As energy costs rise, refrigeration and freezing equipment makers are responding with more energy-efficient equipment. At the same time, work is under way on such technologies as waste heat conversion, and government regulations are beginning to appear.
Refrigeration and freezing would seem to be fairly sedate parts of the food business, but they can affect the profitability of an entire enterprise. Much of the reason for this is that they’re energy-intensive: a 1998 report from the American Council for an Energy-Efficient Economy (ACEEE) entitled “Energy Usage in the Food Industry” estimated that process cooling and refrigeration accounted for about 16% of total energy inputs in the food processing industry. And the price of energy is on a long-term upward trend.
In response, refrigeration and freezing equipment manufacturers are working on ways to increase energy efficiency, research organizations are studying ways to save energy, and government regulations are starting to appear.
Changes to equipment
One example of a manufacturer taking steps to improve the energy efficiency of its products is FMC Food Tech. Todd Middleton, North American director of sales and sales support, reports that the company has taken several approaches. One is the LVS (low volume system) feed system, which reduces the volume of ammonia charge overall in the system and results in a dry suction return to the engine room. “Whenever you have a dry suction return that reduces the pressure loss in the suction pipe, the result is increased efficiency at a given temperature or reduced temperature,” says Middleton. The method can have another benefit as well, he continues. “Because it reduces the refrigerant charge, often it will take you below the limits at which you’re required to have a process safety management plan, which is an expensive undertaking.”
FMC Food Tech also has some new approaches to frost management, including putting fans on the dry (downstream) side of evaporator coils so they don’t accumulate so much frost (Fig. 1) and using blasts of steam or air to consolidate or dislodge frost. Slowing the rate of frost buildup improves heat transfer and energy efficiency and also allows the equipment to run longer between defrost cycles.
Lynn Burge, advertising and promotions manager for Master-Bilt, says that the adoption of electronic control systems (Fig. 2) can make for greater efficiency in equipment. “Controllers give the accurate data on food temperatures and analysis of service issues required by foodservice operators today,” he says. Another feature that helps save energy, he adds, is demand defrost.
The comprehensive energy bill, awaiting the president’s signature at the time of this writing, requires the establishment of efficiency standards for commercial refrigerators and freezers. In April, the Air-Conditioning and Refrigeration Institute and the ACEEE estimated that these changes, if enacted, would avoid the need for two new 300 MW power plants. It’s worthwhile to note that the legislation covers commercial, but not industrial equipment — probably because commercial installations outnumber industrial ones, and could thus account for more energy savings, suggests Todd Middleton. But it’s a good bet that efforts will be made in coming years to develop similar requirements for industrial refrigeration and freezing equipment, so it would probably be wise for both manufacturers and users of this equipment to begin preparations, not only to get ahead of future regulations but to save money today.
Simple ways to save energy
There are some simple ways to save energy that require little up-front investment, and pay for themselves in a reasonable time. Here are some suggestions from Western's Energy Services, a division of Western Area Power Administration, a Department of Energy agency:
• Choose high-efficiency motors to operate fans for both evaporators and condensers.
• Use speed controls on evaporator fans that will reduce their speed when full capacity is not required.
• Choose floating head pressure controls that allow head pressure to vary with ambient temperature.
• Check that defrost is conducted when needed, rather than on a set schedule.
• Make sure that the defrosting methods used are the most energy-efficient available.
These changes are not difficult for manufacturers to incorporate into products, and several of them can also be retrofitted to existing equipment. It makes good sense to adopt a policy of replacing failed motors with NEMA Premium Efficiency motors, and it’s not really a big step to put variable speed drives on fans. Fixed-speed installations are generally designed to run the fan at a speed that will handle the greatest load it will ever see; since the power used by a fan is proportional to the square of its speed, slowing the fan down under conditions of less than full load can save considerable energy. Suppliers of adjustable-speed drives can assist calculating payback times.
Incremental improvements can help with energy bills, but there are some sections of the food industry that could benefit from more radical changes. One example of a technology that seems to hold promise for energy savings for food processors is CHP (combined heat and power). The idea behind CHP is that electricity from the grid can, in some cases, be replaced with electricity generated on-site using natural gas or other fuels, and that waste heat from the generation process (as well as from other parts of the facility) can be captured and put to work in areas such as powering absorption-type refrigeration equipment. It has been estimated that adoption of this technology by food processors in California’s Central Valley can save about 1.5 million kWh per year and 300 kW of demand, resulting in about $123,000 of annual saving. This project is expected to reduce 15 MW of load during summer if it is adopted by 50 food processing plants across the food industry, according to Oak Ridge Labs.