Solar Powered Fans myth and marketing deception
Solar powered fans are rated according to fan displacement at maximum speed in free air conditions
That is a fan in a tube, with nothing on top and nothing below, at maximum speed which would be ostensibly at full light and driven not necessarily by the solar panel accompanying the fan as a product.
The minute the flow encounters resistance, like the cap on a solar fan roof ventilator or the free air available on the intake side, performance values are decimated when compared to those claimed. Add the variances of light available on the day you can reduce those ratings further again until they are only a fraction of what is claimed.
The solar panel is the energy side of this equation so look at the life expectancy as claimed by the manufacturer or the marketing company. There’s no point to going to the trouble of installing the unit just to find some months later that you have is a solar powered frittata because if the warranty doesn’t cover the labour you’re going to be up for the same costs again and again….or until you fall off the roof.
And after all of that remember…you don’t have a roof ventilator that works at night….which is when you really need it for the evening purge.
In the meantime they’ve got your money and you have an education such as it is because like as not, an education always comes at a cost and this is where the calibre of teacher sought is important.
Now you might say it shouldn’t be allowed, and even if the performance testing parameters were defined on the packaging, very few would understand them.
So it’s Buyer Beware…..more so as time passes