Wind energy is a renewable energy resource that is viable, interesting to study, and fascinating to observe. But it's also a challenge to harvest wind energy because unlike solar energy, the wind resource isn't the same everywhere. It depends on the things like the elevation, the terrain, and the time of year. So siting a wind turbine requires careful consideration and sometimes it's not a good fit at a particular site. In fact, every installation will like have some issue that will need to be carefully thought through to make the installation successful. Here are a few issues to consider when considering installing a WfS turbine at your school:
1. Check your expectations - the WfS turbine isn't going to power the school
Sometimes folks get too excited about wind energy and overestimate the impact of the WfS turbine. The turbine won't power the school. It generates about 2 kW of power at full rated power and your school requires 100's of kW of power. So at best, it will provide a very small percentage of the energy consumed at the school. Its real value is as an educational tool.
2. Any turbine needs a clear view of the wind to perform well
The guidelines from Southwest Windpower suggest that the turbine should be placed in an open area at least 20 feet above obstacles within 250 feet. The standard WfS package uses a 45 foot tower although 33 foot and 70 foot towers are also available. So look at the trees, buildings, and other obstacles near the school and think about whether they would block the wind during the windiest parts of the year.
3. The turbine needs to be far enough away from the school to get smoother, higher velocity wind
To get the best performance, the turbine should be located about 2 times the height upstream or 15 times the height downstream of the tallest obstacle. So if your school building is 20 feet tall, the turbine would need to be located 300 feet downstream of the building if it shields the wind.
4. But the turbine needs to be close enough to the school to reduce losses in the wiring
The farther out that the turbine is located from the electrical connection (either at the school or a transformer), the resistance losses in the wire get larger. So the wire size needs to be increased the farther out the turbine is located, increasing the installation costs.
5. The connection to the electrical grid at the school needs to be carefully considered
The Skystream turbine has a sophisticated inverter that monitors the frequency and the voltage of the electrical system that the turbine is connected to. The inverter is UL listed and one UL spec is that the voltage increase caused by the turbine when it pushes power into the system cannot exceed 10% of the system voltage. So if the service to the school is 208V and the voltage on each is 120V nominal, then the turbine will shut down if the voltage in the electrical distribution system exceeds 132V. So if the turbine is located too far from the school and the wire back to the connection is not carefully sized, then the turbine might shut down at lower wind speeds. This won't damage the turbine, but the turbine will not operate for as many hours per year as it should.
It's also important to consider the electrical system at the school and the service that you get from your utility. If the voltage in the utility's system is higher than nominal, than the turbine might experience the same premature shutdown scenario. Of if the equipment in the school (like the air conditioning or any other large electric loads) causes the electrical system to trip at the school, this might not be a good application for a turbine installation.
6. The turbine must be able to communicate back to the school
The turbine uses a Xbee 2.4 Mhz wireless communication system to transmit performance information about the turbine back to a receiver located inside the school. This system is built for a residential installation and can readily get through standard wooden stick and frame construction. But at a school, the wireless system may have a hard time getting through concrete walls and metal framing. The furthest distance we've been able to get a signal back to the school is about 350 feet.
7. You'll probably want to share the performance of the turbine with the rest of us
When the wireless signal gets back to the school, it's picked up by another Xbee receiver with a USB connection that should be connected to a dedicated desktop computer that is running the Southwest Windpower Skyview software that comes with the turbine. To be most effective, you'll want to share this data with other schools in you District. We can also arrange for a way to push the data through your school's firewall and to a site at Idaho National Laboratory that is set up to host the data from WfS turbines across the U.S. But you'll want to make sure your IT/tech person is involved and can understand how the system works.
8. Of course, you'll want to be a good neighbor so you'll want to talk to the neighbors about noise and visual impacts
Like any construction project or even a large wind farm, you'll want to consider the neighborhood where the turbine may be located. The turbine doesn't make a lot of noise (the wind tends to mask the noise when it blows), but it's not completely mute either. Again, the turbine is built for a residential installation, so it's got to be mostly quiet.
You'll also want to consider the visual impact. The standard WfS package uses a 45 tower and the blades are about 6 feet long so the tallest point is about 51 feet. This it likely about 20 feet shorter than the lights on your football field. But you'll want tp consider whether this is a good location if it blocks the view of the Pikes Peak from your neighbor across the parking lot from the school.
9. The foundation of a good installation is a good foundation design - what's your soil like?
One of the biggest unknowns in the cost of the system is the foundation required for the turbine because the properties of the soil at the site need to be determined for the building permit and for the foundation design. So if the best site is located at a spot like near a football field where the soil has been amended and watered to that the soil strength is low, then the foundation will likely need to be larger or deeper. The same is true if the soil has a lot of clay. So if the foundation for the school building was built on clay and you've got cracks in the floors from settling, chances are the same will be true at the turbine.
10. You'll want to consider the maintenance you can provide
The turbine comes with a 5 year limited warranty from the manufacturer, but the turbine is expected to last 15-20 years. There are very few moving parts and there are no bearings that need to be greased. But the tower should be examined for level every year or so and you may need to be able to get to the turbine (for example, if the antenna needs to be tightened or replaced). So access to a cherry picker is helpful. The CSU WAC also has the necessary gin pole and winch to assist any dealer/installer that needs it, so that canalso be arranged. You may also want to make sure you can tap into some electrical and IT expertise during install. You should also be able to contract with the certified turbine installer/dealer for an annual maintenance checks and services.