Solar Power in Nepal: – Solar energy is radiant light and heat from the sun, which has always been used by humans through a series of constantly evolving technologies. Solar radiation and secondary solar resources make up the bulk of the renewable energy available on Earth.

It is an important source of renewable energy and its technologies are commonly known as passive or active solar energy, depending on how they capture, distribute or convert solar energy into solar energy.

Active solar technologies include the use of photovoltaic systems, concentrated solar energy and solar water heating to use energy. Passive solar techniques include aligning a building with the sun, selecting materials with favorable thermal or light scattering properties and designing spaces in which air circulates naturally.

The large amount of solar energy makes it an extremely attractive source of energy. The United Nations Development Program has determined in its 2000 World Energy Assessment that the annual potential of solar energy is between 1,575 and 49,837 exams (EJ). This is a multiple of the global energy consumption of 559.8 EJ in 2012.

Improving sustainability, reducing pollution, reducing costs of stopping global warming and reducing fossil fuel prices as global benefits. The additional cost of incentives for early adoption should be considered as an investment in learning that should be generalized. ”

Solar energy in the context of Nepal

Nepal receives an optimal sunlight of approximately 300 days on average during the year with a total solar radiation of 3.6 – 6.2 kWh / m2 / day with an average of 4.7 kWh / m2 / day, making solar energy a significant renewable alternative for power generation in Nepal.

The significant decrease in the cost of photovoltaic solar technology (approximately 80% less than in 2008) has also been beneficial for the development of photovoltaic solar energy projects. There are about 943 medium-sized photovoltaic solar units for the communications sector, which contribute to 1.5 MW of electricity.

Solar power in nepal
Solar power

Around 225,000 solar photovoltaic appliances are installed throughout Nepal, with a total contribution of 5.36 MWp. Rapid technological advances in this field, which increase efficiency and significantly reduce costs, have made solar energy attractive to investors. With the decrease in the cost of solar photovoltaic technology and its reliability and sustainability, interest in solar energy has grown rapidly in the case of Nepal.

Nepal Telecom was one of the first companies to install Solar PV in the 1970s. Following the establishment of the Center for Alternative Energy Sources (AEPC) in 1996 with the main objective of promoting alternative energy sources in Nepal, more than 70,000 systems off-grid domestic solar, approximately 2,000 off-grid institutional systems, mainly for schools, hospitals, VHF transmitters, etc. have been installed so far Curiously, on October 31, 2012, the first solar photovoltaic system connected to the network with a capacity of 1.1 kWp was installed in the Energy Studies Center of the Pulchowk Campus of the Engineering Institute (IOE) .

Photovoltaic solar systems connected to the 3.3 kWp network in the Min Bhavan substation of the Nepal Electricity Authority and 1.1 kWp of energy in RIDS-Nepal (Integrated Rural Development Services – Nepal), Imadol, Lalitpur, they were installed in December 2012, respectively. February 2013 finished. These initiatives were taken by the SUPSI project in Nepal mainly for research purposes.

The widespread use of photovoltaic (PV) solar energy is of growing interest in both national and global contexts. In 2005, the worldwide installed capacity of photovoltaic solar energy was only 5.1 GW; However, by 2016, this capacity had multiplied by 40 to 303 GW, of which 75 GW were only added last year.

Of the total global capacities, only China represents around 78 GW, followed by Japan with 43 GW. With a growth of more than 40 times in the global photovoltaic solar power capacity in just a decade, photovoltaic solar technology is the fastest growing technology among all renewable energy technologies.

Energy, food, minerals, qualified human resources, the financial situation and freshwater are the main components of a country’s development, while energy and freshwater are the two most important commodities to improve quality of people’s lives. By understanding the position and meaning of these resources and using them consciously / wisely, you can change the face of the country and people’s livelihood.

Nepal is a landlocked country with a small area, surrounded by India and China. In this small and beautiful environment, the biosphere, the climate (Arctic / Alpine to tropical) and the landscape (lowlands from 72 m to the highest peaks at 8848 m above sea level) are diverse.

It does not have its own coal and oil resources and does not have access to the sea / ocean. In the last six years, fossil fuel prices have risen to an all-time high, and the world is in the deepest recession since the Great Depression. Geopolitical events are constantly raising prices.

The short-term risks to political stability and economic activity arising from the global dependence on fossil fuels are once again as obvious as the long-term threat to environmental sustainability. To overcome this dependence, every country in the world needs a clean energy revolution.

Such a revolution would improve global energy security, promote long-term economic growth and address environmental problems such as anthropogenic climate change.

Solar radiation, one of the main sources of fuel, is abundant everywhere and also in Nepal. The solar radiation incident on the surface naturally regulates / drives atmospheric circulation, the Earth’s climate and the Earth’s biosphere. He is also the creator of all other sources of energy that exist on Earth.

Even the most commonly used energy resources, such as fossil fuels, are an indirect result of solar energy trapped in time. It operates solar installations and generates electricity as one of the best clean and alternative energies.

In 2008/09, the total energy consumption in Nepal was 410,000 TJ. The MOF consumption data shows a coverage of 85% by traditional resources . The average global solar radiation in Nepal varies between 3.6 and 6.2 kWh / m2 per day, the sun shines approximately 300 days per year, the amount of sunshine hours is almost 2100 hours per year and the average solar intensity is approximately 4.7 kWhm- 2 Day 1 (= 16.92 MJ / m2 per day) is greater than 4.38 kWh / m2 per day (15.8 MJ / m2 per day) as measured by Lao PDR.

Therefore, Nepal is in a favorable area of ​​sun protection in the world, although data in Nepal was based on one year and in few places, while data in Lao PDR was based on a few years and on the whole country. Therefore, long-term solar energy data is required in many places to confirm this statement.

In view of the above considerations, the country’s total energy production potential with a total area of ​​147,181 square kilometers will be 83,000 GWh / day = 18.36 TW, assuming an efficiency of 12% of the photovoltaic (PV) module.

This is more than the current energy demand in the world (= 13 TW). Solar energy, with the tremendous potential to multiply current global energy demand, is therefore the best alternative to fossil fuels to obtain more sustainable and reliable energy options. Well-available solar radiation data is the key to planning and simulating all solar energy applications.

The installed capacity of the plants connected to the national network is 689.3 MW, while the maximum electricity demand for 2011/12 was 1056.90 MW and the anticipated electricity demand for 2012/13 and 2013/14 is 1163.20 MW or 1271 respectively. 70 MW Theoretically, technically and economically feasible hydroelectric potential was estimated at approximately 83,000 MW, 45,000 MW and 42,000 MW, respectively.

In practice, energy sources are limited, on the one hand, and 1.35% of Nepal’s population growth continues to press for additional energy needs. Electricity consumption and the number of consumers is increasing at an annual rate of around 9%, while the generation of an additional power plant is almost stagnant and immediate and critical management is also not profitable.

The easily available and indelible nature of the solar energy source is found in one of the most important places among the various possible alternative energy sources. The development, simulation and design of many solar energy applications and the installation of solar panels require a precise database of solar radiation in specific locations and locations.

In these circumstances and given that 52% of Nepalese households do not have access to electricity, the growth of solar radiation data is crucial for the development of national rural energy programs in general and for the development of solar technology in particular.

The public and private sector is not only desirable for a substantial investment in these technologies, it is the best option without alternative to solar energy.

Solar power potential in Nepal

The earth receives 174 petawatts (PW) of incident solar radiation (solar radiation) in the upper atmosphere. Around 30% are thrown back into space, while the rest are absorbed by clouds, oceans and land masses.

The spectrum of sunlight on the earth’s surface extends primarily over the near visible and infrared regions with a small portion in the near ultraviolet region. The majority of the world’s population lives in areas with solar radiation of 150-300 watts / m² or 3.5-7.0 kWh / m² per day.

Solar radiation is absorbed by the Earth’s surface, the oceans, which cover about 71% of the Earth’s globe, and the atmosphere. Hot air, which contains evaporated water from the oceans, rises and causes atmospheric circulation or convection.

When the air reaches a high altitude where the temperature is low, water vapor condenses into clouds that rain on the earth’s surface and complete the water cycle. The latent heat of condensation of the water improves convection and creates atmospheric phenomena such as wind, cyclones and anticyclones.

Sunlight absorbed by the oceans and land masses maintains the surface at an average temperature of 14 ° C. Through photosynthesis, green plants convert solar energy into chemically stored energy that produces food, wood and biomass from which They extract fossil fuels.

In 2002 this was more energy in one hour than the world consumed in one year. Photosynthesis captures about 3,000 EJ biomass per year. The amount of solar energy that reaches the surface of the planet is so large that there are about twice as many non-renewable resources on Earth as coal, oil, natural gas, and uranium together in one year.

The potential solar energy that humans could use differs from the amount of solar energy available near the Earth’s surface, as factors such as geography, climate variability, cloud cover, and land available to humans make up more solar energy do we have. available, you can buy limit.

Geography influences the potential of solar energy, as the areas closest to the equator have a greater amount of solar radiation. However, the use of photovoltaic energy that can follow the sun’s position can greatly increase the potential of solar energy in areas far from the equator.

Time fluctuations affect the potential of solar energy because there is little solar radiation at night on the earth’s surface that can be absorbed by solar panels. Cloud cover can affect the potential of solar panels as clouds block sunlight and reduce available solar cell light.

In addition, the availability of land has a major impact on available solar energy since solar panels can only be installed on land that would otherwise be unused and suitable for solar panels.

Roofs have proven to be a suitable place for solar cells, as many people have discovered that they can collect energy directly from their homes in this way. Other areas suitable for solar cells are areas that are not used by companies in which solar modules can be built.

Solar technologies are passive or active, depending on how they capture, transform, and distribute sunlight, and allow the use of solar energy at various levels of the world, mainly depending on the distance to the equator.

Although solar energy is primarily concerned with the use of solar radiation for practical purposes, all renewable energies, with the exception of geothermal and tidal energy, derive their energy directly or indirectly from the sun.

Active solar technologies use photovoltaics, concentrated solar energy, solar thermal collectors, pumps and fans to turn sunlight into useful results. Passive solar technologies include the selection of materials with favorable thermal properties, the design of rooms with natural air circulation and the reference of the position of a building to the sun.

Active solar technologies increase energy supply and are considered supply technologies, while passive solar technologies reduce the need for alternative resources and are generally considered as demand technologies.

Power generation from solar

Solar energy is the translation of sunlight into electricity, either directly with photovoltaic (PV) or indirectly with focused solar energy (CSP). CSP systems use lenses or mirrors and tracing systems to focus a large percentage of the sunlight onto a small beam. Photovoltaic converts light into electricity through the photoelectric effect.

Solar energy is expected to be the world’s largest energy source by 2050. Photovoltaic solar energy and concentrated solar energy contribute 16 to 11 percent of total global consumption. After another year of rapid growth, in 2016 Solar generated 1.3% of global electricity.

Commercial concentrated solar power plants were first developed in the 1980s: the 392 MW Ivanpah power plant in the Californian Mojave Desert is the largest solar power plant in the world. Other large solar power plants include the Solnova solar power plant with 150 MW and the Andasol solar power plant with 100 MW in Spain.

The 250 MW Agua Caliente solar project in the USA UU. And the 221 MW Charanka Solar Park in India is the largest photovoltaic system in the world. Solar projects of more than 1 GW are being developed, but most of the photovoltaic energy used is used in small roof systems with less than 5 kW, which are connected to the grid via network and / or energy data measurements.


In the last two decades, photovoltaics (PV) – also known as photovoltaic solar energy – has evolved from a niche market for small applications to an important source of energy. A solar cell is a device that uses the photoelectric effect to convert light directly into electricity.

The first solar cell was built in the 1880s by Charles Fritts. A german engineer, dr. med. Bruno Lange, a photocell that uses silver selenide instead of copper oxide. After Russell Ohl’s work in the 1940s, the researchers Gerald Pearson, Calvin Fuller and Daryl Chapin 1954 developed the crystalline silicon solar cell.

These first solar cells cost $ 286 / watt and achieve efficiencies of 4.5-6%. By 2012, the available efficiencies were over 20% and the maximum efficiency of photovoltaic research more than 40%.

Concentrated solar energy

Solar energy concentration (CSP) systems use lenses or mirrors and tracking systems to focus a large portion of the sunlight onto a small beam. There is a wide range of concentration technologies. Most advanced are the Parabolzylinder, the linear Fresnel reflector, the Stirling housing and the solar tower.

There are different techniques to follow the sun and focus the light. In all of these systems, concentrated sunlight heats a working fluid and then uses it to generate energy or store energy.

Application of Solar energy in Nepal

Architecture and urban planning.

Sunlight has influenced the design of buildings since the beginning of architectural history. Advanced methods of solar architecture and urban planning were first used by the Greeks and Chinese, who directed their buildings south to provide light and warmth.

When tuned to the weather and the environment, these features can create well-lit spaces that are within a comfortable temperature range. The Megaron de Socrates house is a classic example of passive solar design.

The latest approaches to solar design use computer models that combine solar lighting, heating and ventilation systems in an integrated solar design package. Active solar systems such as pumps, fans and switchable windows can complement the passive design and improve system performance.

The urban heat islands (UHI) are agglomerations with higher temperatures than the surrounding area. Higher temperatures are the result of higher absorption of solar energy by urban materials such as asphalt and concrete, which have lower heat capacities and albedo than the natural environment.

An easy way to counteract the UHI effect is to bleach buildings and roads and plant trees in the area. A hypothetical “cold communities” program in Los Angeles predicted that the city’s temperature could be reduced by about 3 ° C at an estimated cost of $ 1 billion, representing an estimated total annual benefit of $ 530 million. Reduction of air conditioning There are costs and savings in medical care.

Agriculture and horticulture

Agriculture and horticulture strive to optimize solar energy production to optimize crop productivity. While sunlight is generally considered an abundant resource, the exceptions highlight the importance of solar energy for agriculture.

During the short growing seasons of the Little Ice Age, French and English farmers used fruit walls to maximize the solar energy collection. These walls acted as thermal masses and accelerated maturation by keeping the plants warm. The first fruit walls were built perpendicular to the ground and to the south, but over time, sloping walls were built to make better use of the sunlight.

Greenhouses convert sunlight into heat, which allows the production and growth (indoors) throughout the year of specialized crops and other crops that do not match the local climate.

Primitive greenhouses were used for the first time in Roman times to produce cucumbers for the Roman emperor Tiberius throughout the year. The first modern greenhouses were built in Europe in the 16th century to protect exotic plants brought from exploration abroad.

Greenhouses remain an important part of horticulture today, and polyethylene tunnels and series decks have also used transparent plastic materials with a similar effect.


The development of a car with solar energy has been a technical objective since the 1980s. The World Solar Challenge is a biennial race of cars with solar energy in which teams of universities and companies compete with each other along 3,021 kilometers between Darwin and Adelaide in central Australia. Founded in 1987, the average speed of the winner was 67 km / h, and in 2007 the average speed of the winner had improved to 90.87 km / h.

Some vehicles use solar panels for auxiliary power, for example. As for the air conditioning to keep the interior cool and thus reduce fuel consumption.

In 1975, the first practical solar ship was built in England. Until 1995, passenger ships with photovoltaic modules went on the market, which are widely used today. In 1996, Kenichi Horie crossed the Pacific for the first time with solar energy, and the Sun21 catamaran crossed the Atlantic for the first time in winter 2006-2007 with solar energy.

There were plans to go around the world in 2010. The Astro Flight Sunrise drone completed the first solar flight in 1974. On April 29, 1979, the Solar Riser made its first flight in a flying machine powered by solar energy, fully controlled by humans, which reached a height of 12 meters. In 1980, the Gossamer Penguin made the first piloted flights driven exclusively by photovoltaic energy.

The developments then returned to unmanned aerial vehicles (UAVs) with the Pathfinder (1997) and subsequent constructions. The height record for a rocket-powered aircraft in 2001 was 29,524 meters. The Zephyr Developed by BAE Systems, the solar plane is the latest in a series of record planes that completed a 54-hour flight in 2007.

For 2010, months of flights were planned. Since 2016, Solar Impulse, an electric airplane, is in use and is currently going around the world. It is a single-seat plane that works with solar cells and can start on its own. The design allows the aircraft to remain in the air for several days.

A solar globe is a black globe full of normal air. When sunlight shines on the balloon, the indoor air heats and expands, creating a buoyant force similar to that of an artificially heated hot air balloon.

Some solar balloons are large enough for human flight, but the use is generally limited to the toy market because the ratio between the surface and the payload is relatively high.

Fuel production

These processes can balance the energy that would otherwise come from fossil fuels and also convert solar energy into storable and transportable fuels. Chemical reactions induced by the sun can be subdivided into thermochemical or photochemical reactions.

A variety of fuels can be produced by artificial photosynthesis. Multi-electronic catalytic chemistry involved in the production of carbon-based fuels (such as methanol) from the reduction of carbon dioxide is a challenge.

A possible alternative is the production of hydrogen from protons, although the use of water as a source of electrons (as in plants) requires mastery of the multi electronic oxidation of two molecules of water to molecular oxygen. Some planned to operate solar power plants on the shores of metropolitan areas by 2050: the distribution of seawater, which supplies hydrogen to the power plants of neighboring fuel cells, and the by-product of pure water, which flows directly to the system water municipal.

Hydrogen production technologies have been an important area of ​​research in solar chemistry since the 1970s. In addition to electrolysis by photovoltaic or photochemical cells, several thermochemical processes have been investigated.

One of these routes uses concentrators to decompose water at high temperatures (2,300 to 2,600 ° C) into oxygen and hydrogen. Thermochemical cycles, characterized by the decomposition and regeneration of reagents, provide another route for hydrogen production.

The Solzinc process, which is being developed at the Weizmann Institute of Science, decomposes zinc oxide (ZnO) in a 1 MW solar oven at temperatures above 1,200 ° C. This initial reaction produces pure zinc, which can then become hydrogen with water

Energy storage methods

Thermal mass systems can store solar energy in the form of heat at normal home temperatures during daily or seasonal seasons. Heat storage systems generally use readily available materials with high specific heat capacities, such as water, earth and stone.

Sophisticated systems can reduce maximum demand, change shelf life to non-productive times and reduce general heating and cooling requirements.

Another means of thermal storage are phase change materials, such as paraffin wax and Glauber salt. These materials are economical, readily available and can provide useful domestic temperatures (approximately 64 ° C or 147 ° F). The “Dover House” (in Dover, Massachusetts) was the first to use Glauber salt heating in 1948.

Solar energy can also be stored with molten salt at high temperatures. The Solar Two project used this energy storage method to store 1.44 terajoules (400,000 kWh) in its 68 m³ storage with an annual storage efficiency of approximately 99%.

Off-grid photovoltaic systems traditionally use rechargeable batteries to store excess energy. For network-based systems, excess power can be fed to the transmission network, while standard network power can be used to eliminate bottlenecks. Net measurement programs grant credit to domestic systems for each flow that feeds the network.

This is done by resetting the meter when the house produces more electricity than it consumes. If the net electricity consumption is less than zero, the kilowatt-hour credit is transferred the following month. Other approaches include the use of two meters to measure energy consumption versus generated energy.

This is less common due to the higher installation cost of the second meter. Most standard meters measure exactly in both directions, so a second meter is not required.

Hydropower from storage by pumping stores energy in the form of water that is pumped when energy is available from a lower altitude reservoir to a higher altitude reservoir. The energy is recovered when the demand is high releasing the water, turning the pump into a hydroelectric power generator.

Rural electrification in Nepal is very low due to topographic conditions and at the same time to the purchasing power of consumers. This unfortunate combination of obstacles is documented in the fact that 56.7% of the Nepalese population has no access to electricity. In rural Nepal, 17 million people lack electricity.

State funds are insufficient to address the problem in question, therefore, in 2003/04 GoN adopted a policy and created the Community Electrification Program to accelerate the electrification process. The model is that communities buy energy in bulk from NEA and manage / operate the local system through community organizations called Community Rural Electrification Entities (CREE).

The price that CREE pays for energy in bulk is lower than the lowest rate for the consumer. Revenue can be spent for the operation and maintenance of the system.

230 communities responded positively to this initiative and have deposited 5% (as a precondition for being part of the program) of the anticipated costs to the NEA’s Community Rural Electrification Department.

Another 188 agreements have already been signed and 444 additional community applications have been registered. 116 communities already have access to electricity under this agreement (20% local contribution, 80% subsidies from the Government of Nigeria).

Among the 230 communities that have already paid 5%, a large number will not be able to fulfill their obligation to reach the remaining 15%. In addition, communities generally lack the management and technical skills necessary to operate and administer the system properly.

Integration to the solar energy network

Both solar and wind energy are variable renewable energies, which means that all available production must be taken whenever it is available by moving through the transmission lines to where it can be used now.

Since solar energy is not available at night, the storage of your energy is potentially a major problem, particularly in isolated networks and for future scenarios of 100% renewable energy to have a continuous availability of electricity.

Solar electricity is inherently variable and predictable according to the time of day, location and seasons. In addition, solar energy is intermittent due to day / night cycles and unpredictable weather.

The special challenge that solar energy represents in any utility company varies significantly. In a peak summer utility, solar energy adapts well to cooling demands during the day. In peak winter profits, solar energy displaces other forms of generation, reducing its capacity factors.

In an electrical system without storage of energy from the grid, the generation from stored fuels (coal, biomass, natural gas, nuclear) must rise and fall in reaction to the increase and fall of solar electricity (see charge after the power station electric).

While hydroelectric and natural gas plants can respond quickly to changes in load, coal, biomass and nuclear plants generally take considerable time to respond to the load and can only be programmed to follow predictable variation.

Depending on local circumstances, beyond approximately 20–40% of the total generation, intermittent sources connected to the network such as solar tend to require investments in some combination of network interconnections, energy storage or side management of demand. The integration of large amounts of solar energy with existing generation equipment has caused problems in some cases.

For example, in Germany, California and Hawaii, electricity prices are known to be negative when solar energy generates a lot of energy, displacing existing base charge generation contracts.

Conventional hydroelectricity works very well in conjunction with solar energy; Water can be retained or released from a reservoir as necessary. When an adequate river is not available, pumping storage hydroelectricity uses solar energy to pump water to a high reservoir on sunny days, then the energy is recovered at night and in bad weather releasing water through a hydroelectric plant to a low reservoir where the cycle can begin again.

This cycle can lose 20% of the energy due to round-trip inefficiencies, this in addition to construction costs add to the expense of implementing high levels of solar energy.

Concentrated solar power plants can use heat storage to store solar energy, for example. B. in high temperature molten salts. These salts are an effective storage medium because they are economical, have a high specific heat capacity and can supply heat at temperatures compatible with conventional energy systems.

This method of energy storage is used, for example, in the Solar Two power plant, which stores 1.44 TJ in its 68 m³ storage tank, enough to deliver a complete production of almost 39 hours with an efficiency of approximately 99%.

In independent photovoltaic systems, batteries are traditionally used to store excess energy. With a photovoltaic system connected to the network, excess electricity can be fed to the network. The net measurement and feeding rates give these systems a credit for the electricity they generate.

This credit balances the power provided by the network when the system cannot meet demand and effectively trades with the network instead of storing excess energy. Loans generally extend from month to month and the remaining surpluses are settled annually.

If wind and sun represent only a small part of the grid’s energy, other generation techniques can adjust their performance accordingly. However, as these forms of variable power increase, an additional balance in the network is required. As prices fall rapidly, photovoltaic systems increasingly use rechargeable batteries to save a surplus that will be used later in the night.

The batteries used for network storage stabilize the power grid by balancing maximum loads, usually for a few minutes, in exceptional cases for hours. In the future, cheaper batteries could play an important role in the electricity grid, as they can be recharged at a time when generation exceeds demand and can power its energy stored in the network when demand is greater than generation.

Although not allowed by the US National Electrical Code. UU., It is technically possible to use a “Plug and Play” photovoltaic inverter. A recent review article found that careful system design would allow such systems to meet all technical, if not all, safety requirements.

There are several companies that offer plug-and-play solar systems on the Internet. However, there is concern that the installation of solar systems will reduce the enormous advantage of using solar energy over fossil fuels.

Common battery technologies used in today’s domestic photovoltaic systems include the valve-regulated lead-acid battery, a modified version of the conventional lead-acid battery, as well as nickel-cadmium and lithium-ion batteries.

Lead-acid batteries are currently the predominant technology in small residential photovoltaic systems due to their high reliability, low self-discharge and investment and maintenance costs, despite a shorter lifespan and lower energy density.

Lithium-ion batteries could replace lead-acid batteries in the near future, as they are developing further and lower prices are expected due to economies of scale created by large-scale production facilities, such as Gigafactory 1 -ion electric car batteries. Sockets can serve as future storage devices in a vehicle-to-network system.

Since most vehicles are parked on average 95% of the time, their batteries could be used to allow energy to flow from the car to power lines and vice versa. Other rechargeable batteries used for distributed photovoltaic systems include sodium sulfur and vanadium redox batteries, two known types of molten salts or flow batteries.

The combination of wind power and photovoltaic solar energy has the advantage of complementing the two sources, since peak operating times for each system occur at different times of the day and year.

Therefore, the power generation of such solar hybrid energy systems is more constant and less variable than either of the two subcomponent systems. Solar energy is seasonal, especially in north / south climates, away from the equator, suggesting that long-term seasonal storage is required in a medium such as hydrogen or pumped hydroelectric power.

Also, in this field of artificial photosynthesis is being investigated. Using nanotechnology, solar energy is stored in chemical bonds by dividing water to produce hydrogen fuel, or by using carbon dioxide to produce biopolymers such as methanol.

High-level researchers in this field have advocated a global project on artificial photosynthesis to address critical issues of energy security and environmental sustainability.

Environmental impacts of solar energy.

Avoid the production of greenhouse gases.

The life cycle of greenhouse gas emissions from solar energy varies from 22 to 46 grams (g) per kilowatt-hour (kWh), depending on whether thermal or photovoltaic solar energy is being analyzed. This could be reduced to 15 g / kWh in the future.

By way of comparison (weighted averages), a gas combined cycle power plant emits about 400-599 g / kWh, an oil power plant 893 g / kWh, a coal power plant 915-994 g / kWh or with Carbon capture and storage of approximately 200 g / kWh and a high geothermal temperature, Power Plant 91-122 g / kWh.

The intensity of hydroelectric, wind and nuclear life cycle emissions in 2011 is lower than that of solar energy, as published by the IPCC and discussed in the article on greenhouse gas emissions from the life cycle of Energy sources.

As with all energy sources whose emissions during the life cycle were mainly in the construction and transportation phases, the switch to low-carbon electricity in the manufacture and transport of solar equipment would further reduce carbon emissions.

BP Solar has two factories built by Solarex (one in Maryland, the other in Virginia), where all the energy needed to manufacture solar panels is solar panels. A 1-kilowatt system eliminates the burning of approximately 170 pounds of coal and 300 pounds of carbon dioxide that are not released into the atmosphere, saving up to 105 gallons of water per month.

The National Laboratory of Renewable Energy (NREL) of the United States, by harmonizing the different estimates of greenhouse gas emissions in the life cycle of photovoltaic solar energy, discovered that the most critical parameter is the site’s solar radiation: The greenhouse gas emission factors for photovoltaic solar energy are inversely proportional to solar radiation.

For a typical location in southern Europe with a solar radiation of 1700 kWh / m2 / year, NREL researchers estimated that greenhouse gas emissions were 45 g CO2 e / kWh Under the same conditions, in the case of a solar radiation of 2400 kWh / m2 / year in Phoenix, USA. UU., The GHG emission factor would be reduced to 32 g of CO2e / kWh.

The New Zealand Environment Commissioner said that photovoltaic solar energy would have little impact on the country’s greenhouse gas emissions. The country already generates 80 percent of its electricity from renewable sources (especially hydroelectric and geothermal energy) and reaches a peak in national electricity consumption on winter nights, while solar energy production peaks in the summer afternoons.

This means that a large amount of photovoltaic solar energy would displace other renewable generators from fossil power plants.

Energy Payback

The Energy Recovery Time (EPBT) of a power generation system is the time required to generate as much energy as is consumed during production and the life of the system. Due to the improvement of production technologies, the recovery period has been constantly shortened since the introduction of photovoltaic systems in the energy market.

In 2000, the energy recovery time of photovoltaic systems was estimated at 8 to 11 years and in 2006 1.5 to 3.5 years for crystalline silicon photovoltaic systems and 1 to 1.5 years for technologies thin film (southern Europe). These numbers fell to 0.75 to 3.5 years in 2013, with an average of approximately 2 years for crystalline silicon PV and CIS systems.

Another economic measure closely related to the energy recovery time is the energy recovery from inverted energy (EROEI) or inverted energy (EROI). It is the proportion of electricity generated divided by the energy required to build and maintain the equipment. (This is not the same as the Return on Investment (ROI), which varies according to local energy prices, available subsidies and measurement techniques).

With an expected lifespan of 30 years, the EROEI of PV systems is in the range of 10 to all life producing enough energy to reproduce many times (6-31 reproductions). This depends on the type of material, the balance of the system (BOS) and the geographical location of the system.

The consumption of water

Solar energy includes plants with the lowest water consumption per unit of electricity (photovoltaic) and power plants with the highest water consumption (concentrated solar energy with wet cooling systems).

Photovoltaic power plants consume very little water for their operation. The water consumption of the supply-scale life cycle for PV flat panel displays is estimated at 12 gallons per megawatt hour. Only wind energy, which essentially does not consume water during operation, has a lower intensity of water consumption.

However, concentrated solar power plants with wet cooling systems have the highest intensities of water consumption of all conventional types of power plants. Only fossil fuel carbon capture and storage facilities can have higher water intensities.

A 2013 study that compared different energy sources found that the average water consumption for the operation of wet cooled thermal solar power plants was 810 g / MWhr and for the 890 gal / MWhr canal power plants. This was higher than the operational consumption of water (with cooling towers) for nuclear power plants (720 gal / MWh), coal (530 gal / MWh) or natural gas (210).

A study of the National Renewable Energy Laboratory 2011 found similar results: for power plants with cooling towers, water consumption during the operation was 865 gal / MWhr for the CSP channel, 786 gal / MWhr for the CSP tower, 687 gal / MWhr for coal, 672 gallons / MWh for nuclear and 198 gallons / MWhr for natural gas.

The Solar Energy Industries Association determined that the CSP plant in Nevada consumes Solar One 850 gal / MWh. The problem of water consumption is exacerbated because CSP plants are often implemented in dry environments with water scarcity.

In 2007, the US Congress. UU. He ordered the Department of Energy to report on ways to reduce water use by CSP. The subsequent report found that dry cooling technology was available, which could reduce the use of CSP water by 91 to 95 percent, although it is more expensive to build and operate. A 2015 NREL report found that 4 of the 24 CSP power plants in operation in the U.S. UU.

They used 4 dry cooling systems. The four dry cooling systems were the three power plants of the Ivanpah Solar Energy Facility near Barstow, California, and the Genesis Solar Energy Project in Riverside County, California. Of the 15 CSP projects built or developed in the USA. UU. In March 2015, there were 6 wet systems, 7 dry systems, 1 hybrid and 1 unspecified.

Although many old thermoelectric plants with cooling or continuous cooling ponds consume more water than CSP, which means that more water flows through their systems, most of the cooling water flows back to the body of water, which is available for other purposes, and use less water evaporation.

For example, the US coal-fired power plant with continuous cooling consumes 36,350 gal / MWhr, but only 250 gal / MWhr (less than one percent) is lost through evaporation. Since the 1970s, most of the US power plants. UU. They have used circulation systems as cooling towers instead of continuous flow systems.

By Shishir Acharya


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