Alt Energy News

[mubs]

Read two interesting articles today. Gave me some warm & fuzzies.

Sunlight to Fuel Hydrogen Future

Solar Tower of Power

 

[jtr1962]

I like the solar tower. Very interesting. If nothing else a 1 km high structure would be very impressive.

As for the other thing, I still don't get what the point of the so-called hydrogen economy is. You make hydrogen and then use it to make electricity in fuel cells which are way less efficient than any battery. You need to transport the hydrogen, which takes energy, and store it at 10,000 psi. Why not just use all the power needed to do this directly to charge a battery? To me it all seems like a Rube Goldberg scheme to accomplish essentially the same thing. Maybe I'm missing something here. What exactly is the point of making hydrogen via sunlight as opposed to simply using solar cells to generate electricity directly? Electricity is immediately useable in its raw form, a tank of hydrogen isn't.

 

[Fushigi]

Hydrogen is probably more profitable for the energy suppliers. That's the only reason I can think of off-hand.

 

[time]

Unfortunately, I'd be confident that the "Solar Tower" is a scam.

The numbers quoted are actually incredibly poor for the collection area. As a rule of thumb, you can count on about 1kW of heat energy being absorbed by every square meter of surface exposed to the sun. That works out to 100,000 Megawatts, yet the output of the Solar Tower is a mere 200 Megawatts. Even allowing for only 8 or so hours of useful sunshine a day, that's an efficiency of just half of one percent.

To put it another way, it needs more than 3/5 of an acre to supply one house with their estimate of 1kW. I'd guess that would double with air conditioning.

There's also the question of air versus steam. If you're going to have such a huge collector, why not just heat water and use the steam to drive turbines? It's hard to see how it could be any less efficient.

 

[sechs]

Why not just use all the power needed to do this directly to charge a battery?

Okkay, let's do that. And then what? We can't all drive around with cords to this mega-battery in the sky!

Nature doesn't have a battery cycle. It has a hydrogen cycle.

 

[sechs]

Unfortunately, I'd be confident that the "Solar Tower" is a scam.

I wouldn't call it a scam, but an investment of questionable return. The efficiency of this system is extremely poor relative to the amount of energy that's hitting it's coverage area -- but that's the case of nearly all solar power systems.

There's also the question of air versus steam. If you're going to have such a huge collector, why not just heat water and use the steam to drive turbines?

The reason why is that they're using the convection currents of the air to power the turbines; steam uses the expansion of the water for power -- which means you have to boil water at the bottom, not just heat it.

Personally, I would have thought that brine would have been a far better medium. There used to be a solar collector system in Arizona that used a tank of heated brine to run its loop.

 

[ddrueding]

Okkay, let's do that. And then what? We can't all drive around with cords to this mega-battery in the sky!

That's the cool thing about batteries, energy can be transferred from one to another with minimal loss, and they are portable. Your above argument implys that you're unaware of such capabilities, just letting you know

Nature doesn't have a battery cycle. It has a hydrogen cycle.

Because nature has organic processes that are able to process hydrogen and use it's energy directly. We don't

You realize you have a very caustic debate style, right?

 

[time]

I wouldn't call it a scam, but an investment of questionable return.

The enterprise appears to exist for the sole purpose of sucking in money from foolish investors - I'd call that a scam.

The efficiency of this system is extremely poor relative to the amount of energy that's hitting it's coverage area -- but that's the case of nearly all solar power systems.

Untrue. Solar panels have an efficency of at least 12%, solar hot water heaters about 40%, and this project claims total conversion efficency in excess of 60%.

steam uses the expansion of the water for power -- which means you have to boil water at the bottom, not just heat it.

Yes, it involves a phase change, but that's not a big deal. Current solar hot water heaters are designed to only minimally heat water - you don't actually want it to boil.

Personally, I would have thought that brine would have been a far better medium.

Brine just has a higher boiling point, so you can exchange more energy without a phase change. Newer solar hot water systems already use the equivalent of radiator coolant, which achieves the same thing only more so.

 

[sechs]

Okkay, let's do that. And then what? We can't all drive around with cords to this mega-battery in the sky!

That's the cool thing about batteries, energy can be transferred from one to another with minimal loss, and they are portable. Your above argument implys that you're unaware of such capabilities, just letting you know

Perhaps you're unaware that batteries spontaneously lose energy. On a regular basis, hydrogen does not disappear from existence.

Batteries take considerable time to charge. Hydrogen simply exists. While it does take time to move hydrogen, on an equivalent basis, this is much faster than charging a battery.

And, if you think about it, you don't have to use hydrogen to make electricity -- you don't have a choice with batteries.

Because nature has organic processes that are able to process hydrogen and use it's energy directly. We don't

Its much easier to work with nature than against it. Check any piece of rusting iron to see.

 

[sechs]

I wouldn't call it a scam, but an investment of questionable return.

The enterprise appears to exist for the sole purpose of sucking in money from foolish investors - I'd call that a scam.

I think that you've confused a great risk with no chance of a payback. Like an Internet startup, the risk is high, but the possible payback is higher.

Untrue. Solar panels have an efficency of at least 12%

Sure, under ideal conditions. What's the efficiency under real conditions? That's the kind of numbers that these folks are quoting. I don't call 12% great efficiency, either way.

steam uses the expansion of the water for power -- which means you have to boil water at the bottom, not just heat it.

Yes, it involves a phase change, but that's not a big deal. Current solar hot water heaters are designed to only minimally heat water - you don't actually want it to boil.

I don't see where you're going here. The phase change takes a great deal of difference in the intensity of energy required to run the system. This can make design far more difficult.

Brine just has a higher boiling point, so you can exchange more energy without a phase change. Newer solar hot water systems already use the equivalent of radiator coolant, which achieves the same thing only more so.

Once again, I'm not clear where you're going. Brine is a better choice because it's much denser, and, therefore, you shouldn't need quite so much of it as air. Hot water systems have nothing to do with it.

 

[Explorer]

Some interesting reading here:

http://www.oilendgame.org/ReadTheBook.html