Role of renewable energy technologies for sustainable agriculture

Mahendra S Seveda / PP Dabral *

Sustainable agriculture is farming in sustainable way i.e. without damaging the environment and future resource generations. Energy is the most important resource for progress and growth of any agriculture. Energy is central to National development process and to provide major vital services that improve human condition-fuel for cooking, light for living, motion power for transport and electricity for modern communication.

In agricultural sector, its use is in every form of inputs-seed, fertilizer, agro-chemical for plant protection, machinery use for various operations for crop production and processing, household activities and transport. The shortage of energy is an issue in many countries, particularly those in the developing world. Even where conventional energy is plentiful, there is pressure to reduce the amount of fossil fuels used.

Concern over global warming is universal and this has focused our attention on utilization conventional sources of energy to be replaced by renewable sources of energy. The renewable sources of energy include, wind energy, hydro energy, ocean energy, geothermal energy, hydrogen energy. Renewable energy technologies produce sustainable and clean energy from different renewable energy sources.

Solar Energy Technologies

Solar energy is the most readily available and free energy source since prehistoric times. Sun radiates 180 billion MW of energy over the earth. Solar energy can be utilized through two different routes, as solar thermal route and solar photovoltaic routes. Solar thermal route uses the sun’s heat to produce hot water or air, cook food, drying materials, etc. Solar photovoltaic uses sun’s heat to produce electricity for lighting homes and building, running motors, pumps, electric appliances and lighting.

Solar Drying Technology

The solar dryer is a device which uses solar energy for drying. The solar dryers have many applications in industries and agriculture. Traditionally, drying of agricultural products is done on the open ground directly under the sun. This method is known as open sun drying. This leads to losses due to uncontrolled drying, besides causing contaminated of the product.

Various types of solar dryers have been developed as an alternative to open sun drying and other conventional drying methods. The College of Agricultural Engineering and Post Harvest Technology, CAU, Ranipool, Gangtok, Sikkim has developed a portable solar PV powered force convection solar dryer, which is suitable for drying of 5 kg vegetables particularly chilly per batch at domestic level was developed.

The maximum and minimum temperatures under full load condition for upper and lower tray were 65.30C and 56.50C respectively against the respective maximum and minimum ambient temperatures of 27.90C and 17.20C. The drying rate of chilly varied in range of 0.01-0.11 kg h-1.

Solar water heater technology

Most solar water heating systems have two main parts: a solar collector and a storage tank. The most common collector is called a flat plate solar collector. It consists of a thin flat, rectangular box with a transparent cover that faces the sun, mounted on the roof of building or home. Small tubes run through the box and carry the fluid-either water of other fluid, such as an antifreeze solution to be heated.

The tubes are attached to an absorber plate, which is painted with special coating to absorb the heat. The heat builds up in the collector, which is passed to the fluid passing through the tubes. An insulated storage tank holds the hot water. Presently, the solar water heater is used for domestic, commercial and industrial applications. A temperature of 600C is sufficient for domestic use.

Most domestic solar water heaters are capacity ranging from 100-500 liters of hot water per day. A typical solar water heater can save up to 1500 units of electricity every year, for every 100 litres per day os solar water heater. A solar water heater of 100 litres capacity can prevent emission of 1.5 tons of carbon dioxide per year. Solar water heater has a life of 15 to 20 years and pays back the cost in 3 to 4 hears when electricity is replaced.

Solar water heaters are ranging from 100 litres per day to over 20,000 1 day-1 capacity at 850C to 900C have been installed in hostels, guest houses, hotels, industries, etc. The College of Agricultural Engineering and Post Harvest Technology, CAU, Ranipool, Gangtok, Sikkim has installed 8 (7 units of 1000 litre and 1 unit of 500 liter) natural circulation solar water heaters.

Solar water pumping technology

Water pumping is one of the simplest and most appropriate uses for photovoltaic. From crop irrigation to stock watering to domestic uses, photovoltaic powered pumping system meet a broad range of water needs. In solar water pumping system, the pump is driven by motor run by solar electricity instead of conventional electricity drawn from utility grid.

A solar photovoltaic water pumping system consist of a photovoltaic array mounted on a stand and a motor-pump set compatible with the photovoltaic array. It converts the solar energy into electricity, which is used for running the motor pump set. The pumping system draws water from the open well, bore well, streams, ponds, canal etc.

Solar cooking technology

Solar cooker is a device which uses solar energy for cooking and thus saving petroleum resources (LPG & Kerosene), fuel wood, and electrical energy to a large extent. It is a simple cooking unit, ideal to domestic cooking during most of the year except during the monsoon seasons, cloudy days and winter months. There ae different types of solar cookers are available in world wide. The box type solar cooker is most popular.

The box type solar coolers with a single reflecting mirror are the most popular in India. It works as an airtight box with double glass covers. A reflector is placed over it for boosting the solar radiation thus its temperature increases.

Box type solar cookers are capable for cooking different types of food including rice, vegetables, pulses, chicken and fish, etc. A family size box type solar cooker is sufficient for 4 to 5 members and save about 3 to 4 cylinders of LPG every year. The life of this solar cooker is up to 15 years.

Bio-energy conversion technologies

Bio-energy comprises different forms of usable energy obtained from materials referred to as biomass. Bio-energy consists of solid, liquid, or gaseous fuels. A biomass is a biological material in sloid, liquid or gaseous form that has stored sunlight in the form of chemical energy. Several types of biomass can be used, with the proper technology and equipment, to produce energy.

The most commonly used type of biomass is wood, either round wood or wood waste from industrial activities. Wood and wood waste can be combusted to produce heat used for industrial purposes, for space and water heating, or to produce steam for electricity generation. Through anaerobic digestion, methane can be produced from solid landfill waste or other biomass materials such as sewage, manure and agricultural waste.

Sugars can be extracted from agricultural crops and, through distillation, alcohols can be produced for use as transportation fuels. As well, numerous other technologies exist or are being developed to take advantage of other biomass feedstock.

Energy efficient improved biomass cooking stoves

Energy for cooking is a basic necessity. This is largely provided by fuel wood. In India, about 90% of households in rural areas, 75% in the semi urban areas and 25% in the urban areas use firewood stoves. Mostly villagers cook their food on traditional cook stove, which is installed by beneficiaries by placing three stones. There is no provision for smoke emission in these traditional cook stoves.

The traditional cook stoves commonly used at present, have low thermal efficiency, only about 7 to 10% of the potential energy in wood is utilized in the cooking process and consequently consume more fuel. Improved biomass cook stoves are designed to clean up combustion, the hot gases can be forced to contact the pot, increasing efficiency without increasing harmful emissions. Such stoves save wood and reduce smoke.

Improved stove is quicker to start, needs little tending and can meet the specific needs of a cook. Double Pot Energy Efficient Improved Biomass Cook Stove was designed and developed for hilly regions where small utensils are used for cooking. The average thermal efficiency of these double pot energy efficient improved biomass cook stoves were observed as 28.65%, which is within the range of values of thermal efficiency of several similar works all over the world.

The thermal efficiency of several similar works all over the world. The thermal efficiency of the double pot energy efficient improved cook stove was about 200% more than that of the traditional biomass cook stove. Thus, the use of the double pot energy efficient improved biomass cook stoves will conserve the biomass and fuel wood.

Biogas technology

Biogas is a combustible gaseous fuel that is collected from the microbial degradation of organic matter in anaerobic conditions. Biogas is principally a mixture of methane (CH4) and carbon dioxide (CO2) along with other trace gases. Biogas can be collected from landfills, covered lagoons, or enclosed tanks called anaerobic digesters. The biogas typically has 60% methane and 35% carbon dioxide.

There is also some percentage of hydrogen, nitrogen, oxygen, ammonia, moisture etc. Biogas is commonly made from animal slurry, sludge settled from wastewater and at landfills containing organic wastes. However, biogas can also be made from almost any organic waste has the ability to produce biogas: human excreta, slurry, animal slurry, fruit and vegetable waste, slaughterhouse waste, meat packing waste, dairy factory waste, brewery and distillery waste, etc.

Fiber rich wastes like wood, leaves, etc. make por feed stocks for digesters as they are difficult to digest. Many waste waters contain organic compounds that may be converted to biogas including municipal waste water, food processing wastewater and many industrial wastewaters. Solid and semi-solid materials that include plant or animal matter can be converted to biogas.

The types of biogas plant design popular are: floating drum type, fixed dome-type and bag-type portable digester. The fixed -dome type biogas plant has become more popular across Asia.

Conclusion

Renewable energy technologies produce sustainable and clean energy from different renewable energy sources. Renewable energy technologies can be widely applied in the farm for sustainable agriculture.

Renewable energy technologies are considered as clean sources of energy and optimal use of these resources minimize environmental impacts, produce minimum secondary wastes and are sustainable based on current and future economic and social societal needs.


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