5 ways to maximize refrigeration efficiency
Proper maintenance is key according to BC Hydro expert
Most people think of the summer as the most relaxing time of the year. But if your business relies on a refrigeration system, summer is likely the toughest time of the year.
So as the temperature picks up, we spoke to Zaid Al-Chalabi, an Energy Management Consultant with BC Hydro, to see what refrigeration tips he has for a long, cool, energy-efficient summer.
"Properly maintaining your equipment is obviously important to avoid repairs," says Zaid. "But if you regularly check settings and calibrate instruments, your refrigeration system will run more efficiently for longer and save you money."
Here are five areas Zaid recommends reviewing:
1. Reduce refrigeration system lift
Lift is the difference between suction pressure (or evaporator temperature) and discharge pressure (or condensing temperature). Your compressor is constantly working to sustain whatever lift your set up has determined. So if you can reduce your lift, you'll increase your compressor efficiency.
As a rule of thumb, you can expect:
- up to 1.5% compressor power savings per one degree Fahrenheit decrease in condensing temperature.
- up to 2% savings per one degree Fahrenheit increase in evaporator temperature.
2. Improve part load system performance
"It's worth remembering that most refrigeration equipment is designed to run at peak all the time," says Zaid. "But in reality, most refrigeration systems only run at part load for most of the time – which is very inefficient. So to maximize your savings, avoid part load operation of your refrigeration equipment."
- Evaporators: Try upgrading your controls to cycle evaporator fans on and off based on your space temperature. Alternatively, installing variable speed drives will automatically reduce the speed of the fans.
- Compressors: Avoid running all compressors at part load by using a fixed speed compressor running at peak to meet your base load. Then a use a secondary variable speed compressor to cover the trim. "If your base load compressor is turning on and off frequently," says Zaid, "it'll be more expensive to run and have a shorter lifespan."
- Condensers: Prevent over-condensing by upgrading your controls with a wet-bulb approach algorithm instead of using a target condensing pressure.
Zaid explains: "Instead of having one target pressure that the condenser is trying to achieve, it uses the ambient temperature. So if it's really cold outside, like at night, for example, your condenser doesn't need to be working as hard and it'll respond to that ambient temperature."
Variable speed drives on fans will also automatically reduce the fan speed and enable floating head pressure control.
3. Upgrade refrigeration system equipment
Along with introducing upgraded controls and variable speed drives, you can also make significant efficiency improvements by upgrading various other components, beginning with looking at the most common ones:
- Coils: Installing oversized coils will enable your evaporators to increase the heat exchange surface.
- Hot gas defrost: Try replacing electric defrost with hot gas defrost, which uses the heat vapour from the compressor discharge to warm the coil and melt the ice.
- High performance water spray nozzles: Even simple things like nozzles for your evaporative condenser can make a big difference. They're easy to check, clean and replace.
- Compressor oil cooling: Using a thermosiphon circuit or other external cooling for screw compressors can noticeably improve performance.
- New fan blades: Replacing old fan blades with high performance blades can reduce fan motor power by up to 20%. That's because new blades are more aerodynamic and weigh less, while older blades may also be cracked and clogged with dirt.
- Computer controlled system: Human error is a huge part of inefficiency. A computerized control system will not only solve this, it'll also provide visibility into your system's performance, helping with operations and maintenance. Plus, you'll be able to control and monitor everything remotely, track usage, gather analytics data, get alerts, and determine set points or parameters.
4. Reduce refrigeration loads
In Zaid's experience, many customers understand that the higher their refrigeration load, then the higher their energy use will be. They also understand that reducing unnecessary heat loads in refrigerated spaces will reduce your overall refrigeration system energy use. But what most customers don't realize is that the biggest impact on heat load isn't what you store in the refrigerated space – it's actually the building envelope and space lighting.
So, along with checking your system, be sure to also review the following:
- Insulation: Increase insulation in the roof and walls wherever you can.
- Doors: Repair any inadequate door seals and consider installing high speed doors to reduce infiltration.
- LED lighting: Apart from using much less electricity and requiring less maintenance, LED lighting and occupancy sensors can dramatically reduce the heat generated by HID type lighting fixtures.
5. Maintain your refrigeration system equipment
As we mentioned at the beginning, not maintaining your refrigeration equipment will impact its performance. Having a proper operations and maintenance plan means a longer lifecycle and increased efficiency. So talk to your team and create a plan for regularly checking these areas:
- Heat exchangers: Inspect and clean heat exchangers (such as the evaporator and condenser coils) regularly.
- Non-condensable gas: Test for and eliminate non-condensable gas from your system by using an auto-purger.
- Water spray coverage: Check for proper water spray coverage across your condenser heat exchanger surface. This includes your nozzles, as mentioned earlier.
- Calibration: Set a regular schedule for calibrating pressure sensors, temperature probes and compressor slide valves.
- Contamination: Prevent condenser water contamination with a proactive water treatment approach.
- Training: Regularly review the optimum key set points and operational strategies for your system.
Concerned about your refrigeration system?
As you can see, just because your refrigeration system is running inefficiently, it doesn't necessarily mean you need a new one. There are many things you can do to improve your current system. If you're not sure where to start, begin by talking to your Key Account Manager or Regional Energy Manager.
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And of course, BC Hydro is here to help. Reach out to your Key Account Manager or Regional Energy Manager if you have any questions or concerns.