"Solar
Heating Projects" formally "Do-It-Yourself Solar"
is a step by step guide through the wonderful world of solar thermal energy. All
the concepts and projects from "How to Build a Solar Hot Water
System", "Energy Independent Housing" and "Solar Thermal Energy" are included.
The 30+ solar thermal projects presented are the kind you can sink your teeth
without investing in overpriced tools and products.
Affordable, energy-efficient solar thermal applications pave the way towards a sustainable economy,
lessen our dependence on big
business, conserve natural resources, create jobs, and increase our planetary
wealth. The future
possibilities of converting stored hot water into power are explored, but the
focus of this book involves collecting and storing the sun's energy.
Clear illustrations along with a collection of multi media shows
facilitate the learning process. Thoughtless corporations may go
bankrupt, but responsible communities that make practical use of our
limited resources will always find a way to survive.
REMEMBER:
"Sun Heat" and "Oil
Story" CD-ROM Multi Media Shows
are included with this book at no additional charge.
here's a quick
peek at:
the book contents
and first chapter
Solar
Heating Projects
has formerly been printed under the name Do-It-Yourself-Solar.
All
rights are reserved for both of these books. No part of this book may be reproduced or transmitted in any
form or by any means electronic or mechanical without the express permission of
the publisher. On line support is available from www.JC-SolarHomes.com.If you have any questions or comments about this book feel free to post
them on the JC Solar Collector Forum or join the Solar Energy group or send
email to canivan@optonline.net. If
you find this book helpful you may also appreciate my other books which include How to Build a
Solar Hot Water System,Solar Thermal
Energy andEnergy
Independent Housing, but I believe
that this book is my best accomplishment so far.
RECOGNITION: My
appreciation extends to many people that made this manuscript possible such as
Professor Dathatri, the chairperson of the Solar Energy Center at Farmingdale
University, Professor Modi, the chairperson of the Mechanical Engineering
department at Columbia University, NY, the authors of books found on page 156,
my hard working Dad, the general contractor, my understanding mom, my AutoCAD
instructor, Mel, the critic Riddick, Loretta, the best cookies baker on the
block and lets not forget about the little woman who had to put up with my mood
swings and grammatical incongruities during the last 18 months, my patient
loving wife, Catresea.
about this book
If
you’re tired of waiting for government to take serious action on issues like:
air and water pollution, the energy crisis, taxes, political corruption, social
harmony, and a sustainable economy and if you believe it’s possible to: do
more with less, be creative and still earn a living you’ll appreciate this
book. Solar
Heating Projects is about getting your hands
dirty with down to earth projects made from inexpensive construction materials.
Buckminster Fuller believed that social problems are a result of “…wandering
too far from our roots”. Energy for life comes from the sun. Farmers have
always known this, but the rest of us have somehow forgotten about our sun
connection. We live on a vicarious diet of plastic wrapped food supplements and
spend our lives exchanging green pieces of paper. One day we’ll pick up the Endangered
Species Newspaper and find Homo sapiens on the top of the list. The
dumps are rapidly filling up and the ground water is becoming more toxic every
day. We won’t be able to live in a world of planned obsolescence much longer.
Asthma problems, due to a sensitivity of toxins in the air and water are on the
rise. A 160% increase in asthma problems have been reported since 1984. If the
trend continues, a terrorist invasion will be the least of our problems.
As
you progress through the book the projects will become more involved and require
a greater commitment. Your mastery of one chapter will prepare you for the next.
You are encouraged to read the chapters in order even if you never pick up a
hammer. You’ll learn to calculate the energy available from sunlight, the
efficiency of applications and also the payback period. You’ll learn to use
the greenhouse effect rather than suffer because of it. You’ll be shown how to
build solar air heating systems, and solar water heating systems and you’ll
soon understand the concepts of heat transfer, fluid mechanics, multi tank heat
storage, heat extraction, radiant heating, Trombe walls, solar collectors, solar
thermal roofs, and differential solar thermal engine hybrid systems.
You
will be introduced to Photovoltaic technology and even build a simple solar
cell, but the thrust of this book will be concerned with solar thermal energy
projects. A bibliography and glossary is also available. This book is about
sunlight.
My wish is for you to soak up all that comes your way.
CONTENTS
I.CONCENTRATORS7
II.SOLAR AIR HEATING14
Hot
Box15
Window
Box19
Trombe Wall22
Solar Greenhouse27
III. SOLAR WATER HEATING39
Simple Batch Heater40
Thermo Siphoning Batch Heater42
Solar Collector Types43
Serpentine Collector47
Collector Mounting72
Heat Storage 10174
Heat Storage 10275
Heat Storage 10377
Vault Construction 10379
Vault Plumbing 10383
Heat Storage 10490
Heat Storage 10596
Collector Plumbing103
Solar Thermal Roof106
Energy
Independence114
Radiant Heating118
Hexagonal Housing122
IV. SOLAR POWER137
Photovoltaic
Power138
Solar
Thermal Power149
IV. GLOSSARY158
V.BIBLIOGRAPHY161
aboutMr. Sun
My
books usually begin with a brief discussion about the amount of energy available
from sunlight so why should this book be any different. For you brave souls who
have already read How to Build a Solar Hot Water System, Energy Independent Housing or
Solar Thermal Energythis
chapter may seem a bit superfluous, but you might also benefit from
the clarified concepts and the additional down to earth questions and answers.
Our
five billion year old sun accounts for 99.9% of the total mass of this solar
system. Most scientists are optimistic that we'll still have this nuclear
reactor billions of years from now. Each second about 700,000,000 tons of
hydrogen are converted to about 695,000,000 tons of helium and 5,000,000 tons of
energy in the form of gamma rays. As this energy travels out toward the
earth’s surface it’s absorbed and re-emitted at lower and lower temperatures
so, by the time it reaches our tiny blue-green planet it is primarily in the
form of visible and ultraviolet light. Even though solar energy is the
largest source of energy received by the Earth, its intensity at the Earth's
surface is actually very low due to the large distance between the Earth and the
sun and the fact that the Earth's atmosphere absorbs and scatters some of the
radiation. Even on a clear day with the sun directly overhead, the energy that
reaches the Earth's surface is reduced about 30 percent by the atmosphere so the direct solar radiation that reaches the earth’s surface is about
1KWH/square meter.When
the sun is near the horizon and the sky is overcast, the solar energy at ground
level can be negligible. It also varies from one point to another on the earth's
surface. Nevertheless, in the 21th century, the sun's energy has become an
increasingly attractive source for small amounts of direct power to meet human
needs.
A number of
devices for collecting solar energy and converting it into electricity and heat
have been developed. Nine quadrillion, that’s (9,000,000,000,000,000) kilo
watts of solar energy fall on the continental United States every hour.
This is the equivalent energy available from 4.25 trillion barrels of oil. The
utilization of less than .001% of this renewable resource would satisfy all our
energy requirements. So there’s plenty of energy available. All we need to do
is figure out a way of putting the sun to work for our mutual benefit.
Let’s bring
the sun down to earth and see what its worth. We’ll begin with a typical ¼
acre building lot and calculate the energy that falls on a lot of this size in
the North East USA. Try to work these problems out on your own before peaking at
the answers.
QUESTIONS(Answers found on the following page)
1. How much direct solar energy falls on a typical ¼ acre
Long Island
lot in a year?HINTS:¼ acre = 1000 m2, 1hr. of direct sunlight/m2 = 1 KWH, 1000 KWH
of solar energy available/ m2/yr
2. If 100% of
this energy could be converted into electricity what would it be worth at $.10
per KWH?
3. If the entire surface of the ¼ acre lot were covered
with PV panels and the PV panels operated at an efficiency of 10% what would the
value of electrical harvest be during the period of one year?
4. What would the value of the heat harvest be in a year? Assume
the efficiency of converting oil into heat is the same efficiency required to
transform sunlight into heat.
5. Most people would be content with 10% of this energy so
let’s place a house on the property that has a roof which occupies 10% of the
surface (100m2).Calculate
the PV value of electricity and the collector value of heat.
6. How much heat will a one square meter collector harvest
in a year? How much will it be worth?
7. How much electricity will a one square meter PV panel
harvest in a year? How much will it be worth?
8. Compare the value of heat collection with the value of
electric power conversion if each method uses the same surface area exposed to
sunlight.
ANSWERS
1. In North Eastern States more than 1000 hours of direct
sunlight are available over the period of a year. A ¼ acre lot has a surface
area of approximately 1000 square meters. The available energy to one square
meter over the period of a year is 1000 KWH. 1000 square meters would have a
1000 times that energy… so…
1,000,000 KWH of solar energy fall on a ¼ acre lot per
year.
2. At $.10/KWH one million KWH would be worth $100,000.
3. At an efficiency of 10% PV panels would harvest $10,000
worth of electricity.
4. The heat energy available in terms of a fuel oil
equivalent would be worth $40,000 per year.
5. A 100 square meter roof lined with PV panels harvest
$1,000 per year. A
100 square meter roof lined with collectors harvest $4,000 per year.
6. A one square meter collector will harvest .02x1000 = 20
gallons of fueloil per year. At a value of $2/gal it would harvest $40 worth of heat.
7. A one square meter PV panel will harvest .01x 1000 = 100
KWH/year At
a value of $.10/KWH the electrical harvest would be worth $10.
8. A square meter of direct sunlight converted into heat is
worth about 4 times as much as a square meter of sunlight converted into
electricity with a typical PV panel. This comparison is true when we compare
typical solar collectors with typical solar panels.
FACTS
TO REMEMBER:
1KWH = one square meter of
direct sunlight / hour.
1KWH = 3,400 BTU’s
1 gallon of #2 fuel oil =
150,000 BTU’s
1 KWH = .02 gallons of fuel oil
¼ acre = (about 1000 square
meters)
1000 KWH/m2 of direct sunlight energy are available per year in N.E. USA.
Even though heat collection systems harvest more energy
than PV systems PV systems are becoming more popular because of the extensive
rebate incentives in excess of 70% for many North Eastern States. Solar thermal
systems offer few or no rebate incentives and still have a shorter pay back
period. The idea of selling solar electricity to power companies has a certain
appeal, but before you jump on the PV grid bandwagon consider the price you’ll
have to pay for a grid hook up and the time it will take to your system to pay
for itself. Do the math.
To cash in on the rebate incentive you’ll need to hire a
certified licensed electrician who’s a certified PV installer. Major oil
companies like Shell, Exxon and British Petroleum have a vested interest in
photovoltaic technology and there’s not much room for us do-it-yourselfers in
this high tech field of solar applications.As I mentioned before, most of the projects in this book are
concerned with solar thermal applications, but since so much promotional energy
is being focused on photovoltaics I’ve decided to devote one chapter to the
history, theory and construction solar cells.
All the chapters in this book are arranged in an increasing
order of difficulty and expense and you are encouraged to master the material in
each chapter before moving on to the next one. You are also encouraged to
experiment and test projects of your own design. Don’t believe me or anything
you hear or read about. Do-it-yourself discovery projects are the best teachers.
You’ll need a good digital thermometer that has a range up to or higher than
2500 F to test the results of your experiments. This thermometer
would cost about $20. For about $100 you could invest in a data logger that
could sample temperature readings over a period of time. This data could then be
used to automatically print out a graph of your results.
These companies are merely suggestions to help you get
started. I have no financial ties to them. You may have other products in mind.
If you’re on a low budget you might want to use a meat thermometer though the
readings might be a bit crude like the product they’re used on.
I
Concentrators
Concentrators are used to
concentrate the diffuse radiant energy from sunlight. They are found in desert
areas where real estate has little value except for the intense sunlight
available.
Because of the low
efficiency and large surface area associated with concentrators their useful
application in residential areas is limited.A solar cooker is
simple practical project to begin with. It may even save your life someday.
Imagine falling off the
Yukon
express on its way through
Canada
. When you finally stop rolling down the side of the mountain and come to rest
near a ravine like the KoyukukRiver you
find a cardboard box, a roll of aluminum foil and a pack of Ballpark Franks. If
you’re hungry enough you’ll probably dive right into the pack of franks, but
If you’re a city slicker like me you’ll need to cook your food first.
SOLAR COOKER
For your first project I’d like you to make a simple
solar cooker with a cardboard box that you line with aluminum foil. If the box
is large enough and the foil placed well the solar heat generated may be enough
to cook those hot dogs. A simple cooker oven could be made by lining the inside of
the box with aluminum foil, but you’ll lose a lot of the heat unless you can
find some glass or plastic to place on the lid of the box.
If you arrange the foil in the box so it has a bowl like
shape you might achieve temperatures high enough to cook hot dogs. The ideal
bowl shape used to concentrate the sun’s energy known as a parabolic dish. A
large well constructed parabolic dish can achieve a temperature hot enough to
melt steel, but we won’t need temperatures this high to cook our franks.
We’ll call this project a:
SUN BOX
Take the following temperature readings of the inside
temperature of your box. To do this you’ll probably have to secure a
temperature probe to a stick and lower it into the box. When you’re ready,
point the box directly at the sun and take the following readings.
1. Inside temperature with foil
lined box open at the top…………
2. Inside temperature with foil
lined box with plastic lid………..
3.Inside temperature with foil lined box with glass lid………..
4.Inside temperature with box painted black open at the top………..
5.Inside temperature with box painted black with plastic lid………..
6.Inside temperature with box painted black with glass lid………..
Radiant heat energy may be concentrated with a reflective
surface like aluminum foil. It may also be trapped with something known as the
greenhouse effect. This box experiment is a crude way of exploring both
concentrating and trapping methods. We’ll have plenty of projects involved
with trapping heat. For now I’d like to focus on the principles of
concentrating sunlight.
A parabola is actually the best reflecting shape for
concentrating parallel radiation, but you should be able to demonstrate the
effects of concentrating and trapping heat with a simple SUN BOX. Will have
plenty of experiments and projects that deal with trapping heat, but for now
let’s concentrate on concentrators.
A parabolic trough
concentrates light on a line. A parabolic
dish concentrates light on a point. A simple parabolic dish may be made from
a piece of aluminum foil pasted to a sheet of cardboard. Aluminum foil is not
the most coherent reflecting material but it is the least expensive so we’ll
start with this experiment. After attaching the foil to the cardboard you’ll
need to bend it in the shape of a parabola to maximize the concentration of
sunlight.
You can plot a simple parabola with any quadratic equation
such as y=x2, but you’ll need a special kind of quadratic equation
to help you find the parabola’s focal point. That equation is y=x2/4p
where p is the focal point. You could try different shape reflectors and measure
the temperatures at various points. See if you can construct a precise parabolic
reflector and measure the temperature at the focal point. Be sure to use a stick
or hanger to hold your temperature probe. You could give yourself a serious burn
if the concentrator is well made and you place your hand in line with the focal
point.
Parabolic
Dish: A
practical application of a parabolic dish is a flashlight lens, which is used to
transform a point source of light into a parallel beam. The reverse is true.
Since sunlight radiation is essentially parallel it may be concentrated at the
focal point of the lens. As a matter of fact a tiny flashlight lens may be used
as a cigarette lighter by substituting a cigarette for the bulb and by pointing the
lens in the direction of the sun. A type of solar reflector dish concentrator
may also be made by lining the inside of a cardboard box with aluminum foil.
Large experimental parabolic dishes known as heliodynes are capable of melting
steel but they operate at a low efficiency and must be continually aligned to be
of any practical value. The two axis parabolic dish tracking mirrors above are
being used to drive a Sterling engine and
generate electricity.
Parabolic troughs are used in many solar
power plants because their fabrication and tracking machinery is less
complicated than the dish. Hot oil is circulated through the flow tube at the
focal point of the parabolic trough. The hot oil is than collected and used to
boil water and make super heated steam to drive a turbine and make electrical
power.
Simple parabolic
troughs may be made with a sheet of cardboard lined with aluminum foil. I've
heard of people using this to roast hot dogs. Both solar reflectors can be used
as cookers, but we won't be cooking hot dogs today. Right? Let’s be scientific
and collect meaningful data. We’ll construct our solar reflectors with the aid
of a carefully constructed template.
Trough Construction Materials:
aluminum flashing 20"x 4', 1x8x4,
1/2" copper tube 5'long, drywall nails. If you can afford polished
stainless steel go for it. If you’re looking for something less expensive you
could paste a sheet of mirrored plastic to the finished trough. The aluminum
flashing will provide a reflective surface, but it won’t be able to provide
highly focused light. TOOLS: jig saw, hammer, drill,
3/4" bit
Cut the 1x8x4 in
half so that you have two1x8x2's. On one half of one of these boards
sketch out a grid with one inch increments. Use this grid to plot the
positive x values of the curve with a special parabola with the formula y = x2/4p.
Any quadratic equation can be used to plot a parabola, but this equation will
help you pinpoint the parabola's focal point, p. One inch increments should give
you all the points you need to plot this curve. When you're done half a parabola
should look like this.
Notice that the graph shows 1 inch
increments of x, but not of y. I've done this to clarify the y values of the
parabola. You should have no difficulty finding these points on your one inch
grid. When you're satisfied that your plot is correct cut it out with a jig
saw. Use this first cut to sketch out an identical curve on the other board and
then flip the first cut board to finish the parabola. Now finish the parabola on
the first cut board. You should now have two identical end pieces that look
like this:
Notice the 3/4 inch hole drilled at the
focal point of the parabola. This is where the five foot long 1/2 copper tube is
inserted to collect heat from the solar concentrator. Now comes the tricky part
where you might need a little help holding things. This is where the flashing is
nailed or screwed to the end supports. Pre drilling holes spaced about 3 inches
apart and about 3/8 " from the ends might be a good idea. This will
facilitate the process of joining the end supports to polished stainless steel.
If you’re a poor boy like me you could use aluminum flashing, but the focal
point won’t be as sharp. With a little care you'll build a fine parabolic
trough. Notice the furring strips on either side of the trough. These strips
give the flashing extra support and also provide a place to attach glazing.
Congratulations on the completion of your solar reflector, but you're not done
yet. To be scientific you should test your creation for efficiency and maximum
temperature gain.
TESTING On a
sunny day point the parabolic trough directly at the sun and record the maximum
temperature of the boiler/flow tube. Now cover the unit with glass or plastic
and see if the maximum temperature improves. An oven thermometer will do if
you're unable to get hold of a more accurate device.
Now attach one
end of a plastic tube to a funnel and attach the other end to a boiler/flow
tube. Pour water of a known temperature at a controlled flow rate. Notice how
hot the water gets. It might even boil. If you set up a drip rate of 1 gallon
per hour you could calculate the heat gain of the unit and compare this to the
solar energy available. I’ll leave the details of this experiment up to your
imagination. Do these experiments with and without glazing. Compare and explain
your results and suggest things that might improve the collector's performance.
The parabolic
dish is a more complicated project. You'll need to build a parabolic template
with a central axis. This is then rotated 360 degrees to plot the solar
reflector surface. Try not to get carried away with this project. Save some
energy for the projects in the coming chapters.
at we test one variable at a time so we’ll be testing
glazing material and absorber plate color separately.
Notice how
rapidly the temperature inside the hot box rose after 10 am. By 11 AM the hot box temperature was about 170 F; eventually the temperature
peaked at 200 F. After that some clouds rolled in and the temperature dropped
off. Your hot box might not get this hot, but who knows it might get hotter. A
hot box is used to demonstrate the greenhouse effect as well as test glazings
and absorber plate coatings.
A
few things to remember:
1. GREENHOUSE
EFFECT: a method of trapping heat by transforming short wave lengths of
light into long wavelengths which are reflected back by a glazing material
2. ABSORBER PLATE COLOR: an absorber
plate is used to transfer light energy into heat energy. Black substances are
generally best suited for transferring most of the light energy into heat. Black
Chrome is a popular selective coating used on many absorber plates.
3. INSULATION: The efficiency of any
solar thermal system depends greatly on the quality and quantity of insulation
used to retain heat produced from sunlight.
4. GLAZING MATERIAL: some glazing
materials are better suited for trapping long Wave radiation than others. Low
Iron tempered glass is an excellent glazing material, but there are less
expensive lighter materials that might be more suitable for certain
applications.
"Solar
Heating Projects" formally "Do-It-Yourself Solar"
is a step by step guide through the wonderful world of solar thermal energy. All
the concepts and projects from "How to Build a Solar Hot Water
System", "Energy Independent Housing" 
Our
five billion year old sun accounts for 99.9% of the total mass of this solar
system. Most scientists are optimistic that we'll still have this nuclear
reactor billions of years from now. Each second about 700,000,000 tons of
hydrogen are converted to about 695,000,000 tons of helium and 5,000,000 tons of
energy in the form of gamma rays. As this energy travels out toward the
earth’s surface it’s absorbed and re-emitted at lower and lower temperatures
so, by the time it reaches our tiny blue-green planet it is primarily in the
form of visible and ultraviolet light. Even though solar energy is the
largest source of energy received by the Earth, its intensity at the Earth's
surface is actually very low due to the large distance between the Earth and the
sun and the fact that the Earth's atmosphere absorbs and scatters some of the
radiation. Even on a clear day with the sun directly overhead, the energy that
reaches the Earth's surface is reduced about 30 percent by the atmosphere so the direct solar radiation that reaches the earth’s surface is about
1KWH/square meter.
