John Durbin, engineering department manager, Daikin UK, argues that ‘whole building thinking’, incorporating the use of heat recovery systems, can pave the way to meeting legislative demands on energy-efficiency and carbon reduction.
Maximising energy-efficiencies and minimising carbon emissions have never been more important for our buildings than they are now. The CRC Energy Efficiency scheme, pending legislation regarding seasonal efficiencies, and the phasing out of R22 refrigerant are all designed to deliver increasing efficiencies within our buildings.
However, if we are really serious about reducing our carbon output, we need those involved in modern building design to collaborate fully in working towards the utopian goal of ‘zero heat rejection’. Although it can be argued that this is still more of an environmental aspiration than an operational reality, an intelligent approach to heat recovery would be a major step in reducing energy usage.
It has been predicted that the secondary trading market under the CRC Energy Efficiency Scheme will run to some £600m. A holistic approach to heating, cooling and ventilation would enable those organisations with the biggest energy bills and carbon footprints to move themselves into credit on that market.
Whether designing for a new-build or a major refurbishment project, we need to incorporate heat recovery as an integral part of a well-designed and fully integrated climate control system. Every day, many hundreds of tonnes of CO2 are released by waste heat being rejected into the air. It is easy to see that if we capture this waste heat and reuse it where it is needed, then we will achieve the highest levels of efficiency. We need to embrace a ‘whole building thinking’ approach, in which heat recovery becomes a vital part of a virtuous circle of climate control.
The principle is simple: by taking unwanted heat that is generated from items such as IT suites or telecoms equipment and reusing it elsewhere in the building where it is needed, heat can be generated at a much lower cost, as well as drastically reducing carbon emissions.
Whatever the building be it a new hospital, retail complex or office building it is vital to analyse usage patterns and occupancy levels right from the design phase to develop fully integrated systems. The technology already exists to achieve this. Some heat pumps divert heat from indoor units in cooling mode to areas that require heat. Air-source heat pumps, which use solar-heated air to produce 65-75% renewable heat for buildings and services, have the added advantage of achieving significant energy cost savings compared to traditional, fossil fuel boiler systems.
The effectiveness of air-source heat pumps can also be maximised by the use of multiple zones on one circuit. Their flexibility means designs can be optimised so that IT and server rooms, for example, can been cooled; hot water can be provided for sinks and radiators; and heat reclamation can be used to provide warm air at entrances requiring air curtains.
It is critical, though, that architects and contractors talk to heating engineers and experts at the outset.
If a building is looking to achieve impressive energy-efficiencies, then the use of heat recovery in balanced mode within a VRV system can also be employed. Previously impressive COPs of around four pale by comparison with the exceptionally high COPs of nine or 10 available when employing this technology.
Achieving balanced mode operation might involve cooling one area of the building that is experiencing the highest heat gains and transferring that reclaimed heat to other areas of the building that require heating or, indeed, hot water, which is now also possible within a heat reclaim system. To do so, the indoor units need to be arranged to maximise the occasions when this balanced operation can take place, with the heat recovery system diverting recovered heat to wherever it is needed, thus contributing significantly to the goal of zero heat rejection.
However, to achieve these industry beating COPs, it is vital to analyse right from the start a building’s multiple requirements, usage patterns and varying occupancy levels, in order to design a fully integrated system that optimizes energy-efficiency and heat recovery.
By working with suppliers early in the design process it is also possible to ensure that a lifetime approach is taken to systems planning. Ongoing operational efficiency of air conditioning systems has a huge impact on both emissions and energy consumption, and also affects the reliability and life expectancy of the system. Achieving optimum running levels by utilising the latest remote monitoring and malfunction prediction technology will also play its part.
Another area with room for improvement is comparing how real-life performance of an air conditioning system might vary from its predicted performance. Indeed, pending EuP legislation will make this compulsory. Generally, performance is expressed in terms of nominal performance; however, this can hide the significant differences that exist between rated and actual performance. By assessing and then improving real-life performance, huge increases in efficiency are possible.
Furthermore, it is possible to comply with changing legislation and qualify for financial incentives, such as the Enhanced Capital Allowance (ECA) scheme. With this incentive, businesses can receive enhanced tax relief for investment in energy-saving equipment that meets specified government criteria. It allows 100% of the investment to be written off against tax in the year the investment is made, thus enabling some of the cost of meeting legislation to be off-set against tax.
So, by looking at all aspects of a building’s heating and cooling system from the beginning, and incorporating the findings into a comprehensive design strategy, it is possible for an organisation to reduce its energy usage to comply with energy-efficiency legislation. At the same time, long-term running costs can be reduced and financial incentives utilised to help off-set the initial outlay.