14 October 2021
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Air-cooled chiller preparing to be proved in climatic test chamber
James Richardson, technical manager at Fujitsu General Air Conditioning UK, explains how changes to the Ecodesign Directive earlier this year are having a positive impact for chillers.
Chillers are enjoying something of a resurgence as technological improvements have increased versatility and enabled the use of a single product for both comfort and process cooling solutions.
A further development came in January with the implementation of adjustments to the Energy-related Product (ErP) regulations (Tier 2), which saw the introduction of new efficiency levels and separate performance requirements depending on the type of application.
The Ecodesign Directive provides rules for improving the environmental performance of products and sets out minimum mandatory requirements for the energy efficiency of these products. It aims to help prevent creation of barriers to trade, while improving product quality and environmental protection.
Chillers must now be compliant with the requirements specified for their intended use. Minimum performance standards are measured by Seasonal Energy Efficiency Ratio (SEER) for comfort cooling, which is then processed and represented by Seasonal Space Cooling Energy Efficiency Ratio as a percentage value (ηs,c), and Seasonal Energy Performance Ratio (SEPR) for process cooling. Packaged rooftop units are covered by SEER and Seasonal Coefficient of Performance (SCOP), while condensing units and condenser-less units are excluded from the ErP regulations. Where a chiller is used for both comfort and process cooling, i.e. dual-use, it is measured by SEER, although manufacturers can voluntarily choose to include the SEPR.
The improved energy efficiency as a result of these changes, when compared to the requirements under Tier 1, can be seen throughout the Clint portfolio available through Fujitsu in the UK.
Comfort cooling
Air-cooled liquid chillers with < 400 kW cooling capacity show an increase of 8% in relation to SEER, while for units with > 400 kW capacity the improvement is 11%. Water-cooled units have increases of 2% (< 400 kW), and 11% (> 400 kW). Air-cooled and water-cooled heat pumps show 8% improvements for all capacities, while rooftop units and rooftop heat pumps (> 1000 kW) boast increases of 18% and 8%, respectively.
Process cooling
For high temperature process cooling, air-cooled liquid chillers (> 400 kW) show an 11% improvement, while larger units (> 400 kW) are up by 10%. For water-cooled units, the increases are 8% (< 400 kW), 7% (> 400 kW) and 6% (> 1500 kW).
Away from the legislation, it is also worth reflecting on some of the technological advances which have had an impact and ultimately made these efficiency gains possible. Fujitsu’s partnership with GI Holding Group (GIH) means it has an extensive range of Clint liquid chillers, heat pumps and 4-pipe units with scroll compressors available, with cooling capacities ranging between 50 kW-1.2 MW, operating on R452B or R454B refrigerants in addition to R410A. Scroll and Turbocor compressor options are available from 200 kW to 3.8MW, using R513A or the ultra-low GWP R1234ze as alternatives to R134A.
Turbocor compressors
A new multiple stage compression design has reduced what would typically be a large centrifugal compressor into a more compact variant, even compared to its positive displacement screw or reciprocating compressor alternatives. With a low number of moving mechanical parts, the centrifugal compressor is an effective choice in any design. Because of its high rotational speeds - to generate an acceptable pressure difference - a large amount of friction is placed on the shaft bearings, which decreases efficiency and requires an essential source of lubrication. If the oil lubricating the shaft is not cooled sufficiently or develops flow problems, the result usually is catastrophic.
Danfoss developed the Turbocor compressor with an integrated inverter control system and revolutionised efficiency and reliability with magnetic friction-free shaft bearings. This means that the compressor can operate without oil, removing the oil cooling circuit with no wear and tear on the shaft bearings. Sensor rings that can detect the shaft position 100,000 times per second also provide improved control and monitoring.
Microchannel heat exchangers
The use of aluminium microchannel heat exchangers has reduced relative refrigerant charge quantity by up to 25% compared to the more traditional copper and aluminium coils. With increased thermal performance and a reduction in air pressure drop, this design choice leads to both environmental and efficiency benefits.
Clint chillers are compliant when used with options including EC inverter fans, EC inverter fans with high static pressure, inverter compressors and the full range of available refrigerants.
Measuring efficiency
- SEER is the overall energy efficiency ratio of a comfort chiller, representative for the cooling season, calculated as the annual cooling demand divided by the annual energy consumption for cooling.
- SEPR is the efficiency ratio of a high temperature process chiller at standard rating conditions, representative of the variations in load and ambient temperature throughout the year, and calculated as the ratio between the annual refrigeration demand and the annual electricity consumption.
- SCOP is the overall coefficient of performance of a heat pump using electricity, representative of the heating season, calculated as the annual heating demand divided by the annual energy consumption of the system.
- SSCEE Seasonal Space Cooling Energy Efficiency (ηs,c), applies to comfort chillers with a supply water temperature exceeding +2°C and is defined as a percentage. It takes into account the SEER and annual electricity consumption. It is a similar metric to ESEER in terms of ambient temperature but has defined accurate weightings based on ambient run hours and standby power consumption.
