This document discusses solar energy and its potential applications. It notes that solar energy represents an opportunity but not a solution to energy problems on its own. Research and development is needed to overcome technical and cost barriers. Solar thermal and photovoltaic technologies can currently generate electricity in remote or peak load situations if market barriers are addressed. The National Energy Strategy supports R&D to develop more advanced solar products and programs to contribute solar electricity supply in 2000.
This document discusses solar energy for buildings and provides three key points:
1) It describes the benefits of solar energy for buildings including being free after initial costs, always available, clean energy and can be integrated into building design.
2) It explains the differences between passive, active and hybrid solar technologies and how they are used to collect, store and distribute solar energy.
3) It suggests ways to incorporate solar design into multi-unit residential buildings through considerations like orientation, fenestration, thermal mass and shading devices. Readers will understand opportunities for solar building design.
This document provides an overview of solar energy, including its history, current uses, and future potential. It discusses how solar energy is a renewable resource that can be converted to electricity or heat. The document outlines the development of solar technologies from the Greeks and Romans to modern photovoltaic cells. Examples are given of solar energy uses in Kenya and for electricity generation, heating, and transportation. The environmental benefits and potential impacts of solar power are also summarized. The future of solar is said to be bright with opportunities like solar plants in space and more efficient photovoltaic cells.
This document discusses various renewable and alternative energy sources including wind energy, biofuels, solar thermal energy, hydraulic energy, wave energy, and blue energy. Renewable energy can replace conventional fuels for electricity generation, heating, transportation fuels, and off-grid energy services. Examples of renewable energy sources mentioned are solar, wind, geothermal, hydro, tidal, and biomass. Alternative energies are those that can replace current energy sources while having lower pollution impacts or being renewable. The environmental impacts of these renewable energies include reducing reliance on fossil fuels and their pollution, being inexhaustible resources, generating jobs, and reducing dependence on foreign energy imports.
This document discusses framing renewable energy technologies like solar panels and wind turbines within the paradigm of "solar power agriculture". It argues that these technologies are similar to traditional agriculture in that they both collect solar energy over large areas to facilitate energy conversion. Like agriculture, renewable energy production has an S-shaped growth curve rather than a bell curve. The document examines whether renewable technologies can meet humanity's energy needs without competing for agricultural land and whether the concept of solar power agriculture could help increase public acceptance and investment in renewables.
Solar energy originates from the thermonuclear fusion reactions of the sun. It represents the entire electromagnetic spectrum that reaches the Earth. Some key advantages of solar energy are that it produces no pollutants, and the energy reaching the Earth each day is greater than all the fossil fuels on the planet. However, solar energy is intermittent and diffuse, requiring technologies to concentrate and store it. Various technologies can harness solar energy for heating water and living spaces, as well as generating electricity through solar thermal power towers and dishes/troughs that focus sunlight. Overall, solar energy represents an enormous renewable resource that can significantly reduce dependence on fossil fuels.
This document discusses solar power and its various technologies including photovoltaics and concentrating solar power. It provides details on solar thermal energy applications like water heating, heating/cooling buildings, and cooking. Concentrated solar power plants using molten salt for thermal energy storage are also described. The document then discusses solar energy development and challenges in Bangladesh, noting most solar panels there have low efficiency and the government's renewable energy targets are modest compared to other countries.
Solar energy : The Ultimate Renewable ResourceRounak Kapoor
This is presentation on Solar Energy.
It contains->
> Whst is solar energy?
> Its advantages and disadvantages.
> Its Applications.
> Power Towers.
> Solar Panels.
This Presentation is very usefull for Engineering Students.
Geothermal power generates electricity by harnessing heat from within the Earth. It is considered a renewable resource, though specific locations can eventually be depleted as the ground cools over many decades. Three main types of geothermal power plants exist - dry steam, flash, and binary cycle plants. The largest geothermal facility in the world is The Geysers in California, while other significant sites include those in Nevada, Indonesia, and Kenya. Geothermal energy also shows promise for desalination and heating applications.
This document discusses solar energy for buildings and provides three key points:
1) It describes the benefits of solar energy for buildings including being free after initial costs, always available, clean energy and can be integrated into building design.
2) It explains the differences between passive, active and hybrid solar technologies and how they are used to collect, store and distribute solar energy.
3) It suggests ways to incorporate solar design into multi-unit residential buildings through considerations like orientation, fenestration, thermal mass and shading devices. Readers will understand opportunities for solar building design.
This document provides an overview of solar energy, including its history, current uses, and future potential. It discusses how solar energy is a renewable resource that can be converted to electricity or heat. The document outlines the development of solar technologies from the Greeks and Romans to modern photovoltaic cells. Examples are given of solar energy uses in Kenya and for electricity generation, heating, and transportation. The environmental benefits and potential impacts of solar power are also summarized. The future of solar is said to be bright with opportunities like solar plants in space and more efficient photovoltaic cells.
This document discusses various renewable and alternative energy sources including wind energy, biofuels, solar thermal energy, hydraulic energy, wave energy, and blue energy. Renewable energy can replace conventional fuels for electricity generation, heating, transportation fuels, and off-grid energy services. Examples of renewable energy sources mentioned are solar, wind, geothermal, hydro, tidal, and biomass. Alternative energies are those that can replace current energy sources while having lower pollution impacts or being renewable. The environmental impacts of these renewable energies include reducing reliance on fossil fuels and their pollution, being inexhaustible resources, generating jobs, and reducing dependence on foreign energy imports.
This document discusses framing renewable energy technologies like solar panels and wind turbines within the paradigm of "solar power agriculture". It argues that these technologies are similar to traditional agriculture in that they both collect solar energy over large areas to facilitate energy conversion. Like agriculture, renewable energy production has an S-shaped growth curve rather than a bell curve. The document examines whether renewable technologies can meet humanity's energy needs without competing for agricultural land and whether the concept of solar power agriculture could help increase public acceptance and investment in renewables.
Solar energy originates from the thermonuclear fusion reactions of the sun. It represents the entire electromagnetic spectrum that reaches the Earth. Some key advantages of solar energy are that it produces no pollutants, and the energy reaching the Earth each day is greater than all the fossil fuels on the planet. However, solar energy is intermittent and diffuse, requiring technologies to concentrate and store it. Various technologies can harness solar energy for heating water and living spaces, as well as generating electricity through solar thermal power towers and dishes/troughs that focus sunlight. Overall, solar energy represents an enormous renewable resource that can significantly reduce dependence on fossil fuels.
This document discusses solar power and its various technologies including photovoltaics and concentrating solar power. It provides details on solar thermal energy applications like water heating, heating/cooling buildings, and cooking. Concentrated solar power plants using molten salt for thermal energy storage are also described. The document then discusses solar energy development and challenges in Bangladesh, noting most solar panels there have low efficiency and the government's renewable energy targets are modest compared to other countries.
Solar energy : The Ultimate Renewable ResourceRounak Kapoor
This is presentation on Solar Energy.
It contains->
> Whst is solar energy?
> Its advantages and disadvantages.
> Its Applications.
> Power Towers.
> Solar Panels.
This Presentation is very usefull for Engineering Students.
Geothermal power generates electricity by harnessing heat from within the Earth. It is considered a renewable resource, though specific locations can eventually be depleted as the ground cools over many decades. Three main types of geothermal power plants exist - dry steam, flash, and binary cycle plants. The largest geothermal facility in the world is The Geysers in California, while other significant sites include those in Nevada, Indonesia, and Kenya. Geothermal energy also shows promise for desalination and heating applications.
Pilot Solar Thermal Power Plant Station in Southwest LouisianaIJAPEJOURNAL
Solar thermal plants are basically power plants that generate electricity from high-temperature heat. The difference between them and conventional power plants is that instead of deriving energy from gas, coal or oil, the sun provides the energy that drives the turbines. In this paper we will give a brief demonstration of solar thermal power and different system designs of solar thermal power plants. Then we will see the feasibility of implementing solar power plants in Louisiana which currently depends mostly on its conventional power plants which use traditional fuels such as gas, oil, and coal. This study was a part of a proposal that was funded by the US the Department of Energy to construct solar thermal plant near Lafayette, Louisiana. The power plant is currently under the construction and it will be completed by Summer of 2013
This document discusses various methods of harnessing solar energy, including power towers, parabolic dishes and troughs, photovoltaic cells, and passive solar heating. Power towers use an array of mirrors to reflect sunlight to a central receiver tower to achieve high temperatures for generating electricity. Parabolic dishes and troughs focus sunlight onto receivers to heat liquid and drive steam turbines. Photovoltaic cells directly convert sunlight to electricity through silicon photovoltaic effect. Passive solar designs utilize thermal mass and south-facing windows to naturally heat buildings. The document analyzes advantages and challenges of different solar technologies.
The document discusses solar power as a renewable energy source. It notes that fossil fuel reserves are dwindling and will be depleted within 120-150 years. Solar energy has significant potential as a power source given the abundant solar radiation received by the Earth each day. The document outlines average solar insolation levels globally, the efficiency and lifespan of solar panels, and recent advances in solar technology. It concludes that accelerating the use of solar power generation is important given the looming energy crisis posed by finite fossil fuel reserves.
The presentation is about the renewable sources of energy and its present scenario of year 2010. It majorly talks about the generation and utilization of energy through renewable sources.
The document discusses various ways that solar energy is harnessed and used. About half of the solar energy that reaches Earth's upper atmosphere reaches the surface, where it warms the land, oceans and atmosphere. Photosynthesis captures solar energy in plants, and solar energy can also be harnessed to provide lighting, heating, cooling, electricity, and for industrial processes like cooking and water treatment. The total solar energy absorbed by Earth is approximately 3,850,000 exajoules per year, vastly more than the world's total annual energy use.
This document discusses different forms of energy and solar energy specifically. It covers:
1) The different forms of energy including kinetic, heat, chemical, electrical, sound, and nuclear energy. Energy can change forms but cannot be created or destroyed.
2) How solar energy works, from the photons emitted by the sun being absorbed by solar cells to generate electricity via the photoelectric effect.
3) The two main uses of solar energy - generating electricity using photovoltaic panels and getting heat from the sun for applications like drying crops. Solar energy is a renewable resource but production stops at night.
Solar energy can be harnessed in three main ways: through solar thermal technologies to convert sunlight into heat, through photovoltaics to directly convert it into electricity, and through photosynthesis to convert it into chemical energy. Some key applications of solar energy include water heating, space heating, electricity generation, and driving chemical reactions. While solar energy is abundant and clean, it also has disadvantages like intermittency and the need to convert and store it before use.
The document discusses various alternative energy sources including renewable sources like solar, wind, hydropower, and biomass as well as non-renewable sources like fossil fuels and nuclear energy. It provides details on different solar energy technologies like solar thermal, photovoltaic, and passive solar. Hydropower harnesses the kinetic energy of moving water through various methods like dams, run-of-river systems, tidal power, and wave power. While fossil fuels and nuclear energy are easier to use, renewable sources are more environmentally friendly and sustainable long-term options.
Alternative energy sources presentationShahan Saheed
The document discusses various alternative energy sources as replacements for fossil fuels to mitigate global warming. It describes solar power including the photovoltaic process to convert sunlight to electricity and thermal solar to heat water. Challenges with solar include high costs and lack of energy at night. The document also covers thermal power stations in Sri Lanka and companies involved in alternative energy implementation. Wind power is discussed as an option for rural communities through micro-grids.
The document discusses various renewable energy sources including wind, solar, geothermal, hydro, and hydrogen. It provides details on how each source works, current usage levels, benefits and downsides. For wind energy, it describes how turbines convert wind into electricity. Geothermal taps heat from the earth. Hydrogen can be used to store energy from renewable sources using electrolysis and fuel cells. The document also explores using algae as a potential source of hydrogen fuel.
The document evaluates the potential of a solar chimney power plant in the semi-arid region of Nigeria. A mathematical model was used to estimate the amount of power generated from a solar chimney power plant with a collector diameter of 700 m and chimney height of 700 m, which could produce up to 3000 MW of electricity. Solar chimney power plants utilize solar radiation to heat air which drives turbines to generate electricity. They have potential for renewable energy production in areas with abundant sun and flat land.
This document introduces a GIS suitability model created by Geenex, a German company implementing solar farms in the southeastern US, to identify suitable parcels of land for constructing mid-sized solar farms in North and South Carolina. The model considers parcel size, distance to power stations and lines, and elevation variance, using a pass-fail approach. When demonstrated in Lancaster County, SC, the model identified 13 suitable parcels. The model could be improved by adding ranking criteria as some factors are difficult to model.
The document proposes using the moon as a base for a large-scale solar power satellite system to address global problems like global warming, high energy demand, and national debts. It would involve constructing huge solar collectors on the lunar equator using materials from the lunar surface. The collectors would concentrate solar energy and use Stirling engines to generate electricity, which would then be transmitted to receiving stations on Earth via microwave beams. A system of this scale could generate over 5 trillion kilowatt-hours per year and produce hundreds of billions of dollars in revenue to help address various national and global issues. Key advantages include its clean energy generation without needing scientific breakthroughs.
The paper mentions the major issues related to the residential solar energy and the commercial solar energy. Covering the types and application of both residential and commercial, cost related issues, and the future of the industry.
The document examines the changing importance of alternative energy sources. It discusses various renewable energy sources including biogas, biomass, wind, tidal, wave, geothermal, hydroelectric, and solar energy. It provides information on the global patterns and potential of these different energy sources. For example, it notes that areas above 23.5 degrees north generally have higher wind speeds making them suitable locations for wind farms. It also gives statistics on Spain's use of wind power, noting that currently 15% of the country's power is from wind energy.
Renewable energy & its furure prospects in indiaSurabhi Pal
India's renewable energy sector has grown significantly in recent decades. Renewable energy currently accounts for 9% of India's total installed power capacity and 3% of electricity generation. However, demand for energy is projected to substantially increase by 2020-21. To meet this demand, India has set targets to deploy various renewable technologies like solar, wind, biomass and small hydro. Realizing its renewable energy potential could help India reduce its reliance on fossil fuels and create rural employment opportunities.
The presentation discusses alternative energy sources including nuclear energy, natural gas, solar power, wind power, and biomass. It outlines some key advantages and disadvantages of each source. Nuclear energy provides low-carbon power but poses safety risks from accidents. Natural gas is a fossil fuel that produces greenhouse gases. Solar and wind power are renewable sources but their availability depends on sunlight and wind. Biomass can reduce landfills but requires fuel and land. The presentation suggests that wind power is among the cleanest options as it does not contribute to global warming.
Solar Power Plants Photovoltaic vs ThermalThomas Smith
The document compares and contrasts two types of large-scale solar power plants: the Agua Caliente photovoltaic plant and the Ivanpah solar thermal plant. It outlines key details about each plant such as their location, size, cost, environmental impacts, lifetime, and purchasers of the generated power. While both require large amounts of land and have high build and maintenance costs, the document recommends thermal solar due to its longer lifetime and ability to provide backup power and cogeneration capabilities.
A solar inverter converts the variable direct current (DC) output of solar panels into alternating current (AC) that can power homes or be fed into the electric grid. It is a critical component that allows solar power to be used with standard appliances. This document discusses the operation of solar inverters and solar panels, which use the photovoltaic effect to generate electricity from sunlight and maximize power output through techniques like maximum power point tracking. It also provides an overview of renewable energy sources like wind, hydro, and solar power and their increasing role in energy supply.
Solar energy is radiant light and heat from the Sun that is harnessed through technologies like solar heating, photovoltaics, and solar thermal energy. It is captured through either passive solar techniques that don't use mechanical and electrical devices, like building orientation, or active solar techniques like photovoltaic panels and concentrated solar power plants. The Earth receives a vast amount of solar energy each year, far exceeding current and projected human and industrial energy consumption. Solar energy resources and technologies have developed significantly since the late 19th century but saw renewed attention and improved economics following the oil crises of the 1970s.
Solar energy is a renewable resource that comes from the sun. It can be used to generate electricity through methods like photovoltaics or concentrated solar power, or to heat and cool buildings. While solar energy has many benefits, its widespread adoption faces challenges related to intermittent availability, storage, and the large land and material resources required. Future prospects include new concentrating and luminescent solar technologies as well as potentially placing solar arrays in space to collect energy unaffected by Earth's conditions.
L1 Solar Energy--The Ultimate Renewable Resource.pptnehasolanki83
Solar energy originates from the sun and represents the entire electromagnetic spectrum that reaches Earth. It has the advantages of being pollution-free and sustainable, with the energy from 30 days of sunshine having the equivalent energy of all fossil fuels used and unused on Earth. Challenges include its diffuse and intermittent nature. Various technologies have been developed to collect, convert, and store solar energy for heating water and living spaces as well as generating electricity through photovoltaics and concentrating solar power towers and dishes. While solar technologies are improving, their higher initial costs compared to fossil fuels have limited widespread adoption.
Pilot Solar Thermal Power Plant Station in Southwest LouisianaIJAPEJOURNAL
Solar thermal plants are basically power plants that generate electricity from high-temperature heat. The difference between them and conventional power plants is that instead of deriving energy from gas, coal or oil, the sun provides the energy that drives the turbines. In this paper we will give a brief demonstration of solar thermal power and different system designs of solar thermal power plants. Then we will see the feasibility of implementing solar power plants in Louisiana which currently depends mostly on its conventional power plants which use traditional fuels such as gas, oil, and coal. This study was a part of a proposal that was funded by the US the Department of Energy to construct solar thermal plant near Lafayette, Louisiana. The power plant is currently under the construction and it will be completed by Summer of 2013
This document discusses various methods of harnessing solar energy, including power towers, parabolic dishes and troughs, photovoltaic cells, and passive solar heating. Power towers use an array of mirrors to reflect sunlight to a central receiver tower to achieve high temperatures for generating electricity. Parabolic dishes and troughs focus sunlight onto receivers to heat liquid and drive steam turbines. Photovoltaic cells directly convert sunlight to electricity through silicon photovoltaic effect. Passive solar designs utilize thermal mass and south-facing windows to naturally heat buildings. The document analyzes advantages and challenges of different solar technologies.
The document discusses solar power as a renewable energy source. It notes that fossil fuel reserves are dwindling and will be depleted within 120-150 years. Solar energy has significant potential as a power source given the abundant solar radiation received by the Earth each day. The document outlines average solar insolation levels globally, the efficiency and lifespan of solar panels, and recent advances in solar technology. It concludes that accelerating the use of solar power generation is important given the looming energy crisis posed by finite fossil fuel reserves.
The presentation is about the renewable sources of energy and its present scenario of year 2010. It majorly talks about the generation and utilization of energy through renewable sources.
The document discusses various ways that solar energy is harnessed and used. About half of the solar energy that reaches Earth's upper atmosphere reaches the surface, where it warms the land, oceans and atmosphere. Photosynthesis captures solar energy in plants, and solar energy can also be harnessed to provide lighting, heating, cooling, electricity, and for industrial processes like cooking and water treatment. The total solar energy absorbed by Earth is approximately 3,850,000 exajoules per year, vastly more than the world's total annual energy use.
This document discusses different forms of energy and solar energy specifically. It covers:
1) The different forms of energy including kinetic, heat, chemical, electrical, sound, and nuclear energy. Energy can change forms but cannot be created or destroyed.
2) How solar energy works, from the photons emitted by the sun being absorbed by solar cells to generate electricity via the photoelectric effect.
3) The two main uses of solar energy - generating electricity using photovoltaic panels and getting heat from the sun for applications like drying crops. Solar energy is a renewable resource but production stops at night.
Solar energy can be harnessed in three main ways: through solar thermal technologies to convert sunlight into heat, through photovoltaics to directly convert it into electricity, and through photosynthesis to convert it into chemical energy. Some key applications of solar energy include water heating, space heating, electricity generation, and driving chemical reactions. While solar energy is abundant and clean, it also has disadvantages like intermittency and the need to convert and store it before use.
The document discusses various alternative energy sources including renewable sources like solar, wind, hydropower, and biomass as well as non-renewable sources like fossil fuels and nuclear energy. It provides details on different solar energy technologies like solar thermal, photovoltaic, and passive solar. Hydropower harnesses the kinetic energy of moving water through various methods like dams, run-of-river systems, tidal power, and wave power. While fossil fuels and nuclear energy are easier to use, renewable sources are more environmentally friendly and sustainable long-term options.
Alternative energy sources presentationShahan Saheed
The document discusses various alternative energy sources as replacements for fossil fuels to mitigate global warming. It describes solar power including the photovoltaic process to convert sunlight to electricity and thermal solar to heat water. Challenges with solar include high costs and lack of energy at night. The document also covers thermal power stations in Sri Lanka and companies involved in alternative energy implementation. Wind power is discussed as an option for rural communities through micro-grids.
The document discusses various renewable energy sources including wind, solar, geothermal, hydro, and hydrogen. It provides details on how each source works, current usage levels, benefits and downsides. For wind energy, it describes how turbines convert wind into electricity. Geothermal taps heat from the earth. Hydrogen can be used to store energy from renewable sources using electrolysis and fuel cells. The document also explores using algae as a potential source of hydrogen fuel.
The document evaluates the potential of a solar chimney power plant in the semi-arid region of Nigeria. A mathematical model was used to estimate the amount of power generated from a solar chimney power plant with a collector diameter of 700 m and chimney height of 700 m, which could produce up to 3000 MW of electricity. Solar chimney power plants utilize solar radiation to heat air which drives turbines to generate electricity. They have potential for renewable energy production in areas with abundant sun and flat land.
This document introduces a GIS suitability model created by Geenex, a German company implementing solar farms in the southeastern US, to identify suitable parcels of land for constructing mid-sized solar farms in North and South Carolina. The model considers parcel size, distance to power stations and lines, and elevation variance, using a pass-fail approach. When demonstrated in Lancaster County, SC, the model identified 13 suitable parcels. The model could be improved by adding ranking criteria as some factors are difficult to model.
The document proposes using the moon as a base for a large-scale solar power satellite system to address global problems like global warming, high energy demand, and national debts. It would involve constructing huge solar collectors on the lunar equator using materials from the lunar surface. The collectors would concentrate solar energy and use Stirling engines to generate electricity, which would then be transmitted to receiving stations on Earth via microwave beams. A system of this scale could generate over 5 trillion kilowatt-hours per year and produce hundreds of billions of dollars in revenue to help address various national and global issues. Key advantages include its clean energy generation without needing scientific breakthroughs.
The paper mentions the major issues related to the residential solar energy and the commercial solar energy. Covering the types and application of both residential and commercial, cost related issues, and the future of the industry.
The document examines the changing importance of alternative energy sources. It discusses various renewable energy sources including biogas, biomass, wind, tidal, wave, geothermal, hydroelectric, and solar energy. It provides information on the global patterns and potential of these different energy sources. For example, it notes that areas above 23.5 degrees north generally have higher wind speeds making them suitable locations for wind farms. It also gives statistics on Spain's use of wind power, noting that currently 15% of the country's power is from wind energy.
Renewable energy & its furure prospects in indiaSurabhi Pal
India's renewable energy sector has grown significantly in recent decades. Renewable energy currently accounts for 9% of India's total installed power capacity and 3% of electricity generation. However, demand for energy is projected to substantially increase by 2020-21. To meet this demand, India has set targets to deploy various renewable technologies like solar, wind, biomass and small hydro. Realizing its renewable energy potential could help India reduce its reliance on fossil fuels and create rural employment opportunities.
The presentation discusses alternative energy sources including nuclear energy, natural gas, solar power, wind power, and biomass. It outlines some key advantages and disadvantages of each source. Nuclear energy provides low-carbon power but poses safety risks from accidents. Natural gas is a fossil fuel that produces greenhouse gases. Solar and wind power are renewable sources but their availability depends on sunlight and wind. Biomass can reduce landfills but requires fuel and land. The presentation suggests that wind power is among the cleanest options as it does not contribute to global warming.
Solar Power Plants Photovoltaic vs ThermalThomas Smith
The document compares and contrasts two types of large-scale solar power plants: the Agua Caliente photovoltaic plant and the Ivanpah solar thermal plant. It outlines key details about each plant such as their location, size, cost, environmental impacts, lifetime, and purchasers of the generated power. While both require large amounts of land and have high build and maintenance costs, the document recommends thermal solar due to its longer lifetime and ability to provide backup power and cogeneration capabilities.
A solar inverter converts the variable direct current (DC) output of solar panels into alternating current (AC) that can power homes or be fed into the electric grid. It is a critical component that allows solar power to be used with standard appliances. This document discusses the operation of solar inverters and solar panels, which use the photovoltaic effect to generate electricity from sunlight and maximize power output through techniques like maximum power point tracking. It also provides an overview of renewable energy sources like wind, hydro, and solar power and their increasing role in energy supply.
Solar energy is radiant light and heat from the Sun that is harnessed through technologies like solar heating, photovoltaics, and solar thermal energy. It is captured through either passive solar techniques that don't use mechanical and electrical devices, like building orientation, or active solar techniques like photovoltaic panels and concentrated solar power plants. The Earth receives a vast amount of solar energy each year, far exceeding current and projected human and industrial energy consumption. Solar energy resources and technologies have developed significantly since the late 19th century but saw renewed attention and improved economics following the oil crises of the 1970s.
Solar energy is a renewable resource that comes from the sun. It can be used to generate electricity through methods like photovoltaics or concentrated solar power, or to heat and cool buildings. While solar energy has many benefits, its widespread adoption faces challenges related to intermittent availability, storage, and the large land and material resources required. Future prospects include new concentrating and luminescent solar technologies as well as potentially placing solar arrays in space to collect energy unaffected by Earth's conditions.
L1 Solar Energy--The Ultimate Renewable Resource.pptnehasolanki83
Solar energy originates from the sun and represents the entire electromagnetic spectrum that reaches Earth. It has the advantages of being pollution-free and sustainable, with the energy from 30 days of sunshine having the equivalent energy of all fossil fuels used and unused on Earth. Challenges include its diffuse and intermittent nature. Various technologies have been developed to collect, convert, and store solar energy for heating water and living spaces as well as generating electricity through photovoltaics and concentrating solar power towers and dishes. While solar technologies are improving, their higher initial costs compared to fossil fuels have limited widespread adoption.
Solar to energy presentation geofrey yatorGeofrey Yator
Solar to energy conversion.The definition,need for,technologies and the Future of solar energy in the planet earth.
The article is presented by Geofrey Kibiwott yator University of Eldoret.
The document discusses solar energy, including its origins from the sun, applications in generating electricity, and various manufacturing methods like photovoltaic cells, solar heating, and solar power towers. It covers the advantages of being renewable and occupying less space than alternatives while also addressing the disadvantages of higher initial costs and the intermittent nature of the solar resource.
The document discusses various methods for harnessing solar energy, including passive and active solar heating systems for water and living spaces, as well as solar thermal and photovoltaic electricity generation. It describes technologies like power towers, parabolic dishes and troughs, and solar panels. While solar energy has benefits like being renewable and pollution-free, its intermittent nature and higher costs compared to fossil fuels have posed challenges to widespread adoption.
Solar energy originates from thermonuclear fusion reactions in the sun. It represents the entire electromagnetic spectrum reaching Earth. While solar energy is abundant and pollution-free, it is also intermittent and diffuse. Various technologies have been developed to harness solar energy for heating water and living spaces as well as generating electricity. These technologies include passive and active solar water heating, solar thermal power towers and dishes, and photovoltaic cells that directly convert sunlight to electricity. Further advances aim to improve efficiency and reduce costs to make greater use of solar energy.
solar energy--the ultimate renewable resourceGhassan Hadi
Solar energy originates from the thermonuclear fusion reactions of the sun. It represents the entire electromagnetic spectrum that reaches Earth. While solar energy has the advantages of being pollution-free and sustainable, its disadvantages include inconsistent sunshine and its diffuse nature, requiring concentration. Several methods are discussed for harnessing solar energy, including using flat plate collectors to heat water passively or with pumps in an active system. Solar energy can also be used to directly heat buildings through designs incorporating insulation, collection, and thermal mass storage. Additional methods discussed are using power towers or parabolic dishes/troughs to generate solar-thermal electricity, as well as using photovoltaic cells for direct conversion to electricity, though their efficiency and costs remain
The document discusses various methods for harnessing solar energy, including passive solar heating of buildings, active solar water heating systems, solar power towers, parabolic dishes and troughs, and photovoltaic cells. It notes that while solar energy technologies are improving in efficiency and lowering in cost, they remain more expensive than fossil fuel-based energy production. However, solar power represents a renewable and pollution-free alternative to reducing dependence on coal and nuclear energy.
This document provides an overview of solar energy, including definitions of renewable energy and the types of renewable energy. It discusses findings from REN21's 2016 report on global renewable energy usage. Solar energy harnesses radiant light and heat from the sun using technologies like solar heating, photovoltaics, solar thermal energy, and artificial photosynthesis. The advantages of solar energy are that it is non-polluting, inexhaustible, and helps reduce CO2 emissions. Common solar energy applications include photovoltaics, solar water heating, solar thermal power plants, and solar cooling/ventilation. The document also discusses factors that restrict the usage of solar energy such as its low energy density and unstable supply dependent on location and
This document provides an introduction and overview of solar energy and solar power sprayers. It discusses the need for non-conventional energy sources given depleting fossil fuel reserves. Solar energy can be captured directly through solar photovoltaic cells or indirectly through processes like wind and hydroelectric power. A solar power sprayer uses photovoltaic panels to charge a battery and power an electric motor that rotates the sprayer pump, avoiding the need for gasoline. The document outlines the construction, components, design considerations, advantages and applications of solar power sprayers.
Renewable Energy comes from sources that do not deplete over years such as sun, wind, oceans and plants. There are numerous ways to convert primary energy forms into consumable forms of energy including heat and electricity; however, due to the intermittent nature of many renewable sources, the issue of storing electricity is of particular importance. Further its worth to note renewable energy technologies do NOT necessarily compete with each other purely based on price. It depends on geographic location, availability of space, capital costs, operational costs, and environmental concerns.
This document provides a personal testimony from Sébastien about their experience using the "restraint, efficiency, renewable energy" guide from Solar Generation to make their university campus more sustainable. They found the approach clear and logical. First, they reduced energy consumption through education. Then, an energy audit identified efficiency improvements. While restraint and efficiency were easier, renewable projects require more investment but are still worthwhile. Sébastien recommends taking a holistic approach and utilizing Solar Generation's resources.
This document provides an introduction to solar energy, including its basic principles and uses. It discusses how solar energy works, the components of a solar energy system (collectors and storage), and current applications such as heating, cooling, transportation, and electricity generation. Solar energy can be used directly for heating applications and converted to electricity via photovoltaic cells. Inverters are required to convert the DC electricity from solar panels to the AC electricity used in homes and buildings. There are different types of solar inverters depending on the application. The document also discusses solar energy as a renewable alternative to fossil fuels that does not pollute and can help reduce greenhouse gas emissions.
The document discusses the massive potential for renewable energy sources on Earth, including wind, solar, hydroelectric, geothermal, and ocean power. The theoretical potential exceeds 4 million terawatts, while the technical potential is around 240 terawatts, over 10 times current worldwide energy consumption annually. Some key renewable energy sources are then discussed in more detail, along with their geographical potential and some considerations regarding their deployment.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Solar energy -the ultimate renewable resourcerahuldawar
Solar energy originates from the sun's thermonuclear fusion reactions. It represents the entire electromagnetic spectrum that reaches Earth, including visible light, infrared, ultraviolet, x-rays, and radio waves. Solar energy has the advantages of being pollution-free and sustainable, but it is also diffuse and inconsistent, requiring technologies to concentrate and store it. Common solar technologies include heating water and buildings, generating electricity via solar panels, power towers, and parabolic dishes/troughs. While solar is currently more expensive than fossil fuels, its costs are decreasing as technologies advance.
This document proposes using the moon as a base for a solar power satellite system to address global problems like global warming, the US national debt, and high taxes. It describes how a lunar-based solar thermal electricity system could generate over 5 trillion kilowatt-hours per year of clean energy by placing solar collectors and Stirling engines along the lunar equator. This would significantly reduce worldwide greenhouse gas emissions and fossil fuel dependence. Tables evaluate technical advantages over traditional geosynchronous solar satellites, such as having unlimited expansion space and access to raw materials on the moon. The system aims to power the world through microwave beams to rectifying antennas at multiple sites on Earth.
This document provides an overview of solar energy, including its history, current applications, and future potential. It discusses how solar energy works and the two key components (collectors and storage). Applications mentioned include solar thermal technologies for water and space heating, electricity production, cooking, process heat, and desalination. The document also reviews various energy storage methods and the development, deployment, and economics of solar power over history.
Global Situational Awareness of A.I. and where its headedvikram sood
You can see the future first in San Francisco.
Over the past year, the talk of the town has shifted from $10 billion compute clusters to $100 billion clusters to trillion-dollar clusters. Every six months another zero is added to the boardroom plans. Behind the scenes, there’s a fierce scramble to secure every power contract still available for the rest of the decade, every voltage transformer that can possibly be procured. American big business is gearing up to pour trillions of dollars into a long-unseen mobilization of American industrial might. By the end of the decade, American electricity production will have grown tens of percent; from the shale fields of Pennsylvania to the solar farms of Nevada, hundreds of millions of GPUs will hum.
The AGI race has begun. We are building machines that can think and reason. By 2025/26, these machines will outpace college graduates. By the end of the decade, they will be smarter than you or I; we will have superintelligence, in the true sense of the word. Along the way, national security forces not seen in half a century will be un-leashed, and before long, The Project will be on. If we’re lucky, we’ll be in an all-out race with the CCP; if we’re unlucky, an all-out war.
Everyone is now talking about AI, but few have the faintest glimmer of what is about to hit them. Nvidia analysts still think 2024 might be close to the peak. Mainstream pundits are stuck on the wilful blindness of “it’s just predicting the next word”. They see only hype and business-as-usual; at most they entertain another internet-scale technological change.
Before long, the world will wake up. But right now, there are perhaps a few hundred people, most of them in San Francisco and the AI labs, that have situational awareness. Through whatever peculiar forces of fate, I have found myself amongst them. A few years ago, these people were derided as crazy—but they trusted the trendlines, which allowed them to correctly predict the AI advances of the past few years. Whether these people are also right about the next few years remains to be seen. But these are very smart people—the smartest people I have ever met—and they are the ones building this technology. Perhaps they will be an odd footnote in history, or perhaps they will go down in history like Szilard and Oppenheimer and Teller. If they are seeing the future even close to correctly, we are in for a wild ride.
Let me tell you what we see.
The Ipsos - AI - Monitor 2024 Report.pdfSocial Samosa
According to Ipsos AI Monitor's 2024 report, 65% Indians said that products and services using AI have profoundly changed their daily life in the past 3-5 years.
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Dynamic policy enforcement is becoming an increasingly important topic in today’s world where data privacy and compliance is a top priority for companies, individuals, and regulators alike. In these slides, we discuss how LinkedIn implements a powerful dynamic policy enforcement engine, called ViewShift, and integrates it within its data lake. We show the query engine architecture and how catalog implementations can automatically route table resolutions to compliance-enforcing SQL views. Such views have a set of very interesting properties: (1) They are auto-generated from declarative data annotations. (2) They respect user-level consent and preferences (3) They are context-aware, encoding a different set of transformations for different use cases (4) They are portable; while the SQL logic is only implemented in one SQL dialect, it is accessible in all engines.
#SQL #Views #Privacy #Compliance #DataLake
Predictably Improve Your B2B Tech Company's Performance by Leveraging DataKiwi Creative
Harness the power of AI-backed reports, benchmarking and data analysis to predict trends and detect anomalies in your marketing efforts.
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From metrics to track to data habits to pick up, enhance your reporting for powerful insights to improve your B2B tech company's marketing.
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This is the webinar recording from the June 2024 HubSpot User Group (HUG) for B2B Technology USA.
Watch the video recording at https://youtu.be/5vjwGfPN9lw
Sign up for future HUG events at https://events.hubspot.com/b2b-technology-usa/
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Foundations of SQL: Understand the basics of SQL, including data retrieval, filtering, and aggregation.
Advanced Queries: Learn to craft complex queries to uncover deep insights from your data.
Data Trends and Patterns: Discover how to identify and interpret trends and patterns in your datasets.
Practical Examples: Follow step-by-step examples to apply SQL techniques in real-world scenarios.
Actionable Insights: Gain the skills to derive actionable insights that drive informed decision-making.
Join us on this journey to enhance your data analysis capabilities and unlock the full potential of SQL. Perfect for data enthusiasts, analysts, and anyone eager to harness the power of data!
#DataAnalysis #SQL #LearningSQL #DataInsights #DataScience #Analytics
End-to-end pipeline agility - Berlin Buzzwords 2024Lars Albertsson
We describe how we achieve high change agility in data engineering by eliminating the fear of breaking downstream data pipelines through end-to-end pipeline testing, and by using schema metaprogramming to safely eliminate boilerplate involved in changes that affect whole pipelines.
A quick poll on agility in changing pipelines from end to end indicated a huge span in capabilities. For the question "How long time does it take for all downstream pipelines to be adapted to an upstream change," the median response was 6 months, but some respondents could do it in less than a day. When quantitative data engineering differences between the best and worst are measured, the span is often 100x-1000x, sometimes even more.
A long time ago, we suffered at Spotify from fear of changing pipelines due to not knowing what the impact might be downstream. We made plans for a technical solution to test pipelines end-to-end to mitigate that fear, but the effort failed for cultural reasons. We eventually solved this challenge, but in a different context. In this presentation we will describe how we test full pipelines effectively by manipulating workflow orchestration, which enables us to make changes in pipelines without fear of breaking downstream.
Making schema changes that affect many jobs also involves a lot of toil and boilerplate. Using schema-on-read mitigates some of it, but has drawbacks since it makes it more difficult to detect errors early. We will describe how we have rejected this tradeoff by applying schema metaprogramming, eliminating boilerplate but keeping the protection of static typing, thereby further improving agility to quickly modify data pipelines without fear.
1. Chapter 17
SOLAR ENERGY
Renewable technologies represent an important opportunity, but not a panacea for the U.S.
energy economy. Their long-term contribution is predicated on overcoming remaining
technical and cost barriers, mainly through intensified R&D. The National Energy
Strategy's renewable energy initiatives are based on these conclusions and on a clear
understanding of the contributions that renewable energy can and cannot be expected to
make. For example, given policies to address existing regulatory barriers and market
imperfections, solar thermal or photovoltaic electricity technologies can compete today to
provide electricity generation in remote locations and for peaking purposes.
(National Energy Strategy, Executive Summary, 1991/1992)
The Administration supports fundamental and applied research that helps the renewable
industry develop technologically advanced products. [...] Applied research into thin
reflective membrane deposition, airfoil design, and solar module fabrication has reduced
costs and increased productivity from solar thermal power plants, wind turbines, and flat
plate photovoltaic arrays.
[...]
Programs supporting renewable electric supply will contribute 0.6 quads of primary energy
in the year 2000, saving $4 billion in annual fuel costs and reducing 7 million metric tons
of carbon-equivalent emissions.
(Sustainable Energy Strategy, 1995)
2. 314 CHAPTER 17
In Chapter 16 we discussed the following nondepletable energy sources: geothermal, wind,
tidal, wave, hydroelectric and biomass energy. We saw that they will not solve the world's
energy problems. But they are, they can be and they will be important on a local scale. In
Chapter 14 we discussed nuclear fusion; it could solve all our energy problems, but many
technical problems need to be overcome before it can be harnessed and commercialized.
The production of electricity using fusion must go through the ‘bottleneck’ of thermal-to-
mechanical energy conversion, which is inherently inefficient. The last energy source that
we need to discuss, direct solar energy, will solve all society's energy problems, but not
yet. Its efficient large-scale utilization is expected to become a reality some time in the 21st
century (probably in the second half). Its greatest virtue – apart from being free,
inexhaustible, universally available and pollution-free – is that it can be converted directly
into electricity, unlike any other energy source. Its potential, its current status and the
challenges lying ahead are discussed next.
Solar Energy Balance
More than 99.9% of the energy flow on the earth's surface is due to incoming solar
radiation. The rest is from geothermal, gravitational (tidal) and nuclear sources. The sun is
an average-size star, with a diameter of 864,000 miles and 93 million miles away from our
planet. It is a giant nuclear fusion reactor whose interior and surface temperatures are
35,000,000 and 10,000 °F, respectively. Each second 657 million tons of hydrogen
isotopes are converted into 653 million tons of helium. The residual mass of 4 million tons
is converted to energy, according to the Einstein equation, E = mc2:
Power from the sun = (4x109 kg
s
) (3x108 m
s
)2 = 3.6x1026 W
To place this number into perspective, if gasoline were pouring from Niagara Falls, at a
rate of 5 billion gallons per hour, and if we had begun collecting it 3.5 million years ago,
the combustion of all this accumulated gasoline would liberate the amount of energy
equivalent to one minute of the sun's production. The reader is urged to verify this.
Being quite far away from the sun, the earth receives only about half a billionth of this
radiation. But it receives it more or less continuously. About 30% of this energy does not
reach the surface of the earth because it is reflected from the atmosphere (as ultraviolet
radiation, see Figures 3-1 and 11-7). Still, the radiation that does reach the surface is four
orders of magnitude larger than the total world's energy consumption (see Illustration 5-1
and Figure 5-2). In fact, only 40 minutes of sunshine would be sufficient – if available in
adequate forms – to supply the entire annual energy demand on earth.
The if mentioned in the previous sentence is a big one, however. Because solar energy
spreads out more or less evenly through space, it reaches the surface of the earth in quite
3. SOLAR ENERGY 315
diluted form, at a rate of about 220 W/m2 (see Figure 3-1). In other words, if one square
meter were available for conversion of solar energy to electricity (at 100% efficiency), the
energy produced would be sufficient for just two or three light bulbs. The challenge of
solar energy utilization is to concentrate it. Practical ways to achieve this are discussed
below. They include direct solar heating, indirect production of electricity and direct
production of electricity.
Direct Solar Heating
The use of solar rays to achieve effective heating has been practiced since ancient times. In
213 B.C., the Greek savant Archimedes used mirrors to direct sunlight onto the fleet of
Marcellus, the Roman general who tried to capture Syracuse (Sicily), and set his ships on
fire. Today's devices are not necessarily more sophisticated than the ones used by
Archimedes. They are called collectors. A collector is thus a device that collects solar
radiation and converts it to thermal energy.
Figure 17-1 shows the statistics of most recent shipments of solar collectors in the U.S.
The low-temperature collectors are used primarily for less demanding residential
consumption (to heat swimming pools, for example); it is good to see that their sales are up
again. The medium-temperature collectors are used primarily for residential hot water. Both
kinds became popular in the decade of the oil crises (1970s). However, consumer interest
in them decreased sharply when the price of oil decreased in the 1980s (see Chapter 20)
and when Federal solar energy tax credits expired in 1985.
s
s
s
s
s
s
s
s
ss
s
s s
s
s
s
ss
s s
t
t
t
t
t
t
t t
tt
t t t
t
t
t tt t t
1975 1979 1983 1988 1992 1996 2000
0
2
4
6
8
10
12
14
Millionsquarefeet
s
Low-
temperature
collectors
t
Medium-
temperature
collectors
FIGURE 17-1. Shipment of solar collectors in the U.S.
[Source: Energy Information Administration.]
5. SOLAR ENERGY 317
In addition to the collector and the working fluid, a complete active solar system must have
an energy storage facility and/or a backup system, because the sun does not shine all the
time and it may not shine every day. Such a system is illustrated in Figure 17-3. The hot
working fluid (such as antifreeze) exchanges heat with water in the primary loop, similar to
the primary loop of a pressurized water nuclear reactor (see Figure 13-8). In the secondary
loop, this hot water is used to heat the storage tank, from which the hot water is distributed
to the various consumers (for example, a shower in a home or a dishwasher). The size of
the storage system depends on the amount of solar energy incident on the collector and on
the efficiency of the collector. This is shown in Illustration 17-1, based on the information
given in Table 17-1.
In addition to the active solar energy system, passive solar heating system can be used
effectively to reduce the heating (and cooling) requirements of houses and buildings. A
passive system contains no active components, such as collectors and pumps; it relies on
both regular and special features of building design. Walls, ceilings and floors constitute
both the collection and the storage system. Heat is distributed by natural convection.
Building design is optimized to let the sun in and keep it in in the winter, and to do the
opposite in the summer. There are two ways to accomplish this: using the so-called direct
gain and indirect gain.
FIGURE 17-3. Schematic representation of a solar energy storage system.
6. 318 CHAPTER 17
Illustration 17-1. A home in Phoenix (Arizona) requires 62 kWh of heat on a winter
day to maintain a constant indoor temperature of 20 °C. (a) How much collector surface
area does it need for an all-solar heating system that has a 20% efficiency? (b) How large
does the storage tank have to be to provide this much energy?
Solution.
Phoenix is located at about 33 °N, so we can use the data for 32 °N given in Table 17-1.
The average solar radiation in winter is about 6.5 kWh/m2/day. Hence, the daily quantity
of thermal energy obtained using collectors will be:
Thermal energy = 6.5
[kWh (solar)]
m2 day
[0.20 kWh (thermal)]
[1 kWh (solar)]
= 1.3
kWh
m2 day
This means that for every square meter of collector surface area, 1.3 kWh of heat are
produced every day. Therefore, the required collector surface area is obtained as follows:
Collector surface area =
62
kWh
day
1.3
kWh
m2 day
= 48 m2
So a collector 6 m long and 8 m wide would do the job. Obviously, it can be placed on
the roof. The size of the storage tank can be obtained by remembering the quantitative
definition of heat (Chapter 3):
Heat = [Mass] [Heat capacity] [Temperature difference]
Here the mass is that of the storage medium, water, which needs to be determined. The
heat capacity of water is 1 kcal/kg/°C (see Table 3-2), and the temperature difference is
that between the hot fluid in the secondary loop and the cold water going into the storage
tank (say, 60 – 20 = 40 °C); see Figure 17-4. Therefore, the required mass of water for a
day's worth of heat is obtained as follows:
Mass =
Heat
[Heat capacity] [Temperature difference] =
=
62 kWh
(1
kcal
kg °C) (40 °C) (
1.16x10-3 kWh
1 kcal )
= 1336 kg H2O
This is equivalent to a volume of 1336 liters (or about 350 gallons), because the density
of water is 1 kg/L.
7. SOLAR ENERGY 319
TABLE 17-1
Variation of solar radiation (in W h/m2) with time and latitude
Date Perpendicular Horizontal Vertical South 60° South
October 21
32°N 8,498 5,213
40 °N 7,735 4,249 5,212 6,536
48 °N 6,789 3,221
November 21
32 °N 7,584 4,035
40 °N 6,707 2,969 5,314 6,013
48 °N 5,257 1,879
December 21
32 °N 7,401 3,581
40 °N 6,235 2,465 5,188 5,660
48 °N 4,551 1,406
January 21
32 °N 7,748 4,060
40 °N 6,878 2,988 5,440 6,127
48 °N 5,390 1,879
February 21
32 °N 9,053 5,434
40 °N 8,321 4,457 5,452 6,858
48 °N 7,344 3,404
March 21
32 °N 9,494 6,569
40 °N 9,191 5,838 4,677 6,852
48 °N 8,763 4,974
[Sources: Kraushaar and Ristinen, op. cit.; A.W. Culp, Jr., “Principles of
Energy Conversion,” McGraw-Hill, 1991.]
Direct gain refers to systems that admit sunlight directly into the space requiring heat. The
maximum reception of sunlight is obtained through windows facing south, as shown in
Figure 17-4 (see also Table 17-1). The sunlight received during the day – while it lasts –
must be absorbed by a high-heat-capacity material on the floor or the walls. As shown in
Table 3-2, dense substances such as concrete, brick, stone, adobe and water can store
relatively large quantities of heat in a reasonable amount of space. When the sun ceases to
8. 320 CHAPTER 17
shine, the warm floor and walls transfer the accumulated heat to the cold space in the
house.
Indirect-gain passive systems are those that also absorb solar radiation in a high-heat-
capacity material, such as an outside concrete wall. The accumulated thermal energy is then
transferred to the space needing heat. The south-facing Trombe wall, named after the
French engineer Félix Trombe, is the most commonly used passive solar structure. It is
built of concrete, brick or stone; it can even be filled with water. It is often painted black
for maximum absorption of radiation. This increases its efficiency but does not help to
embellish the neighborhood; there are regulations in some residential areas that do not allow
these structures on the street-facing side of the house. An alternative system is a roof pond:
water is contained in large, shallow bags between the ceiling and the roof. Movable
insulating material separates it from the roof. During the day, insulation is removed to
allow sunlight to strike the pond; during the night, it is placed back in its position so that it
allows the heat to be transferred mostly toward the inside of the house.
The most familiar example of a passive solar system is the greenhouse, also called
sunspace or sunporch. It is used both for growing plants and for residential comfort in
winter. It combines direct and indirect gain, by letting the sunshine into the room through
south-facing glass and absorbing the radiation on a brick wall inside the room. (This is the
origin of the term “greenhouse effect,” discussed in Chapter 11.)
FIGURE 17-4. Solar heat gain for different window orientations.
[Source: G. Aubrecht, op. cit.]
9. SOLAR ENERGY 321
In the ruins of ancient civilizations, there are numerous examples of very effective passive
solar heating and cooling systems. The ancient cliff dwellings in the Mesa Verde National
Park in Colorado are a familiar example. As the cost of heating and cooling increases in our
days, architects, home owners and builders are wise in remembering these examples and
adapting them to current building materials and lifestyles. It is well documented that they
can provide significant energy savings.
Indirect Production of Electricity
The use of a more sophisticated collector system – compared to the one represented in
Figures 17-3 and 17-4 – allows the working fluid to achieve a higher temperature. Such a
system can then be used to produce electricity. This is illustrated in Figure 17-5. A solar
thermal power plant is essentially identical to an ordinary steam-turbine power plant, except
that it gets the heat from solar radiation rather than from combustion or nuclear fission.
FIGURE 17-5. Schematic representation of a solar thermal power generation plant.
10. 322 CHAPTER 17
A flat-plate collector typically raises the temperature of the working fluid to about 100 °C. A
number of flat-plate collectors placed in series can raise the temperature of the working
fluid to levels that can provide economically competitive electricity. For example, the
maximum efficiency of the turbine of a power plant whose entering steam temperature is
200 °C would be
Emax =
TH – TL
TH
=
(200 + 273) – (100 + 273)
(200 + 273)
= 0.21
This is a low efficiency, but the ‘fuel’ (solar energy) is free. A higher temperature can be
achieved by using concentrating, or focusing, collectors – as Archimedes did to burn
Roman ships. With the use of parabolic trough collectors, for example, steam temperatures
of up to 300-400 °C can be reached. This technology is currently cost-competitive in certain
markets. In the Mojave desert (Kramer Junction, CA), Luz International has built a plant
that delivers 354 MW of electricity to Southern California Edison's power grid (see
Investigation 17-1).
Temperatures as high as those in conventional power plants can be achieved easily with
solar tower technology. Here, a system of computer-controlled mirrors (called heliostats)
tracks the sun across the sky so that the reflected sunlight from all the mirrors falls on a
central tower containing water or oil or, in more recent designs, a molten salt. At Barstow,
California, some 1900 heliostats were used to raise the temperature of water to 510 °C and
the 10 MW(e) Solar One plant had an overall efficiency comparable to that of conventional
power plants. And the new 10-MW(e) Solar Two at the same location is advertised today
as the world's most technically advanced solar power plant. It uses a molten salt as the heat
transfer fluid. The advantage is that the thermal energy collected during sunny hours can be
stored in the molten salt (see Illustration 17-2) and used on cloudy days or at night. If
successful, it will pave the way for a new generation of commercial power plants.
Illustration 17-2. How much less heat storage medium would be needed in Illustration
17-1 if a molten salt were used instead of water? Because it undergoes a phase change
(from solid to liquid), the amount of heat that can be stored in the salt is larger, say 120
BTU/lb, than the amount that can be stored in water.
Solution.
The mass of molten salt required is
Mass =
Heat
[Heat capacity] [Temperature difference] =
(62 kWh) (
3414 BTU
1 kWh
)
120
BTU
lb
= 1764 lb
Compare this to almost 3000 pounds of water needed for the same heat storage task.
11. SOLAR ENERGY 323
The Department of Energy reports that annual shipments of these high-temperature
collectors were less that 5 thousand square feet in 1994, down from 5.24 million square
feet in 1990. Clearly, non-electric use of low- and medium-temperature solar collectors is
more popular at the present time (see Figure 17-1).
Direct Production of Electricity
Indirect production of electricity from solar energy, while quite promising because of recent
significant progress in technology and in economic competitiveness (see Chapter 18), has
two major drawbacks. Because of its relatively low efficiency (especially using flat-plate-
collector systems), the size of the proposed solar farms can be very large. This is illustrated
below.
Illustration 17-3. How much collector area would a 1000-MW(e) solar farm require if
the individual efficiencies of the collector system, turbine and generator are 30, 25 and
90%, respectively?
Solution.
Let us assume that the average incident solar radiation at the proposed site of the plant is
200 W(solar)/m2. This means that 1 m2 of earth's surface receives 200 W of solar
radiation. If a collector is placed on this surface, it will convert 30% of this energy into
heat; therefore for every square meter of collector, 60 W of thermal energy will be
available. Now, taking into account the efficiencies of the turbine and the generator, we
have that the collector area required is:
Collector area = (
1 m2
60 W(th)
) (
1 W(th)
0.25 W(m)
) (
1 W(m)
0.9 W(e)
) (109 W(e)) = 7.4x107 m2
Thus, with the efficiencies given above, this solar farm would occupy an area of about 75
square kilometers. If land is expensive, this would represent a significant capital
investment.
Direct conversion of solar energy to electricity would not only avoid this problem, but
would avoid the “thermodynamic bottleneck” illustrated in Figure 17-6, which none of the
technologies mentioned so far are capable of doing. In most of our discussion of electricity
generation so far, the energy conversion path has been the one shown in the upper portion
of Figure 17-6.
The direct conversion of chemical energy to electricity is possible in devices called fuel
cells. These are a type of large-scale batteries that have been used for decades in the NASA
12. 324 CHAPTER 17
space programs. In contrast to ordinary batteries, however, fuel cells require a continuous
supply of chemical energy (from natural gas, for example) and the electrode material is not
depleted as it supplies electricity. Their commercial use in power plants and electric
transportation is increasingly being considered, particularly in densely populated areas
(because of their very low environmental emissions and silent operation). A 4.8 MW(e)
demonstration plant had been operational in downtown Manhattan since the early eighties.
A number of utility companies across the U.S. have purchased 2 MW(e) plants, one of
them to power the New York City subway system (The New York Times, June 30, 1991,
p. F6). More recently, a 2 MW(e) plant that is considered to be simpler and more efficient
than many other types of fuel cell power plants was connected to the grid of the Santa Clara
municipal electric system. (For an update on this Santa Clara demonstration project, see
www.ercc.com/scdp.html. For an update on fuel cell technology in general, visit the Web
site of the Morgantown Energy Technology Center of the Department of Energy,
www.metc.doe.gov.)
Chemical/
Nuclear
Energy
Thermal
Energy
Mechanical
Energy
Electricity
Thermal
Energy
Mechanical
Energy Electricity
Solar
Energy
Fuel Cells (e.g., batteries)
Solar Cells
FIGURE 17-6. Energy conversion pathways of fuel cells and solar cells.
Like fuel cells, solar cells produce electricity directly, without going through the
thermodynamically unfavorable conversion of high-entropy thermal energy into low-
entropy mechanical energy (remember Chapter 3). Therefore, in theory at least, the
efficiency of this conversion could be as high as 100% and this – together with the fact that
solar energy is free, inexhaustible and nonpolluting – provides great incentive to develop
this new technology.
13. SOLAR ENERGY 325
A solar cell, also called photovoltaic cell, is thus a device that directly converts solar
radiation into electricity. It is based on the photoelectric (or photovoltaic) effect, which was
known since the early 19th century, but which was translated into a useful device only in
the 1950s, in response to the needs of the U.S. space program. This effect, exhibited by
materials called semiconductors (such as silicon), is illustrated in Figure 17-7. Transistors
and computer chips, which have revolutionized the electronics industry since the 1940s, are
also made from semiconducting materials.
Valence band
Conduction band
Band gap
ElectronEnergy
Band-gap
energy
(photons)
FIGURE 17-7. Photovoltaic effect in semiconductors.
The electrons that have the potential to create an electric current are normally tied up in their
valence band, that is, at a low energy level. An energy barrier (called the band-gap energy)
must be overcome before they can become carriers of electricity in this material, by jumping
into the so-called conduction band. Solar radiation, in the form of elementary particles
called photons, provides the needed energy; the photons strike the surface of the
semiconductor and some of the valence electrons are ejected into the conduction band.
They are thus made free or available for conduction of electricity. But for the production of
electricity, the actual solar cell device must be made from two different types of so-called
’doped’ semiconductors. This is shown in Figures 17-8 and 17-9 and described below.
14. 326 CHAPTER 17
n-type p-type
p/n
Conduction band
Valence band
Electronenergy
n-type p-type
p/n
FIGURE 17-8. The charge distribution in the p/n junction region of a solar cell:
(a) without solar radiation; (b) with solar radiation.
In a normal silicon crystal, there are four valence electrons in every atom. They are held in
place by the positive charge from the nuclei of the silicon atoms. They easily come back to
the valence band before they can give up their energy in an external electric circuit.
However, if the silicon is doped with a small quantity of an element that has five valence
15. SOLAR ENERGY 327
electrons and can fit into the silicon crystal structure (such as phosphorus or arsenic), some
extra electrons are created. Such a doped material is called an n-type semiconductor,
because the extra electrons carry a negative charge. Alternatively, if the semiconductor is
doped with an element that has only three valence electrons (such as boron or gallium),
instead of creating extra electrons, extra missing electrons, or positive holes, are created.
This is a p-type semiconductor. Still, both materials are electrically neutral when they are
separated: in the n-type material the negative charge of the extra electrons is balanced by
the higher positive charge of the dopant nuclei (e.g., phosphorus), and in the p-type
material the extra electron holes are balanced by the lower positive charge of the dopant
nuclei (e.g., boron).
When these two types of material are combined, a p/n junction is formed. This is what
makes possible the production of electricity, as opposed to simple conduction of electricity
in a semiconductor illuminated by solar radiation. Because of the high concentration of
electrons in the n-type semiconductor, some of the extra electrons spill over into the holes
of the p-type semiconductor. This makes the n-type material positively charged in the
vicinity of the junction. Conversely, the p-type material becomes negatively charged in the
vicinity of the junction. An (internal) electric field across the junction is thus created.
Normally, however, there is equal flow of electrons in both directions across the junction
(Figure 17-8a) and no electricity can be produced.
p-n junction
p-type
semiconductor
n-type
semiconductor
resistance
load
(flow of electrons)
FIGURE 17-9. Schematic representation of a solar cell.
16. 328 CHAPTER 17
When solar radiation strikes the solar cell (Figure 17-8b), excess electrons flow from the n-
type material to the p-type material and excess holes ‘flow’ in the opposite direction. This,
together with the existence of the electric field across the junction, makes possible the flow
of electrons away from the (charge-separating) junction and through an external circuit
(Figure 17-9). Thus, solar energy is converted into electricity.
Figures 17-10 and 17-11 summarize the growth of the photovoltaic-cell market in the
U.S. and the world. The contribution to the overall energy supply is still low (see Chapters
5 and 18) but the growth has been phenomenal. It has occurred mostly in the developed
nations (U.S., Japan, Europe). The growth in the U.S. has been most significant in the
residential sector. Developing nations (such as Brazil, India, and China) have also
contributed to the worldwide growth, because one of the key advantages of the
photovoltaic technology is its rural applicability, in remote areas lacking access to central
power supplies. The cumulative world capacity now approaches 600 MW. It is mostly
used for on-peak consumption (see Chapter 18). It must be concluded, however, that both
economic and efficiency problems still stand in the way of large-scale commercial
utilization of this technology.
sssss
sss
s
s s
s
s
s
s
s
s
ss
s
s
t
t
t
ttt
t
tttt
t
t
t
1975 1980 1985 1990 1995 2000
0
10
20
30
40
50
60
70
80
90
Solarcellshipments(megawatts)
s World
t United States
FIGURE 17-10. Use of solar cells in the U.S. and the world in the past two decades.
[Source: Vital Signs 1996, Worldwatch Institute, and Energy Information Administration.]
Every new incremental increase in the efficiency of a solar cell attracts a great deal of
attention in the popular press. While there are no thermodynamic limitations, as mentioned
above, there are inherent energy losses that severely limit the performance of currently
available cells. These include optical losses (for example, reflection of the radiation from
the cell's surface, before reaching the p-n junction) and the (more serious) inability of the
17. SOLAR ENERGY 329
currently designed cells to provide for the conversion of the entire sunlight spectrum (see
Figure 2-2) into electricity. Despite these limitations, the efficiency of an individual solar
cell has increased from 5% in the early designs to about 35% in the most advanced designs.
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
0
5000
10000
15000
20000
25000
30000
35000
Residential
Commercial
Government
Industrial
Transportation
Electric Utility
Other
FIGURE 17-11. U. S. photovoltaic energy contribution by economic sector (in
kilowatts purchased). [Source: Energy Information Administration.]
More important than the issue of efficiency is the cost issue – after all, solar energy comes
for free – and here dramatic changes have taken place. This is illustrated in Figure 17-12.
In Vital Signs 1996, the Worldwatch Institute reports no additional decrease in the price of
solar electricity; today solar cells cost $3.50-4.00 per watt. In a recent NYT article (“70's
Dreams, 90's Realities. Renewable Energy: A Luxury Now. A Necessity Later?,”
4/11/95), the following costs for a kilowatthour of electricity are given:
Natural gas 3 cents
Wind 5 cents
Geothermal 5.5 cents
Solar (thermal) 14 cents
A similar summary was published in a May 1994 issue of Business Week (“The sun shines
brighter on alternative energy”):
Coal 4-5 cents
Natural gas 4-5 cents
Wind 5-9 cents
Geothermal 5-8 cents
18. 330 CHAPTER 17
Hydropower 4-7 cents
Biomass 6-8 cents
Solar (thermal) 10-12 cents
Photovoltaic 30-40 cents
(Environmental benefits of solar energy may not have been factored into these prices; see
Chapter 21.) In these circumstances, some companies in the U.S. have abandoned solar
energy, unsure of when they will be able to convert it into electricity with a profit (see
“U.S. Companies Losing Interest in Solar Energy,” in the NYT of 3/7/89; see also
Investigation 17-1). Others are using cheaper but lower-efficiency materials (thin films of
amorphous silicon) and are still working on efficiency improvements.
During the Bush Administration, the Department of Energy had anticipated (in its
National Energy Strategy) that utility-scale applications of photovoltaics will reach
commercial level around the year 2015. Current official projections do not seem to be as
optimistic. In the Sustainable Energy Strategy, the statement about DOE's Photovoltaics
System Program is more vague when it comes to commercial-scale utilization: “[This]
Program supports private sector research to develop roofing materials and windows that
incorporate photovoltaics and can produce electricity. These efforts are pursued in close
collaboration with industry in programs with the Utility PV Group.”
Finally, photovoltaic technology is expected to bring closer to reality the use of
hydrogen as an energy source. The concept is illustrated in Figure 17-13. It is a sun-
assisted water cycle. Solar radiation is converted to electricity, which is then used to break
up water into hydrogen (H2) and oxygen (O2). Hydrogen is then used as a clean gaseous
fuel, whose combustion regenerates water, produces a lot of energy (274 BTU/ft3) and
causes no pollution. But don't expect to see this wonderful technology at your local electric
utility any time soon (in your lifetime, I mean).
INTERNET
INFO
For the most recent developments in solar energy and other renewable
energy sources, visit the following Internet sites:
•www.nrel.gov;
•www.eren.doe.gov/RE/solar.html
•solstice.crest.org
•www.energy.ca.gov/education/index.html
•www.crest.org/renewables/usecre//
•www.ises.org/
19. SOLAR ENERGY 331
FIGURE 17-12. History and projections of solar electricity costs.
[Sources: C.J. Weinberg and R.H. Williams, “Energy from the Sun,” Scientific American,
September 1990, p. 154.]
FIGURE 17-13. Conceptual scheme of the use of solar cells to produce hydrogen.
20. 332 CHAPTER 17
REVIEW QUESTIONS
17-1. Show the origin of the numbers quoted at the beginning of this chapter from the
Sustainable Energy Strategy.
17-2. On p. 314 it is stated that only 40 minutes of sunshine would be sufficient to supply
the entire annual energy demand on earth. Show where this number comes from.
17-3. It has been reported that the latest module of the SEGS (solar electric generating
system) plant in Kramer Junction, CA generates 80 MW of electricity by using 483,360
square meters of collectors to achieve an annual output of 260 gigawatthours. Check
whether these numbers make sense. What is the efficiency of the collectors?
17-4. In 1994 the Spanish El País has reported on the largest photovoltaic power plant in
Europe, near the city of Toledo. Its electric capacity is 1 MW (enough for 2000 people, the
paper says), and the total area of the solar panels is reported to be 16,700 square meters.
Do these numbers make sense? What is the efficiency of these solar cells?
17-5. Indicate whether the following statements are true or false:
(a) A solar cells converts solar radiation directly into electricity.
(b) A window in New York City that is facing south receives as much as three times more
solar radiation than a window facing north.
(c) From 1980 to 1983 the sales of medium-temperature solar collectors exceeded the sales
of low-temperature solar collectors.
(d) In 1995 U.S. sales of photovoltaic cells represented less than 50% of world sales.
(e) In 1983 U.S. sales of photovoltaic cells represented less than 50% of world sales.
(f) The principal customers for the photovoltaics industry are the electric utilities.
(g) In 1990 more than 50% of the photovoltaics have been sold to the residential and
commercial sectors.
INVESTIGATIONS
17-1. It may be difficult to keep up with all the technical, economic and political
developments in solar energy. The Internet is the ideal tool to try to accomplish this, but
distinguishing facts from both fiction and propaganda may be time-consuming. Spend
some time surfing the Internet to find out about the current status of the SEGS plant in
Kramer Junction, CA and about the company that has pioneered this technology, Luz
International. Use at least two search engines and check at least three different Web sites.
17-2. Use of photovoltaics in rural areas may already be cost-competitive with conventional
technologies. See why it makes sense in South Africa (“Solar power: Night and day,”
Economist of 9/9/95) and elsewhere in the developing world (“Here Comes the Sun,” Time
21. SOLAR ENERGY 333
of 10/18/93, and “A Sunny Forecast,” 11/7/94; and “America Unplugged,” Newsweek of
10/18/93).
17-3. The following companies have been reported to be involved (in May 1994) in
developing photovoltaic technology: Siemens Solar Industries, Solar Engineering
Applications, United Solar Systems, Canon USA, Alpha Solarco, Solarex, Bechtel Power,
Mobil Solar Energy, Amonix, Ascension Technology, Cummins Engineering, Scientific
Analysis, Fresnel Optics, Texas Instruments, Integrated Power and SunPower. See
whether they have Web sites. How many of them are still in the business? Maybe you'll
even want to invest in some of them...
17-4. The Enron Corporation has been known as a natural gas company (see Investigation
9-6). But they were (and still are?) also interested in photovoltaics (“Solar Power, for
Earthly Prices,” NYT of 11/15/94). Find out about the fate of their pledge “to deliver the
electricity at 5.5 cents a kilowatthour in about two years.” See also NYT of 12/4/94
(“Thirsty New Solar Cells Drink In the Sun's Energy”).
17-5. Find out more about the direct conversion of chemical energy to electricity
accomplished by fuel cells. See BW of 5/27/96 (“How To Build a Clean Machine: Fuel
cells are powering hospitals. Cars are down the road.”) and Economist of 2/5/94 (“The
different engine: Fuel cells are efficient, clean and quiet. So why are they also rare?”)
17-6. Find out more about the possibilities of using gaseous hydrogen (H2) as a fuel. See
NYT of 4/16/95 (“Use of Hydrogen as Fuel Is Moving Closer to Reality”). See also
Popular Science of 10/93 (“The Outlook for Hydrogen”).