Materials for Solar Energy Conversion. Группа авторов
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      Solar energy is naturally available in the atmosphere which helps to natural dryer type. Especially in developing countries, this type of technology has been utilized for agricultural field. Further, this method split into two groups such as open to sun drying method and direct solar energy crop drying method [1].

       Open to Sun Drying Method

      Benefits:

       ✓ Tropical climatic countries approach this type of drying easily

       ✓ Minimal initial cost

       ✓ No need of skilled labor

       ✓ Maintenance is low

      Disadvantages:

       ✓ Heating process is slow.

       ✓ Food products may be affected by insects, birds, dust, and some microorganisms.

       ✓ Due to irregular climatic changes like as rain and cloudy, product quality and efficiency varied.

       ✓ Sometimes color of the products also changed due to excess or scarcity of proper drying.

       Direct Solar Energy Crop Drying Method

      Advantages:

       ✓ Needs small space for drying

       ✓ Efficiency is higher

       ✓ Prevention from micro-organisms and other foreign particles

       ✓ Easy available in market

       ✓ Maintenance is quite simpler

Schematic illustration of direct solar energy crop drying method.

      Disadvantages:

       ✓ Not suited for a larger capacity of drying foods

       ✓ Reduction of radiation transmission into cover due to moisture condensation occurs

      1.9.2 Forced Circulation Systems

      The device used in the conversion purpose of photovoltaic is known as silicon solar cells. Due to photovoltaic effect, the solar radiation from sunlight incidents on the silicon solar cells where energy conversion occurs from solar energy into electricity. The benefit of this system is minimum labor cost [24]. There is no movable components and simple in construction. The output generated power is easily transferred to other operating source system such as solar home appliances, solar powered vehicle, water pumps, and other needed sources [25, 26].

      1.10.1 Photovoltaic Effect

       Absorbing Materials

      All the photovoltaic cells need light absorbing materials to capture photons and free electrons, which are placed in a cell structure. Silicon cells play a dominant technology in photovoltaic cells [27]. The most commonly used materials are amorphous silicon, crystalline silicon, cadmium telluride, cadmium sulphide, gallium arsenide, and some other materials.

       Silicon

Schematic illustration of photovoltaic module. СКАЧАТЬ