Solar Heating Projects  

"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.

 







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Solar Heating Projects

 by  
John Canivan

printing July, 2005                   
Sunny Future Press,
Wantagh , NY  
Copyright � John Canivan 2004
ISBN    0975498088   $75
  

  

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 and Energy 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.   CONCENTRATORS                             7

II.  SOLAR AIR HEATING                                  14

Hot Box                                                                             15

Window Box                                                                       19

Trombe Wall                                                                        22

Solar Greenhouse                                                                 27

III. SOLAR WATER HEATING                            39

Simple Batch Heater                                                             40

Thermo Siphoning Batch Heater                                             42                     

Solar Collector Types                                                            43

Serpentine Collector                                                              47

Collector Mounting                                                                72

Heat Storage 101                                                                  74

Heat Storage 102                                                                   75

Heat Storage 103                                                                   77

Vault Construction 103                                                          79

Vault Plumbing 103                                                                83

Heat Storage 104                                                                   90

Heat Storage 105                                                                   96

Collector Plumbing                                                                103

Solar Thermal Roof                                                               106

Energy Independence                                                         114

Radiant Heating                                                                    118

Hexagonal Housing                                                               122

IV. SOLAR POWER                                137

 Photovoltaic Power                                                   138

 Solar Thermal Power                                                149

IV. GLOSSARY                                                   158

V.  BIBLIOGRAPHY                                      161

 

 

 

about Mr. 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 Energy  this 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 � 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 � acre Long Island lot in a year?    HINTS:  � 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 � 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 � 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 � 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 fuel oil 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 

� 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.  

For a digital thermometer      www.professionalequipment.com  
For a data logger                  www.onsetcomp.com  
For both   try                          www.industrial-needs.com/measuring-instruments.htm                                                       

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  Koyukuk River 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.
   

 

Pick a strawberry and taste the sun!

                                                     

  Solar Heating Projects     +     (SunHeat & OilStory & SolarPlumbing) CDs              $75

   

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