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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
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
Solar Updraft Tower
[bs0u0155, Jun 22 2021]
Linear Solar Concentrator
[bs0u0155, Jun 22 2021]
Solar Updraft Tower, 2014 article
Suggests PV or solar thermal in the greenhouse [a1, Jun 22 2021]
How Does Heat Affect Solar 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
A solid-state photoelectrochemical cell [a1, Jun 22 2021]
||The idea title isnt long enough.
||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
||yup, fair enough. All the designs I saw had PV on top of the
greenhouse, which is the dumb way around.
||It does make more sense to have them inside. But
collecting energy via solar thermal, you're NOT
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.
||//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-
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.
||Unless someone has made progress on high-
temperature photovoltaics <link>
||//Photovoltaic panels are essentially black, and can
get extremely hot//
||Ah, that's why trees run that extra water siphon.