Thermodynamic Performance of a High Efficient Power Plant Based on Faecal Biomass Gasification, Solid Oxide Fuel Cells and Micro Steam Turbine

Affordable sanitation around the world with the recovery of valuable energy and clean water from faecal biomass in an off-grid system is a challenge. An energy neutral sanitation  system  concept  based on plasma gasification and solid oxide fuel cell (SOFC) was presented by TU Delft {Mings et al.}. The system is further optimised and  novel small scale CHP toilet system concept  has been developed which can generate power very efficiently and produce clean water. Pre-dryed faecal biomass, is fed to the integrated system. The system combines a dryer, a plasma gasifier, and a gas cleaning unit with an ambient pressure stack and a micro steam turbine (MST). The gasifier uses the heat supplied from the combustion of SOFC depleted fuel. With this concept syngas with high heating value can be produced, which can be efficiently converted in a SOFC system. This is reflected by the net electrical efficiency of the integrated system configuration  of the order of 50%. Additional power is produced combining it with an MST and an efficiency increase of the order of 5% is achieved. Variation of the different operating conditions in the system reveals an optimum for the temperature, steam to biomass ratio and oxidant to fuel ratio in the gasifier. Furthermore, the SOFC operating temperature influences the system performance and self-sustainability. As a result, from a thermodynamic point of view it is demonstrated that a high efficiency power generation through faecal biomass can be realized.

Ming Liu, T. Woudstra, E.J.O. Promes, S.Y.G. Restrepo, P.V. Aravind. System development and self-sustainability analysis for upgrading human waste to power.