HOW TO COOL YOUR SPACE WITH A HEAT PUMP
May 2022
BUILDING CONSTRUCTION FOR TODAY’S CLIMATE
The construction of UK buildings today is focused on good insulation and minimum air leakage to prevent heat loss in the winter. New residential buildings must also be designed to limit solar gains and reduce the risk of overheating in the summer – a risk that has increased in recent years due to the improved insulation and higher proportions of glass being incorporated into building designs.
Overheating has become such an important factor, that a new Approved Document O [1] comes into force in June as part of the uplift to England’s building regulations. The updated standards focus heavily on thermal comfort improvements, the use of more energy-efficient systems and building materials, and improvements to ventilation.
Natural ventilation and passive cooling can be achieved by simply opening windows, but with rising outdoor temperatures combined with improved fabric standards, this will be insufficient for many occupants demanding thermal comfort throughout the year.
THE RISE OF COOLING
In the UK, cooling has historically been dominated by the non-domestic sector. For reasons mentioned already, along with a move to home working, domestic cooling is starting to become more prevalent, and a strong growth in retrofit in this area is anticipated.
Currently, BSRIA estimates that just 5% of UK homes have some form of cooling technology [2]. But a recent government research report predicts significant growth, estimating that by the end of the century, homes will require 75% to 85% of the UK’s total cooling energy consumption [3].
AIR CONDITIONING
The UK cooling market is dominated by what is commonly known as ‘split’ air conditioning units, consisting of a condenser coil outside the building and an evaporator coil inside. By using basic air-to-air refrigeration technology, they condition the room, reducing air humidity and temperature. Nearly all the split units available today can be thought of as heat pumps, by reversing the refrigeration process, they can heat the room in winter too.
This form of cooling is known as wet cooling, or deep cooling. To reduce the humidity, you are taking moisture out of the air which then condenses when passing across the evaporator coil. Condensation is collected and drained or pumped to the outside of the building.
Although air conditioning is an effective means of cooling, the running costs and energy consumption are very high.
Refrigerants commonly used in heat pumps are based on energy efficiency, safety, reliability and technical performance, which is why non-flammable HFCs such as R-410A, R-134a and R-32 continue to be widely used.
The use of carbon-neutral refrigerants like carbon dioxide, propane and ammonia are now being explored because their global warming potential is much lower. The GWP of a refrigerant is its global warming impact relative to the impact of the same quantity of carbon dioxide. Carbon dioxide has a GWP of 1, ammonia zero, R-410A 2,088, R-134a 1,430 and R-32 677. As an example, you could say that R-410A is 2,088 times more damaging to our planet than carbon dioxide.
THE SHIFT TO RENEWABLE ENERGY SYSTEMS
In a bid to phase out fossil fuel heating to reduce emissions, the UK government has announced a ban on installing gas boilers in new buildings from 2025 and a complete ban on installing them in any building from 2035. Instead, low carbon heating systems such as heat pumps will be favoured, and the government is encouraging this through incentives such as the Boiler Upgrade Scheme.
Heat pumps take energy from the ground or the air and convert it to heat the water for space heating. What a lot of people don’t know is that a heat pump can offer cooling in the summer too, very much like the air-to-air split units we mentioned earlier.
HEAT PUMPS
There are different types of heat pumps available, but we’ll focus on the most common: ground-to-water (ground source), and air-to-water (air source).
GROUND SOURCE HEAT PUMPS
The temperature in the ground is fairly constant throughout the year, typically between 8 and 11°C. These stable conditions make ground source heat pumps slightly more efficient than their air source counterparts. Their performance however very much depends on local geological conditions. It is recommended that a geological survey is carried out to determine surface and sub-surface temperatures, thermal conductivities and diffusivities of the rock and soil layers.
There are two basic options for ground source heat pumps: a horizontal ground array, and a vertical borehole. The ground array is the most economical solution, but the land available to lay the pipes will dictate the amount of energy delivered to the building. Pipes will be laid in excavated trenches at approximately 1.2 to 1.5 metres below ground level. If there is insufficient land available, a vertical borehole system could be considered. Boreholes can be between 60 and 200 metres deep.
AIR SOURCE HEAT PUMPS
Air source heat pumps take the energy from the air around us, so the fluctuation in outside temperature does affect the efficiency. That said, they still deliver energy at outdoor temperatures below zero, albeit they have to work a little harder. Air source heat pumps are relatively simple to install and can be positioned either adjacent to the building, on the roof, or in a remote location. They provide the most economical solution for renewable energy technology, making them the most commonly chosen option in the UK today.
COOLING WITH HEAT PUMPS
Ground-to-water heat pumps can provide efficient cooling. Because of the stable temperature below ground, even in summer, the naturally cooler water from the ground can be used to cool a space without using the refrigeration process. This is known as ‘passive’ cooling. If cooler water is required, this can only be achieved by using the refrigeration process. This is known as ‘active’ cooling.
Air-to-water heat pumps can only achieve cooling in summer by using the refrigeration process, so active cooling.
HOW A HEAT PUMP WORKS FOR HEATING
The heat pump refrigerant enters what is known as an evaporator coil. The fan unit blows air across the coil, and this makes the refrigerant boil and evaporate at low temperature, leaving the coil as low temperature, low-pressure gas. This gas enters a compressor that increases the pressure and temperature of the gas.
This high pressure and high-temperature gas then enters what is known as a condenser coil. In this case, the coil sits inside a water vessel. It then gives up its energy to the water, effectively heating the water to be used in heat distribution. As it leaves the condenser coil, the refrigerant is in a liquid state, cooler, but still at high pressure. It then passes through an expansion valve that reduces the pressure and the temperature, and the whole continual process starts again.
How an air source heat pump works in heating mode
HOW A HEAT PUMP WORKS FOR COOLING
The same heat pump that heats water can cool water too. This is achieved by simply reversing the flow of refrigerant. The reversing valve diverts the high pressure, high-temperature gas to the evaporator coil – this is now effectively the condenser coil. What was the condenser coil is now the evaporator coil. A second expansion valve reduces the pressure and temperature the other way – therefore the complete system is working in reverse. The consequence is that what is now the evaporator coil, gives up its coolth to the water in the vessel.
How an air source heat pump works in cooling mode
INTELLIGENT CONVECTORS FOR HEATING AND COOLING
At Jaga, we design dynamic climate convectors that can be paired with heat pumps to switch between heating and cooling for a comfortable indoor climate all year round.
Jaga’s hybrid convector is simply a natural convector with small thermal activators sitting on top of the heat exchanger – this technology is called Dynamic Boost Hybrid (DBH). The activators (small fans) inside the DBH unit increase the airflow across the heat exchanger and can increase heat output by up to 300 per cent. This means the physical size of the unit can be smaller than natural convectors and much smaller than steel panel radiators.
The fans are generally very quiet in dynamic operation, typically circa. 30 dBA. They operate naturally too, with the fans off. They have a boost function where the fans operate at full speed, to bring a space up to temperature very quickly.
COOL TECHNOLOGY
The unique aspect of Jaga’s DBH technology means that the same heat emitter can provide summer cooling too. This is not energy inefficient air conditioning, it’s what we call light cooling, or dry cooling. It’s a form of gentle cooling used to cool down a room by a few degrees, without having to use a lot of energy. It’s ideal for pairing with heat pumps.
Light cooling occurs when the water temperature is consistently higher than the condensing temperature (or dew point), usually around 16°C depending on weather conditions, and therefore no condensation water is formed. The energy consumption is much lower than deep cooling, especially in combination with a heat pump so it’s much better for the planet.
REALLY COOL TECHNOLOGY
If light cooling is not sufficient, then Jaga has a solution to offer deep cooling, or full water-based air conditioning. Deep cooling uses chilled water below 10°C to provide a powerful, much cooler output. It will usually produce condensate because the surfaces in contact with the chilled water (pipes etc) are below the dew point.
This can be provided by our range of dynamic trench convectors, or our recently improved Briza range of fan coil units. Both consist of a dynamic, high-performance heat exchanger, powerful forced draught fan and robust casing, providing powerful heating, cooling and ventilation. They are naturally low water content emitters, so again, quick to respond to thermal demands.
WHICH COOLING METHOD IS BEST FOR YOUR PROJECT?
When considering cooling a space, a cooling load calculation must be carried out by a qualified engineer to design a suitable system to achieve the desired room temperature.
If the installation is correctly designed and executed, Jaga’s DBH, which can be installed inside most Jaga Low-H2O convectors (either at time of order or retrofitted inside existing installations), can be a cost-effective and more environmentally friendly method to gently cool your space. As DBH is a light cooling method, no condensate is produced, so no condensate drains are needed. This makes installation a lot quicker and easier.
If you need powerful, deep cooling for more extreme temperatures, or are looking for an increased level of controllability, Jaga’s deep cooling with condensate trays would be the best option.
WHICH PRODUCT IS BEST FOR YOUR PROJECT?
All Jaga’s dynamic climate convectors provide high outputs at low flow temperatures, making them perfectly suited to projects with a heat pump installation. They’re designed to enable high efficiency from renewable energy systems. Providing the system can provide cooled water, your convectors will be able to operate in cooling mode.
For heating and light cooling
- Strada Hybrid: Wall-mounted, compact, stylish and slimline convector with DBH. For residential, commercial, and public buildings.
- Tempo Hybrid LST: Wall-mounted, flat-packed, compact, and safe LST convector with DBH. For care and nursing homes, educational facilities, and sheltered housing.
- Guardian Hybrid LST: Wall-mounted, safe LST convector with one-piece casing and DBH. For care and nursing homes, educational facilities, public buildings, hospitals, and healthcare facilities.
- Maxi 2020 Hybrid LST: Wall-mounted, highly durable LST convector with DBH. For heavy-duty applications, prisons and secure facilities, care and nursing homes, educational facilities, public buildings, hospitals, and healthcare facilities.
- Mini Canal Hybrid: Efficient trench climate convector delivering 3 to 4 times more heat than a traditional natural trench heating solution. For commercial and public buildings.
- Clima Canal 08: Extremely compact and silent trench climate convector. For residential, commercial, and public buildings.
For heating, light and deep cooling, and ventilation
- Briza 12: Compact and slim fan convector offering powerful heating and cooling outputs. Can be wall-mounted or built-in. Available in 2 pipe or 4 pipe options. For residential projects.
- Briza 22: Super-power fan convector offering very high heating and cooling outputs and optional ventilation. Can be in-wall or in-ceiling. Available in 2 pipe or 4 pipe options. For commercial and public buildings.
- Clima Canal 10, 13, and 19: Very high-power level trench climate convector completely integrated into the floor that can include a ventilation connection. Equipped with a condensation drain. For commercial and public buildings.
Above is just a selection of Jaga products. Please see our website for additional products or contact us directly to discuss your requirements. We will be sure to help you find the best solution for your project.
GET IN TOUCH
For more information about heating and cooling with heat pumps, and for support with selecting the best solution for your project, please get in touch with our expert team.
REFERENCES
- HM Government (2021). Approved Document O: Overheating. Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1057374/ADO.pdf
- BSRIA (2019). UK Chillers reports. Available at: https://www.bsria.com/uk/market-intelligence/market_reports/air_conditioning/
- Department for Business Energy and Industrial Strategy (2021). Cooling in the UK. Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1019896/cooling-in-uk.pdf
