Green energy was a big part of the buzz emanating from the British Science Festival this year. Geothermal heat and sewage-powered clean energy were both on the sustainable agenda being discussed in Newcastle. Researchers were busy unveiling important renewable energy projects underway in north east universities and industry.
First up was the revelation that an exciting partnership between the universities of Newcastle, Durham and Glasgow, and the British Geological Survey, is targeting deep geothermal energy to meet the UK’s entire heating demand and part of its power generation. BritGeothermal aims to create commercial plants as part of the country’s future energy mix.
Digging for heat
Despite a lack of volcanic activity the UK still has capacity to tap geothermal energy. There has been a heating operation in Southampton for the past 25 years and the country’s geothermal gradient – the rate at which the Earth’s temperature increases with depth – averages out at 26°C per km. BritGeothermal aims to drill wells to extract heat from groundwater at depths of one kilometre or more, for industrial and domestic use.
There is potential to provide a massive 100GW of heat that could theoretically satisfy the entire space heating demand in the UK, saving carbon dioxide emissions of around 120 million tonnes.
Science Central borehole
Newcastle’s Science Central is already the site of the deepest geothermal borehole in nearly 30 years, extending 1,800m. Researchers say the temperatures recorded on site already surpass the UK average (at 36°C per km) and they are looking at other onshore sedimentary basins at depths of around two kilometres.
Armed with knowledge about these sites the consortium may develop power plant technologies to be used on offshore oil rigs, where water from wells could meet some of the power demand for the platform. Charlotte Adams, research manager for BritGeothermal at Durham University, is hopeful that “lowering the temperature at which power can be produced could help to improve the economic case for deep geothermal energy in the UK.”
WASTE WATER TREATMENT
Flush with success
First trials of a microbial electrolysis cell (MEC) that produces hydrogen have been carried out at a sewage waste water treatment works on Tyneside. Researchers at Northumbrian Water and the University of Newcastle have harnessed billions of naturally occurring microbes to produce hydrogen gas and improve water treatment at the same time.
Two suggested uses for the hydrogen include fuel for use in hybrid vehicles or harvesting to make higher value organic chemicals. Everything is powered simply using raw untreated waste water at normal temperatures.
Tom Curtis, professor of biological engineering at Newcastle, says: “Most anaerobic digesters require a high-energy, concentrated food source and heat to work properly which means the water has to be removed first and this is an energy-expensive process. What we have developed is a system that feeds on the waste as it arrives at the plant – the whole lot goes in and the microbes do all the hard work.”
Northumbrian Water has built £70 million award-winning advanced anaerobic digestion plants at Howdon on Tyneside and at Bran Sands on Teesside. Sludge from 2.6 million customers’ waste water is treated and produces gas to be turned into electricity.
Maxine Mayhew, commercial director for Northumbrian Water, said: “Currently we are harvesting the methane released by bacteria as they digest the sludge which is then used in gas engines to create electricity. Now, in another innovative move to maximise the energy production, we are working to upgrade and purify the biogas so it can be directly injected into the gas grid.
“As industry pioneers of generating power from waste water we now look to our work with Newcastle University to take this energy production to another level and develop production of hydrogen – the clean fuel of the future.”
Greening the globe
Two per cent of all the UK’s electricity generation is used to treat waste water, so self-generating systems will be vital in boosting the low carbon economy. One of the team’s MEC systems is being installed at a waste water treatment works in Sedgefield, County Durham.
Professor Curtis commented: “I think if there’s one thing we all realise it’s that there’s no magic bullet – no single source of sustainable energy that is going to save the world. Most importantly, wasting energy in waste water treatment is increasingly a global problem. As the [emerging economies] BRICs urbanise and adopt our energy intensive treatment technologies in a world of rising energy costs we are all going to be in the same boat.”
Energy stored in UK waste water is equivalent to five billion barrels of oil a year.