fuel cells for oxygen control inside an algal photobioreactor system for future hybrid life support systems
- Paper number
IAC-18,A1,7,5,x46784
- Author
Mr. Emil Nathanson, Germany, University of Stuttgart
- Coauthor
Mr. Harald Helisch, Germany, University of Stuttgart
- Year
2018
- Abstract
Future human space exploration missions require reliable and self-sustaining space systems. Advanced life support systems (LSS) will be key elements of those systems. Since physico-chemical LSS cannot produce food, biological processes are needed. A logical intermediate step is the development of hybrid LSS, combining both physico-chemical and biological processes. The cultivation of edible microalgae in a photobioreactor (PBR) is a feasible approach. At the Institute of Space Systems of the University of Stuttgart a PBR system for in-situ oxygen ($O_2$) and biomass production in space is currently being developed. Its key features are a lighted cultivation chamber, automated sensor measurements as well as periodic nutrient supply and biomass harvesting. $O_2$ is both a useful by-product (from a LSS perspective) and a putative toxic substance to the algae, if not extracted from their closed habitat. Consequently, a PBR requires the separation of $O_2$ from the water-based medium wherein the microalgae are cultivated. Phase separation can be achieved by a $\mu g$ capable vortex separator, which was already tested during parabolic flights. A PBR gas phase preferably comprises high carbon dioxide ($CO_2$) and low $O_2$ concentration, which makes it incompatible with the cabin atmosphere. The challenge is therefore to realize either a concentrated $O_2$ extraction from the PBR system or an $O_2$ reduction inherent to the system. A reasonable $O_2$ reduction should be based on oxidation reactions (e.g. a fuel cell reaction), which release useful products like $CO_2$ or $H_2O$. This paper highlights the development and testing of a breadboard including an algae driven PBR with a closed gas phase, which is looped trough a polymer-electrolyte fuel cell (PEFC). The fuel cell operation conditions have to comply with PBR system conditions, being ambient temperature and pressure as well as low $O_2$ concentrations. The primary objective is therefore to investigate the PEFC performance under these suboptimal conditions. Of course, also the algae are examined and their performance is compared to the experiments without a PEFC in the loop. After a brief description of the breadboard setup, this paper focuses on the presentation of experimental data. The results are evaluated from a PBR system perspective. Finally, a system development strategy is derived including upscaling of the system.
- Abstract document
- Manuscript document
(absent)