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I have just finished writing a new book entitled 'Renewables', which should be out later this year. It looks at the state of play around the world, drawing in part on this Blog. There is a lot of technological progress to report, and lot of inspiring plans. Some renewables are already competitive with conventional sources in some locations, and many more may well be soon. The down side is that, despite good progress, globally the climate policy picture is still grim. The use of coal is expanding, undermining emission reductions. In the absence of tight, globally agreed, emissions targets, market trading arrangements like the EU Emission Trading System are not very effective. Indeed the EU-ETS seems to be near collapse, with carbon credits trading at 2.6 euro/tonne.

Fortunately the feed in tariff approach seems to be spreading, and that is much more effective, as I report in my new book. Soon we should have 300GW of wind in use globally and we have just passed 100 GW of PV solar, with FiTs helping a lot. The retreat from nuclear in some countries is also helping, although the nuclear v renewables issue continues to rumble on, and I have covered it briefly in the new book. The simple point is that most renewables are getting cheaper, moving down their learning curves well, while nuclear is displaying a negative leaning curve,with costs rising. In parallel, the Energy Return on Energy invested (EROEI) ratio for nuclear is low (around 15:1) and is likely to fall as uranium ore grades decline (maybe to 5:1 or less) while the EROEI's for renewables are all higher and improving (pv solar up to 20:1, CSP 40:1, wind up to 80:1,hydro 200:1 or more).

Renewables do have their problems (e.g they are mostly diffuse and variable) and much of the new book looks at how they might be overcome. It covers grid integration issues, supergrid links, and so on. I hope I have managed to get the balance right, being realistic about what can be done, while still conveying a positive message.

I will be interested in reactions.

(A short blog this week, as I'm on holiday in Spain)

A lot new under the sun

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Solar energy continues to develop as new ideas emerge. There is over 70GW of solar PV now installed around the world and new cheaper cell technologies are emerging, such as die sensitized cells:

Longer term, other novel options are also on the horizon. For example, researchers at Stanford University have developed a carbon based thin film cell, with a nanotube cathode and a graphene anode sandwiching an active layer made of nanotubes and buckyballs, all made by printing or evaporating from inks. When fully developed this technology holds out the promise of new robust applications- a tough spray on PV surface for use in extreme conditions.

However, although important, PV cell development may not be the key issue . Solar power is inevitably limited by the fact that it gets dark every night, so energy storage is all important. Although batteries can be used in some situations, in general, storing electricity is hard, but it can be converted into hydrogen gas by electrolysis- and that can be stored, ready for use for electricity generation when needed, or for other fuel uses. So there is some interest in solar PV arrays linked to electrolysis, possibly using focused solar mirrors, since mirrors are much cheaper than solar cells. Large-scale Concentrating PV arrays ('CPV') in deserts are one option.

Another approach entirely is to use focused solar heat to make hydrogen directly by thermal dissociation of water molecules- but you need very high temperatures and the process is not very efficient. A more indirect approach, as in the Solar Gas project in Australia, is to use focused solar heat to convert a mixture of methane (natural gas) water and/or carbon dioxide into new higher value synfuels. CSIRO claim that you can get an extra 25% energy gain-a solar upgrade.

Meanwhile, Rice University's Nanophotonics Lab in the USA have developed a solar thermal system using nanoparticle absorbers which heat up in sun light and flash off steam when immersed in water . They have tested a parabolic focusing device. The system is claimed to have an overall energy conversion efficiency of 24%. Focused solar is already widely used to boil water and produce hot gasses for feeding into a combined cycle gas turbine. See

But of course that wont work at night. However, it is relatively easy to store heat. Molten salt heat stores are one option. Typically they use a mixture of 60% sodium nitrate and 40% potassium nitrate to store some of the heat from large focused-solar Concentrating Solar Power (CSP) plants, for use for continued stream raising at night, to make 24 hour power generation possible.

Several CSP plants have been built in desert areas around the world, some with molten salt heat stores, and much has been written about the prospects for desert solar in North Africa and the Middle East generating power for local use (including for desalination) and also for export via HVDC supergrids to the EU, as envisaged by the Desertec.

CSP is still expensive and, as noted above, some interest has been shown in large scale PV using focusing mirrors ('CPV') , which may prove to be cheaper. However recently Siemens pulled out of the Desertec project, saying they wanted to concentrate on what they felt were more appropriate technologies for them- wind and hydro. Even so, key players like RWE, E.ON, Deutsche Bank, ABB, and the German reinsurer Munich RE, along with 50 other groups, are still involved, and the idea of using desert solar seems unlikely to go away, with local CSP projects emerging independently. Egypt already has a CSP plant just outside of Cairo , Morocco is planning one, Algeria's 25MW Hassi R'Mel unit started up last year, backed by a 130MW gas-fired plant, and another solar plant is planned there, while Tunisia's 'TuNur' CSP project should ultimately have 2 GW of electricity generating capacity. In parallel, as I have mentioned before, Desertec and others have been looking at the potential for CSP in the Gobi desert, as part of a pan-Asian green supergrid power network. And the Sahara Forest Group is looking to combine CSP, desalination and biomass production in solar greenhouses- their project in Qatar is now running

There is thus no shortage of big ideas for the future. Moving things on even more, in a paper entitled 'Solar-Based Man-Made Carbon Cycle and the Carbon Dioxide Economy', Detlev Mo¨ller outlines a visionary plan to link solar electricity production such as Desertec CSP, with CO2 utilization via (chemical) air capture (i.e. from the atmosphere) as well as conventional CCS. CO2 would then be reacted with electrolytically produced hydrogen to produce fuels for direct use or for electricity production when needed. The 'SONNE' approach, as he calls it , would thus seek to build a man-made carbon (CO2) cycle, like the natural assimilation/respiration carbon cycle by which CO2 is recycled and changed from waste (emissions) to a resource, the process energy being supplied by solar energy. AMBIO 2012, 41:413-419 (DOI 10.1007/s13280-011-0197-6).

As I have noted before, there have been similar ideas circulating for linking hydrogen production from other variable renewables like wind with air captured CO2, to produce green syngases and fuels, or to upgrade biogas produced from biomass. See for example

Wind power may be the cheapest major renewable available at present, but the global solar resource is very much larger (wind, after all, is just an indirect form of solar energy), and the technology is developing rapidly, so longer-term solar, in all its varieties, seems likely to become a dominant option. There is already over 245GW of solar thermal capacity in use around the world, rivaling wind power : see my earlier Blog:

However, as I have indicated above, that could just be the start. Even in the cloudy UK: where so far nearly 2GW of PV has been installed- with more to follow, including a 32MW solar farm near Leicester

Christmas games

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If you are bored over the up-coming seasonal break, here are some energy related entertainments.

Power Grid is one of the best of the new wave of in-a-box multiplayer board games- a medium that has made an odd resurgence despite the massive advance and visual power of electronic/web-linked arcade games. Developed initially in Germany, you play meeting the grid power needs of cites in selected regions across the world, choosing from the full range of supply technologies, and then upgrading them, while having to constantly supply them with fuel, unless you choose renewable energy inputs! You can buy it for around £25 from Amazon

Board games need at least two players. But for the individual, here are some web based entertainments and resources.

With the recent floods in the UK and storms in the USA, the issue of sea level rise has moved up the agenda. There are some useful applets that display the new land contour maps for each region in the world, given different assumptions about sea level rises due to climate change:

Pretty grim . But for light contrarian relief:

And a correction

A bit more lively, if you want to watch energy supply systems in action, take a look at:

Live UK grid frequency balancing:

The complete UK grid system- monitor it direct via this data down load:

Watch PV solar inputs over (day) time in Germany:

There are also some fascinating dynamics charts showing daily power supply patterns in Germany over the past year at:

And if you want to try your hand at building a UK 2050 energy scenario see:

This is a much simplified version of DECCs full '2050 Pathways' model, which you can also tinker with by choosing different supply and demand levels. It includes access to web tool and an Excel calculator. Be warned it is quite complex!

You can store and share your results on the system and see some previous efforts:

If you are really intrepid (or obsessed!), you might like to try to use it to explore the details of the UK's new Electricity Market Reforms, which emerged at the end of November, to see how they match up to your favoured scenario.

A key issue is how the Contracts for a Difference (CfD) system will work. For example, will it support all the new low carbon energy supply options (renewables, CCS and nuclear) equally? The proposed new state owned 'counterpary' company will be in charge, and has to operate within the new overall Levy Control Framework, which sets a ceiling for the cost (which will be passed on to consumers) rising to £7.6m for 2020/21. In terms of which projects prosper, what matters is the level at which the CfD 'strike prices' are set- it's not going to be an open market, at least not for some while.

In its Electricity Market Reform: Policy Overview , DECC says that 'The CfD will be largely standardised across technologies. This provides a stable basis for investment, simplifies the process for allocating CfDs, and makes it easier to compare costs of different technologies. The standardisation of CfDs will also support the move to technology-neutral auctions in the longer term'. Note the phrase 'longer term'.

DECC adds 'However, initially there will be a degree of variation in CfDs for some technologies. First, there will be different generic CfD designs for low-carbon generation that is intermittent and baseload, reflecting the different ways that these plant operate. In addition, there may be some variation for some projects or technology types to recognise the different risk profiles of some projects or technologies.'

So maybe nuclear might be offered a better deal. A £100/MWh strike price? Or more? And less for wind? But DECC adds 'Any variations agreed will have to represent value for money and be consistent with state aid rules.

Then again, it may be that there won't be any new nuclear or CCS projects ready in time for CfD contracts by 2020, in which case the programme may initially focus on renewables. Adjust your scenarios accordingly! Although you will also have to factor in that there will be a long delay, until 2016, before carbon targets are set. So unabated (non CCS) gas plants may boom. In addition, there's the new Capacity Market auction system which may open up in 2014, ready for 2018/19, for backup and storage capacity- you may need some of that , as well as demand side measures. Plenty to play with. But we won't know which technologies the various scheme will back (except that those with CfD support will not be eligible of the Capacity Market contracts), so for now you are on your own! See

I hope some of the above entertain you! After the break, I'll be back with more hard info, including a report on my efforts at a 2050 scenario, using DECCs software, for the Pugwash UK group.

You may also be interested to know that from January, the long running renewable energy journal, Renew, which I edit, is shifting from a membership subscription delivery basis to free web delivery on-line via

As a parting shot, I couldn't resist relaying this joke, recycled by European Energy Review: "did anyone calculate how much it will cost to dismantle the nuclear power stations in Germany and build them back up again in the UK?"

Some of the old German plants were Boiling Water Reactors, earlier versions of the ABWRs Hitachi are now planning to build in the UK, but perhaps more accurately the joke reference could be changed to Japan, since they have two ABWRs, currently closed and likely to stay that way.

Seasons greetings!

Renewable methane

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There has been a lot of interest in developing national energy systems using renewable methane, rather than fossil methane, or even electricity, as a major energy carrier. Unlike electricity, methane can be stored and can also be transmitted with lower energy losses. In the UK the natural gas grid actually handles about four times more energy than the electricity grid. Moreover, if the methane is generated using green energy sources then it's carbon neutral, and if it's generated from bio-sources and also has CCS added, then its combustion can be carbon negative.

Biomethane produced from biomass/waste via AD is one option and this can be added to the gas grid. It's an idea that's spreading across the EU. See: 120529D22Overviewofbiomethanemarkets_rev1.pdf

However, there are also more advanced ideas. Germany has been pushing ahead with 'green gas' production, generating hydrogen via electrolysis, using excess wind-derived electricity. The hydrogen gas can be used as a fuel direct (e.g. in fuel cells or gas turbines) for electricity production, or added to the natural-gas grid, or used in vehicles. It can also be converted into other fuels. Audi will be launching their 'e-gas' vehicles in 2013, running on methane made from wind-derived hydrogen in combustion engines designed for gas use. E.ON has started work on a €5m wind-to-gas pilot project for gas-mains injection. But the hydrogen can also be converted to methane or other syn fuels, using CO2 captured from the air or from power plant exhausts, once again for use in vehicles, for heating or for power production. In effect it provides a way to store excess wind and also capture CO2. The later concept is central to the CO2RRECT project

There are several more complex versions of these ideas currently being promoted. In one variant explored by the Fraunhoffer institute, green hydrogen and captured CO2 is used to upgrade biomasss feed stock, the argument being that this will allow for the production of higher value fuels without having to use so much land area for biomass growing.

There are other possibilities. Enertrag AG is operating a 6MW wind-to-gas plant 120 kilometers north of Berlin, with the help of its partners, Vattenfall, Total and Deutsche Bahn. One option is to mix the hydrogen with biogas made from local corn waste to feed into CHP/ cogen plants, which produce electricity and heat. The power can be fed back into the grid at times when little or no wind is available, while the heat can be fed into district heating networks. During periods of low wind, the biogas plant can run on biomass alone. Enertrag is also feeding hydrogen gas direct into the natural gas grid and Greenpeace Energy is already buying some of this 'windgas' to sell to households. And of course it can also be used in vehicles:

It's not just Germany that is exploring these options. In Denmark, Haldore Topose have developed a highly efficient high-temperature electrolysis-methanisation system that can convert water and CO2 into a range of synfuels/syngases.

Finland is also looking at the idea, with the focus on transport. In January 2012, the Finnish Ministry of Transport and Communications set up a task force 'Future motive powers in transport ' to work out targets and plan paths for achieving them, for different motive powers in road, rail, water and air transport in 2020 and 2050. One of the motive powers considered was renewable methane, for which a sectoral report was prepared by Finnish Biogas Association and North Karelian Traffic Biogas Network Development Programme. An extended summary (31 pages) of the report 'Roadmap to renewable methane economy', in English, is available at

It outlines a goal of 40% share for renewable methane of transport energy consumption in 2050. Progress is already being made. Two large ships (300 GWh annual methane consumption) will be taken into use: Viking Grace (a large passenger ship for Turku-Stockholm route) and UVL 10 (Finnish border patrol boat). Both of them are currently under construction in Finland by STX and they both will be using Finnish Wärtsilä dualfuel methane-diesel engines. By 2020 at least 20 vessels are expected as a result of the UN/IMO sulfur emission restrictions in the Baltic Sea.

In road transport, their target is to have 2% of vehicles methane powered in 2020, i.e. 60,000 vehicles. Also, part of non-electrified rail transport is expected to move from diesel oil to methane by 2020, but in air transport, methane use is not yet expected to have begun by 2020.

In 2020 natural gas (NG) is expected to cover 60% of transport methane use of 2.5 TWh. Biogas (BG) and synthetic biogas (SBG) would contribute by 1 TWh (40%). After 2020 the share of renewable methane will continuously increase and by 2050 the use of natural gas and all other fossil fuels will end, on the basis of the groups scenario, in all transport sectors, although direct non-fossil electricity will provide some of the power.

Clearly then the renewable methane idea is moving ahead. And it's not just a European phenomena. Canadian multi-national Hydrogenics have also developed a wind-to-gas concept, for producing CNG for vehicles, as well as grid gas, heat and power:

In the UK, progress has been limited: as I will be reporting in my next blog, the emphasis has instead been on natural and shale gas. But AD biogas is now being taken more seriously and there are five new government-backed R&D projects aiming to speed up the adoption of energy systems using hydrogen and fuel cell technologies, funded by the Technology Strategy Board and the DECC with £9m, in a £19m programme focused mainly on hydrogen electrolysis.

So far the only UK 'air capture' project for synfuel production using COS from the atmosphere is that being developed by Air Fuel Synthesis. This has recently begun to receive press attention after have received backing from the IMechE: For more see

For more on wind to synfuel see:

Of course what matters in all of this is the energy-conversion efficiencies and costs. But good progress is being made. And the system-wide benefits of being able to store and then use otherwise wasted energy may offset the conversion costs. For more analysis see:

For an overview see the Macogaz 'Power to gas' fact sheet:

Waste not, want not

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We produce of lot of waste. Some is a potential source of energy. That may even include the carbon dioxide produced from combustion.

We usually treat carbon dioxide as a problem. But it can also be a solution. There are some interesting new ideas about using it to make fuels. One option is to use it to enhance algae growth. This can of course be done, in principle, with any bio-crop in large glass houses or other gas-tight enclosure: gas-engine exhaust is already used in commercial glasshouse horticulture for tomatoes etc, e.g. in Holland. But algae absorb CO2 more rapidly. MIT's carbon-capture and algae-bioreactor system is interesting. However there are evidently issues of maintaining efficient reactions, and the US company involved with this, GreenFuel Technologies, evidently has had financial problems. But trials by Sheffield University, using captured CO2 (from Tata steelworks near Scunthorpe) bubbled through algae tanks, are showing some promise:

Meanwhile Swedish utility Vattenfall has launched a pilot project using algae to absorb greenhouse-gas emissions from a coal-fired power plant in eastern Germany in a €2m trial run. Half the funding for the MiSSiON (Microalgae Supported CO2 Sequestration in Organic Chemicals and New Energy) project comes from Vattenfall, the other half from state and EU subsidies. The flue gas emitted at the Senftenberg brown-coal fired plant is being pumped through a broth using algae cultivated in 12 plastic tanks. The biomass produced can be used to produce biodiesel, to feed biogas power plants and as a nutritious supplement in fish food.

In a somewhat similar approach, Carbon Sciences Inc. says it's developing a technology to transform greenhouse gases into liquid portable fuels, such as gasoline, diesel and jet fuel. 'We are developing highly scalable clean-tech processes to produce liquid fuels from naturally occurring or human-made greenhouse gas emissions. From sources such as natural gas fields, refinery flare gas, landfill gas, municipal waste, algae and other biomass, there is an abundant supply of inexpensive feedstock available to produce large and sustainable quantities of liquid fuel to replace petroleum for global consumption, thereby eliminating our dependence on petroleum'.

Much more radical is the idea of reacting CO2 with hydrogen produced by electrolysis using electricity from wind turbines, to make methane and synfuels. See the UK 'Air Fuels' project and the various German/EU projects e.g CO2RRECT I'll be looking at this 'wind-to-green-gas' idea more in my next blog.


We also treat municipal and domestic solid waste as a problem, sometimes just letting it rot in landfill sites producing methane - a powerful greenhouse gas. Some of that gas can be and is captured, providing a cheap renewable fuel, but if it's burnt to generate power then you get carbon dioxide, although that could be captured and stored. Then the energy would be carbon neutral or even carbon negative, given that the production of food/farm waste has involved the absorption of carbon dioxide.

However, there are also other approaches, such as controlled anaerobic digestion of food/farm waste algae, with the emphasis on high-value food products rather than energy production. For example, start-up company Merlin Biodevelopments based in North Wales has devised a new way of growing protein-rich algae from waste food and cow slurry, which can be used in high-protein food products for human and animal consumption. An array of reactor tubes, in which the algae are cultivated, has been built in a polytunnel at the Moelyci Environmental Centre, Tregarth, near Bangor. So far Merlin has invested £500,000 in the project, including R&D grants worth £160,000 from the Welsh Assembly Government. It's designed its own low-cost micro AD plant, and its single 30m long polytunnel can produce 20 tonnes of algae a year. A second plant is due to open in south Wales soon and Merlin expects to be producing 1,000-2,000 tonnes by 2013. They say a 210 sq m polytunnel can produce as much protein in a year as 10 sq km of top-grade agricultural land. In a side project at Moelyci, Merlin is also investigating the value of processing AD residue into high value fertiliser using the algae system.

Using food waste for AD is clearly sensible. As I've noted before, Gwynedd Council are backing a new AD plant, which will process around 11,000 tonnes of food waste each year; converting it into renewable electricity and biofertiliser for use on nearby farmland. The food waste will be collected from local homes and businesses via a collection scheme run by Gwynedd Council. The new plant will replace the existing landfill site. It will be the second waste-fed anaerobic digestion plant built in Wales, following the construction of the Premier Foods plant last year near Newport.

In addition, food waste from homes in South Gloucestershire is now also being converted into renewable energy and organic fertiliser at a single site via AD. Food collected at the kerbside is being sent to an anaerobic digestion plant in Oxfordshire to be broken down by bacteria into useful gases and organic materials. The long-term arrangement with operator Agrivert, brokered by the council's waste collection contractor Sita UK, will see about 6,000 tonnes of food waste processed each year - equivalent to the weight of rubbish carried in 600 full refuse lorries. Agrivert manager Harry Waters said the company would expect to capture two million kilowatt hours of renewable energy from that amount of food waste every year. He said: "That is enough to power more than 400 family homes and produce organic fertiliser which will be used by farmers to grow food on more than 700 acres of land. Moreover, we capture a million cubic metres of methane that would otherwise be released to the atmosphere."

One way or another the AD biogas option looks likely to become increasingly important. The Anaerobic Digestion and Biogas Association recently said the Chancellor's efforts to give shale gas a helping hand with a 'generous tax regime', would be better spent on other forms of gas which are renewable, like biogas. The ADBA suggests biogas from anaerobic digestion (AD), 'which can provide energy security at a lower cost and, since it's renewable, with far lower carbon emissions and environmental impact than more experimental technologies like shale gas. AD can be scaled up fast and cheaply and with the right support could generate 40 TWh of biogas, equivalent to 10% of the UK's domestic gas demand, at the same time as boosting economic growth and creating 35,000 jobs.'

Storing energy

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The Energy Futures Lab at Imperial College London has produced a 'Strategic Assessment of the Role and Value of Energy Storage Systems in the UK Low Carbon Energy Future' for the Carbon Trust, using a holistic system-wide modeling approach. It concludes that storage would allow significant savings to be made in generation capacity, interconnection, transmission and distribution networks and operating costs. In all it says that storage could provide up to £10 billion of added value in a 2050 high renewables scenario.

However, the relative level and share of the savings changes over time and between different assumptions. In the high renewables 'Grassroots pathway' used by the research team, the value of storage increases markedly towards 2030 and further towards 2050, so that carbon constraints for 2030 and 2050 can be met at reduced costs when storage is available. For bulk storage cost of £50/kW per year, the optimal volume deployed grows from 2 GW in 2020 to 15 and 25 GW in 2030 and 2050 respectively. The equivalent system savings increase from modest £0.12bn per year in 2020 to £2bn in 2030, and can reach over £10bn per year in 2050.

The value of storage is the highest in pathways with a large share of renewables, where storage can deliver significant operational savings through reducing renewable generation curtailment i.e. when there is excess wind output available. In addition, storage could lessen the even larger wind curtailment requirement that would result if there was also significant amount of inflexible nuclear capacity on the grid. However CCS scenarios yield the lowest value for storage: 'adding storage increases the ability of the system to absorb intermittent sources and hence costly CCS plant can be displaced, which leads to very significant savings.'

Although it can be very useful in some situations, storage is not a magic solution for all our grid balancing problems: it is best used for specific purposes and durations. Crucially, Imperial say that 'A few hours of storage are sufficient to reduce peak demand and thereby capture significant value. The marginal value for storage durations beyond 6 hours reduces sharply to less than £10/kWh year.'

So it seems we are talking about short storage cycles, ready for the next demand peak- not long term grid balancing to deal with long lulls in wind availability. That makes sense: storage is expensive, so you want to use the hardware regularly to capture excess energy (when it's cheap) and sell it soon after to meet peaks, when energy prices are high.

This may be fine for short cycles. But how then do you deal with longer lulls? Especially in areas where there is a lot of wind capacity? Imperial say 'Bulk storage should predominantly be located in Scotland to integrate wind and reduce transmission costs, while distributed storage is best placed in England and Wales to reduce peak loads and support distribution network management.'

The report also offers some other valuable insight into the interactive nature of the overall system options and operation. For example, one option for balancing grids in the short term is the use of flexible demand - e.g. reducing peaks by time-shifting demand. Imperial say that 'Flexible demand is the most direct competitor to storage and it could reduce the market for storage by 50%.' So with that, you would not need so much storage.

Another option, which might also help with longer-term grid balancing, is the use of interconnectors. While pumped hydro is the cheapest large scale bulk electricity storage option, the UK does not have much potential for large amounts, and some have argued that it would be cheaper to get access to the large pumped hydro storage capacity on the continent, in Norway for example, using 'supergrid' interconnector links. That could also allow the UK to import power when there was a long lull in wind availability.

Interconnectors are expensive, but Imperial say that cross-channel links (maybe 12GW or more) could be 'beneficial for the system because it significantly reduces the amount of curtailed renewable electricity generation in the UK from 29.4 TWh to 15.1 TWh annually'. They add 'this also suggests there will be less scope for storage to be used to reduce the system operating cost through reductions in renewable curtailment. The operating cost savings component is indeed lower in cases with increased interconnection capacity, by about 50% compared to the baseline (Grassroots) case.' So we would not need so much storage.

Nevertheless, Imperial do see a need for perhaps 15GW of storage, given that 'in the Grassroots Pathway, storage has a consistently high value across a wide range of scenarios that include interconnection and flexible generation.'

While there is a good overview of some storage technologies, beyond the points as above about the relative merits of bulk and distributed storage, the report doesn't specify what sort of storage is best. Moreover, it is primarily about electricity storage. But how about rival modes of storage/ transmission e.g. heat or gas (including green gas). That would open up even more interactivity and may also improve the overall efficiency of the system and perhaps even reduce costs. After all, it is much easier to store heat or gas than electricity. Imperial admit that there are technical limits to conventional storage: the round-trip efficiency of storage can be low, and trying to increase it might not actually be worthwhile: 'higher storage efficiencies only add moderate value of storage' although 'with higher levels of deployment efficiency becomes more relevant'. They also warn that 'operation patterns and duty cycles imposed on the energy storage technology are found to vary considerably, and it is likely that a portfolio of different energy storage technologies will be required, suited to a range of applications.'

Fair enough: clearly more research is needed! Imperial do make a good job of promoting the benefits of storage and defending it against some critics. They say that 'by providing reserve capacity and the resulting improved scheduling of plant, storage enables more wind energy to be delivered at the time of generation. In such instances the round trip efficiency of storage does not directly affect the amount of avoided curtailed that displaces other plant.'

However they add that 'there remain a number of important unknowns with respect to the technologies involved in grid-scale energy storage, in particular relating to the cost and lifetime of storage technologies when applied to real duty cycles within the electricity network.' While it is useful to get some idea of the possible interactions and their impacts, these technological and operational uncertainties do make you wonder how useful high-level modeling is: we are some way from being able to optimize the design of the emergent new grid systems, especially given the advent of novel storage technologies. So perhaps its not surprising that, on policy, Imperial ends up saying, 'it is not clear whether government policies should incentivise the development and deployment of novel storage technologies, and if so, what sort of mechanisms should be considered, e.g. ranging from subsidies to direct procurement.'

Solar power - 245GW so far!

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For many people solar energy means PV solar electricity. But, although that is expanding, it's still only around 50GW of grid-linked capacity globally and, by contrast, the perhaps less glamorous but at present far cheaper technology of solar thermal heat collection is well ahead. In fact, globally, there is now more solar heat capacity in place than wind power capacity, and its still expanding. It could account for around one-sixth of the world's total low-temperature heating and cooling needs by 2050, according to a roadmap by the International Energy Agency (IEA). This would eliminate some 800 megatonnes of carbon dioxide (CO2) emissions per year, or more than Germany's total CO2 emissions in 2009. By 2010 there was 195GW (th) installed global (118GW of it in China), rising to 245 GW by 2011.

Paolo Frankl, Head of IEA's Renewable Energy Division, commented: 'Given that global energy demand for heat represents almost half of the world's final energy use - more than the combined global demand for electricity and transport - solar heat can make a significant contribution in both tackling climate change and strengthening energy security, The IEA's Solar Heating and Cooling Roadmap outlines how best to advance the global uptake of solar heating and cooling (SHC) technologies, which, it notes, involve very low levels of greenhouse-gas emissions. Some SHC technologies, such as domestic hot-water heaters, are already widely in use in some countries, but others, like large-scale solar-fired district heating, are just entering the wider deployment phase, while solar-powered cooling is still at the development stage.

Although SHC only makes a modest contribution to world energy demand at present, the roadmap envisages that, if governments and industry took concerted action, solar energy could annually produce more than 16% of total final energy use for low-temperature heat and nearly 17% for cooling by around 2050. This would correspond to a 25-fold increase in absolute terms of SHC technology deployment in the next four decades.

In addition to replacing fossil fuels that are directly burned to produce heat, solar heating technologies can also replace electricity used for heating water as well as individual rooms and buildings. This would be especially welcome in countries without a gas infrastructure and lacking alternative heating fuels. South Africa is cited as an example of a country that would benefit, as electric water heating currently accounts for a third of average household (coal-based) power consumption there.

On top of this, the report notes that solar thermal cooling technology - in which the sun's heat is used to power thermally driven absorption chillers or evaporation devices to cool air - can reduce the burden on electric grids at times of peak cooling demand by fully or partially replacing conventional electrically powered air conditioners in buildings. As climate change impacts, cooling is going to become a major issue around the world, not just in currently hot climates, and direct solar cooling has obvious attractions.

The roadmap also stresses the scope for expanding use of these technologies in industry. Often overlooked is several industry sectors' significant energy demand for low- and medium-temperature heat in such processes as washing, drying agricultural products, pasteurisation and cooking. Those industrial processes offer enormous potential for solar heating technologies, which could supply up to 20% of total global industrial demand for low temperature heat by 2050.

However, the IEA say that dedicated policy support is needed for these technologies to be used effectively, with a stable, long-term policy framework.,28277,en.html

Given the variable availability of solar energy, a key area for development and support is storage. As I've mentioned before, there are many solar heat collector projects around the EU linked to district heating networks backed up by large heat stores, some of them being interseasonal stores, with Marstal's 13.5MW solar array and linked heat store in Denmark being the largest so far. Some involve well insulated large tanks, or engineered thermal masses: for example for one of the first (at Burgdorf in Switzerland) see . However Underground Thermal Energy Storage (UTES), with excess heat stored in the ground in the summer, to be extracted in the winter, may be cheaper. Some systems use deep vertical boreholes: for example see the Drake project in Canada.

In the UK, the Centre for Alternative Technology pioneered solar heat storage, but in terms of UTES, much of the running is now being made by ICAX via their Interseasonal Heat Transfer system, which they aim to deploy in a wide range of construction projects, with ground storage of heating and cooling energy using insulated Thermal Banks for interseasonal thermal storage. For example ICAX worked together with REHAU on a pilot project for the Highways Agency at Toddington in which Interseasonal Heat Transfer was used to successfully capture solar heat energy from the road during the summer, store it in Thermal Banks in the ground and release it back to the road during the following winter to keep the road free of ice. REHAU pipework used for the solar capture, storage and heat distribution performed well during the trial, and REHAU has now formed an alliance with ICAX that will see it supply pipework for future IHT projects, typically in schools, prisons and commercial buildings where there is appropriate outside space for solar capture.

DECC seem to have woken up to the possibility of solar inputs to district heating networks, backed up by large heat stores, although at present the main focus in the heat storage field seems to be on its potential role in evening out demand on the electricity grid. DECC has launched a £3m competition in a drive to push heat storage technologies into commercial production. The Energy Technologies Institute is also investing £14m in Isentropic's gravel tank heat storage tech, to see if it can reduce strain on electricity sub - stations.

I will be looking at energy storage generally in my next blog, with heat storage being one option. Whatever the initial impetus for developing storage, solar heat technology could certainly benefit.

New tidal-turbine ideas

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Some large commercial-scale tidal-current turbine projects are now being installed, such as Open Hydro's device in an 8MW project in Brittany, and MCT's 1.2 MW Seagen has been feeding power to the Northern Ireland grid for several years. Next a 10MW SeaGen array is planned off N Wales. Many other designs are under test, at around 1MW scale, including the Atlantis AK 1000 and Hammerfest Strom's device.

However, tidal current turbine technology is still at the stage when there are many new ideas emerging at various scales. Some are specifically designed for shallow water, like the Pulse Tidal hydrovane system:

Some others are designed for low-speed water flows. Although the resource is large, low-speed projects are usually seen as much less economically viable - the power available is proportional to the cube of the water speed. But if cheap robust designs can be developed, there may be a niche for them even so. For example, the Hales Tidal Turbine uses a simple flat plate vertical axis rotor.

The Hales team says that 'Many tidal turbine designs being tested at the present time have very slim propeller or foil blades which require water flow speeds in the 3 to 4 m/s range to be effective, these tidal speeds only happen in a very few locations around the world, limiting their deployment'. But they say tidal turbines like theirs 'have much larger blade areas and can operate successfully in water flows between 1 and 2 m/s', with these lower-speed water flows being found 'in a great many tidal areas of the world'. They add that the turbines rotate slowly, in a drag type mode, so the blades 'can be made stronger to withstand the high stress loads created by the water flow, unlike propellers and foils which also try to produce a lift effect to improve their performance'. A prototype is being developed with help from Kingston University, with trials in the Thames:

Simplicity of design does of course also mean that the device should be cheaper. Hydro-Gen, based in France, have produced a low-cost low-maintenance floating marine or river-current energy-converter system, mounted under a platform supported by a catamaran, with a slide-able turbine and generator unit that can be raised out of the water for maintenance on a tower, and which can also be folded down for transport by truck. It can run at between 0.5-3.5m/s. There are 10-100kW bespoke 'tailor made' options available. A version with an annular collar/duct is being looked at. They have also built a floating-paddle wheel system for shallow/turbulent water.

More exotically, in the USA, Green Hydropower Inc., are promoting the idea of using vessels anchored in a swift moving body of tidal water as a base for tidal power generation via drag devices trailed behind. Lines from the stern of the vessel would have parachute-like drag anchors, which would create extreme amounts of line pull, this being converted onboard into rotational power that will then produce electricity. This idea avoids having to fix tidal devices to the seabed, e.g. by very large, costly and invasive, gravity anchor systems or monopiles driven into the seabed. By contrast, a vessel based tidal power unit is they say 'able to move into a body of tidal waters, anchor the vessel, operate the drag device systems, pick up anchor and move out in a fashion that allows the seabed and surrounding underwater landscape to remain very much unaltered and available for sealife and marine mammals to thrive, seasonal fisheries to operate and seasonal migration patterns to go undisturbed'. Though the developers accept that standard rotors have a much higher energy conversion efficiency than drag devices, they say 'what a drag device lacks in conversion efficiency can be made up for in quantity and size'.

They have patented some configurations with multiple parachute-like drag anchors mounted on a continuous belt system running out behind the ship, and around a drum on board - the parachutes collapse in the flow on the return journey. A bit of a long-shot perhaps, with fish and debris perhaps being trapped in the drag parachutes. But some river tests have been done:

If that seems too far fetched, then how about the 'Tidal Kite' idea, developed by Minesto. It's an aerofoil wing, with a tidal rotor and generator mounted on it, which is tethered to the seabed and free to move under the tidal flow. However it doesn't just stay in one place, but moves rapidly in a figure of 8 pattern under the influence of a rudder and the tether and lift forces created by the tidal flow. That means the rotor turns faster than if it was simply in the tidal flow - in fact, it's claimed, up to 10 times faster. Given that, unlike other tidal devices, it doesn't need expensive foundations or towers, it ought to be cheaper, and less invasive, and there should be many locations where it could extract power from relatively low tidal flows - thus, in effect expanding, the potential tidal resource. The strains on the tethering cable are going to be high, but Minesto plans to test a prototype off Northern Ireland

Some of these more radical ideas may be non-starters. Most existing tidal currents devices have been based on horizontal axis propeller-type designs, much like wind turbines, mounted on fixed towers or on the sea-bed, sometimes with ducts to enhance the flow. However vertical axis H or V shaped devices, as now being developed for offshore wind farms, have the advantage that they can accept flows from any direction. That may be less important with tides than with wind, since tidal flows are very consistently along one path - just changing direction along it every 6 hours or so. Nevertheless, a large Kobald vertical axis turbine was tested in the Straits of Messina in 2004 and in 2009 a version was also being developed for Indonesia:

In the UK, in addition to the Hales device mentioned above, Neptune's 1 MW Proteus has vertical axis rotors in a duct system, and is now on test in the Humber:

Vertical axis turbines don't have to be mounted vertically - cross flow turbines are also an option, with a horizontal shaft, like Ocean Renewable Power Company's version of the Gorlov spiral rotor:

Finally what about the idea of using wave action as well as tidal flows? C-Energy, in the Netherlands, have developed a vertical axis tidal turbine the blades of which rotate in the tidal flow, while the horizontal struts linking these blades to the central axis are shaped so as to lift the whole assembly up and down when acted on by wave motion:

It's early days yet, and the above review only covers a few of the many ideas now under test, but it could be that some of the new designs may win out.

New wave-energy technology

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Wave energy is developing rapidly, but perhaps not quite so rapidly as tidal-current systems - in part since it's harder to develop devices that can extract energy from the chaotic multi-vectored energy pattern that exists at the interface of the sea and the air, than from the smooth laminar tidal flows further down.

However, there are already some clear winners more or less fully developed, like the UK's Pelamis wave snake, the near shore Oyster hinged wave flap and Wavegens oscillating water column (OWC) system. In addition, Australian company Oceanlinx has developed a variant of the OWC concept and there are many buoy type systems, like that developed by US company OPT. But there are also a host of less well known and sometimes novel ideas emerging and being tested. For example, Wave device developer Wello Oy is testing a 500 kW device at EMEC on the Orkneys. Called the Penguin, it is a floating asymmetric vessel which houses an eccentric rotating mass, mounted on a vertical shaft.

A perhaps simpler approach is to use wave motion to power hydraulic pistons, as with the Sea Dog pump developed by Independent Natural Resources Inc in the USA In the UK Ecotricity is backing a bicycle pump-like 'Searaser' piston device, which, similarly, pumps sea water to shore, possibly up into a reservoir on a hill, so that electricity can be generated via a turbine when required. They may test a prototype soon off Falmouth:

Floats or buoys of various designs are clearly still popular ways to extract energy from the rise and fall of the sea. Some systems, like Clearpowers Wavebob, can be tuned to match different wave frequencies. Perhaps less familiar is the CETO system, which has an array of submerged buoys tethered to seabed pump units. The buoys move in harmony with the passing waves, driving the pumps which pressurise water that is delivered ashore via a pipeline, to drive hydroelectric turbines. The high-pressure water can also be used to supply a reverse osmosis desalination plant, replacing electrically driven pumps usually required for such plants. More at:

Somewhat similar is Atmocean's Wave Energy Sequestration Technology (WEST) system which consists basically of small buoys connected to one another over a stretch of ocean. They are planning to install 10 to 20 units 60 miles off the coast of New Jersey.

A more complex version has been developed by 40southenergy, with a part submerged unit, at a depth between 15 and 25 meters (depending on model type and site) called 'Lower Member', and one or more parts submerged at a depth between 1 and 12 meters (depending on sea state) called 'Upper Members'. The relative motion between Upper Members and Lower Member is converted directly into electricity. A full scale 100 kW prototype, the D100t, has been in the water since Aug 2010.

The conventional OWC concept has also be revisited: Dresser-Rand working with Cranfield University have developed a variable radius turbine called HydroAir, which is said to be more efficient and flexible than the normal two-way Wells turbines used in OWC.

Some devices make use of fixed platforms, with wave energy absorbers underneath, like Buldra system developed by Fred Olsen. Australian company, AquaGen Technologies has come up with a SurgeDriv system, which has a series of floats linked with tension cabling via the seabed and then to a generator on a platform above the sea surface, thus keeping as much of the infrastructure out of the water as possible. The floats can be retracted below the surface to ride out storms. It has a 1.5kW demonstration system at the Lorne Pier in Victoria.

Portuguese company 'Sea For Life' has developed a 'gravitational wave-energy absorber', WEGA. It has an articulated suspended body, semi-submerged in the water attached to a mount structure via a rotary head, which allows it to adapt to the direction of the waves: so it oscillates in an elliptical orbit. Power is extracted via an hydraulic cylinder, which pushes high pressure fluid through an accumulator and a motor, to drive a generator. Multiple devices can be placed on a single mount structure. The hydraulic motor and electric generator are on top of the mount structure, which protects them from the elements and enables easy access for maintenance.

Fully submerged systems also have their attractions - they can follow the circular motion of the waves under the surface. US Air Force Academy researchers in Colorado Springs have demonstrated that submerged energy converters can harness up to 99% of the kinetic energy inherent in an ocean wave. Dr. Stefan Siegel has developed a fully submerged cyclodial wave-energy conversion device, with funding from the National Science Foundation.

Ideas for smoothing out the energy absorbed from waves are also being explored. For example, the floating Danish Waveplane has a series of slots designed to catch waves at different heights, the captured flows then being used to create a vortex to drive a turbine. In the UK, Ecotricity are backing the Snapper linear motor wave unit invented by Prof. Ed Spooner at Edinburgh University. It has magnetically tripped springs storing burst of energy. The project is being co-ordinated by Narec with an EC FP7 grant.

Finally, Danish company Floating Power Plant is developing a 10 MW commercial version of their Poseidan prototype hybrid wave/wind device. Poseidon is basically a floating, anchored, platform, which can accommodate both wave-energy converters and wind turbines. It is claimed that it can achieve an efficiency in transforming inherent wave energy to electricity of 35%, and should be able generate 28 GWh per year if located in the Portuguese part of the Atlantic Ocean. A 37 meter wide 25 metre long 350 tonne model was tested at the Vindeby wind park, off Lolland coast in 2008. The wave system is based on a hydraulic power take-off system, using a double function piston pump to transform the energy from the wave into water pressure that is then sent through a turbine, thus generating electricity.

The wave-energy field is clearly still is a state of creative flux, with many rival ideas under test - the above is just a sample. It will be interesting to see which pan out.

New wind technology

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Nearly 240GW of wind-generation capacity has been installed around the world so far, mostly on-land and mostly based on conventional three-bladed horizontal-axis propeller type designs. But many new ideas and designs for wind devices are also emerging, with cost reduction for offshore projects being a key issue.

Going back to basics, there's a two-bladed propeller-type offshore turbine design being developed for offshore use by Dutch company 2-B Energy, which has the advantage that, unlike three bladed rotors, they can be more easily transported, fully pre-assembled and pre-tested, on a ship's deck to a wind farm construction site.

The Danish offshoot of China's Envision is also developing a 3.6MW two-blade design, with the outer sections of the blades being pitch adjustable. It's claimed that this will reduce stress loading and, since less tower and blade material is needed, could cut costs by 10%.

There have already been several designs for ducted wind turbines, with annular collars seeking to concentrate and accelerate the wind flow. In general the power augmentation is not seen as likely to outweigh the extra costs of the shroud system. But a new wind technology being developed in Japan, the Wind Lens, is claimed to be more effective. Verification experiments on a 5kW version have, it is claimed, yielded 2.5 output augmentation from devices with an annular ring compared with devices without, and according to Professor Yuji Ohya from Kyushu University, augmentation of up to three times is possible. He says 'the merit of two- or three-fold increase in power output leads to higher cost performance': given their efficiency, the turbines can be smaller, reducing costs. It also claimed that they can help improve safety, reduce noise pollution, therefore making the technology more accessible in urban environments.

Three 5kW units were put in a sea-shore park near Fukuoka city and two 100kW units have also now been built. In addition, Modern Power Systems reported that, last December, a demonstration plant was tested offshore on a floating platform in Hakata Bay in Fukuoka, 600 metres off a sandbar that links Fukuoka city with Shikanoshima Island. The tethered platform has two small 'Wind Lens'-equipped turbines and some solar panels. At wind speeds of 10m per second, the turbines can generate 3kW of power. Modern Power System says the floating wind power system will be used for verification experiments over the next year by Kyushu University together with the Environment Ministry and the city of Fukuoka. Then a new round of testing will be carried out in the southwestern tip of the Sea of Japan using a 60m platform with a pair of 200 kW wind lens units, and thereafter the aim is to build an offshore wind farm with giant 5000 kW 'Wind Lens' turbines, located at ocean depths exceeding 100m.

Japan is of course now very keen to press ahead with offshore wind projects, as it attempts to move away from reliance on nuclear power, following the Fukushsma accident. For example there are plans to build floating wind turbines off the Fukushima coast, initially, six 2MW units and then possibly up to 80 by 2020 in a 1GW offshore wind farm. So new designs like the Wind Lens may be in with a chance.

In parallel, vertical axis designs are being developed for offshore use, like the UK Aerogenerator X Nova project and the French Vertiwind.

These are H (or V) shaped devices, but EU/RISO's Deep Wind project is a 'eggbeater' shaped Darrieus design.

The big advantage of vertical-axis devices is that they operate regardless of which direction the wind is coming from, and the generator is at the base, not at the top of a tower. That makes them more stable - especially helpful for floating devices. It also opens up possibilities for very novel on-land developments. For example, US company Free Wind LLC has developed a unique vertical-axis, vortex-driven wind energy conversion system, WinDynamo(tm). The rotor is located inside stationary exterior cowling, with baffles and louvers that create internal vortices from impinging wind, driving a generator, and also a flywheel and compressed-air energy-storage device, mounted at the base. That ensures a more balanced and continual power output, despite variable winds. See

Being a vertical axis system, it is tolerant of turbulent, shifting, non-laminar air flows caused by vertical obstacles, such as buildings. So it can be located in cities and suburbs, where the electricity it makes will be used directly with lower distribution losses. In addition, since it has a stationary exterior cowling, a protective mesh can be installed around the intakes to prevent birds, bats or debris from coming in contact with the turbine, and lightning rods can be installed on top to avoid storm damage. The cowling will also contain any mechanical failure without damage to the surrounding infrastructure.

The developers also claim that the system is visually unobtrusive and silent, operating with very low friction and minimal maintenance by using low-cost permanent-magnet levitation bearings. Well it seems unlikely that any rotating device can be entirely noise free - at the very least there will be aerodynamic noise as the wind passes through the cowling and across the blades. But it looks like it could be an idea worth exploring. See Animation at:

However, perhaps wisely, most of the R&D effort around the world is focused on upgrading conventional horizontal-axis designs - developing larger units of up to 10MW or more, with offshore use the main focus. Some are sea-bed mounted, sometimes using tension leg designs, like the Dutch Blue H device. But fully floating devices are being tested to allow location in deep water further out to sea, like the Norwegian Hywind and Sway turbines

One of the most intriguing is the Swedish Hexicon design, with a series of turbines mounted on a hexagon-shaped lattice platform, which can rotate around a central axis to align with the wind direction. The Maltese government says it plans an eventual 36-turbine scheme to be located 20km off the island's north-east coast in water depths of 100-150 metres, with a massive 460-metre-wide platform. Being further out to sea it would also be much less visible than an inshore wind farm, and the areas around the Maltese islands are considered to be too deep to allow for the economical and feasible construction of fixed monopole wind farms.

However, if you want really exotic ideas, there's the Windstalk from New York design firm Atelier DN - a forest of over 1000 thin 55 meter tall, swaying poles, with embedded piezo-electric generators, using compression strains, as well as fluid pumping generators at the base, to convert the swaying motion into energy. Very much just a concept for the moment, but who knows, new ideas like this, and some of the others mentioned above, may yet prove to be winners.