PARAMETRIC DESIGN STUDY OF A PROPOSED PHOTOBIOREACTOR-INTEGRATED VERTICAL LOUVER SYSTEM FOR ENERGY-EFFICIENT BUILDINGS

Abstract

In recent years, researchers have been actively attempting to integrate biological materials into static building envelope systems. One promising approach is the integration of flat panel photobioreactors into building envelope systems and the BIQ (Bio-Intelligent Quotient) house is the state-of-the-art case building; however, the additional costs for glazing systems to contain photobioreactors, complexity of controlling cultures for microalgae growth, and difficulty of providing indoor environmental quality have kept flat panel photobioreactor systems from being applied widely. If we are able to bring about pleasant physical comforts for occupants through the use of shading devices capable of functioning as the photobioreactors, we can not only grow microalgae but also use less operational energy input to provide better IEQ for occupants. To this end, this study has explored a way to optimize the physical and functional properties of photobioreactor (for Chlorella sp.)-integrated shading devices (specifically vertical louvers). To find the optimal shape for static vertical louvers to be positioned on the west-facing facade, parametric design studies were conducted. To find the optimal vertical louver geometry among numerous alternatives, computer simulations were conducted in terms of three performance criteria (thermal balance by solar radiation, Daylight Autonomy, and microalgae growth rate) and an optimal option was found with the genetic algorithm optimization solver. To ensure reliability of the computer simulation (including numerical model) results, a series of experiments was conducted under the analogous climatic conditions; the computer simulation results were validated with the experimental data. When it comes to hourly indoor illuminance performance, the error between experimental data and computer simulation results was within a range of 5–20%; for average microalgae growth rate, the error was up to 19.9%. Despite the relatively high error between the simulation results and measurements, considering ever-changing light intensity conditions in our measurement compared to that of the computer simulation, it was justifiable to utilize the computer simulation results for the current parametric design study. Finally, the biofuel energy production from the proposed static envelope system was estimated to be 16.5 kWh/m2yr, which is smaller than the state-of-the-art annual biofuel energy production (30.0 kWh/m2yr) from the BIQ house. Nevertheless, the results are promising, given that we used the worst cultivation conditions for the microalgae in the current study.