Evaporator Fan VFD Initiative

Background

In 1997, Cascade Energy Engineering recognized that evaporator fan variable frequency drives (VFDs) represented a tremendous energy efficiency opportunity in industrial refrigeration facilities. Cascade had worked with several pioneering facilities that were among the first to try this technology. These early adopters battled through a few problems, but were very satisfied with the energy savings and performance of evaporator fan VFDs.

Despite these early successes, the market for evaporator fan VFDs was in its infancy - only about 5% of the industrial refrigeration evaporators in the Northwest had been equipped with VFDs. In addition to the newness of the technology, Cascade identified other market barriers that were preventing rapid acceptance of this technology.

The Northwest Energy Efficiency Alliance

Cascade approached the Northwest Energy Efficiency Alliance with a proposal to both accelerate and magnify the implementation of evaporator fan VFDs in refrigerated warehouses. In early 1998, the Alliance contracted with Cascade to operate the “Evaporator Fan VFD Initiative” for the purposes of promoting this technology and addressing the identified market barriers.

The Northwest Energy Efficiency Alliance (website:http://www.nwalliance.org/) is a consortium of Northwest electric utilities, Bonneville Power Administration, state governments, and industrial and consumer representatives. The Alliance is chartered to promote market transformation of energy efficiency electrical products and services. The Alliance territory encompasses Washington, Oregon, Idaho, and Montana.

Field Trials

The central element of the Evaporator Fan VFD Initiative was a significant effort to recruit refrigerated warehouses to try the technology on at least a limited basis as a field trial. The intent of the field trials was to give facility owners and operators firsthand experience with VFDs and to use these VFDs as a laboratory for fruit quality research. Several types of field trials were conducted.

Controlled Atmosphere Storage Field Trials

These field trials involved room to room comparisons of energy use and fruit quality in Washington commercial apple controlled atmosphere (CA) rooms. These trials were conducted for the 1998-99 season and the 1999-2000 season. A total of 10 sites participated in the first year tests and a total of six sites participated in the 2000.

At each test site, two similar CA rooms were selected. A VFD was installed for one room with the other room being a control room for comparison. To provide a comparison versus the status quo, the control room used the fan control strategy normally employed at that facility. In many cases, the fans operated continuously in the control room. The other control rooms used evaporator fan cycling with various degrees of aggressiveness. At a given facility, the test rooms were identical in terms of room dimensions, bin stacking pattern, fruit variety, refrigeration equipment, and storage conditions.

The tests were season long comparisons. The two rooms were loaded with fruit (either simultaneously or sequentially) during harvest in September or October. The rooms were unloaded in a similar time frame typically in the spring.

Common Storage Field Trials

Field trials were also conducted in the broader industrial refrigeration market. These installations typically were larger and were located in cold storage facilities and distribution centers. Unlike the CA installations, the cold storage field trials focused primarily on energy performance and overall system performance. There was less of an emphasis on product quality issues. In some cases, they were comprehensive installations of evaporator fan VFDs for entire facilities.

Study Results

Test results are organized by application below.

Evaporator Fan VFD Case Study Summaries

The controlled atmosphere summary provides an overview of all the 1998 case studies. The regular storage summary provides an overview of all six common storage field trials.

Summary of Controlled Atmosphere Field Trials (pdf format)
Summary of Common Storage Field Trials (pdf format)

Detailed Controlled Atmosphere Field Trials

These field trials included both fruit quality evaluation, detailed environmental monitoring, and evaporator fan power monitoring. The three detailed tests all were conducted in rooms that stored golden delicious apples.

Stemilt Growers Detailed Field Trial (pdf format) - Includes temperature, humidity, and real time mass loss for a tight stacked room.
Trout Blue Chelan Detailed Field Trial (pdf format) - Includes temperature, humidity, and real time mass loss for a conventionally stacked room.
McDougall and Sons Detailed Field Trial (pdf format) - Includes monitoring to detect gradient in carbon dioxide and oxygen within rooms.
Braeburn Research Room Field Trial (COMING SOON) - Includes a three room comparison of four Braeburn lots as well as carbon dioxide monitoring. The test was conducted in small 40 bin research rooms located at Stemilt Growers.

Simple Field Trial Case Studies

These field trials included fruit quality evaluation and evaporator fan power monitoring.

Golden Delicious

Columbia Reach Pack (pdf format)
Hansen Fruit (pdf format)
CM Holtzinger Fruit (pdf format)
Magi (pdf format)

Red Delicious

Stemilt Growers (pdf format)
Olympic Fruit (pdf format)
Valley Fruit (pdf format)
Larson Fruit (pdf format)

D'anjou Pears

Blue Star Growers - Bin Fruit (pdf format)
Blue Bird - Packed Fruit (pdf format)

Brochures

Controlled Atmosphere Evaporator Fan VFDs (pdf format)
Cold Storage Evaporator Fan VFDs (pdf format)
Evaporator Fan VFDs (pdf format)