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 :confused: )

 

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]

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]

...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?

 

~ :doh:

[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

[CraigD]

No discussion of solar mechanical power generators would be complete without a mention of solar updraft towers. (AKA solar chimneys)

 

The idea appears to appear around 1903 (yes, people were interested in generating electricity even then :doh:), with the first large-scale prototype (the linked wikipedia article calls it “small scale”, but at 195 m tall, I think such a description is a bit ackward) being built in 1982 in Manzanares, Spain. There was lots of media and enthusiast interest in them ca. 2001, when an Australian enterprise announced the intentions to build several throughout that continent, hinting at the possibility of massive government support, but little information has been forthcoming on that, and the company in question has gained a bit of disrepute as a result.

 

An enticing feature of SUTs is that they can produce power 24 hours a day, by storing solar power-generated hot air during the day, and using it to continue powering turbogenerators during the night.

 

Drawbacks include that they need to be huge – some proposals have the chimney height around 750 m, (vs. for comparison the highest radio mast in the world’s 646 m) and a low-height surface area of 350 hectares (3500000 m^2, or a square about 2.55 km long on each side, vs. for comparison… well, that’s really big, over 3 times the size of the country of Monaco, or about the size of a city-population-density area of 20000 people) – and, like photovoltaic panels, must be kept clean and transparent, a surprisingly difficult engineering challenge.

 

Hypographer Kayra has and continues to post a good bit about his personal project to make SUTs out of lightweight materials, including lighter-than-air lifting parts. Prototype and most proposed SUTs are made out of reinforced concrete and glass.

[Essay]

#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...

 

 

No, I wasn't shooting for a constant flow of condensed water. It could take all day to evaporate say 10 gallons, but it wouldn't be until night when all the fluid was collected up in (almost as high as you want) some reservoir where you would access a flow to run (perhaps a tall series of) small waterwheels. But it'd only run for at best an hour before running out of fluid. It'd just be a way of maybe supplementing some charge to a battery at night; but it's totally passive. The whole point is to avoid electrically pumping the water.

 

With a sealed system running in the day, and with a cooler dried-air return feeding into the hot fluid reservoir (coming from the collection/condensation tank), it could generate a fairly high airflow rate, just from buoyancy heating. This would really enhance the evaporation rate.

 

Ha, I see this is similar to the solar tower idea, just trying to add in the water transport, along with the updraft.

 

~ :phones:

[freeztar]

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.

 

I see, thanks for clarifying.

[Roadam]

I got interesting idea for solar concentrators. Basically you concentrate the light onto a small pv cell which even gains some efficiency in the process and makes more electricity relative to its size. Of course the panel would have to be cooled to prevent reaching high temperatures where it is quite likely to fail or even melt. So say we cool it with water and then use it to heat the house or store it in boiler for use in showers.

 

But I dont yet know what temperatures solar cells can survive, but since they are usually uncooled and exposed to full sun I guess thats quite high.

 

And by the rule of tumb I guess that for every kilowat of electricity you would probably get about 2 kilowats of heat.

[Michaelangelica]

This Hypography thread may be of interest. it has been running continuously for at least a year- along with champion threads like Quality Jokes etc- so the are a lot of people here that are interested in the concept.

http://hypography.com/forums/science-projects-and-homework/6465-solar-parabolic-trough-charcoal-oven.html

 

Also, are these of interest?

(I originally posted them at

Permaculture discussion forum • View topic - How can the Murry Darling System be saved for ever?

)

INTL: SPAIN Builds the first Solar Concentrator Tower in Europe

 

1000 Suns From Huge Concentrating Dish : TreeHugger

[DFINITLYDISTRUBD]

I think solar would best be harnessed by layering pv's on top of peltier cells on top of water heat collection to power stirling driven generators wich serve as coolers to maintain the temperature difference at the peltiers...particularly mit solar parabolics to bolster light and heat input:)

 

*Bump*

[maikeru]

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.

 

Interesting turbine design. Reminds me of what I posted on the Tesla turbine before, except that this one does have "buckets."