Solar Fire Concentrator
Note: this name is a legacy name from the time when we were pursing the lower-efficiency Tesla turbine as the heat engine of choice.
The current solar concentration design under development for the GVCS is Solar Fire. Solar Fire started as a simple technique to roast coffee and cocoa at the village scale. These older designs are available on www.solarfire.org and are still very relevant to small roasting, frying water boiling operations.
Recently the technique has made significant developments to reach the local crafts (semi-industrial) scale.
Best way to understand the current model is through the film below.
Notes about the film
- The steam pipe arrangement was temporary since we hadn't worked out yet the best way to pass the steam pipe directly down through the main post and out the bottom.
- A compressor has small cylinders to pump a small amount of water at high pressure, the compressor is for pumping water back into the steam generator (micro-boiler) but in the video just pumps back into the tank for a visual aid. The same amount of power into a water pump would have significantly more volume.
- We had to make the video before rather than after, since the Energy Vagabonds (who were crucial in developing this model) were leaving the next day and they had an HD camera.
- Shortly after I fell extremely sick and only got better the morning of my flight back home. So I wasn't able to film the final setup even with my camera.
The design reduces costs by:
- Using only standard construction material.
- Requiring no mechanical bending.
- Requiring no special skills not widely available.
- Requiring no machining of pieces (just cutting, holes, welding).
- Requiring no electronic tracking to be used effectively (though we will also develop automatic tracking for situations that call for it)
Tinytech Plants, can supply the machine for 5000 - 7000 USD, which works out to 156 to 218 USD per square meter, 250 to 350 USD per peak kilowatt thermal. They are currently working on a larger machine that they estimate will be about 33% less per watt, and run the steam engine seen in the video continuously. These costs are lower than all other concentrators I know of.
So, the economic viability of the technology is sound, and it can be built locally for less.
And we of course intend to drive down costs further.
The final intended fabrication model is that local companies build most of the structure, and only special parts/applications are shipped from outside, similar to how the construction industry operates already.
- Drawings are now available at Solar Fire Drawings.
- For the moment there are no dimensions as these are calculated automatically be the Prometheus Calculator (release of version that does this is imminent).
- See Solar Fire Concentration Structure for notes on the structure.
Tube setting and mirror bending
- Note: In reality the mirrors would be turned 90 degrees to be perpendicular to the rows. The mirror is shown here placed parallel to the row simply because it was easier to draw.
- See Solar Angle Calculator for notes on the angle setting.
System Engineering Diagram
- See Solar Concentrator Systems Engineering Breakdown Diagram for notes on the diagram.
- DOWN LOAD FULL SIZED IMAGE\
Simulator and calculator
Though the mirrors can be set empirically (by eye) this requires 2 hinges to control the mirror placement. 2 hinges multiplied by 360 means 720 hinges. But beyond the hinges, actually setting the mirrors seems to become exponentially difficult as the size of the machine increases. For the Prometheus 100 it took me a week and the machine only had 100 reflectors (9 m^2). So setting each reflector by hand for a machine over 3 times larger would have been extremely tedious and long, and I have a lot of experience setting mirrors. The reason it becomes exponentially difficult is that all the reflectors and all the rows have to work in harmony, and the more there are the longer it takes to get them all on target at the same time. Also, for someone making the machine for the first time it would really be an obstacle. Also, the work has to be done in the blazing sun.
So for all these reasons there's a huge advantage in calculating each inclination and setting the reflectors "in the shade". For this we need a computer program. The program can currently be downloaded here, however it's currently not so user friendly since it had to be written on a tight time frame, before the structure of the Solar Fire P32 was complete.
The program will be integrated into Open Source Ecology with lessons and tutorials after the 3D CADing is complete.
There is also the Prometheus Calculator, written in Open Office Calc (spreadsheet). The calculator is a sort of prototype for the simulator; for instance, the calculator can only give you the ideal inclinations of the reflectors for a given sun angle, whereas the simulator can calculate all the ideal. which is far more powerful and can create the graph sequences of the focal point, seen below.
This simulates the concentrator without any random error or "folding technique".
This next sequence simulates with a random error of 1 degree and the folding technique (to compensate the aberration when the sun is low, in the morning and evening, the whole structure can be folded to compensate: about 15-20% more energy can be captured using this technique, which is not seen in the P32).