Week 9

After a few quiet weeks, we have lots to report! We’ve spent the last few weeks working on several small projects to incorporate into our new structure and as of today, most of them are complete! The main four components we’ve installed are a passive cooling “air conditioning” unit in the window, a two-tiered roof, a solar chimney, and a ventilated block near the bottom of the structure. Below are pictures and descriptions of each element.

In the bottom right corner, you can see our ventilated block. The team is still working on a few different molds to incorporate ventilation into the blocks, however this one did not require a new mold. We simply turned the block and added removable screen inserts to the holes. The benefits of this model are that it doesn’t require a new mold, the openings allow for cool air to enter the building, and the screens keep the bugs out and can be easily replaced if damaged. A practical issue with this method would be that turning the blocks might get in the way of reinforcing the structures with rebar which they often do in Senegal.

Above is the new two-tiered “cool roof” we’ve designed and installed. The design is pretty simple; there are two layers of corrugated steel with about 3 inches of open space between them. As the sun hits the top layer, the steel absorbs the heat, but instead of being absorbed into the house, it is then reflected by the inner steel layer and then the natural breeze flowing between the two layers pushes the hot air out before reaching the inside of the house. This seems like a viable option for the Senegalese people because it uses the same materials they typically use for roofs, so cost, aesthetics, and availability should not pose issues. Already we can see that it’s working as the top layer’s temperature is about 10-20 degrees hotter than the inner layer.

This is our passive cooling “air conditioner.” The idea behind this system is that there is a pot filled with cool water inside the window unit and the heat causes the water to evaporate which cools the air surrounding it. As a natural breeze comes through the unit, the cooled air will enter the home. While cost and availability of materials shouldn’t be an issue, one thing we might need to consider is the risks of having standing water in their homes as this provides the perfect breeding grounds for mosquitoes. To prevent this from happening, we could build a screen door of some kind on the interior to prevent bugs getting in from either side.

Our solar chimney builds off the simple principle that heat rises. By painting the chimney black, it will absorb more heat which causes the air inside to heat up and rise. As the hot air inside the chimney rises and exits, it continues to pull the hot air from the inside of the building up and out. This system works well with the ventilated blocks at the bottom because it creates a flow of cool air entering and hot air exiting.

Just after one day we are noticing huge changes inside the structure. In the past few weeks, we have typically been finding the inside temperature to be the same or only one or two degrees cooler than the outside. However, with all our new components, we are finding the inside of the house to be consistently five to ten degrees cooler than the surroundings!