Cold store powered by sustainable energy

The objective of the project is to develop and demonstrate a grid-independent cold storage system for perishable food, medicine or other goods, with a special focus on the need for such systems in developing countries with a sparse and unreliable supply of electricity. The project is directly based on the result from the international SolarChill" project where a unique battery less solar driven vaccine refrigerator was developed by Vestfrost in cooperation with Danish Technological Institute. The project partners are Danish Technological Institute (Project manager), Danfoss, Grundfos, Fresvik (Norway) and Karise Klejnsmedie. The refrigeration system is set up at the solar energy test area of DTI, where a PV array with a nominal power of 800 W has been established. The batteries and charge controller are purchased from a Danish PV system retailer. The inverter is a trapezoid 50 Hz 230 Vac inverter is a robust type with high surge current. The two AC cabinets are standard low energy household freezers, whereas the DC cabinet is a special ice-lined refrigerator (fresh food/middle temperature) with high thermal capacity in its walls. The selection of large chest type freezers gives low specific energy consumption due to a high volume/surface ratio and low air infiltration. The commercial low energy cabinets are relatively inexpensive, and can operate with an extremely low consumption if the thermostat is set to cooling mode. As part of this quite extensive project, there have been a number of contacts with associated activities as well as direct requests from companies operating in 3rd world countries. The two most important cases have been a milk-cooling project in Uganda and a World Bank GEF project regarding improved storage methods for vaccines. The current design of the PV driven refrigeration system could be modified to milk cooling, and this is actually being investigated by the Danish company "Karise Klejnsmedie" who are specialist in stainless steel processing. They are currently designing a prototype with a cooling capacity of 75 liters/day for test at DTI. The relief organization PATH is a specialist in cold chain vaccine storage and transport in developing countries. One of the major problems with vaccines is that they cannot tolerate freezing, but on the other hand they need cooling. Current use of icepacks in transport boxes requires precise adjustment of icepack temperature before outreach, but still there is a risk of freezing. A new type of icepack with a freezing temperature of 5-6°C may solve this problem, but until now they are frozen in ordinary freezers to -18°C in order to be sure they are totally frozen (avoiding sub cooling). If they could be frozen at, say, 1-2°C they could be used immediately for vaccine transport without risk of freezing the vaccine. It seems that the PLC regulated chest freezer from the current project could be well suited for this purpose, and its size is perfect for the type of rack that is used by PATH to hold the icepacks. The rack with icepacks will be tried in the lab by DTI in the near future