Ben Cooper @ Living Solar Panels - UCSC

  The goal of this project is to create a reliable, accurate, and affordable Photosynthetically Active Radiation (PAR) sensor that utilizes a pre-existing IoT framework to automatically upload data at a tunable frequency to support the ongoing efforts of the Living Solar Panels Lab. The device must also be easily reproducable at a large scale to allow maximum scalability and flexibility for current and future experiments.

  Reducing harmful emissions brought about by the fossil fuel industry is one key step in mitigating the current climate crisis. However, proposed renewable energy solutions such as solar and wind energy rely heavily on the extraction, refinement, and processing of rare earth minerals such as cobalt, lithium, and silicon that bring about a plethora of environmental and humanitarian health crises, such as the ongoing case of child slave mines in the DRC (Kelly, 2019).

  Living Solar Panels aims to provide a carbon-negative and biodiversity-friendly method of power generation through the utilization of the electrical potential that naturally develops across a cactus stem as a consequence of the Crassulacean Acid Metabolism (CAM) photosynthetic pathway. Plants that undergo CAM photosynthesis uptake carbon dioxide (CO2) during the night, store that CO2 in the form of malic acid, and during the day, break down the acid to release the CO2 for use in photosynthesis. Because cactus stems are opaque, light cannot penetrate the stem, thus each cactus side photosynthesizes independently of one another (Gibson and Nobel, 1986). This then allows the malic acid to be broken down at a faster rate on the side intercepting the most light, raising the pH, just as conversely the side in the shade, due to breaking down the acid slower, maintains a more acidic pH. This creates a concentration difference across the cactus stem, resulting in an electrochemical gradient that cases charged hydrogen ions (H+) to move across the stem (Nobel, 2020). This difference in concentration, similar to the underlying process of how batteries work, creates a potential difference that can then be utilized as a source of truly renewable power.

  Photosynthetically Active Radiation (PAR) refers to the portion of the electromagnetic spectrum that is essential for photosynthesis in plants and other photosynthetic organisms. It represents the range of wavelengths of light that are absorbed by chlorophyll and other pigments involved in the photosynthetic process. PAR is primarily composed of visible light wavelengths, which range from approximately 400 to 700 nanometers (nm). The intensity and duration of exposure to PAR influence photosynthetic rates, and consequently, affect the concentration of malic acid present on either side of the cactus. Thus, the greater the difference of PAR on either side of the cactus, the greater the concentration difference, and in turn the potential difference across either side of the cactus.

  With a cost of approximately