Watercourse heat collection

Water-source heat pump systems are relatively rare, partly because not many properties are next to or close to a water course, but also because a lot of heat pump installers shy away from the added complexity of obtaining the necessary consents and the difficulty of designing and building a heat collection system in a watery environment.

This is where Renewables First can help – we are experts at working in water from our many years of hydropower experience and water intake expertise from our sister company GoFlo Screens Ltd.  We can design your open-loop (water abstraction based) or closed-loop (heat collector based) heat collection system, and are expert in obtaining all the necessary consents (abstraction, discharge, FRAP, planning, listed building etc.) that are likely to be required when working in water.  We have even designed our own heat collectors (see www.FireFlo.co.uk) for closed-loop systems.

If you are a heat pump installer or main contractor and are happy with designing and installing the heat pump and heat distribution system, but aren’t as confident on the heat collection system – please get in touch.  Renewables First can design it, get the relevant consents and install the heat collection system.  Our responsibility would end with the delivery of heated brine from the watercourse that you could connect to your heat exchanger or heat pump.  Equally, we can specify and supply the heat pump as well if that is required.  The different options and requirements are discussed below.

Closed-loop systems

Domestic and smaller commercial systems (typically up to about 150 kW) can use closed-loop heat collection systems, such as FireFlo heat collectors.  Larger installations could be done if there is the physical space to accommodate the collectors in the water course.  Closed-loop systems have the following advantages over the equivalent open-loop system:

• Normally cheaper
• Do not require an abstraction or discharge consent from the water regulator (Environment Agency / Natural Resources Wales / Scottish Environmental Protection Agency)
• Have no moving parts or active control system, reducing maintenance and increasing reliability
• No problems with bio-fouling the internals of the primary heat exchanger, which can be an issue with open-loop systems
• Less equipment and structures to be seen around the watercourse (particularly above water)
• No requirement for eel or fish screening

A bed mounted, vertical array of FireFlo collectors

A wall-mounted 3-panel assembly being installed (part of a larger system)

Not having to obtain an abstraction licence and discharge consent is a significant advantage, because it saves a lot of time (typically 4 months) spent obtaining the consents, but also saves on the applications fees that could be over £10k for commercial systems, and still approaching £5k for relatively modest domestic-scale systems, plus the cost of the time to actually make the applications.  There are also annual water-use fees to pay (typical a £200/year).

A closed-loop system, if on a ‘main river’, would also need a ‘Flood Risk Activity Permit (FRAP)’ from the Environment Agency or the equivalent in Wales and Scotland to consent the proposed ‘works in the river’, which would cost around £1,500 – £3,000 to obtain.

Note that closed-loop heat collectors should not be installed in locations that could experience extremely high flow velocities during flood events, particularly if such flows would also contain large entrained debris (like trees, branches or boulders).  They are very tough and can survive a lot of punishment, but there are limits.  Mountain streams with large boulder-beds are a particular problem if the boulders start to move during flood flows.

Open-loop (abstraction-based) systems

Larger systems (typically above 150 kW) can use an open-loop system where the water is pumped out of the water course, through a primary heat exchanger, then returned back to the river.  Such systems commonly use a submersible pump(s) to abstract the water, mounted onto some form of framework which normally incorporates guide rails for removing the pump(s) and access equipment.  The discharged water can be dropped into the water course from above, or discharged via an underwater discharge box – the former would normally be preferred, but the water regulator sometimes insists on the latter.

Open-loop abstraction and discharge system (three submersible pumps and one discharge box) on edge of river bank

While the pumps for such systems can be very compact, once the guide rails and access provisions are incorporated, and the discharge system, the structure that has to be installed into the watercourse can become quite large.  The design is critical if the overall system is going to be relatively easy to maintain in the future and to make sure it meets the various fisheries and eel screening requirements.

What next?

If you have a need for heat collection for your water-source heat pump, and don’t know where to start, we can help.  The normal process is:
 

• Feasibility study
  This includes a project review to understand the flow and pressure requirements of your heat pump system and site survey to understand the site layout and complete a survey of the intake and discharge areas.  We would then specify the best system to achieve your needs and document the results in a report including budget quotes for the design, consenting and construction stages.
• Outline design and consent applications
  This is the design in sufficient detail to support the consent applications, then making the abstraction licence, discharge consent, FRAP and (if needed) planning and/or listed building consent applications and managing these through the process until conclusion.
• Detailed (construction) design
  This is the fully-detailed design in sufficient detail to construct the system.
• Construction and installation

If this is of interest, please get in touch via our Enquiry Form for an initial discussion and quote for the first step, the feasibility study.