There has been a great deal of concern over the capital costs for Ground Source Heat Pump (GSHP) systems. Due to the relatively linear cost relationship in loop installation, over-sizing carries a much higher penalty than is the case with conventional equipment. The extent to which capital cost can be reduced depends upon the accuracy with which the heating and cooling loop length is determined.
Loop design is a complex issue, but a few key points warrant special attention. Among these are building load, local climate, site and characterization. There are no generally-applicable rules-of-thumb that cover the diverse range of buildings and ground heat exchanger scenarios.
The GRC Seren H-GoLD tool is a free VB based software tool, developed to familiarise small and medium enterprises with design parameters involved in estimating the ground loop length of GSHP systems. SMEs could take advantage of the opportunities to gain valuable knowledge of how to optimise designs.
Software can also be used for the preliminary assessment of required length which can be used for further detailed study of GSHP systems. The tool provides access to the key input parameters required to size a ground loop, whilst shielding the end user from the complexity.
Estimation of the required length for ground loops is calculated within H-GoLD, drawing on an analytical solution based on the line source equation which is largely adapted from IGSHPA (1988), and Kavanaugh, and Rafferty (1997). The implementation of this analytical approach has been verified by the software development team.
The equation used in this computational code takes into account the average heating load of the building and the local climate variations (to calculate the ground temperature), heat pump characteristics, and soil and pipe thermal parameters.
Seren H-GoLD has also included a simple cost/carbon calculator in its utilities. This estimates the potential benefit of using a GSH installation versus some more conventional methods of heating. The Cost/Carbon calculator takes in simple operational parameters and provides an estimate on both the running costs and the CO2 emissions of a GSHP system.
By developing this easy-to-use tool, it is hoped that the GRC’s Seren project will be of direct benefit to Welsh SMEs motivated to get into the ground source heat pump industry.
To request a copy of the GRC Seren H-GoLD or to request further information, please contact:
The GRC, (Seren project), School of Engineering,
Cardiff University, The Queen’s Buildings,
The Parade, Newport Road,
Cardiff, CF24 3AA
Tel: +44 (0) 29 2087 0497