Oxford University had the highest aspirations for environmentally friendliness when it briefed developers about the design of its new flagship Oxford Earth Sciences Building.
As befits such an august institution, simply attaining BREEAM excellent rating was not enough: it decreed that the carbon footprint for heating and cooling had to be as small as possible.
A Ground Source Heat Pump system provided by GI Energy was selected as the mainstay of the heating and cooling system and the results were spectacular. Carbon savings exceeded expectations.
The CO2 emissions are 120 tonnes a year lower than anticipated and this was achieved despite the completed building behaving quite differently from the way it was expected to when plans were on the drawing board.
In practice it required double the amount of heating and, at peak times, up to ten times the level of cooling than was originally anticipated. Nevertheless the heating and cooling system coped admirably.
“The beauty of GSHP systems is that they extract heat from, and return it to, the ground, making them many times more efficient than conventional heating or cooling,” said Chris Davidson, Director of Development at GI Energy.
“At Oxford Earth Sciences performance data was collected over an entire year which showed that, for every kilowatt of power used, either 3.6 kilowatts of heating, or 4.7 kilowatts of cooling, was produced.
“The building used a fraction of the power that would have been required for conventional central heating or air conditioning, reducing bills and significantly reducing its carbon imprint.”
The site of Oxford Earth Sciences presented several challenges, not least the risk of flooding parts of Oxford if the GSHP system was not properly installed.
There was the danger underground pipework for the GSHP could hit a high pressure underground aquifer that lay directly beneath the building. The exact depth of the aquifer was not precisely known and had to be measured.
GI Energy worked closely with the Environment Agency to establish how deep it could safely drill down without hitting the aquifer. It was agreed that 63 boreholes could be sunk to a depth of 64 metres.
The second issue was the size of the site – even with sinking the boreholes vertically rather than horizontally it was still not large enough to support a GSHP system that could meet peak heating and cooling.
GI Energy took part in all the initial Energy assessments with Oxford University, contractor Laing O’Rourke and consultants Hoare Lea, after which it was decided to install a hybrid system, with back up from gas boilers and conventional cooling.
GI Energy’s brief was to provide as much heating and cooling as possible with a GSHP system, given the constraints of the site, providing conditioned water at 45°C and at 6°C for heating and cooling.
All of this was to be achieved while minimising carbon emissions across the whole heating and cooling system, including the gas boilers and electric chillers.
Significantly, and somewhat unusually, GI Energy is responsible for deciding when to switch on the back up boilers and air conditioners, and the carbon savings quoted are across the whole of the heating and cooling system.
A sophisticated computerised control unit constantly monitors the system and makes intelligent decisions. It can switch each of the three Ground Source Heat Pumps individually from heating to cooling and it can tell the building management system when to switch on the conventional back ups.
Monitoring throughout the year showed that the building required on average 100MWhr of heat, compared to the original estimate of 50MWhr; and the cooling load average 25-35MWhr per week, many times above the initial estimate of 5-10MWhr.
Steve Pearson, of Oxford Earth Sciences, said: “The system is providing much better savings than anticipated. While it is always reassuring to have a contract that delivers what is specified, there is a lot of value in GI Energy’s flexibility and ability to respond to changing demands.”
GI Energy is the market leader in the UK, having pioneered the use of Ground Source Heat Pumps in this country. Based in Coventry, UK, it has now installed more than 200MW of systems in a range of schools, hospitals, universities, commercial developments and housing associations. Landmark projects include One New Change in London and Europe’s largest lake loop, at Mansfield Hospital.
