Heat pumps are often thought of in terms of domestic installations, but there is a wide range of higher output options suitable for a variety of commercial applications. Dimplex, for example, offers a new range of ground source heat pumps with outputs up to 130kW, sufficient to heat large commercial, leisure or educational establishments.
Heat pumps – the technology
Even at subzero temperatures, heat pumps draw usable heat from the ambient air, ground or nearby water source (such as a well or lake) and compress it to provide enough energy to run a heating system. Air source and ground source are obviously the two heat pump technologies suitable for buildings in most locations, and are usually installed in conjunction with low temperature underfloor heating or fan convectors.
Heat pumps are very efficient in that the only power they need is the electricity to run the compressor, and for every 1kWh of energy used to do this, the heat pump produces up to 3-4kWh of free heat, drawn from the environment. This high efficiency makes heat pumps one of the more viable options for the incorporation of renewable energy.
While ground source heat pumps require the installation of ground collectors either horizontally under a large area of land or, more commonly, vertically in a borehole (which yields more heat but requires specialist drilling equipment), air source units involve minimal disruption to the fabric of the building and its landscape, making them particularly suitable for retro-fits.
A widely-held misconception is that air source heat pumps can’t compare to ground source in terms of efficiency (CoP). However, in the UK, this isn’t necessarily the case. Air source efficiency improves dramatically above 0ºC, and in our mild climate where winter temperatures average around 4 to 8ºC, air source heat pumps offer CoP comparable to ground source models.
Keeping it cool
A major advantage of heat pumps for commercial premises is their ability to cool a space, as well as heat it. Heat pumps’ operation can be reversed to draw heat from the building and transfer it to the environment, where it is harmlessly stored for when it’s needed. Heat pumps either use passive cooling, where cool water is circulated through the system without the compressor being used, reducing the ambient temperature by a few degrees, or dynamic cooling, where the compressor and heat pump cycle are reversed to extract heat from the air in the building, creating a greater cooling effect.
So instead of maintaining an air conditioning system in addition to the heating system, a heat pump can do both, and unlike variable refrigerant flow air conditioning systems with their risk of greenhouse gas emissions, heat pumps only need minimal and straightforward maintenance and safety checks.
The green imperative
So, heat pumps offer a straightforward way to incorporate renewable energy in a building to reduce both fuel bills and carbon emissions. But apart from the environmental issues, why are renewables so high on the business agenda?
One of the key drivers for the incorporation of renewables is the updated Part L of the Buildings Regulations, introduced in April 2006. For non-domestic buildings, the general thrust of this new legislation is to not only reduce carbon emissions by 15-20% through the conservation of fuel and power, but also to make a 10% contribution to energy requirements from renewable sources where appropriate.
A high proportion of the measures required by Part L needs to be considered at an early stage in the design and planning, as the energy performance of a building must be demonstrated before it is constructed. Factors such as size and orientation of windows, insulation, ventilation and heating systems are all factors which affect a building’s energy performance.
However, the incorporation of renewables can lift the performance of the building when considered as a whole. For example, use of a heat pump to provide some or all of the building’s heating requirement can give more flexibility in the specification of building fabric.
Another key driver for renewables in commercial buildings is the Government’s Planning Policy Statement 22, known as the Merton Rule after the London borough which was the first council to incorporate the Government guidance in its planning legislation. The Merton Rule requires developers to ensure that for new non-residential development above a threshold of 1,000 sqm, at least 10% of all energy production comes from renewable energy equipment on site.
Over 150 local councils are have already implemented or are currently considering similar policies. Although the Merton Rule targets new build developments, it can only be a matter of time before similar guidance extends to refurbishments. What’s more, Planning Policy Statement 22 guidance is really only the start, as today’s voluntary environmental standards become tomorrow’s legislation.
Some real-life heat pump applications
Dimplex heat pumps have been used in a wide variety of commercial premises. With grants from the Government’s Low Carbon Buildings Programme Phase 2 now offering subsidies of up to 35% to public sector and not-for-profit projects, Dimplex and its network of approved heat pump installer partners have been involved with a wide range of organisations applying for heat pump funding, with projects including schools, libraries, places of worship, community halls and social housing.
New build school – ground source
The first Dimplex application to secure funding from the LCBP was a new extension at Scarning Primary School in Dereham, Norfolk, where Dimplex provided three SI 21 CS ground source heat pumps to give a total output of 63kW, with ground collectors laid under the playing fields. The LCBP grant covered 35% of the costs of the first 45kW of heat output, including the heat pumps, ground collectors and other equipment, the ground works and the commissioning of the system.
Retro fit offices – ground source
Ground source heat pumps can also be practical for retro fitting. A Dimplex SI 14 MS (14kW output) ground source heat pump has been key in the conversion of an historic harbourside grain warehouse at Aberaeron, West Wales. The three- to four-storey stone building was converted into open plan office space, with improved insulation to conserve heat, and new underfloor heating. As the building stands in a largely residential area there was limited space available for ground collectors, so a vertical borehole over 150m deep was drilled to accommodate the ground collectors. The drilling was achieved within a week, with minimal disruption to neighbours.
New build visitor centre – air source
A new National Trust visitor centre combining all the latest principles of sustainable design in a low energy building at Aberdulais Falls in South Wales selected a Dimplex LA 20 AS air source heat pump to power its underfloor heating. For the National Trust, it was vital that the principles of sustainability and energy efficiency were at the core of the project, so the heat pump is powered by a hydro-electric water turbine at the Falls, making the system entirely sustainable and effectively zero-carbon.
With legislation on energy efficiency and the incorporation of renewables set to become increasingly rigorous in the future, now is the time to take advantage of the benefits of heat pumps, as those businesses that are quick to make the most of low energy bills and low carbon emissions will be ahead of the game.