Solar Thermal Storage
By Richard Williams, 5/10/09
I have been fielding some questions about how I plan to store the collected solar thermal energy and I figured that I had better get out a supplement to what I have in my mind when it is so hard to describe in words. Once again through the digital media that we have all come to rely upon these days, I am able to present to the members and visitors of the engineering.com web site my ideas about a simple, relatively cheap and environmentally safe, non toxic way to do this. I will incorporate a lot of pictures in this blog article in order to convey that concept the best way I can. Pictures save a lot of words.
In this first picture down below we are looking at the outside of the completed thermal storage container. The blue Styrofoam boards are 2 inches thick (5.08 centimeters). This is a pretty high “R” value material and I haven’t worked out all the known values as of yet. I rushed out this design with screen shots in order to get my main points across to the readership. This is intended to be buried under ground in an actual project and needs to be well insulated to be able to preserve the greatest amount of that thermal energy for later use. One of our members told me that the melting point of Styrofoam insulation was 250 degrees Fahrenheit (121.11 Celsius). This member has been very helpful with her ideas and comments. The general outside dimensions here are 18 inches thick (45.72 Centimeters) x 4 feet long x 4 feet wide (4 feet = 1.2192 meters) This would also be lined with 5/8 inch Sheet Rock on the inside to help protect the Styrofoam from any extreme heat. My solar mirror array project was scaled down to ¼th the full size in order to save space, material costs and my back. I’m working alone on everything in my back yard. The only thing not shown here is the outermost physical protection of plywood that would be used to cover everything blue on all sides. To prevent water damage from rain when we get it I would use a thick plastic sheet material to repel any moisture from entering the storage unit. The approximate storage capacity is 20 cubic feet (.5663 cubic meters).
Next screen shot is a quick look inside the empty container box without the sheet rock or coils shown and one side removed. Remember that I am in uncharted waters here and I downsized the thermal storage container box to more closely approximate what would be used on the full sized model which could be four times this size in capacity.
Here is a look at the inside with a sliced view close to the bottom which also shows the 5/8 inch (1.5875 centimeters) Sheet Rock that will line the inside to protect the Styrofoam.
Here is another look at the container with the top insulation and outer physical shield hidden. Notice that at the bottom there is a copper coil of ½ inch (1.27 centimeters) soft roll out tubing placed two inches from all edges and also two inches from the bottom sheet rock. Picture a dense material placed inside of this box to be heated by this coil like sand or very small rocks. This bottom coil will be an ethylene glycol and water mixture of about 50% dilution strength like an internal combustion engine’s coolant system. Because this hottest coil will be coming from the solar mirror array, I placed it at the very bottom for no other reason than because heat rises and should also follow that same law inside of the container, which will help to migrate the heat more evenly from the bottom up. I hope.
Another look at the first coil placement with a slight isometric tilt.
Now let us place the second coil or pickup coil that would have plain water suitable for bathing or home heating through baseboard radiators using thermostatic control of the usable heat available. I respectfully bring to your attention that the top pickup coil would be placed at a perpendicular angle to the bottom coil and 4 inches (10.16 centimeters) down from the top, insuring that it will be away from the sides and be well embedded into the heat rich medium that I still have to decide upon that I will use. I exposed one of the sides to more graphically convey to you what I am talking about.
At this time I am theorizing that the heat generated by my 72 mirror solar array as shown in previous articles even at a quarter scale will produce some very significant heat values and I certainly do not want a second project blowing up on me because I failed to plan on the excessive steam heat and pressures produced by my flat plate collector design, I did back in the 70’s. That was very embarrassing to me and could have been tragic because there were newspaper people there along with our town mayor to witness a demo of my unit. It’s size was impressive and so was it’s explosion. L
I’ve included some last screen shots down below here that I put together tonight to end this expose’ of my plan for the storing of this solar thermal unit’s free collection from our sun. I am hopeful that it got my ideas across to the readers out there and also that it will help to inspire a new awakening into the solar revolution that must occur. We are helping to destroy our atmosphere by burning fossil fuels, when we have ways of producing energy without serious pollution as we do now.
Bye for now and I hope it was useful to you and your own ideas. J