Types of Solar Energy

Types of Solar Energy
Types of Solar Energy (Image: Solar Installation Wayne National Forest)

Solar energy is at the root of almost all our energy. Besides the obvious energy that the sun's radiation creates, it is responsible for the vegetation that created our oil and gas supplies. It is responsible for the wind and the tides.

The contemporary discussion of solar usually refers to passive, thermal or electric. Solar passive is the use of sunshine for heating buildings with open space and well positioned windows.

Solar thermal is currently the most efficient use of sunshine. This is often the heating of water or a liquid. Solar photovoltaic can be defined as the conversion of sunlight into electricity.

Solar Passive

Architects and builders have incorporated solar passive for years. This basically involves positioning the house to take advantage of the southern exposure. A builder will design big windows and skylights to allow the direct flow of sunlight into the house. He/she will make sure that the windows are energy efficient in their design, and that there are building materials (like stone) that will absorb the heat from the sun and displace the heat into the house at night. The builder will also make sure that the house is well sealed to keep the warm air in and cold air out. They will pay plenty of attention to the insulation.

Passive solar rocks - Creative Commons Flicker
Passive solar rocks - Creative Commons Flicker

Solar Hot Water Heaters

There are Solar Hot Water heaters that are still working in Florida from the 1930s. The concept is very simple. You pump water to the roof where it resides in a solar panel. The sun heats the panel where the water is usually in coated tubes and then the water is returned to a hot water tank and is ready for distribution in your home or business. The three major systems that are currently popular are evacuated tube collectors, glazed flat plate collectors and unglazed plastic.

These panels are then made part of a system that either is built in a tropic (a no freeze zone) and then sub tropic and temperate zones where freezing is either possible or probable. Where freezing is possible there are safeguards built into the system keep the water from freezing. The systems usually have a mixing tank since solar can heat the water two 200 degrees, when the desire is usually for 140 degrees.

There are around 1.5 million solar hot water heaters in the United States. This is less than one percent of the possible homes. Ninety percent of all homes in Israel and Cyprus have solar hot water heaters.

Solar Hot Water System - Department of Energy
Solar Hot Water System - Department of Energy

Solar Thermal

Solar thermal is in the midst of tremendous growth for the production of electricity. Technology has provided ways to concentrate the sun's rays with coated mirrors that are mounted on mechanical arm that moves the mirror (with the aid of a computer) to maximize the sun's rays on a liquid which is super heated (300 degrees Celsius to 3,000 degrees Celsius). The super heated fluid is then run through pipes that heats water and turns the water into steam. The steam then turns turbines that produce electricity.

The three major types of these concentrators: a: parabolic troughs, b) parabolic dishes, c) central receivers.

There are major developments of these larges scale systems throughout the world. Several of the largest utilities in the United States are currently building mega watt facilities for additional production of electricity.

Solar Thermal Electricity Production - Alforesem, Flicker
Solar Thermal Electricity Production - Alforesem, Flicker

Solar Photovoltaic

Solar (photovoltaic) PV panels are the most common type of solar panels seen on homes and small businesses. There has been tremendous development of solar photovoltaic in the last five years. Europe made huge commitments to the purchase and installation of these systems through incentives to their citizens. This created the need for additional manufacturing capacity and brought the prices down.

The Solar PV system is usually built with solar cells. Theses cells are usually made of silicon and they are coated to better reflect the sunlight. The cells are layered into the panel with a positive layer next to a negative layer. When the sunlight hits the cell electrons move back and forth from positive to negative. There is an external circuit which draws off electrons to be sent through wires (most commonly) to an inverter which converts what is DC current into 120/240 electric current used in most homes and small businesses.

Solar PV Panels - Jeremy Levine
Solar PV Panels - Jeremy Levine

The Future of Solar and You

In 2008, solar PV took off like never before. The production of solar roof top electricity far exceeded the new production of electricity by all the U.S. utilities combined. There is now a 30 percent federal tax credit towards the purchase of a solar system. There are also state and local incentives available, but the credits or rebates vary widely. Moreover, in some states there is net metering where you can sell your excess solar power back to your utility.

The most affordable solar systems are for solar hot water and can start at $2,500 for a DIY kit. The most expensive are off the grid systems that provide all your electricity with a battery back up system. This can easily run $30,000 to $50,000.

The most important steps are to first figure out how to conserve the electricity you are already using, figure out how much you can afford to put towards a solar PV system and then start shopping with solar licensed dealers, who spend more time helping you to understand their systems and less time trying to sell you.

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