This idea is inspired by the Ecole Polytechnique Fédérale de Lausanne's "Solar Thermal Energy Regulator system" (see http://web.archive.org/web/20121216042224/http://www.elektor.com:80/magazines/2010/may/solar-thermal-energy-regulator.1321945.lynkx ). As I understand it, the system uses (commercial !) evacuated tube collectors and the heating of the solar thermal collectors is done to eliminate fluctuations in the system and keep it operating as good as possible as the panels get into the shade as the sun turns.
In my view however, I think that a simpler system could be more effective, which simply disconnects the panels entirely as they get into the shade (such a system btw wouldn't need temperature sensors so the problem regarding the use of the semiconductor sensors would also be solved). In addition, given that a dsPIC controller is used, the system can also be made more advanced and include solar tracking (see http://en.wikipedia.org/wiki/Solar_tracker ) I am confident that relooking the design and adding solar tracking could have a great benefit to areas, other than Switserland (including areas in subtropical and tropical zones).
Setup[edit | edit source]
The idea is had is to make the whole system more modular and also usable in other zones (ie subtropical/tropical zones). In these areas, most building roofs will always be completely in the sun, and the areas also usually use regular flat plate collectors (cheaper, no big temperature differences making the use of transfer-fluid equipped panels not essential).
Thus, simply for modularity and ease of control, in my view simply disconnecting the panels would be advisable. The use of a solar tracker (although granted, for the system I use the solar tracker would give greater advantage than with yours) would make up for the possible losses taken by the entire disconnecting of the panel (rather than simply revving up/down the pumps).
A lot of the system's yield/losses can offcourse also be improved/eliminated by the placement of the panels. I am guessing that ie some parts of the house receive at a good part of the day full sun, and later on full shade, while others have pretty much half shade for the entire day. If a panel is placed on the first location rather than the second one, and if that panel disconnects immediatelly at the moment the shade sets in, we could definitely have about the same yield, and probably even more than at location 2.
Also note that the system would use a platform that can not only rotate, but also tilt, providing an even greater efficiency. See the decription of the batch solar water heater for more info.
For the sensors, the use of PT1000 sensors (which are sensors that can cope with the higher temperatures of the water without needing to empty part of it it in a pool, ...) are already a good improvement; however it can also be done without water sensors, or even without any sensors at all. How this is done is quite simple: since most of the system now only requires to track the sun, and turn on the panels off once they can no longer be kept (rotated towards) in the sun, we only require light sensors. Even the light sensors can be dismissed or a hybrid setup can be followed, now simply using data collected from a day's monitoring of the roof system (the system is monitored and the times are noted on a paper how fast the sun rotates, and what panels need to be switched off). This data is then inserted to the program. Things get a bit tricky if no sensors are used at all though, since during the year, the sun's rotation changes; this would mean we would need to calculate it out (with a formula ?, or again by monthly monitoring) by how much the initially recorded program needs to be changed at all accounts. It should be noted that I do think formula's exist, and programs such as Google SketchUp can even calculate the sunshine for each location at any time of the day.
I think that with this information one could either update the existing Solar Thermal Energy Regulator system or make a new version of it. At the moment, I don't think that a similar system already exists, and creating it would definitly provide a great (environmental & social) benefit to people in (sub)tropical areas.
Finally the project can be designed to allow implementation with the Open design water heater water heating system. Also, either the batch solar water heater (see ) and/or the evacuated tube water heater can be used with the system.
For the solar tracking platform; I would design it for use at either a flat roof, or simply for placement on the ground. A rotatable, tiltable platform is thus best used. In general, think of a round platform with the tank attached at 2 points using hinges. The tank is held up at an angle by a piston. The piston can change the angle by extracting/rectracting, while the platform itself can rotate using ball bearings (rotating over a secundairy round platform). As for the piping; this can be done by using flexible piping connected to the short welded inlet/outlet/overflow of the tank. The lower short welded pipe may need to be placed either on a side or to the front to not obstruct the tilting.