Organic Rankine cycle integrated with hydrate-based desalination for a sustainable energy–water nexus system

Abstract

Clathrate hydrate-based desalination (HyDesal) is a promising desalination technology but it is energy intensive. Developing strategies to reduce the high energy consumption of HyDesal process is necessary for its industrial application. The need for refrigeration requirement for the operation of HyDesal can be offset by LNG cold exergy to reduce its energy consumption. However, the LNG cold exergy utilization efficiency is low due to the large temperature difference between LNG and seawater and hydrate former. In this work, we propose a sustainable process that integrates HyDesal and organic Rankine cycle by utilizing LNG cold exergy to generate fresh water and electricity simultaneously. This integrated process was optimized by adopting particle swarm optimization algorithm to achieve maximal power and fresh water generation. Further, an economic analysis was performed to compare the economic performance of the proposed system and the base case. The results showed that the proposed process could achieve zero specific energy consumption for desalination and generate extra power. The largest fresh water production and power generation of 165.3 tonne/h and 3480 kW were achieved by adopting cyclopentane as hydrate former and mixed working fluid in organic Rankine cycle based on 100 tonne/h of LNG flowrate. The lowest levelized cost of water of the proposed process was 1.946 $/m3, which was 21.05% lower than that of the base case. Thus, the proposed sustainable process can strengthen the energy–water nexus and reduce the greenhouse gas emission by utilizing LNG cold exergy.