What are the different methods of solar power generation?
General Reference (not clearly pro or con)
The National Resources Defense Council (NRDC), in the "Issues: Oil & Energy" section of its website www.nrdc.org (accessed Oct. 14, 2008), wrote:
"The sun's energy can be actively captured to generate electricity or passively harnessed to heat water or buildings.
Solar, or photovoltaic cells, convert sunlight directly into electricity. They're usually made primarily of silicon, the same material used in computer semiconductor chips. When sunlight hits a solar cell, the energy knocks electrons free of their atoms, allowing them to flow through the material, resulting in direct current (DC) electricity.
Concentration systems use mirrors to focus the sun's energy. The concentrated sunlight heats water or a heat-transferring fluid to generate steam. This steam is used just like in a conventional power plant -- to spin a turbine and generate electricity.
Collectors use heat-absorbing material to harness sunlight for heating water or buildings.
Windows, sunrooms and skylights allow the sun to heat and light buildings."
Gil Knier, a scientist in the Science@NASA program, in an article titled "How Do Photovoltaics Work?" published on the NASA website www.science.nasa.gov, in a section titled "The Edge of Sunshine" (accessed Oct. 14, 2008), wrote:
"Photovoltaics is the direct conversion of light into electricity at the atomic level. Some materials exhibit a property known as the photoelectric effect that causes them to absorb photons of light and release electrons. When these free electrons are captured, an electric current results that can be used as electricity...
... A number of solar cells electrically connected to each other and mounted in a support structure or frame is called a photovoltaic module. Modules are designed to supply electricity at a certain voltage, such as a common 12 volts system. The current produced is directly dependent on how much light strikes the module.
Multiple modules can be wired together to form an array. In general, the larger the area of a module or array, the more electricity that will be produced..."
AlternateEnergySources.com, an informational website about solar energy, in a section on its website titled, "All The Basics On Solar Power That You Need — How Does Solar Energy Work?" (accessed Oct. 14, 2008), wrote:
"The solar thermal method uses energy from the sun directly to generate heat. Solar panels can be used to collect heat from the sun to capture its heat and transfer it for water and space heating in buildings. Commonly such panels are positioned to maximise absorption of heat from the sun throughout the day and contain tubing through which water circulates. This tubing is known as solar thermal collectors There is also an indirect method where not water but a non-toxic anti-freeze liquid is used. The sun warms this liquid which in turn transfers this heat to water held in a tank. Passive thermal building design is as simple as designing to maximise the sun’s use."
DiscoverPerfectEnergy.com, an online resource for alternative energy projects, in a section of the website titled "Solar Power Basics - So exactly what is Solar Energy?" (accessed Oct. 14, 2008), wrote:
"1. Thermal Energy There are a wide array of products on the market that utilize thermal energy. The products most often used are called solar thermal collectors and can be mounted on the roof of a building or in some other sunny location. By far, the most common (and one of the most cost-effective) solar thermal collectors is a solar water heater.
A solar water heater system is usually comprised of three parts; a storage tank, a 'working' fluid system and solar collectors. The working fluid flows through the solar collector (either actively pumped or set up in a way that it can passively flow) in which it collects the thermal energy and carries it back into the water storage tank. In some cases the working fluid is the actual hot water from the tank, but more often it is an independent loop (of either water or water and anti-freeze) that collects the heat and carries to it a heat exchanger inside the storage tank. The heat exchanger transfers the heat from the working fluid into the water within the storage tank and the hot water is ready for use when needed.
2. Light Energy Capturing light energy from the sun can vary depending on whether you goal is to capture light or create electricity. If light is the goal, then skylights or light-pipes are a popular method. Skylights allow the sun's light to enter through specialized windows (typically located in the roof) providing natural lighting to a building. One strong consideration that needs to be taken into account when considering skylights is the amount of thermal or heat enery that may be lost due to the skylight.
Another popular alternative in capturing natural light are light-pipes. A Light-pipe is a round tube lined with extremely reflective materials that guides the light rays from an entrance point (the roof or an outer wall) into the building. A collector at the entrance point directs as much sunlight as possible down the tube and a diffuser spreads the natural light through-out the inner room. Light-pipes minimize the heat energy lost and are also extremely flexiable in design and implementation, allowing them to extend past an attic or twist and turn around other obstructions that may be in the way.
By far, the main-stay of the solar energy industry is solar panels or Photovoltaic (PV) technology. Solar cells, usually made from silicon, are electrically connected together and marketed as photovoltaic modules or 'solar panels'.
The basic science behind solar energy is that photons from the sunlight knock the electrons, within the silicon solar cell, into a higher state of energy, therefore, creating electricity. The electricity created by a solar panel can be used immediately to power a building, or it can be stored in a battery for later use. Solar panels are very versatile and can be mounted in a variety of sizes and applications. PV technology is currently being integrated into building materials such as PV shingles and opaque glass PV facades."