The project deals with generating energy from living plants. This is possible due to devices called microbial fuel cells that turn chemical energy into electrical. This whole process starts with the plant. The plant produces bio-convertible substrate, such as glucose, during the process of photosynthesis and releases it in the ground through root system. Certain bacteria types present in the soil act as catalysts, meaning they turn this substrate into CO2, protons and electrons. The earlier mentioned devices are capable of harvesting part of this chemical energy, by collecting electrons, and converting it into electrical energy.
The three most important elements for sustaining this process are a number of bacteria, the quantity of roots and the quality of the devices. Providing an anaerobic medium ensures a sufficient number of bacteria. In addition the number of roots is related to plant type, and the quality of the device depends on the distance between the anode and cathode compartment.
In order to find a way to combine these elements in one system, a material investigation was conducted. It investigated the interaction between strings under tension, and balloon air pressure. Process of investigating the behavioral characteristics of these elements, consisted of inflating balloons into different string configurations. In this process, strings showed a tendency to attach to each other at certain points on the balloon’s surfaces.
Material System
Form Finding
The experiment concluded that certain balloon-like volumes could be used to shape underground root systems. In the same way that vertical strings are following balloon surface, roots are following nutrients paths. And hence, this makes the roots denser at soil spots between balloons. Defining these hotspots several levels below the ground could potentially generate more electricity, gained from one square meter of plants. The project is based on the specificity of the Switch Grass plant that has a long and dense root system reaching 2.5 m in depth, thus allowing more levels for harvesting energy. Besides shaping the roots, balloons are collecting water on surface above the ground and conducting it into the soil, ensuring the anaerobic characteristic of it. Furthermore, other type of balloons act as electricity harvesters containing surface as ion-exchange membrane and cathode compartment inside the balloon, that captures electrons from anode compartment in soil.
Quantitatively speaking, 1 square meter of plants in this system could produce electrical energy up to 0.0200kWh a day, meaning it could charge approximately 3 smartphones in a day.
