Making a Solar House

This project is making a Solar House that can function without connecting to The Grid, as well as to teach about how solar panels are used and how basic circuitry works.

For the House:

• Cardboard
• Hot Glue
• Paper and Pencil

For the Circuit:

• PV Panels
• Battery
• Car Cigarette Lighter to USB
• Micro USB Cable
• USB Switch
• Wire
• Switches / Potentiometer
• Loads:
• Fan
• LED + Resistor
• Active Buzzer

Panel tilt is seemingly self-explanatory, but it is more complicated. The tilt of the solar panel has a large effect on the solar production, while a flat or fully vertical panel is the easiest to implement; they are only optimal for a small section of the world. The way you find the optimal panel tilt is by setting it equal to your latitude.

Azimuth is a direction relating to the compass, where 0 degrees is North and 180 degrees is South. Solar azimuth changes throughout the day, so panels won’t be at maximum efficiency for the entire day, but you can find the average azimuth for the maximum efficiency. Panel Azimuth should be roughly perpendicular to the Solar Azimuth for maximum efficiency. 

Start figuring out a rough floor plan. I recommend looking at reference images of both full size houses and doll houses. Then find rough dimensions, try to make one roof face roughly your latitude, in my case 38°, using trig (or a trig calculator). I aimed for about a total size of around 24"*24"*6", and got pretty close. Make sure your house is big enough to let you add wiring and make changes. I used Fusion360 so then I could export the pieces to a laser cuter, and so that the pieces could all fit perfectly.

I encourage starting with the backboard, which should be a silhouette of your house outline. Afterwords, start cutting the outside walls and gluing them together. I used a laser cutter to cut the pieces to the correct size, but cutting them manually is much faster and easier. Then cut out the inner walls, make sure you account for the width of the outside walls so that the inside walls are the right size. If your house can't stand on its own, use extra pieces of cardboard to reinforce the walls.

There are two types of Circuits: Series and Parallel.

Supply Side:

For the supply side, Series vs. Parallel matters depending on if we want a higher voltage or a higher amperage. Connecting the panels in series would increase the voltage, which for the purposes of our project is unhelpful because we are going to step it down to 5v for the battery. Connecting the panels in parallel would increase the amperage, which is more useful to us because the voltage is going to get stepped down.

Load Side:

Series circuits have each load connected in a line, where the positive connection of one connects to the negative of another. Parallel circuits have each loaded connected all together at two points. In our houses, we use parallel because it is reliable and still works even if a load fails. In our solar houses, we will do the same for simplicity and because we want the circuit to keep 5v.

In this step, we will solder LED's and splice a USB switch.

For the USB Switch:

1. Cut the female (port) side of the switch off
2. Strip the wires and separate the wires, if there are any data cables, ignore them or cut them off (Non-Red/Black Cables.)
3. Optionally, solder extra wires to the stripped ends

For the LEDs:

1. Strip two wires, at least 3 inches (ca. 8 cm)
2. Solder 3 or more LEDs short ends to individual resistors, 220-330 Ω
3. Attach the LEDs perpendicular to the two wires with solder, it should look almost like a ladder

Now it's time to start setting up the electric part of your house. I suggest you start by laying out all your components on a large piece of cardboard. My circuit (The Picture) works as follows:

1. The 3 PV panels are connected in parallel
2. The power from the panels are connected to the cigarette lighter, which is being used as a 24v+ to 5v step down transformer
3. The power from the transformer goes into the battery, which will slowly charge it
4. The power from the battery goes into a USB switch, which has been cut and stripped.
5. The power then gets split into the loads, which are connected in parallel with switches (Not shown in this picture, shown in the house).

In my project, I started with the solar panels and attached the various components in the order they are used. Make sure that the PV panels are secured so they don't fall off, I used duct tape. Then attach the cigarette lighter/step down transformer, either with alligator clips or through soldering. Connect the battery to the cigarette lighter and to the USB switch that you stripped earlier.

Start adding your loads into your house. I added my fan to my second floor so it could be seen, and kept most of my loads close to where the switch panel would be. I used a piece of cardboard and cut holes for my switches and potentiometers. Solder wires onto your potentiometers and switches if they are not already on. Then connect one side of the switches (In my case the red wires), to the positive coming out of your USB switch. Connect the other side (Black wires in my case), to the individual loads, labeling the respective switches. Lastly, connect the ground wires coming out of the loads together to the black wire coming out of the USB switch.

The Loads I Used:

• Fan - 4.3 V - 0.3 A
• Active Buzzer - 5V - 1.6 mA
• 3 LEDs (Min. 2.5V - 0.1mA)(Max. 5V - 22.4mA)

• Make sure that each of your loads work alone before attaching them to your house
• Make sure that your fan is DC (Most Should Be)
• LEDs burn out almost instantly if used without resistors
• Use a multimeter to make sure that your connections work.
• If your battery drains very quickly, make sure there isn't a short circuit
• You can reverse the fan direction by swapping the two wires