Choosing a small wind turbine for your station

February 1, 2009


In the article "Feel the Power" (Radio magazine, July 2008) I discussed alternative power generation and briefly touched on the wind-powered generator at KPAN radio in Hereford, TX. This time I'll talk about wind power generation in greater detail (though this will not be a primer on exactly how to implement such a system) so you can form a more realistic idea as to whether or not such a system would work as part of your broadcast facility. I'll also revisit KPAN as a case study.

If you look closely at most power consumers you will find the majority use power with less-than-ideal efficiency; that is likely because over the last 100 years or more electric power has been easy to come by and, for the most part, cheap. There has been little if any economic incentive to maximize the efficiency of electrical usage.

A small wind turbine from African Wind Power.

A small wind turbine from African Wind Power.

But now, as attention in the United States is turned on our own energy independence (or at the very least minimizing our dependence upon foreign sources) and an increasing desire to limit carbon emissions, alternative and renewable sources of energy (while not new) are being looked upon much more favorably. In addition to being clean, they are now becoming more economically attractive; electricity is getting more expensive (thus reducing the payback time for the investment in a wind generator, for example) and many state governments offer tax incentives that offset substantial portions of the investment.

Basic steps

But where does one start, in determining whether or not a wind generator is a good investment? I have found various manufacturers and users of wind generation equipment agree on the basic steps, which are compiled in the following list.

Know your baseline usage. For one thing, the wind generators mentioned later are relatively small; you won't be powering a 50kW transmitter site with them. The largest system I'll mention will provide 10kW peak — with its average being lower. Likely, the best way to determine your usage in kilowatt hours (kWh) over the year is to study your electricity bill. If you are building a new system then make use of your engineering expertise to make your best estimate your needs.



Maximize the efficiency of your energy usage

A Proven Engineering 2.5kW turbine mounted on a roof in Ashenden House, London.
<em>Image courtesy Proven Engineering</em>

A Proven Engineering 2.5kW turbine mounted on a roof in Ashenden House, London.
Image courtesy Proven Engineering

As I mentioned earlier, because electricity has been fairly easy to come by in most cases, there has been little incentive in years past to maximize the efficiency of its use in many cases. However, if your intention is to lower your energy consumption for not only economic reasons, but for other principles as well, it makes sense before doing anything else to work at using less power, by finding the simplest ways to cut back. In my experience in California in 2001 (during the statewide energy crisis) I noted that once the problem became top-of-mind for many people, 10 percent of energy usage could be eliminated with very little effort by doing things like turning lights off when a room was unoccupied; turning off TV sets that were not being watched; raising the set-points of air conditioners a few degrees, and so forth. The next steps are also simple, such as replacing incandescent lights with fluorescents, and installing more energy-efficient appliances. While these actions may seem more pertinent to home use, they apply to radio stations as well. Turn out lights; turn up the A/C unit; turn off computers and monitors when not in use.

Study the available wind resources

A Proven Engineering 6kW turbine in a field.
<em>Image courtesy Proven Engineering</em>

A Proven Engineering 6kW turbine in a field.
Image courtesy Proven Engineering

Not all locations are suitable for the generation of power from the wind. That's an unfortunate reality. Most likely you have an idea about how much the wind blows at your particular location. There are a couple of things to keep in mind though: First, the wind is stronger as you get higher above the ground, and so your feeling about how much the wind blows is probably wildly inaccurate. Secondly, even if the wind seems to be blowing all the time, likely the average speed is lower than you would guess; and finally, if the wind is too fast (like during a storm) you might be surprised to know that the wind generators will shut themselves down. Too much wind is not a good thing in this case. Visit www.nrel.gov/wind/resource_assessment.html; this site will give you a reasonable idea about the wind resource in your particular area. Look at the map to find the wind power class of the area you are interested in.

Pick a system that meets your needs

Implicit in that statement is that you know what your needs are after studying your historical power usage and then maximizing the efficiency of your power consumption. If you are in the process of developing a new site, you will have to do the engineering to make the best estimate of your future needs. Then comes the next question: Just what power resource are you looking for? Will your new site be completely off the power grid (like a mountain top with no power lines, and too far for them to be constructed)? Do you want to use a wind generator to supplement a photo-voltaic (PV) system, for battery charging perhaps? Or maybe you simply want to generate electricity to reduce your reliance upon your current electricity source. Any of these three needs can be accommodated.



Catch the wind

Wind generators are anything but unobtrusive. To catch the proper amount of wind, they are typically mounted around 50 feet above the ground or higher; and so this requires a tower. Several of the manufacturers recommend at least one acre of ground on which to place the tower. The turbine will need to be above trees and buildings for the most part so that its access to the wind is unencumbered. Unless you are in a rural (or semi-rural) area, that amount of space can be hard to come by. It goes without saying that you must obtain the proper permissions and construction documents from the local authorities prior to purchasing and installing a wind generator system.

Hoisting the assembled KPAN turbine.

Hoisting the assembled KPAN turbine.

Now let's look at the specific uses I mentioned previously. First, let's assume you are building a new transmitter site on a mountain top, far enough from power lines that it is not economical to actually install a feed from the power grid. One manufacturer's website (out of several) useful for this application is that of Bergey Windpower (www.bergey.com). According to Bergey, if your load draws a continuous power or 50W or less, then a 100 percent PV solution is called for. For continuous loads between 50W and 300W, a combination of PV and wind power makes sense.

Wind and solar power obviously complement each other well; when the sun isn't shining, the wind is often blowing. Likewise, when the wind is calm (like during the summer months) the amount of energy available via direct sunlight is often at its greatest.

The wind turbine installed and in use.

The wind turbine installed and in use.

In this example, the wind generator and the PV system have dc outputs used to charge battery banks that provide power to equipment via dc, or by way of inverters that make 120Vac out of 24 or 48Vdc. It's clear that the amount of energy stored in the batteries must be enough to carry the entire load of the system for some amount of time during which there is no other energy source for recharging. That amount of time will be determined during the engineering process. If the combination of the wind generator and PV are not enough to keep the system powered, a backup generator may need to be added.

It isn't necessary to have battery banks to use the wind generator and PV combination to supplement ac grid power though. Some of the wind generators have 220Vac outputs that can be connected directly to the power grid. A system can be constructed with an ac output from both the wind generator and an inverter powered by PV cells. These inverters sense the line voltage and phase of the grid, adjust themselves accordingly, and then connect themselves so that they provide energy to the load, either supplementing or completely replacing (depending upon the wind and solar resources available at the moment) the power absorbed from the public utility source.

Setting the rebar before pouring the tower foundation.

Setting the rebar before pouring the tower foundation.

And finally, the wind generator can be installed to operate on its own, providing ac power for the load, supplementing that drawn from the public utility, or depending upon the wind resource available at the moment, completely replacing that drawn from the public utility. That of course is the ideal, and the amount of time during which that actually occurs will depend upon the average wind resource available along with the average load seen by the wind generator.

Wind generator manufacturers

There are several wind generator manufacturers I want to cover in this article. The first is Bergey Wind (mentioned earlier). The largest wind generator mentioned for this article is the BWC Excel, its 10kW tower-mounted turbine. It comes in a battery charging version — with dc outputs of 24, 48, 120 or 240V. It also comes in the grid-connected version. It's interesting to note that the peak output is in excess of 10kW in the grid-connected version, while it is 7.5kW in the battery-charging version (30 MPH wind speed). Minimum tower height appears to be 60'. Bergey also offers its XL.1, which is capable of 1,000W, but in a battery-charge mode only.

Proven Engineering is a Scottish firm offering several small wind generators including the Proven 2.5 (2.5kW peak) and the Proven 6 (6kW peak).

African Wind Power is another manufacturer of small wind turbines. Its AWP3.7 will source up to 2kW of power in a grid-connect version.



KPAN: a case study

Pouring concrete around the tower base.

Pouring concrete around the tower base.

KPAN is an AM/FM combination located on the high plains of the Texas Panhandle in Hereford (elevation 3,800'). It's been in the Formby family since its inception in 1948, and today is managed and co-owned by Chip Formby. Late in the spring of this year, KPAN installed a Skystream 3.7 from Southwest Wind Power of Flagstaff, AZ (www.windenergy.com/
index_wind.htm
). When I wrote "Feel the Power," KPAN had just started using the Skystream 3.7; but several months have now gone by. Formby has been able to give me more detailed information about why the station purchased that particular unit, and how the performance has been so far.

Formby has been interested in large and small wind turbines since the energy crisis of the early 1970s. As the manager of KPAN, he had been looking at wind turbines for either the transmitter or studio site. Having one at the transmitter with enough output to power the transmitter itself just didn't pencil out because of the project expense and also a very long payback time due to cheap electricity there (11 cents per kilowatt hour). But, he was determined to capture some of the free power that blew by every day; he liked the clean aspect of wind power; and he just wanted to demonstrate that wind power was a viable option. KPAN ended up buying a wind generator for the studio location instead.

Assembling the turbine blades.

Assembling the turbine blades.

I asked Formby why he chose the Skystream, and he told me that it was as much to do with its availability as anything else. He says it's the next generation in wind generators; it's completely self-contained, since the alternator, the inverter and controller are all located within the nacelle itself. There are only two moving parts: the propeller shaft and the rotator ring (which provides yaw so the turbine can point into the wind). A single cable comes out of the unit, providing 220Vac that is meant to attach to the power grid. (Rated output of the Skystream 3.7 is 2kW, measured at 20 MPH. Recently a USDA test unit near Amarillo produced 3.2kW of output in a sustained 35 MPH wind.) SWWP also specifies that very little maintenance is required: Cleaning the blades of bugs, and lubricating the system every 10 years is all Formby expects to have to do.

A crane picks the assembled tower and sets it in place.

A crane picks the assembled tower and sets it in place.

You can get to the nacelle either by laying the tower over, or by way of a bucket truck (KPAN's unit is on top of a 45' mast). Shortly after the unit was brought online, Hereford experienced a strong thunderstorm, with winds of 70 MPH and large hail. The Skystream 3.7 went through the storm with no trouble at all, save a few paint chips on the blades.

I also asked Formby about the performance of the system to date. He told me that it was a little disappointing, since the same unit located at a more rural site nearby had produced about 25 percent more power. He attributes that difference though strictly to the site; KPAN has its Skystream located inside city limits, and it is in the proximity of trees and buildings. Formby expects much better performance of the system during winter, when the trees are without leaves and (of course) the wind blows more consistently. With those performance issues in mind, he expects the payback period for the entire project (which cost a little over $10,000) to be longer than the typical 10-year estimate (unless electricity prices rise unexpectedly in future). It's also important to consider, when figuring the real cost of the system, to learn what tax incentives are available from federal, state or other local authorities. For example, on its website Bergey mentions that California, New Jersey, New York and Illinois all provide incentives for the installation of wind power. Your local utility provider may offer rebates as well.

The installation complete, the construction crew prepares for a group photo.

The installation complete, the construction crew prepares for a group photo.

Formby tells me the whole project looked better and easier on paper, and that if you were strictly concerned with the dollars and cents aspect, that you'd be better off with your money in a CD for 10 years. At the same time, we know that dollars aren't the only consideration and he feels the time will come when payback won't enter into the equation as much, and that a wind generator (especially in the Texas Panhandle — an area T. Boone Pickens calls the wind corridor of the U.S.) will be viewed as just another part of the facility.

While large-scale wind generation (or the lack thereof) is often brought to our attention in the mass-media, the reality is that small-scale wind generation has been around and available for years. What's old is new again. Our nation's current concerns about our long-term energy needs have prompted manufacturers to produce new models, to the benefit of potential new users such as broadcasters. The time may be right for your station to generate some of its own power. No one can say for sure the direction energy prices will go; but there certainly is a great possibility that they could make you look like a clairvoyant genius, five to 10 years down the road.


Irwin is transmission systems supervisor for Clear Channel NYC and chief engineer of WKTU, New York. Contact him at doug@dougirwin.net.


Resource Guide

Bergey Wind
www.bergey.com

Proven Engineering
www.provenenergy.co.uk

African Wind Power
www.africanwindpower.com

Southwest Wind Power
www.windenergy.com


More photos of the KPAN turbine installation are posted online at RadioMagOnline.com



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