Heat pumps will play an increasingly important role in our strategy for reducing climate change, says Mark Richards, technical manager for Vaillant’s Applied Systems air conditioning division.
THE all-year round benefits of heat pump air conditioning are now widely recognised and the increased focus on climate change mitigation has given a further boost to the technology.

The European Commision called for a new ‘industrial revolution’ when it unveiled its latest set of proposals on energy and climate issues in January. This called for greater investment in renewable energy, better use of existing resources and less dependence on the so-called ‘old fuels’. This point was reinforced in the same month when Russia, once again, cut off oil supplies to its European neighbours at the height of winter.

The Commission has predicted that EU energy imports would rise from 50% of the total current consumption to 65% by 2030, putting us increasingly at the mercy of potentially unpredictable sources. To counter this, the Commission wants all developed countries to cut their energy consumption by 30% by 2020.

At the same time, many air conditioning distributors and contractors report that a huge proportion of the new air conditioning systems sold in the UK last summer were heat pump versions. As well as being able to provide heating in winter and cooling in summer, these reverse cycle systems on average deliver COPs of at least 3 to 1 so potentially cutting users’ heating energy bills by up to a third.

The use of inverter-driven compressors further improves the efficiency by closely matching the running speeds to demand so avoiding unnecessary energy consumption when cooling/heating demand is low. Inverter driven reverse cycle systems also provide better comfort conditions as they reach target temperatures more quickly than conventional systems and are better able to maintain set temperatures over extended periods.

Existing systems

Traditionally, of course, most UK buildings already have wet central heating systems or electric heating in place. This means there is now an important balance to be struck if designers are considering retrofitting air conditioning to these properties.

In an ideal world, we would be able to start with a blank sheet of paper allowing the building services engineer to design a combined and fully integrated reverse cycle heating and cooling solution to provide all of the building’s comfort needs – including air filtration – from a single source.

If a heating system is already in place, however, the designer has to take into account the cost and disruption involved in a full replacement as well as the embedded energy penalty of scrapping existing systems.

However, the long-term running cost benefits of providing highly energy-efficient heating and cooling from a single source provide a persuasive case for this type of replacement and the growing environmental prerogative is reinforcing this thinking.

Integrated systems can also help building services engineers meet the requirements of Part L of the Building Regulations by demonstrating that they have taken a holistic approach to reducing the carbon footprint of a building.

Even more persuasive in the current political and legislative climate is the combination of reverse cycle heating and cooling with a renewable energy source. Geothermal (ground source) heat pumps are proving increasingly popular and work particularly well in conjunction with low temperature heating systems such as underfloor. These can deliver COPs as high as 5 to 1, although this has to be balanced against the end user’s initial capital outlay, which will be higher than with a conventional system.

Air-to-air and air-to-water heat pumps are also expected to enjoy healthy market growth during the coming two to three years because they are easier to apply to existing homes and commercial premises, as they neither require a borehole or a large area to bury pipework.

Return on investment

“Rising energy prices combined with tighter planning regulations are driving this market,” says David Frise, chairman of the HVCA’s Sustainability Issues Group. “Almost every enquiry we get now as a contractor has some element of sustainability,” he says. “And if the builder doesn’t want it, you can be sure the planner will.”

No one is better placed to deliver the demands placed on clients by ever more onerous climate change legislation than specialist engineering firms, according to Mr Frise, although he says it is still a battle to explain the financial benefits to end users.

“We are trying to get away from this straight ‘payback’ argument and get people to look at the return on investment instead – that is a far more sensible way of calculating the financial benefits,” he explains. “If you have a unit giving a COP of 4 to 1, then the more the energy prices go up the better your investment looks.

“It is still a fledgling industry, but the momentum is pretty much unstoppable now,” says Mr Frise. “More people are only receiving planning permission if they include some renewables in their design and heat pumps tick a lot of the relevant boxes.”

Sizing is everything

To ensure the systems perform at their optimum and, therefore, deliver the best energy performance, design engineers must ensure they get their sizing calculations right. Detailed analysis of heat loads should be carried out and they should seek to express the outputs in kilowatts rather than horsepower, which tends to refer to the size of the motor rather than the real output of the unit. Oversized units have been a major weakness in far too many building services installations over the years creating a serious legacy of capital and running cost penalties for end users.

However, the momentum created by the climate change agenda towards better planned and integrated solutions such as single source heating and cooling systems is promoting a far more professional approach across the industry. There is growing demand from end users for higher quality designs that meet their environmental obligations, which bodes well for suppliers and designers of reverse cycle heat pump air conditioning.