Solar updraft towers <link> employ a large area of ground covered with a greenhouse type structure. The sun heats the ground and air above it, this tends to rise and can be guided to do so through a turbine and up a chimney structure. Often, the ground underneath the greenhouse structure is blackened to increase energy absorption. We can do better.

Photovoltaic panels are essentially black, and can get extremely hot <link> which actually limits their efficiency in the sort of regions that solar updraft towers might be used. Why not use solar panels to blacken the ground under the green house structure? This would harness the short wavelength light as direct PV generation at ~30% or so and the thermal absorbtion will contribute to the updraft tower. As the PV panels are already under a protective structure, they can be made more cheaply with less protective facing.

Alternatively, a concentrating thermosolar plant, would work well here. They are essentially a parabolic mirror focused onto a pipe - crucially, to the sun, they sort of look black, as all light that hits them is reflected to a small black point. The technology also does not care about the heat under the greenhouse structure. The plant can also be organized such that the steam condenser is at the entrance to the updraft tower collector structure for a further efficiency boost.
-- bs0u0155, Jun 22 2021

Solar Updraft Tower https://en.wikipedi...Solar_updraft_tower
[bs0u0155, Jun 22 2021]

Linear Solar Concentrator https://www.energy....hermal-power-basics
[bs0u0155, Jun 22 2021]

How Does Heat Affect Solar Panel Efficiencies? https://www.cedgree...-panel-efficiencies
"It may seem counter-intuitive, but solar panel efficiency is affected negatively by temperature increases." [Loris, Jun 22 2021]

yup, fair enough. All the designs I saw had PV on top of the greenhouse, which is the dumb way around.
-- bs0u0155, Jun 22 2021


//All the designs I saw had PV on top of the greenhouse, which is the dumb way around//

Electricity is what you want, and photovoltaic cells produce that directly. However, they're generally temperature- sensitive.
The heat in your updraft tower is only a means to the same end. A minimal gain in its thermal efficiency won't be worth it if you lose more than you gain.
-- Loris, Jun 22 2021


//Photovoltaic panels are essentially black, and can get extremely hot//

Ah, that's why trees run that extra water siphon.
-- wjt, Jul 11 2021



random, halfbakery