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September 2012 Archives

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. http://www.iea.org/publications/freepublications/publication/name,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 www.jenni.ch/ . 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. www.dlsc.ca

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. www.icax.co.uk/

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. www.isentropic.co.uk/

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.

With the talk in the United States all abuzz about the presidential election this year, President Obama (and advisors) and Mitt Romney (and advisors) have to act as though they know the solution to lowering unemployment and raising economic growth rates. It is hard for anyone running for an election to admit that they might be powerless to affect some energy and economic realities. In this post, I discuss the trend in the figure below: US monthly personal-consumption expenditures (PCE) for food and energy goods and services as a percentage of total household expenditures. I think it is completely possible that the stop in the declining trend of PCE for food and energy that stopped in the early 2000s is indicative of the new reality facing the United States energy and overall economic (and debt) situation.


US PCE Energy and Food.jpg

Figure 1. Personal-consumption expenditures of US households expressed as a percentage of total expenditures. Data are from the US Bureau of Economic Analysis Table 2.8.5.

 

It doesn't take a PhD in statistics (or engineering, or anything else) to notice the major change in the trends of the time series in the figure. In 1999, the 4-decade trend of decreasing PCE for energy stopped declining and started increasing. In 2007, the (at least) 45-year trend of decade trend of decreasing PCE for food stopped decreasing - just before the beginning of the Great Recession that began in late 2007.  Adding the PCE for "food + energy" shows a minimum PCE percentage of 11.7% in the first two months of 2002. It is a good question of whether or not this will be the minimum percentage PCE for "food + energy" for the US ... for all time.

Several analyses have been done investigating a seeming threshold percentage of US PCE that can be spent on energy goods (and services) before it induces or plays a large role in causing a recession (see James Hamilton's blog entries here (July 14, 20102), here (March 6, 2012), here (September 19, 2012), and there's another one or two or more in there somewhere tracking the same things). But there is much value in considering the role of food in PCE along with energy PCE because food is both the original source of pre-industrial power and it holds high priority in a "hierarchy of needs" sense.

The reason to add the PCE for food and energy is because food is technically an energy source. It is too bad that the statistics needed to plot the data of the figure even further back than 1959 are not readily available, but it is practically certain that the percentage of PCE for food continues higher as one moves back further in time. Before fossil fuels and significant industrialization using wind, wood, and water power in the early 1800s, food was the major energy resource for prime movers. These prime movers were the muscles in humans and animals doing the majority of the physical ('useful') work and providing the most aggregate power. Thus, the quantity of food and fodder produced from the land had the major influence on the amount of power for agriculture and a little industry. The book Heat, Power, and Light: Revolutions in Energy Services, by Roger Fouquet, shows a similar historical graph for the United Kingdom in which he estimates the expenditures for domestic power in the 1500s as at or above 100% of GDP. Thus, in preindustrial times, practically all GDP was to produce power, or useful work!

The data plotted in the figure should be shown in the United States presidential election debates. I'd like to know what our leaders think of this graph and why they think their policies can or cannot affect the trend (or rather new trend since the early 2000s). The likely truth is that demographics and resource constraints have caught up with much of the 'advanced' economies (e.g. EU, US, Japan). There are less young people working to pay for older people to retire. There are fewer older workers retiring because their pensions and retirement funds are not sufficient, thus not making room for new and younger workers. The conventional oil alternatives (oil sands, deepwater, oil shale, biofuels) don't have the same level of pure energetic value of those of the past, and this is the reason that oil prices must remain at current levels in order for new oil supplies to remain viable. I wrote in a 2011 article in Sustainability (see here) how energy return on investment (EROI) and oil price are related. Alberta oil sands are practically the marginal oil supply (in North America at least) and because the oil sands have EROI < 4-5 then the oil price must be near or above 90 $2012/BBL. The economy remains sluggish, unemployment is still below 8%, and the jobs that people are getting are lower paying.

I think that both the 'extreme' left and right are wrong in their approaches. The U.S. can't borrow money and go further into debt to give people high paying jobs while lowering employment, and the U.S. can't borrow money to maintain the same defense budgets of either the Cold War or recent post-Cold War eras. Resource constraints are imposing their real nature upon our real economy. No lowering of interest rates can prevent this impact, and this is why the unprecedented length and level of low US and EU interest rates are not having the 'expected' effects. What we see is that demand for fuels and energy services have decreased (particularly less light duty vehicle miles traveled) since 2008 at a peak near 3 trillion miles (for a nice graph of US vehicle miles traveled see above link to Hamilton blog on Sept. 19, 2012 and search Stanford research on 'peak travel').

Peak travel. A 'bottom' percentage PCE on food and energy. A 'bottom' of interest rates. Coincidence? I think not.

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: www.pulsetidal.com/

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: www.hales-turbine.co.uk/

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. www.hydro-gen.fr

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: www.youtube.com/watch?v=HCCE0JhvkGo

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 www.minesto.com

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: www.pontediarchimede.it

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: www.neptunerenewableenergy.com

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: http://www.orpc.co/orpcpowersystem_tidgenpowersystem.aspx

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: www.c-energy.nl/

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 www.inri.us. 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: www.ecotricity.co.uk/our-green-energy/our-green-electricity/and-the-sea/searaser

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: www.carnegiewave.com/

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.http://atmocean.com/

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. www.40southenergy.com

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. www.dresser-rand.com/products/hydroair/

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. www.aquagen.com.au

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. www.seaforlife.com/

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. www.floatingpowerplant.com

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. www.2-benergy.com/

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%. http://www.windpowermonthly.com/news/1115270/Close---Envisions-36MW-offshore-machine/

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. http://www.mdpi.com/1996-1073/3/4/634

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 http://vimeo.com/13654447 and the French Vertiwind. www.youtube.com/watch?v=kkqzlEqsxww&feature=player_embedded

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

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 www.windynamo.com/

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: www.youtube.com/watch?v=9a3AgZ3R9Fk

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 www.sway.no

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. www.hexicon.eu/

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. http://atelierdna.com/?p=144

Earlier this year I discussed (The EROI of Algae) some research at The University of Texas on an experimental algae to fuels experiment. A couple of new papers have now been published on the energy return on investment (EROI) of algae-based bioenergy when coupled to a wastewater treatment plant (Energy Return on Investment for Algal Biofuel Production Coupled with Wastewater Treatment: http://www.ingentaconnect.com/content/wef/wer/2012/00000084/00000009/art00002). The reason why it is energetically beneficial to couple a wastewater treatment plant to an algal growth facility is because algae, like terrestrial crops such as corn and soybeans, require nutrients as inputs. Wastewater has a high quantity of nutrients that actually must be removed before discharging the water into the environment...in some cases to prevent algae blooms! Oh the irony...


In another recently published work, we established that a best case scenario using known technology (not possible future ideas of new strains of algae), the EROI of algae-based fuels was 0.36 when adjusting the relative energy quality of the energy inputs and outputs (for a free accessible copy of the paper see Comprehensive Evaluation of Algal Biofuel Production: Experimental and Target Results

 http://www.mdpi.com/1996-1073/5/6/1943).  Note that this value of EROI = 0.36 is what we called a 2nd Order EROI that considers only the energy inputs from direct energy consumption (e.g. electricity, fuels) and the energy embodied in materials (mostly nutrients such as nitrogen and phosphorous). If you want to see work that documents the methodology and assumptions of input values, this work is a good place to start to then lead to other literature.



When you add the wastewater to the algae-to-fuels process...

...it could be possible to obtain a 2nd order EROI of 1.4 (as compared to approximately 0.4 without that wastewater). Note that there is energetic value in extracting energy directly from the wastewater, such as via anaerobic digestion, and this can lead to a second-order EROI of 0.4 from a process that otherwise would have EROI = 0 (e.g. generate no useful energy).  This 2nd order EROI = 1.4 sounds promising, indicating that more energy is produced than is needed for production (EROI = energy output / energy input). However, it does not include every investment needed to produce algae and convert it to a fuel. A rough rule of thumb (as if there really is a rule of thumb for producing fuels from algae) is that the capital and labor costs would be near half of the costs of other operating and maintenance costs. By doubling the energy inputs to account for capital and labor, the EROI will be < 1. 

Further, just because a fuel or electricity resource has EROI > 1 even after accounting for all system inputs, that criteria does not relate to societal viability. For example, there is some evidence to support the idea that an EROI > 5 might need to hold for transportation services or liquid fuels (at least in the modern economy). But this is an ongoing area for study.

What does all of this mean? Well, in my opinion, it means we need to treat our liquid fuels (with high-energy density) as very precious resources as we have yet to prove that we can create a renewable liquid fuel even nearly equivalent to gasoline (petrol) or diesel. There is some evidence to show that the United States goes into recession if the EROI of gasoline at the pump drops to near 5 (http://environmentalresearchweb.org/cws/article/news/44403). Let's keep trying for alternative fuels, but also keep perspective to think about alternative modes of organization and transportation in general. The new targets for US mileage standards to increase to 54.5 miles per gallon are a good step toward focusing people on the constraints on the supply of oil and oil/transportation alternatives.

Offshore wind

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In all there is over 230GW of wind-power capacity in place globally, nearly all on land, but offshore wind is moving ahead quite rapidly. The UK is in the lead with over 1.8GW operating, well ahead of Denmark and Germany, but China, the USA and Japan are now also in the race, although so far only China has any projects in operation, 234 MW so far. The US government has just announced a $180m 6-year plan to fund four offshore wind projects and Japan has plans for six 2 MW floating units and then possibly up to 80 by 2020 in a 1 GW offshore programme. Meanwhile France has plans for 6GW by 2020.

The costs are higher than for on-land wind, due to the difficultly of installing and maintaining machines offshore, and the need to have expensive undersea grid links back to shore. However new technology (including floating wind turbines) should be able to reduce the installation costs, and once there are multiple arrays in place the cost per turbine of shared grid links falls.

Studies by the Offshore Wind Cost Reduction Task Force, set up by the UK government, and by the Crown Estate, suggest that it should be possible to reduce the cost of offshore wind energy in the UK to £100 per megawatt hour within seven years with the right actions from the industry. As Wind Power Monthly reported, both studies conclude that the costs of offshore wind energy could be driven down by almost 30% by 2020, making it competitive with established forms of energy generation.

Given that the UK is targeting 18GW of offshore wind energy by 2020, the cut in costs envisaged in the two reports from the current £140/MWh to £100/MWh would save over £3 billion annually. The task force report sets out 28 separate actions required by industry and government to achieve the cuts, including supply chain, planning and consenting, finance and grid infrastructure.

There has been a lot of negative comment about the high cost of offshore wind recently, for example, from the governments advisory Climate Change Committee. So for offshore wind proponents these cost projections are good news, as long as it doesn't give the government an excuse to cut support levels prematurely, as some argue they did when PV solar costs fell.

On land wind may be relatively cheap (it's the cheapest major new renewable source), but, although we will need as much as we can reasonably get, there are obviously limits to how much can be installed. The current plan is to have around 13GW in place by 2020. By contrast the offshore resource is very large and less constrained - being offshore it's less visually intrusive. Long term we could have 100GW or more, if we go further out to sea. Given larger machines and higher wind speeds, offshore wind also has higher capacity factors than on land wind, i.e. the actual energy out compared with installed capacity, sometimes also called the load factor (although there are subtle differences!). On-land wind projects in the UK typically achieve around 25% load factor averaged across the UK, although that's moving up to 30% with new technology and of course it's higher on good windy sites. But offshore wind is much more reliable and unaffected by topographical features. Recent results from Demmark show that its latest offshore wind farm, Horns Rev II, has attained a 47.7% capacity factor. The full list of actually measured 'life time' CF's for Denmarks offshore wind farms is at: http://energynumbers.info/capacity-factors-at-danish-offshore-wind-farms

For the UK, DECC 2050 Pathways calculator uses a load factor of 45% for offshore wind. Given the new Danish data, that may turn out to be low, since by 2050 wind turbines will have improved further and will be further out to sea in windier locations. 50% seems a realistic possibility. For comparison, DECC quotes UK nuclear load factors as 69.3% (2006) 59.6% (2007) 49.4% (2008) 65.6% ( 2009) and 59.4% (2010). That averages out at 60%. Nuclear proponents say that new nuclear plants will do much better, with talk of 80-90%, but that has not yet been proven.

In my next blog I'll look at some of the new technologies emerging for wind power, both on land and offshore. But as a taster, there were 104 offshore wind-turbine tower-support designs competing for support in the Carbon Trusts Offshore Wind Accelerator programme, which runs until 2014. Four were shortlisted for further development: Keystone's wonderfully named 'Inward Battered Guide Structure' (IBGS), which is a 'twisted jacket' tripod tower design; SPTs Self Installing wind turbine; Harland and Wolff's Universal Foundation design (basically a massive weighted bucket sitting on the sea bed ); and the Gifford BMT Freyssinet Gravity Base foundation. A version of Keystones IBGS tower/base has been installed for testing at Hornsea and there are plans for a full test with a wind turbine soon. The Universal Foundation design is also to be tested soon, on the Dogger Bank.

Meanwhile the HiPRWind, R&D programme with 60% (€11 m) EU funding is aiming to test a 1.5 MW wind turbine on a triangular floating structures off Spain. The Biscay Marine Energy Platform (Bimep) will be located 1.7 kilometres from the Basque Country in 50-metre deep waters. It's predicted that the cumulative global market for floating wind turbine structures could exceed €200 billion by 2030. www.hyperwind.eu

Clearly offshore wind technology is moving ahead rapidly and we are likely to see major projects in the North Sea and elsewhere around the world. Some of them are already breathtaking. But ahead there could be even more dramatic developments, like the huge circular supergrid ring main around the edge of the North Sea, with nodal links to wind farm arrays, as proposed by the Dutch Society for Nature and Environment: www.we-at-sea.org/index.php?keuze=n&nummer=55

That's some way off. For now, the UKs next big focus is the 1 GW London Array, around 7 miles off shore in the outer Thames estuary, in water up to 25m deep with 341 turbines. The government has also given a green light to projects off the north Norfolk coast, at, respectively, Race Bank (580 MW) and Dudgeon (550 MW). Plans for the 278 turbine Atlantic Array off N Devon/S Wales continue, while three 400-500MW arrays are planned off Scotland. There's also a proposal for a huge 2.2 GW project in the Irish sea, to be called Rhiannon.

Major projects like this will obviously have to be carefully assessed in terms of environmental impacts. However, the studies carried out so far have not found significant problems. Crustaceans seem to like the foundations, sea mammals stay clear, as do birds. http://iopscience.iop.org/1748-9326/6/3/035101. But in some locations there can be problems. For example, the 500MW Docking Shoal project was refused over bird-impact fears, and the National Trust is opposing the proposed Atlantic Array wind farm, which it sees as being squeezed in between 'two sensitive coastlines'.