Economic feasibility study for artificial lighting of microalgal flat-panel photobioreactors.

Lightning belongs among critical process parameters that significantly affect growth and microalgal yield in photobioreactors. Sunshine or artificial lighting is applied to irradiate photobioreactors. Nevertheless, sunshine lighting is limited by locality and weather conditions. On the contrary, there is a typical demand for nonstop or 8000 annual working hours for industrial biorefineries using photobioreactors as an economic point of view. Thus the paper scopes to evaluate the fundamental economic feasibility of artificial lightning provided by electric energy from fossil fuels, renewable energy systems, or their mutual combinations. The economic feasibility is discussed concerning local annual sunshine hours for a model 1-ha microalgae cultivation plant. It was found that combined sunlight, solar energy- and electric energy-based artificial lighting has a significant positive effect on the economic behavior of a model biorefinery. The mutual combination of sunshine, solar energy- and electric artificial energy-based light evinces a profit increase of 2.18 for microalgal powder, 3.09 for microalgal lipids and 4.11 for microalga carotenoids production technologies all compared only to sun lighted photobioreactors. Nevertheless, capital investments in artificial lightings, solar systems, or photobioreactors, and high operating expenses represent the dominant risk factors of the discussed microalgal biorefinery. Developing cheap and reliable artificial lighting systems, solar and energy storage systems, and improving process characteristics of microalgal cultivation (process stability, high concentrated suspension in thin layer photobioreactors avoiding biofilm formation) were identified as the essential research needs and challenges to improve the economic feasibility of artificially lighted microalgal biorefinery. [ABSTRACT FROM AUTHOR]