Productivity improvement of microalgal biomass in open raceway pond through temperature control

Abstract

Extensive research has been being made to find alternatives to fossil fuels due to environmental problems induced by the consumption of fossil fuels. Microalgae biomass is a renewable energy source which is one of such alternatives, which has simple growth mechanism through photosynthesis and the advantages of high growth rate and yield per unit area. However, there is a problem of high production cost, which is a major hurdle in replacing the existing fuel. One of the main factors affecting the production cost is the cultivation cost. Among the various culturing methods, open raceway pond, which is the oldest and simplest method, is known to be most suitable for mass culture because it has a low operation cost and is easy to scale up. However, as the culture is exposed to the outside, the variation in productivity is extremely severe, and thus a culture concentration is usually maintained at a low level. Therefore, in this study, raceway pond with a heat exchanger is introduced as a strategy to improve the productivity by adding or removing heat from the pond. The impact of integrating heat exchanger evaluated in terms of the algal cell concentration and the production cost. In addition, the optimal operating conditions that maximize the economic efficiency of the culture system are identified by solving the optimization problem using the dilution rate and flow rate of the heat exchanger as decision variables. This study aims to verify the expected outcome of the integration of algal pond and heat exchanger.