Analysis of integrated co-generative schemes including MSF, RO and power generating systems (present value of expenses and “levelised” cost of water)

Abstract

The proposed study provides an analysis of an integrated co-generative scheme including the following subsystems: (1) gas turbine and unfired heat recovery steam generator, (2) auxiliary boiler, (3) multistage flash (MSF) and (4) reverse osmosis (RO). It contains a comparison of the integrated system with the reference scheme. A comparison of alternatives was based on the present values (PV) of expenses over the economic life of capital and “levelized” cost of water. The analysis was based on the following assumptions: (1) depreciation period is equal to the period of bank credit; (2) zero year is the base year of the project; (3) the discount factor is dependent upon the nominal interest rate and retail price index, (4) cost of primary fuel ranges from 1 to 4 $/GJ, (5) assumed carbon tax varies from 0 to $50 per tonne of emitted carbon. Based upon calculated results, the study confirmed the statement that RO can successfully coexist with MSF. Hybridisation of thermally- and electrically-driven processes can provide the following advantages: (1) a decrease of PV of expenses, (2) decrease of specific capital and energy consumption; (3) decrease of the level of carbon tax (owing to a drop of allocated CO 2 emissions); (4) decrease of “levelized” cost of water. Incorporation of RO into existing co-generative systems decreases its sensitivity and, in turn, commercial risk of the system to fluctuation of the following factors: (1) nominal interest rate (2) cost of primary fuel and (3) rate of carbon tax. The array of calculated data and projections is attached.