Cool. So it basically improves water's efficiency to absorb energy in the form of light.
Can the same idea be applied to improve water's efficiency to exchange heat, to make it cool easier? Then you can slap a turbine and have the perfect steam generator.
Cooling it isn't hard, when the steam hits the turbine it loses a lot of its energy and will inevitably cool down and condense. Then you just pump it around back into the chamber and re-steam it.
I work in the solar thermal industry - my company (http://www.sunapse.co) builds software for solar thermal power plants. I can say with some authority that this is legit and VERY promising tech.
the way I read this is that they put black particles that adsorb heat better in the water. That makes this produce some steam fast. I do not see how this would produce more steam than, say, a thin layer of water on top of a thin black-painted sheet that is well-insulated from below (sun heats black sheet; sheet heats water).
How is producing some steam rapidly an improvement?
So, them being 'black' isn't really the point. The point is the potential to get steam from water at lower temperatures, in less time.
If you are dealing with A LOT of water (if you were to scale this to power-plant scale), you are dealing with large 'thermal mass'. This means you need a lot of heat over time to raise all the water to a high enough temperature to create electricity.
If you run a power plant, you want flexibility. You want to switch on your power plant fast, and then shut it down when you want, without cost. This lets you speculate on the electricity market, and be more available if there is a sudden spike in electricity demand. If you're dealing with large thermal mass, you don't have this flexibility.
Also lots of advantages of lower cost - not needing heat exchangers etc but I'll leave it there.
How exactly would you scale this direct absorption? Glass tubes? Under pressure? Oops, now we're at the air-receiver dream. Never gonna happen. Also, can you guarantee that particles don't get entrained in the steam flow? I'm not sure Siemens is gonna warrantee that turbine. Sorry to be a pessimist, but it's gonna take a while longer for tech like this to make sense to me.
But it isn't hard to separate a small mass of water with low thermal mass from your "a LOT of water", is it? If your nanoparticle solution boils ten liters of water in the first minute, pour out ten liters of water over your black heat absorber, and it will boil in about a minute, too.
i think the hope would be that you get a thermal mass (see other reply) that is effectively variable.
with low amounts of incident energy (or when just starting) a large amount of water will heat slowly and you will get no significant steam pressure until the entire mass of liquid is boiling. but with this technology, you will get some steam almost immediately, from the water around the particles, even though the vast majority of the water remains cool. so you have a system with less lag, which is going to improve control / response.
what is not clear from the article, though, is whether this will still work well when there is a large flux of energy. hopefully both cases (traditional and particles) work equally well. in which case particles are a net win. but it may be that particles introduce new problems with "high input".
[the hope is that you get this flexibility "for free" (no need for "tubes") and yes, it works because the particles are effectively black. i have no idea how it would help remove the need for heat exchangers, though (unless they are externally powered - heat exchangers pre-warm water, which is not necessary with particles, but still makes sense if you are using waste heat, as it reduces losses and so increases efficiency).
the press release talks about making solar power more useful for small scale users in developing countries. my guess is that this helps there because you can get better efficiency when not operating at peak power, so "amateur" solar power is more efficient. the argument would be that at low power you get some stream with particles. without particles, in theory, you should also get some steam if you wait long enough (for things to heat up), but in practice, thermal losses might mean that you never do heat up enough for things to work (the heated water cooling as quickly as it is warmed).]
The technology is interesting, but the title is misleading at best. The water is still boiling, but only a small fraction of the volume needs to be at the boiling point. The tidbit about "cheap and abundant source of steam" is totally uncalled for. Unless you're changing the heat of vaporization of water, you will always get the same amount of steam for the same amount of energy input.
This lead me to an interesting Google search around engine efficiency. I always knew that engines are imperfect engine transfer devices, but I didn't realize how much is lost.
Seems like in most scenarios you're getting at best 40% energy efficiency in gasoline engines and somewhere between 17% to 40% in steam engines.
Even at 17% efficiency using the sun to generate steam power seems to hold lots of potential. The trick will be to get it working at scale and able to produce a similar level of energy with the same or lower cost as existing technologies. May be a while yet, but it's an exciting time to teach your kids science as this is the kind of stuff that they'll probably see in mass later in life.
This is exactly how large scale solar thermal power stations work.
The most common ones use thousands of mirrors around a central tower. The sun bounces off the mirrors and focuses at the top of the tower where there is a tank of water. The water is heated, boils, turns to steam, which turns a steam turbine.
The big win seems to be from eliminating much of the heat dissipation that would otherwise normally occur if, e.g., you tried to use sunlight to boil water when nanoparticles aren't involved.
15 comments
[ 3.2 ms ] story [ 30.9 ms ] threadCan the same idea be applied to improve water's efficiency to exchange heat, to make it cool easier? Then you can slap a turbine and have the perfect steam generator.
I work in the solar thermal industry - my company (http://www.sunapse.co) builds software for solar thermal power plants. I can say with some authority that this is legit and VERY promising tech.
the way I read this is that they put black particles that adsorb heat better in the water. That makes this produce some steam fast. I do not see how this would produce more steam than, say, a thin layer of water on top of a thin black-painted sheet that is well-insulated from below (sun heats black sheet; sheet heats water).
How is producing some steam rapidly an improvement?
So, them being 'black' isn't really the point. The point is the potential to get steam from water at lower temperatures, in less time.
If you are dealing with A LOT of water (if you were to scale this to power-plant scale), you are dealing with large 'thermal mass'. This means you need a lot of heat over time to raise all the water to a high enough temperature to create electricity.
If you run a power plant, you want flexibility. You want to switch on your power plant fast, and then shut it down when you want, without cost. This lets you speculate on the electricity market, and be more available if there is a sudden spike in electricity demand. If you're dealing with large thermal mass, you don't have this flexibility.
Also lots of advantages of lower cost - not needing heat exchangers etc but I'll leave it there.
with low amounts of incident energy (or when just starting) a large amount of water will heat slowly and you will get no significant steam pressure until the entire mass of liquid is boiling. but with this technology, you will get some steam almost immediately, from the water around the particles, even though the vast majority of the water remains cool. so you have a system with less lag, which is going to improve control / response.
what is not clear from the article, though, is whether this will still work well when there is a large flux of energy. hopefully both cases (traditional and particles) work equally well. in which case particles are a net win. but it may be that particles introduce new problems with "high input".
[the hope is that you get this flexibility "for free" (no need for "tubes") and yes, it works because the particles are effectively black. i have no idea how it would help remove the need for heat exchangers, though (unless they are externally powered - heat exchangers pre-warm water, which is not necessary with particles, but still makes sense if you are using waste heat, as it reduces losses and so increases efficiency).
the press release talks about making solar power more useful for small scale users in developing countries. my guess is that this helps there because you can get better efficiency when not operating at peak power, so "amateur" solar power is more efficient. the argument would be that at low power you get some stream with particles. without particles, in theory, you should also get some steam if you wait long enough (for things to heat up), but in practice, thermal losses might mean that you never do heat up enough for things to work (the heated water cooling as quickly as it is warmed).]
Seems like in most scenarios you're getting at best 40% energy efficiency in gasoline engines and somewhere between 17% to 40% in steam engines.
Even at 17% efficiency using the sun to generate steam power seems to hold lots of potential. The trick will be to get it working at scale and able to produce a similar level of energy with the same or lower cost as existing technologies. May be a while yet, but it's an exciting time to teach your kids science as this is the kind of stuff that they'll probably see in mass later in life.
Source: http://en.wikipedia.org/wiki/Engine_efficiency
The most common ones use thousands of mirrors around a central tower. The sun bounces off the mirrors and focuses at the top of the tower where there is a tank of water. The water is heated, boils, turns to steam, which turns a steam turbine.
Look up BrightSource Ivanpah