Introduction
I began the applied physics course by focusing on electric generators and electromagnetic induction. When the course went forward I got more interested in renewable energy sources and first of all, in wind power, which also relates to my current topic solar power, because both of them are at least partly caused by the sun. Wind power is caused the motion of the winds, like everyone knows, and winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the globe’s surface and rotation of the globe, whereas solar power is direct implication of the conversion of sun light to electric or heat energy.
Solar power is converted to energy via photovoltaic effect (PV) or concentrated solar power (CSP). The potential of solar energy is huge, as humanity consumes energy in a year, about the same as solar energy is absorbed by the earth's surface and the atmosphere in one hour. However, only 21 percent of radiation energy of sun light can be converted as electric energy by using photovoltaic effect (PV). Accordingly 25-35 percent of the radiation energy of the sun can be converted as heat energy by using concentrated solar power (CSP).
Two ways to convert sun light into solar power
Photovoltaics and PV system
A solar cell or photovoltaic cell (PV) rely on the principle of the photoelectric effect: the ability of matter to emit electrons when a light is shone on it. Photoelectric effect is directly relative to photovoltaic effect, which is used to convert sun light to energy in the solar cell. Photovoltaic effect is the creation of voltage or electric current in a material upon exposure to light.
The array of a photovoltaic power system, or PV system, produces direct current (DC) power which fluctuates with the sunlight's intensity. For practical use this usually requires conversion to certain desired voltages or alternating current (AC), through the use of inverters. Multiple solar cells are connected inside modules. Modules are wired together to form arrays, then tied to an inverter, which produces power at the desired voltage, and for AC, the desired frequency.
Picture 1: Photovoltaic power system
Many residential PV systems are connected to the grid wherever available, especially in developed countries with large markets. In these grid-connected PV systems, use of energy storage is optional. In certain applications such as satellites, lighthouses, or in developing countries, batteries or additional power generators are often added as back-ups. Such stand-alone power systems permit operations at night and at other times of limited sunlight.
Concentrated solar power (CSP)
Concentrated Solar Power (CSP) systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. The concentrated heat is then used as a heat source for a conventional power plant. Lot of different concentrating technologies exists but in all of these CSP systems a working fluid (for example steam in a steam engine or air in a hot air engine) is heated by the concentrated sunlight, and is then used for power generation or energy storage. The most used technologies for concentrated solar power are the parabolic trough, the compact linear Fresnel reflector, the Stirling dish and the solar power tower.
Let’s take a parabolic trough as an example of concentrated solar power technology. A parabolic trough consists of a linear parabolic reflector that concentrates light onto a receiver positioned along the reflector's focal line. The receiver is a tube positioned right above the middle of the parabolic mirror and is filled with a working fluid. The reflector is made to follow the sun during daylight hours by tracking along a single axis.
Picture 2: Parabolic trough explained Picture 3: Parabolic trough solar power system
Summary
Solar energy is a form of renewable energy, and its production produces waste only as manufacturing and disposing phase of the solar units. Solar power has long been quite expensive, because of the price of solar cells, but some studies suggest that production of solar power is going to fall over the next ten years to the level of production of the fossil fuels.
Finally few words about the markets of the solar power and solar power’s relationship to another energy forms. In 2012 Germany was the number one country in the world of producing the solar power, but now-a-days China, Japan and US has taken the top 3 of global markets. China has a global market with around 11.3 GW connected to the grid in 2013, while Germany was the top European market with 3.3 GW. But still, Germany covers only 3% of the country’s total electricity consumption with a solar power. However, market analysts believe this number will increase to 25% before 2050. From a picture below can be seen the whole world energy consumption by source in 2010: solar power represent a minimal piece of it, while the total size of renewable energy sources was 16,7%.
Picture 4: Total world energy consumption by source 2010
Reference
How do solar cells work?| Explore | physics.org. 2014. How do solar cells work?| Explore | physics.org. [ONLINE] Available at:http://www.physics.org/article-questions.asp?id=51. [Accessed 03 December 2014
Photoelectric effect (physics) -- Encyclopedia Britannica. 2014. photoelectric effect (physics) -- Encyclopedia Britannica. [ONLINE] Available at:http://global.britannica.com/EBchecked/topic/457841/photoelectric-effect. [Accessed 03 December 2014].
Solar power - Wikipedia, the free encyclopedia. 2014. Solar power - Wikipedia, the free encyclopedia. [ONLINE] Available at: http://en.wikipedia.org/wiki/Solar_power. [Accessed 16 December 2014].
Aurinkoenergia – Wikipedia. 2014. Aurinkoenergia – Wikipedia. [ONLINE] Available at: http://fi.wikipedia.org/wiki/Aurinkoenergia. [Accessed 16 December 2014]
Picture 1: Photovoltaic power system - Solar power - Wikipedia, the free encyclopedia. 2014. Solar power - Wikipedia, the free encyclopedia. [ONLINE] Available at: http://en.wikipedia.org/wiki/Solar_power#mediaviewer/File:PV-system-schematics-residential-Eng.png. [Accessed 16 December 2014]
Picture 2 & 3: Parabolic Trough Reflector for Solar Thermal System. 2014. Parabolic Trough Reflector for Solar Thermal System. [ONLINE] Available at: http://www.alternative-energy-tutorials.com/solar-hot-water/parabolic-trough-reflector.html. [Accessed 16 December 2014]
Picture 4: Renewable energy - Wikipedia, the free encyclopedia. 2014. Renewable energy - Wikipedia, the free encyclopedia. [ONLINE] Available at: http://en.wikipedia.org/wiki/Renewable_energy#mediaviewer/File:Total_World_Energy_Consumption_by_Source_2010.png. [Accessed 16 December 2014].
