There Must be Something Simple I'm Missing Here...

[Luminal]

After reading up on solar energy extensively, it seems the major drawback is of course that is absorbs less than 20% of the sun's rays as energy, and the rest becomes heat.

 

Why do we not see commonly (if at all?) simple mirrors or magification lenses placed on top of bodies of water (such as the ocean) and a chamber which traps all the heat? As the water moved into the chamber, the focused thermal energy would vaporize the water.

 

To increase its efficieny further, the outside of the "chamber" would have a small outer chamber which would absorb radiating heat from inside and warm the water before it ever entered the middle, thus reducing the amount of energy inside needed to vaporize it. A primer layer, so to speak.

 

Keep adding outer layers until almost no radiating heat is lost, and you have over 90% efficiency.

 

This is so simple a second grader could design it. Why do we never see such devices implemented? Something deceptively simple I'm overlooking?

[foodchain]

After reading up on solar energy extensively, it seems the major drawback is of course that is absorbs less than 20% of the sun's rays as energy, and the rest becomes heat.

 

Why do we not see commonly (if at all?) simple mirrors or magification lenses placed on top of bodies of water (such as the ocean) and a chamber which traps all the heat? As the water moved into the chamber, the focused thermal energy would vaporize the water.

 

To increase its efficieny further, the outside of the "chamber" would have a small outer chamber which would absorb radiating heat from inside and warm the water before it ever entered the middle, thus reducing the amount of energy inside needed to vaporize it. A primer layer, so to speak.

 

Keep adding outer layers until almost no radiating heat is lost, and you have over 90% efficiency.

 

This is so simple a second grader could design it. Why do we never see such devices implemented? Something deceptively simple I'm overlooking?

 

 

What about water vapor concentration increasing in the atmosphere. I mean if that got large scale enough in use as to support populations such as those in Europe and China alone I think would be enough to have a massive increase in global cloud cover. As the earth being an interacting system who knows what that could lead to in time, I would go as far as to say it could trigger an earthquake.

 

So something to trap the water vapor is an obvious requirement.

 

Do you have any ideas on this?

[swansont]

After reading up on solar energy extensively, it seems the major drawback is of course that is absorbs less than 20% of the sun's rays as energy, and the rest becomes heat.

 

Why do we not see commonly (if at all?) simple mirrors or magification lenses placed on top of bodies of water (such as the ocean) and a chamber which traps all the heat? As the water moved into the chamber, the focused thermal energy would vaporize the water.

 

To increase its efficieny further, the outside of the "chamber" would have a small outer chamber which would absorb radiating heat from inside and warm the water before it ever entered the middle, thus reducing the amount of energy inside needed to vaporize it. A primer layer, so to speak.

 

Keep adding outer layers until almost no radiating heat is lost, and you have over 90% efficiency.

 

This is so simple a second grader could design it. Why do we never see such devices implemented? Something deceptively simple I'm overlooking?

 

Solar thermal collectors exist, but they take up a bit of space.

http://www.npr.org/templates/story/story.php?storyId=5733830

http://en.wikipedia.org/wiki/Solar_thermal_energy

 

I'm not sure I understand your efficiency improvement geometry. Layers would interfere with the solar transfer, and any layer will radiate energy out as much as it radiates in.

[iNow]

The bigger issue in effieciency is bandgaps. You can add different layers of different materials to absorb different wavelengths of light, but ultimately it's the bandgaps themselves which limit efficiency on a solar cell.

 

Here's an interesting article that puts it in terms which are easy to digest:

 

http://www.lbl.gov/Science-Articles/Archive/MSD-perfect-solar-cell.html

 

 

...and also here:

 

http://www.lbl.gov/msd/PIs/Walukiewicz/02/02_8_Full_Solar_Spectrum.html

[Luminal]

Solar thermal collectors exist, but they take up a bit of space.

http://www.npr.org/templates/story/story.php?storyId=5733830

http://en.wikipedia.org/wiki/Solar_thermal_energy

 

I'm not sure I understand your efficiency improvement geometry. Layers would interfere with the solar transfer, and any layer will radiate energy out as much as it radiates in.

 

Yes, I didn't explain it correctly.

 

Basically, a large mirror or magnification lense would focus sunlight onto an area several meters below sea level which is sectioned off from the ocean. This area would be composed of the best material to absorb light and reflect as little as possible; there are good candidates for the material but that's not relevant to the discussion.

 

This chamber several meters below sea level would become extremely hot (based on how much magnification is taking place).

 

The water would enter the chamber via a pipe wound around the chamber, thus heating from the radiating warmth and then truly vaporizing as soon as it contacted the surface, as would drops of water upon an oventop would vaporize on contact.

 

In short, the water's pathway into the chamber would encircle the structure (perhaps in tight corckscrews, but the details can come later). The radiating heat would heat the water as it is flooding into the chamber.

 

Imagine it like this: a cubic meter of water comes through a pipe (being heated itself by the radiation) each second from the ocean and sloshes across the surface of the superheated material. The steam would traverse back up an adjacent or inner pipe (thus another way to re-use the lost heat) and turn some turbines. Of course, as it condensed and fell back down, it would turn more turbines.

 

I hope that's detailed enough.

[Fred56]

There´s solar towers. They built one somewhere in the Middle East I think. There are plans to build a big prototype in Australia. But they are only about 3% overall efficient and to get a significant output you need a pretty big area to collect solar energy. And an efficient turbine to harness the airflow...

[Luminal]

I just re-read your responses, and realized you thought I was talking about solar panels.

 

I only mentioned them to show how they are inefficient and an entirely different design could be used using magnification, bodies of water, and steam power (as in coal plants) that would lose very little energy in heat by re-using the heat multiple times.

[swansont]

Doing this in the ocean raises the level of difficulty quite a bit, and below sea level restricts how much sunlight you can collect.

[Luminal]

The only reason I mentioned the ocean is due to uses of distilling the water as it vaporized and providing fresh water from the process.

 

And it wouldn't restrict how much sunlight you could collect, because that would all be done above sea level and focused (through, as I mentioned, lenses or mirrors) into the below-the-surface chamber.

 

The reason it would be below the surface is obviously so that water would naturally fall into place at the required rate rather than needing to be pumped and wasting energy.

[Melvin]

I've heard that there is a solar plant in Nevada (US) that uses hundreds of mirrors to focus sunlight on a tower full of salt. The salt melts and absorbs heat, which is passed through water to vaporize it. The steam powers a generator, which supplies power for 10,000 homes.

[swansont]

I've heard that there is a solar plant in Nevada (US) that uses hundreds of mirrors to focus sunlight on a tower full of salt. The salt melts and absorbs heat, which is passed through water to vaporize it. The steam powers a generator, which supplies power for 10,000 homes.

 

Gee, I wish I'd linked to that

 

The only reason I mentioned the ocean is due to uses of distilling the water as it vaporized and providing fresh water from the process.

 

And it wouldn't restrict how much sunlight you could collect, because that would all be done above sea level and focused (through, as I mentioned, lenses or mirrors) into the below-the-surface chamber.

 

The reason it would be below the surface is obviously so that water would naturally fall into place at the required rate rather than needing to be pumped and wasting energy.

 

You do restrict the light, because the mirrors have to be at the edge of the chamber in order to shine down into it. If they were further away, the lower ones would be blocked. This limits the collection area.

 

You might save some energy this way, but in the other systems, I think re-using the water helps the efficiency. But the main problem is that salt is nasty, chemically, and you have to deal with that. You get fresh water, but you are likely going to limit your power generation. So it depends on what the goal is.

[Melvin]

I can't remember where I heard about it. I think it was on a TV show or something.

[iNow]

I've heard that there is a solar plant in Nevada (US) that uses hundreds of mirrors to focus sunlight on a tower full of salt. The salt melts and absorbs heat, which is passed through water to vaporize it. The steam powers a generator, which supplies power for 10,000 homes.

 

This?

 

http://www.nevadapower.com/company/renewables/solar.cfm

 

 

http://www.nevadarenewables.org/?section=solar

A power tower system uses a large field of mirrors to concentrate sunlight onto the top of a tower, where a receiver sits. This heats molten salt flowing through the receiver. Then, the salt's heat is used to generate electricity through a conventional steam generator. Molten salt retains heat efficiently, so it can be stored for days before being converted into electricity. That means electricity can be produced on cloudy days or even several hours after sunset.

[swansont]

I can't remember where I heard about it. I think it was on a TV show or something.

 

I was being sarcastic (hence the wink); I linked to an article on Nevada Solar One in post #3.