 |
 |
|
Sewage treatment works
Ely Straw Burning Power Station
Greengairs landfill site |
|
|
|
|
Sewage treatment works
Minworth, West Midlands
The Severn Trent plc sewage treatment works at Minworth, West Midlands, is 100% self-sufficient in electricity and exports 12 % surplus to the national electricity grid.
The works is the largest inland treatment works in Europe, serving 1.3 million people as well as businesses in the Midlands. During a £90 million upgrade in 2001, 47 acres of biological filter beds were replaced with an activated sludge process. Minworth’s floating roof digesters use anaerobic digestion to process more than 4,000 litres of sludge a day, producing heat which is used to heat its own digesters and 75,000 cubic meters of sewage gas, mostly methane. The methane produced during the breakdown of the sludge is compressed to remove any water and excess moisture and to increase the pressure of the gas, which is then piped to the combined heat and power plant. The methane is then pumped into five gas engines, capable of producing 1.5 MW of energy each, where it is burnt to generate electricity. The waste heat from the engines is used to heat the digesters. The system is flexible and when more energy is needed, the amount of sludge going into the system can be increased to meet demand. Severn Trent saves money by not buying electricity made from fossil fuels from the national grid and earns money by selling its excess electricity production.
Click here for more information on the Sewage treatment works |
|
|
|
| |
| |
| |
Ely Straw Burning Power Station
Cambridgeshire
Ely Straw Burning Power Station in Cambridgeshire became fully operational in September 2000. It is the first modern, and the world's largest, straw fired power station. This 36MW facility consumes around 200,000 tonnes of straw and generates sufficient electricity every year to satisfy the needs of 80,000 dwellings. The plant is also capable of burning a range of other baled energy crops, such as miscanthus, and can use mixtures of up to 10 % natural gas. The facility has
created about 50 long term jobs. Long-term contracts are in place for the sale of the plant's entire output. Ely is a partnership formed between Energy Power Resources Ltd and Cinergy Global Power.
|
|
|
|
Click here for more information on the Ely Power Station
|
|
|
|
| |
| |
| |
Greengairs landfill site
Scotland
|
Opened in 1990, Greengairs Landfill Site is the largest contained landfill site in Scotland. It currently handles some 750,000 tonnes/year of waste. Around 55% of this is domestic, 30% is commercial/industrial and the rest is inert waste. Methane is produced from the biodegradable waste contained within the waste stream, and this gas, after being abstracted via a collection system, is used as the fuel source for the site's power station. The power station also exports 3.8MW to Scottish Power's 11,000V electricity network. This is due to increase by about 2MW as the plant develops.
|
|
|
|
The gas collection system is designed to abstract the maximum amount of gas from the waste, reducing the risk of gas migration from the site and any problems with landfill gas odours in the local village. Three thousand cubic metres of gas per hour is abstracted from over 60 operational gas collection wells drilled into the waste contained in completed areas of the landfill. These wells are connected to the site gas flare compound by over 6,000m of underground pipework and a series of dewatering pots. The collection system controls the emission of gas from the site, and maximises the quality and volume of gas to be used as fuel for the generators.
The gas is abstracted by two gas boosters. A third booster acts as a standby. The gas is filtered and delivered to a pressure-controlled manifold where it is automatically directed either to the gas flare or to the gas engine manifold where the gas pressure is increased.
The generator sets each produce about 1,000kW of electricity and burns 600-650m3 of gas/hour. The volume of gas consumed varies depending on the concentration of methane. The lower the methane content, the more gas is consumed. The whole landfill gas exploitation system at Greengairs works 24 hours a day, 365 days a year, with projected availability of 90%. About £2.5 million has been invested in the gas collection system and the power station.
|
|
|
|
| |
| |
| |
