With reports that only ten years remain to develop and implement new technologies to generate clean electricity before climate change reaches the point of new return, the drive to cut energy use is set to reach fever pitch. Meanwhile, end-users have also now realized the importance of publicizing their green credentials with corporate social responsibility becoming a competitive issue. Therefore the right choice and selection of building services, and especially climate control equipment, has become key since energy efficient kit can make a big difference to an annual carbon output.

With air conditioning accounting for over 30 per cent of annual electricity consumption, in a typical office, and also representing a significant capital investment for many companies there is a real opportunity for consultants to offer their clients invaluable advice on product specification. However, since expenditure is at the front of end-user’s minds, specifying energy efficient chillers either for new installations or to replace antiquated or energy wasteful onesmust, when it is done, be done right.

However, selecting the most energy efficient chiller for the job is not that simple. When comparing new chillers, it is important to look at each unit’s EER (Energy Efficiency Ratio), the ratio of cooling output compared to power input.  Eurovent, the European Committee of Air Handling and Refrigeration Equipment Manufacturers, has set its own formulae to calculate EERs, making it easier to compare the performance of chillers manufactured by Eurovent accredited companies. Eurovent has also established its own classification for full load EER. This classification follows a similar A to G approach to the Energy Labelling Directive (although the directive is restricted to household appliances and is only mandatory for Room Air Conditioners with a capacity equal to or lower than 12kW). Eurovent's classification is a voluntary initiative, unrelated to any directive and no label is used. Instead the energy efficiency of chillers is designated by Eurovent A or Eurovent B in catalogues and the Eurovent Directory of Certified products.

However, it’s worth at this point sounding a word of caution. A chiller’s EER should not be considered in isolation since most units rarely operate at full capacity throughout their life cycle. That’s why it’s also vital to take a look at a chiller’s ESEER (European Seasonal Energy Efficiency Ratio), as set out by Eurovent. The ESEER is the chiller’s performance ratio which compares power input to cooling power output at partial loads, therefore giving a more realistic view of the chiller’s life-cycle performance. In order to create this index several parameters are taken into account to establish an average use of chillers throughout Europe including weather data, building load characteristics and operational hours. (Although the ESEER cannot calculate exact energy consumption for individual use in a particular geographic location.)

The ESEER is calculated as follows: ESEER = A.EER100% + B.EER75% +C.EER50% +D.EER25% with the following weighting coefficients:

A = 0.03

B = 0.33

C= 0.41

D = 0.23

The ESEER is calculated by combining the three part load EER figures for 35%, 50% and 75% load with full load EER. Eurovent publishes this global single figure in its Directory of Certified Products together with cooling capacity and power input for standard conditions at full load. The operating temperatures and average weighting coefficients for Europe are given in the table below.

Table: Eurovent ©

As well as considering a chiller’s EER and ESEER consultants should also ensure they establish the integrity of the energy efficiency data published in manufacturers’ literature. Although some energy efficiency data is validated by independent testing organisations, such as Eurovent, some manufacturers’ literature simply presents a theoretical calculation of the performance of individual components, such as compressors and heat exchangers which when put together affect the performance of the other.

Another key resource for finding energy efficient chillers is the Carbon Trust’s Energy Technology List (www.eca.gov.uk/etl/). Only chillers meeting the Carbon Trust’ performance criteria are included on the list. It is very easy to identify these products since the ETL symbol is used to endorse qualifying products. Chillers on this list guarantee both reduced capital investment through significant tax benefits for the end-user (Enhanced Capital Allowances) and lower energy costs, leading to climate change levy savings, which all make attractive reading to a client’s finance director.

Chiller manufacturers, like Rhoss, one of the leaders in European chiller design and the company behind our new PowerCool and Z Power range recognize the demand from end-users to reduce fuel consumption and meet EER and ECA compliance requirements. The result is increasingly innovative component design and application to create low energy chillers.

For example, the new breed of energy efficient chillers, like Z Power, use the latest generation of semi hermetic screw compressors specially developed for R134A refrigerant.

The single pass counter flow shell and tube evaporators are designed so that the water and refrigerant passes are always counter flow which means that as the efficiency of evaporation is increased, pro rata, energy consumption is reduced.

Electronic expansion valves enable the system to operate at lower condensing pressures resulting in significant savings in compressor power input and a microprocessor controlled economizer circuit further increases the EER ratio.

Another way to reduce a chiller’s operating costs is by incorporating within it a free cooling system. This takes advantage of low ambient temperatures to pre-cool the water returning to the chiller, reducing the load on the compressors and therefore the energy consumed. When the ambient temperature falls 1^oC below the temperature of the water returning to the chiller, for example, the water return temperature is 12^oC and the ambient is 11^oC, free cooling can be activated. Free cooling is particularly effective in the UK where the ambient temperature is below 11^oC for between 50% and 70% of the year.Typically, with an ambient temperature between 3^oC and 5^oC below the set point temperature, the compressors will completely switch off and the only energy consumed will be by the low power condenser fans.

Most buildings have a requirement for a constant supply of hot water, if only for sanitary purposes, and this will usually be generated by a gas or electric water heating system. A water chiller at full load conditions will be rejecting into the atmosphere, the heat removed through the air conditioning system plus the power input to it, a significant amount of energy.

For just a small fraction of the capital cost, most chillers can be fitted with a desuperheater, a heat recovery vessel, through which, for example, boiler feed water can be passed. The desuperheater can raise water temperatures as high as 70ºC, thereby considerably reducing the load on the building’s water heating system and the associated fuel costs.

As fuel prices continue to escalate clients will take a greater interest in plant procurement to combat climate change levy charges. It will therefore become essential to be able to easily recognise low-energy chillers in order to specify the most efficient unit for a building. It will be equally important to ensure installed chillers run to their optimum efficiency and that every possible method of enhancing this is employed.

The latest Powercool and Z Power series from Coolmation have been developed by Rhoss to provide the best EER (European Efficiency Ratio) performance available in their range, (76.5kW up to 1470 kW cooling capacities) and are both Eurovent Certified. Like the majority of chillers now available from Coolmation, they are also approved and listed under the Government’s ECA scheme. This means that if the client purchases an ECA approved chiller, he can set off 100% of his capital allowances against profits in year one and not over the usual three years which can create a valuable cash flow improvement.