Optimisation of hybrid cane-based combined heat and power-concentrating solar thermal power plants of 30 MW

Abstract

The benchmarking and optimal power extraction from a cane-based combined heat and power (CHP) plant using state-of-the-art processes has been underestimated. This study indicates that the export power potential can be much more than the presently achieved values of 5.8–7.0 MW/1000 tcd (tonnes crushing per day). It can be 11–12 MW/1000 tcd. By integration of cane-based CHP with concentrating solar thermal (CST) – parabolic trough concentrators (PTC) systems of even size, the heat rate (power only) can be decreased from 2984.12 to 2088.89 kcal/kWh and the overall efficiency (power +heat) of 48.59% can be enhanced to 69.41%. The CHP potential of sugar mills will be considerable enhanced to 12 MW/1000 tcd by four elements: (a) integration with solar-concentrating collectors, (b) the use of high-efficiency, high-pressure boilers (>11.0 MPa and 560°C), (c) three-dimensional designed stage optimised steam turbines with high isentropic efficiencies of 92–94+% and (d) minimising in-house steam demand to below 225 kg/t of cane (=9.37 t/h per 1000 tcd) and in-house electric demand to below 22 kWh/t of cane (=0.91 MW/1000 tcd). Auxiliary power must be below 8% of the power export. Matching policy incentives will help in new initiatives and quick take off of new projects. The estimated potential for India for cane-based CHP is around 7 GW without solar systems and is 10 GW for hybrid CST–PTC cane-based systems. This is a zero fossil fuel-consuming technology.

Keywords:

• sugarcane-based CHP
• solar-concentrating collectors
• parabolic trough concentrators
• hybrid solar–bagasse systems
• renewable power potential
• policy initiatives