| A photovoltaic module or photovoltaic panel is a | | | | New designs of module include concentrator |
| packaged interconnected assembly of photovoltaic | | | | modules in which the light is concentrated by an |
| cells, also known as solar cells. The photovoltaic | | | | array of lenses or mirrors onto an array of small |
| module, known more commonly as the solar | | | | cells. This allows the use of cells with a very |
| panel, is then used as a component in a larger | | | | high-cost per unit area (such as gallium arsenide) in |
| photovoltaic system to offer electricity for | | | | a cost-competitive way. |
| commercial and residential applications. | | | | Depending on construction the photovoltaic can |
| Because a single photovoltaic module can only | | | | cover a range of frequencies of light and can |
| produce a limited amount of power, many | | | | produce electricity from them, but sometimes |
| installations contain several modules or panels and | | | | cannot cover the entire solar spectrum |
| this is known as a photovoltaic array. A | | | | (specifically, ultraviolet, infrared and low or diffused |
| photovoltaic installation typically includes an array | | | | light). Hence much of incident sunlight energy is |
| of photovoltaic modules or panels, an inverter, | | | | wasted when used for solar panels, although they |
| batteries and interconnection wiring. | | | | can give far higher efficiencies if illuminated with |
| Photovoltaic systems are used for either on- or | | | | monochromatic light. Another design concept is to |
| off-grid applications, and for solar panels on | | | | split the light into different wavelength ranges and |
| spacecraft | | | | direct the beams onto different cells tuned to the |
| Solar panels use light energy (photons) from the | | | | appropriate wavelength ranges. This is projected |
| sun to generate electricity through the | | | | to raise efficiency by 50%. Also, the use of |
| photovoltaic effect. The mainstreams of modules | | | | infrared photovoltaic cells can increase the |
| use wafer-based crystalline silicon cells or a | | | | efficiencies, producing power at night. |
| thin-film cell based on cadmium telluride or silicon. | | | | Sunlight conversion rates can vary from 5-18% in |
| Crystalline silicon, which is commonly used in the | | | | commercial production, which can be lower than |
| wafer form in photovoltaic (PV) modules, is | | | | cell conversion. |
| derived from silicon, a commonly used | | | | A group of researchers at MIT has recently |
| semi-conductor. | | | | developed a process to improve the efficiency of |
| In order to use the cells in practical applications, | | | | luminescent solar concentrator technology, which |
| they must be: | | | | redirects light along a translucent material to |
| • connected electrically to one another and to | | | | PV-modules located along its edge. The |
| the rest of the system. | | | | researchers have suggested that efficiency may |
| •Protected from mechanical damage during | | | | be improved by a factor of 10 over the old |
| manufacture, transport, installation and use (in | | | | design in as little as three years (it has been |
| particular against hail impact, wind and snow loads). | | | | estimated that this will provide a conversion rate |
| This is especially important for wafer-based silicon | | | | of 30%). Three of the researchers involved have |
| cells which are brittle. | | | | now started their own company, called Covalent |
| •Protected from moisture, which corrodes | | | | Solar, to manufacture and sell their innovation in |
| metal contacts and interconnects, (and for | | | | PV-modules. |
| thin-film cells the transparent conductive oxide | | | | The current market leader in efficient solar |
| layer) thus decreasing performance and lifetime. | | | | energy modules is Sun Power, whose solar panels |
| Most modules are usually rigid, but there are | | | | have a conversion ratio of 19.3%. However, a |
| some flexible modules available, based on thin-film | | | | whole range of other companies (Holocene, |
| cells. | | | | Gamma Solar, Nan Horizons) are emerging which |
| Electrical connections are made in series to | | | | are also offering new innovations in photovoltaic |
| achieve a desired output voltage and/or in parallel | | | | modules, with a conversion ratio of around 18%. |
| to provide a desired amount of current source | | | | These new innovations include power generation |
| capability. | | | | on the front and back sides and increased |
| Diodes are included to avoid overheating of cells in | | | | outputs; however, most of these companies have |
| case of partial shading. Since cell heating reduces | | | | not yet produced working systems from their |
| the operating efficiency it is desirable to minimize | | | | design plans, and are mostly still actively improving |
| the heating. Very few modules incorporate any | | | | the technology. As of August 26, 2009 a world |
| design features to decrease temperature; | | | | record efficiency level of 41.6% has been |
| however installers try to provide good ventilation | | | | reached. |
| behind the module. | | | | |