Cameron Holroyd, commercial director of Kingspan Hot Water Systems, discusses how to get the most out of air source heat pumps.
The unveiling of Feed-in Tariffs and Renewable Heat Incentive proposals mean households that install generating technologies such as solar thermal, heat pumps and combined heat and power units will be guaranteed payments for the low carbon technology.

The scheme is expected to set in motion the mass deployment of sustainable heating systems and deliver 12 per cent of the EU renewable energy target of 15 per cent by 2020. While the scheme is essential if home owners are to be encouraged to consider renewable energy sources as a main stream option, it will also provide a long term framework to stimulate the renewable industry.

However the onus is on manufacturers and installers to ensure the replacement technology performs to its optimum level. Take for instance air source heat pumps, a well-established technology which can be used in virtually any domestic or commercial application. Performance levels can be impaired by not achieving maximum efficiency in heat transfer and heat storage but by installing a purpose-designed cylinder installers can achieve high flow rates and improve heat transfer times, while also extending the life of the heat pump and helping lower the running cost for homeowners.

Cheaper than ground source, air source heat pumps are compact and easy to install. The latest generation of air source heat pumps can extract around 75 per cent of usable heating energy from the environment and supply up to 100 per cent of space heating and domestic hot water to UK homes. They are designed for Northern European climates, providing heat in winter no matter what the outside temperature is. Unlike ground source heat pumps there is no ground loop to install and they are virtually maintenance free. The average household can save around £870 in heating bills and almost six tonnes of CO₂ a year. In fact the market is worth an estimated £57 million a year with the retro fit market growing the most rapidly.

Specifying and installing air source heat pumps is certainly within the capability of a competent MCS (Microgeneration Certification Scheme) installer but unless supplied with a quality cylinder, performance levels can be significantly reduced. To achieve maximum efficiency the best advice is to ensure the complete package is custom-designed to suit the specific application.

Cylinders and heat pumps

Cylinders are now available which are designed to work in conjunction with heat pumps to deliver high flow rates, decrease running costs and improving heat transfer times. For example, the latest addition to the Kingspan Hot Water System range is the new Albion Aerocyl unvented copper hot water storage cylinder. This purpose-designed, low-maintenance cylinder can be specified for use in conjunction with either a heat pump as the sole source of energy or with solar thermal applications complementing the heat pump.

Compatible with a wide range of air and ground source heat pumps, the cylinder features a coil, which allows maximum heat transfer of renewable energy into the stored water. Fast flow rates delivering more than 45 litres of hot water per minute meet all the modern criteria for powerful showers and fast filling baths. As well as quick recovery coils and the use of an external expansion vessel to reduce maintenance, Albion Aerocyl heat pump cylinders have the added benefit of an electric immersion heater for backup.

These low maintenance cylinders are manufactured from high grade copper for excellent corrosion resistance and also feature 50 mm of environmentally friendly foam insulation to reduce standing heat loss values.

Buffer tanks

To achieve an even smoother operation for the heat pump, buffer tanks can be incorporated into a space heating system. The buffer tank increases the volume of water a heat pump has to heat, allowing the excess heat to be stored until it's required and reducing the short cycling during normal operation of the heat pump. It also provides a thermal store to aid the defrost cycle of the heat pump and avoids the water within the system cooling.

The size of the buffer tank required varies with the size of the heat pump being used. Albion Aerocyl buffer tanks are available in both vented and unvented format in a range of capacities from 50 to 150 litres.

As more end users turn to our industry for expert advice in renewable technology, installers have an opportunity to increase the amount of added value work they do and make a valuable contribution to reaching carbon reduction targets.

However, it is their responsibility to ensure the renewable heat equipment, such as air source heat pumps, performs to optimum levels and they recognise that a matched package of a purpose-designed cylinder and buffer tank will extend the life of the system and achieve high flow rates, improve heated transfer and hot water recovery times.

Kingspan provides a complete air source heat pump package. Installers simply need to add the pipe work. The company also provides support from initial advice, through to bespoke design, onsite training and installation, final commissioning and technical support.