Solar energy

[Michaelangelica]

to this day nuclear waste is a major issue! We are still not quite sure what to do with it!

No. I was a bit amazed to find it was dumped into the sea as late as the mid 1990s!

But the fossil fuel industry is not blame free either

In Dr.Karl Kruszelnicki's book "Sensational Moments in Science", ABC Press, 2001. He says:-

"In 1982, some 111 (US)nuclear-fired power plants consumed about 540 tonnes of nuclear fuel.

In the same year, coal-fired power plants released over 800 tonnes of uranium." into the atmosphere.

"If a single nuclear-fired plant released 8K of uranium into the bio-sphere. there would be . .an enormous outcry."

He says the nuclear content of coal has not yet reached general public awareness in the same way that the greenhouse effect AIDs, or the ozone hole have.

There are no nuclear regulations about the disposal of coal ash

 

Coal apparently contains a heap of uranium and thorium

Dr Karl concludes that you will get three times more radiation from a coal fired power plant than a nuclear fueled power plant! That's if you include the complete nuclear fuel cycle mining, processing operating, disposal(!?)

If you don't include these your average coal-fired power plant puts out 100 times more radiation than a nuclear-fired plant.

p103-104

[CraigD]

In the 1990s they [the nuclear industry] were dumping waste into the sea.

From following the subject over a few decades, I’ve learned that certain schemes for disposing of nuclear waste at sea are not bad.

 

Simply vitrifying (encasing in glass) high-level waste and dumping it in high-sediment rate areas of the abyssal plains (eg: see in ”High Level Nuclear Waste” (1994)) is potentially a safe practice, which I recall (I’m unable to find an wwwreference) has been widely used by France’s large nuclear power program. A major objection to this approach is that parties with deep-ocean salvage capabilities could recover the waste for use in nuclear weapons.

 

More recently, some folk, ”Permanent RadWaste Solutions”, proposed a variation of seafloor disposal where a sturdier canister is dropped in a subduction zone, so need only survive about 250,000 years until it drops into the mantle, and eventually, perhaps, the core.

[learnin to learn]

More recently, some folk, ”Permanent RadWaste Solutions”, proposed a variation of seafloor disposal where a sturdier canister is dropped in a subduction zone, so need only survive about 250,000 years until it drops into the mantle, and eventually, perhaps, the core.

 

But what would happen if the nuclear waste actually reached the core? would there be no sort of chemical reaction?

[CraigD]

But what would happen if the nuclear waste actually reached the core? would there be no sort of chemical reaction?

Theoretically, who cares? Based on the amount of heat it produces for the amount of time it’s been producing it, the mantle is a radioactive place already, to which adding a little more would have practically no effect. Melted and diffused thought the huge volume of the mantle, wastes of practically any kind deposited in the mantel will, over geological time scales, appear as natural mineral deposits in uplifted rock.

 

Very high-density parts of the waste might sink through the mantle, eventually reaching the core. If so, the core already contains large masses of high-density material, to which the addition of a little more should have little effect.

 

It’s important to keep in perspective that just the thermal energy contained beneath the Earth’s crust is tremendous, dwarfing the total chemical energy output, including fission. It’s hard to imagine any man-made artifact having much effect on it, unless one considers very exotic possibilities, such as man-made black holes.

[Zythryn]

I still like the idea of hurling it into the sun:)

 

Yes, you have to load it in a canister that will survive a vehicle explosion in case of a disaster occuring, but then you are done. Heck, you could use mercury too if you have concerns about the sun.

[CraigD]

I still like the idea of hurling it into the sun:)

 

Yes, you have to load it in a canister that will survive a vehicle explosion in case of a disaster occuring, but then you are done

In addition to the exploding-rocket-of-radioactive-material problem Zythryn mentions, this would be pretty costly. An earth-escape launch costs about $20,000 to $160,000/kg payload, depending on how reliable it is. The DOE says the US has about 55,000,000 kg of nuclear waste. So the current cost of throwing it all in the sun (or anywhere else outside of the Earth) is between $1 and $9 trillion (1,000,000,000,000), for US waste only, not including the mass of any protective containers. That’s a lot of money, somewhere in the vicinity of all the money in the world for a year of 2.

 

Keep in mind also that rocket launches are also environmentally costly, including some disturbing upper-atmosphere effects. At our current modest launch rate, this isn’t significant, but the roughly 1000 times increase a “throw it in the sun” waste disposal scheme implies might damage the environment as or more severely than not dealing with the waste at all.

[Zythryn]

You're absolutely right Craig, just some pie in the sky wishful thinking on my part:)

[Michaelangelica]

An interesting article on "Concentrated Solar Energy"

Back to the magnifing glass??

Here comes the sun | Guardian Weekly | Guardian Unlimited

 

Happy New Year :hyper:

[Michaelangelica]

Technology Review: Silicon and Sun

Silicon and Sun

 

In his lab facing the Pacific Ocean, Daniel Morse is learning new ways to build complex semiconductor devices for cheaper, more efficient solar cells. He has an unlikely teacher: sea sponges.

 

Technology Review: How To Build a Solar Generator

Friday, July 14, 2006

How To Build a Solar Generator

 

Affordable solar power using auto parts could make this electricity source far more available.

[Michaelangelica]

This looked like the most promising "here now" solar panel tecnologies I have ever seen on catalyst on ABC TV

Sliver Cells - March 8

 

While solar power is clean and green, the great drawback for it has always been cost: it is more expensive than coal or gas-generated electricity.

But could that finally be about to change? Researchers at ANU certainly think so.

They’ve invented a new kind of solar cell that will slash the cost of solar panels.

People will chose to put solar on their rooves, they say, because the panels will provide cheaper electricity than power from the grid.

 

The new kind of solar cells are called sliver cells, and the reason they are so cheap to manufacture is because they use 90% less silicon than standard solar panels.

One of Australia’s largest utility companies is so convinced of the technology’s potential they have bought the rights to it and have already built a pilot factory to produce the new solar panels.

 

Read transcriptTranscript

Catalyst: Sliver Cells - ABC TV Science

[IDMclean]

The problem with solar cells is that they are surface area solar accumilators. They grab only a fraction of the availible spectra and only in a square area.

 

I would really like to see the development of cubic solar cell power accumilators. I mean no material absorbs all spectra. So I would think it is possible to layer semi-transparent semi-conductors to maxmize solar radiation exposure and absorption. Kinda like DVD technology for solar cells.

 

I (pipe) dream

[CraigD]

I would really like to see the development of cubic solar cell power accumilators. I mean no material absorbs all spectra. So I would think it is possible to layer semi-transparent semi-conductors to maxmize solar radiation exposure and absorption. Kinda like DVD technology for solar cells.

A problem I can see with that is that while a particular photoelectric material only generates electricity for light of and above a specific frequency (as determined by its photoelectric work function, they typically absorb light of frequencies below that (without generating electricity). So, in a stack of solar cells, only the top one would receive any light.

 

Photonic crystal gratings, which were mentioned earlier in this thread, are promising, as they can convert incoming infrared light into high-frequency light, reclaiming some of the about 35% of sunlight with frequencies below the work function of the best solar cell materials, increasing solar cell efficiency as much as 20%.

 

For large-scale solar power generation, though, efficiency is not necessarily the most important factor. Cheap, low efficiency systems may practically out perform expensive high efficiency ones. Compared to the cost of the systems and their maintenance, size is typically a less significant factor.

[Michaelangelica]

A problem I can see with that is that while a particular photoelectric material only generates electricity for light of and above a specific frequency (as determined by its photoelectric work function, they typically absorb light of frequencies below that (without generating electricity). So, in a stack of solar cells, only the top one would receive any light.

So, in a stack of solar cells, only the top one would receive any light.

Look, I don't understand completely-I have only seen a TV report -but this is exactly what does not happen.

The area that collects light is many, many times that of a normal solar cell.

the silicon now used for only a single solar cell now is sliced into 700-800 pieces.

Effectively turning what was one cell, into 800 solar cells!

 

If you hold them up to the light the sliced cells are almost transparent.

They are also flexible allowing them to be put on office windows say.

The production difficulty is in the fine slicing of the silicon.

But in a 40mil pilot plant they have developed robots to do this in a very sterile environment. No energy company is going to invest 40mil unless they can see some returns.

 

Another advantage they have is, if they’re partially shaded they still produce power. Unlike conventional panels which shut down with even with a little shade covering them.

 

The cost of solar is measured is the number of years of free electricity you need to pay off the installation. Today it’s about 20. With mass-produced sliver cells it could be just 5 to 7 years.

 

Tony Wood: We would expect to see commercial panels of the size that would be used in a domestic situation over the next 12 months or so.

Now initially we’ll be putting them into the market in very carefully selected trials, to make sure the things work properly, that there’s no problems, but in the next few years you’ll certainly see these deployed in Australia and overseas.

 

*******************************

 

I still can't figure why silicon is so expensive.

It is a pretty common substance is it not?

Wiki says:-

On Earth, silicon is the second most abundant element (after oxygen) in the crust, making up 25.7% of the crust by mass.

Is it the fact it has to be so pure that makes it expensive in solar cells?

Does anyone know why wiki says this:-

silicon is less reactive than its chemical analog carbon.

What is its relationship to carbon?

[Michaelangelica]

perhaps this could be married with the sliver cells??

Orbs of Power! Solar Cells Go Spherical!

Filed on Mar 9, 2007 at 2:46 PM PST

By Michael dEstries

 

 

We like it round. If you've been looking for a little variety beyond your average flat solar panel, a Japanese company may have just what you're looking for. A spherical solar cell has been created that is designed to capture light from any direction. The cells optimize the use of reflected and indirect light resulting in an efficiency rating of 20% -- well above most flat photovoltaic technologies.

Orbs of Power! Solar Cells Go Spherical! | Green Options

[silverslith]

The cheapest solar technology to roll out large scale is algaculture. It can produce over 100 ton/ha/a of dry biomass with high starch or oil contents. So its a great CO2 capture technology that can also suck up co2 from powerplants burning coal or better biomass. No problem with enough land for this as the worlds deserts are far larger than the required area and ideal. The US would need only an area 200x200miles to replace its fossil transport fuels. At a setup cost below $5000 per ha

 

Other viable technologies with resources large enough to power the planet are:

-Geothermal dry rock or ocean floor (both virtually unlimited),

-Oceanic currents harvested with large scale turbines (eg/ theres two projects underway here in New Zealand both over 200Mw one in the Kaipara harbour mouth where 15cubic kilometers passes every 6 hours at up to 25kph, and one in cook strait where enough water passes at up to 20kph to supply all the worlds electricity.)A turbine the size of a Windturbine would make ~1000 times the energy.

- Wave energy, though this is a diffuse one.

- tethered large scale lighter than air wind turbines at altitude (i'd love to be unleashed on that design!) .

-Solar mirrors

 

Large scale storage of Solar Wind and Tidal is easy as heat in artificial geothermal reservoirs. Or you can use on demand sources like hydro or natural geothermal to fill the gaps.

 

Nuclear is attractive to big power and money due to weapons and monopolies. The present day reactors are by far the safest it can ever get for fission as any future for nuclear is reliant on u238, th232 and higher actinides with even mass numbers formed in reactors being breed with neutrons to fissile isotopes (like pu239 and u233. Both increasing the radioactivity in a reactor by 50000x one like chernobyl which has killed 0.5-1million). Additionally the reprocessing of fuel would be a burden for 100's of cycles over 100's of years and is well outside our tech capabilities to do at all now, let alone safely (much harder to do safely than use in a reactor "safely"). Furthermore the mining of actinides releases 10x as much radioactivity into the enviroment as is contained in the final fuel produced and therefore has been unleashing a quiet and constant chernobyl that has undoubtably killed more than the Automobile.

Fusion is a long way off and theres plenty of alternatives far cheaper. Most don't get investment from big money because big money likes monopolies that no-one can afford to duplicate and affect their profits. It especially don't like stuff you can do anywhere for little cost:evil: . worst nightmare!

[Michaelangelica]

The cheapest solar technology to roll out large scale is algaculture. It can produce over 100 ton/ha/a of dry biomass with high starch or oil contents.

Fascinating posts (thorium too) thanks.

Algaculture was not on my radar.

there seem to be a number of pilot plants setting up here.

 

I wonder if you could combine it with new pyrolysis technology?

 

Getting water in Oz deserts is difficult

 

Growing microalgae for CO sequestration, wastewater remediation,

fuel and other valuable products

Brian Kirke

Sustainable Energy Centre

University of SA

6 October 2006

Summary. Aquatic microalgae can use sunlight, nutrients in wastewater and CO and waste heat from power station flue gas to produce biomass rapidly and efficiently.

This biomass can be used to produce transport fuels, plastics, fertilizers and feed for livestock and aquaculture. Thus algae offer the possibility of addressing 3 major problems at once:

1. CO2 emissions

2. Nutrient pollution of waterways

3. Depletion of fossil fuels.

Submission - Australia's future oil supply and alternative transport fuels

[silverslith]

I wonder if you could combine it with new pyrolysis technology?

 

Getting water in Oz deserts is difficult

 

The high oil content is usable as diesel (with a little transesterification (add a little alcohol and a catalyst) and the starch easily fermented. Theres none of the difficulties in processing that cellulosic biomass has so Pyrolysis would be overkill. However Pyrolysis products are easily tankered or piped so using them to fuel power stations that are located where algaculture is centred- so to consume the co2- has promise.

 

Water consumption in covered ponds is low enough that most deserts annual rainfall is enough. You don't want to waste your time with open ones because temperature fluctuations are going to kill your high yield algae or at least cut yields to 10%-30% what they could be. Oz has abundant water up north. Piping it to flat low lying desert area a little south would seem pretty simple.