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/

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

Greenpeace Eco City

If a picture speaks a thousand words, a multimedia-packed, animation-filled interactive town must speak a million. Which is why Greenpeace have launched EfficienCity - to exlain exactly what decentralised energy is and how it works in practice (which can otherwise be a wordy business).

If you still believe the government and think we need nuclear power and coal to stop climate change, come and pay a visit to EfficienCity, which shows how pioneering, real world communities around the UK are using decentralised energy. As a result, they're enjoying lower greenhouse gas emissions, a more secure energy supply, cheaper electricity and heating bills and a whole new attitude towards energy.



See:
http://www.greenpeace.org.uk/files/efficiencity/index.html
http://www.greenpeace.org.uk/efficiencity/about

Decentralised Energy: Woking Council Case Study

Woking Borough Council has pioneered a network of over 60 local generators, including cogeneration and trigeneration plant, photovoltaic arrays and a hydrogen fuel cell station, to power, heat and cool municipal buildings and social housing. Many town centre businesses are also connected to this local energy supply. The Woking energy model produces dramatic savings in energy use and greenhouse gas emissions. With further help from energy efficiency measures, the council has reduced CO2 emissions associated with the operations of its own estate, including social housing, by a staggering 77% over just 15 years. Some sophisticated engineering solutions have been deployed, including large thermal stores in the town centre car park and at the leisure centre at Woking Park. The balancing of the system is performed entirely by computer, and the control system can be readily accessed by remote engineers or council officers.

The generators are connected to users via private electricity wires owned and operated by Thameswey Energy Ltd – a company set up and partly owned by Thameswey Ltd, a municipal energy and environmental services company itself wholly owned by Woking Borough Council. These private wires have points of connection to the local distribution networks (in turn connected to the national grid), but in 2003 the council’s electricity infrastructure was 99.85% self-sufficient. In the event of a grid power cut the system can switch to island generation mode, meaning businesses and householders connected to the private wires continue to be supplied with electricity with only a short interruption while the system disconnects from the dead grid and restarts using a small black start generator (a generator which can start up with no external power input).



Woking was able to raise capital for energy infrastructure development initially through energy efficiency savings. A fund mechanism was established in a benchmark year for energy expenditure, against which savings accruing from energy efficiency measures were recycled, year on year, into further energy-saving initiatives. The substantial financial savings allowed the council to invest millions in energy supply innovation. Moreover, Thameswey Energy Ltd has attracted investment from Danish pension companies who recognise the steady low-risk return the initiative offers – energy systems like Woking’s are a common component of investment portfolios for pension and insurance companies across Europe.

Developing a private network enabled Thameswey Energy Ltd to avoid charges usually associated with the use of the grid. By circumventing these costs, it has been able to fund wires and generation to deliver low emission electricity in competition with conventional suppliers. For domestic customers in social housing, Thameswey provides electricity below the rate of other electricity suppliers as part of Woking Borough Council’s fuel poverty programme. The council estimates that it supplies heat and power to potentially fuel-poor households for 6–7% of the state pension – well below the 10% threshold of all household income spent on heating that the Government uses to  define fuel poverty.

While the Woking model is widely celebrated in energy circles, its significance for UK energy policy has yet to be fully appreciated. It shows that renewable technologies and cogeneration are highly complementary and lend themselves flexibly to a piecemeal engineering approach as finances allow. The key lesson from Woking is that, liberated from the constraints of centralised rules and infrastructure, cogeneration and renewables can assert their own competitive potential.

See www.greenpeace.org.uk/DecentralisingPower_summary or www.woking.gov.uk for more details.

Energy Generation: Waste Seaweed as Biomass

Japanese researchers have developed a biomass fermentation system that uses seaweed dredged from the shore to produce fuel for generating electricity. Seaweed is one of the few untapped sources of biomass energy that is easily obtainable in Japan, and the plan calls for the research stage to be wrapped up no later than March 2007, with full-fledged electricity generation to begin later in the year. The goal is to create the first power plant in the world to run off of seaweed.

Fresh seaweed is commonly eaten in Japanese dishes like sushi and miso soup, but the seaweed that washes up on the shore can rot and begin to smell, and it is unsightly as well. Collection and disposal of it is a major burden for local governments along the coast. At the same time, seaweed absorbs carbon dioxide as it grows, so using it as biomass could be an effective means of combating global warming as well as conserving oil resources. This is why Tokyo Gas Co. teamed up with the New Energy and Industrial Technology Development Organization (NEDO) in 2002 to begin work on a project to use seaweed as a source of biomass for energy production.

A test facility constructed in Yokohama first crushes large amounts of seaweed into a sludge-like state. After using micro-organisms to break down this semi-liquid material, the methane gas that results from this process is used as fuel for a gas engine that produces electricity. In the tests to date, one ton of seaweed has been processed per day, allowing the collection of 20 kiloliters of methane gas. In order to boost efficiency, this is blended with natural gas and converted into 10 kilowatts of electricity per hour. At present production levels, this is enough energy to power 20 households, and this energy is currently used to power lighting in offices at the plant, among other things.

Tokyo Gas Co. aims to complete research by March 2007 and then consider how the system can be put to larger-scale commercial use. The company has studied the optimal conditions for fermenting kelp, sea lettuce, and other types of seaweed and has determined that the system is feasible. There are hopes that the local governments and maritime companies that have struggled to dispose of seaweed in the past can be enlisted into this effort, which is both good for local communities and good for the global environment

see http://web-japan.org/trends/science/sci060824.html for more details.