How to Make a Solar Power
Generator for Less than $300
Frequently Asked
Questions about the Solar
Power Generator
How to Make a Wind
Turbine out of a Hank-
Crank Flashlight
by Phil Heiple 2010 SolarWind Press
How to Make a Solar Power Generator
for Less than $300
by Phil Heiple
Using parts easily available from the internet (see helpful
links) and your local stores, you can make a small solar
power generator for $250 to $300. Great for power
failures and life outside the power grid. Power your
computer, modem, vcr, tv, cameras, lights, or DC
appliances anywhere you go. Use in cabins, boats, tents,
archaeological digs, or while travelling throughout the
third world. Have one in the office store room in case of
power failures in your highrise. I keep mine in my
bedroom where it powers my music, lights, dvd player,
laptop, and (ahem) a back massager. I run a line out the
window to an 8" x 24" panel on the roof. This is the
smallest simplist set-up practical for daily use. It saves
me about five dollars a month off my electric bill.
1. Buy (or make) yourself a small solar panel. For
about $100 you should be able to get one rated at 12
volts or better (look for 16 volts) at an RV or marine
supplies store
2. Buy yourself a battery. We
recommend rechargeable
batteries from green companies.
Get any size deep cycle 12 volt
lead/acid or gel battery. You
need the deep cycle battery for
continuous use. The kind in your
car is a cranking battery--just for
starting an engine. Look for
bargains, the cheapest ones
should cost about $50-60.
2
3. Get a battery box to
put it in for $10. (This is
good for covering up the
exposed terminals in case
there are children about If
you going to install the
system in a pump shed,
cabin, or boat, skip this.)
3. Buy a 12 volt DC meter. Radio Shack has them for about
$25.
4. Buy a DC input. I like the triple inlet model which you can
find at a car parts store in the cigarette lighter parts section for
about $10. This is enough to power DC appliances, and there
are many commercially available, like fans, one-pint water
boilers, lights, hair dryers, baby bottle warmers, and vacuum
cleaners. Many cassette players, answering machines, and
other electrical appliances are DC already and with the right
cable will run straight off the box.
3
5. But if you want to run AC appliances, you will have to invest
in an inverter. This will convert the stored DC power in the
battery into AC power for most of your household appliances. I
bought a 115 volt 140 watt inverter made by Power-to-Go at Pep
Boys for $50. Count up the number of watts you'll be using (e.g.,
a small color television(=60 watts) with a VCR(=22 watts),
you'll need 82 watts.
Inverter
6. Use a drill to attach the meter and DC input to
the top of the box.
4
7. Use insulated wire to attach the meter to the wingnut
terminals on the battery. Connect the negative (-) pole first.
Only handle one wire at a time. Connect the DC inlet to the
battery in the same way. Connect the solar panel to the
battery in the same way.
8. Close the lid (I use a bungee cord to keep it tight). Put the
solar panel in the sun. It takes 5-8 hours to charge a dead
battery; 1-3 hours to top off a weak one. It will run radios,
fans, and small wattage lights all night, or give you about 5
hours of continuous use at 115 volt AC, or less than an hour
boiling water. This system may be added on to with larger
panels, inverters, and batteries.
5
Options: A pop-up circuit breaker may be added between the
positive terminal and the volt meter. Some of you will want an
ampmeter as well. The panels I recommend have built-in
bypass diodes, but I recommend charge controllers for people
who have panels without diodes. Another option is a voltage
regulator, which is not necessary for a system this small, but a
larger system would require one.
Basic Solar Power Generator
8" x 27" MBC-131
Uni-Solar soft panel
Rated power (Watts, peak): 5.50
Typ. 12 Volt Charging (Amp. Hrs/Wk) 13.00
Voltage, Typ. Max Power (Volts) 15.60
Current, Typ. Max Power (Amps) .35
Weight (pounds) 1.5
10 feet cable with battery ring,
terminals, fuse, and convenient
2 pin plug
Technical specs for this little solar box.
6
Copyright Boa Boy Productions 19196, 2008, 2009, 2010, Phil Heiple all rights reserved.
Frequently Asked Questions
1. How many appliances can I run off your system?
"How many" refers to the total number of watts required.
Different appliances use different amonts of watts. You don't need to know what a watt is; you only need to
count up how many total watts your appliances require. Your television, your laptop, even your hair dryer will
have a little nameplate somewhere listing how many watts, volts, and amps it takes. Sometimes it only lists the
volts and amps. To figure out the wattage, multiply the volts times the amps.
Here's the formula: Volts X Amps = Watts.
That will give you the watt hour load. For example, add up all the wattage on all the light bulbs you will be
running off it. Two sixty watt light bulbs means 120 watts. Add an inkjet printer (35 watts), computer (55 watts),
17" LCD flatscreen monitor (45 watts), and a cellphone (5 watts) and your office is fully running at 260 watts.
Get an inverter of at least 300 watts.
You will quickly learn how inefficient many of our everyday items are. For example:
Microwave 900-1500
Coffemaker 1200
Toaster 1200
Food dehyrater 600
Dishwasher 1450
Hairdryer 1500
Electric iron 1200
A sun oven could replace all of them for free. (Well, maybe not the hairdryer--I don't recommend sticking your
head in a sun oven.)
Other equipment:
10" table saw 1800
1/2" Hand drill 600
Vacuum cleaner 900
Laser printer 900
So the best thing to do is figure out your minimum needs, and then buy an inverter that at least covers that, or
better still, buy the biggest inverter you can afford. Then you can add on to it.
2. How long can I run them?
"How long" refers to the total number of amps required.
Again, you do not need to know what an amp is other than it is the unit for measuring how long your set up can
help you out. An amp hour (AH) is how many amps required to run it for an hour. A kilowatt hour (KWH) is
how many kilowatts are needed in an hour.
How many Watt-Hours in a battery?: Watts are pretty simple - it is just battery voltage times amp-hours. A 12
volt 105 AH battery can supply (under perfect conditions and to 100% discharge) 12 x 105, or 1260 Watt-hours
(1.26KWH).
Here's the formula: Amps = Watts/Volts
The amps listed on your appliance are probably listed in milliamps (mA) or thousanths of an amp. An alarm
Frequently Asked Questions Page 1 of 2
http://www.rain.org/~philfear/FAQ-Solar.html 11/16/2010
clock takes about one. A refrigerator will need a few amps. A toaster will take more amps than a refrigerator,
but runs for only a few minutes.
BUT, deep-cycle batteries can only be discharged to about 50% of their capacity without damage. In other
words, you can expect a 100 amp-hour battery to supply around 50 amp-hours of power between charge cycles
without suffering damaging.
THEREFORE: get a battery with twice the amps you think you'll need.
Then test your battery with a meter.It should always be in the 80-90% range. If you use a charger, then you
need to take a reading ONE HOUR after any charging cycle. It is important to wait this hour because all
batteries hold a surface charge that will give you a false reading after charging.
All deep cycle batteries are rated in amp-hours. An amp-hour is one amp for one hour, or 10 amps for 1/10 of an
hour and so forth. It is amps x hours. If you have something that pulls 20 amps, and you use it for 20 minutes,
then the amp-hours used would be 20 (amps) x .333 (hours), or 6.67 AH. The accepted AH rating time period for
batteries used in solar electric and backup power systems (and for nearly all deep cycle batteries) is the "20 hour
rate". This means that it is discharged down to 10.5 volts over a 20 hour period while the total actual amp-hours
it supplies is measured.
3. Can I run my refrigerator off your system? (No.)
Your refrigerator is too inefficient. As much as 20% of an average home's energy usage is for the frige. Even
small dorm-sized models draw too much for a practical solar system.
But you can invest in a 12-volt DC powered refrigerator. The best ones use zero maintenance, brushless,
thermostatically controlled DC compressors. They cost about half as much as propane refrigerators, with a
small one starting at about a thousand dollars.
You will also need a bigger panel; a 75-100 watt solar panel would do it for most.
Unless you live in the very cold northern latitudes having short days and low sun angles, most parts of the
United States will average 4 to 4.5 hours of direct sun per day during the winter months and 5 to 6 hours per day
during the summer months. Of course, some milder geographic locations may also have lots of rainfall and cloud
cover, which reduce these average hourly values. As an example, if you select a refrigerator or freezer that
requires 40 amp-hours per day to operate, this means you will need a solar array that can provide at least 10
amps output (40 amp-hour/4 hours) during the winter, and 6.6 amps output (40 amp-hour/6 hours) during the
summer. If your solar system will be used year-round, then you may want to use the smaller sun-hour value.
Since the ambient air temperatures are cooler in the winter than summer, all refrigerators and freezers will
require less energy to operate during colder months, so a more accurate winter calculation would use the amphour
load given for lower ambient temperatures.
Nova Kool and Sundanzer both make 12- and 24-volt DC powered refrigerators. Some are AC/DC. You can
order them from Solar Sphere.
Frequently Asked Questions Page 2 of 2
http://www.rain.org/~philfear/FAQ-Solar.html 11/16/2010
Some Nova Kool and Sundanzer both make refrigerators are AC/DC. (That would
be perfect for rolling blackout areas--most of the Third World. They live on AC
and then automatically switch over to the DC battery when the power goes out.)
But let me break down what else you will need.
A small 1.8 cubic foot capacity model REFRIGERATOR will require a 45 watt
solar panel, a 60AH battery, and a 15 amp charge controller.
A FREEZER is also 1.8 cubic ft. but requires a 110 watt solar panal, a 150 AH
battery, and a 15 amp charge controller.
A 8.1 cubic ft. capacity freezer gives you over four times the capacity at less than
twice the price but will require a 215 watt solar panel, a 300 AH battery, and a 15
amp charge contoller.
4. "Does it matter how thick my wires are? I put my solar panel on the roof and it
doesn't deliver as much power to my battery as before, when it got less sunlight.
Um...what's an ohm?"
These are all the same question. Electricity flowing through a wire must overcome
resistance to get from one end to the other. A thicker wire has LESS resistance than
a thinner one. A wire twice as thick has half the resistance. A longer wire has more
resistance than a shorter one. The amount of resistance is measured in ohms. When
one volt causes one ampere of current flow, the resistance is one ohm. You can buy
an ohmmeter to measure your ohms, but electricians mainly use them to find
defective connections.
DC electricity is more vulnerable to resistance than AC. That's why the battery in
your car has short, thick cables.
So, use wires as thick as practical. The wires from the panel to the battery should
be as short as possible. Carry the battery up to the roof if you have to. Then a short
connection to the inverter. And then a long line can go from the inverter to you
(because it is AC).
A digital multimeter will test ohms as well as voltage, current and other useful
stuff:
5. "In your instructions you say to buy a DC meter. What's it for?"
The DC meter lets you know how much of a charge you have in the battery.
Remember, you don't want it to discharge more than 50%. And you don't want to
damage it by overcharging. The DC meter (one of the settings on a multimeter)
will allow you to monitor the state of your battery.
6. "Can your system pasteurize water and milk?" (Yes)
The original question was "Can your system boil water long enough to make it safe
to drink?"
Yes, it can. But it is a myth that drinking water has to be boiled for ten minutes.
Pasteurization is achieved at a lower temperature for a shorter period. For both
water and milk (or anything) all the necessary germs (including E. Coli,
Rotaviruses, Giardia, the Hepatitis A virus, and Colera) are dead after having been
raised to a temperature of 160 degrees F (72 degrees C) for one minute.
Therefore do not waste the precious stored energy of the battery by bringing the
temperature up higher than you need to. Heating water is probably the most
inefficient use of this system. A sun oven would do the job more efficiently with
the sun rays--assuming it was in the daytime, sunny, and safe to go outdoors.
They work really good and are a lot of fun. But they cost about $240 each. They
reach 300 degrees F and higher. BUT, if all you want to do is pasteurize, a
homemade sun oven made out of cardboard and tin foil should be able to get you in
the right temperature range. Use a thermometer to be sure. Health care providers
will want to test their results. One way this can be done is with a nifty little device
called a "pasteurization indicator." You can get one for about nine bucks from my
friends at Solar Sphere.
"So with a few thousand cardboard boxes, a few hundred rolls of aluminum foil,
and the proper guidance the Cholera epidemic in Haiti could have been prevented
and 1,751 lives (as of Nov. 30, 2010) could have been saved?"
Yes. This is no joke.
BUT, if all you have is the solar power generator pasteurize with, here is the
smartest way to do it: First of all, don't use an inverter to power a microwave or
electric range. This will suck your battery dry very quickly. Instead, use direct
connections with the battery. There are a variety of devices that plug directly into
cigarette lighter ports. These range from little dip-in infusers to 20-oz. coffee pots.
And still the best way would be to monitor what you are doing and only raise the
temperature for as high as you have to for as long as you have to. These little
beasts take about 20 amps each. I have to warn you that these immersion heaters
are dangerous (the dip-in model can brand you) and the other two will permanently
self-destruct if you keep them plugged in without any liquid in them just once.
Copyright 2010. SolarLight Productions.
How to Make a Wind Turbine
out of a Hank-Crank
Flashlight
by Phil Heiple
SolarWind Press
2010
Using parts from a hand-crank flashlight and a few household items, you can make a
small wind turbine that generates electricity. You can even rig it up to recharge your
batteries. This is an easy to make demonstration device of self-sustaining nonpolluting
renewable electricity...
You will need:
One hand-crank flashlight
a very small phillips screwdriver
three nails
a wooden ruler
one rubber band
one pencil top eraser
one sheet of cardstock
a one-inch piece of dowel
some really good glue
A piece of cardboard for the rudder
A pole to mount it on
1. Get yourself a hand-crank flashlight.
2. Remove the tiny screws and open it up. one side has the crank and a nifty set of
gears. The other side has a circuit board with the generator on one end, battery, on/off
button, and LED lights on the other end. Lift out the circuit board.
3. The generator has a little gear on its back. I found it too short to attach a
propeller to, so I glued a short one-inch piece of dowel to it (I used Gorilla Glue).
Let it dry overnight.
4. Cut the generator off the circuit board, being careful not to break the wires going
from it. (I used wire cutters to snip through the plastic.) Turn it vertical and attach
it to the end of the wooden ruler with two small nails through the holes the screws
were in. Attach the rest of the circuit board flat to the ruler with a rubber band.
5. Stick the rubber eraser over the dowel.
6. Now the propeller. I made a simple pinwheel out of a page of cardstock that I
cut into a 8 1/2 by 8 1/2 square. Instead of a pin in the middle, I stapled the flaps in
at about a inch from the center. Then I cut a small square in the exact center,
slightly smaller than the eraser. Then I gently pushed the pinwheel over the eraser
and it locked in place.
7. Blow at the pinwheel. It should spin freely. You are in business.
8. Make a rudder for the other end of the ruler. I used a scrap piece of foamcore
about ten inches by seven inches and just cut a slot in it and slipped it over the
ruler, which had a useful groove down the middle. The rudder fitted nicely without
any glue.
9. Find the center of balance by balancing it on your finger. Drill a small hole at
the balance point. Get a pole and attach your wind turbine to the post with a flat
head nail smaller than the hole. Be careful to only hammer the nail in so far. Wind
turbine should rotate freely.
10. Take your wind turbine outside. A gentle breeze is all it takes to get it spinning.
The battery was as dead as a doornail when I started. After 30 minutes of spinning,
I pushed the on/off button. Viola! The LED lights lit up!
How to Recharge Your Batteries
How to Recharge Your Batteries: recharge your batteries by taping them to the
ruler and then running wires from their poles to the leads going to the 3.6 volt
battery. Connect positive to positive; negative to negative. Line your batteries up
positive to negative. Two AA or AAA batteries (1.5 volts each) can be recharged at
a time. Unlike a charger plugged into the wall, recharging this way doesn't use
electricity generated by coal, other fossil fuels, or nuclear power.
Strong, gusty winds will tear this apart. So will rain. So try making the pinwheel and
rudder out of tin or plastic. And cover up the exposed circuits with a styrofoam cup
cut in two or a plastic bag.
Putting washers above and below the ruler on the nail will help it rotate around the
pole.
You can glue the propeller and rudder on. Make a better propeller.
Attach it to your bike and recharge your batteries as you pedal.
By Phil Heiple copyright 2010 SolarWind Press