Multi-Utility Heat Pumps is based on patented technology which will help reduce cost of pre-cooling milk, fruits and vegetables while simultaneously drying fruits, herbs or spices. Heat required for low temperature drying is delivered free of cost, while simultaneously increasing the cooling capacity and coefficient of performance of the refrigeration system.

Waste heat from refrigeration units of milk chillers, cold stores and fruit pre-coolers can be recovered using novel patented Tube-Tube Heat Exchangers. These vented double wall tube and tube heat exchangers (Indian Patent # 205 362) enable recovery of the waste heat in a reliable and cost effective manner.

This recovered heat, in the form of hot water at 45 to 600 C can then be used in plastic heat exchangers to dry various products. Hot utility can be used to dry agro products to generate additional revenue.

Plastic Solar Dryers are based on patent pending technology wherein, light weight plastic collectors generate hot air to dry fruits, vegetables, herbs or spices. Hot air required for low temperature drying is circulated using PV operated fan for off-grid applications. Grapes, tomatoes, onion, guava, can be dried with the hot air, with out exposure to direct sunlight. Low temperature drying usually results in better quality products resulting in higher value realization.

Benefits
The heat pumps can be used for on-farm pre-cooling of fresh fruits like guava or grapes, while simultaneously drying guava paste or grapes. Pre-cooling is said to increase shelf life by a factor of three, thereby reducing the loss during storage, transport and retail sale. Distress sale of harvested perishable produce can be avoided with the help of pre-cooling or cold store facility. Economics of pre-cooling and cold store operation will improve significantly due to additional revenue generated from drying. Limited availability of electric power and unpredictability of power cuts can be factored in by incorporating low cost ice bank tank (IBT) or chilled/hot water storage tank/s.

Techno-Economic Viability
The technology of the heat pumps has been tested for industrial, commercial and residential applications. Suitable modifications will be undertaken to meet the needs of the rural applications. Payback period of 0.5 to 1 year is possible for such grid connected robust heat pumps for the rural market.

Plastic Solar Dryers based on novel light-weight highefficiency Plastic Solar Air Heaters costing about Rs 5000 to 6000/m2 aperture area can be coupled to efficiently heat ambient air to 50 to 900 C for use in dryers. Air in these lowpressure drop solar air heaters is circulated using PV driven fans of 5 to 10 W. These solar dryer can be used effectively used in off-grid locations. Expected payback for drying various agro produce like onions, grapes, ginger, herbs is in the range of 1 to 1.5 years.

There are several lucrative opportunities to benefit from heat pump and solar dryer technologies in our country. Based on survey at the Rahata Block in Maharashtra, INDIA, these systems could be used for milk chilling, pre-cooling guava and grapes; while drying grapes, onion, guava paste, herbs and spices.

Contact: ranemv@iitb.ac.in