<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>perihelions</author><text>You won&amp;#x27;t get the claimed efficiency that way: it only applies to an enclosed heat source. It&amp;#x27;s critical that they&amp;#x27;re reflecting light outside of the PV bandgap back into the thermal mass, where it&amp;#x27;s re-absorbed and re-emitted again.&lt;p&gt;If you try that with solar radiation, you&amp;#x27;ll lose most of it back into the sky.&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.nature.com&amp;#x2F;articles&amp;#x2F;s41586-022-04473-y.pdf&quot; rel=&quot;nofollow noreferrer&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.nature.com&amp;#x2F;articles&amp;#x2F;s41586-022-04473-y.pdf&lt;/a&gt;&lt;p&gt;(Equation 1 and surrounding discussion, and the energy-flow diagrams in Figure 1).</text><parent_chain><item><author>pbmonster</author><text>I don&amp;#x27;t get why they go for storage with this. Storing a block of carbon or tungsten at 2000°C for hours or days does not sound like something that will ever be economical. A battery leaking energy this quickly (and it will leak₎ will need to be incredibly cheap to ever make sense.&lt;p&gt;I wonder if you could use this with parabolic mirrors, though. Build a large mirror array, focus sunlight onto a big carbon sphere (maybe coat it with one of those new materials that are transparent for visible light but pretty reflective for IR), cover the top of the sphere in those new panels. They are more efficient than practically all solar cells and get much more power out the same area than solar cells. This should beat a photovoltaic parabolic mirror setup, right?</text></item></parent_chain></comment><story><title>US startup begins producing 40%-efficient thermophotovoltaic cells</title><url>https://www.pv-magazine.com/2023/01/25/us-startup-begins-producing-40-efficient-thermophotovoltaic-cells/</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>kolinko</author><text>Carbon or tungsten I don&amp;#x27;t know, but sand as a thermal energy storage medium can be quite economical. Energy loss scales with the surface area (^2), energy stored with volume (^3).&lt;p&gt;With grid scale, above certain dimensions, you can store energy for months while maintaining economic viability.&lt;p&gt;Even for single days or weeks it makes sense. You need hot water in your home 24&amp;#x2F;7, but sun doesn&amp;#x27;t shine every day in most regions.</text><parent_chain><item><author>pbmonster</author><text>I don&amp;#x27;t get why they go for storage with this. Storing a block of carbon or tungsten at 2000°C for hours or days does not sound like something that will ever be economical. A battery leaking energy this quickly (and it will leak₎ will need to be incredibly cheap to ever make sense.&lt;p&gt;I wonder if you could use this with parabolic mirrors, though. Build a large mirror array, focus sunlight onto a big carbon sphere (maybe coat it with one of those new materials that are transparent for visible light but pretty reflective for IR), cover the top of the sphere in those new panels. They are more efficient than practically all solar cells and get much more power out the same area than solar cells. This should beat a photovoltaic parabolic mirror setup, right?</text></item></parent_chain></comment><story><title>US startup begins producing 40%-efficient thermophotovoltaic cells</title><url>https://www.pv-magazine.com/2023/01/25/us-startup-begins-producing-40-efficient-thermophotovoltaic-cells/</url></story>