MOISTURE CONTROL IN SUPERMARKETS
Supermarkets are a complex environment and standard air conditioning systems are often not effective for the various store configurations. Humidity can affect refrigeration operation and customer purchasing decisions if the store is too cold or because frozen products are not visible or iced up. Humidity is a hidden energy issue. Often over half the store energy is refrigeration and air conditioning, and designs based on the first cost can leave a substantial energy legacy for the owner. Desiccant dehumidification offers an array of benefits to store operation energy and comfort, which can outweigh the initial investment.
REDUCED AIR CONDITIONING COIL WORK
The design practice of (DOAS) Dedicated outdoor air systems, with desiccants is now prominent with technology advancement and over 100,000 systems in commercial buildings.(ref AHRAE May 2008)
DOAS avoid humidity problems and save energy by removing the latent load of outside air, and over-drying the outdoor air sufficiently (i.e. 5°Cdp or 30%RH @ 23°C) to absorb the store (moisture) latent load. This avoids the cost of dehumidification of the entire recirculated air stream.
Up to 80% of refrigeration case energy is consumed by the condition of the air around the evaporator, and ambient moisture is a significant component. Generally, it can be said a reduction in store humidity of 10%RH would save 10% of case energy. (ref ASHRAE handbook 2003 2.3 (fig 1)).
Benefits to cases are:
- Reduced energy input
- Reduced latent load (ice ) on evaporators
- Reduced defrost cycles
- Reduce strip or anti-fog heaters
- Less ice and condensation on the product
- Reduced product loss due to defrost
Reheating of overcooled air is a traditional low-cost practice to allow the air-conditioning plant to dehumidify to dewpoint (ie 12°C) and re-heat the air back towards room temperature. Part load conditions often see ventilation loads creating a need for dehumidification but little or no sensible cooling, so overcooling becomes more wasteful. This practice was restricted in 1999 and later banned in the USA by building energy standard ASHRAE90.1 and countries like Australia have banned the use of electric elements for reheat.
Stores are often too cool due to the refrigeration case spill loads, the heaters are inclined to be on continuously to maintain comfort temperature neutralize the spill and overcooling.
A Supermarket with electric reheat capacities of around 150kW and a continuously running heater element can cost 150 x $0.10/kWh x 365 x 24 = $US134,000.
Desiccant dehumidification offers an array of benefits to store operation energy and comfort.
Desiccant dehumidification has had substantial application into supermarkets in humid climates due to operating and compliance requirements of the case manufacturers, and the inability of conventional HVAC to dehumidify effectively. With energy consideration now prevalent, the low first cost electric reheat systems are being responsibly designed out.
Seibu Giken DSTs range of FLEXISORB products fit the market needs with:
- High-efficiency dehumidification, incl. plug fans and advanced D-Max Japanese desiccant rotor.
- Condensation free construction
- Robust base frame designed for better logistics
- External lock, improving internal maintenance
- One side service access for a smaller footprint
- Customized to suit differing needs of supermarket designs (handing, waste heat, gas, split DX, CHW)
SEIBU GIKEN D-MAX ADSORPTION ROTOR TECHNOLOGY HAS BEEN A LEADER FOR MANY YEARS WITH THE INVENTION OF THE SILICA GEL WHEEL, NOW OFFERS THE FOLLOWING ADVANTAGES:
- Efficient drying process
- Long service life
- High dehumidification capacity
- Mechanically strong
- Japanese quality and performance compliance