As most of your are aware Alberta Aquaponics has been able to grow through the winter for the last 3 years with at least marginal success. We are able to accomplish this by taking advantage of many different techniques that range from meat rabbits being moved into the greenhouse to act as 8 BTU bunny heaters through to the creation of a popcan solar furnace (some of the videos of the creations can be found here)
Over the last year (which was shelved for the summer) and again over the last few weeks I have been working in a new project to heat the greenhouse over the winter that uses a solar concentrator.
The solar concentrator is little more than a satellite dish, something that is available pretty much anywhere in the world, and regularly disposed of as a waste product.
The satellite dish has a parabolic shape (curve) that works as a means of focusing energy, (in this case the suns radiant energy), to a focal point.
To start with, I have taken the satellite dish and applied standard reflective tin tape (see video for my progression of the build) to the dish to create a reflective surface that allows for the solar radiation to be reflected back to the focal point to generate heat.
As you can see from the video this has been a process in getting things working and the bugs worked out.
I now have several of the concentrators created and have collected a basketball backboard and pole from Kijiji (picked up for free) and a used bicycle (also free) that I have put into play for the mount and tracker for the array.
I started off by taking off the backboard from the pole and put the pole in the ground.
I then cut off the front forks of the bicycle from the frame, removed the tire and brake assembly, inverted them and (with the help of Sam Skogen) got the unit welded to the top of the pole.
The front forks act as my two axis points for being able to follow the sun across the sky. The backboard fits into the axel mounts giving my my North – South axis and the pivot of the steering bearing gives me the East – West axis.
For the tracking system I opted for purchasing a premade unit rather than doing a DIY build simply due to cost. I purchased a dual axis Suntracker from Windy Nation and got it set up and put in play. This took a little more design than I had hoped for and in the end became a little bit of a chore to get worked out for putting together.
In the end I used the gear from the bicycle attached to the East – West actuator for the pivot and the North – South actuator bolted directly to the backboard for its axis movement.
The focal point is now an aluminum block as compared to the copper that I was using last year. I found that the heat I was getting was melting out the solder and then burning holes in the copper pipe even when water was running through it. The blocks, although not perfect, are better able to handle the heat of the concentrator and should hold up better (fingers crossed). In the even that I need to change them out, I have been able to source the replacements for a relatively cheap cost.
With that the array was put in place and plumbed into the greenhouse via a circulating pump to the barrels of water to act as a battery for the hot water. The water is cycled from the barrels to the focal points of each of the dishes on the array and then brought back to the barrels in the green house where they passively radiate the heat to the ambient air inside.
Here is where I am not at a bit of a stumbling block. I started having problems at this point with power getting to the solar tracker. At first I thought that it was because the power of the single 30 Watt panel was too low for the task, but upgrading that to a 50 and then to a 90 Watt panel did not resolve the issues. I then connected it directly to a battery (twin 6 volt deep cycle batteries) connected to the solar array on the garage and I have the same issues. I am getting 12 volt to the unit, but the unit is unable to transfer that power to the actuators.
At this point I am awaiting technical information back from Windy Nation on the problem and most likely will be using the warranty return to get it all up and functional.
Stay tuned for more updates as I go along and with luck a new video of the entire unit when it is functional.