Optimization of biomass growth for a novel quadruple renewable geothermal/hydro/biomass/solar hybrid system

Abstract In this study, a novel hybrid system was designed and constructed encompassing a biomass culture medium (BCM), ground source heat pump (GSHP), concentrated solar collector (CSC), active solar distiller (ASD), and bio-oil/biodiesel reactor (BBR). The freshwater was supplied by a combination of ASD/BCM systems to maintain the salinity level. A GSHP system was also employed to control the BCM temperature. Saltwater was introduced to the ASD after cultivation for salinity control of the BCM. Various growth temperature, salinity levels, and CO2 injection were tested for the cultivation of Nannochloropsis oculata to reach maximum biomass production of 3.17 × 106 ± 0.50 × 105 cells/mL on the 8th day. The cellular concentration of microalgae was measured by image processing which can precisely (R2 = 0.88) assess the concentration by imaging the cultured samples. Finally, the efficiency of biofuel-to-biodiesel conversion of the BBR section was studied in terms of time, catalyst concentration, and temperature, which was obtained 80.4%.