VAWTs vs HAWTs: Choosing a Residential Wind Energy System
Typically, when people hear that their neighbor wants to install a wind turbine, they shudder as they think of a loud, large, bird-killing machine towering over the trees and obstructing the view from their back porch. However, this doesn’t have to be the case. Vertical axis wind turbines (VAWTs) are a promising solution to moving towards renewable energy in residential areas, be it rural, suburban, or even urban.
Vertical axis wind turbines have many advantages over traditional horizontal-axis wind turbines (HAWTs), particularly for installation in residential areas. VAWTs love turbulence, unlike HAWTs, which have to tower above any other structures or trees to produce a sufficient amount of energy. This allows VAWTs to be smaller, closer together, and in a wide range of places, such as on rooftops, along highways, and between buildings (if you read our blog about Greening the NFL you already know that the Philadelphia Eagles Lincoln Financial Field is run 100% on renewable energy, including 80 VAWTs). Their smaller size almost always guarantees that they come in under height restrictions imposed by local municipalities. VAWTs are quieter than typical horizontal wind turbines because they rotate three to four times slower than HAWTs, guaranteeing that you won’t annoy your neighbor or lose sleep because of a constant humming.
While VAWTs initially may seem like a better option than HAWTs, they do have some disadvantages as well. While some believe there is less wear and tear on VAWTs, concluding that they can be made using cheaper materials and still last longer, others argue the opposite. While the greatest stress on a horizontal wind turbine is at the base of the blade near the hub (the sturdiest part of the blade), the greatest stress on a VAWT is at the center of the turbine, which is not nearly as sturdy as the ends, where the blades are attached. This stress causes more wear and tear on the turbine, shortening the turbine’s life, and requires stronger, more expensive materials.
VAWT... or Not?
For most residential areas, if you own less than two acres of land, a VAWT is the only option. However, there are several other factors besides acreage to consider before purchasing a wind turbine (VAWT or HAWT):
- Consider how much electricity you are consuming. How much will a wind turbine offset your consumption? Before installing any renewable energy system, you should evaluate your energy consumption and take steps to make your home more energy efficient. This will reduce the size of a renewable energy system that you will need, along with saving you money!
- Use wind maps and install an anemometer to determine your wind speed. The U.S. Department of Energy offers state wind maps at an altitude of 50 meters. While wind maps provide a general indication as to whether you should even be considering installing a wind turbine, they typically do not measure speeds at low enough altitudes to provide an accurate wind speed at the height of your wind turbine, so you should obtain a more accurate measurement of wind speed using an anemometer. Anemometer prices range anywhere from $40 to hundreds of dollars.
- Explore tax incentive and rebate options. DSIRE, the Database of State Incentives for Renewables and Efficiency, offers maps of states that offer tax incentive and rebate options. As of December 2011, 18 states offer rebates for renewable energy, and 24 states offer tax credits for renewable energy.
If you do decide to purchase a VAWT, it is courteous to talk with your neighbors first despite the turbine's reduced impact when compared to HAWTs. Explain to them the benefits and the steps you will take to mitigate the impact the turbine might have on them. Hopefully you will be pleasantly surprised by their response, and possibly even their amazement that a wind turbine doesn't have to tower above the trees. Who knows, maybe you will be a VAWT trend-setter in your neighborhood!