Air conditioning shows the way to reducing carbon-dioxide emissions

Thousands of Mitsubishi VRF air-conditioning systems installed in buildings in London and other cities and towns 10 to 15 years ago could be replaced with the company’s latest generation of equipment to reduce energy consumption and carbon-dioxide emissions by 55% — with a payback of just one year.
Air-conditioning equipment installed as recently as 10 years ago is an energy-guzzling monster compared with the latest equipment, and Mitsubishi Electric has addressed the issues of replacing such equipment to reduce carbon-dioxide emissions by more than half.Air-conditioning equipment has been getting more and more efficient during the last decade. So great has been the improvement in efficiency that it can be easier to pass the SBEM analysis that is required to satisfy Building Regulations with an air-conditioned building than one based on natural ventilation. The logic is simple. A naturally ventilated building is required to have a carbon footprint 23.5% less than the notional building complying with the 2002 Building Regulations, compared with a 28% improvement for an air-conditioned building — an improvement that is easily achievable with the latest air-conditioning systems. But, as we are constantly reminded, meeting the Government’s targets for reducing the UK’s carbon emissions necessitates substantial reductions in emissions from existing buildings — and air-conditioned buildings are no exception. Economic case Cost inevitably enters into the equation, and this is an issue that has been carefully analysed by Mitsubishi Electric in devising an economic case for replacing existing Mitsubishi Electric VRF systems as little as 10 years old using its newly launched City Multi YHM range, which provides both cooling and heating. Not only are YHM units more efficient than previous units, but they are also smaller (both height and footprint) than the previous YGM range and 33% lighter on average. In particular, YHM outdoor units can pass through an 800 mm-wide door and be carried in a typical 6-person lift, suiting it to inner-city areas where access to rooftops by crane is restricted or difficult. High-efficiency versions can achieve a seasonal energy-efficiency (SEER) ratio as high as 6.26, 18% higher than even their immediate predecessors. Energy-saving potential However, it is when the performance of the latest equipment is compared with that installed 10 years ago that the energy-saving potential of replacement becomes apparent. According to Phil Ord, Mitsubishi Electric’s product marketing manager for VRF, the best City Multi equipment of 1998 had an SEER of just 2.38, compared with 6.26 today. That amounts to a reduction in the energy required for cooling of over 60%. In other words, the Government’s target for 2050 can be achieved today — at least for air conditioning. The new YHM systems use heat pumps, so they can also provide space heating. What is more, that heating can be provided more efficiently than by a heat-pump system installed 10 years ago. Phil Ord’s best-case figures suggest a reduction in heating energy consumption of almost 48%, with YHM systems capable of achieving a COP of at least four. And the many buildings with wet heating systems served by gas-fired boilers would see even greater reductions. Strong economic case However, the fact remains that despite these highly desirable reductions in energy consumption, there must be a very strong economic case for refurbishment, especially if it involves replacing perfectly functional equipment. That is why Mitsubishi Electric has taken into account the practical issues of reducing the capital and installation costs associated with replacing existing equipment with new. Phil Ord explains that the simple replacement approach devised for YHM reduces installation costs by enabling the reuse of existing pipework and wiring for power and controls — even though the new equipment uses refrigerant R410A, compared with R407C and R22 for previous systems. New cooling-only and heat-recovery YHM systems can completely reuse previous pipework and wiring. If a heat-pump system is to be installed, the refrigerant pipe from the outdoor unit to the first branch joint needs to be replaced to meet pressure regulations. Phil Ord’s calculations indicate that a new 8 to 10 hp heat-pump YHM system would be associated with annual carbon-dioxide emissions of 4772 kg, compared with 10 588 kg for a 1998 model. That reduction in emissions is also reflected in annual running costs, which are reduced by 55%. And the payback period? Just one year. ‘We sold over 75 000 kW of comfort-cooling R22 systems up until 2002,’ says Phil Ord, ‘and many of these systems are ready for an upgrade. Installing our YHM with its replace function can help reduce power consumption by up to 60%, leading to a significant reduction in CO2 emissions. ‘These thousands of 10-to-15-year-old VRF systems that use R22 refrigeration are coming to the end of their useful life, and the YHM system offers a straightforward way to safely remove this ozone-depleting refrigerant, whilst improving performance and energy efficiency for customers.’ With building-services manufacturers improving the performance of their equipment to this extent, there should be no difficulty reducing the carbon footprint of buildings — and energy bills at the same time. Installing less efficient equipment simply to reduce capital cost has to become yesterday’s attitude — and soon.
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