UK: Chesterfield-based Ultra Refrigeration has developed a high efficiency CO2 refrigeration pack with full heat recovery for the total comfort heating and air conditioning needs of convenience stores.
The company’s Integrated Power Pack (IPP), based on Bitzer’s Ecoline CO2 reciprocating compressors, captures heat from the high temperature discharge side of the pack by passing hot gas through a compact contraflow heat exchanger, transferring heat to a water-based heating system. Hydronic fan coils provide comfort heating and cooling for the store and adjoining warehouse facilities.
The system as used in a number of convenience stores also supplies hot water to an over-door air curtain on the store’s main entrance, which operates constantly during opening hours, saving up to 14kW of electrical energy.
The IPP systems deployed deliver a total of up to 90kW of heating and 40kW of comfort cooling, although the design is scalable and can be configured for larger applications if required.
With efficiency boosted by significant energy savings on the heating side, the system is estimated to have a pay-back of around two years. In addition to energy savings and the much lower environmental impact, a further benefit of the system is that only low pressure pipework circulates within the store, avoiding any risks associated with in-store high pressure systems.
The stores served by the packs typically have around 22kW of HT refrigerated cases and 6kW of lLT units. If the pack’s current cooling requirement is not sufficient to provide the minimum design load to heat the store, a forced load evaporator is brought into circuit to generate the heat required – achieving the required operating conditions more efficiently than would be the case with conventional air source heat pumps.
The packs installed to date are based on four Bitzer Ecoline CO2 compressors, one dedicated to the LT side (Ecoline model 2HME-3K-40S), two handling the HT side (Ecoline model 4JTC-15-40P), and one covering comforting heating and cooling duties (Ecoline model 4HTC-20-40P) – with the option for load-sharing, depending on conditions.
“Some CO2 refrigeration plants don’t fully harness the opportunity for heat recovery offered by the high discharge temperatures generated by CO2 systems. IPP is designed to recover as much of this energy as possible to save on whole-building energy costs,” said Ultra Refrigeration MD Steve Shipp.
In addition to use in food stores, the pack is said to lend itself to applications in industrial process projects requiring pre-heating of water or space heating. It has also been used in a low temperature climatic chamber for testing engines down to Siberian temperatures as low as -45ºC, with reclaimed heat being used to warm the facility’s control centre and workshop.