DOE/CH10093-272

FS 118

August 1994

Solar Heating and You

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

A Solar Collector vc-cd6-a0874-01

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.

Covers

Many clear materials

can be used as covers for

solar collectors, but

glass is the most

common material. Glass can be

made quickly and easily. The

special glass used in solar

collectors resists breaking and

scratching.

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.

Absorbers

The heat produced inside a

solar collector is soaked up by

metal sheets or containers

filled with water, rocks, or

bricks that have been painted

black or another dark color.

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 Technical Information 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.

Printed with a renewable source ink on paper containing at least 50% wastepaper and 10% postconsumer waste
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.

A Sunspace vc-cd6-a0874-02

These dark-colored objects that

soak up heat are called

absorbers. Without absorbers,

solar heating systems would not

produce enough heat to warm

rooms inside your house.

Insulation

Heat always tries to move from

a hotter object to a colder one.

Insulation is what prevents or

slows down the movement of

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 a solar collector is

working properly, the heat that

it produces moves from the

collector to an area where that

heat can be used. If the

collector’s job is to heat air,

then vents, ducts (air tubes),

and fans carry the heated air

from the collector to another

part of the house. If the

collector’s job is to heat water,

then pipes, tubes, and pumps

move water from the collector

to water heating or space

heating equipment.

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.

Sunspaces

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

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Flat-Plate Collectors vc-cd6-a0874-03

Active Solar Air Heater vc-cd6-a0874-04

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.

Flat-Plate

Collectors

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

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Active Solar Water Heater vc-cd6-a0874-05

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.

What Have You

Learned?

1. What two forms of energy

does the sun provide?

2. What are solar collectors

and how do they work?

3. What parts do most solar

collectors have?

4. Which car would be a better

example of a solar collector?

A car that has:

a. black seats and open

windows?

b. dark blue seats and closed

windows?

c. white seats and open

windows?

5. Explain your answer to

question 4.

6. What is a passive solar

home?

7. Are there places in your

community where you can

buy solar collectors? (Look in

the yellow pages section of

your telephone book.)

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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1. Find a south-facing window and measure 2. Cut out a piece of cardboard the same

its width and height. height and width of the window but with

four 5-inch (12.7-centimeter) flaps

extending from the top, bottom, and

sides.

vc-cd6-a0874-07

3. Apply a coat of gesso paste to one side of 4. After the paste has dried, paint the same

the cardboard. Allow the paste to dry for side of the cardboard with flat black

10 minutes. acrylic paint. Allow the paint to dry.

vc-cd6-a0874-08

5. Cut vent holes 3-inches (7.6-centimeters) 6. Push thumbtacks into the cardboard

wide by 3-inches high near the top and around the vent holes on the inside

bottom flaps of the cardboard. surface.

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7. Weave some thin string around the 8. Cover the thumbtacks with thin strips of

thumbtacks and across the vent holes. duct tape to prevent them from falling

out of the cardboard.

vc-cd6-a0874-10

9. Cut enough plastic wrap to cover the vent holes and tape the plastic to the outside (black side)

of the bottom vent holes and to the inside (string side) of the top vent holes.

vc-cd6-a0874-11

10. Slide the cardboard inside the window frame with the black side facing the window and the

top vent holes up. (The plastic flaps should be hanging over the vent holes.) Tape the

cardboard to the window frame with masking tape and leave an air space between the window

and the cardboard.

Hint: Don’t leave your collector taped to the window frame for too many days, or the tape may

pull paint off when you remove it.

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11. On the graph paper, draw lines marking

three columns, and write the words

"Time," "Intake (bottom) temperature,"

and "Output (top) temperature" at the

top of the columns.

13. Did your solar collector work? During

what time of the day was the collector’s

output temperature the highest? What

was the highest output temperature of

the collector on a cloudy day? On a

sunny day?

12. Once every hour for a few hours on a

cloudy day, and for a few hours on a

sunny day, hold the thermometer under

the plastic flaps covering the vent holes

for 2 minutes to measure the collector’s

air intake (bottom) and output (top)

temperatures. Mark your temperature

readings on the graph paper.

Glossary

Absorbers: dark-colored objects that soak

up heat in solar collectors.

Active solar heater: a solar water or

space heating system that moves heated

air or water using pumps or fans.

Covers: clear materials that allow sunlight

to pass into solar collectors and trap heat

inside the collectors.

Flat-plate collector: large, flat boxes

with glass covers and dark-colored metal

plates inside that absorb heat.

Insulation: materials that prevent or

slow down the movement of heat.

Passive solar heater: a solar water or

space heating system that moves heated

air or water without using pumps or fans.

Passive solar home: a house that uses a

room or another part of the building as

a solar collector.

Pipes: tubes that carry heated water

from solar collectors to hot water tanks.

Solar collectors: boxes, frames, or rooms

that trap the sun’s rays to produce heat.

Sunspace: a room that faces south, or a

small structure attached to the south

side of a house.

Thermal mass: materials that store heat

within a sunspace or solar collector.

Vents: tubes that carry heated air from

solar collectors to other parts of a house.

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Resources

Energy Activities for the Primary Classroom,

California Energy Extension Service,

Governor’s Office of Planning and Research,

1400 Tenth Street, Sacramento, CA 95814;

(916) 323-4388.

The Universal House: Energy, Shelter, and

the California Indian: Activity Guide, 4th/5th

Grade, California Energy Extension Service,

Governor’s Office of Planning and Research,

1400 Tenth Street, Sacramento, CA 95814;

(916) 323-4388; Fall 1992.

Science Projects in Renewable Energy and

Energy Efficiency, published by the American

Solar Energy Society, distributed by the

National Energy Foundation, 5160 Wiley Post

Way, Suite 200, Salt Lake City, UT 84116;

(801) 539-1406; 1991.

Teach With Energy! Fundamental Energy,

Electricity, and Science Lessons for

Grades K–3, National Energy Foundation,

5160 Wiley Post Way, Suite 200, Salt Lake

City, UT 84116; (801) 539-1406; 1990.

Teach With Energy! Fundamental Energy,

Electricity, and Science Lessons for

Grades 4–6, National Energy Foundation,

5160 Wiley Post Way, Suite 200, Salt Lake

City, UT 84116; (801) 539-1406; 1992.

The Solar Home Book: Heating, Cooling, and

Designing with the Sun, by Bruce Anderson

with Michael Riordan, Brick House Publishing

Company, ISBN: 0-917352-01-7; 1976.

A Golden Thread: 2500 Years of Solar

Architecture and Technology, by Ken Butti

and John Perlin, Van Nostrand Reinhold

Company, ISBN: 0-442-24005-8; 1980.

Renewable Energy Fact Sheets, Solar Energy

Industries Association, 122 C Street, NW,

4th Floor, Washington, DC 20001-2109;

(202) 383-2600.

Experimenting with Energy, by Alan Ward,

Chelsea House, ISBN: 0-7910-1510-6;

1991.

Renewable Energy: A Concise Guide to

Green Alternatives, by Jennifer Carless,

Walker & Company, ISBN: 0-8027-8214-0.

Renewable Energy, by Alan Collison, Raintree

Steck-Vaughn, ISBN: 0-8114-2802-8; 1991.

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