I made a quick model in SW to check the mass of a sample configuration.

If the main purpose is to just heat the water... Then simple wound 19mm polytube in a black box with a glass/plexiglass cover, will easily boil the water. To a point where you actually need to have a steam pressure release valve installed.

I think you are underestimating how efficient the "Flat Plate" setups as you refer them actually are.

Then I dare say you can't do much better than the tried and true method of Steam Engines that burn a medium for heat.

Exactly that. I agree with wolfrick. It's safe to assume that nobody would be mounting one of these on a tractor.

:-).

If you want more power you have to make arrays of small solar thermal collectors. The important requirement is the concentration ratio(10:1 or higher).   No matter what you do, if you want to use solar power you have to cover large areas of land. So the only way to make it economical is to use the cheapest possible material. Out of plastic, reflective surfaces and photovoltaics, Plastic is the cheapest.

Hi, interesting idea, to make a lens from a watertube. I wonder how much energy gets stuck 'in' the tube. Also wonder about how it practically works out, if you get a decent focus to work with. About suntracking, I think soon we will have that nut cracked. I am working on it using software from cerebralmeltdown.com as a start (open source). We are not there yet, but it's a matter of time!
Anyway, great you take a whole new approach to sunfocussing. Hope to see a real life image!

Can somebody do a Net-Energy analysis on this? For the same size what would be the net energy gain for Water tube cylindrical lens collector, a parabolic trough collector and frensel reflector type collector. Kind of a comparative study?

I think the Solar Thermal Concentrator should be build upon raw material find in desert

THink open, but think also big



We need a Glass expert,

A simple design,

And automated tools for building the glass parts

In fact, It could be easier to get a walls of glass tubes with steams engine producing electricity : because the raw material is in abundance, and the concentrator should be more difficult ( and expensive ) to build : I SUPPOSE

Then we directly produce more walls from our energy

the growth is exponential


BY THE WAY : In this design, you can use Water for producing electrical energy.... or even Algae producing, hydrogène, oil, methane , and biomass

Good stuff! Currently not using translucent polymers (mostly acrylic). For algae this is awesome. For solar, you can do with more economical materials?

Did you have a look at similar existing design via google.com/patents? A lot of them are over 20 years and belongs to public domain.

The cheapest way to do this would be with recycled 2 liter plastic bottles. You can find those for free anywhere in the world. I know you were thinking of a single very large tube, but a hundred or so bottles might work just as well, but cheaper.

I've been salvaging plastic bottles for a different hardware project I'm doing. I found five of them in one day, without especially looking for them, just by picking them up when I passed by them. 2l plastic bottles are EVERYWHERE and they're FREE.

Each 2l plastic bottle will capture sunlight from about a 285 square centimeter area and concentrate it onto a strip about 28cm long and 1cm wide. You'd need to use mirrors to reflect many of these strips of light onto a single tube if you want to boil water.

I have an idea that modifies this design.... Instead of trying for steam, if you have smaller versions of this you can try for convection. See my pic for how.... It would still have to rotate the heating pipe to stay in the focal point.

Due to UV cracking of plastics, I would go with plexi-glass tubing or, even better, lexan.

An engineer/physicist can chip in on this, but my understanding of the Carnot cycle is that the higher the difference in temperature (delta T), the higher a conversion efficiency you get. For converting low temperature differences into useful energy, an open-source Stirling engine would probably get better conversion efficiency than a steam engine.

OK, if the soda bottle can focus sunlight by a factor of 10, then line them up in a frame, and run black pipe or something along the focal lines in parallel, then output to a heat engine. You might get by with single vertical axis pivot to track the sun, and a simple adjustment of the pipes relative to bottles to account for sun elevation. Maybe not very efficient, but pretty cheap if you can get lots of bottles for free.

Concept for "soda bottle array": frame of 1x4 or 2x4 lumber, with crossbars that are notched to hold the bottle neck on one side, and a small shelf screwed into the bottom of the crossbar to hold the bottom of the next bottle. bottles are lined up perhaps three rows of horizontal bottles by 8 ft long in the frame, with three pipes underneath to get the heat. The array is tilted at the best sun angle, and has a vertical pivot such as a vertical pipe to rotate around to follow the sun. The pipes may need to be insulated to reduce losses. The output is manifolded to a heat engine, or hot water storage for home use.

Yeah, when I suggested bottle concentrators, I forgot that the aim was to make steam. You definitely need something bigger for this project, though bottle would be good for concentrating light onto photovoltaic cells

Given heat and sand, I can make shiny flat pieces of somewhat reflective stuff.

High temperature leads to more power. The laws of thermodynamics state that when converting heat to mechanical work, higher temperature leads to higher conversion efficiency.

Greetings All!

This is my first post on these boards and I'm happy to be able to take part in this conversation. I have a few thoughts that I would like to input here as well. Im not sure if anyone is still working on this concept but I figured I'd throw my input out there anyways

I love the concept of using a water filled tube for generating steam and thus electricity. It would be marvelous to see such a device in operation. There are a few of considerations to make when upscaling this idea to practically usable size. Materials, weight and climate. It would be important to use a material that would not react significantly to UV radiation from the sun. Typical plastic as found in plastic bottles does photo degrade. Acrylic turns yellow in the sunlight unless it has been treated against UV light, and glass is impractical because of its weight. There most definitely are solutions to this, but it would be fairly costly.

I did some math of a tube that would equal the large fresnel lens on the greenpowerscience.com measuring 49"x35". In order for the tube to have the same profile to the sun it would have to be 49" long with a diameter of 35". Looking at the weight of the tube and considering that water weighs approx 62lbs per cubic foot, then multiplying that by the 27.3 ft3 of the tube's volume we find the approx weight to be 1692.6 lbs. Perhaps using a lighter medium would help with this. Just for reference, the fresnel lens in this comparison weighs 21lbs in its wooden frame.

Lastly, climate. This is obvious but bears mentioning. This would not work in climates with moderately cold winters simply because the tubes would freeze. This would not be the case if the liquid in the tubes had a lower freezing temperature, just something to consider.

Have you thought of creating a long lens shape instead of a tube. It would reduce the weight, the amount of medium the sun passes through, while not loosing any of the surface area. See the attatchment or a basic drawing of what I mean. Also, I would recommend using distilled and/or  de-mineralized water as it will have less particulate matter in it, allowing more sunlight to pass through.

Anyways, I hope this project is going well. I would love to see an update on the testing anyone has done on this!
Peace

~Danial

Here is a video from some company called Matteran energy. They claim they can generate electricity from warm water. They also say they have a working prototype capable of generating 2.5 KW plus refrigeration. 

wow..5000 views. Keep it up.