Improving pH control and carbon dioxide utilisation efficiency in microalgae cultivation systems with the use of a Proportional-integral + dead-zone control strategy
The advanced control strategy significantly improved pH control of the system.
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An approximate 60% reduction in CO2 associated costs was recorded.
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CO2 utilisation efficiency was improved without any adverse effect on productivity.
Abstract
This study investigated the use of an innovative Proportional Integral (PI) + dead-zone control strategy to improve pH control and to overcome the negative environmental impact associated with the currently employed on/off pH control schemes for microalgae cultivation. Scenedesmus sp. grown in anaerobically digested abattoir effluent (ADAE) was used in this study to evaluate the effectiveness of the alternative/advanced control strategy with respect to the on/off control strategy. Results obtained showed that the PI+dead-zone control strategy significantly improved the regulation of the pH level in the pond as evident by noteworthy reductions of key controller performance indicators with respect to the on/off control strategy. Additionally, the advanced control scheme was able to reduce the CO2 usage by a remarkable 59.21% (highest recorded in related literature), resulting in a reduction in CO2 associated costs (approximately 60%) and most importantly, reduction in the amount of greenhouse gas lost to the atmosphere.
