Photo Credit: www.arcticsolutions.in

The world is changing. Everyone wants to achieve more out of the limited resources and in the process to operate under such conditions, several Research and development projects take shape. Be it for electricity saving, saving mother Earth from the pollution or purifying water for drinking. In a way, all such novel ideas lead to one important aspect – savings! The growing pharmaceuticals and frozen food industries have pushed companies to take measure for their temperature-controlled transportation. The products are maintained in the prescribed range of temperature during the entire duration of transportation. The temperature-controlled transportation is so critical, especially for pharmaceuticals and vaccines, that the product which needs to be maintained between 2-8-degree C, will face severe thermal shocks if the ambient temperature leaves the specified range of transportation. Companies, globally have responded in the past few years with newer solutions which use innovative technology and advanced phase change materials (PCM) to increase performance for most applications, especially benefiting freezesensitive refrigerated biologics, food and dairy products. These improved systems offer greater performance, accuracy, reliability, and reusability by occupying minimum space, being environmentfriendly and cost-efficient.

Cold chain packaging also serves an important role in the transportation of the products. Several Innovative technologies provide several methods of packaging solution, which maintains the temperature of the product, thereby protecting it from the harsh ambient outside. Passive technology includes elsewhere frozen PCM as the primary source of cooling. Infrastructure is required to be kept online on the electric grid but away from the transportation solution. Active technology uses thermostatically controlled either battery operated or diesel operated refrigeration system to maintain the temperature of the product on the go. Hybrid technology depends upon the combination of both passive and active technologies to maintain the temperature.

Cold chain includes cold storage infrastructure, transport infrastructure and point of production infrastructure.  It refers to an environmentally controlled chain of logistics activities, which conditions and maintains the goods within a stipulated range of parameters that include temperature, humidity, atmosphere, packaging and other conditions. Figure 1 presents a sample of cold chain diagram: it indicates the importance of temperature-controlled environment at every step of the process. The temperature-controlled supply chain indicates to refer/refrigerated trucks, cold rooms, chest freezers, warehouses and last mile delivery solutions.

Figure 1: Various Processes in Transportation of Temperature Sensitive Products

Various industries that fall under this category of temperature sensitive transportation are agriculture, dairy, frozen food, horticulture, chemicals, poultry and meet. India today has only 10,000 refer and around a same number of cold rooms. The current infrastructure can hold less than 10 per cent of the country total produce. The figure below clearly demonstrates the increase of the cold chain dependents produce. From 17 million tonnes of produce in 2009, India now requires 47 million tonnes of the produce. The growth accounts for a CAGR of 13.4 per cent and at a current rate, India will require around 115 million tonnes or produce by 2025. The current trend suggests that India’s requirement doubles almost every 7-8 years.

Technology

PCM based products can be seen in every step of cold chain logistics including PCM-based solar hybrid cold room, refer trucks and deep freezers. The PCM improves the efficiency of the running application, additionally it saves on the operating and maintaining cost of the application.

Figure 2: Variables to consider in cold chain compliance

PCM based reefer trucks

Logistic solutions at present are based on refrigerated vehicles which use fossil fuels to operate. Due to this reason, the temperature-controlled logistics become more expensive than the transportation and storage of general produced goods. There is, thus, an urgent need for shift of conventional cooling systems to non-fossil fuel-based refrigeration systems as it considerably brings down the operational costs in an affordable range of the end user as well as the seller. Use of PCM as a thermal energy storage (TES) enables the transportation of goods at a constant temperature while minimising the dependency on diesel/petrol or any other conventional fuel for continuous running of cooling units in the reefer trucks at the same time. The PCM filled encapsulation units, which are mounted in the insulated containers, are charged using electrically operated compressor during the non-operational hours and then for the next 14-16 hours it is the PCM which assures that the required temperature is maintained. This system is ideal for inter-city transportation and for the services, which requires a limited radius of transportation which can be completed during the day. One more major advantage of using such a system is that now, the truck can run on compressed natural gas (CNG) cylinders which add to more savings, in terms of money as well as the environment. Pluss’ PCMs based thermoTab active plates cater to different applications needing specific temperature maintenance. PCMs ranging from (-) 30-degree C to 0-degree C are suitable to suffice cooling requirements of products like pharmaceutical, vaccines, meat, frozen food, fresh vegetables, ice creams and similar. Integrating suitable PCM to meet transportation requirements of sensitive goods has a significant impact on diesel consumption. It cuts down the diesel consumption upto 50-60 per cent along with precise temperature control by implementing TES system.

Figure 3: Growth of the Indian cold chain industry (Source: National Summit on Cold Chain: ASSOCHAM & Tech. Sci. Research)

A real-life example can be taken to explain the advantage of using this system. In a refrigerated truck with 8ft x 6ft x 6ft insulated container, if we compare the PCM plates (thermoTab active) integrated cooling system with a conventional diesel operated compressor unit, the savings on its running cost are exceptionally high. Because such a system is charged (or cooling is stored in PCM) during the non-operational hours using grid-power supply, there is complete saving when compared to charging it on diesel. The cost of operation through diesel, in comparison to electric power for cooling, is almost two times (running cost Rs. 6-7 lakhs per annum in the case of a conventional system as compared to Rs. 2.5-3 lakhs in PCM based system). This results in a very short payback period of 4-6 months, in spite of having a little higher initial investment cost requirement. It also ensures that the cooling system remains intact and long lasting due to its non-moving components involved. This technology ensures that the perishables and temperature sensitive consumable products are safe and secure even in a situation of truck breakdown or failure of cooling systems. Then there are some other advantages as well, such as low maintenance requirement and no-special skills/training requirement to operate this system. Its robust and smart controls enable maintaining temperature and air quality parameters at just the right levels inside the storage volume. The very intuitive human-machine interface provides a hassle-free and an unparalleled user experience.

Thus, this technology promotes the usage of clean and green energy by minimising the dependency on use of non-renewable fossil fuel while ensuring the safety and quality of temperature sensitive consumable products and other perishables is maintained throughout the cold chain transportation and last mile deliveries until they are finally received at consumer’s end.

Figure 4. PCM filled thermoTab active plates in a reefer truck

Benefits of PCM based Reefer Truck Units

  • It is totally environment friendly; there is no dependency on fossil fuels – diesel or petrol, to continuously run the cooling unit; uses grid power to charge once a day.
  • There are no moving parts and complicated components involved in this system, as a result of which at least 30-40 per cent lesser servicing and maintenance cost involved.
  • The PCM based reefer cooling solution offers 8-9yrs. (approx.) of service life, which a conventional system can
  • Such a solution ensures continuous safety of temperature sensitive products even in the situation of truck’s breakdown.
  • No special skills or trained worker needed to operate this system; just plug in the compressor to grid power supply, freeze the PCM, and use it.
Figure 5: Temperature-performance graphs of thermoTab active based reefer trucks.

PCM based Deep Freezers

In the last 5 years since 2013, more than 50,000 PCM-based Chest freezers and coolers have been launched in the market by major OEMs in the refrigeration space. Each PCM based freezer/cooler provides over 5000 hours of temperature control during the power outage annually. These numbers are only a miniscule in comparison to the total market size of chest freezers and coolers and hence the potential for this segment to grow is very large. Proper Initiatives in R&D, strategic scheduling and marketing can easily broaden the horizons for PCM.

Experiments conducted with load and no-load conditions suggest that there is at least an increase of 6-7 per cent in the COP (Coefficient of Performance) of any refrigeration system (figure 4) after using PCM in the deep freezer. The use of PCM pouches perfectly wrapped around the evaporator coils increases the cut-off time of compressor which directly translates into the operating cost saving. The energy stored in the PCM is utilised after the compressor cuts off, therefore maintaining a long retention time. Glycol-water mixture based deep freezers have ruled over the entire market for years, it can provide you with a cheap solution but doesn’t maintains the temperature of the inner products in a constant, and desired range for more than 4-5 hours.

Figure 6: Pouch installation in deep freezer.

For deep freezers, savE HS 23N (melting temperature of -23-degree C) is encapsulated in the multilayer nylon pouches, such designed to withstand the force equivalent to 60 kg and a temperature of around 80-degree C. The installation is nothing different from installation in a conventional deep freezer. Initially, the evaporator coils are attached to the inner shell. After the coils are in place, the pouches are wrapped around the coil-inner shell assembly. Thereafter the entire assembly is put inside the outer shell. The cavity thus formed between the coil-inner shell assembly and the outer shell is filled by injecting the high-pressure PUF insulation. The PUF being injected is maintained at very high temperature and pressure. The pouch can easily withstand the temperature and pressure, without damaging the quality of PCM encapsulated in the pouch. An important parameter to be monitored while injecting the PUF is that the PCM pouches should be properly wrapped around the coils using proper adhesive. If not, the PUF during injecting can penetrate between the coils and pouch thus affecting the heat transfer effectiveness of the entire PCM-evaporator coil system. The figure below well demonstrates the Pouch placement around the evaporator coil.

Benefits of PCM based deep freezers to conventional deep freezers:

  • Energy Saving of more than 35 per cent over operating cycle of the freezer.
  • Lower maintenance, due to non-corrosive nylon pouches.
  • Reduce the overall weight of the system, as less quantity of PCM is required when compared to water-glycol mixture.
  • Longer retention time; suitable in longer power outages of upto 16 hours.
  • Precise temperature control of (±) 2-degree C.
  • Larger shelf life, 3000 thermal stability (cycles) guaranteed, which translates to a period of 8-9 years.
  • The yearly saving per 1100-liter machine is around Rs 10,000 with a payback period of less than 1.5 years.
  • Considerable reduction in greenhouse effect.
Figure 7: Retention time of HS 23N

PCM Solar Hybrid Cold Room

Major percentage of population in the country is dependent on agriculture for their living. Though it is important to increase productivity and produce more products from the same space of land, it is also equally important to manage the products well after the process of harvest. The wastage is 0.5-4 per cent in food grains and 4 per cent-18 per cent in different horticultural crops, with the horticultural crops being high value and more perishable.

It is thus necessary to take required steps in terms of post-harvest management at the first mile operations i.e. at the farm level to check and reduce the value loss of produced farm products. With respect to this, there is a direct relation between the availability of power and the dependency of the cold room facilities. It is impossible to operate working cold room for 18-20 hours without electricity. Alternately, diesel generators are used as a power source, which incur huge costs and are unviable as well.

Figure 8: PCM based Solar Micro Cold Room

Under such circumstances, a PCM based solar micro cold room, which is a small-scale standalone PCM based solar powered cold room, can be used to store fresh fruits, vegetables, exotic and temperature sensitive flowers, processed foods and other perishable commodities. This is a pioneering product in the cold chain space that bundles various innovations together.

The solar powered cold room with thermal storage (PCM) backup enables storage of fresh produce – fruits, vegetables and flowers by constantly maintaining a temperature in the range of 2-degree C to 8-degree C or (-) 25-degree C to (-) 15-degree C throughout the day. The unit has a dimension of 20ft x 8ft x 8ft with solar panels mounted on the rooftop of the unit. These panels capture the available solar insolation during the sunlit day time (4-5 hours of effectively available sunlight), which is fed directly to the compressor system via special drive systems. The compressor then generates enough cooling to charge the PCM filled encapsulation units in the cold room which then in turn cools down the space and provides backup for upto the next day morning in the form of thermal energy storage system.

This product enables storage of perishables to preserve their freshness and maximise shelf life. It comes with every feature of an ideal cold room and is completely standalone. It can also be used in combination (or hybridised) with any other source of power as and when needed. Owing to the endless opportunities one can have using such innovative system and the impact this product can have on the lives of farm level producers or farmers, the marginally high initial investment in this technology, as compared to conventional cold room systems, should never be the prime concern.

Benefits of PCM based solar micro cold room:

  • No electricity required to run the cooling unit; thermal energy storage technique ensures 24×7 temperature maintenance.
  • Ensures constant temperature maintenance which minimises wastage of fruits and vegetables during their storage.
  • Such a cold room has minimal cost involved, be it in its operation or maintenance.
  • Is portable; can be dismantled and installed easily at remote locations where direct transportation of complete assembled unit is not possible.