Solar power

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Solar power is the conversion of energy from sunlight to electricity, either directly using photovoltaics (PV), indirectly using concentrated solar power, or a combination. The concentrated solar power system uses a lens or mirror and tracking system to focus a large area of ​​sunlight into a small beam. Photovoltaic cells convert light into electric current using a photovoltaic effect.

Photovoltaics was initially used only as a power source for small and medium applications, from calculators supported by single solar cells to remote homes supported by off-grid roof PV systems. Commercialized concentrated solar power generation was first developed in the 1980s. Installation Ivanpah 392 MW is the world's largest solar power plant, located in the Mojave Desert of California.

Because the cost of solar electricity has dropped, the number of solar PV systems connected to the network has grown to millions and the scale of solar power plants with hundreds of megawatts under construction. Solar PV is quickly becoming a low-cost, low-carbon technology to harness the renewable energy of the Sun. The largest photovoltaic power plant currently in the world is 850 million MW Longyangxia Dam Solar Park, in Qinghai, China.

The International Energy Agency is projected in 2014 that under the "high renewal" scenario, by 2050, solar photovoltaic and concentrated solar power will contribute about 16 and 11 percent, respectively, from worldwide electricity consumption, and the sun will be a source the world's largest. electricity. Most solar installations will be in China and India. By 2016, solar power provides only 1% of total electricity production worldwide but grew by 33% per year.

Video Solar power

Mainstream technology

Many industrialized countries have installed significant solar power capacity into their grid to supplement or provide alternatives to conventional energy sources while more and more less developed countries have turned to the sun to reduce dependence on expensive imported fuels (see solar power by country)) . Remote transmission allows remote renewable energy sources to replace the consumption of fossil fuels. Solar power plants use one of two technologies:

• Photovoltaic (PV) systems use solar panels, either on the roof or in ground-mounted solar soil, turning direct sunlight into electricity.
• Concentrated solar power (CSP, also known as "dense sunlight") uses solar thermal energy to create steam, which is then converted to electricity by a turbine.

Photovoltaics

Solar cells, or photovoltaic cells (PV), are devices that convert light into electric current using photovoltaic effects. The first solar cell was built by Charles Fritts in the 1880s. German industrialist Ernst Werner von Siemens was among those who recognized the importance of this discovery. In 1931, German engineer Bruno Lange developed photo cells using silver selenide in place of copper oxide, although prototype selenium cells converted less than 1% of incident light into electricity. Following Russell Ohl's work in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin invented silicon solar cells in 1954. These early solar cells cost 286 dollars/watt and achieved an efficiency of 4.5-6%.

Conventional PV System

The array of photovoltaic power systems, or PV systems, produces a direct current power (DC) that fluctuates with the intensity of sunlight. For practical use this usually requires conversion to a certain desired voltage or alternating current (AC), through the use of an inverter. Some solar cells are connected inside the module. The modules are combined together to form arrays, then tied to the inverter, which produces power at the desired voltage, and for AC, the desired frequency/phase.

Many residential PV systems are connected to the network wherever available, especially in developed countries with large markets. In this grid-connected PV system, the use of energy storage is optional. In certain applications such as satellites, lighthouses, or in developing countries, additional electrical batteries or generators are often added as backup. Such stand-alone power systems allow operations at night and at other times limited sunlight.

Solar power is concentrated

Concentrated solar power (CSP), also called "concentrated solar heat", uses a lens or mirror and a tracking system to concentrate sunlight, then uses the heat generated to generate electricity from conventional steam turbines.

A wide variety of concentrating technologies exist: among the best known are parabolic troughs, compact linear Fresnel reflectors, Stirling dishes and solar powered towers. Various techniques are used to track the sun and focus light. In all these systems the working fluid is heated by concentrated sunlight, and then used for power generation or energy storage. Efficient thermal storage allows up to 24-hour power plants.

A parabolic trough consists of a linear parabolic reflector that concentrates light to a receiver placed along the reflection focal line. The receiver is a tube placed along the focal point of the linear parabolic mirror and filled with working fluid. Reflectors are made to follow the sun during the day by tracking along a single axis. The parabolic trough system provides the best land use factor of any solar technology. The SEGS plant in California and Acciona's Nevada Solar One near Boulder City, Nevada is representative of this technology.

Compact Linear Fresnel Reflectors are CSP-plants that use many thinner mirror strips rather than parabolic mirrors to concentrate sunlight onto two tubes with working fluid. It has the advantage that flat mirrors can be used that are much cheaper than parabolic mirrors, and that more reflectors can be placed in the same amount of space, allowing more sunlight available for use. Concentrating linear fresnel reflectors can be used either in large or more compact plants.

The Stirling solar dish combines dish-parabolic concentrate with a Stirling engine that usually drives an electric generator. The advantage of Stirling solar over photovoltaic cells is the higher efficiency of converting sunlight into electricity and longer lifetime. The parabolic dish system provides the highest efficiency among CSP technologies. Big Dish 50-kW in Canberra, Australia is an example of this technology.

A solar tower uses an array of tracking reflectors (heliostats) to center light on the central receiver above the tower. Power towers can achieve higher (thermal-to-electricity) efficiency than the linear tracking CSP scheme and better energy storage capability than the dish stirring technology. The PS10 Solar Power Generation and the PS20 solar power plant are examples of this technology.

Hybrid system

A hybrid system combines (C) PV and CSP with each other or with other generating forms such as diesel, wind and biogas. The combined form of generation can allow the system to modulate power output as a demand function or at least reduce the nature of solar power fluctuations and non-renewable fuel consumption. Hybrid systems are most commonly found on the islands.

CPV/CSP System

The new CPV/CSP solar hybrid system has been proposed, combining a photovoltaic consoner with a concentrated non-PV solar power technology, also known as concentrated solar thermal.

ISCC system

The R'Mel Hassi power plant in Algeria, is an example of combining CSP with gas turbines, where a 25-megawatt CSP-parabolic trough array completes a combined 130 mb combined gas turbine plant. Another example is the Yazd power plant in Iran.

PVT System

Hybrid PV/T), also known as photovoltaic thermal solar photovoltaic solar thermal converter converts solar radiation into thermal and electrical energy. Such a system incorporates a solar module (PV) with a complementary solar thermal collector.

CPVT System

Concentrated thermal photovoltaic hybrid system (CPVT) is similar to PVT system. It uses concentrated photovoltaic (CPV) instead of conventional PV technology, and combines it with a solar thermal collector.

PV diesel system

It combines photovoltaic systems with diesel generators. Combinations with other renewable energies are possible and include wind turbines.

PV-thermoelectric system

Thermoelectric, or "thermovoltaic" device changes the temperature difference between different materials into electric current. Solar cells use only high frequency parts of radiation, while low-frequency heat energy is wasted. Several patents on the use of thermoelectric devices together with solar cells have been proposed. The idea is to improve the efficiency of combined solar/thermoelectric systems to convert solar radiation into useful electricity.

Maps Solar power

Development and deployment

Initial days

The early development of solar technology began in the 1860s fueled by the hope that coal would soon become scarce. Charles Fritts installed the world's first photovoltaic solar circuit, using efficient 1% selenium cells, on the roof of New York City in 1884. However, the development of solar technology stagnated in the early 20th century in the face of increasing availability, economy and coal utilities and petroleum. By 1974, it was estimated that only six private homes throughout North America were wholly heated or cooled by functional solar systems. The 1973 oil embargo and the 1979 energy crisis led to the reorganization of energy policies worldwide and brought new attention to the development of solar technology. The deployment strategy focuses on incentive programs such as the US Federal Photovoltaics Utilization Program and the Sunlight Program in Japan. Other efforts include the establishment of research facilities in the United States (SERI, now NREL), Japan (NEDO), and Germany (Fraunhofer-ISE). Between 1970 and 1983 the installation of photovoltaic systems grew rapidly, but the decline in oil prices in the early 1980s moderated the growth of photovoltaics from 1984 to 1996.

The mid-1990s to the beginning of 2010s

In the mid-1990s, the development of both residential and commercial solar roofs as well as utility-scale photovoltaic power plants, began to accelerate again due to supply problems with oil and natural gas, global warming concerns, and improving the economic position of PV. relative to other energy technologies. In early 2000, the adoption of feed-in tariffs - the policy mechanisms, which gave priority to renewable energy on the grid and fixed fixed prices for generated electricity - led to high levels of investment security and to the soaring number of PV Spreads in Europe.

Current status

Over the years, solar PV growth worldwide has been driven by the spread of Europe, but has since shifted to Asia, especially China and Japan, and to more countries and regions around the world, including, but not limited to, Australia, Canada, Chile , India, Israel, Mexico, South Africa, South Korea, Thailand and the United States.

worldwide photovoltaics growth has averaged 40% per year 2000-2013 and total installed capacity reaches 303A GW by the end of 2016 with China having the most cumulative installation (78A GW) and Honduras has the highest theoretical percentage of annual electricity usage that can be generated by Solar PV (12.5%). The largest producers are located in China.

Concentrated solar power (CSP) also began to grow rapidly, increasing its capacity almost tenfold from 2004 to 2013, albeit from lower levels and involving fewer countries than solar PV. By the end of 2013, Cumulative CSP capacity worldwide reaches 3,425 MW.

Forecast

In 2010, the International Energy Agency estimates that global solar PV capacity can reach 3,000 GW or 11% of the projected global power generation by 2050 - enough to generate 4.500 TWh of electricity. Four years later, in 2014, the agency projected that, under the "renewable" scenario, solar power can supply 27% of global power generation by 2050 (16% of PV and 11% of CSP). In 2015, analysts estimate that one million homes in the US will have solar power by the end of 2016.

photovoltaic power generation

Desert Sunlight Solar Farm is a 550 MW power plant in Riverside County, California, which uses CdTe thin film modules made by First Solar. In November 2014, 550 megawatts Topaz Solar Farm is the world's largest photovoltaic power plant. This was surpassed by the 579 MW Surya Star complex. The largest photovoltaic power station currently in the world is Longyangxia Dam Solar Park, in Gonghe County, Qinghai, China.

Concentrate on solar power stations

Commercial solar power plant concentrate (CSP), also called "solar thermal power plant", was first developed in the 1980s. The 377 MW Ivanpah Solar Power Facility, located in the Mojave Desert of California, is the largest solar thermal power plant project in the world. Other large CSP plants include Solnova Solar Power Station (150 MW), Andasol solar power plant (150 MW), and Extresol Solar Power (150 MW), all in Spain. The main advantage of CSP is the ability to add heat storage efficiently, allowing power delivery over 24 hours. Because peak electricity demand usually takes place around 5 pm, many CSP power plants use 3 to 5 hours of thermal storage.

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Economy

Cost

Common cost factors for solar power include module costs, frames for holding them, cables, inverters, labor costs, possible soils needed, network connections, maintenance and solar insolation to be received locations. Adjusting inflation, it cost $ 96 per watt for solar modules in the mid-1970s. The enormous increase in process and production drives has brought the figure down to 68 cents per watt in February 2016, according to Bloomberg New Energy Finance data. Palo Alto California signed a wholesale purchase agreement in 2016 that secures solar power to 3.7 cents per kilowatt-hour. And in Dubai the large-scale solar generated by 2016 is only 2.99 cents per kilowatt-hour - "competitive with all forms of fossil-based electricity - and cheaper than most."

Photovoltaic systems do not use fuel, and modules typically last 25 to 40 years. Thus, the cost of capital makes the most of the cost of solar power. Operating and maintenance costs for new-scale solar power plants in the US are estimated at 9 percent of the cost of photovoltaic electricity, and 17 percent of the cost of solar thermal electricity. The government has created various financial incentives to encourage the use of solar power, such as feed-in tariff programs. Also, the renewable portfolio standard implements a government mandate that utilities generate or obtain a certain percentage of renewable power regardless of the increase in energy procurement costs. In many states, RPS objectives can be achieved with a combination of solar, wind, biomass, landfill gas, marine, geothermal, municipal solid waste, hydroelectricity, hydrogen, or fuel cell technology.

Levelization of electricity costs

The PV industry began to adopt calculated electrical costs (LCOE) as a unit of cost. The electrical energy produced is sold in kilowatt-hours (kWh). As a rule of thumb, and depending on the local insolation, 1 watt-peak solar PV capacity attached generates about 1 to 2 kWh of electricity per year. This corresponds to a capacity factor of about 10-20%. The product of the local electricity cost and insolation determine the break-even point for solar power. The International Conference on Solar Photovoltaics Investment, organized by the EPIA, has estimated that PV systems will repay their investors in 8 to 12 years. As a result, since 2006 it has been economical for investors to install photovoltaics for free in return for long-term power purchase agreements. Fifty percent of commercial systems in the United States were installed this way in 2007 and over 90% in 2009.

Shi Zhengrong said that, by 2012, solar power without subsidies is already competitive with fossil fuels in India, Hawaii, Italy and Spain. He said: "We are at a critical point, no longer renewable resources like the sun and the luxurious wind of the rich, they are now starting to compete in the real world without subsidies." "Solar power will be able to compete without subsidies to conventional resources in half the world by 2015".

Current install price

In the 2014 edition of the Road Map Technology report: Solar Energy Photovoltaics , the International Energy Agency (IEA) issued pricing for residential, commercial and utility scale PV systems for eight major markets in 2013 (see table on bottom) . However, the SunShot DOE Initiative has reported much lower US installation rates. In 2014, prices continue to decline. The SunShot Initiative modeled US system prices in the range of $ 1.80 to $ 3.29 per watt. Other sources identify the same price range from $ 1.70 to $ 3.50 for different market segments in the US, and in the highly penetrated German market, prices for residential and small commercial rooftop systems of up to 100 kW drop to $ 1 , 36 per watt (EUR1.24/W) by the end of 2014. By 2015, Deutsche Bank estimates the cost for a small residential rooftop system in the US is about $ 2.90 per watt. The cost for utility scale systems in China and India is estimated to be as low as $ 1.00 per watt.

Grid parity

Grid parity, the point at which the cost of photovoltaic electricity is equal to or cheaper than the price of grid power, is more easily achieved in areas with abundant sunlight and high costs for electricity such as in California and Japan. In 2008, the electricity-levelized charge for solar PV was $ 0.25/kWh or less in most OECD countries. By the end of 2011, full cost is expected to fall below $ 0.15/kWh for most OECD and reach $ 0.10/kWh in brighter areas. This cost level drives three emerging trends: the vertical integration of the supply chain, the origin of the power purchase agreement (PPA) by solar companies, and the unforeseen risks for traditional power generation companies, network operators and wind turbine manufacturers.

Grid parity was first achieved in Spain in 2013, Hawaii and other islands that otherwise use fossil fuels (diesel) to generate electricity, and most of the US is expected to reach grid parity by 2015.

In 2007, Chief Engineer General Electric predicted grid parity without subsidies in the sunny parts of the United States around 2015; other companies estimate an earlier date: solar power costs will be below the grid parity for more than half of residential customers and 10% of commercial customers in the OECD, as long as the price of electricity does not fall until 2010.

Productivity by location

The productivity of solar power in a region depends on solar radiation, which varies throughout the day and is affected by latitude and climate.

The location with the highest annual sun radiation lies in tropical and subtropical dryness. Deserts located at low latitudes usually have some clouds, and can receive sunlight for more than ten hours a day. This hot desert forms the Global Sun Belt that surrounds the world. This belt consists of many land plots in North Africa, South Africa, Southwest Asia, the Middle East, and Australia, and much lesser deserts than North and South America. The eastern Sahara Desert of Africa, also known as the Libyan Desert, has been observed as the brightest place on Earth according to NASA.

Different measurements of solar radiation (direct normal radiation, global horizontal radiation) are mapped below:

Self-consumption

In the case of own solar energy consumption, the payback time is calculated based on how much electricity is not purchased from the grid. For example, in Germany, with an electrical price of 0.25 EUR/kWh and an insolation of 900 kWh/kW, one kWp will save EUR225 per year, and at a cost of installing 1,700 EUR/KWp, the system cost will be returned in less than seven years. However, in many cases, the generation and consumption patterns do not coincide, and some or all of the energy is fed back to the grid. Electricity is sold, and at other times when energy is taken from the grid, electricity is bought. The relative costs and prices obtained affect the economy. In many markets, the price paid to sell PV power is much lower than the price of electricity purchased, which gives an incentive to self-consumption. In addition, separate self-consumption incentives have been used in eg. Germany and Italy. The grid interaction regulation has also included feed-in grid restrictions in several regions of Germany with a high amount of installed PV capacity. By increasing their own consumption, feed-in grids can be limited without restriction, which wastes electricity.

A good match between generation and consumption is the key to high self-consumption, and should be considered when deciding where to install solar power and how to modify the installation. The game can be enhanced with battery or controllable power consumption. However, expensive batteries and profitability may require the provision of other services from them besides an increase in self consumption. Heated storage tanks with electric heaters with heat pumps or heating resistant can provide low-cost storage for own solar power consumption. Movable loads, such as dishwashers, dryers and washing machines, can provide controllable consumption with only limited effect on the user, but the effect on solar power consumption may be limited.

Price pricing and energy incentives

The political objective of the incentive policy for PV is to facilitate early small-scale deployment to start growing the industry, even when the cost of PV is significantly above the grid parity, to enable the industry to achieve the economies of scale required to reach the power grid. balance. The policy is applied to promote national energy independence, high-tech employment creation and CO 2 sub substrate reduction. Three incentive mechanisms are often used in combination as an investment subsidy: the authorities restore part of the system installation costs, electric utilities purchase PV power from producers under multi-year contracts with guaranteed levels, and Solar Renewable Energy Certificates (SRECs)

Rebates

With investment subsidies, the financial burden falls on taxpayers, while with feed-in tariffs, additional fees are distributed across utility customer bases. Although investment subsidies may be simpler to manage, the main argument in favor of feed-in tariffs is a quality boost. The investment subsidy is paid as a function of the name plate capacity of the installed system and does not depend on actual output over time, thereby rewarding excess power and tolerance for poor durability and maintenance. Some power companies offer discounts to their customers, such as Austin Energy in Texas, which offers $ 2.50/watt installed up to $ 15,000.

Net measurement

In net measurements, the price of electricity generated equals the price supplied to the consumer, and the consumer is billed on the basis of the difference between production and consumption. Net measurements can usually be made without changes to the standard power meter, which accurately measures power in both directions and automatically reports the difference, and because it allows homeowners and businesses to generate electricity at different times of consumption, effectively using the grid as a storage battery giant. With net measurements, deficits are billed monthly while surpluses are transferred to the next month. Best practices require repeated scrolling of kWh credits. Excess vouchers upon termination of service are lost or paid at rates ranging from wholesale tariffs to retail or above, as well as annual credit surpluses. In New Jersey, the excess annual credit is paid at wholesale rates, such as the remaining credit when the customer stops the service.

Feed-in rate (FIT)

With feed-in tariff, the financial burden falls on the consumer. They reward the number of kilowatt-hours produced over a long period of time, but because rates are set by the authorities, it can lead to overpayments. The price paid per kilowatt-hour under feed-in tariff exceeds the electricity price of the network. Net measurement refers to cases in which the price paid by the utility equals the price charged.

The complexity of approval in California, Spain and Italy has prevented comparable growth to Germany despite better return on investment. In some countries, additional incentives are offered for BIPV compared to stand-alone PVs.

• France EUR 0.16/kWh (compared semi-integrated) or EUR 0.27/kWh (compared stand-alone)
• Italy EUR 0.04-0.09 kWh
• Germany EUR 0.05/kWh (facade only)

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As an alternative, SREC allows market mechanisms to fix the price of the resulting solar power subsystem. In this mechanism, production targets or renewable energy consumption are set, and utilities (more technically Compliance Enterprises) are required to purchase renewable energy or face fines (Alternative Compliance Payments or ACPs). Manufacturers are credited for SREC for every 1,000 kWh of electricity generated. If the utility buys this SREC and withdraws it, they avoid paying the ACP. In principle this system provides the cheapest renewable energy, as all solar facilities are eligible and can be installed in most economic locations. Uncertainty about the future value of SREC has led to long-term SREC contract markets to provide their price clarity and allow solar developers to pre-sell and hedge their credit.

Financial incentives for photovoltaics differ across countries, including Australia, China, Germany, Israel, Japan, and the United States and even across states in the US.

The Japanese Government through the Ministry of Commerce and International Industry runs a successful subsidy program from 1994 to 2003. In late 2004, Japan led the world in an installed capacity of PV with more than 1.1 GW.

In 2004, the German government introduced the first large-scale feed-in tariff system, under the German Renewable Energy Act, which resulted in an explosion of PV installations in Germany. Initially, FIT is more than 3x the retail price or 8x the industry price. The principle behind the German system is the 20 year flat rate contract. The value of new contracts is programmed to decrease each year, to encourage industry to provide lower cost to end users. This program has been more successful than expected with more than 1GW installed in 2006, and increased political pressure to lower tariffs to reduce future burdens on consumers.

Furthermore, Spain, Italy, Greece - which enjoyed initial success with the installation of domestic solar heat for hot water needs - and France introduced feed-in rates. Nothing has replicated the decline in FIT programmed into new contracts, making German incentives relatively less and less attractive than other countries. FIT France and Greece offer high premium (EUR 0.55/kWh) to build integrated systems. California, Greece, France and Italy have 30-50% more insolation than the Germans making them more financially attractive. The Greek "roof roof" program (adopted in June 2009 for installation up to 10 kW) has an internal rate of return of 10-15% on current commercial installation costs, furthermore, tax free.

In 2006, California approved the 'California Solar Initiative', offering a choice of investment subsidies or FIT for small and medium systems and FIT for large systems. The small FIT system of $ 0.39 per kWh (much lower than the EU country) ends in just 5 years, and residential investment incentives "EPBB" alternative is simple, on average maybe 20% of the cost. All California incentives are scheduled to decline in the future depending on the function of the amount of PV capacity installed.

In late 2006, the Ontario Power Authority (OPA, Canada) initiated the Standard Offering Program, a precursor to the Green Energy Act, and the first in North America for distributed renewable projects of less than 10 MW. The feed-in rate is guaranteed a flat price of $ 0.42 CDN per kWh over a twenty-year period. Unlike net measurements, all the electricity generated is sold to the OPA at a specified rate.

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Integration grid

Most of the electricity produced worldwide is used immediately, because storage is usually more expensive and because traditional generators can adapt to demand. Yet both solar power and wind power are variable renewable energies, meaning that all available output must be taken whenever available by moving through the transmission line to where it can be used now . Since solar energy is not available at night, saving its energy is potentially an important issue especially outside the network and for a 100% renewable renewable energy scenario forward that has sustainable power availability.

Solar power is inherently variable and predictable based on time, location, and season. In addition the sun is intermittent due to the day/night cycle and unpredictable weather. How many specific solar power challenges in a given electric utility varies significantly. In the peak summer utility, the sun matches the demands of daytime cooling. In the peak winter utility, the sun replaces other forms of generation, reducing their capacity factor.

In electrical systems without grid energy storage, the generation of stored fuels (coal, biomass, natural gas, nuclear) should fluctuate in reaction to the ups and downs of solar electricity (see next power load). While hydropower and natural gas can quickly follow the disjointed sun as weather, coal, biomass and nuclear power plants usually take a while to respond to the load and can only be scheduled to follow predictable variations. Depending on local circumstances, beyond about 20-40% of the total generation, intermittent sources connected networks such as the sun tend to require investment in some combination of network interconnection, energy storage or demand-side management. Integrating large amounts of solar power with existing generation equipment has caused problems in some cases. For example, in Germany, California, and Hawaii, the price of electricity is known to be negative when solar power produces a lot of power, replacing the existing base load generation contract.

Conventional hydroelectric works very well in conjunction with solar power, water can be retained or released from the reservoir behind the dam as required. Where suitable rivers are not available, hydroelectric power plants are pumped using solar power to pump water into high reservoirs on sunny days then energy recovers at night and in bad weather by releasing water through a hydroelectric generator to a low reservoir where the cycle can start again. However, this cycle can lose 20% energy for inefficiency round, this plus the construction cost adds the cost of applying high level of solar power.

Concentrated solar power plants may use thermal storage to store solar energy, such as high temperature liquid salts. These salts are an effective storage medium because they are cheap, have a high specific heat capacity, and can produce heat at temperatures that are compatible with conventional power systems. This energy storage method is used, for example, by a Solar Two power plant, which allows it to store 1.44 TJ in a storage tank of 68 mÃ,³, sufficient to provide full output for nearly 39 hours, with an efficiency of about 99%.

In stand-alone PV battery systems are traditionally used to store excess electricity. With a photovoltaic power system connected to an excess of electrical grid can be sent to the power grid. Net metering and feed-in rate programs give these systems credit for the electricity they produce. These credits offset the electricity provided from the network when the system is unable to meet demand, effectively trade with the power grid instead of storing excess electricity. Credit usually rolls from month to month and every remaining surplus is completed every year. When the wind and the sun are a small part of the power of the network, other generating techniques can adjust their output appropriately, but when these variable strength forms grow, an additional balance on the grid is required. As prices decline rapidly, PV systems are increasingly using rechargeable batteries to store surpluses that will be used at night. The battery used for grid storage stabilizes the power grid by flattening the peak loads normally for several minutes, and in rare cases for hours. In the future, cheaper batteries can play an important role in the power grid, as they can fill during periods when generation exceeds demand and feed energy stored into the grid when demand is higher than generations.

Although not permitted under the US National Electrical Code, it is technically possible to have a "plug and play" PV microinverter. Recent review articles found that careful system design will enable the system to meet all technicalities, although not all safety requirements. There are several companies that sell plug and play solar power systems available on the web, but there are concerns that if people install it themselves, it will reduce the huge labor gains that solar has on fossil fuels.

Common battery technologies used in current home PV systems include a valve that regulates lead-acid batteries - modified versions of conventional lead-acid batteries, nickel-cadmium and lithium-ion batteries. The acid-lead battery is currently the main technology used in small-scale PV housing systems, due to its high reliability, low self-expense and investment and maintenance costs, despite its shorter life span and lower energy density. However, lithium-ion batteries have the potential to replace lead-acid batteries in the near future, as they are being developed intensively and lower prices are expected due to the economies of scale provided by large production facilities such as Gigafactory 1. In addition, Li-ion batteries of plug-in electric cars can serve as future storage devices in a vehicle-to-grid system. Since most vehicles parked an average of 95 percent of the time, their batteries can be used to allow the flow of electricity from the car to the power line and back. Other rechargeable batteries used for distributed PV systems include, sodium-sulfur batteries and redox vanadium, the two main types of molten salts and flow batteries, respectively.

The combination of wind and solar PV has the advantage that the two sources complement each other because the peak operating times for each system occur at different times of the day and year. Power plants such as solar hybrid power systems are therefore more constant and fluctuate less than each of the two component subsystems. Solar power is seasonal, especially in northern/southern climates, away from the equator, indicating long-term seasonal storage needs in media such as hydrogen or pumped hydroelectric power. The Solar Energy Supply Technology Institute of the University of Kassel is testing a combined power plant that connects solar, wind, biogas and hydrostorage to provide power that follows the load from renewable sources.

Research is also conducted in the field of artificial photosynthesis. This involves the use of nanotechnology to store solar electromagnetic energy in chemical bonds, by breaking up water to produce hydrogen fuel or then joining with carbon dioxide to make biopolymers like methanol. Many large national and regional research projects on artificial photosynthesis are now trying to develop techniques that integrate improved light capture, the quantum electron transfer coherence method and cheap catalytic materials that operate under various atmospheric conditions. Senior field researchers have made public policy cases for the Global Project on Artificial Photosynthesis to address important energy security and environmental sustainability issues.

src: news.virginia.edu

Environmental impact

Unlike fossil fuel-based technologies, solar power does not cause harmful emissions during operation, but panel production causes a certain amount of pollution.

Greenhouse gases

Greenhouse gas emissions-the life cycle of the sun is in the range of 22 to 46 grams (g) per kilowatt-hour (kWh) depending on whether solar heat or solar PV is being analyzed. This potentially decreases to 15 g/kWh in the future. For comparison (weighted average), combined cycle powered gas plants emit about 400-599 g/kWh, 893 g/kWh oil-fired power plants, coal-fired 915-994 g/kWh or by capture and storage carbon around 200 g/kWh, and high temperature geothermal. power plant 91-122 g/kWh. The emission intensity of the hydro, wind and nuclear power cycles is lower than that of solar power in 2011 as published by IPCC, and is discussed in an article on greenhouse gas emissions-the life cycle of energy sources. Similar to all energy sources is their total life cycle cycle mainly lies in the construction and transport phase, the transition to low-carbon power in the manufacture and transportation of solar devices will further reduce carbon emissions. BP Solar has two factories built by Solarex (one in Maryland, the other in Virginia) where all of the energy used to produce solar panels is produced by solar panels. The 1 kilowatt system eliminates the burning of about 170 pounds of coal, 300 pounds of carbon dioxide from being released into the atmosphere, and saves up to 105 gallons of water consumption each month.

The US National Renewable Energy Laboratory (NREL), in aligning different estimates of life-cycle greenhouse gas emissions for solar PV, found that the most important parameter is the solar site insolation: the GHG emission factor for solar PV inversely proportional to insolation. For sites with insolation of 1700 kWh/m2/year, typical of southern Europe, NREL researchers estimate greenhouse gas emissions of 45 gCO ₂ e/kWh. Using the same assumption, in Phoenix, USA, with insulation 2400 kWh/m2/year, the GHG emission factor will be reduced to 32 g CO ₂ e/kWh.

New Zealand's Parliamentary Commissioner for the Environment found that solar PV will have little impact on the country's greenhouse gas emissions. The country has generated 80 percent of its electricity from renewable resources (mainly hydroelectric and geothermal) and the peak of national electricity usage on winter evenings while the peak solar power plant in the summer afternoon, which means the large uptake of solar PV will end up replacing other renewable generators before the fossils. power plant.

Energy restore

The energy recovery time (EPBT) of the power generation system is the time it takes to generate as much energy as it consumes during the production and operation of the system's lifetime. Due to improved production technology, the payback time has dropped constantly since the introduction of PV systems in the energy market. In 2000, the PV system's energy recovery time is estimated to be 8 to 11 years and in 2006 it is estimated 1.5 to 3.5 years for crystalline silicon PV systems and 1-1.5 years for thin film technology (S. Europe). These numbers drop to 0.75-3.5 years in 2013, with an average of about 2 years for crystalline silicon PV and CIS systems.

Another economic measure, closely related to the time of energy return, is energy generated from the energy invested (EROEI) or energy return on investment (EROI), which is the ratio of the generated electricity divided by the energy needed to build and retain equipment. (This is not the same as the return on economic investment (ROI), which varies according to local energy prices, available subsidies and measurement techniques.) With the expected 30-year life, EROEI PV systems are in the 10 to 30 range, resulting in energy which is enough during their life to reproduce themselves repeatedly (6-31 reproductions) depending on the type of material, system balance (BOS), and the geographic location of the system.

Water usage

Solar power includes plants with the lowest water consumption per unit of electricity (photovoltaic), and also power plants with the highest water consumption (concentration of solar power with wet cooling system).

Photovoltaic power plants use very little water for operation. Life-cycle water consumption for utility-scale operations is estimated at 12 gallons per megawatt-hour for flat panel PV panel panels. Only wind power, which basically does not consume water during operation, has a lower water consumption intensity.

Concentrating on solar powered plants with wet cooling systems, on the other hand, has the highest water consumption intensity of any type of conventional power plant; only a fossil fuel plant with carbon capture and storage that has a higher water intensity. A 2013 study comparing various sources of electricity found that the average water consumption during solar power generation concentrates with wet cooling is 810 ga/MWhr for power towers and 890 gal/MWhr for troughs. This is higher than the operational water consumption (with cooling towers) for nuclear (720 gal/MWhr), coal (530 gal/MWhr), or natural gas (210). A 2011 study by the National Renewable Energy Laboratory reached the same conclusion: for power plants with cooling towers, water consumption during operation was 865 gal/MWhr for CSP troughs, 786 gal/MWhr for CSP towers, 687 gal/MWhr for coal, 672 gal/MWhr for nuclear, and 198 gal/MWhr for natural gas. The Solar Energy Industry Association noted that Nevada Solar One through the CSP plant consumes 850 gal/MWhr. The problem of water consumption is increased because CSP plants are often in dry environments where water is scarce.

In 2007, the US Congress directed the Department of Energy to report ways to reduce water consumption by CSP. The next report notes that dry cooling technology is available, although it is more expensive to build and operate, it can reduce water consumption by CSPs by 91 to 95 percent. The wet/dry hybrid cooling system can reduce water consumption by 32 to 58 percent. The 2015 report by NREL notes that of the 24 CSP power plants operating in the US, 4 uses a dry cooling system. Four dry cooling systems are three power plants at Ivanpah Solar Facilities near Barstow, California, and the Genesis Solar Energy Project in Riverside County, California. Of the 15 CSP projects under construction or development in the US in March 2015, 6 wet systems, 7 dry systems, 1 hybrid, and 1 are non-specific.

Although many older thermoelectric power plants with cooling or cooling through disposable ponds use more water than CSP, which means more water passes through their systems, most of the cooling water returns to available water bodies for other uses. , and they consume less water with evaporation. For example, a US coal-fired power station with disposable refrigeration uses 36,350 gal/MWhr, but only 250 gal/MWhr (less than one percent) is lost through evaporation. Since the 1970s, the majority of US power plants have been using recirculation systems such as cooling towers rather than a one-way system.

Other issues

One of the problems that often cause concern is the use of cadmium (Cd), a toxic heavy metal that has a tendency to accumulate in the ecological food chain. It is used as a semiconductor component in CdTe solar cells and as a buffer layer for certain CIGS cells in the form of CdS. The amount of cadmium used in thin film PV modules is relatively small (5-10 g/mÃ,²) and with proper emission recycling and control techniques in place of cadmium emissions from module production can be almost zero. Current PV technology causes cadmium emissions of 0.3-0.9 micrograms/kWh over the entire life cycle. Most of these emissions arise through the use of coal power for module manufacturing, and coal and lignite combustion leads to much higher cadmium emissions. The life cycle cadmium emissions from coal are 3.1 micrograms/kWh, 6.2 lignite, and 0.2 microgram/kWh of natural gas.

In life cycle analysis it has been noted, that if electricity generated by photovoltaic panels is used to make non-electric modules from coal combustion, the cadmium emissions from the use of coal power in the manufacturing process can be completely eliminated.

In the case of a crystalline silicon module, the soldering material, which joins with a string of copper cells, contains about 36 percent lead (Pb). In addition, the paste used for front and back contact printing contains Pb traces and sometimes Cd as well. It is estimated that about 1,000 metric tons of Pb have been used for 100 gigawatts of c-Si solar modules. However, there is no fundamental need for lead in solder alloys.

Some media sources have reported that concentrated solar power plants have injured or killed large numbers of birds due to intense heat from concentrated sunlight. This bad effect does not apply to solar PV power plants, and some claims may be overstated or exaggerated.

The published 2014 life cycle analysis for various power sources concludes that large-scale implementation of the sun and wind has the potential to reduce pollution-related environmental impacts. The study found that traces of land use, given in meters per year per megawatt-hour (m ² a/MWh), were lowest for wind, natural gas and PV roofs, with 0.26, 0, 49 and 0.59, respectively, and followed by utility-scale solar PV with 7.9. For CSPs, traces are 9 and 14, using parabolic troughs and sun towers, respectively. The biggest footprint has a coal-fired power plant with 18 m ² a/MWh.

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New technology

Concentrator Photovoltaics

The photovoltaic concentrator (CPV) system uses concentrated sunlight onto the photovoltaic surface for power production purposes. Contrary to conventional photovoltaic systems, these lenses use curved lenses and mirrors to focus sunlight onto highly efficient and multi-junction solar cells. Solar concentrators of all varieties can be used, and these are often mounted on solar trackers to keep the focal point on the cell as the sun moves across the sky. The glowing solar concentrator (when combined with PV-solar cells) can also be considered a CPV system. Concentrated photovoltaic is very useful because it can increase the efficiency of PV-solar panels drastically.

In addition, most solar panels on the spacecraft are also made of efficient multi-junction photovoltaic cells for obtaining electricity from sunlight while operating in the inner Solar System.

Floatovoltaics

Floatovoltaics is an emerging form of PV systems that float on the surface of irrigation canals, water reservoirs, quarry lakes, and tailings pools. Some systems exist in France, India, Japan, Korea, the United Kingdom and the United States. This system reduces the need for valuable land, conserves drinking water that should be lost through evaporation, and shows higher solar energy conversion efficiency, since the panels are kept at colder temperatures than on land. While not floating, other dual use facilities with solar power include fisheries.

src: www.theprepperjournal.com

See also

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References

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Source

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Further reading

Media related to solar power in Wikimedia Commons

• Smaller, cheaper, faster: Does Moore's law apply to solar cells ?, By Ramez Naam, March 16, 2011, American Scientific Analysis
• Herders Strap Solar Panels For Donkey To Utilize Solar Power To Start Manyattas (February 2015) on YouTube, K24 TV (Kenya)

Source of the article : Wikipedia