Wind Turbine and Solar Panel
The wind turbine is the heart of the project as it produces the electricity required to power the Wi-Fi equipment and power meter. The turbine has gone through numerous iterations due to failures and performance enhancements. Recently, a 30W solar panel was added to the project to prevent the batteries from running low during the summer and fall when it isnít windy in Rochester. The power that the turbine and solar panel produce is stored in two Trojan T105 6V deep cycle batteries connected in series. The communication equipment can run for about two weeks without recharging, so between the wind turbine and solar panel the project can run year round. The batteries are connected to a charge controller to prevent over charging during periods of high wind when the turbine produces a great deal of power.
The wind turbine was built using parts easily found at the hardware store and local junk yard. Sadly solar panels are something that canít be built from easily sourced materials so we purchased it on eBay. We were lucky to find two DC permanent magnet motors for the turbine which produced around 6 volts when turned by hand. Sadly after years of abuse these two motors eventually broke, a bearing failed on one motor while the other had a magnet dislodge. These failures are most likely the result running the motors outside their designed specifications. To improve reliability and performance we switched to a commercial grade 1/4HP 90V DC motor. So far this motor has taken the abuse of sustained 50MPH winds without any issues.
The tower was built using metal stakes, iron piping, electrical conduit, and steel wire. We originally used plastic stakes and nylon rope to secure the tower. This worked fine until there was a wind storm which both ripped the stakes from the ground and stretched the nylon resulting in a tower collapse. As a majority of the parts were easily sourced, rebuilding the tower and turbine was not an issue. The only element of the wind turbine that wasn't easily purchased or found was the wind turbine blades. At the beginning of the project we made some blades out of a PVC pipe and there are numerous guides on how to produce them on the Internet. An issue that we quickly ran into was that the durability of the PVC blades. Rochester frequently has storms that blow through with wind speeds greater than 50+ MPH, something that the PVC blades could not deal with. Eventually we settled on a pair of blades similar to the ones that are used on the commercial Air-X wind turbine. These blades were durable, achiev ed high RPMís, and were readily available on the Internet. The best performing blade was in fact a single wood prop, but some carelessness during testing meant that the blade was destroyed. The many lessons gleaned over testing have made the turbine far more reliable than when the project first began.
The performance of the wind turbine and solar panel are a popular question. The maximum power generated from the wind turbine has been 120W while the solar panel has yielded 25W. While the wind turbine can produce over 100W in high winds, on moderate windy days it usually produces only between 15-30W. On days that arenít windy it doesnít produce anything, meaning that the solar panel usually outperforms the wind turbine. Both power sources are the perfect combination for the Rochester climate as the winters are windy and cloudy while the summers are sunny with little wind.
From our data, the capacity factor for the solar panel has been far higher than that of the wind turbine. The logic behind this is that there are far more sunny days than days with wind speeds above 20MPH. Many commercial wind turbines have powers ratings corresponding to wind speeds from 25-30 MPH, which in many regions are rare. This means that a 400 watt wind turbine might max out at 50 watts during an average day. During a storm the turbine will produce 400 watts but again, this occurrence is rare. Another important element is the cut-in speed of the turbine. There could be a light breeze, but if the wind speed is less than the cut-in, the turbine will spin but not produce any power. A good rule of thumb is that there needs to be at least a 15MPH breeze to generate any decent amount of electricity from a wind turbine.