Researchers working across a wide range of life sciences disciplines rely on ultra-low-temperature (ULT) freezers for the secure storage of biological samples, from blood, cells and tissues to drug and vaccine candidates. Consistent and accurate internal temperatures ensure the viability of these valuable study materials, and are vital to the reliability of study results.

Outdated ULT freezers are not only inefficient – due to poor insulation and heat dissipation – they can also jeopardise sample viability and research outcomes through frequent breakdowns. Inefficient insulation also means that older units will rapidly heat up in the event of a power outage, leaving little time for remedial action.

Laboratory technicians at the University of Sussex had first hand experience of these challenges, working with a selection of outdated freezers that were all between 15 and 25 years old. To mitigate the issues, the team developed an elaborate alarm system to alert technicians of changes in temperature, but this set-up was far from ideal, as it was often inaccurate and incorrectly sent notifications to staff in the middle of the night or during holidays – which subsequently turned out to be false alarms.

On top of this, the lab’s insurance only covered freezers that were less than 15 years old, leaving them at significant risk of losing samples without a means of recovering the costs due to the age of their cold storage units. The group was therefore in urgent need of a new cold storage solution with improved insulation and cold retention, an early detection system for temperature fluctuations and built-in proactive preventative maintenance.

In addition, the University of Sussex actively embraces green initiatives – such as the Laboratory Efficiency Assessment Framework (LEAF) – and aims to become one of the world’s most sustainable universities. The high-energy consumption of its legacy freezers strengthened the case for a complete replacement of its previous cold storage provision in favour of more energy-efficient ULT freezers that would support the transition to a net-zero institution.

Innovative technologies bring a plethora of benefits

The university acquired state of the art ULT freezers that combine frequency conversion compressors and hydrocarbon refrigerants, and quickly noticed improvements in sample security, energy efficiency and sustainability.

The legacy units had each consumed up to 20 kWh per day, whereas the improved insulation and increased energy efficiency of the new freezers results in a consumption of approximately 8.2 kWh per freezer per day. Furthermore, the reliable temperature stability of the new freezers allows them to now be set to -70°C instead of -80°C without affecting sample viability, reducing electricity use by an additional 50%.

This dramatic reduction in energy requirements has resulted in an annual cost saving of over £400 per freezer.

The upgrade also presents an opportunity to consolidate cold storage and dispose of old samples, and the improved organisation of the new units has helped researchers to reduce the overall number of freezers required from 24 down to 20. This has optimised the use of valuable lab space and further reduced energy expenditure, amounting to annual energy savings of approximately 100,000 kWh, or roughly £20,000 per year in costs, providing a complete return on investment in just seven years.

Sample security is further improved by the long holdover times offered by the new freezers. These units remain below -50°C for up to 24 hours without power, due to their advanced insulation and temperature retention capabilities. This has substantially enhanced sample preservation in the event of a power outage, and gives team members peace of mind that they have an extended timeframe to salvage samples. A cutting-edge monitoring and data logging system has also been installed alongside the freezers, alerting staff by text, phone call or e-mail if there’s a temperature discrepancy, providing an extra level of confidence and enabling employees to accurately track temperature changes over time.

The foundations of a greener future

The University of Sussex’s proactive approach to addressing the challenges associated with the legacy cold storage equipment has yielded significant benefits. Transforming its cold storage capabilities with advanced frequency conversion technology has enhanced the institution’s operational efficiency, sample preservation and cost-effectiveness, freeing up funds that can be invested back into vital research. Installing a suite of new freezer units also represents a significant step towards achieving the university’s sustainability goals, and has established a framework for future