ULT freezer

In contrast to short term sample storage at +4 to −20 °C (39 to −4 °F) by using standard refrigerators or freezers, many molecular biology or life science laboratories need long-term cryopreservation (including "cold chain" and/or "colder chain" infrastructures) for biological samples like DNA, RNA, proteins, cell extracts, or reagents.

[3][failed verification] Cryogenic chest freezers can achieve temperatures down to −150 °C (−238 °F) to −152 °C (−242 °F)[4] and may include a liquid nitrogen backup.

The time strongly depends on the type of insulation, the efficiency of the compressor system as well as the installed metal shelves within the freezer.

[citation needed] Due to the low temperature, ULT freezers consume high amounts of electric energy[7] and hence are expensive to operate.

[8] Nonetheless, a comprehensive report published in 2015 by the Center for Energy Efficient Laboratories (funded by Pacific Gas & Electric, Southern California Edison, and San Diego Gas & Electric utility companies as part of their Emerging Technologies program) found that laboratories in California consumed an estimated 800 GWh/year, with ULT freezers being the greatest contributor to that total.

[10][11] Depending on the volume of the freezer, the opening frequency of the users as well as the number of samples, the energy consumption starts from ca.

[7] Modern ULT freezers employ HC (i.e., hydrocarbon) gas mixtures: typically, ethane and propane.