HEATING
Refrigerants applying the heat
Andrew Robinson, managing director of specialist HVAC distributor Exi-tite, looks at the role refrigerants play in heating applications.
W
e are all aware of the constant pressure to find solutions with increasingly improved efficiencies; especially within the built environment.
Legislative pressures such as the EU’s eco-design directive not only work to lower the EU consumer energy bills (estimated to be £440 per person by 2020), but create a Darwinist market, where weaker performing products, that do not meet minimum standards, will not be sold within the European market. It is estimated that 80% of the environmental impact that a product has is a result of the decisions made at its design stage. Focusing on product design by implementing the eco-design directive will therefore have the best results.
Heating processes are responsible for 37% of the UK’s overall carbon emissions on both a commercial and domestic front. The improvements resulting from legislation have seen energy consumption fall by 17% in the domestic sector and 18% in commercial uses since 1990. But why is this? Improved building fabric plays its role, but the technological advancements driven by the legislative pressure for efficiency improvements and reduced emissions have seen renewable technologies improve year-on-year. We shouldn’t forget that when we are talking about heating, we are not just referring to space heating, but also the inclusion for process heating. Whilst both require reliability, space heating should also have some focus on comfort.
The improvement of compressor technologies and control algorithms have been key factors in the growth of refrigerant application for heating purposes from a design point of view. The development of inverter compressors has not only allowed for more compact system designs but also has improved the ability to match system output to the demand required from it at any given time.
Operating this way provides a near continuous supply of energy, resulting in a much more consistent heating process in comparison with a direct on-line compressor. This means that any errors made during system design are not as pronounced in terms of over or under sizing equipment and so an individual’s comfort levels are less affected. If we look at some examples of using refrigerant for
40 October 2019
heating purposes, we can begin to understand the reasons and benefits for this increasing trend.
Applied in the commercial sector, air conditioning systems of varying size are being used for both comfort heating and cooling. Traditionally a heating system fuelled by a gas boiler would have been installed as a separate heat source during winter months, using the air conditioning system for cooling. By combining both a reduction in capital expenditure is realised and the buildings heating is generated from a renewable technology.
Using the same line of products, a traditional ‘air conditioning system’ can also be used to generate hot water, transferring heat energy to water rather than to the air that comes from the fan coils that we are used to seeing. This process allows us to supply, not only a wet heating system, but also use energy to heat potable water and water used for industrial processes.
The water temperature that is achievable can be up to 60°C using this method, extendable to 80°C/90°C using either a cascade refrigerant system or by using refrigerants directly with higher operating pressures such as CO2
(R744).
Focus shouldn’t only be on product design, the way we include these products in a system is also essential. We have designed systems to recover energy from spaces that are being constantly cooled, such as data rooms, and transferred this energy for hot water production for buildings potable water and wet system heating in offices. This would not have been possible if it wasn’t for the refrigerant transfer means and the development of extensive control options that are available in such complex systems.
Staying with heating, ventilation and air conditioning systems and commercial application, we introduce a large amount of fresh air into our buildings via air handling units to keep the buildings air quality maintained. This air would need tempering, so it doesn’t have an adverse effect on the building’s temperature.
Traditionally this process would have been carried out by the air passing over water filled coils within the air stream, the water temperature regulated for each coil provided by either a chiller or a boiler.
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