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In recent years, heat recovery has become an increasingly more common and desirable functionality in units for ventilation, heating and cooling (HVAC). The general idea is to recover as much as possible of the energy that has already been “spent” for heating or cooling, and use that energy again and again. But what if it is not only used repeatedly in one place when needed, but also in other parts of an HVAC system and no matter the outdoor conditions?
A variety of units have incorporated some form of heat recovery, from air handling units, rooftop units and units for variable refrigerant flows (VRF), to heaters, chillers and heat pumps. The reason for doing this is, naturally, to decrease the need for additional external energy and, hence, lower the electricity consumption. Waste not, want not, as they say.
Heat recovery in traditional chillers and heat pumps has been either partial, which is a passive system recovering about 20-30% percent of the energy from the load, or total, which is an active system when energy can be recovered up to the maximum load. In neither case, however, there has been no control of the temperature process - it has been all or nothing - and heat can only be recovered while producing the main load.
The market for cooling and heating units with heat recovery has been strong in regions with warmer climates, like southern and central Europe or the Mediterranean, for the simple reason that it is easier to recover energy in warm or average outdoor conditions. In cooler climates, like northern Europe, there simply has not been enough demand, and the gains have been less noteworthy. However, current trends are changing with an increasingly warmer global climate and an increased emphasis on energy efficiency as key issues for the future.
Polyvalent units for all possible outdoor conditions
Recently, new technology in the form of air sourced heat pumps with the possibility to produce hot water despite very low outside air temperatures, entered the market in northern Europe. Today, this market is ready for further new technology, this time in the form of heat recovery systems. The new polyvalent units are capable of asynchronous recovery; that is, they can recover energy from both heating and cooling, making them more energy efficient regardless of user needs or ambient temperatures. With a sophisticated logic control system, they can modulate the amount of recovery up to total heat recovery, while still being capable of regulating the produced temperature during recovery. These polyvalent units can manage all possible outdoor conditions, even colder climates, all year round and they are eminently capable of recovering enough energy to repay the initial investment, and more.
The installation and use of multi-purpose polyvalent units are, in other words, becoming more and more interesting even in regions with colder climates. They are becoming increasingly popular, and come with several advantages over a traditional heater/boiler with additional chiller system. The most obvious is that only one unit, instead of three, is needed to produce heating, cooling and domestic hot water. With one unit, one connection and one power supply the number of components are drastically reduced and the installation is significantly simplified. Moreover, while the heat recovery possibilities are hard to beat, the fact that these units have the ability to also transfer energy within the system, to where it is needed the most, makes them highly advantageous from an energy point of view. Further, as these units follow the rapid developments in regards to natural refrigerants they allow a leap into the future in terms of sustainability.
What does the market has to offer?
The new Omicron Zero series of polyvalent heat pumps from Swegon is an example of the above, and it is developed and optimized for use in the Nordic countries. These Omicron Zero heat pumps can draw benefit from heat recovery and still produce heat, cold and high temperature water for domestic use when needed, no matter the outdoor conditions.
The many years of further development of Omicron Zero have resulted in completely new and re-designed control systems with improved logic and optimised algorithms. Which, in combination with the independent heat exchangers, enables advanced heat recovery capabilities over a wider range of outdoor ambient temperatures. Last but definitely not the last, Omicron Zero use the future-ready R290, propane, refrigerant which result in a very low global warming potential (GWP), no issues in regards to F-gas regulations, only a significant leap towards a better future.
