By small footprint I mean compact design, rather than long blades spinning at very high speed catching birds off guard. The same power producing area can be incorporated in a verticle spinner that doesn’t extend out like a blade. A spinning cylinder is easier for them to see and avoid.
By small footprint I mean compact design, rather than long blades spinning at very high speed catching birds off guard. The same power producing area can be incorporated in a verticle spinner that doesn’t extend out like a blade. A spinning cylinder is easier for them to see and avoid.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ok....You are talking about a few different things in the three sentences of your Post 13.
“The same power producing area can be incorporated in a verticle spinner that doesn’t extend out like a blade.” There is nothing more compact about Vertical Axis Wind Turbine (VAWT) than there is about a Horizontal Axis Wind Turbine (HAWT). In fact, the opposite is true when looking at the issue from the perspective of ‘power per unit area’. The amount of power that any wind turbine produces is related to the swept area that impacts the blades. In a HAWT, the area impacted by the wind (ignoring the hub for the moment as being negligible compared to the overall area) is pi x (radius) square i.e. the swept area. For a VAWT, that area is diameter x height (of the cylinder). Speaking in terms of generalities, a HAWT is substantially more efficient than a VAWT….. this of course stands to reason since for half of the cycle, a VAWT turbine is moving against the wind as opposed to with the wind.
Here’s a calculator for you…. It’s not the best but I don’t want to spend too much time looking for a better one and it will suffice for the purpose of this point. https://www.omnicalculator.com/ecology/wind-turbine#how-to-calculate-the-power-generated-by-a-wind-turbine At the top of the calculator, you can select whether you want to use it for a VAWT or a HAWT. First do a HAWT calculation…. Put in a 10 foot diameter blade and a wind speed of 25 mph. You should get 6.442 kW output after the losses have been subtracted for a turbine spinning at 210 rpm. Now select a HAWT and play with the diameter and height for the same 25 mph wind. Let’s say you try to maintain a 3 to 1 ratio of turbine height to diameter ratio…. To get the same 6.44 kW output power, the VAWT has to have a diameter of 10.25 feet and a height of 30.75 feet and this is for a turbine spinning at 410 rpm. Not surprisingly, the area swept for the VAWT is essentially the same as the diameter x height for the HAWT…. This is because the flaw with this calculator is that its default efficiency is the same for both the HAWT and the VAWT…. while the theoretical efficiency of a VAWT might be similar to a HAWT, most empirical tests show that VAWT designs end up much lower… typically about ½ to ¾ of what the efficiency of a HAWT is. That being the case, the area has to be increased to get a similar power output for the VAWT.
Will a HAWT design actually ‘catch more birds of guard’ than a VAWT design? I doubt it but I’d be interested in looking at a study that actually does a good job of trying to set up an ‘apples to apples’ comparison.