What Is Energy From The Sun Contained In?
What is Solar Energy?
Solar energy is the radiant energy emitted from the sun that reaches the Earth. It is a renewable energy source that can be converted into other forms of energy, such as heat and electricity.
The sun produces energy through a process called nuclear fusion. In the sun’s core, hydrogen atoms fuse together to create helium atoms, releasing enormous amounts of energy in the process. This energy radiates out from the sun in the form of electromagnetic radiation, including visible light, ultraviolet light, and infrared radiation [1].
When solar radiation reaches the Earth, it can be converted directly or indirectly into other useful forms of energy. Solar panels containing photovoltaic cells can convert sunlight directly into electricity. Solar thermal collectors can harness solar energy to directly heat water or spaces. Passively designed buildings can use sunlight to provide interior lighting and warmth. Plants can undergo photosynthesis to store solar energy chemically.
The amount of solar energy striking the Earth’s surface annually is more than 7,500 times the world’s total annual energy consumption [2]. Effectively harnessing even a tiny fraction of this abundant renewable resource can help reduce reliance on finite fossil fuels.
History of Solar Power
The origins of solar power as a source of energy date back to the 7th century B.C.E when magnifying glass were used to concentrate the sun’s rays to make fire. However, the authentic discovery of the photovoltaic effect (that generates electricity from sunlight) is credited to the French physicist Edmond Becquerel in 1839. In 1873, Willoughby Smith discovered the photoconductivity of selenium. In 1883, Charles Fritts created the first solar cell by coating selenium with a thin layer of gold. In the early 20th century, Albert Einstein helped explain the photoelectric effect, which contributed to the development of viable solar technology. Significant advancement in solar cells came in 1954 when researchers at Bell Laboratories accidently discovered that silicon doped with certain impurities was very sensitive to light, resulting in a large uptick in electrical conductivity. This led to the production of the first practical photovoltaic cells able to convert enough of the sun’s energy into power to run everyday electrical equipment. In 1961 the first solar cell satellite, Vanguard 1, was launched by the U.S. Since the late 1970s, manufacturing methods for photovoltaic panels have further improved efficiency and reduced costs, helping drive the boom in solar installations seen today.
Sources:
https://en.wikipedia.org/wiki/Solar_power
https://www.instituteforenergyresearch.org/renewable/solar/history-of-solar-power/
How Solar Panels Work
Solar panels work by converting sunlight into electricity. At the heart of a solar panel are solar cells, which are made of semiconducting materials like silicon [1]. When sunlight hits these solar cells, the photons from the sunlight knock electrons loose from the atoms in the solar cell [1]. This creates flow of electricity.
Solar panels are made up of many solar cells wired together. The loose electrons flow from one solar cell to the next, creating an electrical current. The solar cells are sandwiched between a glass cover plate on top and a metal backing plate on the bottom. The glass allows sunlight to pass through and hit the solar cells, while the metal backing conducts the electricity away and out of the solar panel.
When sunlight, made up of photons, hits the solar cell, each photon contains enough energy to dislodge an electron from an atom. As more photons hit the cell more electrons are knocked loose. Metal plates on the bottom and top of the cell collect the electrons and transfer them to wires to create electricity. This flow of electrons is the electricity that can then be used to power electrical devices or sent to the power grid.
Types of Solar Panels
There are two main types of solar energy technologies: photovoltaics (PV) and concentrated solar power (CSP).
Photovoltaic panels, commonly known as solar panels, are made up of solar cells containing photovoltaic material that converts sunlight directly into electricity. The most common PV panels use either monocrystalline or polycrystalline silicon cells. Thin-film solar cells use amorphous silicon or other semiconductors and are less expensive but less efficient than crystalline silicon cells.
Concentrated solar power systems use mirrors or lenses to concentrate sunlight onto a receiver which converts it into heat. This heat can then be used to drive a heat engine and generator to produce electricity. CSP technologies include parabolic troughs, parabolic dishes, linear Fresnel reflectors, and solar power towers.
The main tradeoff between crystalline silicon and thin film PV panels is efficiency vs. cost. Monocrystalline silicon cells are the most efficient but also the most expensive. Thin-film panels are cheaper but less efficient, so more surface area is needed to generate the same amount of electricity. Polycrystalline silicon offers a compromise between efficiency and cost.
Sources:
https://www.energysage.com/solar/types-of-solar-panels/
Solar Panel Efficiency
Solar panel efficiency refers to how much of the sun’s energy striking a panel is converted into usable electricity. It is measured as a percentage. The higher the percentage, the greater the conversion efficiency. According to Energysage, solar panel efficiency typically ranges from 15% to 22% for residential panels [1]. However, factors like panel technology, size, temperature, shading and power inverter all impact the efficiency.
The most common solar panel technology uses monocrystalline silicon cells which typically have an 18% to 22% efficiency range. Polycrystalline silicon cells are slightly less efficient at 15% to 18%. Newer technologies like SunPower’s A-Series panels use silicon in a different way and achieve over 22% efficiency. Factors like high temperatures and shading even a small part of a panel can reduce efficiency by 10% to 25%. Using a quality solar inverter that converts DC electricity to AC electricity also impacts the system’s overall efficiency.
Advantages of Solar Energy
One of the biggest advantages of solar energy is that it is a renewable resource. The sun produces an enormous amount of energy every day and this energy source will continue for billions of years to come. Unlike fossil fuels which are finite, solar energy can provide electricity without end. Being renewable means solar energy has a tiny carbon footprint compared to traditional energy sources.
Solar energy systems generate electricity without releasing carbon dioxide or other greenhouse gases that contribute to climate change. According to the U.S. Energy Information Administration, the electricity sector contributes 25% of global greenhouse gas emissions. Using solar energy can significantly reduce these emissions and provide a clean energy alternative.
Installing a solar energy system on homes or businesses can greatly reduce electricity bills. Once the system is paid off, solar panels provide free electricity for decades with practically no maintenance costs. Solar energy allows consumers to reduce their reliance on utilities and become more energy independent. The U.S. Department of Energy estimates solar panels can cut electricity bills by 50% to 70%.
Disadvantages of Solar Energy
While solar energy has many benefits, there are some disadvantages to consider as well. One key disadvantage is intermittency – solar energy relies on sunlight to generate electricity, so cloudy days and nighttime can limit energy production. According to the U.S. Energy Information Administration, the capacity factor for utility-scale solar PV is around 27%[1]. This is much lower than some other energy sources like natural gas or nuclear.
Another disadvantage is the high upfront cost. Installing solar panels on a home can cost anywhere from $10,000-$25,000 after rebates and incentives depending on the size of the system[2]. Even larger utility-scale solar farms require significant investment. This can limit adoption, especially in developing countries.
Solar farms also require a lot of land space. According to the National Renewable Energy Laboratory, it takes about 3.4 acres of land to produce 1 MW of solar power capacity[3]. This large land use requirement could compete with agriculture or wildlife habitats in some instances.
Solar Energy Storage
Solar energy can be stored for later use through several methods. The most common methods are batteries, thermal storage, and pumped hydro storage.
Batteries
Batteries are used to store solar energy collected during the day for use when the sun isn’t shining. The most common types of batteries used are lithium-ion and lead-acid batteries. Lithium-ion batteries have high energy density and efficiency which makes them well-suited for home solar storage. Lead-acid batteries are cheaper but have shorter lifespans. Tesla and other companies now offer large capacity lithium-ion battery systems for home use.
Thermal Storage
Thermal storage involves heating or cooling a storage medium so that the stored energy can be used at a later time for heating and cooling needs. This allows solar energy collected during the day to be used after sunset. Molten salt and water are common thermal storage mediums.
Pumped Hydro Storage
Pumped hydro storage uses excess solar power to pump water uphill into a reservoir. When energy is needed, the water is released downhill to turn hydroelectric turbines. This is currently the largest-capacity form of grid energy storage.
Overall, energy storage enables solar energy to be used anytime, even when the sun isn’t shining. Continued advances in storage technology will further increase the viability of solar power.
Notable Solar Installations
Some of the largest and most notable solar installations around the world include:
Bhadla Solar Park, India
Located in Rajasthan, India, Bhadla Solar Park is one of the largest solar parks in the world. It has an installed capacity of 2,245 MW and plans to expand to over 10,000 MW. The solar park spans over 14,000 acres of land.
Tengger Desert Solar Park, China
With an installed capacity of 1,547 MW, the Tengger Desert Solar Park in northwest China is the world’s second largest solar park. The $3 billion project contains over 6 million solar panels and provides electricity to approximately 1 million households.
Kurnool Ultra Mega Solar Park, India
Currently under construction in Andhra Pradesh, India, the Kurnool Ultra Mega Solar Park will have an installed capacity of 1,000 MW upon completion. It will span across 5932 acres and generate enough electricity to power 700,000 homes.
Longyangxia Dam Solar Park, China
The Longyangxia Dam Solar Park in China is one of the world’s largest hydro-solar hybrid projects. With an installed solar capacity of 850 MW, the solar farm supplements hydropower generation at the dam.
Kamuthi Solar Power Project, India
Located in Tamil Nadu, India, the Kamuthi Solar Power Project has an installed capacity of 648 MW. With around 2.5 million solar modules, it is considered to be the world’s largest single location solar power plant.
Future of Solar Energy
As solar technology continues to improve, the future looks bright for solar energy. Researchers are focused on increasing solar panel efficiency and developing new solar technologies to maximize energy production.
One area of focus is improving solar cell efficiency. Currently most solar panels on the market have efficiencies between 15-22%, but researchers are developing new materials and manufacturing techniques to push efficiencies higher. Perovskites solar cells, for example, have reached over 25% efficiency in lab tests and have potential to reach 30% (Source). Another promising technology is multi-junction solar cells which use multiple semiconductor layers to absorb different wavelengths of light.
New solar technologies like organic photovoltaics and quantum dot solar cells are also being researched. These innovative designs could enable flexible, transparent solar panels. Concentrated solar power plants can also store heat energy to provide electricity when the sun isn’t shining.
The growth projections for solar energy are very positive. Solar power capacity is expected to grow from under 1% of U.S. electricity generation today to over 20% by 2050 according to projections by the Department of Energy (Source). With solar costs continuing to decrease and efficiency improving, solar will become more and more competitive with fossil fuels.
