ICE India Expo 2010, New Delhi, India Evaluating Existing Cold Stores In India And Applying Technical Standards For Enhancing Energy Efficiency And Performance Gurmit Singh Managing Director Walco Engineering Ltd
Present Scenario As of March 31, 2009, there were 5,381 cold stores in India with a total capacity of 24.45 million MT out of which 23.40 million MT (95.7%) fall in the private sector. Almost 75% of the total capacity is used for storing only potatoes, on a rental business model where the farmers own the produce. Mostly constructed with Large/single chamber to stock potatoes the key product, and then remain idle for about 6 months. 2
Present Scenario Erratic power supply permits only 8 to 10 hrs operation per day - usually no power back-up is available. Ignorance on maintaining appropriate commodity storage conditions - due to lack of trained manpower. Absence of Government Regulations on Technical Standards & Protocols till recently curbed quality investments in the past. 3
Consequences Existing Potato Cold Stores Weight Loss range between 5% to 8% and Rot at times exceeds 5%. Large & Unpredictable variations in Quality - industry sources reveal that only 20% of the product passes quality for processing and that too in select cold stores only. 4
Other Facts Existing Potato Cold Stores Unreliability to maintain quality during long term storage and as a result by August, every year, prices of processing potato skyrockets. Not suitable for storing multiple commodities. 5
Analyzing Existing Cold Stores 6 A Typical Conventional Potato Cold Store - Indore
Analyzing Existing Cold Stores 7 Desa, Gujarat
Analyzing Existing Cold Stores 8 A Hybrid Model ( 9 Mezzanines High)
Analyzing Existing Cold Stores 9 Storage in Bags - Typical Stacking Pattern
Analyzing Existing Cold Stores 10 Typical Mezzanine Storage
Analyzing Existing Cold Stores 11 Bunker Type Cooling Coil Arrangement
Analyzing Existing Cold Stores 12 Improvised Bunker Coils With Fins
Analyzing Existing Cold Stores 13 Domestic Ceiling Fans For Air Circulation
Analyzing Existing Cold Stores 14 Make Shift Provisions for improving Air circulations
Analyzing Existing Cold Stores 15 Countering Dehydration Problems
Analyzing Existing Cold Stores 16 Emergency Arrangement to Inducing Fresh Air..
Analyzing Existing Cold Stores 17 Instrumentation? Temperature & Humidity
Analyzing Existing Cold Stores 18 Over Heated Motors and Starters Design Issues?
Analyzing Existing Cold Stores 19 Jump Start Ignorance & Safety Issues..
Analyzing Existing Cold Stores 20 Drying, Grading & Sorting Practices
Analyzing Existing Cold Stores 21 Salvaging Sprouted Potatoes
Analyzing Existing Cold Stores 22 Rot
Need to Go Back To Basics What is a Cold Stores? The fundamental objective is to properly handle and store fresh fruits and vegetables under appropriate storage conditions for extending shelf life and preserving freshness in terms of Taste, Appearance, Nutritive Value and Hygiene. 23
Design Basics Preservation of Fresh Horticulture Produce. Cold Stores are therefore storage chambers that achieve controlled storage environment using appropriate thermal insulation, efficient refrigeration, ventilation & material handling systems. 24
Going Back To Basics Commodity Storage Standards Appropriate storage conditions may vary widely depending on type of produce, post harvest & handling methods, storage period and use, therefore the need to rely on commodity storage standards and research data for Indian Conditions. 25
Scope for Improvement First and Most Important, Do Not Apply Thumb Rules to design and operate cold stores unless you are an expert yourself. Relying on un-scientific or unauthenticated information always results in a compromise on critical design criterion, leading to inefficiency and failure in the long run. Therefore, the need to rely on Technical Standards and Protocols for the Cold Chain in India, recently notified by The Department of Agriculture & Cooperation, Ministry of Agriculture, Govt. of India. Impart adequate training to plant managers & operators to insure compliance to relevant standards and guidelines. Operating systems to near design conditions inevitably enhance energy efficiency and overall performance. 26
Notified Technical Standards Technical Standards & Protocols for the Cold Chain in India Cold storages for storage of fresh horticulture products which do not require pre-cooling (Technical Standards Number NHB-CS-Type 01-2010) Multi-commodity Cold storages for short term and long-term storage of fresh horticulture products, which require pre-cooling and varying storage requirements. Technical Standards Number NHB-CS- Type 02-2010) Control Atmosphere (CA) Storages. Technical Standards Number NHB-CS-Type 03-2010).. 27
Notified Technical Standards The Basic Data Sheet The requirements laid out in Basic Data Sheet, facilitates a detailed Technical Audit of the existing or proposed new cold store facility. It is a checklist of design essentials, critical components, operating parameters and defines the step by step process of estimating performance parameters of the proposed or existing cold store instillation. It seeks certifications from the manufacturer and contractors with respect to technical compliance thereby guaranteeing capacity and performance ratings of equipment being supplied & installed. 28
Scope for Improvement Improve Utilization for Viability Multiple Rooms Multiple Commodity Variable Temperature, Humidity Control & Air Circulation Modified Atmosphere Pre-cooling Chambers Fruit Ripening Chambers Grading, Washing, Packing, Value Additions Integration with food supply chain 29
Scope for Improvement Material Handling & Stacking Pattern Installing Conveyor Systems or Elevators to transport bags to various floor levels for storage will cut down on valuable loading time and reduce the dependency on manual labor and costs. Stacking arrangements should be planned and marked out on the floors to optimize storage capacity and at the same insure sufficient passages for air circulation, and easy movement of operation and maintenance staff. 30
Scope for Improvement Heat Load Calculation to determine total refrigeration load Transmission Load, heat transferred into the cold room through its walls, floor and ceiling. Product load, heat removed from the product brought into the cold room for storage and on account of respiration. Internal Load, Heat produced by Light, Material handling equipment, People in the cold room. Infiltration Air Load, Heat gains with warm air infiltration into the cold room through doorways and ventilation systems. Equipment load, consist essentially of fan heat where forced air circulation is used and defrost heat 31
Scope for Improvement Insulation The primary function of insulation is to restrict the transfer of heat from the warm ambient to the cool environment maintained in the cold stores. A well designed insulation envelope should at the same time also prevent vapor transmission from the warm humid ambient to the cold store environment. This is achieved by providing suitable vapor barriers and selecting insulation materials with low moisture permeability. If moisture passes into the insulation and makes it wet, the insulating properties are decreased and eventually the insulation envelope fails. It is a extremely important to apply the recommended thickness of insulation using the correct methodology for maximizing efficiency. 32.
Scope for Improvement Cold Store Doors Choosing and installing the right type of cold room doors is vital to improving efficiency and performance in cold stores. All cold storage doors are required to be durable to frequent operations, suitably insulated and hermetically seal when closed. Their smooth and quick action ensure less cold air loss, less condensation, less frost build up, less energy consumption and enables stored commodities to be maintained at peak perfection. 33
Scope for Improvement Refrigeration System Condensing Unit Compressors Condenser Cooling Coils Refrigerant 34
Scope for Improvement System Performance Vis-à-vis Operating Parameters - Typical NH3 Compressor Compressor SST SP 35 C/ 95 F ( 181.4 psig) 40.5 C/ 105 F ( 214.6 psig) ( 240 psig) at 930 rpm Deg C Deg F psig Tr. BHP Tr. BHP Tr. BHP 1-10 14 27.6 42.4 55.5 40 60.3 38.4 63.6 2-5 23 36.9 54.1 59.1 51.6 65.5 49.8 69.7 3-2 28.4 43.2 61.8 60.7 59.5 68.2 57.7 72.9 4 2 35.6 52.5 72.7 60.7 69 68.4 66.7 73.5 5 5 41 60.3 82.4 61.1 78 69.8 75.8 75.4 35 SST Saturated Suction Temperature ; SP Corresponding Suction Pressure Tr Ton of Refrigeration ; BHP Motor Break Horse Power
Scope for Improvement Compressors With Automatic Capacity Control All compressors should be provided with capacity control arrangement which is activated by a pressure transducer so that the compressors load and unload automatically to match the cold store refrigeration requirement which varies during the day/season. To further optimize the operation, automation to the extent of sequencing the compressors for lead-lag operation maybe considered. 36
Scope for Improvement Condensers The refrigeration condenser is a vital component which rejects the heat into the ambient enabling the cooling process through the refrigeration cycle. They should be cleaned and maintained regularly. Condensers should be carefully evaluated for the peak load requirements based on the correct ambient conditions and desirable operating parameters Otherwise, it can de-rate the cooling capacity of the total refrigeration system by almost 8% with a 21% increase in electricity consumption. 37
Scope for Improvement Cooling Coil Selection & Operation Considerations are: Optimizing Delta T Across The Coil The difference between return air temperature and the saturated suction temperature of refrigerant is a critical factor determining the size and heat transfer capacity of the cooling coil. For Low humidity Delta T can be selected between 11 C to 17 C. For High Humidity Delta T can be selected between 2.2 C to 4.4 C. (Ref Stoecker, W.F. 1998) 38
Scope for Improvement The Importance of High Relative Humidity Relative humidity is the amount of moisture in the air compared to what the air can "hold" at that temperature. When the air gets saturated and can't "hold" all the moisture, then it condenses as dew. Fresh produce in the cold store is continuously respiring, thereby discharging carbon dioxide and water vapor into the cold store environment. Water is also lost from the tissues by transpiration at a much higher rate if humidity and temperature conditions are not as per recommendations. When fresh produce is loaded in a cold store chamber, the respiration rate is at the peak. During the cooling and pull down cycle the RH instrument may usually show high humidity, above 90%, - but there is a need to monitor the water condensate flowing out through the cooling coil drain-pan to estimate the exact water loss and exercise control. 39
Scope for Improvement Maintaining Humidity Once the field heat is removed and the product temperature reaches the desired holding stage condition, extra humidification can be discontinued provided, the cold store is fitted with a well designed cooling system. Cold Sores designed with undersized cooling coils however require continuous humidification throughout the storage period. But additional humidification systems may causes wetting of produce resulting in fungus & rot and may adversely affect long term storability. 40
Scope for Improvement Air Circulation Air circulation should be designed to maintain uniform temperature at all places inside the cold stores through out the period of storage. During the pull down period, there is a need for higher air circulation to remove the field heat - the fan capacity on the cooling coils may not be adequate and additional air circulation fans may be required at suitable locations. However, once the holding conditions are maintained the air circulation rate can be reduced to the extent of maintaining consistent temperature within 1 C. 41
Scope for Improvement Maintaining Consistent Temperature & Humidity Conditions The present necessity of reshuffling - palti - of bags within the cold rooms during the pull down period is mainly on account of poor air circulation. Hence proper design will save high labor costs and damage to produce. It should be kept in mind that the recommended humidity levels are maintained at all times or else the required air- circulation will lead to dehydration of produce. 42
Scope for Improvement Variable Frequency Drives Basic Fan Laws for Axial Fan Blades Flow Speed Pressure (Speed)2 Energy (Speed)3 This means 80% fan speed (20% reduction in speed) amounts to 51% Electrical Consumption by the evaporator fan Therefore, use of speed control devices like Variable Frequency Drive (VFD) on the cooling fans will improve energy efficiency and performance 43
Scope for Improvement Requirement of Fresh Air & Energy Recovery For maintaining quality and extending shelf life, sufficient amount of fresh air is required to flush out carbon dioxide to a level below 4000ppm ( in case of potatoes ) throughout the storage period. The present practice of opening doors and hatch windows lead to energy loss, as the cold air is just allowed to flow out into the ambient, during summers exceeding 43 deg C. At times, the energy loss during this period can be up to 10% of the total refrigeration capacity. It is therefore desirable to use controlled ventilation system with suitable energy recovery device which can recover up to 70% cooling energy from the exhaust cold air. 44
Scope for Improvement Ante Rooms & Air Curtains Ambient conditions of high humidity and temperature generally always lead to condensation on the surface of the cold produce when it is directly unloaded into the open thereby wetting its surface and affecting its quality and shelf life. Therefore ante rooms become a necessity where the produce is first unloaded and held for a period of time till the product is warmed above the dew point temperature. To further minimize energy loss due to infiltration through doors, special devices like air curtains and strip curtains should be utilized. 45
Scope for Improvement Other Energy Saving Measures Refrigerant Piping Design. Air Purger. Power Factor Controller. Renewable/Solar Energy. Light Fixtures CFL/LED. Refrigeration Controls & Automation. Natural Lighting for General Areas. 46
Scope for Improvement Safety Provisions Fire Fighting Equipment Handling Refrigerant Leaks Safety devices, Controls & Alarm Systems Emergency Lighting in the Cold Chambers Lightening Arrestors First Aid Kit 47
Scope for Improvement Operation & Maintenance As Built Design & Installation Manual O&M Manual Equipment Performance Rating and Certification Data Acquisition Log Recommended Spare Parts. Sanitation & Hygiene Practices Staff and Operator Training O & M Contracts 48
A Case Study Basic Design Data Product Seed Potato Storage Temperature 3 C (+/-1 C) Plant location: Uttar Pradesh or Punjab Outside dry-bulb temp: +45 C (max.) Outside wet-bulb temp: +30 C (max.) Product Receiving system : Open trucks Product Temperature at the time of loading 20 C to 25 C Storage system : 50kg Bags stacked on Mezzanine floors 49
A Case Study Basic Design Data Total Storage Capacity: 5000 Mt No of Chambers & Capacity: 4 X 1250 Mt. Chamber Size: 21.00 m x 16.00 m x 13.70 m (L x W x H) Duel Commodity Cold Store with mezzanine floors Loading Rate: 4% to 5% of the total storage capacity / day (equally split into four chambers) Pull-down time : 24 hours Compressors running hours : During Pull Down - 20 hours/day and During Holding 18 hours/day 50
A Case Study Compliance to Technical Standards Technical Standards and Protocols for the Cold Chain in India (Technical Standards Number NHB CS Type 01 2010) National Horticulture Board Department of Agriculture & Cooperation Ministry of Agriculture, Govt. of India. 51
A Case Study Refrigeration Load Summary During loading and Pull Down to 15 C (Per Chamber) - loading @ 1000 Bags/day/Chamber * S. No. Description KW / 24 Hrs. Percentage 1. Transmission Load 12.12 14.20% 2. Product Load 43.16 50.58 % 3. Internal Load 5.25 6.16% 4. Infiltration & Ventilation Air Load 16.14 18.93 % 70% Recovery 5. Equipment Load 8.65 10.13 % Total 85.32 (24.37 TR) 100 % * Variable on Loading Rate & Product Temperature 52
A Case Study Refrigeration Load Summary During Pull Down to 3 C @ 0.5 C per day (Per Chamber) - Fully Loaded * S. No. Description KW / 24 Hrs. Percentage 1. Transmission Load 12.12 14.35% 2. Product Load 54.56 64.60 % 3. Internal Load 0 0% 4. Infiltration & Ventilation Air Load 9.11 10.79 % 70% Recovery 5. Equipment Load 8.66 10.26 % Total 84.45 (24.13 TR) 100 % * Fixed Load 53
A Case Study Refrigeration Load Summary During Holding Period at 3 C (Per Chamber) * S. No. Description KW / 24 Hrs. Percentage 1. Transmission Load 12.12 36.30% 2. Product Load 14.80 44.94 % 3. Internal Load 0 0% 4. Infiltration & Ventilation Air Load 3.03 9.20 % 70% Recovery 5. Equipment Load with VFD 2.97 9.06 % Total 32.93(9.41TR) 100 % * Fixed Load 54
A Case Study Total Refrigeration Load Summary with 10% Safety Factor Total Refrigeration Load Peak Period Holding Period Lean Period With 2 Chambers KW/24 Hrs 371.58 144.90 72.45 (106.17 Tr) (41.40 Tr) (20.70 Tr) 55
A Case Study Typical Configuration of Cooling System & Equipment Selection Refrigerant System Compressor Capacity Control Condenser Cooling Coil Defrosting Humidification - Ammonia - Overfeed - Multi Cylinder Reciprocating - Automatic in Step - Atmospheric - High Efficiency finned coil with carbon steel tubes and fins, hot dipped galvanized, 6 rows deep & 8 mm fin pitch - Air / Water - Micro Mist 20 lit/hr/chamber with controller 56
A Case Study Compressor Operating Parameters Compressor Make & Model Nos. Comp. RPM Operating Parameters Evap. SST. / Cond. Temp ( O C) Refrigeratio n Capacity (KW) Motor Rating. (KW) Total Electric Power. (BKW) Remarks Working /Standby Investor s Selection 1 880 +2 O C / 38 O C 52 psig/197.5 psig 234.85 KW 55KW 45.5 BKW Pull-down Investor s Selection 1 880-2 O C / 38 O C 43psig/197.5 psig 200.90 KW 55KW 45.3 BKW Holding 57
A Case Study Atmospheric Condenser Operating Parameter Condenser Make & Model Nos. of Stands Operating Parameters & flow (lps) (max) Condenser Capacity (kw) Pump Motor Rating (kw) Total Electric Power (BkW) Remarks Working /Standby Atmospheric 2 Dia. Pipe 24 38 O C/197.5 psig/38.4 lps 560 KW ( 2 Comp) 3.7 KW x 2 6.29 BKW 50% During Holding 58
A Case Study Air Cooling Unit Operating parameters ACU Make & Model Nos. Operating Parameters Evap. (SST) & TD* ( O C) Cooling Capacity (KW) per coil Air Flow (CMH)/Coil Material of Coil Tubes & Fins Fin pitch (mm) Total Fan Electric Power (BKW) Investor s Selection 12-2 O C SST & + 3 O C Return During holding 28 KW 35700 CMH Hot Dip Galvanized 8mm 1.78 Investor s Selection 12 + 2 O C SST & + 9 O C Return During Pull Down 38 KW 35700 CMH Hot Dip Galvanized 8mm 1.78 59
A Case Study Summary of Estimated Electrical Operating Load Equipment Peak Period BKW Holding Period BKW Lean Period BKW Compressors 91 45.3 27.18 Condenser Pumps 6.29 3.145 3.145 Air Cooling Units 21.36 7.32 3.66 Over Feed System 4.7 4.7 4.7 Internal Lighting/Misc. 2 0 0 Total Operating Load (BKW) 125.35 60.47 38.68 60
A Case Study Estimated Performance Parameters of the Proposed Cold Store Parameters Peak Period* Two Compressors Operating & Two Condenser Pumps Holding Period* One Compressor Operating, One Condenser Pump &VFD Control Lean Period* One Compressor Operating at 50% One Condenser Pump &VFD Control Coefficient Of Performance (COP=KW Cooling/BKW Power) of the Proposed MT Cold Store Unit 469.70 /125.35 =3.747 200.90/60.47 =3.322 100.45/38.68 =2.596 Power Consumption (KWH/Day) considering diversity factor of 0.8 125.35 x 0.8x 20 hrs =2005.6 60.47 x 0.8x18 hrs =870.78 38.68x 0.8x 18 hrs =557.11 61 (*) Peak Period: 15th Feb. to 15th March and Subsequent Holding Period: till end October
A Case Study Estimated Performance Parameters of the Proposed 5000MT Cold Store Parameters Peak Period* Two Compressors Operating & Two Condenser Pumps Holding Period* One Compressor Operating, One Condenser Pump &VFD Control Lean Period* One Compressor Operating at 50% One Condenser Pump &VFD Control Total Electricity Cost (Rs/Day) at Rs 4.50/ Unit Rs 9025.20 Rs 3918.55 Rs. 2506.99 Electricity Cost (Rs/Month/50kg Bag) Rs 2.70 For 100,000 Bags Rs 1.17 for100,000 Bags Rs 1.50 for 50,000 62 (*) Peak Period: 15th Feb. to 15th March and Subsequent Holding Period: till end October
Conclusion For majority of the existing potato cold stores, average electricity consumption cost range between Rs.14 to Rs.16 per 50 Kg bag during the storage season of eight months coupled with product loss and devaluation of over 20% as per conventional standards. Through proper design electricity cost per bag can be brought down to Rs.11.55 or lower, thereby improving energy efficiency by at least 17% to 28% and at the same time maximizing storability and overall quality of the fresh produce. 63
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