GROUND SOURCE HEAT PUMPS CASE STUDY
L
ow-carbon technologies such as ground-source heat pumps have the potential to make a real dent in the UK’s carbon reduction targets.
However, if these systems are to fulfil that potential, the industry’s attitude to their specification, commissioning and operation needs to change. If carbon-saving technologies are simply
‘fitted and forgotten’, the chances are they will not perform as expected, and the result
will be more ‘turned off and forgotten’. Experience from one prestigious university project in Oxford shows the importance of continued involvement from the design and construction team during the post- occupancy stage – and the significant rewards that can be gained through perseverance.
A groundbreaking system The Department of Earth Sciences at the University of Oxford (OUES) is a leading centre for geological research designed by Wilkinson Eyre Architects with Hoare Lea as mechanical and electrical consultant. The development, which had a £29.5m construction cost, comprises a 7,100m2 building with a five-storey office and teaching wing and a four-storey specialist laboratory wing, linked by an atrium entrance. In some of the laboratories, environmental control is of critical importance to the experiments conducted. The building also houses a server room, and a number of hub rooms, where 24-hour cooling is required. Energy efficiency was a key part of
the brief and a 20% renewable energy contribution was a planning requirement of Oxford City Council. Early in the design, Hoare Lea carried out a comparison of low and zero carbon (LZC) technologies, and concluded that a ground-source energy system (GSES) was the most appropriate solution. OUES is one of the first laboratory buildings in the UK to use a GSES and the principles of the technology fitted neatly with the climate change and geological research interests of the university department. The financial payback of the system
– at current energy prices – was longer than would normally be considered viable, but became more attractive when fuel cost inflation was factored in. Also, Oxford University was attracted by the predicted carbon savings and instructed the designers to push beyond planning requirements and maximise
www.cibsejournal.com August 2013 CIBSE Journal 37
CONTROLLING TO SAVE CARBON
When installing the ground loop, the designers were limited to the footprint of the building, writes Roger Macklin of GI Energy. This constrained the GSES’s total energy exchange capacity and peak output, so conventional heating and cooling systems were installed as part of the original design. This led to the development of a unique control philosophy in which the GSES could choose whether to provide heating or cooling on the basis of optimising carbon savings, rather than to satisfy a specific load.
The overall conditioning is, therefore, led by the GSES control system, which selects the technology to use. GI Energy modelled the performance of the selected heat pumps to identify, for a given ground-loop temperature, how carbon savings would be maximised, taking into account the anticipated performance of the conventional systems. Further development of the control system added stability and incorporated detailed hourly performance monitoring, observable from GI Energy’s office.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60