Power to Gas

Scaling up clean renewable energy systems will generate more electricity than we need. The Centre for Alternative Technology (CAT) have put forward proposals [1] which would generate about 1,160 TWh of electricity in an average year. The average total demand would only be around 770 TWh per year. However, the problem is that the electricity isn't necessarily generated when we need it. There will be a mismatch between supply and demand, with both large surpluses and shortfalls.

The key is to develop large amounts of energy storage which can be saved until needed. At the moment technologies like fly wheels, compressed air, batteries and pumped hydro plants can't store enough energy to keep the lights on when there's reduced amounts of renewable electricity. For example, in 2010 there was little wind but a high demand for electricity due to the cold weather.

The solution is to develop a technology called Power to Gas or P2G.

Hydrogen
Hydrogen can be made by the electrolysis of water – splitting H2O into hydrogen (H) and oxygen (O) using electricity. Electrolysers can use electricity at times when there is abundant surplus of electricity, to create hydrogen gas for storage. In principle, hydrogen can be stored and then used directly to produce electricity using gas turbines or fuel cells. However, hydrogen is a very light gas that needs to be highly compressed for storage. Itis also quite explosive and can even corrode metal. It is possible to store relatively large amounts of hydrogen (a few 100 GWh) over long periods of time, for example in salt caverns. However, compared to natural gas (primarily methane), hydrogen is difficult to store and transport and there is almost no existing infrastructure suitable for it.

Biogas & Synthetic Gas
Biogas and synthetic gas are both produced from renewable sources. Biogas, a mixture of methane and carbon dioxide, can be produced by anaerobic digestion (AD) – the decomposition of biomass (for example, grass, animal manure or food waste) in an oxygen-free environment. Carbon neutral synthetic gas is made via the Sabatier process. Here, hydrogen (made by electrolysis) and carbon dioxide (from burning biomass, or from biogas) are combined to produce methane. Methane is easier to store than hydrogen. The Sabatier process can be seen as ‘upgrading’ hydrogen to a gas that is easier to handle. The process of using electricity to produce gaseous fuel is sometimes referred to as ‘power to gas’ (GridGas, 2012).

Methane gas is also the primary component of today’s fossil fuel natural gas. The methane in biogas and synthetic gas can be stored in very large quantities just as natural gas is currently. The UK today has a highly developed gas infrastructure that includes storage facilities, such as the Rough gas store off the coast of Yorkshire, which has a capacity of 35,000 GWh. However, methane is a powerful greenhouse gas, so it is very important that any escaping from pipelines or storage is kept to a minimum.

Biogas and synthetic gas, once stored, can be burned in power stations (again, like natural gas today) to provide energy when electricity supply from renewable sources is insufficient to meet demand. Gas power stations burning biogas or synthetic gas can be flexible – we can turn them on or off quickly. We can use them as ‘back up’ generation to meet demand when electricity supplies from variable renewables fall short. They can also supply industry for very energy intensive processes which would be difficult to run on electricity.

It is important to remember that burning methane is only carbon neutral when it is produced using biomass and/or renewable electricity. When methane gas is produced from biomass, the amount of CO2 released by burning it is reabsorbed when new biomass plants are grown, resulting in no net increase of GHGs in the atmosphere. Synthetic gas is carbon neutral when the hydrogen used is produced using renewable electricity, and the CO2 used is from non-fossil fuel sources (like
biomass).

The processes involved in creating a significant biogas and synthetic gas back up system have many losses associated with them. As energy is converted between forms (electricity and biomass to gas, and back to electricity), we lose energy in the process – about 50%. However, the ability to store energy in this way forms an integral part of an energy system powered by renewables, and is a good way of using electricity which would otherwise be surplus to requirements.

Who is making the technology happen?

A Sheffield company called ITM Power [2] is developing and installing technology to make Power 2 gas a reality.

References:
[1] http://www.zerocarbonbritain.com/images/pdfs/ZCBrtflo-res.pdf for the full report
[2] http://www.itm-power.com/energy-storage/power-to-gas-energy-storage-solution/

Off-Shore Wind Turbine Suction Bucket Support Structure

The Danish company Universal Foundation has developed a gigantic steel suction bucket which will act as a support structure for off-shore wind turbines. It has been engineered to sink rapidly into the sandy sea floor. Once in place, it will become stuck fast and form a rock-solid foundation for a wind turbine above the waves.

The structure works by creating quicksand around the rim of the 16-metre-diameter bucket, so it slips easily into the seabed. When the inverted steel bucket reaches the bottom, a pipe running up through the stem above sucks water out of the bucket. This causes water to flow into the bucket through the sediment, creating a sloppy quicksand at the rim. But when the bucket is in place, the pump is turned off, forming an extremely strong foundation. Trying to pull it out creates a vacuum in the bucket, like when you try to pull your foot out of wet sand on the beach.

Conventional foundations for offshore wind turbines are either a giant steel rod, driven into the seabed, or a steel jacket resembling an electricity pylon. Both need more steel – an expensive material – bigger, more specialised ships for deployment and are more prone to costly weather delays.

Two of the foundations left the Harland and Wolff shipyard in Belfast in January 2013 and will become the first deepwater deployment of the technology once planted 25 metres below the surface at Dogger Bank.

If all goes well, the technology may provide a secure basis for the thousands of giant offshore wind turbines planned for UK waters. The benefits include:

• It can be installed faster and at lower costs than conventional foundations
• It could save developers more than £5bn if used for the 6,000 turbines planned in the next decade or so, because it is 20% cheaper than conventional foundations, which make up about 30% of the cost.

For more details, see the following websites. The Guardian website has good videos, graphics and pictures:

• http://www.guardian.co.uk/environment/2013/jan/22/suction-bucket-offshore-wind?intcmp=122 
• http://www.universalfoundation.dk/
• http://www.harland-wolff.com/Services/Design-and-build-offshore-foundations/Universal-Foundation.aspx

Off shore wind turbines help to produce more fish

European fish stocks are under increasing pressure. The European Commission accepts that all important fish stocks in European waters can be described as overfished and a World Bank report claims that the worldwide cost of overfishing alone is a huge $50 Billion. The Common Fisheries Policy is our way of controlling overfishing by setting quotas for the amount fisherman are allowed to catch. Even with these quotas fish stocks are struggling to recover to sustainable levels and are being increasingly hampered by the effects of pollution and recently changing sea temperatures due to climate change.

Ironically the threat of climate change may bring about a positive change for fisheries in Europe. Offshore wind farms are looking more and more attractive as European states look to reduce their carbon emissions. It is predicted that 40GW of offshore wind capacity will be installed by 2020. This would roughly equate to 200km2 or 77 square miles covered by wind farms. This large portion of sea designated for electricity generation might be an unexpected boon to European fish populations.

Scientific studies of existing off shore wind farms are finding they can be a great benefit to the marine ecosystem they are placed in. One major benefit is that, due to safety concerns, no fishing can take place inside the wind farm. As some of these farms can be huge, the largest constructed is off the Kent coast and covers an area of 35km2, this effect can be significant. The wind farms effectively become Marine Conservation Zones (MCZs) where fishing is prohibited. This not only allows fish in the area to develop to full size but also stops the sea bed from being damaged from the scrapping of trawlers nets.

It is predicted that networks of offshore wind farms will greatly benefit fish populations by acting as MCZs. These zones may even help fisherman as fish and spawn will leave the protected areas and increase the population of nearby sea. It has been found that fisherman usually congregate near the edges of MCZs and experience much higher catches than in unprotected seas. More mature fish produce more spawn than younger fish so having an area of the sea where fish can grow to maturity can greatly help fish stocks and fisherman.

The foundations of the turbines themselves have also been show to have a positive effect. The steel ‘monopile’ the turbine is placed on has been shown to act as an artificial reef. This means smaller marine organisms grow on the hard structure, increasing the biodiversity of the area and producing a valuable food source for fish in the area.

Wind farms in the future could become teeming areas of bio-diversity and act as series of protected areas where fish can grow to maturity and reproduce in safety. The development of offshore wind farms will not only greatly reduce Europe’s carbon emissions and reliance on energy imports but may also let fish stocks recover so that they are once again being fished at a sustainable level.

These benefits pose the question of whether this should be done onshore as well. Most onshore wind farms are placed on fields grazed by sheep or cows. These grass fields are shown to be incredible un-diverse, biodiversity wise they are classed as deserts. The field itself however will financially support the farmer with only the turbines on it; maybe we should be looking to use these wind farms as nature reserves too?
This article was taken from Sheffield Renewables web site. Please check out their website.

Dynamic Demand Electricity

Dynamic Demand Control is a technology that could help stabilise the National Grid, reduce carbon dioxide emissions associated with power generation, and allow more intermittent renewable energy (like wind and solar power) than is currently possible.

The government has promised to connect significant amounts of renewable energy to the National Grid but many renewable sources are variable. Take wind: sometime it's windy sometimes it's calm. Already the Grid has to be continually balanced because the demand fluctuates all the time (we randomly switch kettles, lights etc. on and off). The National Grid company therefore has to pay for power stations to change their output continually on a second-to-second basis. This "response" service costs around £80 million a year (on top of the actual power supplied) and involves part-loaded generators which are less efficient and polluting. An important question is: "What will happen when large amounts of intermittent renewables are on-line? How do we keep the system balanced?" This is an important issue for system operators and the Government.

But what if we could design appliances that demand most of their power at times when there is excess power available on the grid? Take a fridge. It needs electricity but it doesn't really care exactly when it gets it as
fridges have large thermal storage. The good news is that you can measure the excess power on the National Grid from any plug socket in the country. (You just measure the "50Hz" AC frequency because it drifts a little as generators slow down and speed up). The device you need to do this would cost less than £5 and would fit into a matchbox.


It should be possible to provide the same stabilising service to the National Grid more cost-effectively using dynamic demand fridges. This means such a fridge could earn money throughout its life. The organisation Dynamic Demand has been founded to promote this technology. They want to see Government, regulators and industry seriously debate the possibilities. After all, if such a technology could reduce the carbon dioxide emissions associated with power transmission and allow more renewable energy onto the power grid, can we really afford not to have it?

See www.dynamicdemand.co.uk
Also see http://gridwatch.templar.co.uk/ for near real time information about the grid

North Sea Renewables Grid

Although critics of wind power suggest that wind is a variable energy source and can’t be relied upon to keep the lights on, this isn’t actually the case when wind power is distributed over a large area like the North Sea. Variations in production at one wind park can be partly balanced by that of another park several hundreds of kilometres away.

To demonstrate this concept, Greenpeace commissioned a report based on what would happen if real wind speeds over the North Sea were applied to more than 100 envisioned wind power projects with 10,000 turbines. If all projects from Belgium, Denmark, France, Germany, Great Britain, Netherlands and Norway were built there would be an installed capacity of 68.4Gw.

The top graph below shows how the power output of the propose London Array would fluctuate with changing wind speeds. When combined with all wind farms around the British east coast, the power production starts to level out as a dip in generation around London could be offset by heavy winds around Scotland. The final graph shows how wind production stabilises even more when combining all wind farm output from countries bordering the North Sea.

To capitalise on the balancing nature of distributed wind farms, a large North Sea grid spanning 3,850 miles would be required to connect all of the wind farms together. Such a grid would facilitate trade and increase security of supply by dispatching power from offshore wind farms to different countries depending on the highest demand. Moreover, an offshore grid allows the import of electricity from Norwegian hydro power plants to Britain and other countries. For some hydro plants, excess power (when the wind blows and sun shines) can even be used to pump water back into reservoirs, working like a huge water-battery. Biomass from European countries could also be fed into this grid.

A system of this nature with many thousands of wind turbines is more reliable, and energy production more secure because the impact of maintenance or defects will be negligible when compared to a large coal or nuclear plant going off line. Another advantage of a North Sea grid is that any future wave power, floating wind Turbines and tidal power stations could also be connected up to provide more power, stability and distribution of power between countries.

If this proposal were to be implemented then 70 million homes or 13% of the annual electricity consumption of the seven European countries could be met.

For the full report, see
http://www.greenpeace.de/fileadmin/gpd/user_upload/themen/energie/offshorewindgrid_final.pdf

BedZED - Sustainable Homes

The Beddington Zero Energy Development, or BedZED for short, is the UK’s largest carbon neutral development. It provides 82 residential homes with a mixture of tenures and sizes. The project also includes buildings for commercial use, an exhibition centre, a children's nursery and a show flat so that visitors may see what it is like to live at BedZED.

Buildings are constructed from thermally massive materials that store heat during warm conditions and release heat at cooler times. In addition, all buildings are enclosed in a 300mm insulation jacket.
BedZED houses are arranged in south facing terraces to maximise heat gain from the sun, known as passive solar gain. Each terrace is backed by north facing offices, where minimal solar gain reduces the tendency to overheat and the need for energy hungry air conditioning.

Where possible, BedZED was built from natural, recycled or reclaimed materials. All the wood used has been approved by the Forest Stewardship Council or comparable organisations.
BedZED homes and offices are fitted with low energy lighting and energy efficient appliances to reduce electricity requirements. Visible meters are mounted in homes and offices so the occupiers can keep tabs on their electricity consumption.

BedZED receives power from a small-scale combined heat and power plant (CHP). In conventional energy generation, the heat that is produced as a by-product of generating electricity is lost. With CHP technology, this heat can be harnessed and put to use. At BedZED, the heat from the CHP provides hot water, which is distributed around the site via a district heating system of super-insulated pipes. The CHP plant is powered by off-cuts from tree surgery waste that would otherwise go to landfill. Should residents or workers require a heating boost, each home or office has a domestic hot water tank that doubles as a radiator.

Making the roof areas green with sedum plants helps increase the site’s ecological value and its carbon absorbing ability, as well as giving the occupants private gardens. Next to the green roofs are the photovoltaic panels to generate electricity.

Transport energy accounts for a large proportion of the energy consumption of any development. A green transport plan promotes walking, cycling and use of public transport. A car pool for residents has been established. BedZED has good public transport links, including two railway stations, two bus routes and a tramlink. On-site charging points for electric cars and a free public electric vehicle charging point is already available in Sutton town centre. BedZED's 10-year target is to produce enough electricity from photovoltaic panels (which convert sunlight into energy) to power 40 electric vehicles. It is hoped that a mixture of private cars and vehicles available through the car club will minimise fossil fuel use as the community settles. For owners of electric vehicles energy and parking will be free of charge.

To find out more search Google for “BedZed” or visit http://www.zedfactory.com/projects_mixeduse_bedzed.html