Ground Source Heat Pumps


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What are ground source heat pumps?


At a very basic level, heat pumps can be thought of a pumps which transfer heat from one place to another, just as a water pump transfers water from one place to another. This can be up-gradient when in heating mode (transferring heat energy from a lower temperature source such as the ground, a river or a lake, to a warmer building), or down-gradient when in cooling mode (pumping waste heat from a building to the ground in the summer).


Because the capital cost of ground source heat pump (GSHP) systems per installed kW decreases as the system size increases, this makes GSHP systems attractive to major commercial and industrial developments, and larger private residential properties. With an efficiency of 350% or more in heating mode, they are cheaper to run than conventional heating and cooling systems which use grid electricity, gas or oil, and can provide considerable cost and carbon savings over the lifetime of the system. In addition to this, the UK government is currently providing a subsidy for eligible GSHP systems in the form of the Renewable Heat Incentive (RHI).

 

  Water-Source-Heat-pumps Vertical-GSHP

 

There are two main types of GSHP: closed-loop and open-loop:

  • closed-loop systems (left-hand diagram): a heat transfer fluid circulates within a sealed pipe buried in the ground; the heat transfer fluid does not mix with groundwater. The sealed pipe can be placed in vertical bores, in horizontal trenches, or within a lake.
  • open-loop systems (right-hand diagram): water is abstracted from the ground via a borehole, passed through the heat pump, and discharged at a modified temperature. Water can also be abstracted from a river or lake.

Why involve LWRC?


GSHP systems have been around for many years now, so we know from experience that they can provide heating (and cooling) for a reduced running cost and carbon cost in comparison with more conventional forms of heating. However, in order to realise these potential benefits, careful design and installation by competent engineers and contractors is paramount. At LWRC we have staff experienced in all aspects of GSHP systems and we can manage a GSHP project from concept to commissioning. Our operations are certified in accordance with the international quality management standard ISO 9001:

  • Feasibility study: a ground source heat pump is not the right option for all situations. Many factors need to be considered, including ground temperature, hydrological and hydrogeological conditions, potential borehole yield, the heating and cooling demand of the building (known as the building 'load'), land availability for installation, licensing, construction, capital costs, running costs and potential RHI payments. We can look at your requirements and give you carefully reasoned advice on the type of heat pump system that would be suitable for your project, including an outline estimate of costs. For a relatively small initial outlay this will enable you to make an informed decision on whether to take the project to the next stage.

  • Design: we use industy-leading software such as Ground Loop Designer (GLD) for closed-loop system design, and FEFLOW for open-loop system design. With decades of experience in hydrological and hydrogeological investigations we have a deep understanding of ground conditions and groundwater flow which are key elements to designing a successful GSHP system. As part of the full design process, one or more trial boreholes may be need to assess well yield, ascertain aquifer characteristics and undertake thermal response testing; this depends on the size and type of GSHP system.

 

  • Financials and risk management: we can provide an estimate of system costings and running costs at an early stage to give you a clear idea of the payback period of your proposed GSHP scheme. If you are replacing a conventional heating/cooling system in an existing building we can estimate the savings you will make with the proposed GSHP scheme; the more detail you can provide on your current running costs and building loads, the more accurate this estimate will be. A spend profile and principal risks to the project are identified at an early stage so you can be clear how much cost is likely to be incurred before the stage of the project is reached where these risks are mitigated.

 

  • Licensing: depending on the size and type of GSHP system you may need an abstraction licence, consent to investigate groundwater, flood defence consent, environmental permit and/or planning permission. Over the years we have conducted hundreds of licensing discussions with authorities such as the Environment Agency and local councils resulting in favourable licensing decisions for our clients. These discussions should be opened at a early stage of the project.

 

  • Installation, testing and commissioning: we work with a range of subcontractors at installation stage and we can help you manage the tendering process and supervise the drilling, installation and testing phase. LWRC staff have many years practical experience in the design, supervision of construction and testing of boreholes, experience which is critical to a successful project outcome.

 

 LWRC experience

 

  • LWRC have designed and installed GSHP systems at large private residences across the UK.

 

  • We have undertaken detailed feasibility studies for a number of projects in London, both open- and closed-loop, where the proliferation of ground source heat pump systems over recent years means that very careful analysis is needed to ensure any proposed GSHP system is sustainable in the context of existing schemes.

 

  • We have designed closed-loop "loop-in-pile" systems where the closed-loop pipe is installed in the building piles as the building is constructed.

 

  • We have designed and installed open-loop systems using water abstracted from rivers (so called water-source heat pump systems).

 

  • We are currently undertaking a feasibility study for a ground source heat pump scheme which will use water pumped from flooded mine workings in the north-east of England.

 

We are members of the Ground Source Heat Pump Association.

 

For additional information on modelling click here

 

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