Exploiting the capabilities of air conditioning

This introduction of the CRC Energy Efficiency Scheme throws down the gauntlet for organisations required to cut their carbon emissions. Simon Keel looks at how updating air-conditioning systems can have a huge benefit on an organisation’s energy consumption.

With the introduction of the CRC Energy Efficiency Scheme this month, the requirement to cut energy consumption has never been greater — and with it comes an even more convincing argument for moving away from inefficient air-conditioning plant by investing in new technology.

Upgrading air-conditioning systems to create more efficient and integrated solutions could provide a valuable opportunity for companies to avoid purchasing extra CRC allowances, as today’s air-source heat pumps provide higher energy efficiencies and, therefore, greater reductions in carbon emissions than ever before — and look set to continue offering even more significant savings in the future.

The meteoric rise in efficiency since their introduction in the 1950s has meant that the running cost and energy consumption of air-conditioning systems has dropped dramatically. Already recognised as renewable technology, air-source heat pumps can save tonnes of CO2, otherwise emitted by fossil-fuel burners by using solar-heated air to produce 65 to 75% renewable heat for buildings and services.

Of all the recent innovations in the market, the configuration that makes the largest contribution to improved energy efficiency has been direct-expansion inverter heat pumps and especially those in a multi split variable refrigerant flow (VRF) system. Being direct, there is no energy loss transferring from one medium to another, and there is no need for extra pump or fan power to be used to circulate the heating or cooling around a building.

The heating COP of a VRF heat pump is typically 3.3* to 4.0 kW of heat. Varying the refrigerant volume to exactly match the building need at any instant saves both money and carbon emissions, while allowing each area to maintain its set temperature. Daikin’s latest systems, for example, return even higher efficiencies than previous models, with a 14% average increase in efficiency across the range and the most efficient units reaching a 20% increase in efficiency. COPs and EERs (for cooling) of up to 4.3 and 4.1, respectively, are obtained at 100% connection, exceeding the energy-efficiency targets set out in Part L of the Building Regulations and the rigorous criteria set out by the Enhanced Capital Allowance (ECA) qualification.

Such heat pumps are relatively easy to install and operate, but a major part of the success of the success of heat pumps is the use of intelligent controls which, combined with the ability to monitor services remotely, ensures maximum performance efficiency at all times. In some cases, a service visit can even be arranged before the user knows there is a fault. Hundreds of thousands of such systems operating throughout the world have proved the point.

However, to achieve maximum perform­ance for minimal impact, 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 optimises energy efficiency and heat recovery.

Daikin, air conditioning, VRV, VRF
Even in winter, some areas of a building (such as server rooms and IT suites, will require cooling, and heat removed from these areas can be used to efficiently heat other parts of the building with a VRF heat-pump installation.

Heat recovery, the reclaiming of heat from one area within the building and transferring it to another, can provide substantial improvements in HVAC system efficiencies and contribute significantly to the goal of zero heat rejection. In fact a system operating with a balanced cooling and heating demand can achieve a COP of up to 10.

Taking a wider look at changes that are likely to influence decision making over the next 20 years, there are many new ideas and schemes coming forward. For example, chilled beams started to become popular only five or so years ago have replaced variable-air-volume (VAV) systems in most cases. They can operate with a chiller and a boiler to provide both heating and cooling.

Perhaps the most significant change, however, is the increased reference to a system’s total equivalent warming impact (TEWI). To assess the impact of a system, a calculation covering a long period must be made, usually 15 years. Using this method, two or more systems can be compared to see which would have the least impact. There are issues about global warming potential (GWP) of commonly used refrigerants At present, the most common refrigerants have high GWPs. However, they are highly efficient and when compared under TEWI, their systems generally come out on top as their intrinsic efficiency far outweighs the small amount of damage that may be caused through unexpected leaks.

We can never be certain what the future will bring. With such rapidly evolving technology changes are certain. However, what we do know is that the technology already exists to allow major carbon savings that can offset the impact of the CRC today.

Simon Keel is product executive with Daikin UK.

* This figure is based on the minimum COP to qualify for Enhanced Capital Allowances. Chiller technology has already started to change with the introduction of new compressors and efficiencies. There is also likely to be a move to new refrigerants, and changes in Building Regulations could well mean that smaller plant will be required than might have been expected.

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