Best Practice Guide

Food and Beverage Growers and Processors

Introduction

Planning an Energy Program

Funding and Approval

Commissioning

On-the-Farm Energy Use

Lighting

Building Envelope

Central HVAC System

Boilers

Steam

Combined Heat and Power

Compressed Air

Refrigeration

Energy Use Basics

Proper Maintenance

Proper Operations

Energy-Smart Investment

Motors

Demand Response

Distributed Generation

Water Use


Fetzer Vineyard

J Vineyards and Winery

Mission Foods

S. Martinelli and Company

Sara Lee

Vineyard 29


View the Glossary

Refrigeration

Energy Use Basics

Printer-friendly version

Share your thoughts

Energy use characteristics
Refrigeration and process cooling systems typically consume more electricity than any other industrial process, accounting for more than 25 percent of all electrical consumption among U.S. food processors. Almost all systems rely on conventional technologies similar to the refrigerator found in your home. However, the energy efficiency of these technologies has not significantly increased over the last few decades.

Cave events room at Vineyard 29. Photo courtest of Vineyard 29.View Details.

Besides process cooling, refrigeration systems are critical for cold storage. The United States has approximately 2.9 billion cubic feet (cu. ft) of cold storage, with total capacity increasing each year. Of this, California has the largest gross warehouse capacity, mainly for the agriculture and dairy sectors, but also to support the needs of several other industries and manufacturers. Among the U.S. pacific coast states, there are almost 310 million cu. ft. of cooler storage in public warehouses and 1.3 billion cu. ft. of freezer space.

Energy efficiency measures do more than just reduce utility bills. Several measures prolong the useful life of expensive capital assets such as condensers and compressors. Other measures might improve product quality, production efficiency or worker comfort. While the economic impact of these indirect benefits may be difficult to calculate, it is worth noting and reporting the results along with energy and cost savings.

How does a refrigerator work?

How does a refrigerator work?
The key to mechanical refrigeration is the continuous movement of a refrigerant between a hot side and a cold side. Most mechanical refrigeration systems consist of a compressor, an evaporator, a condenser, and an expansion valve. Of these, the compressor consumes the most energy.


Here's how it works: a (liquid) refrigerant moves through the evaporator coils; as ambient air passes over the coils, heat moves from the (warmer) air to the (cooler) refrigerant, causing the refrigerant to boil and vaporize. The air is now chilled and ready for use - this is where the "cooling" actually occurs. Water can be used in place of air, or a heat exchanger can be used in place of evaporator coils, but the process is basically the same.


But the story doesn't stop there. The refrigerant continues through the loop, now as a gas. Because refrigerants tend to have very low boiling points, it's temperature is still cold. The refrigerant next passes through a compressor that increases its pressure and temperature. As a high pressure, high temperature gas, the refrigerant is moves through the condenser coils. Ambient air is passed over the coils; heat from the (warmer) refrigerant is transferred to the (cooler) air, and rejected from the system. The refrigerant keeps moving, now as high pressure, high temperature liquid. The final stage is to pass the refrigerant through an expansion valve that drops the pressure, causing the refrigerant to return to a low temperature, low pressure liquid. From there, the cycle starts over.


Resources

Northwest Food Processors Association ENERGY PORTAL, online information on process efficiency for refrigeration and freezing.

Industrial Refrigeration Best Practices Guide. Prepared by Cascade Energy Engineering for the Northwest Food Processors Association and the Northwest Energy Efficiency Alliance.

The Industrial Refrigeration Consortium (IRC) is a collaborative effort between the University of Wisconsin Madison and industry. The goal of the IRC is to improve the safety, efficiency, and productivity of industrial refrigeration systems and technologies.

A Guide to Help You Reduce the Energy Use of Your Industrial Refrigeration System. Pacific Gas and Electric Company website.

Hochstein, A. Closing in on the Ideal: Door engineering that maximizes energy efficiency and handling productivity for today's cold storage facilities. Rite-Hite Corporation website.

Thermal Energy Storage Strategies for Commercial HVAC Systems. Application Note, Pacific Gas and Electric.

Northwest Food Processors Association Efficiency Practices and Emerging Technologies websites offer useful information and tips for the food processing industry.

California Energy Commission websites on Food and Fiber Processing Technologies and Energy in Agriculture.