Subject: Solar for Kids

From: Carlos Portela <[email-masked]>
Date: Mon, 12 Aug 1996 14:25:13 -0700

It's winter in Australia, and kids are in school there.
Children in Penrith, Australia are using the net in
school and found our Solar Architecture Index web page
(http://www.teleport.com/~solar3d/solar) by conducting
a search in Yahoo.  They then sent us an email message
asking for general information about solar energy,
such as "who invented it," "what is it good for," etc!
In response we sent them the NCSC Fact Sheet for school
children via email.  That fact sheet is included below
in this message for other children to read.

We would like to compile a list of children's resources
on solar and renewable energy, to list on our web site
for other kids to find.  Any one that knows of a
solar for kids resource we should list, please email
or post it.  Thanks for helping kids on the net!

Carlos Portela
-- 
3-D Software
P.O. Box 220, Mapleton OR  97453  USA
[email-masked]
http://www.teleport.com/~solar3d

      |--------------------------------------------------------------|
      |                   "Solar Energy and You"                     |
      |                                                              |
      |                 A Factsheet Prepared by the                  |
      |                 North Carolina Solar Center                  |
      |--------------------------------------------------------------|

      Solar Energy is heat and light that comes from the sun. Thousands
of
years ago, some people used solar energy to heat their homes.  Today,
solar energy is again being used to heat buildings.
      Why is everyone interested in solar energy now?  The reason is
that
the fuels we burn in our furnaces are very expensive, and the supply of
these fuels is shrinking every day.  They are not renewable like solar
energy is.  Burning these non-renewable fuels also pollutes the air we
breathe and harms our environment. That is why people are trying to find
new ways to heat their offices, factories, offices, and schools without
using so much expensive oil and gas.
      Before you learn how the sun can provide heat for buildings, there
are a few facts about your home's heating system that you should know.

+ HOW IS YOUR HOME HEATED?

      Houses are warm in winter, but where does the heat come from? 
Most
of the heat comes from burning fuel.  The logs on a campfire or in your
fireplace are a type of fuel, and the fire itself is a heat source.  The
heat source keeps your home warm.
      What is the heat source in your home?  Most house and apartment
buildings have a type of large stove called a furnace in the basement. 
The furnace burns fuel and is the heat source for the whole building. 
Some furnaces burn wood or coal for fuel, but most of them burn oil or
natural gas to produce heat.  Some houses don't have furnaces.  Their
heat
is produced from electricity.
      A campfire or fireplace can heat only the space that is right
around
it.  However, the heat from the furnace must heat all the rooms in a
house.  How does this work?  The heat produced by the furnace is used to
warm either water or air.  Then pumps or fans move the hot water or air
to
the rest of the house in water pipes or special large tubes for air
called
air ducts.  This movement of the hot water or air to warm other rooms is
called heat distribution.
      In addition to a heat source and a heat distribution system you
need
a way to control the amount of heat in your house.  Then the rooms won't
be too hot or too cold.  How does the furnace know when you need more
heat?  Maybe you have noticed a small box mounted on the wall at home or
at school that has a dial inside it.  This box is called a thermostat. 
It
measures the room temperature and signals the furnace to send more or
less
heat.

+ HOW CAN SOLAR ENERGY HELP?

      The sun is a giant heat source.  If you can collect enough solar
heat, you can use it instead of the heat from a furnace.  One way to
collect heat is to trap solar energy with solar collectors.  An example
of
how solar works is a car that has dark seat covers and has all its
windows
closed tightly.  When sunlight passes through the glass windows of the
car, it is absorbed (taken in ) by the dark seat covers and walls and
floor.  Light that is absorbed changes into heat.  If the seat covers
are
a pale color, such as white or yellow, they would not absorb as much
sunlight. So pale colored seats do not become as hot as dark seats.
      Now here is an interesting fact about glass; it lets light in, but
it does not let all the heat out.  Even if it is cold outside, the
inside
of the car will be warm from the trapped heat.  so a solar collector
does
three things: 1) it allows sunlight inside through glass (or plastic);
2)
it absorbs the sunlight and changes it into heat; 3) it traps most of
the
heat inside.  this is called the Greenhouse effect.
      Solar collectors become so hot that they can be used as heat
sources
for a building.  there are two kinds of buildings that use solar
collectors as heat sources: passive solar buildings and active solar
buildings.  These two kinds of solar heated buildings will be explained
in
the rest of the fact sheet. 

+ WHAT ARE PASSIVE SOLAR HOUSES?

      In some cases, a whole house itself is a solar collector (just
like
the car).  These houses are called passive solar homes because they
don't
use any special mechanical equipment such as pipes, ducts fans, or
pumps. 
Since the sun shines from the south in North America, passive solar
houses
are built so that most of the windows face south.  They have very few
windows on the north side.
      Some passive homes have greenhouses attached to them to let in
light
and trap the heat.  The greenhouse is also used to grow plants because
its
many windows provide a lot of sunshine for the plants.  Passive houses
use
walls and floors to absorb solar energy and turn it into heat.  Passive
homes do not use a mechanical heat distribution system.  Instead, a
passive home works because hot air is lighter than cold air.  Because it
is lighter, the hot air will naturally rise to the top of a room,
leaving
the cold, heavy air near the floor.  In a passive home, air that is
heated
downstairs will naturally flow upstairs.  Cold air will flow downstairs
and will be heated up again.
      To control the amount of heat in a passive solar house, people
close
doors and windows to keep heated air in and open doors and windows to
let
heated air out.  At night, special heavy curtains or shades may be
pulled
over the windows to keep daytime heat inside the house.  In the
summertime, awnings or roof overhangs help to cool the house by shading
the windows from the high summer sun.
      Some people can't design their houses to use solar energy this
way. 
They too can use the sun for heat by choosing an active solar system.

+ WHAT ARE ACTIVE SOLAR HOUSES? 

      Some buildings do use special mechanical equipment to collect and
distribute solar heat.  These buildings have active solar heating
systems. 
Active systems use collectors which look like flat boxes covered with
glass.  Dark colored metal plates inside the boxes absorb sunlight and
change it into heat. 
      Air or water flows through the collectors and is warmed by this
heat.  The warmed-up air or water is then distributed to the rest of the
house just like in an ordinary furnace system.  Thermostats are also
used
to control the delivery of heat in active solar heating systems.  Active
solar collectors are usually placed high up on roofs where they can
collect the greatest amount of sunlight.  They are put on the south side
of the roof in a place where no trees or tall buildings will shade them. 

+ STORING SOLAR HEAT

      When a furnace is used to heat a building, you don't need to store
any heat as long as there is more fuel.  Whenever heat is needed, you
simply turn on the furnace.  But when a solar heating system is used,
what
will happen at night or during cloudy weather when no sunlight can be
collected?  Solar energy systems must include some ways of storing the
heat that was collected during sunny weather.
      In active systems, either hot water is moved to large tanks of
water, or hot air is moved to bins of rocks beneath the building. When
it
is needed, the hot water or air is taken back out of storage and sent to
the living areas.
      In a passive house, heat is absorbed by the thick walls and floors
during the day.  At night, when it becomes cold outside, warm walls and
floors release their heat back into the room.  If you have ever leaned
up
against a sunny brick wall or dark rock on a cold day, you were leaning
on
warm solar storage.

+ BACKUP HEATING SYSTEMS

      Passive and active solar heating systems can store enough heat for
overnight and for short periods of cloudy weather, but what happens if
it
is cloudy several days in a row? 
      In addition to the solar heating system, all solar homes also have
a conventional home heating system such as a furnace, heat pump, or wood
burning stove.  The backup heating system works just like it would in a
conventional home, only it isn't needed nearly as often.

+ OTHER USES OF SOLAR ENERGY

      Solar energy can be used in many other ways besides heating
buildings.  Solar photovoltaic cells change sunlight directly into
electricity; solar energy heats water for homes and businesses; and
sunlight can even be used to cook food.  As our supplies of precious gas
and oil get smaller, we will find new uses for energy from the sun.

+ WHAT HAVE YOU LEARNED?

>From  Your Readings

1.  What is the definition of solar energy?

2.  What are 4 kinds of fuels?

3.  Explain each of these parts of a heating system:
    
    a.  heat source.

    b.  heat distribution.

    c.  heat control.

4.  Which car would be the best example of a solar collector? One with:

    a.  black seats and its window open?

    b.  dark blue seats and its windows closed?

    c.  white seats and its windows closed?

5.  Explain your answer to number 4.

6.  Describe a house with a passive solar system.

7.  Describe a house with an active solar system.

8.  Which kind of house would you prefer?  Why?

9.  Why must solar energy systems have heat storage?

10. What can solar energy be used for besides heating buildings?

>From  Your Research

1.  What kind of heating system does your house have? (Hint: What is the
heat source, heat distribution system, and heat control system in your
home?)

2.  How much do you think it costs to heat your house for one month in
the
winter? (Check with your parents.)

3.  What climates would be the best for solar heating?

4.  Would your home be able to use solar heat? (Hints: Is the south side
unshaded?  Is your home well insulated?)

5.  Are there places in your town where you can buy solar collectors?
(Check the telephone book.)

+ IF YOU WANT TO KNOW MORE...

How Heat Moves

      Heat always moves from a hot object to a colder one.  When the two
objects are touching each other, heat is transferred by conduction. 
When
you lean against a cold wall, you warm the wall by conduction.  When you
lean against a dark, warm wall, the wall heats you.
      When two objects are not touching each other, heat still travels
>from  the warmer to the cooler one, but this type of heat transfer is
called radiation.  The sun heats the earth by radiation; your fireplace
heats you by radiation.
      When heat is carried from one body to another in a fluid such as
air
or water, and the transfer depends on the fact that hot fluids rise
while
cold fluids sink, this process is called convection.  Air near the top
of
a room will be warmer than air near the floor because of convection. 
You
can often feel cold air flowing into a warm room through the space
underneath a door.  In the summer, you open the top half of your windows
to let out the warmer air near the ceiling.

+ FOR MORE INFORMATION

      The North Carolina Solar Center has a reference library as well as
other free fact sheets and information on solar energy, energy
efficiency,
and related subjects.  For more information on these topics, or to learn
more about the resources available at the Solar Center, contact us at:

North Carolina Solar Center
Box 7401
North Carolina State University
Raleigh, NC  27695-7401
(919) 515-3480
Toll-free in North Carolina:  1-800-33-NC SUN

Prepared for InterNet by:
Henry Rogers
Solar Extension Specialist
North Carolina Solar Center

      The North Carolina Solar Center is sponsored by the Energy
Division,
North Carolina Department of Commerce, in cooperation with North
Carolina
State University.  However, any opinions, findings, conclusions, or
recommendations expressed herein are those of the author(s) and do not
necessarily reflect the views of the Energy Division, North Carolina
Department of Commerce.
      The written material contained herein may be reproduced by anyone
in
any fashion provided credit is given to the North Carolina Solar Center,
the Energy Division, North Carolina Department of Commerce, and North
Carolina State University.  Contact the North Carolina Solar Center at
the
above address for free printed copies of this fact sheet.

SC105        March, 1990