No, the Wikipedia article is still fundamentally out to lunch, because the conflate cooling mechanisms with the heat source. It really is unexcusable to be that sloppy.
I'll try one last time to explain this correctly.
1) Start with a well insulated building having NO windows. All walls, and the roof, are say R30, the building is nearly airtight, and the cement slab floor has R15 UNDER the slab. The building exterior is a good approximation of white, both walls and roof. The building is located in a cold but sunny region in the wintertime. I.e. the sort of place that would need a greenhouse to grow plants. There is no building heat or cooling systems.
So this building is, to a reasonable degree, convectively, conductively, and radiatively isolated.
What is the inside temp of this building? Does blocking convection heat it? LOL!
The inside temp is, to a very good degree, the mean of the outside temp. The inside temp does not fluctuate much during a day (perhaps a +/- a couple of degrees) while the outside temp might fluctuate 30 degrees from night to day.
Now, replace the R30 roof with a transparent glass roof. Assume the glass multi-pane, so still has reasonably low conduction, and of course is still close to airtight. Now what happens?
Well, we have a greenhouse now compared to the original building. It is heated by radiation during the day, and loses heat by radiation (of a different spectrum) at night. The average temp of the interior is now significantly higher than the original building, due to all that radiante heat coming in during the day. However, the temp does fluctuate more on a daily cycle because energy enters during sunlight hours and net exits during the night. The equilibrium temp can be estimated pretty well by using only radiation equations, and using an average temp for the blackbody terms. That is exactly what is down with the earth calculations.
If glass is used, then this cladding functions like the GHG of the atmosphere, that is it boosts the building temp a bit more due to the spectrum interaction. If plastic is used which does not have the same spectrum interaction, the building temp will be a bit lower than if glass is used. So think of glass as being like adding CO2, Methane, etc, while plastic is like lacking those. In both cases the greenhouse does have H2O which is also a GHG.
In both cases, the actual air inside the greenhouse is irrelevent to any calculations. If you go through the numbers you will find that the heat capacity of the air is negligible. So all the nonsense about how the air is heated convectively and rises and falls, is all worthless. It does not enter significantly into the energy calculations at all and can and should be ignored. It is just a red herring to distract you.
In the same sense, starting from wind blowing through your building instead of starting from a closed building as I did above is wrong as well. That is what leads people to claim convection is "heating" the building. LOL! |
