Cold Storage Warehouses

Owners and managers of cold storage warehouses are often faced with minimizing their operating costs.  The energy used by the refrigeration system is often a major contibutor to this cost of operation.  In the attempt to limit the energy used and its subsequent cost various methods can be utilized.

One of the most common is the addition of new central control system.  Despite many claims, control systems simply function to turn equipment off or on.  Some of the more intelligent control systems process information based on weather, time-of-day, or take into consideration the part-load efficiency of the equipment being controlled.

Weather is one aspect no one has control over.  It is something you can only react to.  You cannot control how hot or cold the ambient temperatures are.  You can however configure the refrigeration system to be able to utilize the lower temperature periods to your advantage.

Part-load efficiency has multiple considerations:

1. The equipment will operate within its ability provided by the manufacturers design.  Various types compressors are often described by their ability to operate at partial loads.  This is often based on their normal operating speed.
2. Using variable frequency drives (VFD’s - often called inverters) provides the ability to modify the part-load operation of the equipment to gain increases in operating efficiencies.  Being able to control the equipment operating speed can provide closer control and also reduce energy cost.  This is accomplished by controlling the equipment performance envelope to meet the demands of the cooling requirements.
3. What impact does part-load operation have on energy use?

Time-of-day control should take into account the On-Peak and Off-Peak electricity rates and associated costs for those specific periods.  With this capability you can control when the equipment is operating and be able to control costs as suitable for your facility requirements.

An optimum goal is reached when the refrigeration system is configured and controlled to provide the lowest operating cost.  This approach requires the system to be able to react to the changes in weather conditions to take full advantage of low discharge pressure operation.  This promotes lower energy use (kWh) and demand (kW), when the refrigeration system is required to operate.  This can be further enhanced by having the ability to use cold weather for a free-cooling mode.  This may allow the compressors to be shut off, while the refrigeration system still provides cooling.

The refrigeration system should be optimally configured to operate in any weather condition.  Once this is accomplished the control system provides the ability to sustain the benefits of meeting the cooling requirements in the most efficient manner.

The final part of the story is this question: Are you controlling the refrigeration system to only operate during those periods when electricity rates are the lowest?  The time-of-use rates you pay for electricity may offer substantial benefits in cost reductions.

Tags: cold storage warehouse, control systems, free-cooling, inverters, part-load efficiency, refrigeration system

This entry was posted on Friday, June 26th, 2009 at 8:32 pm and is filed under Energy Use, cold storage warehouse, industrial refrigeration. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.