Introduction

The phenomenal growth in world population, concentrated especially Africa, Asia and South America, in the next 20 years to 3 billion will seriously worsen the existing population-food imbalance. Apart from steps to increase food production, concerted efforts for reducing the food loses, that take place during food production, harvest, post-harvest and marketing, is needed. This becomes more imperative as 800 million people living in these countries are under-nourished and 80% of food production of the world is done here. Traditional sun drying followed in these countries lead to reduction in the product quality due to insect infestation, enzymatic reaction, and microorganism growth and myctoxin development. Fish, cereal, grains, pulses, fruits and vegetables undergo losses up to 40%. The fossil fuel based technology used in the industrialized countries could never be an economical viable solution to these countries. Though much research and development work has been done, there is still a lack of knowledge on the processing of fruits, vegetables and fish in such a way to avoid spoilage and to obtain good quality and clean products. More over a large number of youth in the rural areas of the developing countries are looking for employment to sustain themselves. Adapting a methodology to solve the above two problems could lie in solar drying of food products.

Process Heat

Production of process heat/hot air using fossil fuel like electricity, diesel, furnace oil, LPG, coal, firewood and other forms is a common production method in almost all food processing and industrial application including ceramic, leather, pharmaceutical, chemical industries. Apart from the above industries all processing industries adopt either drying or process heat as one of its manufacturing step. It is reported that in India 1,754,400 kiloliters of furnace oil or its equivalent is being used for processing the end product. It is possible to save considerable quantity of this fuel by using 5 million m² solar air heating system. Nearly similar solar collector area is needed to meet the agro processing requirements in the country.

Planters Energy Network – PEN, a registered society initiated in 1989, is active in the promotion of solar hot air generation units for food processing and other industrial application in order to reduce/replace the conventional fuel. PEN has installed largescale solar hot air generation systems that are reliable and durable using the roofs of agro processing houses, to reduce/replace conventional fossil fuel. This article explains the experiences gained by PEN in this sector with success stories.

Tea

380 m² Solar Air Heating Systems for tea drying installed at M/s Glendale Tea Factory, Coonoor, Tamilnadu

500 m² Solar Air Heating Systems for spices drying installed at M/s Eastern Condiments (P) Ltd., Theni, Tamilnadu

4 x 167 m² Solar AIr Heating System for leather drying installed at Ranipet, Tamilnadu

Tea industry is energy intensive and to obtain final black tea of moisture content 2 to 3% from the green leaves, a large quantity of thermal and electrical energy are being used. PEN has introduced roof-integrated collector in 9 tea factories in Tamilnadu, so that their fuel consumption could be reduced up to 25 to 35% by using solar heat. These installations also reduce around 1500 tones of CO₂ emission per year.

Spices

Solar panels at Solar fruits and vegetables drying centre at Nimmo, (30 kms from Leh, Ladakh, Jammu & Kashmir)

Spices factories use fossil fuel for drying the spices to low moisture content so as to obtain nice grounded powder with good colour. PEN has installed solar drying facilities for spices for two leading spices powder manufacturing company in south namely M/s. Eastern Condiments (P) Ltd., Theni (500 + 167m²) and M/s. Sakthi Masala (P) Ltd., Erode (1040 m²). The technology is so satisfactory to M/s. Eastern Condiments (P) Ltd., it has adopted this technology in 1994 and again in 2002. A 1400m² solar collector is being planned now. There is also a tremendous potential to adopt similar solar drying units for drying of other spices like green and black pepper, small and large cardamom, cashew nuts etc.

Leather

Under the facilitation from UNIDO, a 700m² area roof integrated solar hot air system unit has been installed for a leading tannery to dry leather in Ranipet. This unit in six months time could saves 368.8 tonnes of firewood fuel and replaces a 1.2 tonne steam boiler during its operation. A similar smaller unit of a collector area 50m² in a tannery at Vaniyambadi has generated hot air of temperature above 100°C so as to save around 5 liters of diesel per hour in an auto-spray drying unit.

Pulses

The 400 kg capacity fruit/vegetable dryer at Nimmo, Ladakh, Jammu & Kashmir

PEN has demonstration the successful usage of solar heating for pulses to reduce diesel or furnace oil consumption. A 167m² area solar collector installed in a dal factory saves 60 liters of diesel per day. Quality of the dal is also improved through solar drying. Two other dal mills have opted for solar air heating technology. These projects replace the conventional diesel or agricultural waste fuel and have a pay-back period of less than 2 years.

Fish

Even though technological leaps have enhanced the fish production, due to the perishable nature of fish, an estimated 21% of the harvest is lost due to lack of post harvest processing. This results in fishermen losing considerable portion of their profit apart from the loss of considerable nutritional food to the common man. Fish is a highly perishable food product and can be stored only by refrigeration or drying. Drying is far more economical than refrigeration since the fish once dried can last longer without any processing whereas refrigerated fish requires the fish to be maintained at low temperature till consumption.

But the problem affecting the quality of the dried fish is the unhygienic way in which fish is prepared and dried. The open beach drying, results in insects laying egg inside the fish, that renders the product non-consumable. Moreover the high relative humidity of the sea breeze prolongs the drying process. The theoretical energy required for drying one tonne of fish from 75% moisture content on wet basis (w.b.) to 15% w.b. moisture content is 399.72 kWh. Since this is an energy intensive operation, prolonged drying using conventional drying requires 76 liters of diesel at a drier efficiency of 50% and it costs Rs. 2500. Considering the cost of the fish this cost is more than what a fisherman can afford. PEN introduced solar fish drying as a livelihood support to the fisherwomen. In the first project at Visakhapattinam, Andhra Pradesh PEN successful demonstrated a 500 kg of capacity hygienic processing of fish so as to obtain better market price for the fish. To cater to individual fisherwomen and small groups PEN launched an 11.5 m² area solar air heating system which will run by four DC fans, operated by 4 x 10 watts SPV panel. Nearly 40 units are installed in the coastal belt of Tamilnadu and Andrapradesh. This unit produces around 6000 kg of quality fish per annum creating around 600 job days. A 500 kg capacity unit for export purpose, has been installed at Paradip Port, Orissa.

Fruits and Vegetables

Many of the hilly regions of India suffer from lack of infrastructure facilities for processing its agro products like fruits, vegetables, etc., This leads to a huge wastage in vegetable fruits chain as well as other fruit products and it ultimately affect the farmers income. Horticulture crop is one of the important agricultural activities in most of the hilly regions of India. For example the economy of Ladakh is very much dependent on horticulture and agriculture. Ladakh (presently called as Leh District) is located between 75°50’E to 80°15’E and 32°17’N to 36°30’N and elevation between 3000 to 5000m. The region has low precipitation. Annually around 2600 ton of fresh apricot, 3500 ton of apples and other fruits and 8500 tons of vegetable are grown. Similar to other parts of the country, fruits and vegetables suffer a huge wastage (35 to 45%) due to the lack of proper processing facility. Dehydration or drying is very critical factor for these products mainly for avoiding spoilage as well as in bringing remuneration prices for the farmers. The absence of biomass fuel and availability of abundant sun's energy (ie) around 5400 Whr/m² day on horizontal plan makes it attractive to adopt solar energy for drying in these regions.

60 m2 Solar Air Heating System for fish drying at District Fisheries Youth Welfare Association, Visakhapatnam

230 m² Solar AIr Heating Systems for Ceramic drying installed at E.I.D. Parry (India) Ltd., at Alwar, Rajasthan

PEN air heaters coupled with PEN's re-circulation drier could be used to dry many fruits and vegetables. A 424 m² area solar collector was installed to produce hot air for a vegetables dehydrating company near Coimbatore. Another two units were installed for drying organically grown fruits like mango, pineapple, banana, etc for export near Batlagundu in Tamilnadu. PEN has installed many solar drying units in Ladakh and Kargil region. The roof of the processing house has 55 to 90 m² solar collector and the hot air is passed to the re-circulation drier placed inside the room. Eight such units are in operation at different parts of Ladakh. One small drier of 70 kg capacity with SPV panel has been also installed in Ladakh. The solar dried apricot fruits fetches 100% higher price in the market than the conventional open dried.

The harvesting season for many fruits are of short duration resulting in non-viability (economically) of dehydration/drying projects of the fruits. Fruit bar or fruit jelly is one of the by-product which has a shelf life of more than 9 months. Presently fruit bar is prepared in a crude and unhygienic way at the mango garden itself using rejected mangoes. The mango fruit concentrate, if properly prepared, can be stored at ambient temperature with a life span of more than 16 months. Recently PEN has installed a solar drying facility at Eluru near Vijayawada, Andhra Pradesh. A 55m² area solar collector generated sufficient hot air to dehydrate in 8 hours around 200 kg of mango concentrate. This unit has a back up heating with biomass fuel. The total project consists of the following:

A building with provision for preparing fruit concentrate during the fruit season and its storage space.

A 55m² solar collector integrated with the roof of the building.

A drier of capacity to hold 200kg of mango concentrate at a time.

A back up heating unit (either bio-mass or LPG)

Packing unit for finished product.

The total cost of the project will be around Rs.18 Lakh (without land cost). This project will handle a minimum of 60 tonnes of fruit concentrate per annum and create employment of 1500 man-days per year. This kinds of unit could be replicated through out the country mainly on the mango and other fruits growing area like Andhra Pradesh, Tamilnadu, Mandhya Pradesh, Goa, Maharastra, etc.. Once the concept established in mango, it could be applied to other fruits also.

Industrial Applications

In Apollo hospital Ranipet, electrical heating is used for drying washed wet cloth. A 55 m² solar heater provides hot air so as to reduce the electrical consumption by 60%. A similar area collector has been successfully used for drying condoms in TTK-LIG factory, Chennai reducing 40 – 50% electrical consumption. To reduce furnace oil used for ceramic drying at EID Parry factory in Alwar, Rajasthan PEN has installed a 230 m² solar air heater and the project has a payback of 3 years. Sahayamatha Salt factory near Tuticorin uses a 110 m² solar air heater for preheating air to a fluidized bed drier so as to reduce the furnace oil consumption.

Conclusions

PEN has demonstrated the concept of cost effective (pay back period is less than 3 years) solar hot air system for processing many agricultural and industrial products as a retrofit in the existing environment to safeguard optimum efficiency. Solar air heating could also be considered as energy saving measure since it reduces fossil fuel consumption. Moreover PEN has shown the working of many large level solar hot air generations using the existing roof of agro/industrial houses and to make the system reliable with longer life. The technology developed by PEN is able to provide a low cost non-fossil fuel operated methodology for processing large quantity of fruits, vegetables, spices, grains, other cash crops and other industrial and chemical products.

Application of solar air heating system in food processing and other industries