Solar concentrator to make power and water

The efficiency of the solar concentrator can be designed to work best for a single function.

In the case of the installation you refer to (wherever it is actually installed), the chosen useful output is electric power.

If the solar concentrator was also going to be used to desalinate seawater, the efficiency of electric power generation would fall, in proportion to the extra work being done.

I trust that answers your question

seems to me if you did the electricity first their may still be enough energy left after the turbine that you could AtLeast pre heat the salt water via water to water heat exchangers or whatever medium they use in the heat collector their by cutting the use of fossil fuels for the desalinization part of the operation also could you just add a second array to finish the salt removal or would it be more efficient well it just seems to me that the additional product of fresh water would make it worth while to super size the array or build another side by side with the power plant or even add a third array to pre heat the lower temp steam before reheating for more power which would be worth more on the market the water or the electric may be if we could get the engineers and the bean counters to work out the numbers . and check out the efficiencies because solar is free minus the cost of the facility.

co gen

(Just a suggestion, your Posts would be easier to read if broken up into sentences, and spaced)

You say "and check out the efficiencies because solar is free minus the cost of the facility."

Solar is not actually free, even after the Capital Costs of the Installation are paid for.

There are running costs, depreciation, insurance,loss of interest on Capital, Interest on borrowed Capital, and constant continuing costs.

In any energy conversion, it is not possible to get something for nothing, and all energy eventually is lost in the form of heat, which tries to raise the total temperature of the universe.

Thus any extra extraction of energy, as per your suggestion, lowers the efficiency of the primary chosen output: Electricity.

In other words, you could desalinate the seawater, but get less electrical generation than is desired at the installation.

Fresh water, to be useful, also requires an infrastructure to move it where it is needed.

This can be via canals, pipelines, aqueducts, tankers, or freezing into icebergs which need to be towed and thawed - all of these have losses due to friction (which generates heat)

So from an Engineering and Physics viewpoint, the desalination as an additional facility is a costly exercise.

all those costs also apply to fossil fueled plants right? add 100$$ a barrel it seems it would be a bargain?

For the United States, if around 100 square miles of desert was covered with 80% efficiency convertors of sunshine to electricity, that would run all the United States, plus much of Canada and Alaska with Electricity.

What is really needed is to get more efficient solar cells, plus transmission and in-use efficiencies improved, and the energy troubles of much of the world are over.

Mind you, that system is rather useless on a rainy day, or at night-time.

You ignore the invironmental impact of a large solar installation. What grows under a collector array? Putting collectors on roofs is one thing; spreading them across dessert landscape is a totally different proposition. There is an installation I once saw in Southern California, between Ontario and China Lake, of a large solar farm. Barren. The dessert around the farm is not barren...

"What grows under a collector array?"

- mushrooms?

http://blog.scifi.com/tech/archives/2007/05/04/solar_power_pla.html

guess it not a new idea after all.

Guys,

As a proponent of Desalination plants, I have the following observation.

One interesting down side to desalination is that the external environment; that is the source of the sea water, becomes progressivley more saline.

Even the oceans are finite so this has to be factored into our calculations.

If we need water, and we do, we need to be careful how we obtain it.

Pulling water from wet mountainous areas might be better. But that has other costs and other environmental effects; again this is a finite resource.

Perhaps for desalination we need to tow the odd iceberg over to the source??

I have not seen any calculations on this effect, but feel that we need to understand the implications of any action on our part to avoid yet another global environmental problem.

As I said at he beginning I am a firm believer in desalination and believe that we should be employing it in a number of areas around the world where drought is a significant problem.

I believe that usage of the desalinated water should be limited in the first place to drinking water; agriculture and industry might have to think hard about how they minimise their water usage first.

G'day

Sleepy

My experience with desalinization is that it is expensive from both the energy consumption perspective and the maintenance perspective. You are right that such processes should be used for drinking only. Agricultural/industrial uses are best supplied by recycled water, and the technology already exists to accomplish this (although not the infrastructure to make it practical in most locales).

"Even the oceans are finite so this has to be factored into our calculations."

Isn't rain just solar powered desalinization?

In answer to your above question, Steve S, Yes....

The solar concentrator produces steam from water and it is the steam that runs the turbines which produce electricity. If salt water is used, the minerals in it are not separated but put into suspension in the steam. When those minerals run through the turbines, especially in the high temperature sections, they will deposit on critical parts and cause no end of corrosion problems and maintenance. Also, the residual steam after its runs through the turbine condenses back to water and is re-cycled to be used again in the concentrator. One of the worst problems of the desalination process is dealing with the corrosive results from the minerals.

The main problem with your installation is that it is electro-mechanical and thus "old technology".

There is always going to be a problem using a fluid medium to transfer energy.

In all turbine situations, there are several problems:

1. Chemical corrosion - even if distilled water is used.
2. Erosive corrosion - Caused by cavitation of the fluid.
3. Seals and bearings problems.
4. Frictional losses.
5. Mechanical wear on all parts.

I have seen stainless steel Francis type turbine runners looking like sponges on the blade edges, after less than a year in operation, using fresh water. The damage was caused by that old enemy of the screw propeller: Cavitation.

Although Solar cells are not yet really efficient = 40+ percent at present see:

http://www.energy.gov/news/4503.htm

So, a 40+ percent efficiency of the actual solar cells is good, but because of other losses in actually getting the electric power to the user, that nett efficiency drops to around 12 percent. (Transformer losses, Copper losses, reactive line losses, Power Factor correction requirements, and so on)

Yes, I am aware that a 100 square mile solar cell installation far out in the desert would not be a pretty sight/site.

This gets us back for better efficiency to solar cells on each house/property roof, all connected to the electricity grid, with meters reading in/out, but does not get around the zero generation during the hours of darkness.

So........what is needed - all must be easy to obtain, and very cheap:

• Solar cells with efficiency of 85 percent plus.
• A method of easily storing electricity during darkness or low-light periods.
• Converters to raise the voltage to useful levels for domestic/commercial/industrial users, also to transmit to other areas.
• The efficiencies of all the losses added together, not to exceed 30 percent.
  

Now for the thinking caps, c'mon folks ........

Response to Sparkstation and cjwarner

Sparkstation,

One,

I am not competent to join a discussion on Turbines but simple reading of the problems associated lead me to believe that this is a tough nut – although being worked on by many at any one time – think of all the hydro-electric schemes for example – get Rolls Royce on the job!

Regarding Solar Cell electrical generation.

Improvements in Solar cell efficiency are absolutely necessary to make them a worth while contributor. Currently, as far as I can see the majority of the R&D is being spent on improvements in the efficiency of the current solar "diodes" silicon etc.

Thanks for the update on the Boeing/Spectrolab work; this leaves the impression that we will probably be working hard for every tenth of a percentage point in the future unless we consider a jump in Technology.

We probably need a major rethink which might involve plant technology. Plants have spent how many millions or billions of years improving this process and we ought to be able eventually to capture the chemistry and replicate it in a suitable manner. This is probably a long term issue and we will still need to work with the best of the existing technologies.

Can anyone on this forum please break down the causes of the inefficiency of the current diodes. Then perhaps with collective minds we might just be able to winnow away at one or two of them - if we achieved a 1-2% improvement then that ought to be worth having, especially if others are doing the same and we were able to tandem the results. Get the whole world involved.

How is the efficiency of a solar array or diode defined. Is it relevant to an array of a plant cell based system? Is anyone aware of any work being done in this area – I don't suppose it has been defined as a too difficult problem?

Moving on.

You talk, sparkstation of losses in the distribution which reduce 40% efficiencies to 12%; a frightening set of losses. Can we please enumerate and quantify these so that we can all look at the overall problem.

Can anyone produce a diagram with quantified losses.

I presume that the losses in distribution from a power plant to a large array of homes is a different matter to a solar array driving some single large plant such as a desalination plant. Perhaps the desalination (or other large) plant wins out through less wasted power? And the houses can all have their own individual arrays?

I have seen some non related discussion about the power distribution problem issue being different between lots of small scale generators as opposed to the old style large generators coupled together on a grid, I have yet to follow this up.

Finally, forgive me if I have strayed from any "proper format" or whatever - I am new to this.

Thanks

Sleepy

Further response to Sparkstation.,

I forgot to add a comment on Storage.

I had believed that major storage in West Coast USA was heading towards Vanadium batteries - I believe that Google search will find this without a problem.

This assumes that a Vanadium battery can be used for storage - it is NOT the sort of thing that we would put in our homes but useful and interesting.

Sleepy

Based on my very limited experience with solar, the main problem is not the efficiency of the panels themselves, but rather what I refer to "temporal distribution", i.e., having power available when it is needed. Storage technology is critical. I have had very, very good results with solar water heaters (i.e., hot water when I want to shower or wash dishes), and good results with small solar electric installations in remote locations where there are limited alternatives (solar far outperforming wind, being much more reliable/predictable)- limited by storage battery technology. I am also very encouraged with regards to wave/tidal energy options, except that these are generally high-dollar options that are not available to the small operator, and generally involves a large distribution configuration.

Perhaps we should be looking at cultural modification? Why is it necessary to light up Las Vegas every night like daylight? Limiting certain high-energy activities to daylight hours could significantly reduce the storage requirements...

Both with energy and water, the long term solution is going to require a modification of our consumption patterns (i.e., Australia and other countries mandating the phasing out of the incadescent light bulb, perhaps mandating a transition to LCD or plazma screens to replace traditional TV tubes), and pricing water to reflect the actual cost of production...

the original post was to explore concentration of sun light on a surface to generate heat that could be used to produce power and water by some method other than photovoltaic means that area seems to be well under development with new flexible screen printing method the company is already in production. what material in a Tesla turbine when used for a runner would be easily cleanable and non corrodible and temp resistant as far as making steam to run the turbine and further removal of salt after the turbine has taken its energy.

dear sir, plasma & lcd tv,s use approx 3 times as much power as crt- I personally watch a 1990 Philips 26" tv by choice- as repairer of tv,s etc I wouldn't watch much of late stuff- the future of tv may be compact crt & possibly oled displays.

lcd and plasma t.v both use more energy than tube technology. they are a bad thing as far as energy use, but good for hd pictures. I havent checked into power use but oled organic led technology is on its way (previously used in car stereos as a display technology.