The committee felt that 'a more incremental approach using alternative technologies (such as tidal lagoons) may have the potential to provide a lower-risk, lower-impact option than the Hafren Power barrage scheme', although they added 'whether these alternatives offer better value for money is far from clear at this stage'. An incremental 'step by step' approach would reduce the risks associated with going for a large barrage and allow for gradual learning. So they recommend that 'consideration is given to first developing a smaller scale tidal project, in order to build a stronger evidence base for assessing impacts, risks and costs before proceeding with any larger scale scheme'.

That is pretty much what consultants Black & Veatch and Parsons Brinckerhoff had told them in their evidence. Similarly the Renewable Energy Association had expressed concerns about the 'financial and environmental risks' of a large-scale barrage and advocated building a small barrage to begin with, 'to assess the costs and monitor the environmental impact'.

The Committee noted that the Regen SW and South West Marine Energy Park discussion paper, "Bristol Channel Energy - A Balanced Technology Approach", had claimed that a combination of tidal, wave and wind technologies could provide up to 14 GW of low-carbon electricity, obviating the need for a 'single mega-project which has major economic and environmental and impacts'. The paper also suggested that the focus on a single, 'potentially divisive' barrage project is damaging for the marine industry and instead recommends 'a more inclusive discussion'.

The alternative options certainly did look worth exploring. Tidal resource modeling by the Energy Technologies Institute suggested that 'the energy yield from a single large-scale Severn barrage could be achieved with a lower level of interaction and impacts through a combination of tidal energy extraction at a number of smaller, different sites.' By contrast, Engineering the Future told them that, with a single barrage, 'the timing of energy production would vary with the tides and the amount of power generated would vary significantly between spring and neap tides. Even though there are engineering possibilities to hold back and control water flow through impoundments, there would be some days every month when electricity was produced at times when ordinarily demand would be very low'.

On the economic case for the large barrage, the committee felt that 'attracting very large sums of money from long-term investors may prove challenging' and that, with DECC estimating levelised costs at £214-£353/MWh, the CfD strike price for the barrage 'would have to be considerably higher than the £100/MWh which Hafren Power have "in mind". Furthermore, the company say they would require this price to be guaranteed for 30 years, twice as long as an offshore wind project. [...] As a minimum, the strike price for barrage-generated electricity should not be higher than that for offshore wind, which is expected to be around £100/MWh by 2020 [...] If a higher strike price was offered, it would risk swamping the Levy Control Framework to the detriment of other low-carbon technologies'.

The Committee also noted that the environmental impacts of the current Hafren barrage plan were 'very considerable and that there is a high risk of unintended and possibly damaging consequences'. For example Hafren Power proposed to use a Very-Low-Head (VLH) turbine design deploying two sets of contra-rotating blades. Generation would be bi-directional on both the ebb and flood tides. The Committee noted that the Environment Agency had claims that it was 'not aware of any turbine designs which would allow the safe, repeated passage of fish through a barrage at the scale proposed.'

It noted Prof. Falconers estimates were that the scheme 'would reduce tidal range in the Severn from its current range of 0m to 14m to one of 3m to 12m. Low tide would therefore be raised by 3m, and high tide would be reduced by 2m. The overall reduction in tidal range would lead to a reduction in intertidal habitats of salt marsh and mudflats, with a resultant impact on bird populations dependent on these areas for feeding grounds.'

RSPB had suggested a barrage would have 'significant adverse effects on the populations of 30 species' with potential 'serious effects on a total of 96 European protected sites for birds'. The Countryside Council for Wales said that : 'Decreased flows and flow speeds incurred by a barrage would reduce the suspended sediment concentration within the impounded area and downstream leading to further changes in the estuary extent and composition of intertidal and subtidal habitat features of the Severn Estuary'

While Hafren Power cited the La Rance scheme as evidence of the potential for improved biodiversity with a barrage in place, the Committee was also told that La Rance was not an appropriate comparator for the Severn 'since it is "a rocky river valley" unlike the sediment-rich Severn estuary'. Problems experienced at the Annapolis Royal site in the Bay of Fundy had include 'fish mortality, erosion problems downstream and the health of the river upstream'. It was reported that tidal causeways across tributaries there had led to 'rapid, unpredictable consequences and no foreseeable return to a state of dynamic equilibrium.' RSPB pointed to experience in the Eastern Scheldt, where a storm surge barrier was built in the 1980s; the estuary still shows 'absolutely no sign of reaching a new equilibrium'.

By contrast the Committee noted that with lagoons the environmental impact was thought to be less since they would not affect tides and water flow to the same extent and would not obstruct downstream and upstream migration of fish. In addition 'Land-connected lagoons are located away from navigation channels, and therefore are unlikely to impact on the operations of Severnside ports. A lagoon design would be unlikely to impede the development of other marine technologies in the region.' They noted that the Regen SW and SW Marine Energy Park discussion paper suggested that a fixed barrage would 'impact on downstream flow and hence tidal stream generation potential'.

Hafren were clearly not happy and the door is still open for them to come back with an improved proposal, but overall it doesn't sound very promising or likely. Energy Secretary Ed Davey told the Lib Dem conference in Cardiff earlier this year that the government was 'looking for private-sector consortium to come with different projects in the Severn', but on the Hafren project he commented 'I think it's fair to say their numbers aren't in the place that they would need to be and there are some questions I know people have of that proposals yet to be fully answered.' By contrast, he said that there had been a 'huge amount of work' done independently on 'alternatives to a straight barrage, with lagoons and a more displaced, dispersed approach to getting that powerful tide and I think there are some real attractions to that. I am hoping that maybe if people can work through those economics, work through the ecological aspects which are critical, they can present government with proposals that are affordable and attractive'. www.walesonline.co.uk/news/wales-news/energy-secretary-questions-severn-barrage-2948639

Select Committee report: www.publications.parliament.uk/pa/cm201314/cmselect/cmenergy/194/19402.htm

However, as I indicated, there are concerns that, given a range of environmental, social and political issues, large hydro may not be the best option for the future, whereas smaller scale projects, including micro hydro, wind and PV solar, might be better suited to development goals and local needs. http://environmentalresearchweb.org/blog/2013/06/hydro--and-beyond.html

I focused on Africa, but the dominance of hydro is even greater in South America. Brazil, the leading economy in the region, already gets 87% of its electricity from renewables, mostly hydro. However it is trying to diversify, with wind and solar. So are some of the less developed countries in the region. Nearly 100% of Paraguay's electricity comes from hydro, but it is trying to expand other renewables, as are Patagonia, Bolivia and Ecuador, with PV especially favoured. Colombia, which currently gets 70% of its electricity from hydro, is investing in wind power: it has an estimated theoretical wind power potential of 21 GW.

It is the same story elsewhere. 82% of oil-rich Venezuela's electricity already comes from renewables, primarily hydro, but there are plans for expansion of wind power (with 10GW or more being said to be possible) and a 'sowing light' PV programme. Peru gets 56% of its electricity from hydro and is trying to build up its wind, solar and biomass contributions via a feed in tariff system. Argentina, which gets 40% of its electricity from hydro, is building a 1,350 MW wind farm with Chinese turbines, and is also pushing ahead with PV solar. In Chile, an election campaign promise by President Piñera was to get 20% of energy demand met from renewables by 2020. Uruguay plans to produce 90% of its electricity from renewables by 2015, 30% from wind, 45% hydro, and biomass 15%.

Moving north, Mexico, already has 2GWof wind capacity and is a looking to 12GW by 2020. There are also some interesting new wave and tidal projects emerging. It aims to get 35% of its electricity from non-fossil sources by 2026, up from 20% now. Nicaragua aims to be 94% renewables based by 2017, using hydro and some wind. In the Dominican Republic, a 2007 law established tax breaks for investment in renewables, which account for 14% of electrical generation. Cuba has been slower off the mark but there are many local off-grid PV projects, as well as hydro, wind and biomass resources, while solar and wind are obvious areas for development in the Caribbean region generally, with some projects underway or planned.

While funding remains an issue in much of Central America and the Caribbean, the solar and wind resources are large, as they are across the whole South American region. Large still hydro dominates but the use of wind is spreading, as is PV, although more slowly while the potential for using biomass, although controversial, is very large. But that's another story!

There is no question that the use of some types of biomass for energy is likely to be a poor choice. Some energy crops used for liquid biofuel production have very low calorific value, and mono-cultural plantations can be very bad for biodiversity, as well as requiring a lot of water and undermining local ecosystems. Rapid expansion of biofuels production in the developing world has led to problems such as deforestation and displacement of indigenous people. The need to meet rising biofuel targets has also led to exploitation of workers, loss of wildlife and higher food prices. It also contributed to poor harvests, commodity speculation and high oil prices, which raised the cost of fertilisers and transport.

However much of this is related to commercial pressures for production and export of high added value vehicle fuels- there have certainly been reports of poor working conditions in some biofuel plantations in Asia. Biofuels are the ultimate cash crop. But if we move away from high added-value products like biofuels for transport, the situation may get a little easier. Biomass can also be used for heat and power. Indeed many argue this make more sense, since the final energy yields/acre using solid woody biomass are generally higher than for liquid biofuel production.

In particular, there may be a role for some high yield energy non-food crops on marginal land, and for less invasive approaches, such as short rotation coppicing. Forests are different matter. It seems clear that deforestation and unsustainable exports should be avoided and that attention should be given to other less damaging approaches to biomass sourcing. Clearly though there is still much to debate, and some environmentalists see biomass and not too dissimilar from large hydro-something we should avoid. I will be looking at that debate some more in my next Blog.

For the moment, it maybe worth noting that the World Bank recently reversed a two-decade old decision to turn its back on large hydropower investment, which it now sees as crucial to meet the bank's key development goals, claiming that it has the highest potential for clean energy development and was abundant in the poorest regions of the world where the needs are greatest. It has pledged $1 billion in funding for hydro projects in relevant countries. Overall, it aims to place hydro higher on the political agenda, including large-scale projects, arguing that hydro at all scales was vital in affecting the impact of climate change.

This view is not shared by many environmental groups, who see large hydro as not only massively disruptive, in terms of local social and environmental impact, but also as unlikely to help with balanced sustainable development, with most of the power being sent long distances rather than being used locally, and methane emissions from biomass coming down stream and trapped by the dam making large hydro projects in some hot heavily vegetated areas worse in terms of greenhouse gas production than coal fired plants of the same generation capacity. Micro/mini hydro is preferred as less invasive and more localised. In addition to wind, PV solar is also seen as important for developing regions, including South America. See www.greentechmedia.com/research/report/solar-in-latin-america-the-caribbean-2013

Renewable Energy World has been running a useful series of reports on PV's prospects in the region www.renewableenergyworld.com/rea/news/article/2013/05/latin-america-report-the-future-of-solar-in-latin-america?cmpid=WNL-Friday-May31-2013

While it is true that in some locations hydropower, and the storage capacity associated with reservoirs, may be useful to help manage the variability of some these renewables, in the development context, there is a risk that large hydro projects will continue to dominate, squeezing out often more appropriate smaller scale options. For example, Brazil's 3,750 MW Jirau hydropower plant is the largest single renewable energy project so far being supported under the Kyoto Clean Development Mechanism.

Since the energy output is dependent fundamentally on the head height, sites which can accommodate taller dams can produce more energy and it is a square law: double the head gives you four times more energy on average. So in energy terms at least, the bigger the better, and trapping a large mass of water in the reservoir behind the dam will help to give a guaranteed supply, although there will be cost trade-off and site limitations.

The energy source is ultimately solar heat, which drives the hydrological cycle, but since that is climate and weather related, the energy resource at any particular location and time can vary. Indeed, with decreased rainfall in some areas in recent years, output from some hydro plants has fallen. This is likely to get worse with climate change.

The interactions between hydro projects and the environment are also two-way: large projects can have significant environmental impacts. Many environmental/development organisations, while backing smaller scale hydro, have opposed large hydro projects because of the large social and environmental impacts.

The social dislocation resulting from flooding areas for new reservoirs is an obvious issue, but there are also wider ecological issues. For example, the World Commission on Dams NGO has claimed that, in some hot climates, biomass carried down stream can be collected by the dam and can rot, generating methane, so that net greenhouse emissions can be more than from a fossil plant of the same energy capacity. It is not just a matter of any initial biomass trapped when the hydro reservoir was first filled, but a continuous ongoing process of fresh biomass decay http://www.dams.org/news_events/press357.htm,

The industry does not accept this. It says emissions are not a general problem, and in any case there are remedial options and there remains a strong push for more hydro, and large schemes. http//:www.sustainablehydropower.org

While it is clear that Africa and other places in the developing world need energy, there are counterviews about whether hydro, especially large hydro, is the best bet. Large projects are expensive and involve large companies who, some fear, may not be that concerned about local impacts. Certainly there have been some bitter battles fought over some projects and large-scale hydro remains a politically contentious issue in many parts of the world. Quite apart from local impact issues, it is sometimes argued that large centralised projects may in any case be the wrong answer for Africa and other similar locations. The very large distances involved make it unlikely that grids could ever cover the entire continent. As with the 40GW Grand Inga project on the Congo, much of the electricity seems likely to be exported on HVDC links to remote markets, not used locally. Local decentralised power may make more sense. That can be micro hydro, or wind, or biomass or solar, technologies which can be installed quickly with low local impacts and a potential for direct local involvement, and also possibly for the creation of local manufacturing enterprises to build the equipment.

Large hydro obviously plays a major role in Egypt, the Aswan Dam supplying 10% of its electricity, although it is now diversifying into solar and wind, with a target of getting 20% of its electricity from renewables by 2020. Large hydro is dominant in many sub-Saharan African countries, but in addition to wind, micro-hydro is seen as attractive in some locations, while village-level PV projects have spread widely, for example in Uganda, Tanzania, Chad, Rwanda, Angola, Gambia and Congo. Niger aims to get 10% of its primary energy from renewables by 2020, Senegal 15% by 2025. Kenya has large wind, solar and biomass resources, and is planning a 100 MW wave plant. It already has over 200 MW of geothermal capacity, and aims to meet 50% of its electricity needs with geothermal by 2018. Nigeria's 2006 Renewable Energy Master plan has renewables supplying 13% of electricity in the short term, and 36% long term. Ghana has introduced a Feed-In Tariff for PV, and its 155 MW PV project, launched in 2012, is the largest so far in Africa

Renewable energy feed-in tariffs (REFiTs) are clearly helping roll-out renewable technology across Africa, as they have in the EU, but a recent NGO report argued that, to meet Africa's needs at the speed and scale required without burdening the energy poor, costs must be distributed across the population fairly, based on usage and ability to pay, while the international community can provide extra financial support, such as through 'top-up' payments via a Global REFiT Fund, in line with obligations under the UNFCCC/Kyoto protocol for repayment of climate debts. http://www.foe.co.uk/resource/reports/poweringafricasummary.pdf

There has certainly been no shortage of high-level initiatives on renewables in the region. In 2009, the Africa-EU Energy Partnership and the EU, together with the African Union, launched a 10 year Renewable Energy Cooperation Programme. and the UN's new Sustainable Energy for All initiative, includes €50m EU backing. http://www.sustainableenergyforall.org/ But Africa needs more than top-down aid programmes. It needs local involvement, training and skill development, to support the growth of local jobs, and technical and economic capacities.

For a good overview see IRENA's new report on Renewables in Africa: http://www.irena.org/menu/index.aspx?mnu=Subcat&PriMenuID=36&CatID=141&SubcatID=276

In my next Blog, I will be looking at the situation in South America, where large hydro also dominates, but alternatives are also emerging.

The International Renewable Energy Agency (IRENA) see it somewhat differently. It looks to a doubling of the global share of renewable energy by 2030. It suggest that, if progress continues at the current pace, renewables will account for 21% of the global energy mix in 2030. See its Roadmap to 2030 http://irena.org/DocumentDownloads/Publications/IRENA%20REMAP%202030%20working%20paper.pdf

It has produced an open-access Global Atlas of renewable energy resources, covering wind and solar resource and local constraints world wide in a web accessible format http://www.irena.org/GlobalAtlas

IRENAs recent report on 'Renewable Power Generation Costs in 2012', claims that some renewables are competitive in some locations now and many more will soon be so. (Go www.irena.org under publications)

Moving things on, IRENA have released their first set of 10 briefs on various renewable energy technologies, covering bio-ethylene, bio-methanol, biomass co-firing, concentrating solar power (CSP), desalination using renewable energy, electricity storage, heat pumps, liquid biofuels, thermal storage and solar PV. Each brief looks at the technical background market status, potential and barriers. (Go to www.irena.org/ under publications)

In parallel a new International Energy Agency Renewable Energy Technology report explores current and potential bottlenecks in the global supply chains for wind and solar photovoltaic (PV), and recommends vital steps to avoid them. It argues that impact and the likelihood of occurrence of almost all of the bottlenecks identified can be reduced significantly, if not eliminated, by appropriate combinations of industry and policy measures. www.iea-retd.org/RE-SUPPLY

In addition, REN21 have produced a very timely review of renewables progress and prospects drawing on interviews with 170 energy experts around the world. It set the scene by reminding us that many past projections have be overtaken by reality: 'the International Energy Agency in 2000 projected 34 GW of wind power globally by 2010, while the actual level reached was 200 GW. The World Bank in 1996 projected 9 GW of wind power and 0.5 GW of solar PV in China by 2020, while the actual levels reached in 2011, nine years early, were 62 GW of wind power and 3 GW of solar PV'.

Looking forward, in the interviews, most industry experts believed that the world could reach at least 30-50% shares of renewables long term. And some advocated 100% or near-100% futures. European experts cited higher shares just for Europe, with many saying that Europe could attain 50-70% shares. www.ren21.net/gfr

Although the US and China are taking the lead overall, with renewables supplying around 15% of electricity in the US and 17% in China., the EU is also moving ahead quite well. The EU-27 renewables share of gross final energy consumption was 13.4% in 2011 against 12.5% in 2010 and employment in the sector rose to 1,186,000 in 2011, up 3% on 2010. www.eurobserv-er.org/pdf/press/year_2013/bilan/english.pdf

Wind has stayed in the lead. The EU wind energy sector installed 11.6GW of capacity in 2012, bringing the total wind power capacity to 105.6 GW, according to the 2012 annual statistics from the EWEA. For comparison wind is at over 62GW in China and around 60GW in the USA

In France, by the end of 2012, wind was supplying 10% of annual electricity, with 7GW in place so far. Italy has about the same. The UK also has about 7GW, increasingly offshore. And it is looking to have perhaps 16GW offshore by 2020. Belgium, is aiming for 2.2GW of offshore wind by 2020, and looking to 8GW eventually. Spain's 22GW of wind farms produced more electricity over three months last winter than any other power source, including over 6TWh of electricity during January, exceeding the output from both nuclear and coal-fired plants and supplying over 25% of Spain's total power generation. The leader however is Germany, which now has 30GW of wind capacity, and continues to make progress with, increasingly, offshore wind. For a summary: www.germany.info/Vertretung/usa/en/06ForeignPolicyState/02ForeignPolicy/05KeyPoints/ClimateEnergy__Key.html

PV solar is also doing well. The UK has 2GW, France 4GW, Spain 5 GW, Italy 15GW and Germany a massive 32GW, helping to push the global total past 100GW. And looking into the far future, Shells new 'Oceans' scenario says that by 2060 solar would be the largest single energy source globally. www.shell.com/global/future-energy/scenarios/new-lens-scenarios.html

For the moment though, wind leads the (non hydro) renewables. Overall, consultants Frost & Sullivan say that, within the EU, by 2020, wind is expected to generate 647 TWh, (up from 119TWh in 2010), hydro 392 TWh (up from 327TWh) others 408 TWh (up from 124TWh), while the output from EU nuclear power plants is expected to fall slightly, from 937 TWh to 910 TWh between 2010 and 2020. So nuclear's share of total EU generation will fall from 28.0% to 23.7%. and the use of coal for electricity generation will also fall, and quite dramatically, from 940TWh in 2010 to 517 TWh by 200. Looks to me that what they are saying is that renewables wiil see off coal and also nuclear, though perhaps not gas! http://www.frost.com

The EU approach seem to be popular. 70% of Europeans asked in a poll believed that investment in renewable energy should be prioritised over the next 30 years, compared to alternative energy sources including shale gas, nuclear and carbon capture and storage (CCS) plants. 28 % said energy efficiency measures should be prioritised, 18 % favoured nuclear and 12% backed CCS.

The survey of over 25,500 EU citizens carried out to inform the European Commission's comprehensive review of EU air policy, found that despite a campaign by industry to promote shale gas as a cost effective and lower carbon alternative to coal, just 9% of Europeans believe unconventional fossil fuels such as shale gas should be prioritised.

The results were fairly closely replicated across the EU but with some local variations .e.g. renewables were supported by over 80% in Portugal, Austria, Spain, German and Denmark, but in Bulgaria and Romania support was below 50% , while in Poland shale gas was backed by almost a third of respondents. www.ec.europa.eu/publicopinion/flash/fl360_en.pdf

What next? WWF have launched a report 'Putting the EU on Track for 100% Renewable Energy' which indicates where it thinks Europe needs to be by 2030 in order to reach a fully renewable energy system by 2050. It is comes as the European Commission is beginning to consider post-2020 climate and energy plans. WWF says that by 2030, the EU could reduce its energy use by 38% and generate 40% of the remainder from renewables. The post-2020 climate and energy policies needed to deliver this vision would it says help the EU to reduce its €573bn external fossil fuel bill and cut its greenhouse gas emissions in half. http://awsassets.panda.org/downloads/resreportfinal_1.pdf

While all technologies generate system costs, those of dispatchable generators are seen as at least an order of magnitude lower than those of variable renewables. The study says that ' the system costs of variable renewables at the level of the electricity grid increases the total costs of electricity supply by up to one-third, depending on country, technology and penetration levels'. While grid-level system costs for dispatchable technologies are claimed to be lower than $3/MWh, they can reach up to $ 40/MWh for onshore wind, up to $ 45/MWh for offshore wind and up to $ 80/MWh for solar.

Their UK data is as follows:

The back up cost is put at zero for nuclear, $4.05/MWh for wind at 10% market penetration, $6.92 at 30% penetration; $26.08 and $ 26.82 respectively for PV solar Balancing cost is put at $0.88 (@10%) and $ 0.53 (@30%) for nuclear; $7.63(@10%) and $14.15 (@30%) for both wind and solar

Grid connector costs are put at $2.23/MWh for nuclear, $3.96 for on land wind, $19.81 for offshore wind, $15.55 for PV.

Grid reinforcement and extension costs- zero for nuclear, $2.95/MWh ((@10%) and $5.20 (@30%) for on land wind, $2.57 (@10%) and $4.52 (@30%) for offshore wind, $8.62 (@10%) and $5.18 (@30%) for solar

Totals: Nuclear $3.10 /MWh (10%) $2.76 (30%) On land wind $18.60(10%) and $30.23 (30%) offshore wind $34.05 (10%) $45.39 (30%), PV solar 57.89 (10%) and 71.71 (30%)

So at 30% penetration, they say wind can cost at least ten times more, PV 20 times more than nuclear! Are they right? The nuclear costs look very low. In its 2010 study of the cost of maintaining adequate frequency response via the grid Balancing Services Incentive Scheme (BSUoS), National Grid estimated that 'the risk imposed by six additional 1800 MW [nuclear] power stations on the system could increase from £160m to £319m'. That works out at about $3.2 /MWh, assuming an 80% load factor. Not $0.53-0.88.

And some of the figures for renewables look very high. The extra cost for onshore wind backup and balancing services has been put by Milborrow at up to $4/MWh for contributions to supply of up to 20%, and up to £11.3/MWh for a 40% contribution. Not ~ $21 (at 30%)! In any case, the cost will depend on what measures are used to ensure balancing- output from gas plants is only one option e.g. interconnector links with the continent could lead to wider system benefits, exporting excess UK wind power. A big £bn p.a income gain. By contrast having nuclear on the grid imposes some costs. If it has to be run 24 7 then some output from renewables may have to be curtailed (i.e wasted) at low energy demand times. It is possible to vary the output from nuclear plants to some extent, but that too imposes operational losses and costs.

The NEA says that, currently, grid-level costs are absorbed by consumers through higher network charges and by the producers of dispatchable electricity in the form of reduced margins and lower load factors. It says 'Not accounting for system costs means adding implicit subsidies to already sizeable explicit subsidies for variable renewables. As long as this situation continues, dispatchable technologies will increasingly not be replaced as they reach the end of their operating lifetimes, thereby weakening security of supply.'

They add 'Maintaining high levels of security of electricity supply in decarbonising electricity systems with significant shares of variable renewables will require incentives to internalise system costs, as well as market designs that adequately remunerate all dispatchable power production, including low-carbon nuclear energy'

So it comes down to the simple message that renewables are a bad idea and if we persist in using them, then technologies like nuclear will need extra support and protection!

Of course you could argue that if you don't have nuclear then the problems are much less-it is not too much use for balancing after all, and there are plenty of good balancing options. The NEA however are unable to contemplate heresies like this. They simply say 'significant changes will be needed to generate the flexibility required for an economically viable coexistence of nuclear energy and renewables in increasingly decarbonised electricity systems'. Although actually they see co-existence as problematic 'In systems that currently use nuclear energy, the introduction of variable renewables is likely to lead to an increase in overall carbon emissions due to the use of higher carbon-emitting technologies as back-up.'

Really? Surely when wind is high, we wont be burning gas so, even if there are some emissions from gas plants run when wind is low, there will still be a large overall carbon saving. There is certainly a cost to providing backup, although it can clearly be exaggerated. Most of the backup plants needed for now and for a couple of decades ahead already exist, so it's just their occasional use of fuel that costs extra. Longer term we might need a few more, though that wont will be just for balancing- we may need them anyway to replace old plant. In a report to the Committee on Climate Change, in March 2011, consultants Poyry noted that, in a scenario with renewables supplying up to 94% of UK electricity by 2050, new peaking plant would not be needed until after 2030, and that by 2050 around 21GW would be needed. And, over time, we can switch to balancing with biogas and green gas generated from excess wind to avoid all fossil emissions.as was perused in the Pugwash report. www.britishpugwash.org/recent_pubs.htm

Developing radically new systems like, along with smart grids and supergrids, will certainly cost money, but will balance supply and demand, provide us with a way to switch to renewables, reduce the use of ever more costly fossil fuel and avoid the costs and risks of nuclear. Not something NEA would like! http://www.oecd-nea.org/press/2012/2012-08.html

However, these projects may well just stay as local energy suppliers, at least for a while. According to a report last year in European Energy Review (29/11/12), the success of Germany's Energiewende green energy programme has led some of Desertec's original supporters, like Greenpeace Germany and the German Greens, to conclude that Germany doesn't need Desertec. Even Germany's environment minister Peter Altmaier said recently that 'Desertec has become much less important since Germany's renewables boom.' The European Energy Review report concluded 'Germans may see Desertec as a welcome helping hand, they do not view it as a crucial part of their Energiewende'.

Siemens and Bosch pulled out of the Desertec programme last year, but Desertec remains confident given that it still has wide industrial support (including from E.ON and ABB) and it is still working with and supporting projects in North Africa, with CSP being only one of the options- there is also a huge wind potential in the region. There are also new potential project links elsewhere, for example in Asia. One such envisages HVDC supergrid links to wind projects in Mongolia, while, separately, the Gobitec initiative proposes links to CSP projects in the Gobi desert. http://www.gobitec.org/ and www.desertec.org/press/press-releases/1210 24-01-wind-power-from-the-gobi-desert/

Even more ambitiously, why stop at just generation? Although HVDC can be very efficient at shifting power long distances, there may be local excess generated at times, so why not store it until demand at the other end of the link is high? This could avoid grid congestion problems, which some see as becoming an issue, although initially more in the EU than at the source end of the grid: www.sciencedirect.com/science/article/pii/S0378779612003197

However, with large projects, local storage might be very valuable. There is the option of creating vast new lakes in depressions in desert areas for seawater storage and pumped storage operation using power from Concentrated Solar Power plants. The huge below-sea-level Qattara Depression in Libyia might be a possible site, or the Danakil Depression in Eritrea /Ethiopia. That's pretty speculative, but if an when CSP or CPV gets going on a significant scale, it might prove worthwhile: http://elpipes.blogspot.co.uk/2011/01/pumped-storage-at-danakil-depression-in.html

Perhaps a little less fanciful, there is a very large renewable energy potential in Northern Russia and Siberia, which might be exploited. Despite the huge wind potential, put at over 350GW, Russia has a very small renewable energy programme aiming to supply 4.5% of its electricity by 2020, with only around 11MW of wind capacity so far, and although it's now planning to expand that a bit, to 150MW, it is still clearly leaving most of it untouched. Instead it is focusing on exporting gas and developing nuclear power. But there have been suggestions that opportunities exist for exporting 'green' energy from Russia to the EU, which might help stimulate development of its huge renewables resource more rapidly.

A recent paper in Energy Policy argued that 'EU-Russian cooperation in the renewable energy field would present a win-win situation: (EU) Member States could achieve their targets on the basis of Russia's renewable energy potential, while Russia could begin to develop a national renewable energy industry without risking potential price increases for domestic consumers--a concern of great political sensitivity in Russia.'

Some of this might simply involve importing biomass from Russia, but there is also the option of electricity imports via new supergrid interconnections, although clearly there are huge political and economic issues involved. See 'RUSTEC: Greening Europe's energy supply by developing Russia's renewable energy potential', Anatole Boute, Patrick Willems, Energy Policy 51(2012) 618-629.

Long distance transfer using High Voltage Direct Current grids is quite efficient (with energy loses of around 2% /1000km compared to maybe 10%/1000km for conventional AC grids), butt there are plenty of problems with the supergrid idea, not least its high initial high capital cost. And for schemes like Desertec to work there will be need for careful local negotiation over way leaves and, for the local generation plants, over the distribution of costs and benefits: see http://www.spiegel.de/international/europe/competitors-and-local-opposition-threatens-desertec-solar-plan-a-892332.html. But the Desertec scheme only envisages most of the CSP power being used locally -only 15 % being sent to the EU, so local use would dominate.

Despite the problems, enthusiasm remains high. In a joint declaration last year the Desertec Industrial Initiative and Medgrid, the French led transmission group, along with lobby groups like Friends of the Supergrid, the Renewables Grid Initiative and the Climate Parliament group, said there could be 'No transition without transmission', and backed grid upgrade links across the EU and to and in nearby regions. See, www.medgrid-psm.com/en/

Political and economic pressures may slow them but supergrid projects of various kinds seem bound to spread as more renewables are added to networks. There are already plans for linking up wind projects in and across the north sea; given it huge renewables expansion programme, Germany need to reconfigure and strengthen its national grid system; enthusiasts in Japan are looking to supergrids to help top up and balance their new renewables programme; and China is building large HVDC links to integrate in its massive hydro and wind projects. And there is the ambitious Atlantic Wind Connection offshore grid proposed for off the east coast of the USA, linking up 7GW of offshore wind projects: http://atlanticwindconnection.com/

It may be developed piecemeal, and a long way from some of the wilder dreams about global supergrids, but the elements of regional supergrid systems look like they will emerge.

The report, "Conquering Challenges, Generating Growth", lays out the progress made so far: 12 full-scale single devices with a capacity of 9 megawatts deployed in UK waters generating clean electricity - more than the rest of the world combined. It notes that commercialisation of the tidal sector is just around the corner, with the deployment of the first arrays (multiple devices) beginning in 2014, and an expected increase to 100-200MW of wave and tidal installed by 2020. Major engineering firms such as Siemens and Alstom are working with the UK and Scottish Governments, universities and electricity companies to develop British marine power. The Crown Estate has awarded leases for more than 1.8 gigawatts of capacity at nearly 40 sites in UK waters. The British Isles has 50% of the total European wave energy resource and 25% of tidal energy resource - these technologies could generate up to 20% of the UK's electricity needs. Based on independent research, RenewableUK estimates that wave and tidal energy could be worth £6.1 bn to the UK by 2035, creating nearly 20,000 jobs - up from the 1000 employed now

However, this growth could be stifled if the Government fails to get the details of Electricity Market Reform right. The most crucial factor is the level of financial support technologies will receive. The report states that the initial strike price for the first generation of tidal arrays should be set at £280 to £300 per megawatt hour. For wave technology, the initial strike price should be £300 to £320/MWh. This will catalyse the marine energy industry, leading to economies of scale and learning through experience, which will lower the strike price for the second generation of arrays in 2018. Also, under EMR, contracts would only last for 15 years - the report argues that this must be extended to 20 years to give investors an adequate return - otherwise the strike price would have to be higher. It's notable that there is talk of EDF being offered 40 year CfD contracts for its nuclear projects.

RenewableUK's Wave and Tidal Manager, David Krohn, said: "The wave and tidal energy industry has reached an exciting period as it moves from single device demonstrator projects to the first small proving arrays. The world's leading projects are being developed in the UK waters thanks to a comprehensive package of support granted by the UK and Scottish governments, which has ensured that the UK leads the world in wave and tidal energy. However, there are significant hurdles that need to be overcome to ensure the sustained growth of the industry. It's time to get real about the potential risks so that we can work with Government and others to find the solutions as early as possible. Wave technology in particular will need tailored capital support in the coming years if we are to maintain pole position in this promising and strategically important sector. It is essential that Electricity Market Reform provides a level of support that will allow the most cost effective projects to be taken forward.' www.renewableuk.com/en/publications/index.cfm/wave-and-tidal-energy-in-the-uk-2013

It is true that wave and tidal stream technology is still relatively expensive, but costs are falling, thanks to the support via the revised Renewables Obligation and special development grants, amounting in all to 25-30p/KkWh. By contrast, onshore wind gets 10p/kWh or less and offshore wind 15-17p/kWh. Max Carcas, previously a device developer with Pelamis, told the Financial Times (28/1/13).'While 25-30p/kWh seems quite expensive it is often forgotten that there has never been a new energy technology that has been economic 'out of the box. The cost of generating from wind and solar energy has fallen by about 80 % since the mid-1980s, The fact that the opening costs of marine energy are lower than many preceding energy technologies puts this sector in a very good position to be competitive in the longer term.'

So it is good to hear that the Crown Estate is investing up to £20m in two new wave or tidal energy projects. The funding will be used to construct arrays (multiple devices). Projects with an installed capacity of at least 3 MW are eligible to apply, as long as they are expected to reach final decision on investment by March 2014. RenewableUK said: 'The funding will accelerate a crucial step forward - from successful individual devices to the deployment of full-scale arrays in the water. It will also help to attract the right level of private investment to commercialise the sector'

In parallel, two tidal power projects in north Wales and Scotland are to receive grants worth £10m each. Sea Generation Wales, a joint venture between Siemens, and RWE,, will develop a 10MW project off Anglesey, with five 2MW of MCT's SeaGen type generators, running by 2015, while MyGen, in a joint venture between Morgan Stanley and International Power, an independent power generation company, will develop an 86MW project in the Pentland Firth between the northern Scottish mainland and the Orkney Islands. This is the first phase of a 400MW array which will feature the turbines developed by Atlantis Resources and Tidal Generation Limited, the partly Rolls Royce initiated project now owned by Alstrom. More should follow. For example Siemens, is planning a MCT SeaGen project at Kyle Rhea in the Orkneys, expected to be operating tidal farms of 20MW to 50MW by 2020.

But it's not all good news. Neptune Renewable Energy's Proteus tidal stream ducted- vertical axis turbine has been found to be technically flawed and therefore not commercially viable. Their full-scale demonstrator was deployed in the Humber estuary in January 2012 and has been subject to much testing and a number of modifications. But it became apparent that the device would not be able to achieve a high enough level of electrical output, despite indications to the contrary resulting from earlier work done at fortieth and tenth scale. The plan was to supply the Deep marine attraction in Hull with around a third of its power.

The company said 'Since November, a significant amount of work has been carried out, some independently, to establish the reasons for the technical problems and to understand whether the company was facing issues of adjustment and tuning, rather than a challenge to the overall concept of using a vertical axis turbine within a duct, in estuarine locations. This work has included looking at an alternative lift turbine, rather than drag turbine," said the company'. But having looked at the options they have decided to abandon the project and liquidate the company. Source www.neptunerenewableenergy.com/

More positively, Pulse Tidal has secured a site for its 1.2MW commercial demonstration of its oscillating double hydrofoil system at the SW Marine Energy Park, Lynmouth. That's a very novel design, so it will be interesting to see how it fares.

It referred to a report by North Energy Associates (NEA) and Forestry Research (FR) produced for DECC, which tried to answer the question: 'Is it better to leave wood in the forest or harvest it for timber, other wood products (e.g. panel boards) and/or fuel?' They concluded that: 'Management of UK forests for wood production can contribute to UK carbon objectives e.g. to 2050...Using wood for bioenergy can also reduce carbon emissions, compared to burning fossil fuels for energy....These results suggest that policy should support managing UK forests to produce wood for products and bioenergy'.

However, the NEA/FR report specifically rejected the 'whole tree burning' scenario picked by the FoE/Greenpeace/RSPB report's researcher Tim Searchinger, in favour of using trimmings, offcuts and other wastes with no other market: www.gov.uk/government/uploads/system/uploads/attachment_data/file/48346/5133-carbon-impacts-of-using-biomanss-and-other-sectors.pdf

The Biomass Energy Centre, which is a government backed advice and information agency, has produced a critique of the Searchinger study, which it says 'appears to have been neither peer-reviewed nor submitted to any journal for formal publication, contains no new research but numerous factual errors and misinterpretation'. For example, he 'chooses just one scenario from the peer reviewed study by FR and NEA for DECC, amongst the hundreds examined,' allowing him 'to allege that biomass is "dirtier than coal", ignoring all the other scenarios that show carbon saving benefits in the form of lower GHG emissions ranging from marginal to very substantial'.

The Biomass Energy Centre says.'The DECC study shows that there are many ways of using forests and that, for managed forest in the UK, almost all of the scenarios provide considerably greater GHG emissions reductions than simply leaving the trees unharvested. It also shows that there is an unrealistic scenario, selectively picked by Searchinger, which is slightly less good under certain circumstances, in GHG emissions terms, than leaving them unharvested. This scenario does not make economic sense, and does not represent UK practice. In addition, the UK government sustainability requirements demand genuine GHG emissions reductions, so this scenario would not attract government support in the form of ROC payments and, hence, there is no incentive to power generators to use it'.

The Biomass Energy Centre point out that UK sawmill practice basically involves the selection and use of timber of sufficient size and quality for construction or joinery, purposes, and it backs this approach as being both economically and environmentally sound. The left overs have many uses including for paper, wood-based panels and sometimes for fuel. They insist that the use of whole trees including all of the roundwood for energy in the UK is simply not an economically realistic approach. What may be viable is the use of forestry thinnings, chips, sawdust, offcuts, etc. In addition, 'Broadleaf trees also have a significant proportion of branches (conifers typically much less), while conifer tops taper to wood of small diameter. If these types of wood are not used for wood-based panels (for which they are not always suitable), paper or energy, they will simply be disposed of, and will still break down to carbon dioxide. Consequently the appropriate use of these types of wood for energy, displacing fossil fuel, is beneficial.'

They note that 'the research undertaken by FR and NEA for DECC and related research by FR clearly demonstrates that the production of mixtures of sawn wood, wood-based panels, paper and fuel (including a proportion from small, young thinnings as whole trees) results in significant overall greenhouse gas benefits'.

Clearly, although they don't meet the re-absorption delay issue head on, they don't see using marginal and left over wood as a problem, and also claim that, even if biomass fuel prices rose, that would be unlikely to divert high value timber from other markets, so it would not be a problem for other uses of wood, including those which ensured continued carbon sequestration. www.biomassenergycentre.org.uk

One time Greenpeace and FoE senior energy campaigner, Stewart Boyle, now active in the biomass industry, also joined in the critique. He produced a heartfelt Blog for the Renewable Energy Association claiming that the NGOs had got it badly wrong. He also saw the co-firing of wood chips in coal plants like Drax as a helpful interim step and was worried about DECC's attitude. www.r-e-a.net/blog/modelling-our-way-to-biomass-paralysis-22-03-2013

Not everyone thinks that importing wood chips from North America to co-fire in large old inefficient coal plants like Drax is a good idea. The High Renewables scenario for 2050 produce for British Pugwash avoided all biomass imports: www.britishpugwash.org/recent_pubs.htm

But in the interim some might be condoned, while we get busy developing smaller scale high efficiency Combined Heat and Power plants, linked to district heating networks, and fed by UK sourced biomass or biogas. Short Rotation Coppice still has its advocates, while AD biogas production from farm and food wastes has a lot of attractions.

The latter would avoid land use conflicts, but if we want to go for green gas and biomass in a big way they may not be avoidable. The Pugwash 70% renewables scenario had 10% of UK land area being used for biomass by 2050, with the implication being that faming practices and diets might have to change. But 2050 is a long way off and by then we may well be generating (and storing) synthetic green gases, using the excess electricity that wind, wave and tidal projects will generate, when energy demand is low, to power electrolysers. Germany has started doing that now, in part as a way to balance variable renewables like wind and PV solar. But this 'power to gas 'idea also helps avoid excessive land use for biogas production, with an extension being to use CO2 captured from the air to convert electrolytic hydrogen into methane. See, for a UK input by ITM: http://www.itm-power.com/wp-content/uploads/2013/04/Platts-April13.pdf

Meanwhile, although burning trees is out of the question, we do need to see what biomass can offer. UKERCs estimate for SRC was 4% of UK electricity and that's just for starters. http://www.ukerc.ac.uk/support/tiki-index.php?page=Biomass+Resources+and+Uses

In theory a heat pump, working like a refrigerator in reverse, can deliver heat with around three times the energy value of the electricity fed in to run it, though in practice they may not always achieve these high levels of return, especially in cold damp weather (Roy et al, 2010). But heat pumps do offer a way of upgrading low-grade heat, from whatever source, including the air, ground, water, direct solar and geothermal, and if they are run using electricity from renewable energy sources, their carbon emissions will be low.

Steam-raising thermal power plants by contrast are much less efficient. However they can be operated in Combined Heat and Power (CHP) mode, so that some of the heat that would otherwise be wasted in the conversion process is captured for use in district heating networks (DH). CHP/co-generation can increase the energy conversion efficiency up to 80% or more, compared with around the 35% typical of conventional stream raising plants, and so it makes a lot of sense, as long as there is a suitable local heat load e.g. a city or urban area. It has been claimed that CHP plans linked to district networks are far more efficient than heat pumps, especially small domestic scale heat pumps.

Heat pumps have an energy output/input Coefficient of Performance (COP) of maybe 3, but since they are using some of the heat that would otherwise be wasted, CHP plants linked to DH can deliver a COP equivalent of up to 9, or more, depending on the grade of heat that is required (Lowe 2011). And if CHP plants use a renewable source of heat, like geothermal or biomass, their carbon emissions, already low/kWh, should be even lower, and cost less/tonne of CO2 saved than heat pumps (Kelly and Pollitt 2009). Though, there is some debate on this; it may depend on the carbon content of the electricity used by the heat pump and the grade of heat that you want out (Woods 2011; MacKay 2013).

It is true that installing district heating (DH) mains can be disruptive, more so than installing heat pumps in individual houses. But once installed and linked to the central heating radiators of houses and other buildings, unlike with domestic heat pumps, there is no in-house device to maintain. Moreover, once installed DH pipes can be fed with heat from any source, as they become available, including solar and geothermal energy and it become a major infrastructure asset. That helps make large scale solar heating linked to heat stirs viable in Denmark- it's claimed to be much more economic than individual house solar heating, if you already have the DH network.

Note also that heat can actually be sent quite long distance without significant losses: for example Oslo's district heating network is fed via a 12.3 km pipe from a waste burning plant in the city outskirts, and in Denmark there's a 17km link from a CHP plant to the city of Aarhus, while heat is delivered by a 200 MW capacity heat main to Prague from a power station 65 km away.

With a CHP/DH system at Odense claimed to have a COP equivalent of near 12, three times that of a heat pump, surely CHP/DH wins hands down? Well no, sadly it's more complex than that. These systems are not operating in a vacuum. If there is a lot of spare electricity available at night (e.g. from a large nuclear and/or wind programme) then heat pumps can use it, and in off- gas grid areas, which are also to be unlikely to be candidates for DH, domestic heat pumps can be very useful .

It has also been pointed argued that, while CHP may convert 1 unit of combustible fuel into, typically, 0.5 units of heat and 0.3 units of electricity, and so is overall 80% efficient, a heat pump converts 1 unit of electricity into ~2 or more units of heat, so its 200% efficient. Ah, but where did the electricity come from? If it's from a fossil or nuclear plant running at 35% efficiency, you are back down to 70%. And retaliating further, the CHP buffs say that, in theory since CHP delivers heat that would otherwise be wasted, its COP is infinite- since it gives us heat for no new fuel input!

It certainly can get complicated. For CHP operation, taking heat out from the near final stages of a power turbine reduces its electrical generating efficiency slightly, but to confuse things further, stream is sometimes taken off at several stages at different temperatures- and times. So there is no one efficiency figure: CHP plants can vary the heat to power ratio depending on market and weather conditions. And of course you can use heat pumps with heat from CHP! And big heat pumps can be good in some locations, taking heat from rivers, lakes or even the sea, as is done in Sweden. The debate goes on...

References

Kelly, S. and Pollitt, M ((2009) 'Making Combined Heat and Power District Heating (CHPDH) networks in the United Kingdom economically viable: a comparative approach' Energy Policy Research Group, Cambridge University: EPRG Working Paper 0925: www.eprg.group.cam.ac.uk/wp-content/uploads/2009/11/eprg09251.pdf

Lowe, R (2011) 'Combined heat and power considered as a virtual steam cycle heat pump', Energy Policy Volume 39, Issue 9, pp 5528-34 http://dx.doi.org/10.1016/j.enpol.2011.05.007

MacKay, D (2013) 'Sustainable Energy without the Hot Air'- on line book, p147 et passim http://www.withouthotair.com/

Roy, R., Caird, S. and Potter. S (2010). 'Getting warmer: a field trial of heat pumps', The Energy Saving Trust, London.

Woods, P and Zdaniuk, G (2011) 'CHP and District Heating - how efficient are these technologies?' CIBSE Technical Symposium, DeMontfort University, Leicester UK 6/7th September