Energy efficient devices for your home???

I keep getting asked about the various Energy producing devices you see 
advertised on the net.  Her is an example of   some wind power 
generation devices to consider.  When dealing with wind power you have 
to go back to the very basics of dealing with SLUGS which is the air 
mass that you wish to extract energy from. Here is a great fact sheet 
from NASA.

     https://www.grc.nasa.gov/WWW/K-12/airplane/airprop.html   Do your 
math an you will realize that the devices being sold to home owners will 
only charge some batteries when the wing is blowing and you will darn 
sure not power your home.

https://www.treehugger.com/wind-technology/new-scalable-wind-turbine-said-be-urban-tolerant.html

https://inhabitat.com/the-windstrument-wind-turbine-provides-renewable-energy-with-its-orchid-like-design/?variation=d

As far as solar is concerned you have to go to the very basic fact that 
there is only one kilowatt per square meter under ideal solar 
conditions.  When you back out the efficiencies of collecting, 
conversion into useful power you find that the concentrating collector 
driving a Stirling heat motor only achieved a 35 % overall efficiency. 
Best Case.

https://www.sciencealert.com/engineers-just-created-the-most-efficient-solar-cells-ever

https://phys.org/news/2013-06-solar-cell-world-highest-conversion.html

https://www.sciencedaily.com/releases/2015/09/150902093301.htm

n.wikipedia.org/wiki/Solar-powered_Stirling_engine

https://www.stuff.tv/news/giant-flower-shaped-solar-panel-tracks-sun-across-sky-maximum-power 
Read carefully the claims.   18 square meter design collects generates 
roughly 4,000 kWh per year. Divide by 365 days/ year and you get a 
little less than 10 kwh per day divided by 8 hours of useful sun light 
which equals to 1.3 kw.

Remember to go back to the basics of one KW/ square meter on sun light 
infall under  ideal conditions.

Please don't get trapped into the false belief that you can force 
multiply such as the Solar Boys that say, I'll just get a parabolic dish 
and multiply the Solar Energy.  WRONG, for under ideal conditions and 
latitude at high noon, clear day there is an in-fall of Solar Energy 
that is one kilowatt/ meter square.  You can concentrate and jack up the 
temperature but the sum total of energy/ square meter is still the same.