Build a solar heater

Build a solar heater

By: Gary Reysa (www.builditsolar.com) © Gary Resa 2005
After walking into our new workshop one December morning and finding the inside temperature to be a bone-chilling 10°F (-12°C), I decided that it was time for a heating system! Given the rising costs of propane and our environmental concerns about using nonrenewable fossil fuels, a solar solution seemed fitting. I reviewed many solar collector concepts, and finally decided to install a thermosiphon air collector on the south wall of the building. The concept is elegant and simple. A thermosiphon design uses only the buoyancy of heated air to circulate air through the collector, eliminating the cost, maintenance, and energy consumption of fans, sensors, and controllers commonly used in other collector designs. On a sunny day, in a cold climate like ours here in Bozeman, Montana, this simple system can produce the heat equivalent of burning about 2 gallons (8 l) of propane. To minimize material use, I integrated the collector within the building’s structure. I also tried to make the collector easy to construct using readily available materials. In fact, making this collector should only take one trip to the hardware store and US$350. Set aside two or three days to complete the project.

Materials used to construct the thermosiphon collector can be found at most lumberyards and hardware stores.

How It Works

The thermosiphon collector consists of clear, corrugated poly carbonate panels fastened to vertical 2 by 6s. The clear panels, on the building’s south face, admit sunlight. An absorber—in this case, two layers of black metal window screen—suspended inside the collector captures the sun’s

heat energy. The air around the mesh expands and rises as it warms, creating a convection current. Vents located at the top and bottom of the collector allow air to circulate and become heated. Cool air enters the lower vent, is heated by the absorber, and rises through to the upper vents that exit into the building’s interior. This circulation of air continues as long as the sun shines on the collector. At night, as air in the collector cools to outside temperatures, airflow tries to reverse. Air in the collector sinks through the bottom vents and attempts to pull the warmed air from the building through the top vents. Use of flapper valves on the top vents helps prevent this reverse circulation and keeps the heat inside.

Nuts & Bolts

The collector is 20 feet wide by 8 feet high (6.1 x 2.4 m) for an overall area of 160 square feet (15 m2). The collector is 6 inches (15 cm) deep. In most cases, make the collector as large as your south wall allows (see sizing solar collector). The top vent and bottom vent areas should each be at least 50 percent of the collector’s horizontal cross-sectional area (again, more is better). The collector frame is constructed from wood, and consists of six vertical members, a bottom sill, and a top sill. The six vertical 2 by 6s divide the collector into five, 4-footwide (1.2 m) bays. A 2 by 6 is used for the bottom sill. A 2 by 8 is used for the top sill, which should be sloped at about 10 degrees to shed rain. The collector frame attaches to the building by lag bolts from the inside. The collector is glazed with clear Suntuf corrugated polycarbonate panels. These panels have an ultraviolet light-resistant coating on their sun-facing side to extend their life. Each panel is 26 inches (66 cm) wide by 96 inches (244 cm) high. There are ten panels. Pairs of 26-inch-wide panels are joined over a 1- by 1-inch (2.5 x 2.5 cm) vertical wood strip to make the 4-foot-wide panels for each bay. Two, 1- by 1-inch horizontal members provide additional support for the glazing. The absorber is installed on battens placed about halfway between the glazing and siding. After measuring the thermal performance with one, two, and three layers of window screening, I found that two layers work best.

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Disclaimer: Please use caution when working with tools such as saws, hammers, electric drills, etc.... Just because we feature these alternative energy how-to's does not directly imply that you will be able to do everything with any incident just by following the directions. Please make safety your number one concern! EnergyRefuge.com assumes no liabilities for accidents involving our instructions or those that are re-posted. Please use common sense and please consult a professional if needed.

Solar DIY/How-Tos

Everybody loves alternative energy how-to projects, so we are endeavoring to bring you the best alternative energy how-to's on the web. Check out our additions to the energy how-to section and leave some feedback for us in our forums. Our goal in providing this how-to section is to empower everyday individuals who seek to make change in their energy consumption and seek to move to alternative energy. We are here to share our experience in the alternative energy field, and hopefully it will inspire, encourage, and make a change in your energy use. Please contact us if you would like to submit a solar how-to or an alternative energy project.

Small Solar Electric Systems

Some of the alternatives for those looking to get cleaner electricity are small solar electric systems. Small photovoltaic (PV) systems can provide the ideal solution to locations where getting connected to the grid is impossible. They can be more efficient in sunny areas such as the American southwest, although they can work well in other types of climates, too.
PV small solar electric systems are designed to harness solar power as it hits the earth. These are crystalline silicon panels that capture sunlight and turn it into electricity, which is then stored in a battery bank. When battery charges drop below a certain level, the solar panels recharge the batteries. Photovoltaic panels can be mounted on a rooftop or a freestanding solar array rack.

Energy Savers recommends that before buying a small solar electric system the buyer should be sure that the site where it will be installed has enough solar energy to meet the electricity needs of the building, both efficiently and economically. The supplier can perform an analysis or give instructions on how to do that. It’s important to consider the geographic orientation and the tilt of the solar panels as these can affect performance. Still according to Energy Savers, it’s also important to accurately size the components of these small solar systems, especially when these are not connected to the grid (“stand alone”). The organization advises considering how much of the total electricity need the PV system would be expected to supply, which can be done by analyzing past electricity bills and consulting with a potential provider of small solar electric systems. Before installing small solar electrical systems, it is necessary to obtain permits from the city or county’s building department (a building or electrical permit, or both). The PV provider often looks after this for the client, but it’s important to make sure that permitting costs and responsibilities are addressed when negotiating an electricity system. Those who live in a homeowners association must also get approval from them, unless state laws say that citizens have the right to install a small solar system on the home. The fact is that the number of these types of systems is growing. Even a cold weather state like Minnesota has been registering record numbers of solar system installations (178 between January and November 2010), thanks to governmental incentives that have reduced costs per watt to $7.50.

How does my wind generator work?

How does my wind generator work?

Every wind generator, whether they produce enough energy to power a city or to power a small radio, works on these same basic principles...

1. The wind blows

2. The generator's vane (tail) causes it to turn into the wind

3. Blades attached to an alternator/generator experience the force of lift and begin to spin

4. The spinning creates electricity for us to use directly or to charge batteries

Sounds pretty simple eh? Well, then how the heck do I build one? Read on...

Tools Required

Surprisingly, building a simple wind generator only requires very basic hand tools, and if you are desperate you won't necessarily need all of them. I used...

• Jigsaw (or a hacksaw and a lot of determination)

• Drill

• (2) Drill Bits (1/2", 7/32")

• Tape Measure

• Crescent Wrench

• Pipe Wrench

• Protractor (to measure angles for the hub)

• Sandpaper (various grits)

Parts Required

I wanted to be as minimal as possible with my design (I'm poor), so I took the already simple designs from around the web and made them even simpler. All of the parts are available at any local home improvement or hardware store, and the entire setup can be constructed in as little as a weekend. Many of the parts you may already have lying around, and lots of substitutions can be made (instead of 1" steel pipe for the tower, you could use an antenna pole for instance). Here are the parts I used to build my generator...

• 10" x 14" Steel Sheet

• 10" x 1/4" Steel Nipple

• 1-1/4" Floor Flange

• 36" x 1" Square Tubing

• 1/2" Bore Circular Sawblade (for hub)

• 5/8" x 1/2" Arbor (to attach sawblade to motor shaft)

• (2) Metal Straps

• 8" x 4" PVC Pipe

• 30" x 8" PVC Pipe (6" pipe works well too)

• A DC Permanent Magnet Motor (preferably Ametek 30V or 260V 5A treadmill motor)

• (8) 1/4" Bolts (with washers and nuts)

• (2) 1/4" Sheet Metal Screws

• 10-40 Amp Diode (the bigger the better)

All of the above parts (with the exception of the motor), can be picked up in a single stop to any large hardware or home improvement store. For the motor, the most popular types are old tape drive motors manufactured by a company called Ametek. The key is to finding a motor that puts out the highest voltage per RPM. For instance, the Ametek I'm using is rated for 30V at 325 RPM, making it excellent as an electricity generator (for a nice output comparison of the Ametek motors commonly found on eBay and other sites see TLG Windpower). However, pretty much any permanent magnet motor with a good volt/RPM ratio will do. Keep in mind that if you want to generate useful electricity, you will need to produce at least 12V to charge deep cycle batteries or run an inverter. My setup can easily achieve 300-400 RPM in a pretty average wind (for Oklahoma). These instructions assume an Ametek motor with a 5/8" shaft, but can easily be adapted to other motors (search ebay for "wind generator" and you will get a listing of lots of good motors).

Blade Construction

Arguably, the most important part of a wind generator are its blades. A lot of people like to carve their own blades out of wood or composite materials. However, for the rest of us, it's quite easy to make a good set of generator blades from common PVC pipe (and the efficiency isn't too bad either). A 2-3 foot section of either 6" or 8" PVC pipe will do the trick. Before we go any further, here are a few blade theory quickies...

• The longer your blades are the more "swept area" you have to gather energy from and easier your blades will spin in low winds, but the slower your rotation speed will be

• The tips of the blades always spin faster than the base, therefore one needs to take into account the "tip speed ratio" (TSR) when designing blades (there is a reason why old farm windmills will spin all year long at 40RPM)

• The power that can be extracted from the wind increases by the cube of wind speed (something like P=k*v^3 k=constant of wind generator, v=wind velocity)

• According to the Betz Limit, only about 59.3% of power can be extracted from the wind (so in reality P=.593*k*v^3, assuming k accounts for mechanical inefficiencies in the generator motor)

• The higher you get the generator off of the ground, the more wind it will be exposed to (the general recommendation seems to be 25-50ft., but I've had decent results at just 12ft.)

Cutting the blades for this machine is very simple. You will need to cut your PVC pipe into 3 sections, two 150 degree sections and one 60 degree section (I've attempted to illustrate this VERY APPROXIMATELY in my favorite CAD program--and by CAD program I really mean MS Paint). The red lines are cut marks. You will want to use a good tape measure and possibly some construction paper or newspaper to mark everything before you cut. The 150 degree angles will result in wide blades that start up in lower wind speeds, however this will lower the shaft turning speeds. In practice, you will find that the optimum angle could be anywhere from 75-150 degrees. The best idea is start out with a wide set of blades that you can always thin out later if you need to. Remember, measure twice and cut once!

After the blades are cut, I like to go ahead and smooth out all of the edges. If you want to follow aerodynamic theory, you can round the angled (leading) edge and flatten the straight (trailing) edge, but in practice I haven't seen this make much difference with PVC blades. So, you should end up with something roughly like these...

Hub & Blade Assembly

The next obstacle is building a hub to attach the blades to. There are many types of ways that this can be done. I have used circular sawblades and scrap steel disks. I recommend the sawblade approach, as they are readily available and easy to drill through. You can pick up an arbor with a 5/8" or 1/2" shaft at any homestore that will attach directly to the sawblade. Using the 1/4" drill bit, you will want to drill 3 sets of 2 holes 1" apart which each set 120 degrees from the next (this is where the protractor comes in handy, unless of course you are a Euclidean purist in which case you probably don't need a protractor). Here is a picture to make it more clear...

It's a pretty simple idea, but circular sawblades have worked out very well for me as hubs. Be sure and get some sort of rubber covering for the tooth edges and/or file down the edges as best you can, because the last thing you want is a hub of death flying at you if your generator decides to rip apart!

After our holes are cut out and we are confident of our safety procedures, we attach the blades to the hub (note that the hub pictured was cut from scrap steel, more pictures to come later)...

Tail & Pivot Assembly

Now we need to build a spinning platform for our generator motor to rest on. To achieve this, we will use some square tubing, a pipe nipple, flange, and small sheet of steel. Here is my "CAD" draft of what I wanted my tail & pivot assembly to look like, and a real picture of some of the parts I used...


First, I recommend cutting the sheet steel with a jigsaw into a nice design for the the tail (Note: this step is quite unneccessary and ONLY for aesthethic reasons).



We then want to make a cut down the center of the square tubing. The length of the cut isn't that important, but I recommend about a 9" cut (this will help make balancing easier later on). We may then slide the tail metal into the hole and use the 1/4" drill bit to drill and attach the tail to the square tubing.




We will then want to cut out a weather covering for our motor. A piece of 4" PVC slips perfectly over the Ametek 30V motor that I use. I cut it out like so (note the side hole for the motor wires).



Then we go ahead and paint it all up to seal everything from the elements. I wouldn't recommend painting on your front porch like I did though...



After everything is painted, we can now put it all together. Take the floor flange and put it under the square tubing about 6"-7" from the head. Mark the holes and drill them out with the 7/32" drill bit (or any bit close to but smaller than 1/4"). Attach with the 1/4" sheet metal screws. Use the metal straps to secure the motor and cover assembly, screw on the pipe nipple and you should have something like this...

Tower Assembly

Every wind generator needs a tower. I built mine from some pipe fittings from my local hardware store. If you already have an antenna pole or electrical conduit lying around, then you can skip this section. Here is my recommended parts list for a small extensible tower...

• (2) 5' Sections 1" Pipe

• (1) 1" Pipe Coupling

• (3) 1" Pipe Elbows

• (4) 18" Pipe Sections

• (2) 12" Pipe Sections

The tower base is pretty self-explanatory. Just hook up the elbows and pipe sections to create a base similar to this...



From there we can attach the 2 5' sections of pipe together to form a nice strong mini-tower for our generator to sit atop...

Finished Product

Now we are ready to attach the blades to the motor shaft with the arbor. You will also want to go ahead and attach some wire to the motor and run it to a device to power or a bank of batteries etc...



Here is a picture of the experimental design using six blades. It would spin in practically no wind, but would never get past 100RPM. At least it looked interesting!


Here is the battery bank I'm feeding into in parallel with solar panels. I am just using two 12V marine deep cycle batteries that can be found at any place that sells car batteries. I keep them in a standard plastic tub with a hole cut in the sides for 12V fans I cannibalized from a couple of old Mac G4s (not pictured). Be sure and put a diode between the battery and the generator so that current doesn't flow from the battery to the motor.



It turns out, cutting the blades a little thinner works better for my area. So I used the large white blades from the previous picture and thinned them out a bit. This resulted in the fastest shaft speeds as seen in first video at the top of this page.


Thank You

How I Built a Wind Generator

How I Built a Wind Generator in My Backyard for $150

Lately I've been spending a great deal of time working on ways to generate my own electricity. It isn't a necessity for me yet, but someday being electrically self-sufficient could really come in handy. My interest started a while back when I stumbled upon a how-to article on building wind generators from treadmill motors and PVC pipe. It sounded easy enough, so I decided to try and design my own. This particular design can be built for $100-$150 if you are thrifty and can regularly generate 50-250 watts (considerably cheaper than a solar panel of similar power output). Here's how I built it for those of you who are interested. Additionally, please check out my new frequently asked questions page for more information not discussed in detail here.


Videos

Wind Turbines Vs. Solar Panels

Wind Turbines Vs. Solar Panels

June 28th, 2010 — 11:21am

What will work better: residential solar panels or wind turbines for the residence? A great deal will be based upon the region where you live as well as the weather conditions

there. Here we will check out the pros and cons of both starting off with the benefits of solar panels.
Solar panel pros:
1) Although commercial solar electricity systems are even now relatively expensive, the expenses are coming down. Best of all, your can assemble photo voltaic panels pretty easily and for roughly around $100 each. The actual construction of a photo voltaic panel is really really simple. You possibly have all or most of the tools you’ll have to have in your garage.
2) Solar panels are very easily added as time goes by. If you start with a smaller array, even one or two panels, you’ll be able to add to it as your time and money permit. Do not think as though you need to install an entire solar system to your property all at once. Get started now and at some point you’ll have a solar powered house. With every single panel you put up, you’ll have to buy less electricity from the utility company.
Solar panel cons:
1) Photo voltaic panels do not function at night. This isn’t a real disadvantage if you are still connected to the electrical grid. You’ll be able to buy electrical power at night and sell electricity you produce back to the power company in the day time. This ebb and flow of electrical power translates into no electric bill to pay each month.
2) Climate can be a limiting factor. Residential solar energy will work far better in Phoenix than it will in Seattle, but the fact is there’s adequate sunshine in almost every city and state inside the United States to make your own solar energy feasible.
Wind turbine pros:
1) Like solar, after your wind turbine for your residence is installed and operating, the maintenance is minimal. You can even construct your own wind turbine for under $150. Commercial wind turbines would cost a lot more, but if you know how simple they are to assemble there’s no reason to buy commercially.
2) Wind turbines for homes generate power day and night, whenever the wind is blowing. Like solar, some locations are going to be much better than others but wind power generators are absolutely realistic in most areas of the country.
Wind turbine cons:

1) A rooftop wind turbine could be a bird hazard. On occasion birds fly into the blades of rooftop wind turbines and are injured or killed. The hazard is really no more than the smaller windmills you see for irrigation on farms. The bird hazard is actually significantly more a concern with large wind farms situated in major bird migration routes like the ones in Southern California.
2) Wind turbine generators make noise. Unlike a residential solar panel which is 100 % silent, a residential wind generator will make a whoosh whoosh sound as it spins.
Whichever you decide on, photo voltaic or wind power, you’ll be a winner and so will the environment. You will have lower or no electric bills and there will be less carbon dioxide spewed into the atmosphere. And here’s a thought for your future: Nissan now sells an all electric vehicle, the Leaf, and many more car manufacturers will have them in the foreseeable future. Imagine never having to pay for gasoline once you generate your own power at home.

Comment » | wind turbines

What to Know in Residential Wind Turbines

June 28th, 2010 — 11:19am

When you think about wind turbines, the tower with four blades reminiscent of Holland country landscape with the tulips and the Dutch gal is the first image that may come to mind. That image of a windmill seems a prototype of the mechanical wind turbine, also called aerogenerator that uses the wind energy to turn kinetic energy to electricity. It is also one of the mechanical inventions requiring great respect for it helps in alleviating the over-dependence of fossil fuels in generating electricity to power homes.
A distinction is to bring regards though in associating windmill with wind turbines. Windmill has mechanical purposes and that may not include generating electricity. The wind turbines, however, are invented to harness the strength of the wind to convert energy to electricity by turning the blades of the electric-generating wind system.
It may not be necessarily that huge to construct one unless you want megawatts of electricity to power a lot of machines in many households; that situation may need a behemoth one or numerous wind turbines beautifully lined up on a road or isolated locations to bring electricity to a whole town or a district of towns. The wind turbines may be humongous but seeing them collectively in an orderly, interval set-up makes them like the 8th modern wonders. These turbines have been utilized as a gradual replacement to the fossil fuels.
However, in the case of wind turbines for domestic application, the towering machines don’t have to be that big. A certain size for home use may be installed though. But, it is also important to note how much electricity you normally consume, as this will be a factor in availing a residential wind turbine with the appropriate capacity of the system for use in homes.
There are some things to learn about residential wind turbines. Although aerogenerator can be among the best machines that help lessen the amount of smokes fumed out from the power facility, using this at home is in simultaneous fashion with procuring electricity from local power utility at the beginning. The cut-in speed of wind turbines for homes is 7-10 mph. Below that speed is not sufficient to power a home, so it is better to have another connection of wires with electric power derived from the local power utility plant.
However, when the wind speed peaks up in the location of the wind system, enabling the turbine to roll its blades faster, the energy piles up converting to electrically charged current. As the turbine’s blades move at faster rotating speed and continuously, more and more electric current is made and the electricity may be enough to power homes, thus decreasing or eventually eliminating the dependence of power from the local power retailer. There can also be the tendency that the excess power produced from the turbine can be sold to the local power utility.
Residential wind turbine is an alternative medium to obtain energy to turn into electricity to power homes. This can be used as replacement to or in conjunction with solar panels, making your home environmentally friendly. This blade-turning machine with rotor and shaft may not even require batteries to make it work. Modern residential wind system eliminates the need for batteries and this is to watch out for when opting to acquire one or a set of required wind system.
If you desire to have a set of the wind machine system that helps generate electricity in your homes, make it a point to browse around. The best deals of residential wind turbines are just here for your purchasing decision.

This website has been created to chronicle the building of my 17' diameter wind turbine.

  

Background...
In the fall of 1999 I moved to a rural area of West Virginia, named Terra Alta (high earth). To be honest we live at the *top* of Terra Alta, our house is at an altitude of 3000' where we have a panoramic view of about 270 degrees for up to50 miles!

Besides the wonderful view we also have wind, lots of wind!

So why not harness some of this to generate our own electrical power?

Typically I research the heck out of stuff, and this project is no exception! There is one website that I have found to be *the most* informative site (OtherPower). I have decided to build a wind turbine that closely resembles their 17' diameter unit, the main changes that I will be making is some slight modifications to 'beef' up the metal structure in a couple of places, otherwise it will be the same. This turbine is of the axial flux design. I want to output 2-3kwh in a 20mph wind and have found that this one should suit my needs.

Post note: they have redesigned and rebuilt their 17' turbine and it now is capable of putting more power! The structure of it closely resembles their larger 20' wind turbine.

Some good informative reading "The Bottom Line About Wind Turbines", this is a good place to start out to help you determine if a wind turbine would suit your needs.

Commercial Possibilities...
There are more and more commercial business that are involved with 'green' power'. If you have any doubts in your abilities to make your own wind turbine then either seek out a workshop (the guys at OtherPower.com have them) or purchase a commercially available unit. Many wind turbines are now available that output anywhere between 400-3.5kwh, with price and size being the major differences.

Roll your own...
I made the choice to make my own wind turbine. There were a number of factors that influenced this decision: 1) I have the skill sets 2) I have the tools 3) I have the desire 4) No tax incentives are in place to entice me into purchasing a commercial unit.
The fourth reason was probably the major item that helped me with my decision. For the type of power output that I was desiring the average cost for a commercially manufactured was between $6,000-8,000. I knew that for under $1,500 I could purchase all the items and build my own. Had there been federal/state tax credits that would have helped offset the initial investment, I would have gone that route.
The tower is another matter - I will not be building my own and am currently searching for a suitably strong - hopefully guy less free-standing tower, either monopole or lattice design. What money I save in the wind turbine will help offset the tower costs.
Disclaimer..
I am not a structural nor design engineer, the methods, tools, diagrams used/shown/discussed within this website are what I used building my own wind turbine, and as such warranty nothing. Use your own common sense when building yours and if in doubt see a professional.
It's Flying - Some Pictures..
After all of my hard work the wind turbine is on top of the tower and operational.
Click on a picture to see larger image:

Solar Power Step By Step Guide

Solar Power

Solar power is the basis for all life on earth! Solar heating has been used for thousands of years to warm dwellings (solar thermal). But solar electricity (photovoltaics) is a very new industry.

Solar Photovoltaic (PV) --a zero maintenance, zero fuel cost electric generator

Solar panels have no moving parts. You just mount them out in the sun, hook up the wires, and collect power, without adding fuel or replacing worn-out parts. It's amazing that nobody knows for sure how long a solar panel will last. That's because many of the very first photovoltaic panels are still producing power today.

Solar Electricity Basics

We often receive questions here along the lines of 'how many solar panels do I need to power my 3,000 square foot house?' We don't sell or install solar power systems, so we can't provide free consulting services and still keep our business running. However, we've written numerous articles on the topic and compiled a list of resources to help answer your questions and start you on the right track for doing your 'homework' on the topic:

• The design, size and cost of a solar photovoltaic power system for your home depends on only a few simple factors:
  1. How much energy in kilowatt-hours (kwh) do you use per month, and how much does it cost you?
  2. What can you do to reduce your energy usage, and how much will that cost you? (Every dollar spent on conservation will save you $3-$5 on the cost of an RE power system).
  3. What solar resource do you have available at your location?
• Renewable Energy Basics -- This article guides you through answering ALL those questions above, in great detail. Includes information on grid-tied, off-grid and grid tie with battery bank systems.
• Designing a tiny solar power system for a camping trailer -- This article goes through the basics of designing a properly-sized solar power system, including calculating your inputs, loads and battery bank size.
• If you are serious about moving to a solar power system for your home or cabin, most local solar dealers / installers will provide you with a free or low-cost estimate and energy estimate. Going local is an excellent choice!
• Most internet solar power retailers have lots of free information online, including system sizing spreadsheets. Two retailers that we patronize frequently because of their great customer service are The Alternative Energy Store and Backwoods Solar -- but there are many more excellent retailers online.
• Shopping by Dollars per Watt is the best way to choose solar panels. Photovoltaic panel prices have steadily been dropping at 3-5 percent per year for the last decade or so. However, prices may not seem all that low to you, because in general the technology is getting better, so each panel is making more watts than those of a few years ago. You have two options for buying photovoltaics, new and used:
  • New photovoltaic panels -- This page gives some details about new panels, including how the technology is advancing, and information about tracking mounts.
  • Used photovoltaic panels -- This page discusses how to inspect used panels for damage and test their output before purchasing.
  • We are no longer maintaining our used solar panel mailing list. Because of strong demand for large photovoltaic installations around the world, there has been a general shortage of new panels. This has increased demand for used panels too, and we have not seen any large lots of used panels available for 4 years now. The best places to look for used PV panels are your local newspaper classifieds, Craigslist, and Ebay.

Solar Thermal Panels -- using the suns energy directly for heat

Using solar power directly to heat air or water is the most efficient way to do it. Solar electric is not a very efficient way to heat things, but solar thermal works great! We don't have a huge amount of information here about solar thermal, but there are some links below for you.

• Passive solar house design is an excellent way to heat a home. Generally it's designed into the home from the ground up, with south-facing windows, thermal mass to store heat, lots of insulation, and thermal blankets for the windows at night. DanF's home was designed this way. Until we do get a page up here about passive solar heating, you can search the internet for the term and get a wide variety of books and articles on the topic.
• Solar hot water heating panels became very popular in the USA in the late 1970s and early 1980s for preheating a homes hot water. Government tax credits were offered by the Carter administration, and many companies sprang up designing and installing systems. When the Reagan administration cancelled the tax credits, many of these companies went out of business, and there were very few people left to maintain and repair these systems. Many of them are still sitting on roofs today, broken. HOWEVER, it became obvious very quickly that some of these companies were 'fly-by-night' and their products were poorly designed in the first place:
  • In general, we advise against purchasing these old systems used. It's actually easy to find one for free, which might be OK if you are experimentor and enthusiast. But these older systems used numerous active controls, sensors and pumps, and were very unreliable compared to the excellent, low-maintainance and reliable systems available today.
  • Solar water heating panels are NOT a new idea! This article about the history of solar water heating is an excellent read. Thousands of systems were installed and were very effective in sunny parts of the USA around 1900.
  • On the other hand, modern solar water heating panels are an excellent investment in most parts of the county! The technology has changed so much that these systems are now completely different in design than those from the Carter area that caused so many problems. Some industry analysts say that the loss of the tax credits, while it had a large negative impact on the industry at the time, ended up being the best thing that ever happened to the industry in the long run.
  • These systems are now often incorporated along with radiant floor heating pipes. The sun heats the fluid, which circulates inside the high thermal mass floor of the home. This is a VERY efficient way to heat a home!
• Solar air heating panels are another new technology that's catching on quickly. It allows the homeowner to retrofit a house that was not orginally designed for efficient passive solar heating, and reap the benefits and energy savings of heating with the sun.

Guide on Residential Wind Turbine

Guide on Residential Wind Turbine

June 28th, 2010 — 11:24am

Residential wind turbines are a wonderful model to produce a

cheaper source of free energy. Knowing what to search for and where to buy one is essential in getting you started. If you are looking for a suitable residential wind turbine kit, the good news is that there is lots of places where you can do so. This is not something you can just get at a ironware store. Instead, a little searching have to be done first. In fact, the internet is one of the best places to find and buy residential wind turbines kits.
Assuming you have decided to purchase it online, there are a few points to check if it is a good bargain. You want to be positive you only purchase them online from a site that extends free transport though. Do not purchase them offline if the company does not provide free shipping. If not, the kit will be extremely costly with accumulated charges tallied on. On The Average, a rational price for a residential wind turbine should be around $300. If you find any sales where the cost deviates quite a bit you may want be be skeptical. It may be a scam.
A wind turbine is more commonly referred to as a windmill. It can also be referred to as a wind generator. Though the terms are used interchangeably, each is not the same as the other. What makes a wind turbine different from a windmill? For instance, a wind turbine converts wind energy into mechanical energy that can be further converted to electrical energy whereas a windmill will just use the mechanical energy as is. As a windmill does not convert the energy, it cannot really be considered a wind turbine even though the words are often used interchangeably.
Let’s examine the different types of wind turbines. Wind turbines are classified based on their orientation. There are two basic kinds of wind turbines known as the Horizontal Axis Turbine and Vertical Axis Turbines. The Horizontal Axis turbine contains blades that rotate across a horizontal axis. Conversely, The Vertical Axis turbine rotates its blade on a vertical axis. The Horizontal Axis Wind Turbines are more popularly used in various parts of the world. This is because horizontal axis wind turbines are more efficient than the vertical ones.
The advantages of installing a residential wind turbine includes saving power, cost effective, environmental friendly and perpetual power supply.
Some advantages of wind turbines include:

• Perpetual power supply – You do not have to be dependant solely on the government for your power supply. Endless supply of power means never having to deal with a power outage too!

• Saving Power- Wind turbines use wind energy to produce the same energy that we have to pay electric companies to use so we save power by not having to use regular electricity.

• Cost Effective – Because wind is free, the only actual costs a user incurs is in installing and maintaining the wind turbine.

• Environment Friendly – Wind turbines run on a natural energy source and are therefore not harmful to the environment.

The benefits of a wind turbine so attractive that everyone would want to install one, but if it is not correctly done, it can be quite bad. Before installing a wind turbine, do consider the following.

• You must have at least an acre set aside to install it on.
• Make sure the average wind speed is about 11 miles per hour.
• Make sure the tower and base are ironclad. It is the wind turbulence that can mess up your wind turbine so take that into consideration as well.
• Make sure that the distance between the wind turbine’s height and the wind generator and cells is optimal.

Vertical-axis wind turbines

Vertical-axis wind turbines (or VAWTs) have the main rotor shaft arranged vertically. Key advantages of this arrangement are that the turbine does not need to be pointed into the wind to be effective. This is an advantage on sites where the wind direction is highly variable, for example when integrated into buildings. The key disadvantages include the low rotational speed with the consequential higher torque and hence higher cost of the drive train, the inherently lower power coefficient, the 360 degree rotation of the aerofoil within the wind flow during each cycle and hence the highly dynamic loading on the blade, the pulsating torque generated by some rotor designs on the drive train, and the difficulty of modelling the wind flow accurately and hence the challenges of analysing and designing the rotor prior to fabricating a prototype.^{[citation needed]}
With a vertical axis, the generator and gearbox can be placed near the ground, using a direct drive from the rotor assembly to the ground-based gearbox, hence improving accessibility for maintenance.
When a turbine is mounted on a rooftop, the building generally redirects wind over the roof and this can double the wind speed at the turbine. If the height of the rooftop mounted turbine tower is approximately 50% of the building height, this is near the optimum for maximum wind energy and minimum wind turbulence. It should be borne in mind that wind speeds within the built environment are generally much lower than at exposed rural sites.^{[citation needed]}

[edit] Subtypes

Darrieus wind turbine of 30 m in the Magdalen Islands

Darrieus wind turbine 

"Eggbeater" turbines, or Darrieus turbines, were named after the French inventor, Georges Darrieus.^[17] They have good efficiency, but produce large torque ripple and cyclical stress on the tower, which contributes to poor reliability. They also generally require some external power source, or an additional Savonius rotor to start turning, because the starting torque is very low. The torque ripple is reduced by using three or more blades which results in greater solidity of the rotor. Solidity is measured by blade area divided by the rotor area. Newer Darrieus type turbines are not held up by guy-wires but have an external superstructure connected to the top bearing.^{[citation needed]}

Giromill

A subtype of Darrieus turbine with straight, as opposed to curved, blades. The cycloturbine variety has variable pitch to reduce the torque pulsation and is self-starting.^[18] The advantages of variable pitch are: high starting torque; a wide, relatively flat torque curve; a lower blade speed ratio; a higher coefficient of performance; more efficient operation in turbulent winds; and a lower blade speed ratio which lowers blade bending stresses. Straight, V, or curved blades may be used.^{[citation needed]}

Twisted Savonius

Savonius wind turbine 

These are drag-type devices with two (or more) scoops that are used in anemometers, Flettner vents (commonly seen on bus and van roofs), and in some high-reliability low-efficiency power turbines. They are always self-starting if there are at least three scoops.

Twisted Savonius 

Twisted Savonius is a modified savonius, with long helical scoops to give a smooth torque, this is mostly used as roof windturbine or on some boats (like the Hornblower Hybrid).

Modern wind turbines

Modern wind turbines

Turbine blade convoy passing through Edenfield in the UK

Turbines used in wind farms for commercial production of electric power are usually three-bladed and pointed into the wind by computer-controlled motors. These have high tip speeds of over 320 kilometres per hour (200 mph), high efficiency, and low torque ripple, which contribute to good reliability. The blades are usually colored light gray to blend in with the clouds and range in length from 20 to 40 metres (66 to 130 ft) or more. The tubular steel towers range from 60 to 90 metres (200 to 300 ft) tall. The blades rotate at 10-22 revolutions per minute. At 22 rotations per minute the tip speed exceeds 300 feet per second (91 m/s).^[15][16] A gear box is commonly used for stepping up the speed of the generator, although designs may also use direct drive of an annular generator. Some models operate at constant speed, but more energy can be collected by variable-speed turbines which use a solid-state power converter to interface to the transmission system. All turbines are equipped with protective features to avoid damage at high wind speeds, by feathering the blades into the wind which ceases their rotation, supplemented by brakes

Resources

Main article: Wind power

A quantitative measure of the wind energy available at any location is called the Wind Power Density (WPD) It is a calculation of the mean annual power available per square meter of swept area of a turbine, and is tabulated for different heights above ground. Calculation of wind power density includes the effect of wind velocity and air density. Color-coded maps are prepared for a particular area described, for example, as "Mean Annual Power Density at 50 Meters." In the United States, the results of the above calculation are included in an index developed by the U.S. National Renewable Energy Lab and referred to as "NREL CLASS." The larger the WPD calculation, the higher it is rated by class. Classes range from Class 1 (200 watts/square meter or less at 50 meters altitude) to Class 7 (800 to 2000 watts/square meter). Commercial wind farms generally are sited in Class 3 or higher areas, although isolated points in an otherwise Class 1 area may be practical to exploit.^[12]

[edit] Types

The three primary types:VAWT Savonius, HAWT towered; VAWT Darrieus as they appear in operation.

Wind turbines can rotate about either a horizontal or a vertical axis, the former being both older and more common.^[13]

[edit] Horizontal axis

Components of a horizontal axis wind turbine (gearbox, rotor shaft and brake assembly) being lifted into position

Horizontal-axis wind turbines (HAWT) have the main rotor shaft and electrical generator at the top of a tower, and must be pointed into the wind. Small turbines are pointed by a simple wind vane, while large turbines generally use a wind sensor coupled with a servo motor. Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive an electrical generator.^[14]
Since a tower produces turbulence behind it, the turbine is usually positioned upwind of its supporting tower. Turbine blades are made stiff to prevent the blades from being pushed into the tower by high winds. Additionally, the blades are placed a considerable distance in front of the tower and are sometimes tilted forward into the wind a small amount.
Downwind machines have been built, despite the problem of turbulence (mast wake), because they don't need an additional mechanism for keeping them in line with the wind, and because in high winds the blades can be allowed to bend which reduces their swept area and thus their wind resistance. Since cyclical (that is repetitive) turbulence may lead to fatigue failures, most HAWTs are of upwind design.

wind turbines

This article discusses wind-powered electrical generators. See windmill for wind-powered machinery used to grind grain or pump water.
A wind turbine is a device that converts kinetic energy from the wind into mechanical energy. If the mechanical energy is used to produce electricity, the device may be called a wind generator or wind charger. If the mechanical energy is used to drive machinery, such as for grinding grain or pumping water, the device is called a windmill or wind pump. Developed for over a millennium, today's wind turbines are manufactured in a range of vertical and horizontal axis types. The smallest turbines are used for applications such as battery charging or auxiliary power on sailing boats; while large grid-connected arrays of turbines are becoming an increasingly large source of commercial electric power.

History of Wind Energy (Best)

Since early recorded history, people have been harnessing the energy of the wind. Wind energy propelled boats along the Nile River as early as 5000 B.C. By 200 B.C., simple windmills in China were pumping water, while vertical-axis windmills with woven reed sails were grinding grain in Persia and the Middle East.

 

Early in the twentieth century,   windmills were commonly used  across the Great Plains to pump water and to generate electricity.

New ways of using the energy of the wind eventually spread around the world. By the 11th century, people in the Middle East were using windmills extensively for food production; returning merchants and crusaders carried this idea back to Europe. The Dutch refined the windmill and adapted it for draining lakes and marshes in the Rhine River Delta. When settlers took this technology to the New World in the late 19th century, they began using windmills to pump water for farms and ranches, and later, to generate electricity for homes and industry.

Industrialization, first in Europe and later in America, led to a gradual decline in the use of windmills. The steam engine replaced European water-pumping windmills. In the 1930s, the Rural Electrification Administration's programs brought inexpensive electric power to most rural areas in the United States.

However, industrialization also sparked the development of larger windmills to generate electricity. Commonly called wind turbines, these machines appeared in Denmark as early as 1890. In the 1940s the largest wind turbine of the time began operating on a Vermont hilltop known as Grandpa's Knob. This turbine, rated at 1.25 megawatts in winds of about 30 mph, fed electric power to the local utility network for several months during World War II.

The popularity of using the energy in the wind has always fluctuated with the price of fossil fuels. When fuel prices fell after World War II, interest in wind turbines waned. But when the price of oil skyrocketed in the 1970s, so did worldwide interest in wind turbine generators.

The wind turbine technology R&D that followed the oil embargoes of the 1970s refined old ideas and introduced new ways of converting wind energy into useful power. Many of these approaches have been demonstrated in "wind farms" or wind power plants — groups of turbines that feed electricity into the utility grid — in the United States and Europe.

Today, the lessons learned from more than a decade of operating wind power plants, along with continuing R&D, have made wind-generated electricity very close in cost to the power from conventional utility generation in some locations. Wind energy is the world's fastest-growing energy source and will power industry, businesses and homes with clean, renewable electricity for many years to come.



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