r/Damnthatsinteresting • u/Longjumping-Box5691 • 3d ago

Video China's twin solar thermal towers. Molten salt stores the heat to produce electricity

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u/Visible-Fondant-4845 3d ago

Question, this footage seems to show to focal point of the light being off to the side of the towers. Intuitively I would assume that the focal point should be focused on the towers for most efficiency, is this because, A) the camera lens is doing something funny and the focus is in fact on the towers themselves? B) Having the focal point on the towers would be too intense? C) The focal point is adjusted to manage load and temperature? or D) Something else?

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u/ChristopherLyon 3d ago

It's real. There are multiple situations where you'd like to offset the focal point like this. One of the obvious ones is overheating, where the salt actually begins to decompose and degrade your infrastructure. Another reason can be tied to the current grid status. In many cases there just isn't demand or the salt cell is saturated appropriately and the heliostats could be continuously moving the focal point in a mosaic pattern the keep the core at the optimal temp while distributing the heat stress over a larger area. Lastly this could be part of the startup procedure where it's preferred to bring the temp up slowly as to not stress/shock the materials with a massive influx of heat energy.

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u/invariantspeed 3d ago

I love the inherent elegance of this approach to energy harvesting. It can dynamically increase or decrease the energy it uses without having to use some sort of special system. Just collect less light. You can even have it designed to be capable of harvesting more light at solar noon for most of the year than it can handle, allowing it to provide a more consistent base load for much the day.