Solar powered ammonia cooling for California cold store

Enabled by a $225,000 financial incentive from San Diego Gas & Electric through the power company’s Sustainable Communities Program promoting energy efficient features, solar powered ammonia refrigeration technology provides for the cooling needs of a 134,511 square foot cold storage facility since March 2009 in San Diego County, California. According to C&L Refrigeration, the company called in to deal with refrigeration challenges, the building design is expected to cut energy costs by 75%.

The facility features:

• High efficiency ammonia screw compressors
   
• 8 evaporators at 420,000 Btuh or 35 tons each installed on the roof: Dedicated ‘penthouses’ were designed on the roof for the evaporators. Installing them on the roof allowed easy access for maintainance.
   
• Integrated refrigeration and solar panel control systems: By adjusting the frequency on variable speed drives of each compressor, the refrigeration output is lowered to meet the available power from the solar panels during the hottest part of the day when energy is most expensive.
   
• Reduced heat load to attain a 75% more efficient building: To achieve this, the ceiling is 60-feet high, 25 feet taller than a typical cold storage facility. “Going vertical was very important, because there’s the same square footage on the roof but more storage space inside,” says Tom Dosch P.E., C&L project engineer. “Because the roof is the biggest source of heat and 90 percent of a cold storage facility’s energy bill comes from the refrigeration, having more storage without increasing the size of the roof reduces the overall power needs.”

Next steps

Innovative Cold Storage Enterprises Inc. (ICE), for which the facility was built operates another older cold storage building to which the new facility will be compared in terms of energy use. The new building is expected to store four times as much product at half the cost of ICE’s first building and will serve as a model for future buildings. Moreover, the facility is awaiting to attain gold certification from the U.S. Green Building Council’s Leadership in Energy and Environment Design (LEED) program.