Energy saving cold storage
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This is a presentation showing how much energy can be saved by using equipment engineered by CT-technologies in Denmark. CT-technologies are helping clients with solutions within cold facilities (e.g. cold storage, meat processing plants, dairy plants, etc.). If you need more information please write an e-mail to bba@ct-technologies.dk
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Energy saving cold storage
- 1. - Delivering world-class solutions for insulation of Cold Stores and Food Processing Plants Energy saving cold facilities
- 2. 07/10/2015 Operation costs in a cold facility • Typically energy consumption account for a substantial part of running a cold facility • This substantiates the need for lowering energy consumption 26% 10% 41% 9% 14% Energy Other Salary Administration Rent
- 3. 07/10/2015 Several areas can be considered when lowering energy consumption in a cold facility. • Insulation panels • Strip curtains • Air curtains • Doors • Loading docks • Light fixtures • Refrigeration system • Day-to-day basis CT-technologies can provide the above products/services Purpose
- 4. 07/10/2015 Insulation panels Bad building insulation (walls, floor, ceiling) negatively affects room temperature. This results in: 1. High energy consumption 2. Reduction of frozen food shelf life 3. Lower food quality 4. Frost build-up Frozen food shelf-life
- 6. 07/10/2015 Insulation panels: Case study Details: • Energy saving when replacing 100 mm PU panels with 200 mm PU panels from CT-Technologies • Room size: 2000 m3 • Cold store room: -25°C • Outside cold store room temperature: +35°C • ∆t: 60
- 7. 07/10/2015 Insulation panels: Case study cont. Result and notes: • Replacing 100 mm panels with e.g. 200 mm panels will save energy costs by USD7756 per year in a 2000 m3 cold room • Heat loss through a cold facility’s roof is higher than anywhere else. Therefore, 200mm + 100mm panels can be installed for even higher energy savings * (assuming $0.17 per kWh) 100 mm PU panel 200 mm PU panel Heat transfer coefficient 0.23 (W/m2/K) 0.12 (W/m2/K) Heat loss through walls (24hours and room at -25°C) 262 kWh 137 kWh Energy saving when using 200mm instead of 100mm (24H) 125 kWh Energy saving per year ($) * $ 7756 Panel price per m2 (incl. shipping) 36 USD 57 USD Total price for 2000m3 cold room $28512 $45144 Payback period when choosing 200mm panels 5.8 years
- 8. 07/10/2015 Strip curtains Excessive door openings can result in excess use of energy and may affect temperature control within a cold store Source: ICE-E (2014)
- 9. 07/10/2015 Details: • Cold room storing uncooked pies • Desired pie temperature: 3-5°C • 2 doors without strip curtains Problem: • Pie temperature reaches 12°C during operation hours ** • Heat infiltration through doors responsible for 68% of heat load on the store *** Strip curtains: Case study Case study: UK pie factory, lack of strip curtains* Solution: • Install strip curtains on doors. CT-technologies use high quality strip-curtains for minimum heat loss • Installing strip curtains saved 19% of the energy used by the cold store (from 5.3kW / day to 4.3kW / day) **** • Pie temperatures were kept at desired level of 5°C
- 10. 07/10/2015 Strip curtains: Case study cont. Temperature of pies in cold store with strip curtains. Temperature of pies in cold store with no door protection.
- 11. Air curtains 07/10/2015 Using CT-technologies’ air curtains is an effective way to combat warm air infiltration and thus save energy Air curtain benefits: 1. Reducing heat loss by up to 80% 2. Energy saving: 1-10 % 3. Energy savings generally pay for the equipment and installation costs within 1-3 years 4. Maintains visibility and safety 5. Improves sanitation Source: Berner (2013)
- 13. 07/10/2015 Doors Problem: Slow speed/manual conveyor and forklift doors allow large amounts of infiltration due to the length of time the doorway is open during the operation cycle = higher energy bills. Solution: Replacing an old, slow moving door system with a modern, high-speed door system (with the latest technology) from CT-technologies results in significant energy savings. Source: Cold Chain, 2014
- 14. Doors: Case study 07/10/2015 General refrigeration data Measurement Infiltration air temp. (average) 27°C Infiltration space humidity 70% Refrigerated space temp. -28°C Refrigerateted space humidity 5% Day per week 7 Door opening per hour 12.5 times Operating hours 8.76 hours Refrigeration type 1 kw/ton Door specification 12 inch / Sec. door 60 inch / Sec. Door Measure ment Door height 305 305 cm Door width 244 244 cm Door area 2438 2438 cm2 Hold time 6 6 seconds Opening speed 30.5 152 cm/sec Closing speed 30.6 153 cm/sec Total door open time 22 9 seconds Average refrigeration load 160,52 67,00 kWh Energy use, general refrigeration 399,120 166,905 kWh / year • Energy saved per year: 233,132 kWh • $39,632 per year (assuming $0.17 per kWh)* Comparison: 12 inch/second door with 60 inch/second door*
- 15. Loading docks and operation 07/10/2015 Problem: The time taken to load and unload products a cold store affects: • The amount of hot and humid air infiltrated through the doors • Heat gained by the products in the meantime (which may lead to their deterioration) • Increased number of necessary defrost cycles (due to extended door openings) = All equal to higher energy bills Solution: CT-technologies’ design ensures minimum electricity consumption by: • Reducing heat infiltration into cold store by installing air curtains on the doors • Designing ante-room (cooling down air in the ante-room outside the frozen rooms to e.g. 5°C) • Adding mechanical cooling in the loading dock. Source: ICE-E (2014b)
- 16. Loading docks and operation: Case study 07/10/2015 • A case study from an ice-cream factory in Bulgaria showed 8% energy saving by implementing CT-technologies’ design standards explained earlier. Comparison of expected energy savings and required investments for different solutions to reduce heat loads from infiltration through the cold store docking area and doors. kWh saving / month = 150.000
- 17. Light fixtures 07/10/2015 Problem: • Traditional lights installed in a cold facility have high heat energy • Because of the heat from the lights, the chillers need to remove the energy created by heat from the lights to keep a low temperature in cold storage Solution: • Replacing traditional lights with CT-technologies’ HIF/LED lights/Led lights with intelligent control will save a substantial amount of energy usage.
- 18. Light fixtures: Case study 07/10/2015 • In a – 26C° Cold Storage 50 x 250W sodium lamps were replaced on a one-for-one basis with 50 x 48W LED light fittings • 80% reduction in energy consumption • Assuming a 24/7 365- day operation, the annual energy saving would be 175,000 kWH • Or $29,750 in energy saving/annum (assuming $0.17/kWh) • Carbon emissions will also be reduced by 94,000 tons per annum • Additionally, the LED lights will contribute to more room brightness (see image) Before LED light After LED light Souce: Savenergi, 2014
- 19. Refrigeration system 07/10/2015 The energy cost above call for high quality refrigeration systems to reduce energy costs. Sector Proportions of energy costs that can be accounted for by refrigeration Meat, poultry and fish processing 50% Ice cream manufacturing 70% Cold storage 90% Food supermarkets 50%
- 20. Refrigeration system cont. 07/10/2015 Choosing refrigeration equipments such as: • Compressors • Condensers • Air coolers • Chiller units • Ice handling equipment • Freezing equipment saves a substantial amount of energy. CT-technologies has years experience in supplying and selecting the best industrial refrigeration equipment from the industry’s leading manufactures.
- 21. Refrigeration system cont. 07/10/2015 Reducing condenser temperature is key to saved energy bills. Energy savings in % by reducing condenser temperature 1°C
- 22. Refrigeration system cont. 07/10/2015 Appropriate condenser size: • Increasing condenser size to match cold room facility results in up to 10 % energy saving * Evaporators: another key area to reduce energy consumption: • Evaporaters with intelligent defrost control saves energy consumption by 9%. • Evaporators with low fan horsepower can save up to 25% on energy bills ** The importance of piping insulation not to be neglected:*** • CT-technologies can advise on piping insulation (e.g. how thick insulation needs to be) • Well insulated piping system can reduce costs by 5%. **** Source: Carbon Trust (2015)
- 23. Refrigeration system cont. 07/10/2015 High quality refrigeration equipment and well-operated refrigeration plant can reduce energy consumption by 50% or more. For instance: 1. Use a central system with a few large industrial type compressors. 2. Use of state of the art fans, motors, lamps etc. with ultimate efficiency. 3. Evaporative condensers rather than air cooled types. 4. Oversized evaporator and condenser surfaces enables compressors to work with high evaporating and low condensing pressures with consequent low wear and low energy consumption. Source: Carbon Trust (2015)
- 24. Energy saving on a day-to-day basis 07/10/2015 CT-technologies can advise on how to save energy on a day-to-day basis. For instance*: 1. Optimise air flow for refrigeration equipment: Energy saving: 5% 2. Correctly stock display cabinets: Energy saving: 3% 3. Fan controls on large refrigeration units: Energy saving: 1% 4. Switch lights off when not needed: Energy saving: 2% 5. Anti-condensation spray: Energy saving: 1-2% 6. Optimise compressor set points: Energy saving: 15% 7. Ensure efficient operation of condensers and evaporators: Energy saving: 5-7% 8. Optimise evaporator set points: Energy saving 2% per ºC Source: Nitra (2015)
- 25. References 07/10/2015 - Berner (2013) “Air Curtains: a Proven Alternative to Vestibule Design” - Carbon Trust (2015) ”Refrigeration systems - Guide to key energy saving opportunities”. - Cold Chain (2014) ”Minimizing Infiltration Into Refrigerated Spaces”. Available at: http://www.coldchainllc.com/wp-content/uploads/2013/02/Minimizing-Infiltration-into- refrigerated-spaces.pdf - ICE-E (2014) ”ICE-E case study 4 Door protection”. - ICE-E (2014b) “Loading and operation of cold rooms” - Nitra (2015) “Chilling energy costs”. - Savenergi (2014) ”-26°C Cold Store Trial – LED Hi-Bay Lights”. - The ohio state university (2014) ”Using off-peak power rates to reduce refrigeration costs”.
- 26. For more information contact CT- technologies via www.ct-technologies.dk 07/10/2015
Editor's Notes
- The above calculations are based on a real-life example from East-Timor. A 1500 m2 Distribution Center to store chilled and frozen food products. Note: energy price in East Timor: $0.24/kWh
- Emidan report shows that bad building insulation is a major contributer to high energy consumption and thus high energy bills. Also, bad insulation results in affecting the required temperatures in the room. 1. Increased refregiration load: Infiltration heat creates additional refrigeration load, which reduces the refrigeration system’s ability to maintain temperature and increases the electricity expense required to run the refrigeration equipment. The increased use of electricity can be accurately calculated (Cold Chain, 2014) 2. Frozen food quality is senstive to elevated and fluctuating storage temperature (a steady low temperature is required) (The Ohio State University, 2014) 3. To combat frost buildup, more frequent energy intensive defrost cycles are required, resulting in significant additional expense (Cold Chain, 2014)
- The above are examples of bad insulation. The standard of a cold room’s insulation can be measured by scanning sections of walls, ceilings and doors with infra-red cameras. Replacing such panels with high quality panels will result in substantial energy saving
- ∆t: 60 (-25C -35C)
- Note: English comma system is used (opposite of Danish) Note: assumed kWh is an avarage of energi prices from Nigeria, Ghana, Philippines, Vietnam, Indonesia and East Timor. Heat transfer coefficient: The lower the less energy is needed Calculations: 2000m3 = 792m2 ∆t: 60 kWh needed to keep at -25°C (24hours), 100 mm panel: 792 x 0.23 x 60 = 10930 10930 x 24h = 262310 262310 / 1000 = 262kWh kWh needed to keep at -25°C (24hours), 200 mm panel: 792 x 0.12 x 60 = 5702 5702 x 24h = 136858 136858 / 1000 = 137kWh Energy saving per year: 262-137 = 125 kWh saving per day. 125 kWh x 365 days = 45625 kWh saving per year. 45725 x $0.17 = $7756 Total panel price for 2000m3 room: 100mm: $36 x 792m2 = $28512 200mm: $57 x 792m2 = $45144 Payback period, when choosing 200mm panels instead of 100 mm panels. 45144 / 7756 = 5.8
- * During door openings warm air enters the cold store through the top of the entrance and cold air leaves through the bottom. The difference in enthalpy between the warm and cold air means that heat has entered the cold store. The warm air entering the store may contain more moisture than the cold air leaving. This moisture can be deposited throughout the cold store, but is generally worse above the door, on the refrigeration coils and on the floor near the door. If the cold store operates below 0°C this moisture will turn to ice. Heat needs to be removed by the refrigeration system to condense and freeze this moisture. This increases the energy consumption and running costs of the refrigeration plant.
- * A typical example of this was seen in an audit carried out at a pie factory in the UK. The room examined was used to store uncooked pies at 3-5°C. As pies were stored in the room for between 2 and 18 hours prior to cooking there were significant numbers of door openings as product was moved in and out of the store. The cold store had 2 doors, both had no door protection ** During the week when the factory was operated the temperature of pies within the store rose daily, sometimes to temperatures in excess of 12°C (see graph below). At weekends when the store doors were closed the temperature of the pies was maintained below 3°C.This indicated that the cold store doors were responsible for a large infiltration load on the store and that methods to reduce infiltration would be beneficial. *** Heat loads calculated for the cold store showed that infiltration was the greatest heat load and was responsible for 68% of the heat load on the store. Potentially this could be reduced by half if strip curtains were fitted to the open door. **** In the audit with no door protection the store refrigeration system used on average 5.3 kW and the doors were open for 1.9 hours in each 24 hour period of the audit. With the strip curtains fitted the average energy used was 4.3 kW (reduction of 19%) when the doors were opened for a similar time each day. In addition the temperatures of pies were significantly reduced, often by up to 5°C during peak usage times (see below). The energy savings did not take into account the effect of reducing the cold store temperature and so if a like for like comparison at similar store temperatures had been able to be carried out the impact of adding strip curtains would have been even more significant.
- Note: Strip curtains need frequent adjustments and maintenance and replacement in order to keep their efficiency
- 2. Depending on climate, building size and traffic volume) 4. Prevents ice from forming on glass door panels and can dry excess water on floors. 5. Air Curtains reduce the entry of insects (non-recirculating unit), dust and airborne contaminates.
- * 12inch/second or 60inch/second refers to the the amount of inches the door closes per second. 12 inch = 30cm , 60 inch = 152cm The table demonstrates potential energy savings obtained by replacing a single, slow door system with a new high speed door system with all other factors being the same. In the example above, replacing a slow moving door on a -28C freezer with a high speed door system would save approximately 230,000 kilowatt hours annually. At $0.17 per kWh, the resulting financial benefit would be approximately $39632 per year.
- Note: the above is a very large cold storage
- *Assuming 8 hours operation per day (368kWh per day)
- LED technology has major advantages over the conventional discharge lighting which is used extensively within the cold store environments. Unlike sodium or metal halide lamps, LED lights have an instantaneous start-up time of less than 2 nanoseconds, making them ideal for being switched off during periods of inactivity within an area, and then instantly switched on again when needed. Also, unlike fluorescent lamps, LED fittings operate better at lower temperatures. Another example: Example: 100 lights in a cold store use approximately 134,320 kWh per year Total cost per year when $0.17/kWh: $22,834
- http://www.carbontrust.com/media/13055/ctg046_refrigeration_systems.pdf
- High quality refrigeration equipment used by CT-technologies have the ability to reduce condensor temperature by a higher proportion than avarage industry equipment.
- * It is often seen that condensers does not match cold storage facility requirements (small in size compared to the need). ** increasing the fan horsepower of an evaporator from 1 horsepower to 3 horsepower increased the capacity of that evaporator by about 22 percent but consumed about three times as much power. Generally, an evaporator, properly selected, should not consume more than 0.4 horsepower per ton. CTT uses evaporators with low fan horsepower. Variable Frequency Drives (VFDs), which are electronic devices used to change the speed of motors by changing the cycles of the electrical supply, are very profitable even in systems in which the systems are cycled off. One VFD for each evaporator or defrost station is all that is required. Kollasch suggested that VFDs are very useful for capacity control because a 10 percent reduction in condenser fan speed results in an 8 percent capacity reduction, but that same 10 percent speed reduction also results in a 25 percent reduction in electric power consumption. ***All refrigerated pipework should be insulated to prevent unwanted heat gain. The colder the pipe, the more insulation is required. Insulation needs to be sufficient to stop condensation forming on the surface. This is a heat gain in itself. The condensation can also make the insulation wet. Pipework in sub-zero temperatures requires special care, to stop moisture freezing inside the insulation. Low-temperature insulation has to be air-tight as well as thermally sound, or the insulation will break down. **** Up to 5% for suction line insulation.
- ***** CTT can both deliver high quality equipment and advise about running a well-operated and maintained refrigeration plant. rather than many small split units with commercial type compressors. Large units are more efficient than small units 3) lowers the condensing pressure further, resulting in even better Coefficient of Performance (COP) 4) results in improved efficiency.
- *The following opportunities can be undertaken immediately and have no or minimal financial costs. Can provide between 1% and 5% saving (or even higher) in energy consumption. 1. Undertake a visual survey of the refrigeration units and components. If refrigeration equipment is unable to operate efficiently it will consume higher than normal quantities of energy. Remove debris where possible; maximize air flow. 2. Pay attention to the maximum fill lines; blocking air flow can add 3% to a store’s refrigeration costs. 3. For large refrigerated units, turn the fans off when the door is open for an extended period. 5. Anti-condensation spray applied to the freezer doors removes the need for electrical anti-condensation methods. 6. A compressor removes heat through the evaporator and is the most energy consuming element within a refrigeration unit. To ensure optimum efficiency, set the compressor to the lowest condensing temperature possible and keep suction pressure only as low as is required. 7. To optimise the efficiency of a refrigeration unit, all of its elements must be able to function properly. If a condenser, which rejects heat to the atmosphere, is not able to function properly, the compressor will need to compensate at a rate of 2-4% for each 1ºC. Undertaking maintenance, cleaning and leak repair is a sure way to minimise the energy spend for refrigeration. 8. Evaporators are the components which create the cooling effect. Keeping set points as high as possible will ensure the evaporator only defrosts when needed; maintaining the temperature at optimal levels and keeping costs low.