Comparison of the carbon footprints of combined heat and power (CHP) systems and boiler/grid for supplying process plant steam and electricity

This paper focusses on comparing carbon footprints of supplying process plant steam and electricity using boiler/grid, gas turbine and steam turbine CHP systems, and grid heat & power (grid-HP), and investigating the effect of key parameters on the carbon footprints. These parameters include fuel type, grid carbon intensity, plant heat to electric power ratio, plant steam pressure, and operational parameters particular to the CHP systems. The analysis highlights the critical importance of the grid carbon intensity. There exist grid carbon intensity transition values, whereby below a certain value the grid-HP provides the lowest footprint, and above a certain value one of the CHP systems provides the lowest footprint. These transition values are independent of the plant heat to electricity ratio. However, they are influenced by other factors outlined in the paper. Consequently, many fossil fuel boiler/grid and CHP systems may become obsolete due to decreasing grid carbon intensity.