A Ground Source Heat Pump transfers heat from the ground into buildings
The Energy Saving Trust and Centre for Sustainable Energy have lots of information regarding ground source heat pumps:
Case study: Gamlingay Eco Hub.
The award-winning Gamlingay Eco Hub opened in 2012 following an extensive refurbishment by the parish council of a former community building, It is an exemplar project with all energy needs supplied by on-site renewable technologies. A ground source heat pump and solar thermal panels provide heat for space and water heating and solar photovoltaic panels generate all the electricity needed by the building and more, making it net carbon positive in operation. You can find out more about the project on the Gamlingay website.