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Combined Solar Updraft Photovoltaic/Concentrating Thermosolar Plant

Use existing solar tech as the thermal collector
  [vote for,

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]

Solar Updraft Tower, 2014 article http://buildingdesi...olar-updraft-tower/
Suggests PV or solar thermal in the greenhouse [a1, 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]

High temp PV hybrid https://onlinelibra...1002/adfm.201503597
A solid-state photoelectrochemical cell [a1, Jun 22 2021]


       The idea title isn’t long enough.
a1, Jun 22 2021

       Not a new idea? Linked article from 2014 says "Solar thermal collectors or photovoltaics can be arranged inside the collector greenhouse. This could further be combined with agriculture."
a1, 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

       It does make more sense to have them inside. But if you're collecting energy via solar thermal, you're NOT sending it up the tower to drive a turbine. PV might only extract a few percent in a very narrow range of wavelengths.   

       I wouldn't even know where to start on the math to figure out which is a better scheme, how much each collection method contributes to the total output. Do you?
a1, 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

       Unless someone has made progress on high- temperature photovoltaics <link>
a1, 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


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