Organic Rankine Cycle Biomass Power System
The UK government, corporations and the general population find climate change to be a pressing issue and some prominent corporate actors are tapping into global supply chains to power their operations with increasing amounts of renewable energy as a means of curbing carbon emissions.
In one example, British Sky Broadcasting – the largest pay-tv broadcaster in the UK – enlisted the services of an Ireland-based contractor – ClearPower – to install and operate a combined cooling, heat and power plant fueled by biomass at its West London facility. BSkyB has set a goal of offsetting up to 40% of the broadcasting facility’s carbon dioxide emissions. The facility also features an onsite wind turbine to help accomplish that goal.
The biomass plant was manufactured in Italy by Turboden, a subsidiary of US jet engine and gas-fired turbine producer Pratt & Whitney. The plant is comprised of a “5.2 MW thermal furnace, a 1 MW electrical organic rankine cycle generator and 4.1 MW of heating of which 2.3 MW is converted to cold water and the remainder is used to provide hot water to the complex,” according to ClearPower’s website.
ClearPower verifies the quality and sources the woodchips used to power the biomass plant from a location located just outside of Oxford, Daryl McMenamin, a ClearPower Design Engineer told Breaking Energy. ClearPower completed a feasibility study to evaluate the possibility of expanding the plant in a district heating loop around the campus, but is currently working to optimize plant operations by running it for at least a year before deciding on expansion. The plant started up in November 2011.
Biomass Takes Flight
In another example of a large UK-based company adopting a renewable energy solution to reduce their carbon footprint, BAA Airports – owner/operator of the UK’s largest airport, London Heathrow, and several others – is the site of Turboden’s second organic rankine cycle biomass plant in the UK.
“Traditionally, Turboden has developed projects in which ORC units were suitable for district-heating in small or medium-sized villages,” says Paolo Bertuzzi, a general manager with Turboden. “With these larger scale tri-generation projects, Turboden is delivering cost-saving renewable energy solutions for some of the UK’s most prominent institutions,” the company said in a statement.
The plant will use wood waste to generate 1.8 MW of electricity and 8 MW of thermal heat and cooling to three separate airport terminals. “The Energy Center is substantially complete and is in its first phase of commissioning. The biomass component will commence commissioning in late September 2012, with the wood chip required in mid-October,” Erika Bugnar, Heathrow Airport Press Officer told Breaking Energy via email.
“The power generation component of the plant will follow in late November, after which it will provide stable low level heat and power to support the Terminal 2 program. The plant will then be optimized for efficiency during 2013.”
“Over the next 15 years, Heathrow’s biomass supplier LC Energy will provide the airport with over 30,000 tons of premium grade wood chip fuel annually. This is harvested in strict accordance with Forestry Commission sustainability practices and is sourced within a 100-mile radius of Heathrow, typically within 50 miles to limit the carbon life-cycle impact of the supply chain,” said Bugnar.
She added that, “A key feature of this supply chain is that the wood chip is sourced entirely from sustainably harvested virgin wood, with each tree felled under license from the Forestry Commission as part of structured woodland management schemes. This promotes and encourages better woodland growth, increased biodiversity, rural economic development and – importantly, long term renewable timber resources.
Once felled the timber is transported to one of LC Energy’s timber hubs, the closest of which is just two miles south of Heathrow. The hubs currently have 30,000 tons of timber in stock, seasoning to be ready for chipping and delivery to the Heathrow Airport Energy Center in October 2012.”
The Turboden biomass plant is part of a larger carbon reduction initiative being undertaken at Heathrow, which airport representatives are clearly excited about, as Bugnar explained to Breaking Energy. “This project is the first phase in the implementation of Heathrow’s Low Carbon Energy Infrastructure Strategy for 2020, which calls for total CO2 saving by 2020 of approximately 42,000 tons from energy infrastructure investment. It delivers the on-site renewable energy resource required for the T2A development under the terms of the Terminal’s planning agreements.
In addition the project supplements Terminal 5 district heating infrastructure with efficient thermal energy, and safeguards for the future expansion and improvement of the Heathrow-wide district-heating network.”
The technology itself is unique, “in that it uses an organic fluid instead of steam to drive a turbo-generator, which can range in nominal output from about 1 to 10 MW and up. The system employs a closed-cycle process that uses relatively low- to moderate-temperature heat sources to generate electricity. These ORC systems are driven by a simple evaporation process and are entirely enclosed, which means they produce virtually no emissions,” Turboden said in a statement.