As an operator of a refrigerated premises you will already appreciate that they are an energy intensive piece of business hardware.
Increasing your cool room and freezer room efficiency has an immediate and direct effect on your financial bottom line by reducing daily expenditure on services.
Small systemic changes can also improve product quality, reduce down time and enhance safe operation. Caring or your bottom line is also good for the environment and reduces your facilities environmental footprint.
1. MONITOR ENERGY USAGE.
Understanding and trending what your system is suing now and at high demand creates an awareness. This provides the tools to plan for any future energy requirements. A monitoring system installed in the upstream power supply of the refrigeration system allows the cause and effects of disruptions to be visualised, monitored and controlled by you and your staff.
Monitoring your refrigeration systems natural and seasonal cycles allows you to detect the warning signs of failure earlier. If your system starts requiring more energy than normal there may be a refrigerant leak, faulty component, failed door hardware allowing ambient, operator error or defrost issues.
Are you receiving “hot” product from other departments or customers. Cooling is expensive for everyone in the cold chain from manufacturing, transport and storage. The shipping of “hot” product shifts the costs to the next link in the chain.
Is that you and can you afford the cost of the goodwill?
2. DOOR MANAGEMENT.
The day to day management of the door use is arguably the single greatest impact influencing the running costs after the fixed factors of insulation and plant design.
Ambient air outside your room is laden with moisture and energy. The air inside of your facility is relatively dry and it is this difference in relative moisture levels that is a key driver of air and energy exchange.
The warmer the ambient air the greater the amount of water vapour the air can hold.
- Air at +4°c, 50% RH hold 2.50 g of moisture for every 1 kg of air.
- Air at 20°c, 50% RH hold 7.26 g of moisture for every 1 kg of air. (Almost 3 times more)
- Air at 30°c, 50% RH hold 13.30 g of moisture for every 1 kg of air. (Almost 6 times more)
When you first open a door, inertia is on your side and a relatively small air exchange may take place. However it only takes approximately 20 seconds for fully developed in / out air velocities to become established. This is the situation easily found anywhere there is regular forklift traffic.
High levels of air leakage may cause optimal temperatures to be exceeded, loss of stock and increases the required running times of the system.
All of this moisture eventually collects on the cooler (evaporator) in the form of water droplets, frost or ice. When a frost / ice accumulation becomes too thick, it acts as insulation and reduces the cooling capacity ensuring a longer run time to make temperature. Moisture will also condense or freezer on the first, sufficiently cold surface it makes contact with. This includes walls, floors, fittings and fixtures. In freezer rooms, this may produce significant ice safety and product spoilage issues.
See also Temperature & Defrost below.
Actions to consider:
- Close the door – Staff training and awareness, signage, indicating lights and alarms.
- Door Curtains – Do you have them and are they in good condition? Although not universally loved by all operators, they remain the single most cost effective barrier.
- Door Seals – Do they seal or are they just for show? Does the door need adjusting or gaskets replaced? Easy to check! Go inside your coolroom or freezer room and turn off the inside lights. If you can see daylight past the gaskets your require refrigeration maintenance action. If you are accumulating sheets of ice in front and around the freezer door, you require refrigeration maintenance action. Door seals come in various shapes and effectiveness from simple blade wiper styles to gas tight ripening doors.
- Install an automatic forklift door to improve management, speed and safety.
- Install a dedicated personnel door within or next to your wide and tall forklift door.
- Consider automated rapid open / close refrigeration door systems.
3. AIR FLOW.
Air circulation around the walls and product is critical for the system operation and the maintenance of product quality. The circulating air is the vehicle that intercepts the heat energy filtering through the insulated wall from the packaged product that generates internal heat of respiration ripening or was “hot” loaded.
Leave some spaces between stock so maximum air circulation can flow around the packages. Stacking of product against the wall means that infiltrating wall heat can cause warm spits on and within your product. This includes the floor where a pallet provides significantly better temperature control tan slop sheets for storage applications.
Make sure that product or poorly placed fixtures (such as lights) are not blocking any fan outlets or evaporator returns.
4. TEMPERATURE MANAGEMENT.
Most modern digital thermostats contain a huge number of variables for the humble refrigeration technician to choose from to tailor the installation to your special circumstances.
SENSING AND SET POINT:
Are your temperature gauges and controls calibrated and accurate?
Are you cooling your product?
Did you know a +2°c cool room uses measurably more energy then a +4°c cool room?
A simple check is to place the room temperature sensor in a small container of ice water for 5 minutes and observe the result. The display should ideally be 0°c, ±0.5°c. If your display only shows whole numbers then look for 0°c or ±1°c. Make sure your sensor is water proof or carefully wrap in a plastic sleeve and allow a longer time to stabilise. If the sensor is reading less than 0°c your room might be running warm, and if it is reading more then 0°c your room might be running too cold. Add a test and calibration checkpoint to your next service schedule.
The temperature differential is the distance between the temperature the refrigeration service switches off and when it switch on. This temperature generally varies between 2°c for smaller rooms and 0.5°c for larger facilities. If the setting is too wide then you might see wide fluctuations in the cool room storage quality and product life as the product moves between extremes. Set too narrow and you might experience short cycling of the refrigeration equipment resulting in higher running costs, increased motor stress and refrigeration maintenance.
Setting a defrost is all about knowing the sweet spot for your particular business and it is worth the effort of discovering the ‘Goldilocks’ effect.
It is prudent to only run the number of defrosts you need for the time that is required. Current generation systems generally use adaptive defrost management that respond to system demands. Older systems were often based on time start and stop for the worst case scenario. You do not want to be defrosting your cool room for too long since once a cooling coil is clear, any additional heat energy used for defrost is wasted.
You do not want your defrost running too hot either. If water created from a defrost cycle turns to steam, then when the evaporator turns back on, it could be thrown around the room to form wet spots, ice formations or deposit on product packaging.
Conversely if your defrosts are too short or too cold, it is simply not going to be effective. Under this scenario, the next defrost may be triggered earlier and the refrigeration service is operating in a permanently low efficiency state with insulated cooling heat exchangers and strangled compressor systems.
With the possible exception of some “off-cycle” defrosts, any time defrosting is time lost to providing cooling and this time needs to be caught up. If energy recovery systems are not used then this defrost effort is another expense.
Having your defrost professionally investigated as part of your routine refrigeration maintenance schedules ensures that not only it it functioning correctly, but also ensure that the operation can be amended to suit seasonal weather and business cycles.
6. MANUAL HANDLING AND PRODUCT MANAGEMENT.
This topic works hand in hand with door management since the efficient access to product is likely to have significant impact on how your doors are operated. Clear signage with simple loading and unloading policies like high turnover items with the cleanest access; vertical racking to minimise pallet stacking and shuffling, long term storage to the rear.
Do you have multiple rooms and can they be segregated into targeting best use?
Are you holding mixtures of product such as tomato, avocado, lettuce?
Do they all have different optimum temperatures, some warmer (cheaper) than others?
Keeping your cool or freezer room as full as possible is more efficient then running a half full or near empty cool room since the volume of free air space within the facility is less. Manipulating the strategic and reasonable advantages of the product thermal mass may allow you to shift some of the run time to a lower power tariff or to times when you can access the full solar power generation benefits to offset external energy requirements.
Have you considered a LEAN culture review where all facets of the loading and storage operate are put under the microscope?
7. LIGHTING THE ROOM.
A natural by-product of artificial lighting is heat. If your facility has too many lights or the wrong lights installed, you may be increasing the cooling demand by more than you realise. Recent advances in low temperature LED lamps can have a significant and measurable impact on cooling demand since the waste heat / lumen factors are very low. It is also worth considering an automatic movement sensor that shows when the room is not being or an after-hours time clock so the lights are off when not needed.
A little love and maintenance by ensuring your lights retain an effective upstream vapour barrier stops moisture forming in your fittings. This ensures safe operation and longer trouble free operation.
8. HOW EFFECTIVE ARE YOUR EXISTING SYSTEM CONTROLS.
Not all significant changes require a large investment. Some cool rooms and freezer rooms are not working optimally simply because the old electro0mechanical controls to operate the system are sometimes 10 or 20 years old. Older mechanical thermostats and defrost mechanisms with the albeit mostly reliable but unsophisticated control methods can be a big contributor to your power bills. upgrading to a digital controller can be a simple solution with a short return on investment, whilst also improving the system visibility.
A modern digital controller brings many of the room operating variables to one simple, convenient location and at your fingertips. Room temperatures and defrosting variables can be displayed in real-time, providing for a greater depth of information and education than was possible previously.
The old adage of “knowledge is power” can now be adjusted to read “knowledge is less power consumed”.
9. TYPES OF REFRIGERANTS.
There are a multitude of refrigerants in the market and each category of refrigerant is suitable only for a specific range of applications. Certain types of refrigerants use less energy and have less of an impact on the environment than others.
Refrigerants are generally known by their “R” ground number, i.e. R22, R134A, R404A, R410A, R502 etc. However this hasn’t stopped various enterprising marketers from creating their own “special” blends and some care and diligence is required to sort out the genuine contenders from the snake oil merchants.
If you have an existing system with an older style refrigerant such as R22, R502 and R12 it is recommended that you should be talking to your refrigeration service technician to determine in advance the bet alternate refrigerant and lubricant combination for your system. You should also be aware that for systems using R22 as a refrigerant, R-22 is now a restricted refrigerant and destined to be completely phased out by 2030. Significant import restrictions applied as of January 2016. Read more about R22 here.
It is prudent to advise your company insurance agent or broker when considering a change to an alternate refrigerant since some contain elements that may impact on premiums including propane (R290) and Isobutane (R600a) amongst others. Ensure that you receive notification and current MSDS, in writing, from your refrigeration service agent describing the refrigerant and quantity proposed.
10. HEAT RECOVERY.
A refrigeration system can be considered as a heat pump moving energy from a closed insulated box to an external environment looking to establish equilibrium.
You can recycle some of the heat from your refrigeration or freezer systems and utilise this to heat fluids or air. This is achieved by installing an auxillary heat exchanger between the refrigeration compressor and the standard condenser rejecting heat to the environment. Typical applications include pre-heaters of hot water services. If a hot water service needed to produce for example 85°c water, then pre-heating the water using “waste” heat might accomodate up to 50% of the energy required. Systems include inline heating or collection in a central storage tank. Refrigeration systems using water defrost can also benefit from this closed loop energy process.
During winter, condenser heat might redirect to an internal heat exchanger to provide heating for manufacturing and process personnel and directed outside in summer.
11. BONUS COMMENTS!
PLAN YOUR REFRIGERATION MAINTENANCE.
Over the medium to longer period of your equipments’ service life having a programmed maintenance schedule for your refrigeration services is immediately more energy efficient but is also more cost effective with reduced, planned downtime and increased reliability. Read here for more.
LEAK TEST “OFTEN”.
It is actually a legal requirement to ensure all refrigerants are kept inside the system. Once a refrigerant leak detection test has been performed and confirmed, it is your legal requirement to fix the problem. Running “top ups” attract significant fines for the plant operator and employees as well as the refrigeration service agent and its’ employees. We recommend having a regular leak detection to ensure your system is operating optimally and eliminate all leaks from your systems. Regular might mean quarterly to annually depending upon your circumstances and risks.
Going greener is not only beneficial for the environment, but can also be even further beneficial for your bottom line. The government offer various incentives to help implement energy efficient practices, systems and technologies. You can find some here.
Curious about those strange cracks in the concrete adjacent to the freezer?
It might just be a little natural ground movement or you might also have an interest in frost heave. For more information regarding frost heave and what to look out for click here.
If you would like to talk to one of our service technicians or refrigeration maintenance engineers about how to best service your facility simply click below and one of our refrigeration technicians will give you a call. Alternatively you can contact us on 03 9793 6088.