A Framework for Comparing the Viability of Different Desalination Approaches

Key Points 

Most renewable powered desalination schemes are hybrids that displace fossil fuel power when renewable power is available. Their economic viability depends only on whether the renewable power source can generate electricity more cheaply than the fuels that it displaces. The framework used here by KAPSARC compares standalone plants that are powered only by renewable energy and therefore incorporate storage, either of input energy to allow the plant to run full time or of produced water to level out the production of an oversized plant. The commerciality of such approaches is a function of the relative costs of three elements: 

• energy storage (electricity or heat); 
• the cost of standby desalination capacity (including treated water storage); or 
• the relative costs of renewable and conventional energy. Our research shows that, with the present state of technology, membrane plants are more cost-effective than thermal plants. It is also more cost-effective to oversize the desalination plant and store water on the back end than to store electric power on the front end. The best current configurations are only competitive if the opportunity cost of the avoided fuel consumption is more than $60/barrel of oil equivalent (BOE).