Photovoltaics (PV) is a technology that converts sun light into electricity. Photovoltaics refer to the operating mode of a photodiode in which current through the device is entirely due to the transduced light energy. Photovoltaics is most commonly known as a method for generating solar power by using solar cells packaged in Photovoltaic modules. Generally these individual cells are electrically connected in multiples as solar arrays to convert energy from the sun into electrical energy. Solar cells are made up of semiconductor materials which have the ability, on sub-atomic level, to absorb photons (particles - or quanta - of light) thus increasing energy of electrons in valcence band and moving them to conduction band, hence creating evectricity on macroscopic scale. Today, these materials include: Crystalline Silicon, Cadmium Telluride (CdTe), Copper Indium Gallium Selenium (CIGS), amorphous Silicone (Si) and continuous printing organic materials. Due to the global need for energy and the inability of common sources of energy (oil and gas) to keep up with demand and because of negative trade-offs for other sources such as coal and nuclear many new sources of energy are being explored. Solar energy has significant promise in that it does not lead to emition of green house gasses, it is most efficient during the middle of the day when demand is highest and a solar cell can operate relatively maintenance-free for well over 30 years. Solar cells are durable. One of the early applications was power generation on satellites. The cost of solar cells is continually decreasing and the efficiency increasing. Additionally, solar electric generation has the highest power density (global mean of 170W/m2) among renewable energy generation sources. There is an abundance of solar energy available. There are 89 petawatts of sunlight reaching the earth’s surface which is almost 6,000 times the 15 terawatts of average power consumed by globally. A 100 mile by 100 mile solar array located in southern Nevada, for example, could provide all the power needs of the United States.
The key down sides to PV include the cost, ranging from $5.00 - $8.00 per watt depending on the application, and the fact that when the sun is not shinning, very little to no electricity is generated. Therefore solar PV needs either a battery storage system or more commonly it is tied into an existing electrical grid.
Incentives can help lower the cost of PV installations (see our home page for details). The purpose of incentives is to grow the industry, even where the cost of PV is significantly above grid parity, to allow it to achieve the economies of scale needed to reach grid parity. The policies are implemented to promote national energy independence, high-tech job creation and reduction of CO2 emissions. Three incentive mechanisms are used: Investment subsidies – a refund for part of the cost of installation of system, Feed-in Tariffs/Net metering – the utility buys PV electricity from the producer under a multi-year contract at a guaranteed rate, and renewable energy credits. Nearly all areas of the US have one or more of these incentives to encourage PV installations.
Building-Integrated Photovoltaics (BIPV) is the term used when PV is incorporated into new domestic and industrial buildings as a principal or ancillary source of electrical power. Typically an array is incorporated into the roof or walls of a building. Arrays can also be retrofitted into existing buildings. In this case they are usually fitted on top of the existing roof structure.
The technology needed for the composition as well as the production of PV cells is rapidly changing. The cost/performance ratio is continually improving such that the federal government has set a goal of being at grid parity (cost to produce electricity using Photovoltaic is equal to the cost for utilities to produce electricity from other sources such as coal and gas) by the year 2015.
Globally for 2010, there was a significant growth in the number of PV systems installed - According to iSuppli, at least 15GW of PV systems were installed globally in 2010, compared to 7.2GW in 2009.Many seized the opportunity and launched new solar start-ups at a rate reminiscent of the burgeoning computer industry of the 1980s.
Following a strong year in 2010 that will see around 1 GW of installations in North America, 2011 should bring over 2 GW of new installations - as well as a host of new options for developers and project owners looking to reduce the levelized cost of solar energy,
The following is a solar irradiance map of the US and other countries, provided by SEIA
According to an independent study by GTM Research, U.S. solar installations created $3.6 billion in direct value to the global economy in 2009. Of that, nearly 74 percent, or $2.6 billion, directly benefited the U.S. economy. Eighty-one percent of the domestic value created in the solar industry came from the photovoltaic (PV) sector, with concentrating solar power (CSP) and solar heating and cooling (SHC) making up the remaining 19 percent. The U.S. was a net exporter of solar energy products in 2009, led by the $1.1 billion in exports of polysilicon, the primary feedstock in most PV cells. For PV, China and Mexico contributed most to imports, while Germany, Japan and China were the most prominent export destinations.
Feed in tariffs (FiTs) vary widely from country to country and state to state. A person contemplating a PV system should choose a well qualified, certified installer who is familiar with the FiTs in your area.
Energy storage and batteries
Batteries for the solar industry are in great demand, and the best technology for solar is hotly debated. There is an abundance of research, development and testing of utility scale and other batteries for renewable energy storage.
Inverters and microinverters
According to iSuppli, high-power inverters of 500kW or more that are designed for utility-scale solar will enjoy a 61% compound annual growth rate on a MW basis over the next five years.
Utility scale power
Massive solar power plants in Australia, Spain, Italy and the US made the news in 2010—demonstrating different solar technologies as well as challenges surrounding distribution, land-use, funding, politics and more.