Small Scale Parabolic Trough

It is the way forward for solar power.

It makes photo voltaic cells seem very outdated.

Good luck I hope you succeed.

Good luck with your project, please register on CR4 and keep us informed.

Perhaps check out the work of Roland Winston before you build. He designed and patented a w curve trough that does not have the super duper concentration of a parabolic trough but which does not need seasonal adjustment. His patent lapsed and the design is freely available now. Winston is still working in concentrating non imaging optics. He has been a trailblazer.

Brian

First of all, and not to be nit-picking, the units "kw/hr" are not correct. Kw is a unit of power, and the appropriate unit for energy would be kilowatt-hours, or the integral of power produced (or consumed) over time.

Now, the amount of power available from sunlight is heavily dependent on the solar insolation, which is measured in Watts per meter squared. Average is 250 Watts per square meter. To capture 50,000 watts (50 kw) peak, one needs an area of 200 square meters. If you live near the equator, you might get peak energy for 4 to 6 hours per day- the further away from the equator, the less you will get, but you will have longer days during the summer. If you include sun-tracking capabilities, you can increase this, but sun-tracking uses energy, so reduces your efficiency. There are many sites on the Internet that can give you good ball-park numbers for the solar insolation in your geographic region.

You are going to lose some energy to the inefficiencies of your heat conversion. You will be heating a liquid to the point of phase change, to drive your turbines. The turbines themselves will result in efficiency losses as well. A good rule of thumb (but in no way an absolute value) is that you are doing really good if you can capture 30% of the available energy. Which means your collector now has to be about 3 times as large as the theoretical unit based on the insolation calculations discussed in paragraph 2 above.

These are the basic starting points for designing your system. First, determine how much solar power is reasonably available in your region, and this will determine the size required for your trough, and whether you actually have enough room for this system. Once this is determined, there are many of us on the forum that can help you with the thermodynamic calculations for determining how much you can reasonably expect to extract, and offer suggestions for ways to improve efficiency.

Perhaps I am nit-picking, too, but sun-tracking should increase the overall efficiency of the system unless it requires a whole lot of power (I think what you mean is that you will not hit quite as high a peak efficiency when the sun is actually in the right position).

i was thinking more along the lines of power consumption required for tracking- especially if one is looking at a sizable system that needs rotating about...I am not sure, but I suspect that with a parabolic mirror, one may not gain enough with tracking to make it worth while...

I would look at the solar power projects in Israel they are of this design and they are so much better than PV cells.....stars & earth difference.

It is the best technology I can find for solar power and there is less electronics to go wrong.

I hope the question asker achieves his goal.

There are actually a number of projects that have been around much longer than the Israeli projects, which might have more historical performance data. I know of one such large installation that has been operating since at least the 1980's located in the desert north of San Bernardino, California, in the USA. Unfortunately, I do not know the name of the installation, but I used to drive by it on my way from San Bernardino to China Lake. I believe it is near one of the prisons. It was a large (and I mean LARGE) array of parabolic reflectors installed on relatively flat land...

Cwarner,

I dont remember the original name, but after it went bankrupt from overpriced mirrors (cause it was federally subsidized and the subsidy ran out) it was bought by Southern Calif. Edison and as far as I know has paid for itself and become profitable. Its called Kramer Junction Solar.

I once applied there for a job,

THIN FILM PV RULES!

Spacecannon

THIN FILM PV RULES!

They are heavy large and expensive if the cost were to come down to 10-20% of present price then I might agree...then a normal house holder could afford one or three to put on there roof and if you live in an apartment then wind power is the way forward.

Portu-gal,

Dude,

you have never lived under a wind turbine have you.

Thin-film are the cheapest PV out there, Im paying under $1.5/watt and there are several companies that claim under $1.00/watt (First Solar, and 2 in asia), but they wont sell to me. (US Dollars)

THIN-FILM RULES!

AND AIRBORNE WIND TURBNES BEAT GROUND BASED ANY DAY!

Spacecannon

Regarding the Southern California solar farms that spacecannon and I have been discussing, (and thanks to spacecannon's better memory), we have some real figures for actual operating solar thermal facilities:

Better information found on SEGS web site, Nextera Energy Resources. The Daggett facilities are owned and operated by Cogentrix, while Nextera operates the other 7 faciiities. They are apparently operating at about 21% efficiency (be careful here- the definition of efficiency may be a bit misleading. In this case, they appear to be delivering 21% of the available capacity to customers). The nine plants require about 0.66 hectares per MW, which is a lot less than suggested by some other studies I have encountered, but this area has very high solar insolation (310 W/m²), and Kramer Junction claims 340 days of sunshine per year...

All in all, this seems better performance than the naysayers claim, but not quite up to the claims of the proponents...

Cwarner,

have you tried NREL and NASA,

I've come across interesting info on this subject, I think it was there, but it was a while back.

I still live out by Dagget, and the thing that I have learned about steam driven systems from concentrated sunlight is they are very expensive with a lot of moving parts that break down, the Tesla turbine is supposed to be simple and efficient but I dont see any commercial use of it so there must be a reason.

Its my experience that big money goes with what works, on the other hand they are trying a sterling engine design out here that isnt working.

If using a parabolic trough why not go with CPV. I hear it is the new big oportunity.

Spacecannon

CPV- Communist Party of Vietnam? Oh- concentrated photovoltaics...

Actually, I am not all that convinced that any solar power system is going to be practical in the long term (the energy density just isn't there), but I keep looking at every option, hoping to someday change my own opinion. Your concentrated photovoltaics are still tied to the high production costs of the cells- one would hope solar thermal would have some cost advantage, but I don't see that. I have no faith in wind, either, since wind is a derivative of solar. Unfortunately, it is extremely difficult to get real information from these people. My current favorite (after mini nukes) is tidal power...

Cwarner,

GA for the laugh

My favorite is Airborne wind turbines, but Im biased cause i have a patent.

I also like pebble bed reactors.

I would like to know what the originator of this discussion plans to use for a reflective surface.

Spacecannon

Parabola will require sun tracking. On the other hand, an hyperbolic reflector will not need tracking if collection pipe is located at the focus and the assembly is properly oriented.

Milo

Grab a copy of 'Solar Engineering of Thermal Processes', Duffie Beckman, 0-471-51056-4

Was a great text for an upper division ME elective at CSUS. Everything you could possibly want to know about the design and optimization of solar thermal processes.