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Comment by zdkl | Hacker News Reader

Re. thermal gradients, have you considered plain old mirrors? https://en.wikipedia.org/wiki/Odeillo_solar_furnace

> 54 metres (177 ft) high and 48 metres (157 ft) wide > more than 2,500 h/year [sunlight] > peak power of 3200 kW > Temperatures above 2,500 °C (4,530 °F)

Sounds like it could be useful as a "default load" inside an otherwise inactive solar furnace at least.

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You're describing solar thermal energy [1]. Use solar collectors to turn light into heat, then use a heat engine to turn that heat into electricity. This TEG could be used as a heat engine for this task. But again, our heat engines are already capable of this task and don't need such high temperatures. A solar collector array even getting to this TEG's operating temperature might not be feasible.

Photovoltaics just turn solar energy into electricity, and don't need the heat engine. This has made them way cheaper to deploy than solar thermal energy. So unless there's something very important about this new TEG, the solar thermal vs photovoltaic calculus doesn't really change.

1. https://en.wikipedia.org/wiki/Solar_thermal_energy

The point is to store the thermal energy for later use to smoothen out photovoltaic's intermittency issues.

Right. But we already have that technology with conventional heat engines which have the advantage of much, much, lower operating temperature requirements. If you have a 3,000 degree vat of thermal storage material this new engine stops working after draining 1000 degrees. Existing heat engines can usually work down to several hundred Celsius - though superheated steam engines need around 700 Celsius. But that's still an extra 1000 degrees you can bring it down, even in the conservative case.

This is the first of its kind to reach this efficiency, correct?

I assume that means there could be room to significantly improve its efficiency or operating requirements with more investment and research.

Having one example, even if 'useless' or elementary, is key to developing new technology.

Compared to other TEGs. Not compared to steam turbines. The article is actually being very generous in saying it's "as efficient" as steam turbines. Steam turbines are more efficient with scale, and industrial ones for power generation are over 90% efficient [1]. This new TEG's efficiency is "around 40 percent". Higher than the previous TEGs in the 25-35% range. But not compared to steam engines, that also benefit from much lower operating temperatures.

1. Multistage (moderate to high pressure ratio) steam turbines have thermodynamic efficiencies that vary from 65 percent for very small (under 1,000 kW) units to over 90 percent for large industrial and utility sized units.

https://www.epa.gov/sites/default/files/2015-07/documents/ca...

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