Solar Heating... a primer
The sun gives us energy in two forms: light and heat. For many years, people have been using the sun's energy to make their homes brighter and warmer. Today, we use special equipment and specially designed homes to capture solar energy for lighting and heating.
What are solar collectors, and how do they work?
Solar collectors trap the sun's rays to produce heat. Most solar collectors are boxes, frames, or rooms that contain these parts: (1) clear covers that let in solar energy; (2) dark surfaces inside, called absorber plates, that soak up heat; (3) insulation materials to prevent heat from escaping; and (4) vents or pipes that carry the heated air or liquid from inside the collector to where it can be used.
When sunlight passes through glass and hits a surface inside a solar collector, it changes into heat. Although glass allows sunlight to pass through, it also traps the heat produced inside the collector.
Cars with dark seats are good examples of how the absorbers in solar collectors work. Did you ever sit on a dark car seat in shorts after the sun had been shining on it for a long time and the windows were closed? Ouch! When solar energy passes through the windows of a car, heat is absorbed by the seat. If the seats were a lighter color, like yellow or white, light would be reflected away from the seats, and less heat would be absorbed. Dark-colored seats absorb more heat.
Because insulation prevents the heat inside a solar collector from moving to the outside where the temperature is lower, it is an important part of any solar collector.
Vents and Pipes
When fans or pumps are required to move heated air or water, the heater is called an active solar heater. If the heated air or water from the collector moves to another part of the house naturally without fans or pumps, then the heater is called a passive solar heater.
Solar collectors come in many shapes and sizes. A home that uses a room or another part of the building as a solar collector is called a passive solar home.
In many cases, passive solar homes use rooms called sunspaces to capture solar energy directly. A sunspace can be either a room that faces south or a small structure attached to the south side of a house.
Sunspaces have a large amount of glass and large areas of dark stone or concrete walls and floors. These materials make up the thermal mass, which absorbs heat.
Vents placed against the back wall of a sunspace allow heated air to move naturally into nearby rooms. At the same time, cooler air from nearby rooms can move into the sunspaces.
Another type of solar collector is the flat-plate collector. Flat-plate collectors look like large, flat boxes with glass covers and dark-colored metal plates inside that absorb heat. Flat-plate collectors are usually placed on roofs of houses where no trees or tall buildings will block the sun's rays.
Air or a liquid, such as water, flows through flat-plate collectors and is warmed by the heat stored in the absorber plates. The air or water heated inside the solar collectors then heats air or water inside the house. In an active solar air heater, a fan pushes the air heated inside the collector into a large bin full of rocks under the house. The heat is stored there so it can be used later. In an active solar water heater, the water heated inside the collector is pumped through pipes into a hot water tank.
The first flat-plate collectors were installed on the roof of a house in Los Angeles in 1909. Since then, millions of solar water and space heaters have been installed in homes and other buildings all over the world.
Why Use Solar Heating Systems?
Today, solar heating is becoming more important than ever before. Natural gas and oil, which are burned to heat our homes and water, are limited. As reserves of gas and oil shrink, these fuels become more expensive. If more people began using solar heating systems, fossil fuels such as oil and gas would become less expensive and last longer.
Burning natural gas and oil in our heating systems also causes air pollution. Even electric water and space heaters cause air pollution indirectly, because coal and natural gas are burned to produce electricity in large power plants. So if more people used solar energy to heat the air and water in their homes, our environment would be cleaner.
Children's Activity - Making A Solar Air Heater
(An adult should help you with this activity.)
Materials needed: cardboard, measuring tape, scissors, acrylic gesso paste, black acrylic paint, paint brush, thumbtacks, duct tape, thin string, plastic wrap, masking tape, thermometer, graph paper.
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This document was produced for the U.S. Department of Energy (DOE) by the National Renewable Energy Laboratory (NREL), a DOE national laboratory. The document was produced by the Information Services Program, under the DOE Office of Energy Efficiency and Renewable Energy. The Energy Efficiency and Renewable Energy Clearinghouse (EREC) is operated by NCI Information Systems, Inc., for NREL/DOE. The statements contained herein are based on information known to EREC and NREL at the time of printing. No recommendation or endorsement of any product or service is implied if mentioned by EREC.
This article appears with slight modification courtesy of EREN... the Energy Efficiency and Renewable Energy Network , a division of the U.S. Department of Energy.
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