Impact of Dropwise Condensation on the Biomass Production Rate in Covered Raceway Ponds

Energies

Jack Hoeniges¹  Laurent Pilon¹  Keyong Zhu²  Jeremy Pruvost³  Jack Legrand³  El-khider Si-Ahmed³ 

[1] Mechanical and Aerospace Engineering Department, Henry Samueli School of Engineering and Applied Science, University of California, Los Angeles, CA 90095, USA;School of Aeronautical Science and Engineering, Beihang University, Beijing 100191, China;Université de Nantes, Oniris, CNRS, GEPEA, UMR 6144, F-44600 Saint-Nazaire, France;

关键词: light transfer;    photobioreactor;    biofuel;    bioprocess engineering;    design;    modeling;   

DOI  :  10.3390/en14020268

来源: DOAJ

【 摘 要 】

This study investigates the effect of condensed water droplets on the areal biomass productivity of outdoor culture systems with a free surface, protected by a transparent window or cover to prevent contamination and to control the growth conditions. Under solar radiation, evaporation from the culture causes droplets to condense on the interior surface of the cover. To quantify the effect of droplets on the system’s performance, the bidirectional transmittance of a droplet-covered window was predicted using the Monte Carlo ray-tracing method. It was combined with a growth kinetics model of Chlorella vulgaris to predict the temporal evolution of the biomass concentration on 21 June and 23 September in Los Angeles, CA. A droplet contact angle of 30${}^{\circ }$ or 90${}^{\circ }$ and a surface area coverage of 50% or 90% were considered. Light scattering by the condensed droplets changed the direction of the incident sunlight while reducing the amount of light reaching the culture by up to 37%. The combined effect decreased the daily areal biomass productivity with increasing droplet contact angle and surface area coverage by as much as 18%. Furthermore, the areal biomass productivity of the system was found to scale with the ratio $X_0/a$ of the initial biomass concentration $X_0$ and the specific illuminated area a, as previously established for different photobioreactor geometries, but even in the presence of droplets. Finally, for a given day of the year, the optical thickness of the culture that yielded the maximum productivity was independent of the window condition. Thus, the design and operation of such a system should focus on maintaining a small droplet contact angle and surface area coverage and an optimum optical thickness to maximize productivity.

【 授权许可】

Unknown