Building a new fog collector!

As well as testing the Standard Fog Collector, we want to know if that's really the best shape structure - ie, for the amount of mesh used, does it really collect the most water?

The SFC works well when it's perpendicular to the prevailing wind, but what if the wind changes direction? It misses out on all those other droplets! So we thought we'd try and build a multi-dimensional fog collector too. This construction was more just to practise building since there's no wind in the fog room.

Base and trunk with mesh sewn into centre supports.

Here's the "Tree FC' with its feet and top branches attached. We used slotted angles and Dexium diagonal struts with lots of nuts and bolts holding it together.

The completed Tree FC! All the branches are attached securely, mesh has been attached with cable ties and a quartered 90mm PVC pipe forms the trough for each branch, tied on with fishing line. We're keeping in mind that this design, while probably capable of catching water from more directions, is pretty fiddly to build so might not be appropriate on a large scale...anyway we'll see how it goes!

How to take over your uni's fog room!

The final set up with collection buckets.

Mesh Tests

With just over a week till we head off to Peru, we thought we'd update you on our experiments so far. Pictured above is our first go at building a 'Standard Fog Collector' just before we put it inside the fog room. It's built out of aluminium square hollow sections, half a pvc pipe for the trough and mesh (from Reverse Garbage) stretched over a clothesline cable. The nuts are attached with fishing line to provide some drop-points for the water droplets.

We're trying to determine the best mesh for the job, so we've sewn different meshes to coat-hanger frames (pictured above) and hung inside the fog room to see which is most efficient (ie best at catching and dripping water droplets). Once we've determined the best one, we'll take the sample to Lima and try and use equivalent locally available mesh. 

Each sample has a 500 mL beaker underneath it, plus a control beaker just in front of it to see how much water is collected just by being in the fog room. We've also got a control PVC trough to compare with the one on the SFC.

What's the story?

Bringing Fog Harvesting technology to the shanty towns of Lima, Peru

Description

1. Thousands of families in the shanty towns of Lima are without a secure water source. They are not connected to the town's supply, and every fortnight have to buy water that is trucked in and sold at exorbitant prices.

2. Lima is a very foggy place. Especially in July to November, when a dense fog is blown across the city from the cold Pacific Ocean and sits over the city. But it never really rains - annual precipitation is less than 15mm per year.

3. Fog Harvesting is already being used successfully in wealthy places in Lima. It involves making a massive screen of shade-cloth mesh (8m x16m) and setting it up on a foggy hill. When the wind blows, little droplets of water are trapped on the mesh. These droplets get bigger and heavier and trickle down the mesh into a trough, where they are directed into a storage tank- providing a water source! Fog collectors can collect around 20 Litres per day per square metre of mesh.

So putting these three factors together, we've got one pretty exciting and innovative humanitarian engineering project!

Help support two Civil Engineering students who are spending their year working out the best way to make Fog Harvesting affordable for shanty towns, and are travelling to Lima in July to make it happen!