Thermosiphon Solar Water Heater

Since it is winter time and I have not been doing much gardening, I have decided to undertake a project to hopefully reduce my heating costs. I am still in the process of acquiring the necessary materials and so I have not yet tested this system. I plan to build my first one out of plastic materials and PVC piping. I would really prefer to use metal (for environmental purposes) but the plastic and PVC will be cheaper and easier to work with until I am certain this design works as planned.

First, a little understanding of what a Thermosiphon is:

 A thermosiphon is a relatively simple device which uses the natural convective forces of water. Essentially hot water rises above cooler water. When the water is channeled properly, you can use the rising hot water to create a circulation.


Next, how to use this to my advantage:

My house sits so that one side of the house gets a lot of sun and the other side is shaded with trees. My theory is that I can place the solar heater in the sun and the storage tank (see discussion below) on the opposite side of the house in the shade. I can connect the heater to the storage tank by running the pipes under the floor of my house (my house sits above grade). I plan to close off most of the vents under the house (I'll open them back up in the spring to allow for circulation) to minimize heat loss. I am hoping that the heat dissipation from the pipes will heat the under side of the house enough to reduce my heating costs. Since this system is entirely solar powered any energy savings will be a direct reduction to my heating bill. I can drain the system and open the vents under my house in the spring to prevent heating during the summer.

My Design:

As I mentioned earlier, I have designed this system but not yet built it so I am not certain it will work as designed. However, from my research this system should work. I am hoping to acquire the materials soon and have a prototype built before the coldest part of winter gets here. So here is my current design. I will not go into the details of the design of the solar heater or connections in this posting; however, I am sure there will be more discussion in the days to follow. I would like to make two notes about the design:

1. There needs to be a pressure relief tube included - this should be a pipe which extends out of the top of the storage tank and rises above the highest point of the system. This tube will allow for filling the system as well as an escape if the water heats to the point that the system begins to build up too much pressure.
2. There needs to be a drain valve at the lowest point of the system (possibly one on the heater and the tank) to allow for draining the system in the summer.