Solar energy is derived from the light and radiant heat from the sun, an abundant source of renewable energy that can be captured and employed in many ways.

Since ancient times, solar energy has been harnessed by humans using a range of technologies.  Current solar technologies include photovoltaic systems (PV), concentrating solar power systems (CSP), passive solar heating and daylighting, solar hot water, solar process heat, and solar space heating and cooling.

Solar power can be used in both large-scale industrial and commercial applications and in smaller systems for the residential sector. Businesses and industry can diversify their energy sources, improve efficiency, and save money by choosing solar technologies for heating and cooling, industrial processes, electricity, and water heating.  Public utilities and power plants are also capturing the sun's abundant energy to deliver cleaner energy to their customers. For example, concentrating solar power plants (CSP), first developed in the 1980s, use mirrors to reflect and focus sunlight onto receivers that collect and convert solar energy into heat and electricity.  This allows large-scale power plants to save consumers the hassle and capital investment in household solar technology systems.

Two Types: Passive and Active

Solar technologies are characterized as either passive or active depending on how they capture, convert and distribute the sun’s heat and light. Active solar techniques use photovoltaic panels, pumps, and fans to convert sunlight into useable energy, while passive solar techniques use materials with favorable thermal properties, employ design techniques that naturally circulate air, and orient building placement to maximize (or minimize) the sun’s heat and light.

Solar Energy Potential

Solar energy has massive potential to power our modern society. The total solar energy absorbed by Earth's atmosphere, oceans and land mass is approximately 3,850,000 exajoules (EJ) per year. To put that in perspective, the energy from sunlight striking the Earth for just 40 minutes is equivalent to global energy consumption for an entire year.  The amount of solar energy reaching the Earth’s surface is so vast that in one year it is about twice as much energy as will ever be obtained from all of the nonrenewable resources of coal, oil, natural gas, and uranium for nuclear plants, combined.

The popular magazine Scientific American reported in 2007 that “a massive switch from coal, oil, natural gas and nuclear power plants to solar power plants could supply 69 percent of the U.S.’s electricity and 35 percent of its total energy by 2050” with a sizeable, but achievable investment.

Development, Deployment and Economics

Leading industry analysts and solar company executives predict that solar power will reach equal cost competitiveness with fossil fuels for electricity generation in North America and elsewhere within the next few years, possibly as soon as 2010.

The likelihood that tougher regulations on global warming emissions from the energy sector will be implemented by individual governments and under the successor to the global Kyoto Protocol (expected at the end of 2009) will make solar and other renewables more attractive to investors, as prices of electricity produced by polluting fossil fuel sources will rise in response.

Photovoltaic (PV) panels currently represent 90 percent of sales in the solar market. While solar PV panels are easy to install, building them is currently expensive because of tight supplies of silicon, their costliest component. Most industry analysts expect the constraint on silicon supplies to end within two years, driving down the cost of making PV panels.

However, emerging technologies such as thin-film solar panels made from cadmium telluride, which require much less silicon, are expected to challenge the market domination of PV panels. Nobody knows for sure which type of solar panel technology will dominate the market in the coming years, making the solar power industry an exciting sector to track.

Germany, Japan and Spain currently dominate the solar power market, although the fourth place United States may overtake Germany as the world’s biggest solar market in the next few years if investments and regulations converge to propel it to the top.  China is also emerging as a major solar power interest, with growing demand for clean energy supplies and a competitive cadre of Chinese solar panel manufacturers vying for increased market share of the fast-growing demand for solar panels worldwide.  France, Italy and South Korea are also experiencing rapid growth in solar power due to various incentive programs and local market conditions.