Solar Energy
Solar Energy Background
What can be more useful for humanity if not an unlimited power source, which we can use without any harm to the environment? Probably nothing, but solar power. Humanity has always tried to conquer the unlimited power of the sun – the history of solar technology dates back to the 7th Century B.C. and continues to this day. In the beginning, we tried to concentrate the sun’s heat by using glass, mirrors or other devices to light fires. From those times, we greatly progressed, but still we did not conquer this magnificent source of power.
Why should we develop solar power technologies? Because they have many pros with few or even without any cons. Freely obtained, almost unlimited solar power can solve most of humanity’s problems: it will help us overcome the petroleum and log-burning era, solve environmental problems caused by non-wise usage of conventional power sources; solar power can save trees and greenery all over the world.
Satellites, loaded with solar energy can be directed to places all over the world – they can be used to help people who are trapped in natural disasters, it is inexhaustible, it does not affect earth’s nature; thus, it has a very high potential. The cons of this power source are few but significant: it is expensive; it occupies vast extensions of land. However, technology is still in development, so we can expect future improvements.
As previously indicated, the history of solar power dates back to hundreds of years ago, as magnifying glass was used to start fires. According to Aarre (2013), old tales claim that Greek inventor Archimedes created a so-called “heat ray” to destroy enemy ships, which consisted of a “collection of mirrors that concentrated sunlight onto the ships”, which is similar to the fundamental principles of current solar power generation systems used today.
Shahan (2012) contends that in modern times, Edmond Bequerel, who discovered the photovoltaic effect, achieved the first milestone of solar power technology in 1839. Bequerel was conducting experiments using electrolytic cells, upon which he discovered that when exposed to light, certain materials generate electric currents. Years later, in 1876, William Adams and Richard Day assured selenium is one of those materials. These findings represented the foundation for the development of photovoltaic cells.
Bell Laboratory employees Calvin Fuller, Daryl Chapin and Gerald Pearson developed the first silicon solar cell in 1954, as explained by Go Solar California. Hoffman Electronics was the first company to undertake the task of commercializing PV cells in 1955, indicates Go Solar California. However, the first cells to enter the market had significantly low efficiency levels (2%) and were considerably expensive for the general population. Efficiency later increased to approximately 11%. Solar panels became competitive when Dr. Elliot Berman from Exxon Corp used lower-grade silicon and cheaper housings for cells and achieved significant cost reductions. Thereafter, solar cell technologies use increased as they have become more accessible, particularly in remote areas.
Concentrating Solar Power Systems work under a different basic principle: conversion of solar energy into mechanical energy, which is subsequently converted into electricity. Smith (1995) attributes the earliest conversion of solar radiation into mechanical power to Auguste Mouchout, who invented the first solar motor, as he envisioned the need to reduce fossil fuel dependency. Mouchout developed an apparatus involving an iron cauldron enclosed in glass, which was exposed to and trapped solar radiation, which was transmitted to water for heating. He then included a reflector to his design for additional sunray concentration, and successfully used this device to drive a steam engine. Unfortunately, the French Government judged the device as unpractical, given that coal prices were at a record low, which significantly reduced the attractiveness of a solar motor. In 1878, English researcher William Adams developed the first solar tower, which consisted of flat-silvered mirrors in a semicircular arrangement to form a reflector. Throughout the years, these systems have been improved by concocting more efficient mirror arrangements, heat transfer fluids and other factors, which have allowed obtaining higher temperatures from the collection of the sun’s radiation.
Therefore, solar power is a renewable source of energy, which converts sunlight into electricity by directly using photovoltaic or indirectly – concentrated solar power. Photovoltaic (further – PV) – are used to power up small or medium applications, from pocket watch and calculator to solar-powered smart houses.
Fundamentals of Solar Power Generation
Solar energy refers to the power obtained through the transformation of the sun’s radiation and heat intro electricity. Two different methods are used to perform this conversion: Concentrating Solar Power Systems (CSP) and Photovoltaic Cells (PV).
Concentrating Solar Power Systems
Concentrating Solar Power Systems consist of the use of lenses or mirrors to concentrate the radiation emitted from the sun, to elevate the temperature of Heat Transfer Fluids. According to Machinda, Chowdbury, Arscott and Kibaara (2011), these fluids are used to increase the temperature of water until it is turned into super-heated steam, which proceeds to complete a conventional thermal-to-electric Rankine cycle. The steam is used to drive a turbine, which uses its thermal energy and converts it into mechanical energy, subsequently converted into electric power by a generator that is driven by the turbine’s rotating shaft. CSP systems are divided in:
Line-focusing systems.
Point-focusing systems.
Solar tower systems.
Photovoltaic Cells (PV)
Photovoltaic Cells directly convert sunlight energy into electricity. Solar panels consist of arrangements of PV cells, and are used for solar power generation systems. These cells generate electricity by exploiting the physical properties of semiconductor materials, which are composed of p-n junctions. When sunlight strikes the panels’ surface, they raise the energy level of the electrons and free them from their atomic shells (Penick and Louk, 1998, p. 3), which are then forced to establish a flow of electric current. The most used type of solar cells are Crystalline-Silicon (c-Si) and thin-film cells. The efficiency of c-Si can reach 25%.
Advantages and Disadvantages of Solar Power
This source of energy is not as expensive as it was before, besides, according to Fraunhofer reports, solar power in sunny regions will be much cheaper than gas, oil or coal. In these several years the growth of solar photovoltaic was significantly raised in Thailand, South Africa, Canada, Australia and moreover the world. Solar power is most accessible, because of the sunlight’s ubiquity.
The use of PV cells is not limited to private buildings, warehouses, etc. For example, The Nellis Air Force Base, located on the northeastern outskirts of Las Vegas gains about 25% of their energy from PV. Furthermore, in 2007, the Sun Power Corporation used their solar photovoltaic installation to generate about 14,000 KW, making this corporation one of the biggest in the U.S. states, but still – 25th in the world
A known problem of solar power generation is its storage: PV cells capture and generate solar energy directly, but there is nothing to capture and hold in molten salt tanks. There was still an option to compress air in some underground caverns during the daytime. Alabama and Germany used this option to save and store the output of solar power plants for daytime peak usage. This cycle is revertible and it can be the opportunity to get electricity during the night by releasing the air in sake of turbine spinning.
Like many other renewable sources of power (wind, geothermal, hydroelectric) solar power is the source, which relies on specific conditions, rare in nature. The places that exactly correspond to the requirements of receiving enough solar power are located far from populated cities, where this power is necessary. There is only one solution – the single place with all suitable conditions is Earth’s orbit (Benduhn, 2009).
The earth’s orbit receives approximately 1.4 GWs for each square meter by solar flow. It is essential, since the solar ray loses about quarter of its value until it gets to the planet’s surface. A fully developed massive satellite, covered with mirrors or any other collection surface, located in geostationary orbit about 35,000 kilometers above the equator will be perfect for solar energy collecting purpose. This satellite will perform the collecting and converting roles, by converting the solar radiation into an electro-magnetic beam. The supreme advantage of this will be ability to direct thousands of solar power Gig watts to any location of our planet.
Another advantage is the inexhaustibility of solar energy. As Johnson (2009) states, the sun has the potential to provide much more energy than our planet needs. This energy has a great future for the economic growth; it also has no any pollution effect on nature and environment. However, it is still too unstable to rely on – any mechanical or technical problems with the space satellite will cause the interruption of the power-dependent services.
The concept of an unlimited source of solar energy is not a dream or the subject of a science fiction film – it is a reality. In past few years, this idea earned financing by the governments of China and Japan, and some companies from U.S. have internationalized to focus efforts on the commercialization of this concept. (Benduhn, 2009)
The official interest of U.S. is occasional. Peter Glaser, who was an American engineer, credited this concept in 1968; a patent for this idea granted to him five years. This research did spark interest up until 1970. This year began the first major phase of research on this subject thanks to NASA’s studies of this concept’s feasibility. There was a proposition about the 5GW concept, but the technology of these times could not do the task economically possible, so researches continued only during the second phase of the solar power researches.
The second phase took place during 1995-1997; NASA got their “fresh look” into this concept with some new technologies. Then, the third phase began – Pentagon’s NSSO publication initiated it. This report was all about the opportunities of solar power use for strategic security. The media outlets were in shock because by concept and intimidated the U.S. government to perform further research. In last few years, many Swiss and American firms took a serious look at this concept, its realization and profits. The fact that both Pentagon and NASA developed interest in this concept signifies that this idea has a promising future.
Japan Space Systems are researching the space solar power systems since 2000. They are have been studying space solar power systems as a future energy resource under the support of The Ministry of Economy, Trade and Industry since 2002. Their studies covered from basic lab testing to the practical usage of power plants. Their development plan consisted of four steps: Technology Demonstration Satellite (100KW), Prototype System (10MW), Pilot System (250MW) and Commercial System (1GW).
The dangers of global warming and limited amounts of natural energetic sources justifies the space solar power systems. During the last 50 years, the global temperature started increasing in high rate. Furthermore, global warming affects energy, water resources; it influences on ecosystems and agriculture. The human’s health quality slowly fades, there is a higher risk to get illness or even die because of extremely high heat; insects are increasing in amounts, people from weakest groups like elderly, poor people and children are the most at risk against the climate related effects. One of the solutions for this problem is to slow down the global warming by not using the natural energy supplies, like gas, oil and wood.
If we replace gas and oil by solar power, we will help our world to stop deforestation and lubricants/combustibles usage. Usage of combustibles and lubricants increases total heat, which leads to the global warming. The solar system is not the only way to save our ecology, but it is also a way to provide cheap and safe electricity to every house. Energy firms raise the awareness of technology by showing its profits, compared to traditional energy sources. For example, The Space Energy firm gives lectures about this technology and works with Japanese and Chinese governments to help them in developing of space solar power concepts.
However, the invention of space solar system can be a threat to the current political systems of our planet. The reason of it – predominating position in the world. Everyone understands that the first country that be the first in development and utilization of clean and renewable energy will take the leading positions in space and aviation, and probably become the world leader. This argument is real, and there will be many debates about the consequences of space-based solar systems.
The solar space stations will have a dual use, like almost every item in our world. As an example GPS satellites, which can be both opportunity for traveler, and guidance system for missiles. If we do not even think about the space solar system stations as a weapon, it can lead to the great loss of the world’s infrastructures, capital investments etc. It will leave thousands of thousands of people without their workplace, since regular electricity “factories” will not be in favor after the developing renewable source of energy. It can lead to destructive consequences: people who lost their works can raise the anti-solar revolutions all over the world.
The usage of space solar power satellite system will help combatants to control and deliver energy for troops anywhere in the world by directing the satellite’s ray to some army receiver stations. This will solve all the logistical problems, connected with army’s energy supplies – there will be any need in transporting fossil fuels. It will also lead to decreasing of casualties, caused of not having enough supplies during the important moment. Still, this feature will be usable not only for some combat actions, but also for doing “good” things – it will be possible to build a stationary receiver complex anywhere – it is cheap and simple. People can use it to support rebels, who opposes the regime army; to help people, trapped in bad situations – cataclysms, natural disasters and something like that.
The satellites power systems are usable for humanitarian purposes - it will help people around the world to get the necessary help they need by directing the power beam anywhere on a short notice. It can support refugee camps and hospitals by giving free electricity; the electricity of these space solar system satellites can help with desalination of water in some far from civilization regions. It will help small nations to overcome the problems of high gas/oil/coal prices. This system can become one of the diplomacy lever – it can help in stopping aggression between non-equal enemies.
Solar Power and Sustainability – Social Perspective
The social factor of sustainable development depends on four major concepts: equity, awareness, participation and social cohesion. Solar power generation is influential mostly regarding participation. Reports show that the establishment of solar power plants positively influence communities, given that they propel job availability.
Communities established near conventional fossil fuel power generation plants tend to suffer from air pollution. Conversely, where solar plants are located, residents enjoy fresher air and in consequence, present less medical issues, improved overall health, reduced breathing difficulties, etc. Moreover, some communities, which due to geographical limitations do not have access to large power grids, can use solar energy-based power generation, which promotes educational and social opportunities.
Solar Power and Sustainability – Environmental Perspective
The Brundtland Commission defines sustainable development as “the development that meets the needs of the present without compromising the ability of future generations to meet their own needs”. In consideration, the environment is one of the pillars of sustainability. It is widely recognized that the burning of fossil fuels for power generation is one of the main causes of global warming, given the extensive emissions of greenhouse gases this activity generates. Solar power, on the contrary, is an alternative source of electricity that does not generate emissions of this type, and is therefore a much more environmentally friendly option.
A study conducted by Nelson, Gambhir and Ekins-Daukes (2014) indicates that in the UK the carbon emission intensity of CSP systems ranges from 20 to 50 gCO2/kWh, photovoltaic cells systems’ ranges from 15 to 38 gCO2/kWh. Both figures are considerably lower than the carbon emission intensity of fossil fuel power generation: 500 gCO2/kWh.
Solar power generation raises ecological concerns regarding land use and degradation and habitat loss for fauna and flora species. However, these claims fail to consider that these plants are placed in deserted areas with soil unsuitable for cultivating crops or raising livestock, as explained by Tsoutsos, Frantzeskaki and Gekas (2015).
Solar Power and Sustainability – Economic Perspective
The first commercially available technologies for solar power generation were too expensive for the average person, and therefore their widespread adoption was unpractical. However, these costs considerably decreased in recent years. For instance, Nunez indicates that the average cost of residential solar power systems has is now approximately 30% of the price in 2008. Conversely, electric billing for conventional energy sources have increased or remained the same. As a result, solar power generation has become a much more attractive option, and has quickly increased from generating 0.5% of the worldwide electricity in 2012 to over 1% in 2015 (Fondation Energies Pour Le monde, 2013). A significant factor for this increase is attributed to the widespread use of residential solar energy use, as well as businesses that have decided to install solar panels on rooftops to cover part of their energy demand.
Similarly, Nelson (2011) indicates that the cost of energy (cost per watts generated) of Concentrating Solar Power Systems was approximately $125-225/MWh, but predicted future costs are estimated to be $43-62/MWh for trough plants and $35-55/MWh for tower plants (p. 332). These costs are competitive with those from energy generated through fossil fuels. Utility companies, however, do not seem to benefit from this technology. Though the number of homes with solar panels installed has increased, they are still connected to power grids to use as a secondary source, as a backup for times when solar system output is reduced or inexistent, such as during nighttime or system failure. Therefore, utility companies face the issue of assuming the fixed costs of grid maintenance with lower revenues, as solar-power users do not consume as much traditional energy and thus have lower bills.
Solar Power and Sustainability – Political Perspective
The successful transition towards renewable energy requires the establishment of certain policies and strategies to provide incentives for the development of solar power generation systems, as well as to impose penalties and educate the industry. Nelson (2011) contends that incentives are mainly in the form of tax breaks, subsidies, mandates and regulations to promote renewable projects, while fines are higher taxes and strict regulations (p. 300). Likewise, the education aspect involves the increase of public awareness regarding the long-term cost-benefits of renewable energy.
Future Developments and Research
Research on solar power generation mainly focuses on increasing system efficiency and decreasing manufacturing costs. Among these studies is one conducted by Stupca, Alsalhi, Al Saud, Almuhanna and Nayfeh (2007), who discovered that coating cells with silica nanoparticles increases their efficiency by improving the absorption of ultraviolet rays. Moreover, the heat transfer fluid of CSP systems is under constant study, as research intends to select the material that can achieve the highest temperature while maintaining its stability, in order to replace molten salt.
As explained in previous section of the paper, the development of space solar power technology to collect sunlight hitting the earth’s orbit is also a major focus in this field.
Conclusion
I believe the development of solar power systems in space will be a great achievement that will solve many problems of humanity. Surely, it has some disadvantages, but the advantages outweigh them. Besides, human creativity should suffice to develop solutions to these potential issues.
Setting space solar power satellites an important step for humanity in exploring space. Not conquering, but exploring – since there is a belief that humanity is not the only race in our universe, so we cannot just “conquer” the unknown. This technology must be developed as soon as possible, as it would open myriads of opportunities for scientists. The space solar power itself is not dangerous, but it can be if it lands in the wrong hands.
References
Aarre, M. (2013, August 14). The History of Solar Energy. Retrieved from Energy Informative: http://energyinformative.org/the-history-of-solar-energy-timeline/
Benduhn, T. (2009). Solar power. Weekly Reader Pub.
Chu, S., & Majumdar, A. (2012). Opportunities and challenges for a sustainable energy future. Nature - International Weekly Journal of Science, pp. 294-303.
Fondation Energies Pour Le Monde. (2013). Electricity Production in the World: General Forecasts. Observ'ER.
Johnson, G. (2009). Plugging Into the Sun. Retrieved April 10, 2016, from National Geographic Magazine: http://ngm.nationalgeographic.com/print/2009/09/solar/johnson-text
Machinda, G., Chowdhury, S., Arscott, R., & Kibaara, S. (2011). Concentrating Solar Thermal Power Technologies: A Review. In IEEE (Ed.), 2011 Annual IEEE India Conference, (pp. 1-6). Hyderabad.
Nelson, V. (2011). Introduction to Renewable Energy (Energy and the Environment). Boca Raton: CRC Press Taylor & Francis Group.
Nunez, C. (2015, October 2). Solar Energy Sees Eye-Popping Price Drops. Retrieved April 12, 2016, from National Geographic.
Penick, T., & Louk, B. (1998). Photovoltaic Power Generation.
Shahan, Z. (2012, March 21). A Brief History of Everything Solar. Retrieved from Clean Technica: http://cleantechnica.com/2012/03/21/history-of-solar/
Smith, C. (1995, July). History of Solar Energy. Retrieved from Solar Energy: http://solarenergy.com/info-history
Stupca, M., Alsalhi, M., Al Saud, T., Almuhanna, A., & Nayfeh, M. (2007). Enhancement of polycrystalline silicon solar cells using ultrathin films of silicon nanoparticle. Applied Physics Letters.
Tsoutsos, T., Frantzeskaki, N., & Gekas, V. (2005). Environmental impacts from the solar energy technologies. ELSEVIER Journal on Energy Policy, 289-296.
Wara, M. (2014). California's energy and climate policy: A ful plate, but perhaps not a model policy. Bulletin of the Atomic Scientists, pp. 26-34.
Wood, L. (2012). Projecting power: The security implications of space-based solar power. Bulletin of the Atomic Scientists, pp. 70-78.
