Stewart Purchase, chief executive of Viessmann UK, discusses the increasing use of heat pumps in the UK and how technology is helping to move this exotic heat source into the mainstream arena
WHEN I tell my European colleagues that using ground source heat pumps (GSHP) is regarded in the UK as exotic, a bit of a fringe activity, they raise their eyebrows.
In Europe heat pumps are an important part of the heating market; in Sweden for example their sales exceed oil -fired boilers.
This year UK sales of heat pumps for heating systems will be of the order of a thousand or more, a figure that points to a market now set for steady growth.
We are seeing installations in schools, homes, businesses and public sector buildings which confirm that clients at least, now see heat pumps as a perfectly sensible heating option.
Why this change of attitude? Three factors have coincided:
· Geothermal and ground boring expertise is now combined with the heating system design knowledge relevant to heat pumps;
· Reliable, economically priced heat pumps, designed for UK systems and design practice are available;
· A focus on using sustainable energy wherever possible, especially in newly designed buildings.
All of a piece?
The first two factors here are the key ones, especially as far as the system designer and the contractor are concerned.
Heat pumps of course are in wide use in air conditioning and heat recovery but using them as the main source of heating energy, as an alternative to a boiler, has been seen as too complex.
This is because, unlike boilers, the heating system, the building and the heat pump and its energy source, usually the ground, have to be considered as all of a piece.
Until recently the client faced the terrifying task of reconciling the differing requirements of the heat requirement of the building, the heating system and the geothermal input, with information fired at him from three or more specialists.
On top of that equipment available has been limited in application.
With a maximum water flow of 50°C, systems almost had to be underfloor.
Nothing wrong with that but it excluded GSHP's from retrofit to existing radiator circuits and meant the DHW had to have a back-up heater; usually an immersion heater.
Infrastructure the key
Now both these drawbacks to the market have been overcome. For example my company has a relationship with Geoscience, a specialised geothermal advisor and contractor, so that the solution to the ground source+heating equipment+heating systems+building equation can be presented clearly to the client. Siting the ground heat source is easier too. The Slinky system gives a close to the surface installation of simple-to-install pipework.
New equipment, like the Viessmann Vitocal 200 and 350, allow water flow temperatures of up to 65°C, giving them the ability to serve both DHW and radiator circuits if required. Reliability is a key issue. We would expect a ground source heat pump to have a service life of around 20 years, outlasting oil boilers and burners and over that time heat pumps need no routine maintenance.
Heat pump systems in a box
In addition, heat pump systems are being simplified. Until now heat pump systems had to be assembled on a one off basis. This meant a great deal of time and the trial and error approach to getting the system operating correctly. Now with the launch of the Viessmann Vitocal 343, we have a heat pump system in a box. A package combining a heat pump, controls, solar heating connections and a storage cylinder, all in a case the size of a domestic freezer.
Ground source heat pumps need not just be heating machines. When the Royal Society for the Protection of Birds (RSPB) planned a new visitor centre on the edge of the marshes at Rainham it is no surprise that sustainability and a low carbon footprint were high on their wish list.
The new centre is built on 360 hectares of marshland running down to the Thames estuary, a site used for many years by the MOD. The building includes a reception area, café, shop and education space, giving views across the reserve for the anticipated 140,000 visitors a year.
Heating for the centre is by a Viessmann 28kW Vitocal ground source heat pump drawing its heat energy from six, 80m deep, bore holes. The heating system within the centre is underfloor, giving maximum floor space and running at the ideal temperature (35ºC) for the heat pump. During the summer the underfloor system circulates ground water, without it being raised in temperature by the heat pump, so that it adds to the cooling of the building but does not require energy input for refrigeration.
With the design, equipment and installation infrastucture in place heat pumps are moving into the main stream of system choice. Certainly there are good long term environmental benefits of a machine drawing 75% to 80% of its output from the soil under our feet.
In money terms GSHPs are more expensive to install than conventional boiler systems but their running costs compared with oil and LPG make them a sound investment over their operating life. That's at today's prices.
If the Energy White Paper is right the picture during the next 10 to 20 years makes them even more applicable.
Viessmann offers specialised training on heat pump technology and installation T: 01952 675000