Dual Solar Shed (regulated and Unregulated)

The goal of this ible is to show how I set up two small-scale solar systems in my shed to make it more usable. The first is a battery and lighting system (slightly larger) with an old travel panel that I had not used in a long time. The second is a small fan that exhausts the hottest air from the ridge of the roof, through the gable, using two cheap solar cells I had used for small learning projects in the past.

The nice thing of this project is that I will show two solar setups side by side, a regulated setup with a battery, and an opportunistic unregulated setup that uses power as it comes.

The basic tools needed are

• screw driver or drill
• snips
• wire strippers
• soldering iron (not needed for the battery setup)
• multimeter (optional, but could be useful to make sure everything is properly setup)
• a flat-head screw driver for adjusting the terminals on the solar controller

The materials needed are

• screws
• wiring. Preferably UV resistant, but if you don't have it just as I did not, you can keep an eye on it. The actual side capable of high current is hidden in the shed, and the outside wires won't move, so normal wiring will easily last a year or two before it starts cracking. If you can get your hand on CSPE sheathed wiring, then that is your best bed, but it is very pricey and normally very high GA. Otherwise, there are other options that will be more durable than vinyl like silicone and this stuff.
• some sort of caulking to seal up the holes (optional)
• solar panels. In this case I use
  • a small 10-20w at 12v panel (I had an old 7.5)
  • two 10cmx6cm cells 5v at 2.5w.
• a fan
• some modular 12v LED lights with a switch
• A solar power controller with 12v out (optimal to power LED lights as it means less voltage changes and therefore near perfect efficiency from the battery to the lights; if you are are using this for 5vDC or 120V ac, then there are better options for the same price, like dual usb, or better charge state indication etc.)
• a 12v lead acid battery of the size you want. I just used salvage. If you are buying a battery, don't bother buying one with a W/h rating higher than 10x the watt rating of the panel (as this represents a full day of optimal charging).
  • For a 20W panel, a battery like this would be optimal
  • For a 10W panel, a battery like this would be optimal

  • Bigger is better. The controller does need some power, so if your system is too small, it may not be very useful in the winter.

By using the power directly, when the sun is at its strongest, the fan vents out the hottest air. This will create a very small negative pressure and fresh air will seep in. This is not meant to ventilate per say, it is certainly not enough to properly exchange the air in the shed, but it does help keep the shed not too much warmer than the outside temperature, instead of rising throughout the day.

This makes the setup incredibly simple, just wiring the fan to the panel is all that is required. I glued the panels to a small piece of wood and tacked that to the roof of the shed.

A single cell can be used, but I had two almost identical cells, so I put them in parallel. This increases the power, which means that when the sun is not optimal, it will still run a bit more. When solar cells are under shaded light, they will rapidly reach their full voltage (which affects the speed of the fan), but the power (amps or milliamps in this case) which are required to overcome the resistance of the air and friction, remain very very low until enough light is available. This is why I opted to double power (parallel panels), rather than doubling voltage (series panels). Not only that, but more voltage = more speed = more resistance. In this very low power situation, it would reduce the efficiency (although normally as voltage goes up, these types of systems do become more efficient when amperage is higher).

To wire up the cells, I just soldered the two + sides together and the two - sides together.

I drilled a hole in the top of the gable and secured a small piece of screening in front of it. I then screwed the fan over the hole.

The two cells were glued to a small piece of plywood which was tacked to the roof. The wire was fed from under the flashing into the shed, near the location where the fan is secured, and the wires connected.

That's it! Although limited in uses, such a setup is incredibly simple and extremely efficient as there is no conversion or storage of power.

Using a solar regulator and a lead acid battery, the power is converted to the proper levels to maintain a safe charge of the battery, and then power is drawn from the battery rather than the panels. In this case, I highly recommend a regulator with a direct 12v output. This way you do not have to waste power inverting the 12v from the battery to 120v AC and then back to 12V DC.

When setting this up, the battery needs to be connected first, and then the panel second. Once everything is up and running, the 12v can be used to power the lights.

The lights were scattered to maximize usefulness. The important part here is to have a switch.

I cut off the end that plugs into the AC adaptor, but not before properly identifying the wires and which part of the connector they corresponded to. I then used a multimeter to check the polarity of the AC adaptor, to make sure I don't invert it.

The shed is now much more usable, with more light during the darker times, and less heat during the hottest days.