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Published July 24, 2008 09:02 AM

Clean Tech Intro: The Solar Family

Solar power means more than solar panels. These days it can also mean collectors, towers, dyes, oh my! Here’s a guide to (most of) the different kinds of solar technologies that are out there today.

First, the basics: Anything that uses solar energy as a source of power is solar-powered. Simple, right? Well let’s not forget that the sun gives us more than a whole spectrum of light, it also gives us heat. Both are used for a wide variety of applications, not just electricity.

1. Solar Thermal

Solar thermal technologies use heat. Cleantechnica has already introduced solar thermal. The cheapest, easiest, and most financially sound solar investment you can make for a house is to install a solar thermal collector. It collects solar energy to provide warm water or warm air for your house, even in the far north. On a larger scale, mirrors can be used to focus heat from the sun to boil water and turn a turbine. Generating electricity with this method is called Concentrated Solar Power (CSP). Large scale CSP projects are already underway in deserts around the globe, and in some places they are invigorating the economy.

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The cool thing about CSP is that it overcomes one of the major problems with renewable energy. It used to be true that solar farms stopped producing energy as soon as the sun went down. No longer. Heat is much easier and cheaper to store than electricity, so you can save it for the hours or days when the sun doesn’t shine. Power towers and molten salt are just two methods of producing solar power whenever we need it.

2. Photovoltaics

Photovoltaics are solar technologies that transform light into electricity. Certain elements and chemicals, called solar cells, can lose electrons when exposed to photons (light). Under the right conditions, these electrons are harnessed as electricity. For a more technical explanation, check out Wikipedia. To learn more about the use of solar photovoltaics on homes for energy-production, click here.

3. Silicon

This is the most widely used and recognizable material used to make solar panels. Paired with solar cells, silicon can produce high efficiency solar panels. However, silicon panels tend to be more expensive to make, transport, and install because they’re heavy, rigid, and require plenty of high-quality materials. Thin-film silicon panels attempt to overcome these obstacles. The downside: silicon panels work best on cloudless days when the sun is directly overhead. That’s why silicon panels are often positioned on racks to face the sun. The cost of these racks, and loading the panels on them, often consume 50% of the cost of silicon panel installation.

Another strategy to reduce the cost of silicon panels is to use less of them, but still generate plenty of energy. This is possible by concentrating sunlight onto the panel. More intense light means more energy” if you don’t melt your panel in the process. This technology is called Extreme Concentrated Photovoltaics (XCPV).

4. Thin Film

 Thin film solar panels are very thin and flexible; the solar cells can be placed on sheets of plastic or aluminum. They should not be confused with silicon thin-films, which use a different manufacturing method. Thin film solar panels tend to be easier to make, use fewer and cheaper materials, and are easier to transport and install. Some thin films absorb different wavelengths of light, which can make them more practical in cloudy regions. The downside: they’re still less efficient than silicon panels, so they don’t produce as much energy. Their efficiency can sometimes degrade over time, depending on the materials and environment. To learn about thin-film installations on homes, click here.

5. Solar Dyes

Here is another promising technology that is still being developed. Invented by the Swiss in the 1990s, the idea is to produce solar cells in cheap, easy, attractive dyes that can be painted or sprayed onto almost any surface. The benefit is both cost and application: the dyes are only one tenth of the cost of silicon panels and you can boldly take them where solar has never gone before. Imagine painting your house with solar cells and reaping just enough energy to power your microwave. That is the downside: solar dyes are not yet as efficient as thin film solar, and many dyes only last several years instead of decades.

6. Radical Solar Technologies

Some tech exists that push the definition of “solar power”. For example, algae can be used to produce biodiesel and ethanol. If you fill your car with this fuel, is your car solar powered? What about passive solar technology, which controls how and when sunlight affects buildings? Since the sun is a major engine driving our planet, the possibilities for harnessing its energy are infinite.

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