By Bob Zak
Increasing competition and a slow economy have most cold food processors and cold warehouse operators scrutinizing operations for cost-cutting opportunities. However, many companies miss significant potential savings in a major cost area: electrical power.
Electrical power comprises 4 to 7 percent of refrigerated and frozen food per-unit costs and – for cold storage warehouses – it is the second highest cost after labor. The solution is advanced technology that allows facilities to shave costs more effectively without compromising food safety and quality or causing unanticipated disruptions.
Count the costs
To pare power costs to an absolute minimum, it’s essential to understand all utility charges and tailor savings strategies to them in a way that best suits your facility. Utility charges may include:
Usage rate. This is the total amount of power consumed. Costs normally range from $0.07 to $0.20 per kWh.
Demand charge. This is based on an operator’s highest peak power consumption in any given month, usually measured in 15-minute increments. For many processors and warehouses, demand charges have become as high as usage rates on the bill..
Time-of-use (TOU) charge. Your utility may charge three to five times the normal usage rate during a fixed time period every day.
Dynamic or real-time pricing (RTP). Power is often traded like a commodity in an open market, and some utilities offer potentially beneficial rates that follow trading indexes in real time. That means your facility’s power costs may vary throughout the day, running from much lower – to much higher than normal. In worst-case examples, power costs have jumped during an RTP spike to more than 100 times the normal rate.
Advanced energy management systems (EMS) help operators keep total electricity costs as low as possible. Manual actions increase the risk of operator error. Moreover, employees cannot optimize loads around the clock – nor can they effectively coordinate fine adjustments in real time throughout an entire facility.
On the other hand, an advanced EMS constantly monitors power use and makes adjustments. Ultimately, this not only reduces energy costs but it also helps maintain and enhance food safety and production efficiency. Importantly, operators can install and integrate these new technologies with their existing control systems.
Operators may use these technologies to cut costs and even generate income. Here are a few examples.
Execute meaningful peak demand control. Achieving maximum savings requires monitoring and adjusting electrical loads throughout an entire facility, not just for the refrigeration systems.
To do this, you need an EMS that can monitor all incoming electrical power (sometimes at multiple meters), make decisions for the entire facility, and then implement demand control or energy efficiency measures that reduce the total energy cost across the entire facility. A rule-based control structure allows you to adjust the set -points according to how aggressively you want to curtail loads, while ensuring these actions are not disruptive to the plant.
Respond to utility TOU or RTP rates. An advanced EMS will allow you to reduce consumption during short-duration, high-cost billing periods by monitoring the meters, tracking to the rate situation, and executing the necessary actions.
For a food processor, reacting quickly without compromising production or minimum temperatures is a challenge, so it is imperative that the EMS consider the entire facility’s electrical loads for reduction. A cold storage facility has more flexibility because refrigeration requirements change slowly due to the cold sink created by a dense mass of frozen product, known as the “large flywheel effect.”
Generate revenue by participating in a demand response program. These incentive programs, available in many regions, pay you for significantly reducing consumption upon request when your grid operator is experiencing unusually high demand. Most cold storage and processing facilities find it impossible to participate in these programs by making manual adjustments.
This strategy is particularly well suited to facilities with large cold spaces because they benefit from the large flywheel effect. In any case, an advanced EMS is pretty much essential to enable most facilities to reliably shed the amount of power requested for the time required (usually two to six hours) while tightly controlling any impact to production and food safety.
Upgrade energy efficiency of refrigeration systems. Most facilities have opportunities to save on electricity costs by improving the operation of the heaviest power user in a food processing plant or cold storage warehouse: the refrigeration system.
Facility operators should consider these upgrades:
- Install variable frequency drives (VFDs) on fans and pumps. Varying the speed decreases capacity proportionally but decreases power by a cube function (e.g., 50 percent speed equals 50 percent capacity equals 12.5 percent power requirement).
- Install VFDs on compressors, because screw compressors do not unload efficiently without them.
- Stage and sequence multi-compressor engine rooms for savings (i.e., match compressor capacity to the refrigeration load).
- Better match interdependent compressor and condenser fan horsepower with floating head pressure control for maximum savings.
- Initiate and terminate evaporator defrosts for maximum efficiency. You can do this by using liquid solenoid on-time, a temperature delta across a coil, or infrared sensors.
Some utilities offer grants or low-interest loans to increase the efficiency of refrigeration and other subsystems, such as compressed air and hydraulic systems.
Selecting advanced EMS
To achieve maximum energy savings, you need an advanced EMS that’s powerful and flexible, can control your entire facility, and fully automates load curtailment. Here are the key features to look for:
- Highly accurate temperature monitoring capability (constraints on curtailments will often be temperature based);
- Wireless technology to transfer information efficiently and minimize installation costs;
- A Web-based architecture for connectivity to a plant from any remote location;
- Adaptive demand set-points to increase savings in a fluid production environment while keeping curtailment actions to the minimum;
- Capability to embed operator intelligence so that plant personnel can drive automated decision making according to your facility’s needs;
- Reporting capabilities that provide accurate energy and operating feedback and detail savings
Refrigerated and frozen food processors and cold storage warehouses are increasingly challenged to drive down costs, meet strict requirements for food safety, and reduce their environmental footprint. The good news is, these are challenges you can meet: with advanced energy management technology, you not only can survive, but thrive, in the marketplace.
Bob Zak is president and general manager of Powerit Solutions North America (www.poweritsolutions.com), a cleantech company that plugs energy-intensive businesses into the smart grid. In 2009, Zak’s Seattle company was named one of the world’s top 100 cleantech firms and SmartGridNews.com’s readers voted Powerit as one of 10 smart grid “companies to watch.”
Tech Talk: Reduce, time energy use; integrate solar
Everyone needs balance. That’s why cold facility operators need flexible energy management tools to address more stringent utility company rate structures.
And that’s why Hench Control, Hercules, Calif., says it has expanded its focus beyond energy efficiency (a permanent reduction of energy demand) to include new “demand-response” options that reduce a cold building’s energy demand temporarily during critical peak periods.
“Demand-response is becoming more of a focus and priority for utility companies based on the total kilowatts available in the U.S. power grid,” says Matt Chang, Hench vice president of sales and marketing. “Their objective is not to build new power plants … Hence, they are looking to better allocate and conserve what they have available to them.”
Although it’s easy to turn equipment off completely during peak demand times, it takes more intelligent software to maintain critical refrigeration system components and manage them while complying with demand response. He says Hench developed algorithms that account for these situations and others.
“These extensive and complex algorithms reduce energy usage by changing set points, which allow the Hench system to turn off ‘energy hogs’ when power use or energy price is high,” Chang says.
“Conversely, this also enables the lowering of temperature in cold rooms when power use or energy price is low.”
Hench’s load-shedding program changes set points based on a certain control value. That control value can be current kW (power usage), price per kW, demand charges, day and time, or a combination of any or all four.
Chang says the energy management system also can utilize demand charges, real-time pricing and current kW. In this situation, there is a peak demand table downloaded monthly, which has the agreed upon peak demand charges for every hour of every day for the month. Real-time pricing tables are updated every five minutes. If current kW is below the agreed upon peak demand, the system will control on the real-time pricing table. If the current kW is above the agreed upon peak demand, then the system will control on the current kW to get the demand down.
Chang says his company’s latest offering is hcSolar, a program that connects any facility’s solar panel technologies and power into Hench’s predictive, adaptive EMS program.
“The program interfaces with the solar production to make educated decisions on how to best maximize the additional energy relative to the demand/load for food processing facilities and cold storage warehouses,” says Chang. “The end result of both Hench and solar systems working together make facilities and warehouses independent of the grid during peak demand times and will generate an even higher percentage of avoided costs at high demand times.”
Tech Talk: Detect frost, control blast cell evaporator fans
They say rust never sleeps. Unfortunately, the same could be said of energy costs. That’s why suppliers such as Logix, Kirkland, Wash., keep exploring new angles in energy management. For example, some of the firm’s latest research involves everything frost detection systems to blast cell evaporator fan controls.
Jim Conant is Logix president and co-founder.
“Energy costs are headed north,” he says. “Many utilities are seeking rate increases (as high as 23 percent in some cases) and others are adding demand and peak rate charges. Many clients are asking for custom-tailored load management features that specifically address their rate structures. Because rate structures also vary nationwide, our solutions are diverse as well.”
One broad industry solution involves Logix’s work with blast cell evaporator fan controls.
“A large portion of the energy used in a blast freezing cycle is associated with fan operation,” Conant notes. “However, studies show that much of this fan energy is not achieving any useful work (product freezing). This is due to the somewhat slow rate of heat migration out of the product, which can’t keep pace with the surrounding refrigeration.”
Conant says Logix’s approach involves a schedule that cycles fixed-speed fans or that gradually reduces variable frequency drive speeds over the term of the freezing cycle. The result is that fan energy waste is abated with minimal (or even reduced) effect on blast duration.
Logix also is conducting beta tests involving a new frost detection system to control freezer evaporator defrost cycles.
“This technology reduces evaporator defrost frequency and associated energy costs,” says Conant. “In many cases, we’re reducing defrost cycles to just one or less per day – down from as many as four cycles per day. In fact, we’re often seeing just one defrost per three to seven days in a cold storage setting. The typical warehouse with a 500-ton refrigeration system uses more than a quarter of a million kWh’s annually with conventionally-controlled defrost. On average, our frost detector can at least halve that energy cost . . . Once our technology is fully field tested, we plan to make it available commercially to the industrial refrigeration market.”