Activated carbon–carbon dioxide based two stage adsorption compression Brayton cycle power generation

Enhancement of energy delivery of a carbon dioxide (CO₂) Brayton cycle without compression work liability is achievable using low grade heat for thermal compression. The limitation of the expansion ratios of a single stage adsorption thermal compression is obviated by opting for pressure build up in two stages. Despite the use of a large number of adsorbers, it is shown that, specific work output can be augmented substantially with no undue penalty on the overall cycle efficiency albeit with a marginal shortfall in work output per unit mass of adsorbent. These features are elucidated through an activated carbon based thermal compression of CO₂ yet limiting high side pressures to 80 bar and the principal heat source at a temperature equal to or less than 300 °C in tandem with another low grade source at 100 °C for thermal compression. The net outcome is a substantial reduction in the size of the power block and heat exchangers resulting from enhancement of the expansion ratio and reduction in the mass flow rate in the circuit.