Wastewater and Mixed Microbial Consortia: a metastudy analysis of Optimal Microbial Fuel Cell configuration

Microbial Fuel Cells (MFCs) are an area of increasing research for use as an alternative energy source, due to their ability to produce electricity while simultaneously treating organic waste. This meta-study determines the optimal MFC configuration for electricity production, through consideration of the biocatalyst and substrate used. This study focuses primarily on comparing the use of mixed microbial consortia to pure strains of biocatalyst, and the use of waste water in contrast to simple substrates such as; acetate, glucose, and lactate. The use of algae as a substrate, and as a biocatalyst, is also investigated. In this study, only single and dual chamber MFCs are compared, and power density standardised to anode surface area (mW/m2) is used as a metric to facilitate the comparison of different experimental setups. This meta-study shows that dual chamber MFCs, using simple substrates, when catalysed by mixed culture biocatalysts, produce greater power densities, than algae, and complex substrates, with average power densities of 280, 70 and 30 (mW/m2) observed respectively. In single chamber MFC configurations, mixed culture biocatalysts have been observed to yield approximately double the power output of pure culture biocatalysts

Factors Influencing the Thermodynamic Efficiency of Stirling Engines

This meta-study examines the factors which contribute to Stirling engine efficiency. Working fluids should have high specific heat capacity, low viscosity and low density making noble gases the most suitable. Each different working fluid has its own optimum power output at varying pressures and temperatures. The best being Helium at 4.14 MPa and 922K. Dead volume also affects the power output of Stirling engines. Theoretical engines with zero dead volume are ideal but dead volume can occupy over 50% of the engine. Engine configuration also impacts on the efficiency of a Stirling engine. The layout of pistons and cylinders about each other can also have drastic effects on these efficiencies. Currently the most effective engine layout is the ‘gamma’ configuration, which measures 30%-32% efficient. Future research is required to produce a more efficient Stirling engines, based on the factors considered above to determine the viability of these engines as a replacement for coal and fossil fuel powered combustion engines