Since we are committed to creating human-scale, DIY solutions, we will be experimenting with three models of collectors that are straightforward enough to be built in one’s own home. Yesterday we introduced the five different types of conventional solar collectors. We also live in an area that experiences deep freezes and therefore we cannot test the integral-collector storage design, although this is likely the best design for those of you living in warmer climates. We cannot build vacuum tubes, so that system is out. We cannot build a true concentrating collector, but we will attempt to combine reflective mirrors with the flat-panel design, as the concentrating collector makes the most heat for a set amount of space.
All models will be built on the small scale for testing before the best design is used at full scale for the installation build. Other than the configuration of the collector pipes and materials, the models will be identical in build, size, and internal water capacity. The models will be run through side-by-side tests under identical conditions to determine which puts out the most BTUs. We will measure both the increase in temperature and volume of water put through the system to calculate this comparison. We will run water through the models at slow, medium, and fast constant flow rates and then at the maximum flow rate (varies by model) to determine the optimum speed for maximum BTU output. We’ll also record the ambient temperature and amount of solar radiation.
Design 1 – Manifold Collector
The first design is a manifold flat-plate collector. Water enters a large pipe in the bottom of the plate before moving up narrower pipes to a large pipe at the top before flowing out of the collector. All pipes are copper. The rising pipes are connected to a large, thin sheet of metal that spans the interior of the frame. The back of the unit is insulated and the front is covered with glass. This design is expected to have faster flow rate than the next model, but may provide less heat in that time.
Design 2 – Circuitous Collector
The second design is a circuitous collector. It is in a frame identical to the other designs, but instead of water flowing through many pipes rising up the collector, a single copper pipe snakes its way back and forth up the face of the collector. It is also connected to a large, thin sheet of metal that spans the interior of the frame. It is glazed and insulated. It is expected to have a lower maximum flow rate than the first design but a greater heat output.
Design 3 – Semi-Concentrated Collector
This design is unique as far as I know. It has the same frame, insulation, and glazing as the first two designs. The copper pipes are arranged in the same manifold configuration as the first design but instead of a large, thin metal sheet to collect heat, a series of long mirrors are angled to focus the sun’s energy on the pipes, similar to a concentrating collector, but in a stationary orientation.