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How Does Solar Energy Work

How Solar Energy is Produced

Using the sun for energy can be accomplished in many different ways. However, here we will explain how two major applications work. The first type of solar power extraction discussed here will be about generating electricity from the sun. The second method discussed will be solar heating, including solar water heating.

Solar Panels (Photovoltaics)

The process of capturing and using solar energy is as old as time. Like most things in the modern world, the simplicity of capturing the sun's energy has been elevated to new technological heights. Unlike solar heating collectors that are used to warm fluids running within the collector, photovoltaic cells magically convert light from the sun directly into electricity. The magic happens simply when light hits the surface of semiconductor material, electrons are released from the outer shell of atoms in the semiconductor material. These free electrons become available for electron flow, otherwise known as electric current. All that is needed to capture this current is some kind of loading device such as an home appliance, or a storage device such as a rechargeable battery.

Mono-crystalline Solar Panel
Mono-crystalline Solar Panel

The photovoltaic cell used in renewable-energy systems is definitely the product of rocket science, powering communications satellites to ensure everyone on the planet can watch reruns of Friends.

The term photovoltaic is derived from the Greek word "photo", meaning light, and "voltaic", voltage which assists the flow of electricity. Friends simply call them "PV" cells for short. Bell Laboratories discovered the PV cell effect in the 1950s. It didn't take the folks at NASA very long to figure out that PV cells would be an ideal means of producing electricity in space. Many missions later, PV cells have improved in performance and have come back down to earth in price. Nowadays, the technology is used in watches, calculators, street signs, and renewable-energy systems for the urban homeowner.

Solar Panel Array
Solar Panel Array

For the home renewable-energy system, PV products are relatively standardized, allowing even a novice to make accurate comparisons between product lines. There are currently four major product technologies that should be seriously considered for home use: mono crystalline, polycrystalline, laminate (roof shingles) and string ribbon cell. Other cell technologies such as "thin film" are an option provided product warranty and manufacturer financial strength to honor the warranty period are acceptable. Find out more about solar panels here.

Solar Concentrating Systems for Electricity Generation

These systems are usually very large, taking up many acres, in order to make them cost effective. This technology uses mirrors to concentrate the sun's light on to a small tube fill with oil. The oil is moved through the long tube, with cool oil going in and hot oil coming out. The light is converted to heat which drives a heat engine (usually a steam turbine) connected to an electrical power generator. The heat can also be stored in some heat retentive material such as molten salts for electric generation at night.

This kind of solar energy system can be implemented in several ways.

  • Solar Parabolic Troughs

    A solar parabolic trough concentrates solar light on to a long thin pipe with oil running through it. The hot oil can then be used to boil water for steam, which can drive a turbine to generate electricity.

    solar concentrating parabolic trough
    Solar Concentrating Parabolic Trough

  • Solar Parabolic dish

    Solar parabolic dishes concentrate to a single focal point, converting light into heat heat, which then can be stored or changed to steam.

    solar concentrating parabolic dish
    Solar Concentrating Parabolic Dish

  • Central Receiver or Tower

    Performs the same function as the previous two concentrators on a larger scale. Typically, terrestrial mounted mirrors surround a very tall tower. The mirrors reflect sun light into the tower to concentrate heat. The heat is then used to create steam, which can turn a turbine, thereby, creating electricity.

    solar concentrating tower
    Solar Concentrating Tower

    Another type of solar concentrating tower is very tall. It uses the chimney effect to power wind turbines at the base of the tower. As the tower heats up from mirrors that reflect the sun, hot air exhausts from the narrow top, drawing cool air in from the ground. Wind turbines are mounting around the base of the tower, being powered by the moving cold to hot air. This is a very large scale structure that can generate many megawatts of power. Here is a video illustrating the power.

Passive Solar Heating

Passive solar heating has two main applications: to heat water and to heat buildings.

Passive Solar Water Heating

The most popular application for solar water heating in warm climates is for swimming pools. A black array of tubes is usually placed on the roof of a home. There is an inflow spigot and an outflow spigot. Cold water comes into the bottom of the array from the pool. Hot water flows out of the array back to the swimming pool. A simple water pump keeps the liquid flowing.

solar pool heater
Solar Pool Heater

Solar water heating can also be used to heat your house water, either in conjunction with your conventional gas powered water heater, or totally. Several types of solar home water heaters are available. See more detail on home solar water heaters here.

Passive Building Heating

There are two main ways to heat a building with the sun's energy. One is to design the structure to capture as much winter sun as possible, given the location's latitude. This structure should also block most of the summer sun from penetrating the interior of the building to reduce summer cooling needs. The home usually has an equator facing solarium or greenhouse that captures sunlight and heats the rest of the through thermal mass. If the structure is built properly, no furnace or other carbon based heater is needed. The thermal mass of the building retains heat during the day, to be dispersed in the living quarters at night. This type of structure can be built in the coldest of climates.

solar home design
Solar Home Designed to Take Full Advantage of the Sun

The second strategy is to build a solar collector box that is mounted on the exterior of the building or roof. The insulated box is ducted into the building, delivering warm air pushed by a low speed fan. Like the solar hot water heater, the box has two ports, one to pull cool air from a low point in the building, another to pump warm air high in the building. For this externally mounted heater to be most effective, the building and the box heater must be well insulated. Any thermal leakage from the building greatly diminishes the effects of the heater. An excellent book on passive solar heaters was written by residents of a cold Colorado town, San Luis Valley. The Complete Handbook of Solar Air Heating Systems by Steve Korner with Andy Zaugg is an excellent to building one of the kind of heaters.

There are many homemade projects of this type of heater using all kinds of materials, including recycled. Here's a passive solar heater made from soda cans.

Other Uses of the Sun's Energy

  • Electronic Device Battery Chargers
  • Solar Powered Landscape Lights
  • Solar Power Ornaments
  • Your Ideas Here

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