Prototyping a Solar Thermal Collector using Aluminium Cans

IMG_20160718_181446 IMG_20160718_181322

The following prototype is the first attempt at building a Solar Thermal Collector using a waste product such as aluminium cans. The concept is simple: the sun’s radiation heats up drilled cans painted black, heating the air inside, while a fan moves the hot air to the intended destination. The cans are drilled in the bottom and the top, and stacked on top of each other. As the hot air naturally rises, it is removed by the fan so that the cooler air enters the panel through openings at the bottom.

Despite this being a very crude first attempt (the acrylic glass is barely transparent, it is not the target thickness, it has cracks and it is not sealed in the edges), we were able to output air with a temperature of 38ºC in a spring day with less than 20ºC of ambient temperature earlier this year.  We are now working on optimizing the design for two goals:

  • Find easier materials to source and work with, and write the instructions for this design;
  • Experiment combining this thermal collector with a heat engine, so that during the summer the heat of the sun can be used for mechanical work or for electricity generation.


Experimenting with Portable & Passive Hydroponics

I have been experimenting with portable and passive solutions for hydroponic systems. The objective was to have a system as simple and maintenance free as possible. Two types of packages were tested: Tetra-Pak or similar and PET bottles. The Tetra-Pak or similar were ideal since they protected the nutrient solution from light. While growth was fast, some fungal activity was detected in lettuce leaves, and some of the packages started leaking from the bottom after some weeks of use.


The PET bottles are behaving surprisingly well. I was unsure if their transparency would affect plant growth since it’s usually believed that roots should be protected from light. But the plants have been experiencing some growth, despite light exposure. As expected, algae growth can be observed in the walls of the PET exposed to the nutrient rich solution. Whether they will affect the growth of the target plant or not remains to be seen.

Some of the challenges that need to be addressed before creating an instruction for this technology include: finding the best material for container (preventing leaks and light), and incorporating these vertically without danger of spillage.

OikoSol’s Vermicomposter in action

Here you can see a picture of OikoSol’s vermicomposter in action. It has been working without problem, managing to consume around 1 Kg of organic waste per 2 weeks (approximate figure), as well as ~200mL of vermicompost tea per week. It was observed that other organisms have populated the vermicomposter, including mostly thrips and compost mites. But these have been contained to the compost as it is always closed. There have been no issues with smell, which is a good result considering this one is positioned inside a kitchen.