Daniel and Eduardo Rivero are pig farmers who live in the Andes mountains in the village of Callapa, near La Paz, Bolivia in South America. Located at about 12,000 feet in the mountains, the temperatures at night are very cold yet during the day, the temperatures are warm with a strong sun.
They have a farm where they raise pigs to be sold at the market. At night, the baby pigs are cold, get sick and sometimes die due to the colder temperatures.
The farmers are poor and rely on selling the pigs to make their living. When the baby pigs cannot survive the cold, the farmers lose their investment. It is very important that they keep the pigs alive so they can sell them later. They wanted to find a solution to keep the pigs alive that was cheap, readily available and that would not harm the environment. The baby pigs warm themselves in the sun during the day. After seeing how smart the piglets were, the farmers too decided to use the sun!
Here is a picture of the structure before they started the work. Note that the building is white which will reflect the heat of the sun. The building is also made of brick. Brick is not a good insulator and so this building is very cold in the mountain nights.
The farmers decided to build a greenhouse that would use the sun to make the building warm for the pigs. The greenhouse has a roof made of a material that the sun can pass through, allowing the heat to enter the building. It works the same as when your car is parked in the sun and gets hot inside. They painted the wall a dark color to absorb the sun's rays and store the heat for use in the night.
Here is a picture of the farmers after they completed the greenhouse. They are happy because they make more money by keeping the baby pigs healthy and warm. They are also glad that they were able to build a simple structure that uses a free energy source available every day and that does not harm the environment.