Wind Turbine FAQS

Answers to Questions about the St Croix Reformed Church Wind Turbine…

How much money did it cost?

The cost of the turbine, tower, and installation was $66,000.  The turbine itself was $25,000. The tower was $16,000 which is a bit more expensive than other towers in the states because ours comes with a motorized jack so that it can be lowered for hurricanes. Other costs included the wind reporting/anemometer package and foundation. Our shipping costs were about $5000 of the total.

Who paid for it?

The church put up $16,000 from its Reserve Fund. The remaining $50,000 came from a US Energy Department grant, administered by the VI Energy Office to non-profits in the territory. We applied for the grant in 2010 and were one of 19 island non-profits that received an award.

How much money will it save?

Based on average windspeed, cost of electricity, and the turbine’s capacity, we estimate the wind turbine will  save us between $400 and $600 a month depending on our electricity usage and windspeed.  During windy days and windy times of the year, the excess generated power will be banked with the electric company as a credit.  Thus, if we generate $600 in power one month, but only use $400, the savings can be applied at some other time of the year should we generate less and use more. The savings will be reinvested in mission, energy upgrades to the building, and set aside for turbine maintenance. Learn more about the formula for disbursal.

What will the church do for electricity when the turbine isn’t turning?

The church will still be hooked into the power grid. The turbine feeds energy into the grid. There are no batteries. This arrangement is called “net metering.” The church will have two electric meters: one that measures consumption, and the other which measures the amount being generated by the turbine and fed into the island power grid.

How noisy is a wind turbine?

That depends on how fast it is turning, how close you are standing, and whether you are standing up-wind or down-wind. On average, at 70 feet away it will be as loud as a normal conversation (60 decibels). Thus, it will not be heard from within the church building or by neighbors.

How long are the blades and how close to the ground are they?

The composite blades are 13 feet long, -making the “sweep” diameter about 26 feet across. On our 60 foot tower, this means the blades are 47 feet above your head.

Why does the church need a wind turbine?

Electricity costs in the USVI are the highest in the USA. We are currently spending about $500 a month on electricity, and that’s without A/C in all but the office. Kilowatt costs are rising. By erecting a wind turbine, we will not only address our power needs, but hopefully serve as a forerunner and inspiration to the rest of the island as it struggles with increasing utility costs.  The Kingshill School located at our church was closed in 2012 due to economic conditions on the island and the loss of the island’s major employer. It’s electrical bill was being paid by the church as a mission. So while our electricity consumption has gone down with the loss of the school, our KWH costs are rising due to economic conditions. (WAPA, the local energy provider uses expensive fuel oil and has antiquated equipment.)

How do height and windspeed affect the turbine?

On average, we expect windspeeds of 10-14 miles per hour. Windspeeds increase exponential every 10 meters from the ground. Thus, the average wind speed 60 feet off the ground is significantly higher than on the ground. Even a one-mile an hour increase in windspeed can significantly increase the power output of the turbine.

The following chart shows how kilowatt production jumps as windspeed modestly increases.

Avg Wind Speed    kwh per month
 7.8                55
10.1               115
12.3               195
13.4               235
14.5               270

The power available in the wind is proportional to the cube of its speed, which means that doubling the wind speed increases the available power by a factor of eight. Thus, a turbine operating at a site with an average wind speed of 12 mph could in theory generate about 33% more electricity than one at an 11-mph site, because the cube of 12 (1,768) is 33% larger than the cube of 11 (1,331). Conversely, little power is harvested at low wind speeds. We hope for an average of 12 mph., though as you can see, a really windy day can make up for a lot of slow wind days.

Ground turbulence and wind quality are other factors affecting the turbine’s efficiency. Our location on a hill with few surrounding obstructions makes it a good place for a turbine.

Average windspeeds at our church are around 12 mph.

What if the turbine blades are not turning, or are turning slowly?

Ideally the blades will always be turning and the wind will always be blowing at least 12 mph.  Above average windy days will compensate for below average days.  Bergey’s 10Kw turbine will start turning at just 4 mph, however, electrical production jumps exponentially as windspeed increases. Thus, a 14 mph wind generates much more than twice the power of a 7 mph wind.   On really windy days or nights, it will outperform its average output and that energy produced is fed into the meter and banked (credited) to our bill.

The turbine can withstand winds up to 125 mph.  During high winds, the electronic “auto furl” feature of the turbine’s tailfin will take over to reduce blade speed. It will point the blades slightly out of the wind to reduce blade speed back to its optimal range and safety. The turbine tower can also be LOWERED during hurricanes.

Because we will still be connected to the power grid, we will still get electricity no matter how slow the wind is blowing (as long as the grid is up!).

Why did we choose a Bergey brand turbine and A.R.E. tower and Mayan Windpower?

Bergey is one of the oldest turbine manufacturers in America. They have excellent equipment and electronics, and a generous 10 yr warranty which spoke volumes to us.

American Renewal Energy’s 60 tower can be lowered by a motorized screwjack. They are one of only two tower manufacturers with such a design.

Mayan Windpower is owned by Jeff Cabrera, an expert in tower & turbine installation and maintenance, and in working with turbine electronic packages. Jeff also joined the church as a member.

  See “the story of our turbine” for more details.

Why did we choose wind over solar?

We are in a windy location!  And we didn’t have enough efficient roof space (at the proper angle) to install 10kW worth of solar panels. Solar panels would also be subject to storm damage, and the prospective of removing a roof load of them for hurricanes did not amuse us.

We  believe that BOTH solar and wind power are a big part of the island’s future and hope the VISIBILITY of our turbine and tower to the island and our member will encourage the island in this regard.  At our church, the roof location where we might have installed the panels would have been invisible, as we could not attached them to our angled roof. It was the wrong pitch and not big enough.

What does “10 kW” mean and how much will the turbine generate?

“kw” means “Kilowatt”. It is a measurement of “how much” electricity a thing either consumes or produces. 10 kilowatts = 10,000 watts. A kilowatt hour (kwh) is how much electricity is produced or consumed in one hour and is often used to measure the cost of electricity. A “10 kW turbine” operating at an average wind speed of 12 mph will generate 10,000 kilowatt-hours of electricity a year.

For comparative purposes, a refrigerator freezer uses about 6 kilowatt hours (kWh) per DAY.  A window air-conditioning unit will use about 1.3 kwh per HOUR. Run it for 8 hours and you are using about 11 kilowatt hours a day. 1000 watts of light bulbs turned on for eight hours, will use 8 kilowatt hours of energy during that day.  The  turbine would need to produce 15 kWh a day to cover the cost of 1 AC, 1 frig, and ten 100 watt bulbs. On many days, it will produce much more than that. Somedays, less.

Our Bergey Excel current conditions

real-time data streaming from our turbine

How will the Turbine be operated and maintained?

Installed in the church are numerous power inverters and a computer brain which monitor the system. It automatically feeds data via a weblink to the readouts you see above. Kingshill School students will be able to monitor the system, including energy production and statistics, via an online data page.  A member of the church with a wind turbine background oversees operations and maintenance.

Wind data is being shared with the VI Energy Office so that it can help others consider the potential of windpower.

Have a question? Email neilmacqueen@gmail.com

 

For the latest announcements about the installation schedule, click the TURBINE NEWS category link in the righthand column>>

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