Solar Energy

Humanity has been making use of solar energy since our beginnings. Plants are essential to the food supply and without light photosynthesis couldn’t take place. Taking a hint from Nature we have started to tap solar energy for other uses like generating electricity, heating, and purifying water.

Solar Cell Materials

Pure monocrystalline silicon wafer ready for production. Image by Saperaud.

Pure monocrystalline silicon wafer ready for production. Image by Stahlkocher. License: GNU FDL

Advances in solar cell technology and materials are allowing us to reach increasingly higher efficiency when converting solar energy to electricity. Some of the latest solar cells to be tested in labs, like the three junction concentrators, can get as high as 42% efficiency.

Solar cells are constructed of various materials and in a variety of ways. Mono and polycrystalline silicone are the most popular. These are the silicone panels you likely imagine when thinking of solar panels. Although inflexible and inefficient when compared to emerging technology the abundance of silicone makes these popular, inexpensive, and more environmentally friendly.

Amorphous silicone solar cells provide a flexible layer allowing for thin film photovoltaics. Cadmium Telluride solar cells are also thin film photovoltaics that are cheaper to produce and more efficient than amorphous silicone but the components, specifically tellurium, are rarer limiting production. Another emerging thin film solar cell is constructed of Copper, Indium, Gallium, and Selenide. Known as CIGS solar cells these have the highest efficiency among thin film cells but manufacturing costs are prohibitively high for mass production.

Gallium arsenide multijunction solar cells on Mars rover. Image by Rtphokie.

Gallium arsenide multijunction solar cells on Mars rover. Image by Rtphokie. License: CC BY-SA 3.0

Gallium Arsenide multijunction solar cells have the highest efficiency (42% as of 2011) of any solar cell but are quite expensive. Currently this technology and solar cell material is only used in specific situations like the Mars Rover where the cost is justified.

Other emerging photovoltaic technology includes Dye Sensitized Solar Cells which use a layer of TiO2 coated with photosensitive dye and organic solar cells which rely on solely on organic semiconductors to produce an extremely environmentally friendly solar cell where end of life disposal isn’t an issue. Both of these currently have very low efficiency rates but are also new technology that hasn’t had the time to mature.

Environmental Impact of Solar Power

Currently solar panels are among the most environmentally friendly power sources. Silicone is the most abundant resource on Earth behind Oxygen making it easy to obtain. It is also safe to work with (with the exception of silicone dust) and easy to dispose.

Manufacturing does make use of certain gases like nitrogen trifluoride which can be thousands of times more powerful than carbon dioxide as greenhouse gases. Luckily these gases are used and recaptured during production allowing only minuscule amounts to escape into the atmosphere when compared to coal and other atmospheric pollutants.

When solar cells reach their end of life proper disposal and recycling is key to ensuring that solar panels live up to their “green” reputation. More than just silicone is used to produce solar cells and this other electronic waste doesn’t sit so well in landfills. Many manufacturers are including extended producer responsibility with their products which means they’ll take the panels back at the end of their life and recycle them at no cost to the consumer.

Another potential pitfall towards solar panels being environmentally friendly is production in areas with lax environmental protection laws. There are many potentially hazardous chemicals used during manufacturing and in some countries proper disposal of those chemicals might be ignored in favor of dumping on the side of the road. In these situations “green” solar panels sold in environmentally conscious countries may be produced overseas using very “non-green” methods that alter the net environmental impact of the technology.

Uses of Solar Power

Daylighting oculus at the top of the Pantheon in Rome. Image by Arnold Dekker.

Daylighting oculus at the top of the Pantheon in Rome. Image by Arnold Dekker. License: GNU FDL

One of the earliest uses of solar power, besides agriculture, was in lighting. A window, or oculus, would be positioned to allow sunlight into a building acting as the sole source of light during the day. In modern times solar energy is used for heating water, generating electricity, distilling water, more efficient agriculture (greenhouses), and climate control of buildings.

Another important aspect to solar energy is that it fuels almost every other energy source we use. The Sun causes the wind for our wind turbines. It generates the tides (with the Moon), waves, and rain for our hydroelectricity. Biomass and resulting biofuels rely on photosynthesis to grow. Even fossil fuels were originally created by living organisms that relied on sunlight. The only exception is geothermal energy that uses the heat from the core of the Earth and nuclear energy but consider that the Sun is a giant nuclear reactor itself.

Solar Power in the News

Solar Power Breaks Through 2000 Megawatt Threshold – 2013-06-08
FOLSOM, Calif.–(BUSINESS WIRE)–Solar power shines, setting a new all-time high output of 2,071 megawatts (MW) at 12:59 p.m. today, June …
Solar Energy: A sustainable solution to power cuts and rising … – 2013-06-08
Solar-based power back-up systems are emerging as a sustainable solution to the constant problem of erratic power supply during the summer …
US to Lead Clean Energy M&A as Solar Stays in Lead – 2013-06-08
The U.S., with 42 percent of the $37.8 billion in clean-energy mergers and acquisitions activity last year, will maintain its top spot this year led …
Minnesota’s New (Standard Offer) Solar Energy Standard – 2013-06-08
A friend at Fresh Energy generously called me the architect of Minnesota’s new solar energy standard (signed last week), and although that …
What Makes Solar Energy a Good Investment? – 2013-06-07
Fortunately, solar energy is a great investment for Americans, particularly when paired with new kinds of investment marketplaces like Mosaic.
World’s Largest Coal Company To Use Solar Power In Bid To Cut … – 2013-06-07
But when the world’s largest coal producer turns to solar power admid concerns its coal reserves won’t last much longer, people start to take …
Innovative solar cell structure stores and supplies energy … – 2013-06-07
Solar panels on the roof of a Madison home. A UW-Madison engineer has proposed a new design for solar panels that can simultaneously …
Team’s solar-powered wheelchair wins World Cerebral Palsy Day … – 2013-06-07
The team’s solar-powered wheelchair includes solar panels that are easily deployed and stored, providing nearly unlimited range at low …
Scaling Up Solar Power May Demand Updated Electric Grid – 2013-06-07
(ISNS) — One hour’s worth of global sunlight would be enough to power the world’s energy requirements for an entire year. But even if …
Innovative solar cell structure stores, supplies energy simultaneously – 2013-06-07
Solar panels on the roof of a Madison home. A UW-Madison engineer has The potential energy available via solar power might seem limitless …


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