Solar heating using Aluminum Cans  - this was an entry for a contest based on a personal study/project. 

 This project aims to repurpose recyclable 250ml aluminum cans to create a solar heater for home, cottage, shelter, cabin, garage etc. I am using the Aluminum's thermal conductivity properties which heats or cools relatively fast depending on the application. For this project I make use of the Aluminum's heating property due to absorbing heat from the sun which will heat the air once circulates inside the cans. The cans are connected in vertical columns using 3d printed connectors as explained below.

Materials needed:

- 250ml aluminum cans with the top and bottom parts cut and removed;

- printed connectors, printed elbows and Tees, printed wall-through connectors, ventilator spout and damper;

- for the enclosure:  wooden/plastic insulated box, Glass (Tempered preferable) sheet or Plexiglass, Flexible plastic hoses to run through the walls, Heat resistant Glue or Silicon. Since this project is customizable, I did not include an exact dimension of the enclosure since this will depend on the location, height and width of the particular project. The system can be very easily expanded since it is scalable by adding more connectors, tees and columns as necessary;

- Black paint to paint the aluminum cans and box interior;

- small servo to open/close the damper - servo used here is a HITEC 70mg but there are other similar sized servos on the market which will fit the mount;

- arduino board with 2 Temperature sensors (HDT11 or HDT22), arduino LCD (optional) and one 5V relay;

- computer fan;

 The project involves using of aluminum cans with top and bottom parts cut. The cut cans are connected vertically through printed connectors (shown in blue) which are the essential part of this design as they connect the cans, attach to the enclosure with screws and they mainly help creating a circular uprising motion of the air inside the column once the air is heated by the sun. 

The design of the connector allows to be printed without any supports and inside I included 3 fins to create a small air ‘vortex’ which will help with moving the air efficiently for better heating. I looked at several iterations of cans air heaters built on Youtube which seems to work well in cold areas.

Please refer to the attached drawings => The heating is achieved by the air movement through the aluminum cans due to heating and natural convection created. The cold air is drawn from the lower part of the room, travels through the aluminum cans and as it moves upward it heats up. The convection created will move the air from bottom to top where it will exit and travel back to the room at a higher temperature. The cans will need to have the exterior painted with black paint as well as the inside of the enclosure box to attract as much solar radiation as possible. 

For better control of the temperature and air moving, I have added a 12V ventilator and a damper which will be controlled by 2 temperature sensors, Arduino board and one small Servo used in RC. There will be a temperature sensor outside and another one inside the room. When the Outside Temperature is Higher than the Inside Temperature, the Arduino board will engage the servo to open the damper and turn on the fan which will create the forced convection.

When Outside Temp is Less than the Inside Temperature the Arduino will stop the fan and will engage the servo to close the damper. The damper and fan wil basically make sure during the night the air circuit is closed so the warmer air from the room will not exit and be cooled. Also during winter storms the enclosure box may be covered with snow which will block the sun rays to heat the aluminum heater hence this automated system will ensure the heat will be preserved inside the room.

The enclosure box will have the exposed surface area covered with glass or plexiglass only and ideally should face South. The height/width of the box will be based on the height of the wall but also based on the desired width. Basically this system is scalable and can have as many modules as possible to heat the desired area. 

For vertical columns I used the entire height of the aluminum can. The top and bottom of the can will need to be cut and removed and the can will be painted in Black on the outside.

For horizontal connection, I designed based on the half of the can's height which will be connected using elbows and Tees.

Below is the Arduino Sketch with the following pin connections (please refer to the Arduino pin out image):

- the Outside temperature sesore will be connected to the A1, Inside Temperature to A2;

- Servo to pin 6

- Relay to pin 7

#include
#define dht_dpin1 A1 //no ; here. Set equal to channel sensor is on
#define dht_dpin2 A2
dht DHT;
int relay =7;
#include
int servocold = 179; // Angle in which servo will go to
int servohot = 0; // Angle in which servo will go to
Servo servo1;

#include
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup(){
lcd.begin(16,2);
Serial.begin(9600);
servo1.attach(6); // Attaches servo to specified pin
delay(300);//Let system settle
//Serial.print("Temperature and humidity\n\n");
delay(700);//Wait rest of 1000ms recommended delay before
//accessing sensor
}//end "setup()"

void loop(){
//This is the "heart" of the program.
DHT.read11(dht_dpin1);
lcd.setCursor(0,0);
lcd.print("Out Temp ");
lcd.print(DHT.temperature);
lcd.println("C");
delay(800);
lcd.setCursor(0,1);
lcd.print("Out Humd ");
lcd.print(DHT.humidity);
lcd.println("%");
delay(500);
DHT.read11(dht_dpin2);
lcd.setCursor(0,0);
lcd.print("In Temp ");
lcd.print(DHT.temperature);
lcd.println("C");
delay(800);
lcd.setCursor(0,1);
lcd.print("In Humd ");
lcd.print(DHT.humidity);
lcd.println("%");
delay(500);
if (dht_dpin1 > dht_dpin2 ) {
digitalWrite(7,HIGH);
servo1.write(servohot);
} else {
digitalWrite(7,LOW);
servo1.write(servocold);
}
delay(500);
}