Heat transfer: IBM’s concentrated photovoltaic system can focus 2,300 times the power of the sun onto a one-square-centimeter solar cell without causing heat damage, thanks to an indium-gallium liquid-metal alloy that conducts heat away from the cell.
IBM
Saudi Arabia's newest purification plant will use state-of-the-art solar technology.
Saudi Arabia meets much of its drinking water needs by removing salt and other minerals from seawater. Now the country plans to use one of its most abundant resources to counter its fresh-water shortage: sunshine. Saudi Arabia's national research agency, King Abdulaziz City for Science and Technology (KACST), is building what will be the world's largest solar-powered desalination plant in the city of Al-Khafji.
The plant will use a new kind of concentrated solar photovoltaic (PV) technology and new water-filtration technology, which KACST developed with IBM. When completed at the end of 2012, the plant will produce 30,000 cubic meters of desalinated water per day to meet the needs of 100,000 people.
KACST's main goal is to reduce the cost of desalinating water. Half of the operating cost of a desalination plant currently comes from energy use, and most current plants run on fossil fuels. Depending on the price of fuel, producing a cubic meter now takes between 40 and 90 cents.
Reducing cost isn't the only reason that people have dreamed of coupling renewable energy with desalination for decades, says Lisa Henthorne, a director at the International Desalination Association. "Anything we can do to lower this cost over time or reduce the greenhouse gas emissions associated with that power is a good thing," Henthorne says. "This is truly a demonstration in order to work out the bugs, to see if the technologies can work well together."
While the new concentrated PV technology might generate affordable electricity, solar power still costs more than fossil fuels in many parts of the world. But even with those high costs, using it to power desalination makes sense, Henthorne says. "You're not doing it because it's the cheaper thing to do right now, but it would be the cheapest thing down the road."
Desalination plants typically use distillation. Most upcoming plants, including the one in Al-Khafji, will use a process called reverse osmosis, which forces seawater through a polymer membrane using pressure to filter out salt. Both these methods are energy-intensive. Saudi Arabia, the top desalinated water producer in the world, uses 1.5 million barrels of oil per day at its plants, according to Arab News.
The new plant's concentrated PV and reverse-osmosis systems will use advanced materials developed by IBM for making computer chips.
Oasys Water says it will test complete, large-scale systems using forward osmosis early next year.
Cotton fabric treated with nano inks produces a water filter that's efficient and needs little power to work.
It sounds like a good use of PV solar, and a great way to displace 1.5 million barrels / day of oil.
My question is - what do they do at night - do they just stop producing water (can they), or do they switch to fossil generated electricity?
The way to use renewables is to find intermittent uses for them so you can produce something when the sun shines (or the wind blows).
You can't store electricity easily, but you CAN store fresh water so this seems like a great use for PV (as long as you can tolerate the plant lying idle for 14 hours/day.
Re: What do they do at night ?
After the sun goes down, what you do is largely a financial/environmental decision.
You could shut the plant down. That means that the capital you spent on the plant is only producing revenue for 1/3rd to 1/4rt of the day.
You could switch to fossil fuel power. There's both a financial and an environmental price that you would have to pay. You'd have to build natural gas (?) generation, pay for the fuel, and accept putting more CO2 into the environment.
You could install additional concentrated solar, store the heat produced during the day, and use that stored heat to keep the plant running around the clock.
Re: What do they do at night ?
I wouldn't assume you can simply shut the plant down at night; many industrial facilities cannot be simply turned on/off with a simple switch.
Re: What do they do at night ?
I'd say storing the heat for use at night is the best option if they intend to go 100% solar at the plant. They probably won't be able to run it through the night, but maybe get a few more operational hours.
Re: What do they do at night ?
What they do at night probably would be to switch to other sources of power. Power plants cost money and reduce efficiency when they are cycled up and down.
Since electricity demand is naturally lower at night, the existing electricity generation can be diverted to power these types of facilities.
Solar is naturally a "peak" power source, meaning it is most abundant at the same time that demands for commercial power (i.e. retail stores) and for cooling are greatest.
In my view, the most logical supply combination for solar is with nuclear, ignoring of course obscure technologies such as pumped water power.
Re: What do they do at night ?
Look near the end of the article: they will use reverse osmosis powered by those photovoltaic cells, as opposed to distillation.
The way RO works is to have your salty water at a relatively high pressure, and the pure-water side at lower pressure, to force the H2O through the membrane that excludes the salts. The pressure difference doesn't need to be all that high -- my house's regular pressure at the tap works just fine for my home RO system that resides under my kitchen sink.
So now think: what's an easy way to establish water pressure? Height. You pump the salty water up to a set of water towers, and they will then drain out to feed the RO filters. So you can set the relative sizes of your PV and RO arrays so that your tanks fill up during the day, and drain through the ROs 24/7, getting close to emptying the tanks in the morning, when the pumps start back up again.
Basically, you can use the prefiltered water itself as your overnight energy storage.
Re: What do they do at night ?
Overcoming the osmotic pressure at the quantity of water that they are trying to process takes a lot of energy, more then gravity could provide. 1.5 Million barrels at 1700 kWh per barrel gives us 2.550 TeraWh per day. That's a lot of energy expenditure for some of the worlds most efficient plants.
Re: What do they do at night ?
"Overcoming the osmotic pressure at the quantity of water that they are trying to process takes a lot of energy, more then gravity could provide."
That doesn't make any sense. Gravity is a field, not an energy source. But raising matter within a gravity field can *store* a lot of energy.
To provide the osmotic pressure, you need to generate the pressure from your energy source. You can do that directly with pumps, or by using the pumps to raise the height of the water, letting gravity provide consistent pressure for the trip back down -- which is how most municipal water supplies do it.
Re: What do they do at night ?
the key to solar desalination is the cost, also need simple, the membrane, high temperature etc, is not affordable for solar desalination, we have developed a very simple core to realize the desalination and could work with temperature just above the ambient about 20 C, just a core, a fan and very little thermal energy, the core just plastic, two channels, one condensation and one evaporation, salty water evorating in the evaporation channels, and oure water condensation channels, condesation heat transferring supply energy for water evaporation, and little solar water are only for make up, very simple, very low cost, very little energy.
at light, we combine with solar ponds, as we only need hot salty water with temperature about 20 C higher than ambient, the night ambient temperature is low, so the hot salty water temperature could be low and not heavy insulation for solar ponds is required.
Please visit www.i-isaw.com
yuanyijun
Does anyone know why Ultra-High-Concentrating PV would be particularly useful for desalination?
I don't see an explanation of why UHCPV is useful vs any other PV technology for desalination. For reverse osmosis, is any energy other than electricity required (for mechanical pumps)? Is UHCPV used just because it's fancy research?
With UHCPV there would likely be recoverable waste heat, but would need to be <<60degC. That might be useful in some places, but I can't see how it would apply in desalination. I've heard of a scheme to create concentrated brine by evaporation, then use that to reduce salt in seawater, but PV waste heat wouldn't work better than a pond.
Is there some soft of flash distillation that would work with heat input at 40degC? It seems that reverse osmosis with energy recovery is the most efficient, and that uses pressure not heat.
Is using PV energy to run a desalination plant better than grid power? I would think that it would be useful to turn off a desalination plant during peak electric demand and use the solar collectors for other daytime usage.
I was wondering if water towers (e.g. reservoir on a mountain) could be useful to store water pressure energy, but when I looked at it before it seemed impractical. [The reason is the price of electricity is low at night and high during the day.]
Re: Why Ultra Concentrating PV?
A fair point - why do they go for 2300x concentration and not (say) 400x ?
It is either a sweet spot, or just IBM showing off.
In either case, it is probably good.
As they say, they are trying it to see if it scales up and works in practice.
As Holoman says, they will need to keep the lenses and mirrors clean - the only way to find out if this is realistic is to build it and see.
It is amazing that they burn 1.5 Million barrels of oil per day on desalination - anything that reduces this is going to save a lot of money.
It is a pity they can't use the (highly concentrated) heat energy for further evaporation - maybe this is what they are trying to do?
Re: Why Ultra Concentrating PV?
I'm not sure if it's the case here, but I believe there are some varieties of PV that can get in the range of 40% efficiency -- but these would be pretty expensive. So if you can concentrate the light, you can use a lot less of this expensive silicon for a given collector area. Note that you also have to track the sun to keep your focus point on the chip -- with the side effect of providing an additional boost to the daily electricity output. In the end, you will probably get higher output for a given collector area, possibly at a comparable cost to regular PV. With maturity, it might wind up beating regular PV in terms of cost per cumulative KWh output.
Of course, any concentrated-sunlight technique requires unobstructed views of the sun, so they're only viable in regions with extremely low cloud levels. Saudi Arabia should be excellent for that.
Re: Why Ultra Concentrating PV?
"I was wondering if water towers (e.g. reservoir on a mountain) could be useful to store water pressure energy, but when I looked at it before it seemed impractical. [The reason is the price of electricity is low at night and high during the day.]"
I don't get why that would be the reason. If electricity is cheaper at night and more expensive during the day, then you can fill up your water tanks/reservoir at night and shut off the pumps during the day.
Re: Why Ultra Concentrating PV?
One reason you see such high popularity of Reverse Osmosis based desalination plants is their cost and profit economics.
Reverse Osmosis is expensive maintain. Building a Reverse Osmosis desalination plant means you commit to one technology for the next 20 years and must buy filters from IBM for the next 20 years. They have huge financial incentive to give u the technology or discounts upfront for committing to buy their product for 20 years.
Evaporation based systems or even rainwater collecting systems tend to have a one time cost with little maintenance for the next 20 years. There is less incentive to lobby or give discounts because once the construction is done, maintenance or further profits are minimal.
I have seen in Australia and in many places pay for expensive outrageous prices for Reverse Osmosis plants that make no sense. Per liter of fresh water capacity, they cost the same upfront and 50-100% more per year to maintain.
It is sad that expensive lobbying is able to promote inferior technologies to pretend they are the green solution to a cities fresh water needs.
lens cleaner on hand as the dust and sand
will definitely effect the technology.
Nice dream but doubt it can work over the long term.
Saudi desalination using solar powr
Where does the salt go once it is extracted from the ocean water?
Re: Saudi desalination using solar powr
At a certain point the salty side gets flushed or recirculated back into the oceans. Some systems use a counter circulation to flush the membrane.
Night operations issue:
Could they possibly implement MIT's idea of using sunlight to breakdown a water molecule into oxygen and hydrogen atoms and recombining the two atoms in a fuel cell? Apparently, this method would allow for a carbon free (and cheap) energy or power to be used either during the day or night.
It would be more viable to apply the same principles as those being implemented in solar thermal power plants. Well insulated subterranean stores are filled with molten salt. Roughly speaking, 50% of the produced solar thermal energy is used to melt the salt; the other 50% is used in the evaporation process. During night, the energy stored in the molten salt can be used to keep the process running.
Using hydrogen for storage is generally not very efficient. Electrolysis, at least, has a hard time getting better than 50% efficiency -- and so do fuel cells. So normally you only get 25% of your energy back.
What's the efficiency of this direct sunlight H20 splitting technique?
The article (link: http://web.mit.edu/newsoffice/2008/oxygen-0731.html) doesn't mention much about the efficiency of the process. I am assuming that it is as efficient as electrolysis..which is not much. BUT even if it is not as efficient as other storage techniques, why would the efficiency really matter as long as it's costing less to produce the same amount of energy?
Of course, it becomes increasingly difficult to keep the costs per kwh down as the efficiency drops. Note that fuel cells still are rather expensive. It would probably be hard for such a setup to beat a PV array even if the sunlight --> H2 step were very cheap, unless that step's efficiency were quite high.
Though if long-term storage is a requirement, then it could win against PV etc. once you factor in battery costs. e.g. it could work well for Johnny Depp's island retreat (http://www.ecogeek.org/content/view/1910/83/).
It could also be a big win for any direct uses of hydrogen -- such as an a H2-fueled jet engine.
Wait, I just looked at the article you linked to, and there's nothing about going from sunlight to h2 directly here. It's just electricity to h2. Which means it's purely about storage -- and the article doesn't claim it to offer anything more. Though the article does overhype the necessity of storage.
So it's really very simple -- if this new electrode they've developed gives about the same efficiency as regular electrolysis (I guess it's just that the electrode material is cheaper than the classic platinum type), then the energy stored this way will be 4x the cost per kwh as the electricity coming directly from the PV, end of story.
Again, it can be worth it if storage is a requirement, or if you really just want the h2. But it's a poor choice for reducing carbon emissions if you have grid power available.
Example: say your home PV setup makes h2 for you to use for your overnight needs. This means that your PV array needs enough capacity to satisfy your daytime needs plus 4x your overnight needs. If we assume that power not used from the grid saves a consistent amount of carbon emissions at the power plant, that means that you could save 3x the carbon emissions if you instead put that excess daytime power into the grid. That is, with the daytime excess going to h2, you're saving the carbon from your overnight power usage, but with it going to the grid, you're saving 4 times as much carbon emissions (for your neighbors). Subtract your overnight carbon emissions from that, and that's 3x the carbon savings.
i assume the indium-gallium alloy also serves as the PV junction n'est-ce pas? (the article doesn't specifically say this) if so that's a whole new line of research: superhot PV's and semiconductors, which could open up a new array of materials for PV, and bridge toward heliostat technology (which would involve molten salt energy storage, hot fuel cells to produce hydrogen,etc.)
And wouldn't the most cost effective water technology here involve recycling brown and gray water and adding small amounts of desalinated seawater as needed?
Warming seawater helps reverse osmosis....
So what they should be doing is cooling it with seawater piped through backed side.
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DJTal
154 Comments
Ocean fertilisation.
We could drastically reduce our need for desalinating water just by using less fresh water for growing agricultural crops. Instead of taking water to where the nutrients are, why not take the nutrients to the water? We don't need fresh water in order to produce more food for human beings. We need to restore the populations of fish and other creatures in the oceans. Ocean currents and storms could be used to spread the nutrients around ,so fertilising the ocean could provide big energy savings compared with spreading nutrients on the land.
Reply
dancrissco
54 Comments
Re: Ocean fertilisation.
This sounds like a very interesting concept. Could you point me to any existing research or published work in this area? I would welcome more comments on this concept.
Reply
briang1621
172 Comments
Re: Ocean fertilisation.
Combining Solar with other plants that require large amounts of energy (like desalination plants) is smart! For my solar technology, (Hovering Solar) I have been advocating its placement next to existing power plants, and other factories which require large amounts of steam, simply because it produces vast quantities very cheaply.
You can see a video illustrating what I am talking about on my website.
www.GreenVineSolar.com
Dr. Brian Glassman
Ph.D. in Innovation Management from Purdue University
Reply
flyingmonster
29 Comments
Re: Ocean fertilisation.
We are already fertilizing the oceans on a large scale with farm run off, street and sewer drainage etc. Massive algal blooms in the US Pacific NW are seriously affecting aqua culture and jellyfish blooms are already becoming a worldwide problem as a result. The Crown-of-Thorns Starfish that is destroying the Australian Great Barrier Reef has also been directly linked to farm runoff.
The efficiency of this desalination system could be much higher if the excess heat is used to turn more salt water into steam to run a turbine generating electricity and more fresh water from the steam condensate.
Don Green
Reply
mkogrady
423 Comments
Re: Ocean fertilisation.
Question to any Biologists out there -
Does a Jellyfish have any significant amount of fat that can be converted to a Bio-deisel fuel?
I saw a TV show that focused on the Jellyfish problems plaguing the Japanese Fishing Industry. The jellyfish were huge slow moving critters - easy to catch, and probably easy to process too.
Just asking...
Reply
StupidPeasant
98 Comments
Re: Ocean fertilisation.
Unintended consequences... Don't fertilize the ocean human.
However, Desalination coupled with greatly reduced energy cost (solar, nuclear, wind, whatever) could green and feed the world, free the wild rivers and clean the pollution from the waters. Pollutants could be dried,cubed and stored. Salt and unused minerals could be returned to the sea. Cheep energy could pump the water to the wastelands of Earth and make it wonderful. Clean water and cheep energy makes many great things possible. Tie all that to the coming technology singularity and we have a very groovy world ahead.
Reply
SparkyVA
4 Comments
Re: Ocean fertilisation.
The earth's way of fertilizing the oceans is with dirt. Where the prevailing winds blow soil into the oceans is where the large fisheries are: Great Banks, off of Chile, etc. Chlorophyll needs some trace amounts of minerals to flourish, and the soil provides that. From chlorophyll, you just climb the food chain to your restaurant plate of fish.
Reply