Geothermal energy — With the construction industry on the lookout for sustainable energy sources, geothermal energy is increasingly becoming the preferred option on projects

With the need to comply with regulations such as Part L and PPS22, the construction industry is always on the lookout for sustainable energy sources. One of them, geothermal energy, is increasingly in demand and is being used in a new form by being incorporated into foundation piles.

Martin McLaughlin, senior engineer at engineering consultant Faber Maunsell, is convinced that this use of geothermal technology will soon become the accepted norm. He says: “It will be the standard for the future and the most financially viable option for all buildings.”

He explains that in London in particular, considering the mayor’s emphasis on energy renewables, geothermal technology can have a positive effect on a planning decision. He adds: “Teams using a 100% geothermal solution can experience a higher net growth on the project because the need for other energy-efficient devices is reduced within the building.”

There are some practical considerations when laying conventional pipes to collect the energy. The ground has to be dug up specially. Foundation-bearing piles are therefore used both to support a building and as energy piles to provide cooling and heating. Either the concrete elements within the ground are used to house circuits made from plastic piping or specially constructed grouted boreholes are used. The pipes are used to circulate a heat transfer medium, normally water with anti-freeze, which transports the ground temperature to the central control system for the building services.

Technological hurdles

Incorporating pipes within piles is growing in popularity as the technology becomes easier to use. But there are still some hurdles to overcome to make geothermal energy the preferred option on a project. Tony Suckling, technical development manager at Stent, a geothermal technology provider, says that the architect, structural engineer, geotechnical engineer, geothermal engineers and building services engineers should all be included right from the beginning of a project because of the complexity of the planning and engineering processes necessary for ground storage systems. He says: “This is the reason why this technology has yet to really take off here in the UK. Geothermal energy and energy piles are introduced onto the project agenda, but then removed once the team realises that the building design is too far advanced to accommodate the system.”

Geothermal technology will be the standard for the future and the most financially viable option for all buildings

Martin McLaughlin, Faber Maunsell

At the moment geothermal energy is more expensive to install than other energy-efficiency technologies but environmentally conscious clients can experience a payback period that ranges from 10 to 20 years depending on the size and cost of the project.

In London Faber Maunsell is working on six projects that use geothermal energy in the foundation piles of the building. One of them, a £16m sixth-form centre for Lambeth College in South London, will cater for more than 1100 people and is expected to produce about 24% of renewable energy. The 6669 m2 education centre has been designed with a closed loop geothermal system integrated into the piles of the building to serve all the heating and cooling needs of the building. This equates to a maximum duty of 430 kW. For this scheme Faber Maunsell estimates that payback time will be up to 13 years.

Part L gives geothermal a boost

Meanwhile Stent’s Suckling says his company has experienced an increased interest in integrating geothermal energy in the foundation piles. Since Stent’s first British project in 2002, it had only worked on five projects. But since Part L was passed the company has been approached to work on 10 projects and is now devising the integrated geothermal energy system of a library project in Oxford and an art gallery in Chichester.

Construction consultancy McBains Cooper has designed a closed loop system integrated within the building piles for a £30m police headquarters for Kent Police. And Faber Maunsell is working on a £64m speculative office development for Development Securities at Paddington Central in London.

Ian Campbell, associate director at Faber Maunsell, says the client has been the driver for this choice: “Development Securities has embraced the inclusion of renewable technologies on the project since its inception in 2000 and will continue to do so for future phases.” The 23,769 m2 scheme is in the second phase and has been designed with a closed loop geothermal system integrated into the rotary piles.