Solar Fire Concentrator/Structure
Always good to start with a simple animation.
- We star with a base and a vertical post.
- We add a boiler on top (supported by an inverted tripod).
- We add the cold pipe and steam pipe as shown.
- We weld a boost (larger piece of tube that fits snugly on the main post).
- All the above parts a fixed, as in they do no move in relation to the ground.
- Then we add our central rotating piece, the whole frame rotates on this point.
- We then add the main beam as shown.
- The next step is to add the frame and the rows, but this is not shown in the animation.
- Then we add the mirrors.
- And concentrate the sun.
- Watch the video below should explain well how the rest of the machine is put together and works.
- Or download the video directly in MP4.
How to raise the boiler
One question that had been bugging me is how to raise the boiler. For the Solar Fire P-32 we put a hinge above the frame, which meant we had to go around the hinge with the pipes (requiring 4 corner for each pipe, so 8 pipe connection in total just to go around the hinge), so that to raise or lower the boiler we could disconect the pipes (if the pipes are inside the main post a hinge doesn't serve much of a purpose.)
The solution to this problem is putting the hinge directly on the base and so only needing to disconnect the pipes at the lower corner. Especially for the steam pipe this means only one corner which increases efficiency and leaks. A steam leak is a lot worse than a water leak since the steam carries away both the energy we've put into it and a significant amount of pressure of the system. If cold water leaks through a the same size whole far less energy leaves the system. Also, since the output steam is hot ~200C it has a tendency to grow any leak faster than cold water. So, for these reasons reducing steam pipe connection to 1 is a significant improvement. The water pipe could also go up the main pipe to reduce connection but this would have a cooling effect on the steam pipe, causing condensation which causes more heat transfer and so more condensation. So we want to limit the proximity of the cold pipe with the hot pipe, even if it takes more connections, as seen in the video. We could use a wider post but we want to limit the width of the post as well.
I talk about pumps under the Solar Fire System Engineering Diagram.
A pump is required to put water in the boiler first to start the machine, this can be a basic hand pump, then later when the concentrator is working. Under operation a hand pump is also possible (that's how we operated the P-32) but it takes a lot more effort since the system is now under pressure. We reached 15 Bar (220 PSI) and the gauge was still rising at the same rate, but we stopped since the system was designed for 10 Bar (150 PSI).
So for continuous operation of a steam engine, the steam engine can drive a compressor that continuously feeds water back into the boiler. In the video we see the compressor just pumping water back into the water tank.
Note that a compressor has small cylinders to pump a small amount of water under high pressure, the same amount of power put into a water pump would pump significantly more water. For operating the machine under load about 10% of the energy is required to feed water back into the boiler. It's also possible to do it with a Steam Ejector, a popular choice in the skills required are probably not as available as a basic compressor.