This frozen food case includes CO2 as the secondary heat transfer fluid.

In today’s competitive retail environment, companies are constantly looking for ways to improve their operations. They often partner with vendors and other outside resources to create solutions to pressing industry challenges such as energy conservation and environmental leadership.

Food Lion LLC, one of the largest supermarket companies in the United States, is currently working with Hill Phoenix, a designer and manufacturer of commercial refrigeration systems, to test and evaluate new refrigeration technologies that are said to be kinder to the environment and offer better sustainability benefits.

Food Lion is evaluating Second Nature® technologies from Hill Phoenix in two Virginia stores, one in Dinwiddie and the other in Montpelier. The Dinwiddie store is testing a medium-temperature secondary coolant system that uses water and glycol to refrigerate products. The Montpelier store is testing a low-temperature system featuring carbon dioxide (CO2), a naturally occurring gas, to refrigerate food products.

Both systems will be tested simultaneously in a Portsmouth, Va., location that is scheduled to open in early 2008.


According to the manufacturer, the Second Nature systems used in these tests were chosen because:

• They require less refrigerant, thus lessening the degree of global warming and ozone depletion.

• They raise suction temperatures without raising food temperatures, saving energy and protecting food shelf life.

• They reduce the amount of copper piping used, replacing it where applicable with ABS plastic piping. This saves energy spent during the copper smelting process and reduces the net weight of the installed material, as well as lowering the number of potential refrigerant leaks.

• They require less maintenance than traditional direct expansion (DX) systems.

Scott Martin, director of sustainable technologies for Hill Phoenix, said, “Food Lion is committed to using environmentally friendly and energy-saving technologies in their stores. Hill Phoenix also desires to produce the most energy-efficient, environmentally friendly refrigeration products in the industry. These two like-minded approaches are the driving force behind the testing of these green technologies,” Martin said.

“Food Lion believes that a critical aspect of serving our customers is to be a responsible corporate citizen. We take great pride in undertaking initiatives such as these, which will protect the environment and sustain the communities in which we operate for years to come,” said Glenn Dixon, Food Lion’s senior vice president of corporate development.

An outside consulting firm, VLE Enterprises of Pottsboro, Texas, is independently monitoring and measuring the impact on the environment, energy consumption, initial costs, maintenance expenses, and total cost of ownership expenses for all three stores.

At the conclusion of the evaluation, Food Lion management will report the findings to the U.S. Environmental Protection Agency (EPA) and conduct an internal review. The data will be shared with Hill Phoenix, and the next steps will be reviewed and proposed. If the results are good, the systems will be applied in more stores.


The medium-temperature system in Dinwiddie has refrigerated display cases and walk-in coolers and freezers that have been redesigned to benefit from the latest advances in secondary refrigerant technology.

Flooded evaporators provide better heat transfer and faster pulldown after defrost. The results provide for higher-quality food products through improved refrigeration and shelf life, Martin said.

This system replaces R-404A with a secondary fluid composed of water and 35-percent inhibited (food-grade) propylene glycol. This low-pressure chilled-water loop eliminates the circulation of high-pressure refrigerant throughout the sales floor and reduces the possibility of leaking refrigerant to the atmosphere, Martin said.

The ability to control product temperatures, as well as case temperatures, is another advantage, he said, particularly as it’s applied to medium-temperature applications such as meat, seafood, and produce cases. Temperature control is more stable because defrost time is equal to or less than other defrost methods, and defrost temperatures are significantly lower. Plus, there is reduced recovery time after defrost.

This helps ensure that the Food and Drug Administration’s (FDA’s) 41°F maximum product temperature is achieved, said Martin. Reduced shock and improved moisture removal also yield longer shelf life.

Because the medium-temperature secondary refrigerant (propylene glycol) is not under high pressure like the primary refrigerant is, Hill Phoenix used the Georg Fischer-engineered ABS plastic piping system for construction of the Dinwiddie store. Copper mining and smelting are large producers of greenhouse gases in the production of copper piping materials. The engineered ABS pipe used in Dinwiddie has an overall significantly lower environmental impact than copper. For example, it requires 36 percent more oil to produce copper than is required to produce the engineered ABS pipe.

In addition to its sustainability benefits, Hill Phoenix Second Nature systems help reduce maintenance costs up to 50 percent annually and provide equal energy efficiencies, Martin said. Additionally, ABS has a significantly lower thermal conductivity rate than copper and a greater wall thickness, making it a better insulator, he said. Both of these factors lead to lower energy losses through the engineered ABS plastic pipe. Finally, the plastic pipe is more easily recycled.


At the Montpelier store, Food Lion has applied an advanced low-temperature system that replaces R-404A throughout the store with CO2 as the secondary heat transfer fluid, at pressures equal to or less than typical R-404A DX systems, thus reducing the initial R-404A charge by 60 percent.

The sustainability of ongoing savings that will result from the elimination of refrigerant outside the machine room and the subsequent leaks that occur over time will be equivalent to 1,621 tons of carbon emissions over 10 years, officials predicted.

An integral part of the systems are the cases that feature evaporator coils specially designed to use CO2 as the secondary coolant. This Second Nature Advanced LT system pumps CO2 as a secondary refrigerant through the store to remove heat from display cases and walk-in freezers.

Heat is absorbed in the display case through coils similar to those used in common DX systems. The CO2 does not completely evaporate in the coil, the manufacturer said; it is returned to a separator as a mixture of liquid and vapor. The liquid portion is available to be pumped from the separator back to the cases; the vapor portion returns to the condenser-evaporator heat exchanger to be condensed back into a liquid. At this point, heat absorbed in the display cases is transferred from the secondary system to the primary system and rejected outside.

Martin said the benefits of using CO2 as the heat transfer fluid in this design include the fact that it is a natural component of the environment. CO2 is inexpensive with an extensive distribution network.

“It has excellent thermodynamic and transport properties and good material compatibility,” Martin said. The cooling effect is based on latent heat capacity and results in lower flow rates when compared to other low-temperature secondary fluids.

The system is also coupled to a heat reclaim system designed to recover 50 percent of the refrigeration system’s waste heat, then use it to heat potable water in the store. By capturing the waste heat of the store’s low-temperature refrigeration systems, natural gas usage will be reduced, Martin said.

The use of CO2 in this store allows a 21 percent reduction in lineal footage of installed copper and a 50 percent reduction in the weight of installed copper pipe vs. a comparable installed DX system. With fewer connections and valves requiring adjustments, such as thermostatic expansion valves and evaporator pressure regulators, system control is simplified.

Food Lion is owned by Brussels-based Delhaize Group. For more information, visit

Publication date:05/07/2007