HEATING AND VENTILATION
by altering the speed of all fans in unison. Power consumption falls dramatically with any reduction of heat load or ambient air temperature, as the input power requirement is relative to the cube of fan speed.
Of course, this money and energy- saving, noise-reducing technology comes at a premium, but payback can be in as little as three months. In fact, the change from traditional stage control to variable speed control can even pay back the cost of the entire cooling package in as little as two or three years.
Power savings and notable noise reductions
Exploring stage-controlled and variable speed-controlled fans comparatively really showcases the benefits of this more advanced noise reducing technology. Where the ambient and/or heat dissipation requirements dictate that half of the fans operate at full speed on a standard stage-controlled fan system, all of the fans would typically need to operate at 47% speed on its variable speed-controlled counterpart. In this scenario, the stage-controlled equipment would be consuming 50% of its maximum input power, compared to the variable speed-controlled plant which would be consuming just 10.4% (0.473
) of
its total input power. The noise reduction levels are equally as impressive in favour of variable speed fans, with the example staged-controlled solution only managing a reduction of 3 dB, and the speed- controlled system delivering a reduction of 16 dB. Since changes in noise follow logarithmic laws, this 13 dB difference equates to the stage control solution being 21 times noisier.
Adiabatic cooling technology with variable speed fans operating in mission- critical 24-hour environments can typically deliver annual energy reductions of around 96,000 kW and an annual cost reduction of £9,660.1
Intelligent installations for better noise reduction
When it comes to adiabatic cooling in particular, working closely with a skilled manufacturer can further improve noise reduction. The ideal scenario would be what is known as ‘free field’ conditions, where the cooler is situated away from buildings and other plant – not a likely scenario for many hospital locations in the UK. Installing a cooler next to a wall will instantly increase the noise output by around two or three decibels which, because of the logarithmic nature of sound, translates to double the volume. Specification best practice will only assist you so far in meeting your noise transmission targets, even with the assistance of an independent acoustician, because many adiabatic cooling suppliers
48 Health Estate Journal October 2018
Three Adiabatic V-Coolers en route to Chelsea and Westminster Hospital.
will only furnish their customers with noise data from the fan manufacturer, which doesn’t reflect the real volume of the kit in a real-world scenario. The answer is to identify and work with a cooling specialist which independently verifies its equipment for acoustic performance, using anechoic chamber testing and inspection methods. Failure to specify plant with accurate noise verification testing can lead to non-compliance post- installation, leading to costly additional measures or a complete kit replacement.
Flexible installation through intelligent design
For hospitals and other healthcare environments, two of the biggest specification concerns are noise reduction and footprint, with space at a real premium for retrofitting cooling equipment. The general rule of thumb for this sort of technology is ‘the quieter you need it, the larger it will be’, which is often not conducive with specification criteria. Adiabatic coolers offer great flexibility in their design, allowing manufacturing and installation teams to create a solution which meets the threshold for noise reduction, while retrofitting far more technologically advanced equipment into an often tight footprint.
Orientation plays an important role in the flexible design of adiabatic coolers, with the equipment working at optimum functionality when mounted upright or on its side. Then there is the addition and intelligent positioning of attenuators, which can reduce unit size from, for example, a six-fan model to a four-fan alternative to save space on the ground. Fans can be repositioned too, so that the often bulky attenuators sit atop the equipment to reduce the overall footprint.
Using the skills of a
design-focused manufacturer To really benefit from the energy-saving and risk reduction capabilities of an adiabatic cooling system, no matter the surrounding environment you need to work within, employing the skills of a design-focused manufacturer can support the specification process. Options such as mounting the plant on extended legs, or even building the equipment into a wall, are possible for
both space-restricted new-build projects or the retrofitting of older cooling equipment.
As NHS Trusts and private medical and care providers continually strive for improvements in energy efficiency, better control over risks such as Legionella, and optimum patient comfort, the adiabatic cooling market forges ahead with meeting the increase in demand from the healthcare sector. The goal is to bring to market cooling solutions which revolutionise complex maintenance and reporting procedures, minimise the use of harmful chemical treatments, and deliver monetary savings which simply cannot be ignored.
Reference 1 Estimates based on 24 hours per day, seven days per week, 50 weeks per year, with an electricity price of £0.1/kWh
hej
Matthew Griffin
Matthew Griffin is a specialist in the bespoke design and specification of adiabatic cooling technologies, with nearly 10 years’ industry experience. He has been integral to the replacement of cooling towers for a number of NHS Trusts throughout the UK, including projects for Great Ormond Street Hospital and Glan Clwyd Hospital. Like all of Transtherm’s consultants, he is a highly skilled, qualified engineer, and works closely with customers to promote the education and best practice specification of adiabatic cooling technology for the healthcare sector, among others.
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