An eco-energy entrepreneur who played a leading role in the development of Sheffield’s district heating scheme is hoping to help the city build on its reputation as an innovative and green place to be.
Stephen Brooks was development manager for Sheffield Heat and Power in the mid 1990s, when pipes were first laid under the city’s streets to use heat from the Bernard Road waste incinerator to heat homes and city centre businesses.
The Sheffield City Council backed initiative always had the ambition to build its own combined heat and power plant, generating electricity and feeding the heat left over into the district heating network.
That never came to be, but now, as a director of UYE (UK), Stephen Brooks has launched plans to build an innovative CHP power plant at Halfway that will generate electricity for the grid and heat for the nearby Westfield Estate by burning waste wood.
UYE (UK) isn’t the only company planning to build a wood burning power plant in Sheffield.
E.ON has started work on a 30MW power station at Blackburn Meadows, but, beyond burning recycled waste wood and a potential start date in 2014, there is little resemblance between the two.
While E.ON says its power station has the potential to become a CHP district heating plant UYE (UK)’s will have CHP capabilities from day one. It will also be smaller – about a 10th of the size – and is based on significantly different technology, using oil, rather than steam, to turn the turbines which generate the electricity.
While traditional steam technology might work for a larger scale power station on a more isolated site, it has its drawbacks for a smaller scale operation – particularly when the site you have chosen is on an industrial estate.
So, UYE (UK) has opted to use the Organic Rankine Cycle – named after the Scottish engineer and physicist William John Macquorn Rankine, who played a key role in the early development of the science of thermodynamics.
“We looked at steam, but it has disadvantages,” says Stephen Brooks. “It’s noisy, you need chemicals for water softening and it generally uses enormous temperatures and pressures.
“We will operate at significantly lower temperatures – 215C to 320C – compared with up to 1,400C for steam.”
Although they travel more slowly than molecules of steam, molecules of oil are bigger and heavier, so they carry more energy and can still turn the turbine blades to generate electricity.
The system is sealed and the oil only needs changing every three years.
High temperature, high pressure steam is an aggressive medium, which makes steam-driven power plants more prone to break down and parts need replacing on a more regular basis.
Stephen Brooks reckons that while a steam plant operates 75 per cent of the time, you can get 90 per cent out of an ORC plant and you don’t have to renew the blades on the turbines every three to five years, as you have to with steam.
“It (ORC) is very clean technology. You don’t even need ear defenders when you go round the plant and it is so quiet you can hear the valves operating,” says Mr Brooks.
It is also a proven technology, with plants operating in eco-conscious Austria and Germany, as well as Italy for many years.