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reviewed by Larry D. Barr

I read a book last weekend. Now, this is certainly not out of the ordinary. I read a lot of books. Some of them, like Stephen King’s The Stand, I read about once a year. And I’ve probably read almost everything Martin Caidin ever wrote four or five times. Or more. However, the book I read last weekend is certainly out of the ordinary.

It’s called Homebrew Wind Power – A HANDS-ON GUIDE TO HARNESSING THE WIND. The book is written by Dan Bartmann and Dan Fink, a couple of guys who live (and create wind turbines) in a small off-grid community somewhere up in the north-west part of Colorado. A few years ago, when I was the editor of an online publication called Energy Self Sufficiency Newsletter, Dan Fink was one of our regular columnists, writing under the handle of “The Wind Bag”. DanF, as he’s also known, proved himself very adept at sharing his vast knowledge and his insights into the vagaries of the wind, and the various ways it can be captured and cajoled into sharing some of its energy (but never more than 59.26%) in the form of usable electricity.

The Two Dans have been working on this book for several years, and about two weeks ago I got an email from DanF asking me if I’d like an ‘advance review copy’ to look over and possibly share my reactions with y’all, the readers of Rebel Wolf Online. Of course I said “Yes” and the book arrived in a few days. As I removed the book from the bubblepack envelope, it was immediately apparent that this was a quality tome. It’s 8” X 10”, with a soft 12 point C1S cover (C1S is printer talk for Coated with plastic on 1 Side), and contains 320 pages of 100% post consumer waste recycled paper, a spectacular cover shot of a wind turbine
flying in a Rocky Mountain sunset and more appendices than the Dionne quintuplets.

I don’t necessarily consider myself a wind energy expert, even though I lived off-grid for about 19 months back in the ’70s with a Wincharger 1222H as my main source of power. However, I’m pretty well versed in the overall discipline and so I wasn’t sure just how much I’d learn from this volume. I learned a hell of a lot.

Mick Sagrillo’s foreword, written in Mick’s usual “if you didn’t want the answer, why’d you ask the question?” style, will be a real eye-opener for the renewable energy newbie who thinks that wind power is a simple “plug and play” experience. Mick Sagrillo is one of the ‘gods’ of renewable energy and getting Mick to write the forward for your book is a lot like Enzo Ferrari looking at your home-built car and saying, “You done good, Kid.”

The first four chapters, which cover wind energy theory, basic electricity and elementary magnetics are intended to bring the wind energy neophyte ‘up to speed’, and basically served only as a review for me. I’ve always been comfortable with the theories and math of renewable energy. And ten years as a working electrician gave me a very solid grounding (sorry) in the electrical department.

When I got into Chapter 5, “Furling and Regulation” my wind turbine education truly began. You see, my little Wincharger didn’t furl – it just had a couple of centrifugally activated flaps that came out when the wind speed got too high and slowed the rig down to a hopefully safe speed. Anything faster than that and I was supposed to be home and physically set the brake and secure it. Primitive yes, but it was a 1930s era design and it worked fine in the area I was living in at the time.

However, that’s not the way it’s done anymore and The Two Dans have designed and implemented a virtually fail-safe mechanism for the self-protection of their wind turbine design. In the interest of historical accuracy, I should mention here (as The Two Dans acknowledge repeatedly in the book) that the original axial-flux design didn’t originate in the wilds of Colorado with DanB and DanF.

The credit for the original concept goes to Hugh Piggott, another of the gods of renewable energy. Hugh lives in Scoraig, Scotland, many kilometres beyond the reach of the grid and pioneered a radial-flux wind turbine design built from old truck brake drums., which was the first homebrew design to have a furling tail. Then, as the price of neodymium magnets came down, Hugh invented the axial-flux design. Remember that Hugh’s initial challenge was twofold.

First, to electrify the little settlement of Scoraig. His second challenge was to devise a turbine that wouldn’t self-destruct in the vicious winds coming off the North Sea at N 57° 55′. Now, I’ve never been to Scoraig, Scotland. But my friend Ash lives at N 55° on the northern coast of Ireland, and we’ve clocked winds of better than 80 mph at his house. I don’t imagine that things calm down any almost three degrees of latitude further north. So Hugh had his work cut out for him. And he met the challenge brilliantly. Before long, Hugh was traveling the world, giving hands-on workshops for building turbines and bringing electricity to places where it had never been before.

The Dans attended one of Hugh’s workshops in the US and liked it so well they went back for more. After a couple more sessions under Hugh’s tutelage, they got back to their shop in the wilds of the Rockies and started thinking and tinkering and making a few changes here and there. DanB came up with the idea of using Volvo disc brake rotors one cold, dark night and as the process continued, one change led to a couple more — ad infinitum — and the turbine that’s detailed in the book is something like “iteration n+1” and generations removed from Hugh’s original, primitive radial-flux wind generator.

Chapter 6 of the book, “Shop Safety” is an absolute must-read chapter. I don’t care how long you’ve had a shop, worked in a shop or if you’re a rank newbie at building anything. Read this chapter. Then go back and read it again. It will keep you, and those who help you, from getting hurt. As you build your wind turbine, you’ll be working with all kinds of things that can hurt you badly. The magnets used in the turbine are among the strongest, most powerful magnets this side of the Large Hadron Collider and and if you let your hand get in between the two magnet rotors, the resulting collision will turn your fingers to Alpo. So pay attention. The chapter is broken down into sections regarding the safety procedures for each step of the build and each fabrication process you’ll be using. One of the good points that’s made in the
metalworking section is to treat every piece of metal that’s been cut, welded or ground, as if it’s hot. Mighty fine advice. However, I’d recommend that you also do what we always do in my shop. Once you’re done grinding, welding or cutting on a piece, just take your soapstone marker and write “HOT” on the piece in big letters. It might have cooled off by the time your co-worker goes to pick it up, but it’s much better to treat a cold piece of metal like it’s hot than the other way around.

Chapters 7 through 18 take you step by step and piece by piece through the entire process of building your own axial-flux wind generator. Each chapter, each step, each process is illustrated with photos of the components. As you learn what to do and how to do it, you also learn what not to do. The Two Dans also do a wonderful job of of explaining why you’re doing it that way.

Knowing why you’re doing something is vital in a process of this nature, because it gives you a solid foundation in the subject and prepares you for the sometimes not-so-simple task of living with and maintaining the wind monster you’ve created. Even if you’re consumed with an almost overwhelming haste to get the rig in the air, don’t skip over the ‘why’ parts of the book. You’ll need them later.

Chapter 19 is titled “Failures and Prevention”. It’s a machine. It can fail. There are a lot of things that can go wrong with any complex mechanism. This chapter details what to watch for – those little signals a machine gives to let you know that all is not well. The proper maintenance methods are described and, again, illustrated with myriad photos. There’s a very informative section with pictures of machines that have failed, along with a bit of failure analysis so you know why it happened and how to avoid that failure mode with your machine. The chapter concludes with a section on Troubleshooting. You built it, so nobody knows that machine better than you do. You’re also the one that’s going to be repairing it if something goes wrong. Nobody’s better qualified.

If you’re not satisfied with the 10 foot turbine described in the building process in the book, Chapter 20 “Scaling it Up and Down” may be for you. It describes a 17′ unit and also a downsized 7′ turbine. These two units are not as far along in the development process as the 10 footer that we build in this book. The guys have built and flown a few of them, but they don’t have near the hours in the air that the 10 footer does. I’d recommend building the 10 foot turbine first and getting some first-hand experience before setting off into less-charted waters. However, there is some advanced theory in that chapter that will certainly improve your technical understanding of the subject whether you build a larger or smaller unit or not.

Of the remaining two chapters of the book, one is devoted to sources of information, supplies, components, kits, towers, web resources and just about anything else that’s wind energy related.

Chapter 22 is the Glossary wherein you can find definitions for most every wind related term from “AC” to “Zymurgy”. The latter being one of my favorites.

Six appendices round out the book and contain information on tap drill sizes, wire gage, those sometimes pesky metric to English conversions, tools, wind data and other just generally useful brain fodder. I was gratified to see in the production credits that the book was almost entirely produced using free, open-source software. I believe that open-source software will be the force of the future and the fact that a book of this quality can be produced using OSS is proof that the free software movement is coming of age.

Dan Bartmann and Dan Fink have done a magnificent job in the writing and production of Homebrew Wind Power. They’ve created a book, written with a vast amount of knowledge and experience in the subject, loaded it with photographs that clearly show the processes involved and enabled any wind energy amateur to successfully build his or her first wind turbine and enjoy the rewards of living off-grid. The writing style vividly demonstrates that The Two Dans enjoy what they do and while they take the subject of wind energy very seriously, they never take themselves too seriously. They have fun building wind turbines and it shows in the book.

Do I have any grumbles about the book? Just one. I live on a 70′ X 100′ lot in the city and I don’t have room to fly one of these turbines even if I built one. I’d need a tower bigger than the lot to get above the trees. So, here’s a book that’s got me all fired up to build a wind turbine and I’ve got no place to fly it. What a book! I heartily recommend it.

By the way, you’ll love the “Dog Haiku”.


The Ultimate DIY Wind / Electrical Resource

Want to learn how to build a wind turbine, not sure about amps, watts, volts, etc.? There is one source that explains it all in an easy to understand method. You will learn everything you need to design, build, and use the power from your own wind turbine, at a fraction of the cost of a commercial unit. I’m not talking about those cheezy 3′ units, I’m talking about whole house sized units.

Dan Fink and Dan Bartmann wrote the definitive resource on DIY Wind Turbines. It’s called Homebrew Wind Power, and we feel it’s the best resource on learning the basics, and getting the full story of hands on wind turbine design.

A Hands-on Guide to Harnessing the Wind

Have you ever wondered how wind turbines work and why they look like they do? Are you interested in adding wind power to your off-grid electric system, but have been put off by the high cost of equipment and installation? Well, now you can build and install your own wind turbine!

Harnessing the wind can be a tricky business, but in this groundbreaking book the authors provide step-by-step, illustrated instructions for building a wind generator in a home workshop. Even if you don’t plan on building your own turbine, this book is packed with valuable information for anyone considering wind energy. It covers the basic physics of how the energy in moving air is turned into electricity, and most importantly, will give you a realistic idea of what wind energy can do for you–and what it can’t.


SXM Needs to invest in wind and solar energy

St. Maarten, “Today”, Monday June 9th, 2008


GREAT BAY – We haven’t seen anything yet as far as the global energy crisis is concerned, says Steve Spence, director of New York-based Green Trust. “Gas at the pump is now around $4 a gallon in the States, but within three years I expect to see prices like $10 a gallon. We have to conserve; there is no other solution. Renewable fuels will not solve the problem, simply because we are unable to plant enough crops to produce a sufficient amount of bio-fuel.”
What does this mean for St. Maarten? The price of gas has just gone up to Naf. 2.50 ($1 .404 per liter). If the price were to follow the trend Spence predicts for the United States, motorists would be paying Naf. 6.25 ($3.51) per liter by the year 2011 –  and that’s right around the corner. Such fuel prices will have a serious impact for the island, not only on motorists, but also on our whole energy supply system. “St. Maarten will have to invest heavily in solar and wind power,” Spence says. He outlined his vision on St. Maarten’s energy-future Saturday evening during an exposé at Enviro Week in the Emilio Wilson Park. Spence, 43, has been living off the grid for five years now, meaning that he does not buy any energy from a utilities company back home. He is an IT engineer and an electronics technician who describes himself as a green conservative. “I probably would have been a hippie in the 60’s if I had been old enough,” he says on his web site. Spence lives off grid, powering his energy needs with solar and wind energy. As a back up, he uses a diesel generator that runs on vegetable – oil.


Production is down, demand increases

Spence’s view on the future of the energy markets hinges on two principal observations. First of all, the emerging economies in China and India result in a higher demand for oil. Arab countries also start using more oil. At the same time, world oil production has peaked in 2006, and is now in decline. To sum up: demand is increasing, and production is falling. That makes oil –  and by extension gas at the pump, and the traditional production of electricity – more expensive. “There will come a moment when you will not be able to buy oil at any price,” Spence says. “So you need alternatives for the moment when oil is no longer available.” In St. Maarten, utilities company GEBE produces electricity using diesel generators. Last year, the company invested. $31.9 million in two new Wartsilä diesel generators that will be delivered to the island next year; they will become operational in 2010. If Spence’s doomsday scenario becomes reality, the island will have to invest in alternatives –  and fast. Sun and wind energy are two untapped resources, the New Yorker says. One wind turbine can produce enough electricity for 700 homes.”
Twenty wind turbines

There are approximately 13,500 homes on the Dutch side of the island. To cover all energy needs with wind power, GEBE would have to install 20 wind turbines with a production capacity of 2.3 Megawatt each. The investment would be somewhere in the neighborhood of $94 million, or 167 million guilders. What if GEBE does not jump on the bandwagon? Spence: “This island enjoys plenty of sunshine and there is plenty of wind too. It blows my mind that not every home in St. Maarten has at least one or two solar panels on its roof. Why this is so, I do not know.”  Spence also discovered a misconception about solar panels. “Many people think solar panels are only fit to heat water. But there are also solar panels that produce electricity.” If GEBE, for one reason or another does not make the switch to wind energy, citizens have the option to take their own measures. “I can install a 1000 watt residential wind turbine for $1,000,” says Spence. “They are not hurricane resistant, but there is a solution for that situation. When a hurricane approaches, you crank down the turbine tower and when the weather improves, you crank it up again.” Investing in wind energy does not mean that diesel-powered systems have to be discarded. They can function as back up. In remote locations, wind energy is a cost-effective alternative for grid-extension. Private investments in wind energy do not have to cost homeowners any money. They can finance their investment and pay off the loan to the bank in seven to ten years in installments they would otherwise have to pay to the utilities company. “You don’t pay more money every month, but you are disconnected from the grid,” says Spence.


The decline in oil production and the world’s ever-increasing demand make the need for conservation more pressing, Spence says. Energy efficient lighting and vehicles and insulated homes have to be part of the solution. “People will also have to consider car pooling, and limit the amount of trips they make with their cars.” Another energy-saving method is eliminating what Spence .calls “phantom loads.” This is the energy electrical appliances like TV’s, VCR’s and computers consume in stand-by mode. “I connect these appliances to an electrical strip and when I switch the strip off, they do not consume anything anymore,” Spence says. St. Maarten is also an ideal environment for the introduction of electric cars, Spence points out. “I could build an electric car with a range of around fifty miles that performs better than a gasoline-powered vehicle, even when it has to go up steep hills.”

Paul Mooij, founder of the Caribbean Foundation for Sustainability (CFS) that organizes Enviro Week, told Today that his organization will write a pressing letter to the Executive Council to draw its attention to the looming energy crisis and the possible solutions for St: Maarten.
For more information about living of the grid and other alternative energy solutions, go to




One could of course argue that Green Trust director Steve Spence has a product to sell and that we ought to take his message about soaring oil prices and the subsequent consequences for energy supply in St. Maarten with a grain of salt.
The Dutch Prime Minister Colijn famously told his citizens in a radio address on March 11, 1936, “I request that the listeners, when they go to bed, go to sleep as peacefully as they do on other nights. For the time being there is no reason whatsoever to be really concerned.”
These lines, later condensed to the more accessible term, “Why don’t you all go to sleep peacefully”, are often mistakenly contributed to Colijn on the eve of Germany’s invasion. In reality, Colijn spoke the words four years earlier, a couple of days after Nazi-Germany cancelled the treaty of Locarno, and after Hitler began to militarize the Rhineland.
Looking back, the four years that passed between Colijn’s unfortunate assessment and Hitler’s attack on the Netherlands, seem like an awfully short time. The Dutch had every reason to be concerned about Hitler’s activities. Had the government inspired them to take measures, many lives could have been saved. But the why-don’t-you-go-to-sleep-peacefully speech gave citizens a false sense of security.
A few years later, the Dutch government was off the mark again, when it told citizens how to deal with German firebombs (pick them up and stick them in a bucket of sand). Images of Rotterdam’s bombardment did not stop the government from repeating this type of ridiculous advice for a nuclear attack at the height of the cold war (cover yourself with a white sheet).
In other words, history proves that governments are not the reliable partners they ought to be. How does this relate to Spence’s predictions about the energy market and the way St. Maarten ought to react to it?
We let our readers be the judge of that, but it is almost certain that the energy markets will at least move in the direction that Spence has indicated.
That ought to be §sufficient reason to jump into action and to review the way St Maarten meets the community’s energy needs thoroughly. How our government will react to the situation is anybody’s guess. It will be a rainy day in hell when oil prices drop back to that idyllic level of $25 a barrel. That is not going to happen, ever:
Will it get worse? All indicators point in that direction.
Do we have alternatives to fend of the consequences of Spence’s doomsday scenario?
To make those alternatives a reality we need political awareness first, followed by the political will to create solutions for the future that makes the island less dependant on a commodity that becomes scarcer every day. That future is not a next-generation thing; it is right around the corner.
It brings to mind the American expression, “the light is on, but there is nobody home” – a reference to somebody who is mentally not all there. If we do not tackle the energy issue in a decisive manner, Country St. Maarten could end up in a situation where “everybody is home, but all the lights are out.”
For sure, nobody wants that to happen.




Homebrew Wind Power

Our favorite (and in our opinion, the best) DIY guide to off grid power systems and DIY wind turbine construction has to be “Homebrew Wind Power” by Dan Bartmann & Dan Fink. It’s a complete guide to low voltage dc power systems and a good electronics tutorial in addition to being a step by step guide to producing free electricity with the power of the wind.

“Have you ever wondered how wind turbines work and why they look like they do? Are you interested in adding wind power to your off-grid electric system, but have been put off by the high cost of equipment and installation? Well, now you can build and install your own wind turbine!

Harnessing the wind can be a tricky business, but in this groundbreaking book the authors provide step-by-step, illustrated instructions for building a wind generator in a home workshop. Even if you don’t plan on building your own turbine, this book is packed with valuable information for anyone considering wind energy. It covers the basic physics of how the energy in moving air is turned into electricity, and most importantly, will give you a realistic idea of what wind energy can do for you–and what it can’t.”

Get the book here

Homebrew Wind Power

and if you email us your Amazon order confirmation, get the DIY ebook package of your choice from

absolutely free.

To learn more about electronics, and how to monitor off grid power systems and control devices, see


More residents getting “sick” from wind turbines?

The residents of the town of West Lincoln, Ont.  are reporting a variety of stress related illnesses they attribute to a wind farm nearby.

“‘It’s too late, two years too late,’ said Helen Kzan … ‘I’ve been to the doctor. They told me to move. My stress level has skyrocketed. My physician told me my stress will kill me before the wind turbines.”

Many people attribute these illnesses to the reported sounds, vibrations, and light patterns made by the moving blades. What’s wrong with this picture?

The wind farm hasn’t been built yet.

These people are reacting to the anti-wind advocacy groups reports on what they think will happen. It’s not wind turbines that make you sick, it’s listening to the lies and made up statistics of the anti-wind groups.  It’s their own fears that are making them sick, and the anti’s are creating self fulfilling prophecy.



A New View of Energy Efficiency:

How the “Hybrid Home Guy” Uses Andersen Windows to Change the Conversation about Green Building

Adam Bearup was finished. After years of pushing architectural envelopes to encourage more people to change the way they were living to more earth-friendly practices, the “Hybrid Home Guy” recognized his own energy inefficiency: rather than pursuing a truly revolutionary style of building that would not only earn attention but also have less impact on the planet, Bearup was chasing projects to help keep people employed.

Yet as he began planning a sabbatical to re-focus his energies, fate intervened – and wouldn’t take no for an answer. The project would become known as Earth Shelter Michigan; a grouping of five underground domes designed to function completely off the grid. Bearup said “no” four times. There were serious budget and location concerns. But when the owner came back a fifth time, he recognized this was the envelope he had to push and said yes to a career-changing project.

Earth Shelter is comprised of a campus of domes to help the family live as self-sustaining as possible. The five domes each have a purpose: a main house dome where the owners will live; a greenhouse to grow produce; a small “parents’ quarters” dome; another dome with walk-in freezer and pantry space; and a 72-foot-long barn dome that will include stalls for animals living there. The square footage adds up to 12,000 including the barn. Yet with a 48-volt battery bank that is charged by solar panels and a back up generator — and owners willing to carefully budget their energy consumption — the entire campus will run off the grid.

The domes are all underground — some spots measuring 35 feet below the surface – while one end is strategically positioned for passive solar exposure. But Bearup designed each dome to feel as though it’s sitting above ground. With a creative layout and use of paint colors, Bearup and his team helped natural light streaming through the windows on each façade reach back into the farthest points of the domes.

From the perspective of building science, windows are the most important part of a building’s shell for Bearup. Solving that issue in an environmentally friendly way was key.

“Windows have an incredibly important job to do at Earth Shelter, but it’s the same for any house: create, capture and contain energy,” said Bearup. “If we use the right windows and exterior envelope, we can keep each dome at Earth Shelter a few degrees within the 70 degree range without running the heating or cooling system.”

For Bearup and his team, Andersen Windows was his solution to the weather found in Northern Michigan: wind-driven rain, hot summers, bone chilling winter temperatures, all elements that can take their toll on a structure.

“We’ve used Andersen 400 Series in other houses, so based on our knowledge of its performance standards, along with blower door tests and various industry certifications, we knew these windows really performed,” Bearup explained. “The flashing components of the 400 Series really impressed us, and their construction is so tight, the homeowners won’t have to worry about maintenance and there’s virtually no chance of rot on the frame.”

A total of 26 windows and four outswing French doors were installed throughout the domes.

In addition to its building attributes, Bearup also ordered the windows to have a good degree of Forest Stewardship Council (FSC) wood content. Andersen has FSC Chain of Custody certification, which Bearup said was also important in choosing the windows. He liked that Andersen heats and cools its manufacturing facility by burning its own wood byproducts in a steam generating facility and even is converting some of its trucking fleet to run on compressed natural gas, which lowers emissions.

“Not only did we want to put in a great product from a company that’s been around a long time, but we wanted to make sure the products aren’t destroying the environment through their creation,” said Bearup. “We were very impressed with how similar our thoughts on this were, and what Andersen does to really respect and nurture the wood they use and the environment they work within to only make it better.”

As work wraps up on Earth Shelter, Bearup can see how his views of environmental homebuilding have changed for the better. And that’s started conversations with others who want to create their own Earth Shelters and, Bearup hopes, shift their views of a home’s 21st century utility.

“Houses can function as part of a larger system that works together,” Bearup explained. “It complements a healthy lifestyle in the way the home breathes and lives. Earth Shelter is a living, breathing entity. And what I hope to show everyone out there is how – rather than being a repository of things – a home can encourage you to live. To let in the things we need to help us grow and thrive, like the light shining through the windows, to be aware of what’s around you. If it helps introduce a mindfulness that I believe is missing among so many homes today, then we have changed the world for the better.”


Taming the hype: Beating Betz?

Travis and his girls are off getting a horse in Arkansas this week, and we are going back home to see the kids and our new granddaughter for Christmas. Paul Gipe brings you the following :

By Paul Gipe

Poor Albert Betz, the German physicist must be turning over in his grave. He’s been beaten yet again.

Seems like it is becoming almost a weekly occurrence now that some inventor or another announces they’ve beaten the Betz limit for the aerodynamic performance of wind turbines. The latest is the so-called Windtamer from Livonia, New York.

Betz, following in the footsteps of his British colleague Frederick Lanchester, calculated that the theoretical maximum energy a wind turbine rotor can extract from the wind is 59% of the energy in the windstream.

Windtamer says they not only beat Betz but they will produce twice as much as a conventional wind turbine. However, a quick scan of the “report” justifying Windtamer’s claim reveals that the turbine’s performance is not any better than all those wind turbines that have gone before.

But first, the famous press release.


3kW 17-foot Wind generator, and you build it yourself!’s latest project

3kW+ output, 48VDC, 17-foot diameter wind turbine built from scratch. Low winds don’t have much power available in them. The only way to harvest a useful amount of energy from low winds is to sweep a large area with the wind generator blades. This turbine charges a 48V battery bank in 5 MPH winds, is making 400 Watts at 10 MPH, and 1500 Watts in a 16 MPH wind. When fully furled, this machine produces maximum power of 3800 Watts. The tail folds up and in during high winds, yawing the machine at an angle to the wind to reduce the massive, exponential, power input increase from high winds. The machine has survived 60+ MPH winds in operation.


Bogus Wind Turbine Marketing Claims

Once again we are hearing from folks some pretty wild claims about marketers trying to sell wind turbines with some fantastic outputs, outputs that are in the realm of science fiction (Honeywell Windtronics especially). If you know the blade length, it’s pretty easy to determine how much power you can realistically produce. Check out out calculator here and do some what if scenarios with wind speed and blade length –

Also See Paul Gipe’s review and explanation at


RENEWABLE POWER FOR AMATEUR RADIO (and other electronic devices)

RENEWABLE POWER FOR AMATEUR RADIO (and other electronic devices)
by Larry D. Barr, K5WLF

About the author: Larry D. Barr is an Amateur Extra class amateur radio operator, first licensed in 1966. He is uniquely qualified to write on this subject, having lived offgrid for 19 months with the majority of his electricity provided by a Wincharger 1222H wind generator. Larry is a journey level electrician, an alternative energy systems designer and the former editor of Energy Self Sufficiency Newsletter. His pickup mounted, solar powered ham radio installation was featured in the American Radio Relay League’s “We Do That” video series and on their website. Currently employed as the Planetarium Manager for Tarleton State University in Texas, Larry continues to be active in renewable energy and looks forward to living offgrid again in the near future.

Because of my interest and involvement in renewable energy, I’m often asked by other amateur radio (ham) operators about the best way to run their stations on renewable energy sources. Most of these queries pertain to solar, or photovoltaic (PV), sources, but we’ll also mention wind and minihydro in addition to PV in this article.

The good news is that modern, solid state ham rigs lend themselves extremely well to renewable power. They draw relatively little current at a nominal 12 VDC, and therefore require fairly modest expenditures in generating devices.

The bad news is that hams who like the old vacuum tube (hollow state) rigs will not be able to power those old “boat anchors” without a serious layout of funds for PV panels or a much larger than usual wind generator. The old rigs simply draw too much current to be practical for operation on a renewable system.

So, let’s look at the practicality of running a modern, 100 watt, solid state transceiver like my Yaesu FT897D on a PV system. It’s easy to do – and at a relatively low cost for the solar setup.

First, let’s consider the power required to operate the radio. There are two distinctly different current requirements for the unit. One is the power required for the radio to receive incoming signals. That’s about one ampere (1A) at a nominal 12 volts direct current (12 VDC). Nominal 12VDC turns out to be somewhere in the vicinity of 12.6 VDC, for a fully charged 12 volt battery, to around 13.8 VDC which is the output of an average vehicle alternator. We’ll mostly stick with 12 VDC for this article just to make the calculations easy.

The other requirement is 22A while transmitting at the full 100 watt output level. Well, you’d think that wouldn’t take long to run down a battery, and you’d be right. But think a minute. We don’t transmit all the time. Actually, the ratio of transmit to receive in normal ham operation is right at 1:9. 10% transmit and 90% receive.

Now, we need to figure out how many Amphours (Ah) we’ll use per clock hour in normal operation. Amphours is the numbers of amps, the current, consumed over a period of one hour. It’s the way the battery capacity is rated. As I said earlier, normal radio operation is generally calculated at 90% receive and 10% transmit.

So, in 1 clock hour we’re consuming:
(1A X 0.9h) + (22A X 0.1h) = (0.9Ah + 2.2Ah) = 3.1 Ah

Figuring our 100Ah battery at 50Ah, because we don’t ever want to take the battery below 50% depth of discharge, we divide:
50Ah / (3.1Ah/hour) = 16.129 hours

Which is about 16 hours and 8 minutes from a fully charged battery. I run two 100 Ah sealed lead acid (SLA) batteries in my battery banks for a rated 200 Ah capacity and a ‘real world’ capacity of 100 Ah. That doubles my run time to about 32 hours and 16 minutes.

There are those who will disagree with me about my advice to never exceed 50% depth of discharge in a deep cycle battery. They are welcome to do so. And I will never loan one of those folks my batteries. Your batteries will last much longer and provide better service to the end of their life if you follow my advice. Each time a battery is drawn below 50% charge, it gives up a small part of its longevity. Personally, I can’t afford to replace batteries before the natural end of their life. So, I treat them well. My shack and pickup batteries are over six years old and still operating at peak efficiency.

I must mention here that manufacturers base the capacity ratings of their batteries on the assumption that the discharge will be made at a constant rate. That rate is assumed to be one twentieth (1/20) of the published Amperehour rating of the battery. In the case of our single 100Ah battery, the rate would be 5A. For our 200 Ah bank, it would be 10A. This relationship is called C (capacity) / 20. You’ll see it published simply as C/20 or ‘the C/20 rate’.

Any deviation from this C/20 rate, especially discharge rates which exceed it, will result in a different amount of power available from the battery. If we exceed the C/20 rate, the capacity of the battery will be less. In many cases, much less. It depends on the extent to which we exceed the C/20 rate of discharge.

In the case of our 100 Ah example, since our calculated rate of discharge was 3.1Ah/hour (or 3.1A), we were below the C/20 rate of 5A and should get at least the run time we calculated. However, if we were to exceed the C/20 rate, our run time would be less. How much less would be proportional to the amount above the C/20 rate that we imposed on the battery. If our discharge rate is below C/20, we may get a bit more. But let’s figure for worst case and not count on it. This phenomenon has been well documented by a gentleman named Peukert and his analysis of the effect is known as Peukert’s Theorem.

We should note, and must accept, that this does not indicate that the battery is faulty. It’s simply reacting in accordance with the laws of physics and chemistry that batteries operate under. To draw an analogy — if you bought a car and the manual stated that you could expect 25 MPG at 50 MPH, it would be unreasonable to expect that same mileage at 120 MPH. You’ve changed one of the variables in the equation and you can’t expect the result to be the same.

Now, let’s look at the PV panels and other gear required to support our FT897D on a solar electric diet.

My system consists of two UniSolar US64 amorphous panels rated at 64 watts each. They’re connected in parallel for a total of 128 watts. With the Xantrex C12 charge controller set at an output voltage of 14.2VDC – it seems high, but it’s right for the SLA batteries – that gives me about 9.01 amps to the batteries. Let’s just call it 9 amps. So, in one clock hour, I’ve put 9 amphours back into the batteries. That’s almost a 3:1 ratio of input to output.

Truth be told, I usually see about 7.4 amps, more or less, from the panels going into the battery bank. But that’s more than twice what I’m using and certainly explains why, on occasion, I’ve gone out on a radio mission with less than fully charged batteries, worked on the air for four hours or so and returned home with a fully charged battery bank. And all free, from Mother Nature.

My UniSolar panels aren’t available anymore. Unisolar has decided to dedicate their manufacturing capability to mainly Building Integrated PhotoVoltaic (BIPV) and has discontinued their line of discrete PV panels. We recently mounted a Kyocera 235 watt panel on our local ham club’s tower trailer, and if I were buying now that’s what I’d get for myself.

Let’s look at the total cost of a PV system to run the radios using the Kyocera panel.

The PV panel will run you about $375, the Schneider/Xantrex C35 controller with the CM digital display (recommended) is about $165, and a pair of PowerSonic 100 Ah SLA batteries will round out the system for $275 each or $550 for the pair. That’s a total of $1090 for the system. With proper care, the panel and the controller will last you for a lifetime. The life span of the batteries depends on you. I’ve been running mine for about six years now, and they’re still doing their job, and doing it well. If you abuse them, by discharging them below 50% capacity, or over or under charging them, their life span will decrease.

Now, let’s talk about wind power for a minute. If I were buying a wind generator today, I’d get an Air 30 turbine made by Southwest Windpower. It’s a 400 watt unit and has all the controller circuitry built in. At peak output, it’ll give you somewhere around 25 amps, and because of the integral controller, it interfaces seamlessly with a PV system. Cost is somewhere in the neighborhood of $600. If you live where wind is one of your most prevalent natural resources, you might get by with just the Air 30, but I really recommend a hybrid system that uses more than one source. Wind and PV is a great combination, for many times when the wind is blowing the most, the sun is obscured.

Minihydro is a wonderful power source if you have a year round watercourse on your property. If you don’t, just forget about it. My dream is to find a property with a year round stream on it, but unless I win the Lotto and maybe leave Texas (not likely), I’ll never find it. Don’t even fret over hydro unless you can provide your system with a reliable and continuous source of water. There aren’t many locations available with that resource and it’s best to not even think about it unless you already own it. If there’s a call for it, I’ll gladly write about minihydro at length in a future article.

OK. let’s summarize. I’ve explained how to calculate the draw of your radio. We’ve discussed the factors that control battery run time and battery life. We have talked about the initial cost of a PV system, and considered adding a wind turbine to the system. It’s easy to add other 12VDC devices, such as lighting or entertainment devices, to the system. Just do your calcs and ensure that you’re not drawing your battery bank below 50% capacity. Be sure to follow all appropriate wiring codes and make damn sure that your wiring is safe and overload protected. Enjoy the free energy that Mother Nature provides. ldb

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