A Revolution in Cold Storage
Blog Aug 09, 2016
AD: The quality of your laboratory’s sample store is reliant in part on the effective maintenance of a consistently low temperature, especially when the freezer is likely to undergo multiple door-openings throughout the working day – which is commonplace in busy laboratories. Thermo Scientific™ TSX ULT freezers are designed to exhibit a high level of temperature uniformity as part of their daily function. Where conventional refrigerant freezers use single-speed compressors with a simplistic binary on/off system that can challenge temperature uniformity across the cabinet, the TSX Series uses the sophisticate V-drive technology, which allows for a far more fluid and energy-efficient method of control.
JR: Can you describe the V-drive technology and the benefits this provides over conventional ULT freezers?
AD: Typically, ULT freezers will take approximately 50 minutes to recovery from a door opened of just 60 seconds, which can have consequences, especially when storing heat-sensitive materials such as antibodies or plasmid vectors. The TSX Series of ULT freezers, however, utilises the unique V-drive technology, which allows for far quicker recovery following freezer interruption than conventional refrigerant ULT freezers. It takes just 24 minutes to fully recover following 1 minute of open-door use. The technology allows the TSX freezers’ compressor to run at variable speeds subject to the situation, instead of having to cycle on and off continuously as is the case with conventional refrigerant freezers using a single speed compressor. The running of the compressor at a slower speed in the background means it can react quicker to a temperature spike, and instantly get to work to rapidly bring the temperature back down. Where other ULT systems often have to kick-start their compressor completely when temperatures rise, the TSX series of ULTs simply have to employ a gradual increase in compressor speed.
JR: Can you tell us about some of the features that help to reduce the energy usage of the TSX freezer?
AD: Conventional refrigerant freezers either have a low or high BTU reserve, which will either struggle to recover from temperature spikes quickly, or will waste vast amounts of energy as the compressor is forced to kick-in at full power as soon as the door is opened. The V-drive technology, unique to the TSX freezers, automatically tunes the BTU reserve capacity to the heat loads presented to the freezer, avoiding the need for the compressor to have to operate on full power instantly when the door is opened.
The compressor drive is fitted with an automated tuning control which works to optimize the compressors running speed and energy consumption. During stable periods, such as overnight, weekends, or quiet days, the V-drive will run at a low speed rather than switching off entirely - a more energy efficient method of operation. The freezer temperature is therefore constantly maintained, and following a sudden temperature rise after a door-opening event, the compressor can gradually increase in speed to compensate. The innovate design, paired with the V-drive, has meant that the TSX ULTs have passed all environmental tests. Testing showed that the TSX600V for example uses less than 0.015kWh/day per box stored – up to 50% less than other conventional refrigerant ULT freezers available. The TSX600 is estimated to use 48% less energy per year than other such ULT freezers, which could result in over £4,000 in savings on energy bills over a 10 year period1. This level of sustainability is pivotal for the TSX series – which are even manufactured in a zero waste facility!
JR: Are there any benefits to a -70°C setpoint as opposed to -80°C?
AD: Absolutely. While conventional refrigerant ULT freezers can run up to 18 kWh/day in energy usage, the TSX Series can offer energy savings up to 50%. And by switching from a -80°C to a -70°C setpoint, you can make an additional energy saving of 10-18%. Switching to a -70°C setpoint for example on a TSX600 results in a kWh/day of 7.8 (10% less energy than at -80°C). When making that same switch on the new TSX400, the kWh/day is 6.5 (an 18% reduction from -80°C). In most situations, -70°C is an acceptable setpoint, as nucleic acids for example can be safely stored at -20°C or -70°C, depending on the duration of the storage. Likewise, bacteria, viruses, and most proteins can also be safely stored at -70°C as well as DNA/RNA, bacteria, purified proteins, enzymes and more.