Government of Nepal
Ministry of Energy, Water Resources and Irrigation

Alternative Energy Promotion Centre

Making Renewable Energy and Energy Efficiency Mainstream Supply in Nepal
Solar Energy

Solar Photovoltaic (PV) Systems

Photovoltaic (PV) is the conversion of light into electricity using semiconductor materials that

exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. A photovoltaic system employs solar panels, each comprising a number of solar cells, which generate electrical power. PV installations may be ground mounted, rooftop mounted or wall mounted. The mount may be fixed, or use a solar tracker to follow the sun across the sky. Solar PV has specific advantages as an energy source: once installed, its operation generates no pollution and no greenhouse gas emissions, it shows simple scalability in respect of power needs and silicon has large availability in the Earth’s crust. PV systems have the major disadvantage that the power output works best with direct sunlight, so about 10-25 percent is lost if a tracking system is not used. Dust, clouds, and other obstructions in the atmosphere also diminish the power output. Another important issue is the concentration of the production in the hours corresponding to main insolation, which does not usually match the peaks in demand in human activity cycles.

Types of Solar technologies

  • Small Solar Home System
  • Solar Home System
  • Institutional Solar PV System (SPS)
  • Solar PV Pumping for Irrigation
  • Solar PV Pumping for Drinking Water
  • Solar PV Street Lighting
  • Solar Minigrid
  • Solar Rooftop

Small Solar Home Systems and Solar Home Systems (S/SHS) are Solar PV Systems to collect solar energy and store in the battery to use for lighting and some other end-uses like TV, Radio and mobile phone and laptop computer charging. These are limited to 80 watt peak.

Institutional Solar PV Systems are installed for electricity to generate and use for institutional electricity requirement. Schools, Colleges use such systems for power to computers and lab works. Likewise health posts and health centres use for freezing important vaccines and medical materials while religious places also use for lighting as well. Their capacity is used to be 1 kW, 2 kW and even larger in some cases as per requirement.

Solar PV Pumping for Irrigation is one important application of Solar PV System. This has been successful in lifting water from down terrains to farm lands at upper level and also drag underground water for irrigating for easier cultivation and better crops. Such systems are designed according to availability of water, requirement possibility of water pumping during sunshine hours.

Solar PV Pumping for Drinking Water is another important system from the point of view of health and sanitation. This system helps people to bring water from down streams, store it at a tank and distribute through pipes to households or communities. Such systems are designed according to availability of water, requirement possibility of water pumping during sunshine hours.

Solar PV Street Lighting is isolated electricity generation system by Solar PV. The poles are installed with solar panel, battery and other accessories. The system collects electricity in the battery during sunshine hours and discharge to light the installed lights in the poles in the evenings and nights.

Solar Minigrid : In the context of Nepal, solar and solar-wind hybrid mini grids are one of the most innovative technologies deployed to provide energy access to rural and isolated communities, and meet their development needs. In 2011, the first solar-wind hybrid mini grid of 12 kW installed capacity (10 kW wind + 2 kW solar PV) was implemented in Dhaubadi village of Nawalparasi district. Solar mini grids are complementary energy producers that can deliver electricity at the household, business/commercial, community, or industrial/utility levels. Thus, the application of solar mini grids in adequately meeting the local energy demand is flexible and far reaching.

Solar Rooftop : A rooftop solar power system, or rooftop PV system, is a photovoltaic (PV) system that has its electricity-generating solar panels mounted on the rooftop of a residential or commercial building or structure. The various components of such a system include photovoltaic modules, mounting systems, cables, solar inverters and other electrical accessories. Most rooftop PV stations are Grid-connected photovoltaic power systems.

Solar Thermal System: Solar Thermal System is primarily used domestically for space heating, hot water, and in some cases air conditioning. Solar thermal energy is renewable and no fuels are required during the process to generate electricity or mechanical energy. It is also carbon free except for production and transportation; otherwise it is non-polluting. Solar thermal can also be combined with photovoltaic (PVs), in highly efficient cogeneration systems.

Types of Solar Thermal Technologies

  • Solar Water Heater
  • Solar Dryer
  • Solar Cooker 

Solar Water Heating (SWH) is the conversion of sunlight into heat for water heating using a solar thermal collector. A variety of configurations are available at varying cost to provide solutions in different climates and latitudes. SWHs are widely used for residential and some industrial applications. A sun-facing collector heats a working fluid that passes into a storage system for later use. SWH are active (pumped) and passive convection-driven. They use water only, or both water and a working fluid. They are heated directly or via light-concentrating mirrors. They operate independently or as hybrids with electric or gas heaters. In large-scale installations, mirrors may concentrate sunlight into a smaller collector.

Types of Solar Water Heating

  • Vacuum Tube Collector
  • Flat Plate collector

Devices for heating water with solar radiation are Solar Water Heaters. Flat Plate and Vacuum Tube Collector are quite popular for medium temperature application up to 90°C. Mainly used for hot water supply for domestic use, hotel industry and low temperature industrial application.

Solar Dryer

Dehydration of fruits and vegetables is a promising food processing technology that can crease the shelf life of products by nearly a year. It is a value addition process that can save approximately 33% of seasonal agro-product losses. Solar dryers can be used to carry food dehydration without relying on electricity. Many solar dryers have found limited applications due to high capital requirements. Most of these dryers are based on convection as the main mode of heat transfer, and are therefore complex and inefficient. A heat transfer technology based on conduction gives the dryers better efficiency, thereby reducing the processing time by 40%.

Types of Solar Dryer

  • Box Type
  • Flat Plate Type

Solar cooker

Solar cooker is a device which uses the energy of direct sunlight to heat, cook or pasteurise drink and other food materials. Many solar cookers currently in use are relatively inexpensive, low-tech devices, although some are as powerful or as expensive as traditional stoves, and advanced, large scale solar cookers can cook for hundreds of people. Because they use no fuel and cost nothing to operate, many non-profit organizations are promoting their use worldwide in order to help reduce fuel costs (especially where monetary reciprocity is low) and air pollution, and to slow down the deforestation and desertification caused by gathering firewood for cooking.

Types of Solar Cooker

  • Flat Plate Type (Box)
  • Parabolic Trough Type
  • Parabolic Dish Type