As global temperatures continue to rise, the demand for more efficient refrigeration systems has become paramount, especially in areas with high ambient temperatures. A recent Montreal case study by the Canadian-based OEM Evapco showcases how integrating HVAC in a grocery store’s CO2 (R744) refrigeration rack can provide a solution to this problem.
HVAC Integration in Grocery Stores: A Case Study
Presented at the Food Industry Association (FMI) Energy and Store Development Conference, the details of this innovative integration were revealed by François Aucoin, Director of Engineering at Evapco, and Nicholas Torres, Commercial Refrigeration Sales Manager at Evapco.
Aucoin mentioned, “Because we integrated the systems, we had better control over all the conditions – temperature for the cases, store humidity, and less defrosting.” This combined system not only offers the benefits of temperature control but also system heat and gray water reclaim. If a store is located in a warm climate and desires parallel compression, Aucoin pointed out that the additional costs of incorporating the AC with the suction group are minimal.
Improved Efficiency and Operation
A significant advantage of this integrated system is the enhanced efficiency of the compressor when connected to the AC coil linked to the high-temperature (HT) suction group. This connection aids in maintaining subcritical operations and helps regulate the flash tank, ensuring smoother operation and fewer disruptions.
The retailer in Montreal did not provide Evapco with the energy performance data directly. However, they did mention that the performance was on par with other stores of similar size and system type.
Technical Aspects of the Integration
The study by Evapco centered around a full-service supermarket of 30,000ft^2, owned by a significant Canadian retail chain. The store’s refrigeration system was a CO2 rack with three suction groups, each using one variable frequency drive (VFD):
- Low-temperature (LT) Group: This included four compressors, one at -30°F (-34.4°C) and three at -20°F (-28.9°C) suction, providing a capacity of 300,000BTU/hr.
- Medium-temperature (MT) Group: With six compressors at 20°F (-6.7°C) suction, the MT group had a capacity of 1,600,000BTU/hr.
- High-temperature (HT) Group: This group, consisting of four compressors at 34°F (1.1°C) suction, provided a capacity of 1,000,000BTU/hr, specifically for AC and heat reclaim.
With 100% heat reclaim, the HT group operates multiple systems, including the AC, dehumidification coils, and others, reclaiming heat rather than wasting it. This not only increases the efficiency but also provides for applications like hot water, air heating for specific areas, dehumidification for the servicing floor, and hot water for sanitation.
The store’s controls were fully integrated, employing the Parker Micro Thermo platform, which also facilitated remote access monitoring and control.
The Addition of HVAC
When diving into the design specifics, adding an AC system required a nuanced approach, especially regarding the lift suction. However, the test for feasibility yielded positive results, with benefits like preventing frost accumulation in the AC coils due to the higher suction temperature of the CO2 HT compressors. When there’s no AC load, heat is transferred for heat reclaim, ensuring efficient operations and better liquid-to-gas ratios.
Heat rejection was also streamlined with Evapco’s patented Purity Plus design, leading to stabilized compressor demand, especially during high ambient temperatures.
Gray Water Reclaim
Given the increasing ambient temperature trends in Montreal, Evapco integrated two adiabatic gas coolers piped in parallel using mist technology. This system reclaimed rainwater from the store roof and AC coil condensate, funneling it into a collection system in the mechanical room, minimizing the usage of treated city water.
Despite the benefits, challenges arose, particularly regarding controlling the negative pressure created by the cooking hoods and coordinating with different trades for system integration.
François Aucoin emphasized the viability and benefits of CO2 technology, suggesting that nothing stands in the way of integrating the HVAC system into the refrigeration. All that’s required is a design adaptation. Evapco, based in Laval, Quebec, specializes in CO2 modular refrigeration equipment, boasting over 432 installations in North America alone.
“There is always a demand for rejected heat rather than wasting it outside,” states François Aucoin, reinforcing the importance and efficiency of such integrated systems.
Source: Information and quotes derived from an article on r744.
TL;DR: A Montreal case study by Evapco found that integrating HVAC into a grocery store’s CO2 refrigeration rack stabilizes medium-temperature compressor demand during high ambient temperatures. This combination enhances overall control, improving store conditions such as temperature, humidity, and defrosting frequency. The integrated system maintains efficient compressor operation, has the potential for gray water reclaim, and effectively utilizes rejected heat rather than wasting it. Challenges like controlling negative pressure from cooking hoods arose but are manageable. Evapco, a leader in this technology, emphasizes the benefits and viability of such integrations in HVAC and refrigeration systems.