Specific to Small Wind Turbines/conditions:

If the “Actual” average wind is less than 8mph, your conversion efficiency will be very low, possibly less than 30% of the power created will be converted through a Grid-tie application. Charge controller are a bit more efficient because your not stepping up the voltage so high – possibly only to 20v or 50v. An inverter requires a step up to 220v in most situations. This could be 5x to 10x the produced voltage in lower wind conditions. Rapid changes in wind speeds make the step up process very difficult for modern equipment to handle.

If your winds are on Average greater than this then the efficiency in conversions goes up in respect to the wind speeds. At higher wind speeds the conversion efficiency optimal. If you get a wind of about 20mph (consistent – with no wild gust variations) your conversion should be about 80% to 90%)

In winds about 12 mph (again constant, with little or no wild variations) your efficiency should be about 50% to 60%, the efficiency is directly related to the “consistency of wind”. Rapidly changing wind speeds will greatly affect the conversion efficiency.

Though we think we have identified some solutions testing still needs to be done and we are working with several companies within the market towards a combined solution. Some of these companies are Texas Instruments, Aurora (Power One), ZhanTech, Xantrex(now Scheinder Electric) and WMIA.

The primary barrier is the wide varying range of power generated by SolAir’s Permanent Magnet Generator. Modern inverters are not efficiently capable of converting or in some cases recognizing the rapidly changing voltage produced by wind turbines. Modern inverters are working at an approximately 30% efficiency in converting turbine power to grid tie applications.

We have identified some equipment that could potentially increase this efficiency by about 20%, our objective is to increase efficiency to about 80% or great conversion of energy produced by the turbine to a grid-tie application.

Starting with the inverter. The inverter wants to see a DC voltage on its input that is within a specified range. Then it boosts up this voltage by chopping it through a transformer which steps up the voltage and filters out the chopping ripple with an LC filter, or the voltage is boosted by a boost converter and then chopped into a sine wave and filtered with an LC filter.

The inverter needs to put out complete sine waves and does not react fast enough to fluctuating inputs, especially if the input cuts in and out with changing wind speeds. Similar to large Turbines bulk capacitance can be used as a way of filtering these fluctuations out but it would be a huge investment and take a very large space. Some choose to store the energy in a chemical state which is much more space efficient as it can store more energy per unit volume. This allows the converter to stay in sync with the line, and also allows a steady control loop.

If the input voltage is only 40V the inverter needs to step this up to 1.414 x 120V = ~170v plus allowance for losses. So let’s say 180VDC. If the wind generator puts out say 5A at 40V that would be 200Watts. At 120Vac that would be about 1.6A rms. So roughly we have about a 5:1 increase in voltage and about a 5:1 decrease in current.

Wind power generators want to be able to supply low voltage with lots of current or else high voltage and lower currents. Most wind turbines voltages are consistent with lower currents(amps) and higher voltage ranges as they turn faster. Most likely because it is really hard to wind high turn count coils with really heavy copper wire. Hence, more turns with a smaller gauge wire seem more practical. With any direct drive system the prop speed would want to be on the fast side so as to generate more voltage.

The problem here is that the small wind community needs some sort of storage medium that can handle the wide voltage range. Other than batteries there isn’t a good one.

Boost converters can be used to convert the wind generator voltage up to the 180VDC level. Most simple boost converters can’t boost much more than 8X their input voltage due to losses and topological limitations. So if you use 8 as our limit then divide 180V by 8 we would have the minimum wind generator voltage that would work for this system. That would be about 22.5V.

If we try to optimize for lower wind speeds before we cut in power with a 5x to 10x booster this would result in a substantial increase in voltage at higher wind speeds. This would cause the turbine to generate too much load resulting in potential damage the inverter and electrical equipment connected to it.

So if we also consider the generator as linear then we might see 220V on the output, which is okay because the inverter was expecting 180V and could easily handle this higher voltage. The boost converter is happy because now the input exceeds the design output voltage so the boost shuts off and the voltage and current go straight through it with only a diode drop of voltage loss.

A majority of inverters available operate optimally at least 180V on the input. This is fairly consistent with the available products on the market.

Making a boost converter that can bump up 22V to 180V is easy. Making it large enough to handle the current isn’t too hard either. But doing this in a method that is constant and results in effective conversion of power is very difficult.

DyoCore is working towards a solution;

One solution is measuring prop speed and output voltage and current. If the wind energy falls off, the current delivered to the line must also back off. This will take a controller with some smarts – programmable and/or smart application hardware. Some MPPT inverters work in this fashion but optimized for changes in PV not wind.

The other part of the solution is a capacitor that can take rapid changes in input and adjust to a steady output current that can then be leveraged by a standard MPPT inverter.
The combination of these two is the optimal solution for all Small Wind Generators.

Products marketing in this category are often anything but “Small Wind”. The average wind speed in most areas is under 15mph. The average “small wind” turbine doesn’t even function at this wind speed! How is Small Wind determined? What is considered “Big Wind”?

When I developed my product I thought it fit into the category “Small Wind”, but now I’m thinking maybe “Micro Wind”. But nobody likes to be called Micro unless you’re a computer chip. The problem with these categories is they are self assigned. If you find your product performs terrible and under market expectations in large wind you simply classify it small wind, some companies simply put a big price tag on their products and tell you it needs a 250 foot pole and classify it big wind…

As an actual user of my own product I understand there are definitive differences in the placement of a product in these categories but do other manufacturers? Placing a turbine in “Small Wind”, let’s say the average residential wind conditions – fewer than 15mph and that is generous, means your product should then produce is rated performance in those specific conditions. However, manufacturers rate and post performance output on their products in what should be considered “Big Wind” conditions, greater than 20mph, but then classify their product as “Small Wind”. Then they justify this by stating in fine print their product should be installed in “Big Wind” conditions on a 60 foot pole where average wind speeds are greater than 20 mph.

I cringe every time I hear a story about how “Small Wind” products don’t perform and are not financially practical. Then to find the writer was making that assumption on a product that was both miss represented as “Small Wind” and substantially over priced to begin with.

The bottom line is “Small Wind” works if you buy a true “Small Wind” product at a good price point! The unfortunate dilemma is there are no guidelines to how a manufacturer rates or publishes data about their products. Very similar to the “healthy – good for you” sticker they put on the food you buy…

When buying Small Wind do a little research. These questions are easy for any manufacture; what is the rated wind speed? What is the cost per kWh at a realistic “Small Wind” average (under 15 mph most likely) speed in your area? Then see if the product will actually produce a return based on the actual performance in real world conditions.

SolAir rated wind speed output: 800 watts at 12 mph (850 watts combined with Solar)
SolAir Cost: Only $1260
SolAir’s cost per kWh at the rated wind speed - Year 1: $ 0.50w, Year 2: $0.17w, Year 3: $ 0.08w

This is very controversial topic with only one inevitable result. If it sounds too good to be true, it usually is.
Have you seen this device advertised, Power-Saver 1200? For about $300 you can save upwards of 30% on your residential energy bill.

This product is based on the claim that it adjusts your energy usage to reduce I2R losses and a low power factor. The cost savings of managing power factor and I2R losses is perfectly legitimate but the truth is neither applies to the common US household. The average household doesn’t see or recognize a low power factor, so the residential customer isn't charged for it, so eliminating it will not save you any money.

Typically the companies that sell these devices use a video showing a motor drawing significantly less amperage with the device (capacitors) connected. All true but very misleading to the residential power consumer. This demo and angle is overdramatized and dramatically misleading. Truth is, you buy this thing, install it, improve the power factor by some amount (they don't state the KVAR value of the device) and not only save nothing but incur the cost of the unit, installation and the required fuse. You will never save 5%, 10%, or "up to 30%. Utility companies in the US do not charges residential customers for low power factors and don’t measure such usage.

In the commercial markets the utility company will charge the cost of delivering demand energy plus the adjusted profit the markets and the public utility commissions will normally apply to high demand. This is how Power Factor applies in determining your bill based on how much extra current must be carried by the transmission lines during high demand. But the residential market doesn’t measure power factor in the utility billing process unless you possibly live in a commercial market and are a business client. Businesses, however, benefit greatly from power factor correction. The utility has a separate device attached to the meter to measure it but the meter itself still measures only "true power".

As for I2R losses if this device is mounted at the panel, it will not reduce I2R losses because the stored energy oscillates through the house wires between the inductors and capacitors. As this happens, current flows, and losses occur regardless.
I personally have tested now 4 devices and I have purchased a total of 7. I have sent several to professional testing facilities to be tested – everyone with the same conclusion. Additionally several were the exact same device repackaged and relabeled. All of course with a 100% guarantee unless you open the box. Ironically you need to open the box to see what’s in it. For the curious who want to maintain their money back option it apparently only houses a bank of capacitors and one actually had a pilot light in it which appeared to most likely eat more energy than it could possibly save.

In my opinion, do not be sucked into this “go green” with a Power Saver type device. Use your $300 to plant a few more trees around your home, take your kids to the park a few more times a year and simply turn off that light when you leave the room.

I’d like to be proven wrong and will immediately post my apology. I get emails, spam mails and claims about this device. Here’s my challenge, my electric usage is very consistent month to month, I don’t have AC and I never use the heater. Send me a unit, I’ll test it for one month and share with you my billing for the past few months, the current month I install the unit, then the following month without the unit. If my bill is reduced by greater than 10% I’ll retract my statements pay full price for your unit and praise your product. All data during the test phase, including my retraction if I am wrong, will be made public on this and other blog sites along with press. DyoCore will additionally pay you $1,000 for your time If the product proves to actually work with a proven saving of over 20%. This amount being midpoint in most of these product’s marketing data. To participate in my challenge email me at dave@dyocore.com.

Facts about True, Reactive, and Apparent power - http://www.allaboutcircuits.com/vol_2/chpt_11/2.html

First you need to know “how much stuff you have”, then you need to know “How Solar works”. Additionally, but not such a critical factor is “where you live”, it’s fair to assume you will get about 6 hours of direct sunlight a day on average considering clouds, rain, and other weather conditions that might exist in your specific area.

You can start by figuring out how much power your home consumes on average. Your energy bill should provide you with a summary of your energy consumption trends over a period of time. A typical home has the basics, a water heater, stove/oven, dish washer, clothes dryer, electric heater , TV, lights, computer, etc. If we say these items average out to 600 watts. Over the course of 24 hours, you need 600 watts * 24 hours = 14,400 watt-hours per day.

Now a bit about solar. An average solar panel can generate 70 milliwatts per square inch * 5 hours = 350 milliwatt hours per day. Therefore you need about 41,000 square inches of solar panel for the house. That's a solar panel that measures about 285 square feet (about 26 square meters).

Unfortunately this only covers you the part of the day the sun shines, approximately 6 hours, and most likely not the 6 hours your home. So what do you do when the sun isn’t shining? A battery bank is a good solution but very costly to an already costly endeavor. The original question, how much do I need, is a moving target. Solar by itself is not a reasonable cost effective, practical solution.

NOAA Solar Calculators: http://www.srrb.noaa.gov/highlights/sunrise/gen.html