Research Projects

Farmers, business owners, and consumers require cooling to deliver their products to the market, store them for later consumption, and cool their homes and buildings. Vaccines are an excellent example of a product that requires refrigeration, yet the lack of reliable, inexpensive electricity in parts of India makes this difficult to achieve. Our proposed technology eliminates the need for electricity, and associated greenhouse gas emissions and instead provides cooling inexpensively using widely available solar thermal energy. Adsorption refrigeration systems consist of a solid adsorbent and a fluid like water. The action of the adsorbent replaces the compressor in conventional refrigerators. Water molecules adhere to a dry adsorbent (like a desiccant), and can be driven off through the addition of heat (in this case with solar energy). The high-pressure water vapor is condensed and passed through an expansion valve to generate cooling in an evaporator, before completing the cycle by adhering once again to the adsorbent. The proposed adsorption freezer box enables ice (or cooling at other temperatures) to be generated on a daily basis by exposing the box to sunlight. The freezer box is a simple design that consists of an adsorbent bed, an evaporator, and a condenser. The desiccant bed is sealed in the box's lid and the evaporator and condenser are fitted to the side of the box. The top of the lid is transparent to sunlight for receiving solar energy during the desorption process. The box is thermally insulated and initially evacuated to remove trapped air in the desiccant pores. The novelty and innovation of the proposed design is the development of a practical geometry, a box, suitable for widespread application for either refrigeration or air conditioning. To our knowledge, a solar-thermal-driven adsorption-cooling unit has not been developed in this form factor. Depending on the desired cold temperature, the adsorbent bed and refrigerant can be easily replaced. For example, the Ministry of Health and Family Welfare Government of India (MoHFW) reports that the majority of medicines require storage temperatures between 2 to 8oC. This temperature range can be achieved by using silica gel as the adsorbent and water as the refrigerant. Similarly, to achieve the freezing temperatures necessary to make ice activated carbon (adsorbent) and methanol (refrigerant) can be applied. We estimate that a box of length 58 cm, width 50 cm, and height 60 cm can easily accommodate 5 kg of adsorbent, and produce at least 2 kg of ice each day. Anticipated design improvements, including the capability to connect the box to an external heat source in addition to solar thermal energy, should lead to even greater amounts of cooling to enable air conditioning of small buildings and/or refrigeration of fresh fruits and vegetables, vaccines, or other products.