Total building solutions are the key to higher efficiencies
The development of smarter and more sustainable buildings is a necessity if Britain is to meet its legally binding carbon-reduction commitments. Integrated environmental control solutions incorporating heat-pump based technology combined with heat recovery can make a major contribution towards this goal. John Durbin examines the significant energy savings possible using these systems.
The Department of Energy & Climate Change’s ‘Pathways to 2050 — key results final report’ recognises that over the next 40 years the carbon emissions produced by the UK’s buildings will need to be reduced to at least 45% of the 2010 level. To achieve this goal, it will be vital to design climate-control systems capable of cutting carbon emissions significantly.
At present, many of the UK’s buildings operate quite separate systems for heating, hot-water production, air conditioning and refrigeration.
This means that a huge proportion of the heat energy produced as a by-product of air conditioning and refrigeration systems simply goes to waste, rather than being captured and used elsewhere in the building.
By integrating climate control systems in an innovative way and incorporating heat recovery systems based on heat pumps, it is possible to create a much more holistic — and sustainable — energy cycle within a building. Such solutions could cut energy usage by up to 60%, making a massive difference to the sustainability of the built environment if they are applied comprehensively.
One of the most effective ways to implement an integrated solution is by harnessing the high efficiencies of heat recovery, as provided by variable refrigerant flow (VRF) technology. [VRF is the generic term for what Daikin terms VRV, variable refrigerant volume, Ed.]
VRV’s great advantage is that it varies the refrigerant volume within an air-conditioning system to match precisely the building’s requirements at any moment. This means that the output adjusts continuously to ensure that each area maintains its set temperature, while saving both money and carbon emissions, because it only uses the minimum energy required.
Such highly energy-efficient solutions can be developed for a wide variety of settings. Possibilities include on a major scale for airports, shopping centres and stadia; for complex environments such as leisure centres, hotels and civic buildings; or for community facilities like schools, shops and health centres.
For example, in a major department store, where refrigeration is required for cafes, restaurants and kitchens, it is easy to see how the heat rejected by this function can be used elsewhere in the building, such as door air curtains or to provide hot water in wash rooms.
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| The key to the 53% reduction in energy consumption on the ground floor of a hotel (top red bar to green column) lies in exploiting integrated services and heat recovery supported by heat pumps. Non-heat recovery refrigeration and VRV air conditioning is replaced with integrated CVP refrigeration and VRV, both with heat recovery. With the support of heat pumps, recovered heat can be used instead of electricity to produce hot water and serve door curtains. | Energy savings of 40% can be made by moving from a single duct-mounted 2.5 kW fan coil with individual room controllers in hotel bedrooms (top red bar) to heat-recovery VRV with control based on room occupancy and usage (green column). |
VRF heat recovery in conjunction with a heat-recovery air curtain and a heat-pump hot-water module can reduce energy consumption by around 35% compared to a conventional system.
Heat recovery can also be used for ventilation.
Heat recovered from stale and contaminated air extracted from a room can be transferred to the fresh incoming air, which is then delivered into the room. Recovering energy (heat and coolth) from the exhaust air therefore reduces the cooling/heating load on the air-conditioning system, while offering all the health benefits of clean, odour and pollutant free air.
Automatic bypass of the heat exchanger makes possible the additional benefit of free cooling, where needed, when outside temperatures are below indoor requirements.
As well as the need to increase energy efficiency, reducing energy consumption will also be vital in helping to achieve the 2050 targets. Integral to this is the need to improve the monitoring and control of systems. This means changing user behaviour and enhancing our collective understanding of how energy is managed within our buildings.
Intelligent control technologies can play a significant role in monitoring and maintaining heating, ventilating and air-conditioning systems (the largest user of energy in the workplace). In fact, intelligent controls could increase a system’s efficiency by a further 30%.
For commercial offices, banks and retail stores, a good intelligent control solution should be able to set heating and cooling levels zone by zone, so public and staff areas can be maintained at preferred temperature levels, while air curtains at entrances are controlled separately, as are meeting rooms and IT server rooms, thus maximising the overall energy efficiency of the building.
However, to achieve these major reductions in energy usage and improvements in energy efficiency, it is vital that a whole building solution is designed from the outset. By examining the temperature requirements of the entire building to incorporate a total integrated climate-control solution, not only will it be possible to make buildings more sustainable, it will also help cut energy bills.
John Durbin is engineering-department manager at Daikin UK.
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The whole-building approach to reducing overall energy consumption is demonstrated through an online tool recently introduced by Daikin UK called Daikin City (www.daikincity.co.uk). This interactive virtual city enables specifiers to compare energy savings that might be achieved through the use of various VRV-based technologies in a variety of buildings such as a bank, hotel, school, restaurant and retail outlets. The two diagrams of a hotel on the facing page are just a small sample of the scope of this web site.
Other energy saving solutions include Daikin’s CVP refrigeration heat recovery. Again the on-line tool explains the principles of the technologies in a clear and visual manner, providing an indication of the energy saving potential of VRV technology. In the case of a convenience store with CVP refrigeration heat recovery system, savings of 24% can be made on a standard system.
Visitors can view the impact that different energy-efficient options have on an energy calculator, which displays the potential energy savings that could be achieved as part of an overall solution.
