Solar Technologies

Solar energy has been used for centuries for drying crops, clothes, wood, and crop residues, and heating buildings. But now methods have been developed to make these activities more efficient, and to use solar energy in different ways. There are two main types of solar energy technology: passive solar (heat) and photovoltaic. Selected examples of both are demonstrated at the site.

Solar drier

This is a method for increasing the efficiency and cleanliness of solar drying. Fruit and vegetables are dried on racks in a small chamber with a solid earth back wall and plastic film covering. The drier is constructed from available stone, mud, bamboo and white plastic sheet and built facing south to maximize the sunshine it receives. The design ensures a constant airflow.

Solar cooker

The solar parabolic cooker is a reflecting surface in the form of a parabolic dish which concentrates the solar rays at a focal point on which the cooking pot is placed. The reflector is mounted in such a way that it can be easily adjusted to face the sun. The quantity of heat delivered to the cooking pot is proportionate to the reflector size; very high temperatures can be attained sufficient for most conventional cooking such as rice and lentil soup (dal). The net power of the cooker is approximately 700 watts in good sunshine. Recently Solarsource 1 (an improved parabolic cooker designed and promoted by One Earth) was installed for demonstration.

Solar lamp

The Tukimara solar lamp consists of a small solar photovoltaic module and three tiny semiconductor devices called white light emitting diodes (WLEDs) that convert electricity into white light more efficiently than traditional filament lamps. The three WLEDs together use only about 0.5 Watt of power, much less than the approximately 10 Watt consumption of the conventional solar DC lamps used in Nepal. Solar lamps have strong advantages for rural kitchens, where they provide bright, smoke-free light, with no danger of fire, unlike kerosene lamps. Solar lamps can be used like a torch, and are safe when handled by children. Development of lights using WLEDs has great potential and a big scope for mass use in low cost home lighting systems in rural areas in the Hindu Kush Himalayan Region.

Solaqua solar still

The Solaqua Solar Still uses natural evaporation and condensation to give pure water using solar energy. It removes impurities such as salts, heavy metals, arsenic, and nitrates, and eliminates microbiological organisms and the taste and odour of chlorine to give pure water. This simple technology is appropriate for mountain communities and can be used under harsh mountain conditions. The equipment can produce six litres of purified water per day under sunny conditions. The advantages are the very simple operation and maintenance and cost effectiveness, since only solar energy is required. It is suitable for both rural and urban areas.

Solar oven

  • Cooks 3 to 4 items in 2 hours (enough for a family of 3-4)
  • Can be used in all seasons when there is adequate sunshine 
  • Reduces the consumption of fuel  wood 
  • Reduces the drudgery of firewood collection (usually done by women) 
  • Helps to save the forest and environment
  • Is an efficient use of solar energy

Solar dryer

  • Can dry 6-8 kgs of food in 2 days (depending on thickness and water content)
  • Saves about 40% of drying time compared to in the open
  • Keeps food clean during the drying process and reduces unhygienic exposure to dust, insects, birds, and others
  • Can easily be moved to optimise exposure to the sun 
  • Is an efficient use of solar energy

Solar water disinfecting device (SWAD)

Disease-causing organisms in water are killed by exposure to heat in a process called pasteurisation. Water that has been heated to 65ºC (150ºF) for a short period of time is free from most common harmful microbes and is safe to drink.

  • Can be used to disinfect 6-12 litres of water per day 
  • Helps to reduce consumption of fuel wood, exposure to smoke from burning wood, and the drudgery of collecting wood. 
  • Is an efficient use of solar energy.