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Why the time has come to pump it up

Following the government’s commitment to the Renewable Heat Incentive, there is growing interest in the potential use of heat pumps in a variety of projects, say industry suppliers.

PTS product group manager for renewables Ian Stares says the EST heat pump report has cast doubt over whether heat pumps can help the UK to deliver its sustainable domestic heat targets, but should be used as a guide to improvement.

The findings raised some concerns about system efficiency, with mid-range system efficiencies being between 2.3 and 2.5. In Germany, trials have shown that heat pumps can deliver a co-efficient of performance (COP) of 4.

The Department of Energy and Climate Change has recently published its roadmap to 2050, called Pathway Alpha, which envisages more than 20 million heat pumps in operation.

Mr Stares suggests that if the EST trial was started today, there would be a noticeable improvement as installation practices and technologies have moved on.

In Germany, heat pump technology and, crucially, its installation, is much further advanced than in the UK, which accounts for the higher standard of performance. This is the key point the EST makes: that a well-designed heat pump installation, correctly sized and installed, will offer significant savings.

With installation being such an important part of heat pump performance, installer training is key. Mr Stares points out that we need installers to be enrolling on accredited MCS training courses, while manufacturers must be encouraged to provide common metrics by which consumers and installers can judge the suitability of products for different applications. Merchants can also play a key role in providing independent advice.

The government’s decision to press ahead with the Renewable Heat Incentive should signal the start of a bull market for renewable technologies and heat pumps in particular.

Logical growth

Tony Gittings of FG Eurofred says renewable installations only account for 1 or 2 per cent of new heating and hot water installations in residential properties, but he fully accepts the logic for the growth of heat pumps.

They are, he emphasises, cleaner and can be more energy efficient than conventional systems, are kinder to the environment as a result and promise years of efficient use. Heat pumps - especially air-source - look as though they would make an excellent replacement for our over-dependence on gas central heating systems.

There are a lot of hurdles to be surmounted before the domestic heat pump marketplace takes on anything resembling a major force, adds Mr Gittings. And who will take over the installation on a mass-market scale?

Air conditioning contractors know all about heat pumps but not necessarily about installing them on a domestic system; heat pumps have fridge handling issues - plumbers are loathe to get involved; and AC contractors are not familiar with the structure, the names and the protocol of the domestic market.

All the signs point towards heat pump growth of anything from 10-20 per cent per year. While there are some contractors establishing themselves as specialists, it still isn’t a mass market - yet.

Mr Gittings’ view is that the industry has to rethink its approach, and that that should start with a dedicated heating division or company within organisations. They can then set up the necessary infrastructure; partner with the right manufacturer or contractor; and commit to training, after-sales service; breakdown response teams, etc.

Getting the right kit

There is a tendency to pigeon hole heat pumps within the 5 kW to 14 kW band of applications, says Garry Broadbent of ICS Heat Pump Technology. However, there is growing requirement to apply equipment suitable for more demanding applications.

High temperature heat pumps can simplify an application and allow the specifier/installer to move into different areas of the market. A typical example could be that of an oil boiler user who wishes to move onto a heat pump.

So, how does the installer select the appropriate heat pump? Firstly, the end-user must understand the implications of use in terms of allowing the installer/assessor to survey the heat loss of the property, but the installer must understand any limitations caused by the existing distribution system.

The existing radiator distribution system may cause the heat pump to run at too high a temperature for too long a period due to insufficient surface area to allow efficient heat exchange at a constant 45 deg C. If a radiator is deemed to be too small, there are two options:

  • The radiator can be exchanged for a larger surface area unit, or
  • A higher flow temperature of 55 deg C can be specified to accommodate a smaller radiator with a high temperature heat pump.

The second option will maintain efficiency and performance at an acceptable level throughout the heating season. This will also provide the ex-oil boiler user with cost savings, remove the need for fuel deliveries and achieve a significant carbon saving, says Mr Broadbent.

Purmo sales and marketing director Chris Edwards says that as enthusiasm for renewables gathers pace, the advantages of a good quality radiator should not be overlooked. Correctly sized and specified, it is still a highly energy-efficient heat emitter for use with sustainable heat sources and there are drawbacks in seeing only one solution to heat emission within the home.

If a ground-source heat pump is being used, it seems counter-intuitive to then use underfloor heating, losing some of the heat back into the floor, rather than emit it through a radiator directly into the room, says Mr Edwards.

There are many settings in which the best choice is still a radiator, especially as they can work efficiently at lower temperatures and do not need to be piping hot to be working well. This is largely a question of educating the end-user, which should not be difficult as running at lower temperatures means lower energy bills and a safer system.

Radiators are also ideal when an air-source heat pump is retrofitted to an existing property, he continues. New radiators may be needed, as it is crucial to ensure they are correctly sized and specified for lower temperature systems; but they are easier and less disruptive to install and much cheaper than retrofitting underfloor heating.

As long as they are used within a well-designed system, including thermostats and good controls, radiators are equally effective with almost any energy source. The big advantage for installers is that this is proven technology with which they are very familiar, says Mr Edwards.

Importance of returns

Vaillant marketing and technologies director John Collings says that spending by both organisations and private individuals is being carefully scrutinised and the industry must take a look at how solutions provide a good return on investment. As a result, many more heating engineers are seeking the specialised training they need to become competent in heat pump installation.

Ground-source types are proving their worth in many projects and will produce COPs of up to 4.5 depending on the flow temperatures achieved. However, they require a relatively high level of capital investment and so the installer has to thoroughly research a project to make sure the investment can be justified.

Air-to-air heat pump systems are ideally positioned for the mass market. The evolution of this version of the technology means almost any type of home in the UK can now benefit, says Mr Collings.

Local authorities recognise a system can be retrofitted to smaller houses, particularly all electric properties. In most of these, the heat pumps have replaced inefficient and poorly controlled night storage heaters so the savings are significant and the conditions for occupants much improved.

Many heating installers are now undertaking specialist training under the F-Gas Regulation that allows them to work with the refrigerant gases used in heat pumps. Diversification is an important strategy for installers adapting to a much-changed market following the downturn. Heat pumps are a good example of how heating businesses can evolve to survive and prosper in the market of the future, adds Mr Collings.

Latest developments

Daikin UK’s John Durbin agrees that today’s super-efficient heat pumps, with inverter control and variable refrigerant flow, offer all kinds of new possibilities, with the latest advances now capable of efficiencies of 9 or even 10.

They are an integral part of many air conditioning, heating, ventilation and refrigeration systems in all kinds of domestic and commercial applications, and higher capacity systems are capable of meeting exacting industrial heating and cooling requirements. However, for truly impressive performance, inverter technology is key, he argues.

Inverters adjust the power used to suit the actual requirement and will gradually increase capacity based on demand to cool or heat the room. Unlike standard on/off systems, an air conditioning system with an inverter continuously adjusts its cooling and heating output to suit the temperature in the room. It will shorten system start-up time, so the required room temperature is reached more quickly and temperature fluctuations are avoided.

An inverter continually monitors and adjusts ambient temperature, so avoids cycling of the compressor, avoiding voltage peaks, reducing energy consumption by between 30 and 70 per cent compared with a traditional system.

Manufacturers have continued to hone inverter technologies, from those designed to maximise comfort in commercial environments to the latest super inverter models. Forthcoming EuP legislation will require air conditioning equipment to demonstrate seasonal efficiency ratings, rather than the nominal performance ratings previously used.

There’s no doubt that the latest advances in inverter control and seasonal efficiencies will continue to deliver ever higher energy efficiencies to reduce the environmental impact of air conditioning systems.

Cylindrical benefits

Gledhill Building Products chief executive Mark Foster says that independent research shows the importance of using a specially designed heat pump cylinder to maximise the benefits of heat pump technology. In some cases the technology fails to live up to its potential, which could affect perceptions and slow take-up.

Some systems are not delivering the anticipated levels of performance as they are being installed with conventional cylinders, which take longer to heat up from cold and require higher energy levels than a cylinder that is able to recharge on a continuous cycle.

If a heat pump is installed with a specialist cylinder it can really deliver the manufacturer’s promised efficiency levels, argues Mr Foster. Heat pump distributor Freedom Heat Pumps carried out a comparative test using the an air-to-water heat pump system in combination with a heat pump cylinder kit alongside a market-leading split system using the manufacturer’s own cylinder.

The test compared how long each system took to recover the cylinder temperature from cold. The results showed the dedicated system took 40 minutes to reach 500 deg C, while the split system took twice as long.

The test also measured the average heat input into the water from the heat pump. The average heat input for the dedicated system was 7.2 kW, while for the conventional cylinder it was just 2.6 kW, Mr Foster notes.

In at the deep end

Calorex sales director Tony Barnes explains the growing pressure on councils and leisure centres to efficiently heat swimming pools.

They normally use heat exchangers linked to boilers, but water evaporates from the surface at the equivalent of a bath of water every two hours.

This evaporation contains most of the heat input, he says. Pool operators are increasingly looking at heat pumps for an economical and environmentally-friendly solution.

By recovering and recycling energy, heat pumps need less input and can reduce running costs and carbon emissions by up to 70 per cent. They also cut maintenance costs by reducing humidity damage to the building.

All sizes of pool now have a wide range of solutions available, built especially for this environment, with all components chosen to provide maximum efficiency and reliability, minimum maintenance and a long lifespan.

Using a heat pump with thermodynamic heat recovery technology can save over 250 tonnes of CO2 emissions each year on a typical 25 m pool. Other renewable forms of heating do not produce the same high-level performance, Mr Barnes argues.

Solar pool heating panels collect heat from the sun and have no operating costs, but the volume of solar collectors required is neither practical or economical.

Against this, the benefits of using heat pump and dehumidifiers are huge. With the added assurance of MCS certified products and installers, it’s a win-win situation, Mr Barnes suggests.