A different way to use solar

[alexander]

Now, we have been talking on and on about making a pv system, but i have found other, interesting ways to use solar, and some interesting projects that may get some of you interested, maybe inspired to build and improve on the concepts.

So, one could utilize a fairly inexpensive solar concentrator, such as this one:
Multifacet parabolic solar concentrator

to power a home-made slotted turbine, concept of which is described here
Slotted Disk Turbine

now, question is, where do we, geeks, start to improve on both of these designs to utilize solar, cheaper and in some ways better then PV...

Enjoy pondering, looking forward to what you guys think.

[Roadam]

Multifaceted concentrators are cheap, but they dont concentrate if there is no direct sunlight onto them.

But I am not sure about that turbine. It may not even be cheaper to produce than normal equivalent. Nor would it be equivalent in efficiency. But I cannot claim that by other than my feeling.

[alexander]

the turbine can be built for under 300 bucks, i dont know about their efficiency.

i figure a sun tracking system will be in order of a 100-150 bucks for the stand for the reflector and all, if you buy commercial that is.

but this is not even about a money issue, its about making an efficient design that will use solar in a different way then pannels, for example, where you need some serious chemistry to produce a pannel, and the smallest of cracks in the pannel may disable the unit, and it may or may not be repairable, simplicity is the goal of a water vapor system... at least till the turbine part, its only a bunch of tubes, water and mirrors (some flow control valves)

The real question is how we can fairly efficiently use solar in a similar system. I know you need direct sunlight for the concentrator, but that's not the fun of this mental project.

[Roadam]

Oh of course, if you dont want to use something as complicated as solar panels!

Well, home made system would probably be unable to sustain high temperatures so I guess that 200 °C is possible. But at that temperature the efficiency is about 16% (endoreversible method, not carnot, it seems it is more close to the real world). But since the turbine would most probably be non ideal, efficiencies may be even smaller.

[alexander]

I have a couple of questions for you (and this is not because i'm stupid, i have answers, but once again, thought provoking )

What is the pressure at 200 degrees going to be, and how do we make our system safe at that pressure?

What is preventing us to go to a higher temperature, aside from obvious dimensions, but we can fairly cheaply increase those, but what else can be holding us back, and going back to the first question, how do we ensure safety?

How do we ensure that this home-made unit maintains a certain level of slight environmental change invariance (small cloud, or what have you)? (like heating up some heat-retaining material instead of straight pipes)

How do we improve the efficiency of the turbine, also would it be more beneficial to go with a different type turbine, or should we go with a piston engine, lets ponder those directions and not rule out a possibility of something else completely... remember, heating up water to make steam may not be the best thing to do, there may be a better way to utilize this heat... there may be a PV cell that can handle those temperatures at a much higher efficiency, or, we could talk about a reflector into a lens, that will split the spectrum onto a set of panels that are optimized to be used in specific wavelengths....

[alexander]

i've just had an idea about doing something with a micro hydro systems actually, you can use a pv unit to power a pump installed in the intake pipe, that will pipe some water to a higher elevation collector, that would change the power output of a small water turbine... without much need for more special pv-centric equipment... dc pump motor, tubing and collector tank, fairly elevated (does not have to be very big), and a drop tube into the turbine... kind of like turbo charging with an electric turbo that runs on solar.

[freeztar]

Originally Posted by alexander

i've just had an idea about doing something with a micro hydro systems actually, you can use a pv unit to power a pump installed in the intake pipe, that will pipe some water to a higher elevation collector, that would change the power output of a small water turbine... without much need for more special pv-centric equipment... dc pump motor, tubing and collector tank, fairly elevated (does not have to be very big), and a drop tube into the turbine... kind of like turbo charging with an electric turbo that runs on solar.

It would be better to use the pv by itself as you would be losing efficiency at the pump and the turbine.

[alexander]

yes it would be more efficient, and i am absolutely recognizing this, its more cost effective to do this though, because if you have a hydro system tied to the grid already adding this would only boost your system's output, you would need to get a totally separate system with pv, and grid tying those is a major pain, also you would need to make at least 120VDC to use any grid tie inverter, thats 240 .55 volt industrial pannels, generally about to 3x3in, to 6x6 (depending on power out, ex 2500ma would ve a 2.9x3.2in, 6000ma would be around 150mm X 150mm), which, as you can imagine, is a fairly large-sized array. The goal was to only put a couple of panels, up to give the station a boost, without starting a solar farm, or dropping 3 grand on a separate system... mind you too, depending on where you are, you may not be able to place a solar array like that, in any place that would give you any decent efficiency... but you may be able to throw a couple of panels up in an opening between the trees or something.

Hey, just a thought, you know.

[Essay]

Originally Posted by alexander

...that will pipe some water to a higher elevation collector, that would change the power....

The two ideas I've mulled over for years are:

#1. Using solar insolation to lift water, just through evaporation at a low level and then condensation at a higher level. Basically it's just a passive way to store mechanical energy. I usually try to think of using found materials to make a solar chute to carry water vapor up to a tank where it should condense and later be used to run a water wheel type generator, on the way back down.
...or to supplement some other system (turbine?) as Alexander mentions.

Though if you had a channel (the solar chute to carry the vapor up) which had different lenses to make the higher levels hotter, it'd transport water uphill much more efficiently (...and with a heating lens on the bottom reservoir, of course). ...and possible to tap some of that rising energy also, maybe to help with condensation....

&

#2. Using the (solar induced) expansion and contraction of large massive objects (houses, bridges, etc.) to translate a small strong movement into a lot of rpm's, or any other large (less strong) mechanical advantage.
That's a very abstract description, so: Does that make sense?

~

[alexander]

#1.
Its a neat idea, there is one problem with it, while you are using a natural way to lift water, due to the properties of this liquid, it is anything but an efficient way to do so. You need to evaporate a lot of water to get a constant flow forming from a condensing water. It seems like a lot of energy wasted just to get the water to a higher elevation... we can run numbers on this, if you disagree, but it seems that a pump, at least for this type of system would be a lot more efficient at getting the water up there...

#2
Interesting concept... lets me ponder on that for a bit