Frigesco’s flash defrost system has won a string of industry awards over the past year, and was recently crowned Refrigeration Product of the Year and Energy Saving Product of the Year in the National ACR Awards 2015.
ACR Journal looks at the technology behind the innovation, and discovers some unexpected benefits in addition to significant energy savings.
The technology uses a carefully-calibrated food-safe phase-change material to capture waste heat from the refrigeration system during normal operation, and use it to carry out high efficiency defrosts of evaporators.
The system was developed by a team headed by Professor Tom Davies, and is now undergoing field trials in working stores by major end users in the UK, the US and South Africa.
Hot gas defrost carries a significant energy and performance penalty, as it requires the refrigeration system to operate outside its optimum envelope for significant amounts of time in order to generate the heat for defrosting. This reduces the efficiency of the system and increases running costs.
Electric defrost incurs a direct energy penalty, through the consumption of electricity to melt frost using heaters. The use of electric fans adds further to energy consumption.
Legal and safety challenges
Due to its high specific heat capacity and good insulation properties, accumulated frost requires a lot of energy to melt it. Defrosting a refrigerated display case typically accounts for around 30 per cent of total energy used. When multiplied across a supermarket’s estate, or indeed the combined refrigeration systems in the food supply chain across a whole country, this amounts to an immense drain on energy supplies and a huge additional cost for end users.
A new approach
Controlled trials have confirmed that it can cut overall energy consumption of refrigeration systems by up to a fifth. Efficiency is improved, as it does not require electrically-driven components to deliver heat energy to frosted evaporators, although small pumps can be used to improve the speed of the process if required.
In addition, as it sequesters heat produced by the refrigeration system during normal operation, it adds a sub-cooling effect, improving performance and yielding further energy savings. In thermodynamic terms, the sub-cooling gain effectively pays for the post-defrost re-chilling required.
Traditional defrosting methods are known to be extremely inefficient, with as little as 20 per cent of the energy being used in the defrosting process. Not only is this inefficient, it adds a significant heat gain to the refrigerated space.
Although the main benefit is a reduction in energy use and lower running costs, the Frigesco system delivers other attractive benefits. These include:
- Improved food hygiene and safety due to more effective defrosts, and more stable temperatures in the refrigerated space;
- Longer working life and fewer breakdowns for refrigeration plant, due to more complete defrosts and improved equipment operation;
- Potential reductions in equipment capital costs due to design optimisation possible with the use of flash defrost;
- Reduction in a retail store’s overall maximum electrical draw, giving “head room” in locations where power supplies are near the limit, which may be vital in extreme weather conditions, as experienced in hot summer months;
- The more efficient defrost process stops the build-up of frost on floors and walls in the immediate environment of refrigeration plant, eliminating the so-called “Santa’s grotto effect”, and reducing slip hazards for store staff. Frigesco is currently working with a number of major UK and overseas food retailers on in-store trials prior to a global roll-out of the technology.
“Frigesco’s flash defrost is a genuine innovation, and the savings are substantial and proven. Retailers are understandably interested in adopting the technology.
“Given the potential savings and relatively low capital cost, I believe Frigesco flash defrost technology will be widely adopted by food retailers and supermarkets in the future. It deserves to become a mainstream technology across the industry.”