What are the benefits of incorporating air-source heat pumps in schools?

Heat pump systems are at the heart of sustainable heating and cooling and from the economic perspective; the government support this technology having invested over £50m to boost the installation of heat pumps into Schools across England and Wales.

The money has been available in the form of grants also some independently run schools can benefit from an interest free Carbon Trust loan to pay for the installation and maintenance of heating using air source heat pumps.

Focus on sustainability

As part of the continuing program to refurbish every secondary school in England over the next few years this is providing a huge opportunity to change the way that renewable energy is used in public buildings. The BSF (Building Schools for the Future) programme involves the government devolving funds to LEA (Local Education Authorities) and schools for spending on maintaining and improving their buildings. Part of this requirement is a focus on the sustainability of schools, with schools being assessed for their environmental performance levels under the Government’s BREEAM (Building Research Establishment Environmental Assessment Method) standards.

The schools of the future should therefore have a more energy efficient construction, which are heated through more renewable sources and have lower operating costs. The low carbon buildings programme has made renewable energy sources such as heat pumps a really attractive and viable option, with the overall result being a reduction in Carbon Dioxide released into the atmosphere and that is to the benefit of all our futures.

Schools help to set an example

There are definite advantages for schools that invest in renewable technologies. Schools help to set an example in the use of sustainable energy sources to the rest of society. As young people grow up being more aware of renewable energy systems, it means they will become more widely accepted as the norm, not only for public buildings but also for domestic use.

Heat pumps in Schools form a key component in the renewable approach to a balanced budget. Not only can they make a huge contribution to reducing carbon emissions, they can also cut payback periods by 35 to 40% through fuel savings.

Air-source electric heat pumps are year-round space-conditioning systems capable of providing heating; cooling, and some new models now provide domestic hot water. Their appeal lies both in that they offer heating and cooling in a single piece of equipment-which usually means a lower capital cost-and in that they provide heat at a lower cost than electric resistance heating, gas or oil. They can be used in most commercial applications and some industrial processes, particularly those that generate waste heat.

An air-source heat pumps transfers energy between the outside air and either air or water inside a building. In cooling mode, it functions just like an air conditioner, moving heat from the inside of a building to the outside; in heating mode, the refrigerant flow is reversed so it takes low-temperature heat from the outside air and mechanically concentrates it to produce high-temperature heat, which is then delivered to a building. Because most of the heat is simply moved (pumped) from the outdoor air to the indoors, the amount of electricity required to deliver it is considerably less than would be required from electric resistance heat.

How could I use a heat pump?

A heat pump can be used where there is a low temperature source of heat. For example, heat can be transferred from a source at 5ºC and delivered as warm air at 40ºC.

Applications include space heating and cooling, pre-heating domestic hot water, heat recovery and dehumidification in both domestic and industrial sectors.

Does a heat pump use renewable energy?

Yes, the source is usually renewable energy from an ambient heat source or waste energy. For example, with a 3:1 performance ratio, for every three units of heat delivered, two units can be from the renewable heat source and one from the electrical power supply. A heat pump, operating on a ‘green electricity’ supply from an accredited renewable source, offers emissions-free heating and then three units of renewable energy would be delivered for every one unit of energy purchased as ‘green electricity’.

What are the different heat sources?

Ambient heat from water, air, or the ground; or waste heat from industrial processes or combined heat and power units are often used. In air-source heat pumps, passing air at ambient temperature over a finned heat exchanger, thus heat is extracted into the evaporator of the heat pump. In a water source heat pump, river, lake or ground water is cooled as heat is extracted.

In the case of ground source heat pumps, the collector pipe is installed in one or more trenches or boreholes. A water/anti-freeze solution is pumped around this loop of plastic pipe, extracting heat from the ground.
The heat extracted from the ground or lake or river water is replaced by heat from the atmosphere.

What are the advantages of a heat pump system?

Energy Efficient: Heat pumps are very energy efficient as they consume a little energy (usually as electricity) in order to deliver three or four times as much energy as heat. The ratio of energy-out to energy-in depends on the operating conditions and typically varies between 2 to 1 and 5 to 1. The overall average is called the seasonal performance factor.

Environmental: Heat pumps access renewable or waste energy and so displace consumption of conventional fossil fuels (gas, oil, coal). As electricity generation technologies improve, the emissions performance from the combustion of fossil fuels and renewable electricity generating capacity increases, so the greenhouse gas emissions associated with electricity consumption are reducing – making heat pumps even more environmentally beneficial.
Physical: Different types of heat pumps have different benefits. Ground source heat pumps have -
•    No visible external equipment
•    No external fans
•    Quiet running
•    Very little risk of accidental damage
•    Adaptable to many locations.

Economics of heating houses: The running costs of a heat pump are much less than a traditional gas boiler heating system, also LPG, oil and electricity. The initial capital cost is usually higher than other conventional heating systems. The ‘whole-life’ cost, combining the capital and running costs is favourable for heat pumps compared to fossil fuelled systems – and, especially, compared with other forms of electric heating.
Heat pump systems are used in commercial premises (offices, hotels, supermarkets) providing heating and cooling – and in some industrial processes and applications.

What about greenhouse gas emissions?

Heat pump systems consume energy in moving heat from one place to another. The principal use of energy in a heat pump is to generate the motive power to drive the compressor. The associated emissions depend on the power source driving the compressor. In the UK the heat pump will typically create around 55% of the greenhouse gas emissions from the most energy efficient domestic gas heating system (where the heat pump is providing space and domestic hot water heating).