Solar Power

• October 1, 2011

Global Solar Intensity Potential Map

Solar intensity (insolation) by region via: altE

Solar is inevitable not because of carbon, but because it is the most effective way to reach the un-electrified poor.”                          – Jigar Shah, Carbon War Room

According to data from the U.S. National Renewable Energy Laboratory, enough sunlight falls on the earth to generate 177 million gigawatt-hours of electricity a year using current solar technologies (assuming 50% development of available land). That is about 10 times the amount of electricity used by the entirety of human civilization in one year. What’s more, there is an explosion of innovation taking place in the solar technology sector that could double or even triple the output of a typical solar installations, making solar power significantly cheaper than coal and gas-fired power plants.

Solar power offers numerous advantages over other methods of power generation (source: NRDC):

  • It relies on a free fuel — sunlight.  No mining or drilling and it is infinitely renewable.
  • Unlike conventional fossil fuel and nuclear power, solar power produces no pollution or CO2 emissions.
  • With no moving parts, solar panels are silent, easy to operate and rarely need maintenance.
  • Solar power can slash utility bills for both residential and commercial consumers.
  • PV’s strengthen the electrical grid, helping utilities avoid blackouts during peak daylight times.
  • Solar manufacturing is a booming industry, offering recession-proof employment opportunities.

There are three types of solar power generation — Photovoltaic (PV), Concentrated Solar Power (CSP) and Solar Thermal – which have a variety of applications.

Solar Photovoltaics

Solar PV Panel

Creative Commons: Mike Baker, 2009

The best known form of solar power generation, Solar PV panels convert sunlight directly into electricity. Most photovoltaic cells are made primarily of silicon, the material used in computer semiconductor chips, and arranged on rectangular panels. When sunlight hits a cell, the energy knocks electrons free of their atoms, allowing them to flow through the material. The resulting DC (direct current) electricity is then sent to a power inverter for conversion to AC (alternating current). Thin film PV is much less efficient at converting photons to electricity but is far cheaper to manufacture and, with the advent of translucent films, can be integrated into building window systems. Germany has become one of the biggest consumers of solar PV electricity and is projecting 25% solar power generation by 2050.

Concentrated Solar Power

Solar CSP

Creative Commons: Siemens

CSP is an industrial-scale technology for producing electricity by using mirrors — usually arranged in a series of long, parabolic troughs, a large round dish, or a circle surrounding a “power tower” — to focus the sun’s reflected rays on a heat-collecting element. The concentrated sunlight heats water or a heat-transferring fluid such as molten salt to generate steam, which is then used conventionally to spin turbines and generate electricity. Investments in CSP have grown dramatically as many see the potential for “grid parity” — solar power that is as cheap or cheaper than coal-fired power generation.

Solar Thermal

Solar Thermal Collectors

Creative Commons: Ra Boe

Solar Thermal Collectors collect the sun’s heat through heat-absorbing panels and a series of attached circulation tubes, replacing the natural gas or oil fuels typically used for residential and commercial hot water heating. Some wall-mounted systems collect heat and radiate (or blow) the heat into the building, again offsetting traditional fossil fuels for use in space heating. Space heating and water accounts for more than 50% of all residential and commercial energy use, so the application of inexpensive solar heating systems can greatly reduce our reliance on fossil fuels.

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Despite the many advantages of solar power, countries like the United States have been slower to adopt the technology. With some of the best solar resources in the world, the U.S. is in danger of missing one of the greatest opportunities in history to become a leader in the clean energy revolution:

A decade ago China made 1% of the world’s solar panels. Today it makes nearly half of them. The $15 billion worth of solar panels China exported last year was more valuable than America’s corn, beef, and chicken exports combined. China is no longer coming. They are here. They ate our lunch, and they are moving on to our dinner. — U.S. Rep. Edward J. Markey

Solar Quick Facts

  • Solar photovoltaic (PV) cell manufacturers produced a record 10,700MW of PV cells globally in 2009—an impressive 51% increase from the previous year. [Earth Policy]
  • By the end of 2009, nearly 23,000MW of PV had been installed worldwide, enough to power 4.6 million US homes. [Earth Policy]
  • More than 100,000 rural households have installed solar home systems in Bangladesh, where 70% of people don’t have access to electricity. The program, by non-profit Grameen Shakti, is the fastest growing in the world and expects to install 1 million systems by 2015. [International Labor Organization]
  • Kenya is one of the global leaders in solar in the developing world, with over 200,000 PV systems sold in Kenya since the mid 1980’s, three quarters to private households. [Humboldt]
  • Californians installed 194 megawatts of solar in 2010, 47 percent more than they installed in 2009. [Grist]
  • California now has nearly 1 gigawatt of solar spread across almost 10,000 sites. [Grist]
  • If solar panels were installed on the 2/3 of buildings in NYC that are suitable, around 50% of the city’s electricity needs could be provided for when the sun is shining. [TreeHugger]
  • Prices of solar panels are falling so fast that by 2013 they will be half of what they cost in 2009. [Guardian UK]CSP is being widely commercialized, with about 1.17 gigawatts (GW) of CSP plants online as of 2011. [Renewable Energy World]
  • About 17.54 GW of CSP projects are under development worldwide, and the United States leads with about 8.67 GW. [Renewable Energy World]
  • CSP Stations may be economically competitive with fossil fuels. [Robert Glennon]
  • Concentrated solar power could account for up to 25% of the world’s energy needs by 2050. [Guardian UK]
  • Nathaniel Bullard, a solar analyst at Bloomberg New Energy Finance, has calculated that the cost of electricity at the Ivanpah Solar Power Facility, a project under construction in Southern California, will be lower than photovoltaic power and about the same as natural gas. [Robert Glennon]
Concentrating Solar power tower DOE

Creative Commons: U.S. Dept. of Energy, 2010


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