. Fortunately, not only do we have plentiful supplies of CO2 from the air, air movements can also supply the energy, via wind turbines, to make hydrogen, via the electrolysis of water. Problem solved! Except of course each stage in this process is difficult, with conversion efficiency's of around 60%, unless the waste heat can be recycled/used.

Carbon capture techniques are of course being developed for use with power stations emissions. But there has been a parallel idea of 'air capture' – for example the 'absorption tower' approach developed by Prof. David Keith from Calgary University, in which a fine mist of strong sodium hydroxide solution is brought into contact with an air flow. The big advantage of that is that you can do it anywhere – not just at power plants. But rather than just storing the resultant mix, the CO2 can be recovered, ready for conversion into a fuel.

That is what a team led by Prof. Tony Marmont are planning to do, using an electrochemical process based on a patented design developed by Prof. Dereck Pletcher, formally of Southampton University.

Prof. Marmont is a long time proponent of renewable energy in the UK and funded the set-up of the CREST organisation at Loughborough University. His team at Beacon Energy in Leicestershire has been working on hydrogen generation, storage and use for some while – with the electricity supplied by their own wind and PV systems, so the next stage should be a bit easier.

In the 'air fuel synthesis' (AFS) approach being developed by Marmont, the recovered carbon dioxide will then be reacted with electrolytic hydrogen; either directly to make methanol and thence to petrol via the Mobil Methanol-to-Gasoline route; or via the Reverse Water Gas Shift reaction (as above) with hydrogen, to make carbon monoxide, which in turn will be reacted with more hydrogen in a Fischer–Tropsch reaction to make hydrocarbons. In the latter case, variation of the reaction conditions could enable petrol, diesel or aviation fuel to be made.

It's a fascinating idea, essentially using renewable energy to do what nature does with photosynthesis – convert atmospheric carbon dioxide back into organic molecules. But it does rely on multiple stages, each with significant energy losses. In terms of road transport applications, you would presumably get a much better return on the wind-generated energy if it was just used in battery electric cars – with the overall conversion efficiency then being 90% or so. So the AFS approach may only be an interim option while electric cars are improved. But liquid fuels have a much higher utility/energy storage density than batteries, and there may well be some application (e.g. for heavy goods vehicles and, crucially, for aircraft) where liquid fuels will have major advantages.

So there could well be a future for ideas like this, and the wind power resource could be up to it in time. The Marmont team calculate that 'to make all UK oil – 140,000 tons a day – as synthetic, would take a windfarm area 175 miles by 175 miles in the North Sea. To make only aviation, marine and military fuel as synthetic, would take an area 72 miles by 72 miles.'

The Los Alamos Lab in the US has proposed something similar, but with the energy supplied by a nuclear reactor. They gave their idea the somewhat cringeworthy label 'Green Freedom'.

For good measure they suggested that conventional power station cooling towers could be used for the carbon dioxide trapping NaOH spay system. But as with the wind-AFS approach, it would probably be more efficient to use the nuclear electricity directly in electric cars, a point made elegantly at

Nevertheless, with there being no easy aviation fuel substitutes, Air Fuel Synthesis does still seem worth exploring, as are the various other novel 'Green Chemistry' ideas for fuel production being developed around the UK and elsewhere, including the use of biomass as a feed stock for hydrogen production. See for example:

For more on new renewable-energy developments, visit from which some of the above was drawn. Thanks to Dave Benton for his input on AFS.

How much carbon dioxide is produced from nuclear generation? Certainly the power plants do not generate carbon dioxide directly. But there are indirect carbon implications – including from uranium mining and fuel fabrication, which arevery energy intensive activities.

In a 2001 study, Jan-Willem Storm van Leeuwen and Philip Smith commented that: 'The use of nuclear power causes, at the end of the road and under the most favourable conditions, approximately one-third as much CO2-emission as gas-fired electricity production. The rich uranium ores required to achieve this reduction are, however, so limited that if the entire present world electricity demand were to be provided by nuclear power, these ores would be exhausted within three years. Use of the remaining poorer ores in nuclear reactors would produce more CO2 emission than burning fossil fuels directly'. They developed this analysis is subsequent studies:

This analysis was strongly challenged by the World Nuclear Association which disputed some of the figures and assumptions and the nuclear industry has also pointed to the use of in situ leaching techniques that are claimed to reduce the energy costs of uranium ore extraction.

However this claim, and the WNA figures, as well as the estimates by Smith/Leeuwen, have been challenged by Prof. Danny Harvey. In a new textbook on Carbon Free Energy (Earthscan), he estimates the 'energy return over energy invested' (EROEI) ratio for nuclear power production as being 19.5 for uranium ore grades of 1%, down to 17–19 for the current world average grade of 0.2–0.3%. For an ore grade of 0.01%, the EROEI ratio drops to 5.6 for underground mining and to 3.2% for open pit mining, but could be as low as 2 or as high as 10 for in situ leaching ('ISL') techniques. However he suggests that ISL involves 'significant and irreversible chemical and radioactive contamination of underground aquifers.' And of the 5.4 million tonnes of identified uranium resources, he says only 0.6 mT are amenable to ISL.

Although there can be debates about assumptions and methodology, the basic issue seems clear: as lower and lower grades of uranium ore have to be used, increasing amounts of energy are needed to make the fuel, so that, since the bulk of this energy will for the present come from fossil-fueled plants, the emissions they produce will undermine the advantage of the zero-emission nuclear plants, and ultimately could make the whole exercise pointless – you would be producing more CO2 than if you just used the electricity from the fossil-fueled plants directly as normal.

The assessment of when the so called 'point of futility' is reached, when the energy used (and carbon produced), to mine and process the fuel is more than the carbon-free energy produced by the reactor, depends on a variety of complex factors, including the energy efficiency of the fuel fabrication and enrichment processes, and how this energy is provided. Centrifuge methods are much less energy intensive than the diffusion processes so far mostly used for enrichment, but it's hard to see how improvements in fabrication efficiency could continually compensate when lower and lower quality ores have to be used. The high-grade ores currently used contain around 2% of uranium (20,000 parts per million), the lower grade ores only 0.1% (1000ppm). Granite contains just 4ppm and seawater – 0.0003 ppm. If we had unlimited cheap carbon free energy, then maybe we could extract some of this, but then we wouldn't need to!

Other analysts have focused on the energy balance issue- and compared nuclear with other options. A study by Gagnon from Hydro Quebec looking at energy outputs to energy inputs ('energy payback ratios') over the complete life cycle, indicated that, at present, nuclear plants (PWRs) only generate up to 14–16 times as much energy as is required to build them and produce their fuel. By comparison, on-land wind turbines could produce up to 34 times as much energy as in needed for their construction (they of course don't need any fuel for operation). Moreover, this figure is likely to be improved as new technologies emerge (an earlier paper by Gagnon had wind ranging up to 79), while as we have seen, the figure for nuclear is likely to fall as lower grade ores have to be used. (Gagnon. L Civilisation and energy payback Energy Policy 36 2008, 3317–3322).

The study of energy balances by Harvey mentioned earlier came to similar conclusions: while as we have seen he claimed that the energy returns over energy invested (EROEI) ratio for nuclear was below 20 and possibly as low as 2, he found that the EROEI ratios for most major renewables were much better than this, even for nuclear using current grades of uranium, and 'will be decidedly better at lower grades'. Solar PV, which is one of the more energy intensive renewables, had a EROEI ratio of 10–20 at present and this is expected to rise to over 20 given new technical developments. While the EROEI ratio for wind was, he calculated, already up to 50.

Perhaps the last word should go to Benjamin Sovacool from the National University of Singapore, who has produced a paper trying to resolve the differences in views on this issue. It assessed 103 life-cycle studies of the nuclear fuel cycle. He says that the quality of most life-cycle estimates is very poor, with a majority obscuring their assumptions (sometimes intentionally) and relying on poor and/or non-transparent data; but when one selects only the most methodologically rigorous studies, typical life-cycle emissions from nuclear plants appear to be about 66 g CO2e/kWh. Although that is less than the estimate of 112–166 g CO2/kWh produced by Storm van Leeuwen and Smith, it is more than most renewables and 10 times greater than the industry often claim for nuclear power – he says they typically put the life-cycle emissions from nuclear plants, including ancillary fuel fabrication and (in some studies) waste disposal, at 1–3 grams of CO2e/kWh.

Sovacool. B Valuing the greenhouse gas emissions from nuclear power: A critical survey, Energy Policy 36, 2008 pp2940–2953.

All of this may not matter if we are just talking about a few extra nuclear plants, but if larger programmes are envisaged here and elsewhere, then it begins to be important. Certainly if we are thinking in terms of very major UK expansion along the lines of the 146 GW by 2050 seen as possible, if very ambitious, in the new DECC 2050 Pathways report, or even perhaps in the case of the UK 'nuclear renaissance' programme envisaged by Robin Grimes and Bill Nuttall in their recent Science review paper ( and by the IMEch in their recent report, which seemed to back the earlier suggestion by the Malcolm Wicks MP, that nuclear should provide 35–40% of UK electricity 'beyond 2030':