Solar Cooling for a Cold Storage Facility
by Peter Powell | June 1, 2009 | Air Conditioning|Heating|Refrigeration News
There is only one thing you need to know about California: The state loves all things green — especially solar power.
Only thing is, when you are a refrigeration contractor, you can do green but how can you harness the hot sun and create cold?
Well, according to the folks at C&L Refrigeration of Brea, Calif., it can be done and they did it.
When a cold storage facility opened a few months ago in San Diego County, it was billed as “ground breaking in design, solar-powered and expected to lower energy costs by 75 percent,” according to a statement from those involved in the project.
The 135,000-square-foot cold storage building for a company called Innovative Cold Storage Enterprise was built to store such frozen foods as strawberries, chicken, prepared foods and other products.
In all, a 10-person design team and some 40 subcontractors were involved in the project. C&L was called in to deal with refrigeration challenges involving the building design, integration of the refrigeration system with solar panels, and handling wastewater generated from the refrigeration system.
The ceiling is 60-feet high, said to be 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,” said 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.”
C&L designed penthouses on the roof for the evaporators. In all there are eight evaporators at 420,000 Btuh or 35 tons each. The large size was by design. “Larger ones are used because it is more economical to install and operate with fewer evaporators,” said Ron Cassell P.E., company president.
He also noted that having the evaporators on the roof allows for easy access for maintenance.
The solar panels on the roof are used to provide the power for the refrigeration system during the hottest part of the day. The refrigeration control system, designed by C&L, is integrated with the solar panel control system. During the hottest part of the day, when energy is most expensive, the refrigeration output is lowered to meet the available power from the solar panels. This is accomplished by adjusting the frequency on the variable-speed drives of each compressor.
Cassell said it has been reported that approximately 72 percent of the energy needs for the structure are being met by the solar panels.
C&L designed a way to minimize the amount of water used from the cooling tower and devised a plan to store and use wastewater for irrigation, saving about 42,000 gallons of water each month, it was reported. The company designed a way to store the defrost water from the evaporators and use it to operate the building’s low-volume toilets.
“That may have never been done before,” said Cassell.
All the components of the project — from the taller building, to the solar panels, to the water system — were part of the efforts to make the project green, a major goal in California, which leads the nation in aggressive advocacy of such environmentally correct projects.
Yet another part of the green equation was the use of high efficiency screw compressors with ammonia as the refrigerant.
“Ammonia is the refrigerant of choice for green industrial projects,” said Cassell. “The ozone depletion potential and global warming potential are zero.”
The cold storage facility is one of many projects that C&L has been a part of during the last 30 years. The company is involved in engineering, construction, and maintenance of commercial and industrial air conditioning and refrigeration systems.
The project included a $225,000 financial incentive from San Diego Gas & Electric for energy-efficient features through the power company’s Sustainable Communities Program. It also is awaiting LEED Gold rating by the United States Green Building Council.
“There is a good future in green technology for industrial applications, and we’re committed to being a leader in that,” said Cassell.