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US startup begins producing 40%-efficient thermophotovoltaic cells

pv-magazine.com

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Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#101

Post by cma »

leereeves wrote: post #63
pbmonster wrote: post #62

Earlier quoted context omitted.

If you shine solar radiation on a nice black carbon sphere, practically all of those photons are absorbed, right? The sphere gets hotter, and starts emitting IR photons. My idea was to now enclose this sphere in TPV modules - except in places where the parabolic mirror puts sunlight on it Let's say that's half of the sphere (but you could cut this number down if you chose a parabolic mirror with a long focal point).…

Wouldn't this process also contribute to climate change by trapping energy on Earth that would have been reflected back into space? Edit: Apparently, yes, current PV solar may also do this: > We found temperatures over a PV plant were regularly 3–4 °C warmer than wildlands at night https://www.nature.com/articles/srep35070 But I suspect/conjecture that turning sunlight directly into heat, then turning some of that he…

That area over PV plants is tiny relative to the size of the world though even with enough of them to power world electricity usage.

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#102

Post by hedora »

kgabis wrote: post #50
goodpoint wrote: post #31

Earlier quoted context omitted.

We already have a fusion reactor at a relatively safe distance called the sun.

We also have this thing called night, as well as weather and seasons.

We also have space lasers and mirrors.

I can imagine some sort of orbital parabolic mirror setup that keeps a few acres at 2000C in the dead of winter and vaporizes any birds that fly over the power plant site.

We're nowhere near the point where that would make sense, but it could let us harness more than the earth's surface area of sunlight for energy production.

It will probably have to wait until after we plunge ourselves into some a perpetual winter trying to mitigate climate change. Of course, a ring world or dyson sphere would make it obsolete.

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#103

Post by gumby »

labcomputer wrote: post #79
londons_explore wrote: post #37

> emitter temperature of 2,400 C GE's combined cycle turbines can get system level efficiency of around 63% from these sorts of temperatures. (For those not familiar with them: They're basically aircraft jet engines followed by steam turbines using the hot exhaust. They are in widespread use to generate electricity from gas, but they can also run off any other liquid fuel, or simply off anything that gets very hot.)

You have to do some “energy accounting” sleight of hand to get 63%, though. That number assumes that some of the low-grade waste heat can be used for, e.g., district heating. It’s also a peak steady-state number, only achievable under optimal load conditions.

> It’s also a peak steady-state number, only achievable under optimal load conditions.

For base load generation at least, these run continuously under “optimal conditions”. The big ones are designed to be switched on and run for decades.

A turbine is a tuned system (its shape is designed for its operating conditions). For base load generation it’s important to fix those operating conditions thus getting the most output from the least input.

(This is quite different for a peaker plant that needs to spin up and down relatively wuickly in response to demand, much less, say, the turbine on an aircraft or locomotive, which go up and down depending on load. They can never be anywhere close to theoretical efficiency).

Just a long winded way of saying that “optimal load” is not as uncommon as one might think. Its no spherical cow.

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#104

Post by whycome »

https://commons.wikimedia.org/wiki/File:NREL_PV_Cell_Record_...

This graphic of photovoltaic cell efficiency (non-thermo) is super interesting: it shows the progression from 1976 and current capabilities (and not necessarily commercially viable or available). The panels you'll get for your home are probably around 20% efficient in ideal conditions.

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#105

Post by digging »

badtension wrote: post #64
awestroke wrote: post #51

Earlier quoted context omitted.

And we also have this looming thing called climate emergency, which should conceivably motivate us to forge ahead with renewables and adjust our energy usage patterns to match production peaks, lest we doom humanity to extinction

I feel like this is one of the biggest missed opportunities. Why do we insist on our energy system to be infinitely flexible and full power available 24/7? Is a habit of doing the laundry at night worth more than additional millions of tons of CO2 in the atmosphere? I understand convenience, laziness and inertia (resisting change) but I also think changing the times when we click "power on" is a simpler solution than…

It's often >90 degrees Fahrenheit at night in for months on end where I live, and houses are built cheaply and in a style completely unfitting a hot climate (that is, thin walls, dark roofs, fully aboveground, thoughtless window placement, etc. Standard American Dumbass style). It's unhealthy to sleep in these conditions without AC, even fatal for some.

So yes, we could survive without power at night. We just have to rebuild every building.

As a long-term ideal I don't disagree with you. We should be building for resilience. But that's not a solution to climate change.

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#106

Post by pbmonster »

amluto wrote: post #96
londons_explore wrote: post #66

Earlier quoted context omitted.

Gas turbines typically are limited to ~1300C to limit NOx production. However, if you have another heat source that doesn't involve combustion, that limit is taken away. And then you can run the whole thing hotter (increasing efficiency substantially). There is no need for blades to withstand the combustion temperature, because film cooling can keep blades far cooler in high speed laminar gas flow. The challenge is t…

> Gas turbines typically are limited to ~1300C to limit NOx production. However, if you have another heat source that doesn't involve combustion, that limit is taken away. As far as I know, combustion isn’t required for NOx formation. If you want to run hotter without producing NOx, you need to eliminate either nitrogen or oxygen. IIRC there are a couple of proposed designs for doing this: combustion in nitrogen-depl…

> combustion in nitrogen-depleted air and chemical looping combustion.

Am I misunderstanding this or are both of those concepts basically "just inject pure oxygen"? And I'm no economist, but running a powerplant on rocket fuel doesn't sound that feasible to me.

Urea injection into the exhaust gas sounds more sensible to me, and even that is seems economically questionable. Fuel prices would need to be pretty high that the efficiency gains make buying urea (instead of just more fuel and running the combustion colder) worth the investment...

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#107

Post by Tuna-Fish »

pbmonster wrote: post #106
amluto wrote: post #96

Earlier quoted context omitted.

> Gas turbines typically are limited to ~1300C to limit NOx production. However, if you have another heat source that doesn't involve combustion, that limit is taken away. As far as I know, combustion isn’t required for NOx formation. If you want to run hotter without producing NOx, you need to eliminate either nitrogen or oxygen. IIRC there are a couple of proposed designs for doing this: combustion in nitrogen-depl…

> combustion in nitrogen-depleted air and chemical looping combustion. Am I misunderstanding this or are both of those concepts basically "just inject pure oxygen"? And I'm no economist, but running a powerplant on rocket fuel doesn't sound that feasible to me. Urea injection into the exhaust gas sounds more sensible to me, and even that is seems economically questionable. Fuel prices would need to be pretty high tha…

No-one sane wants to do combustion in a pure oxygen environment. The solution isn't that, it's to eliminate nitrogen and replace it something else. Typically CO2, because you can get it for free and already preheated by recirculating exhaust.

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#108

Post by hwillis »

gumby wrote: post #103
labcomputer wrote: post #79

Earlier quoted context omitted.

You have to do some “energy accounting” sleight of hand to get 63%, though. That number assumes that some of the low-grade waste heat can be used for, e.g., district heating. It’s also a peak steady-state number, only achievable under optimal load conditions.

> It’s also a peak steady-state number, only achievable under optimal load conditions. For base load generation at least, these run continuously under “optimal conditions”. The big ones are designed to be switched on and run for decades. A turbine is a tuned system (its shape is designed for its operating conditions). For base load generation it’s important to fix those operating conditions thus getting the most outp…

The nationwide average capacity factor for CCGT was 57% in 2020: https://www.eia.gov/todayinenergy/detail.php?id=48036

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#109

Post by pbmonster »

hiAndrewQuinn wrote: post #83
pbmonster wrote: post #45

I don'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. I wonder if you could use this with parabolic mirrors, though. Build a large mirror array, focus sunlight onto a big carbon sphere (maybe…

Maybe my physics knowledge is off here. Why would storing a block of material at a constant high temperature be infeasible? Can't we surround the heated material with a forced vacuum to nullify any heat loss, or am I underestimating something like the rate of diffusion through a pinprick in such material? The fact we don't seem to be able to do this yet suggests I'm missing something, probably several things.

Sure, you can built a thermos (vacuum around the hot storage volume, then highly reflective walls to put the radiating heat back into the storage volume).

The problem is that a tungsten tank filled with molten salt is heavy. If you want to store a couple of MW/h, we're quickly talking about several thousand tons. You have to suspend it somehow inside that thermos. With materials, that don't conduct heat well, but still have some strength at 2000C.

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#110

Post by badpun »

hiAndrewQuinn wrote: post #83
pbmonster wrote: post #45

I don'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. I wonder if you could use this with parabolic mirrors, though. Build a large mirror array, focus sunlight onto a big carbon sphere (maybe…

Maybe my physics knowledge is off here. Why would storing a block of material at a constant high temperature be infeasible? Can't we surround the heated material with a forced vacuum to nullify any heat loss, or am I underestimating something like the rate of diffusion through a pinprick in such material? The fact we don't seem to be able to do this yet suggests I'm missing something, probably several things.

All bodies at temperatures higher than 0K radiate heat, the vacuum around them doesn't stop that from happening.

https://en.wikipedia.org/wiki/Thermal_radiation

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