Combined Water and Power (CWP): saving water and carbon
CWP is a development project and can be initiated now.
In responding to the current and future demands for water within a city such as Melbourne we are already witnessing a change of paradigm about the engineering of water systems. Strategies to reduce demand, by technology and behaviour change, are complemented by new approaches to supply based on a distributed systems approach. This recognises that fresh-water is a distributed resource and that there is a significant energy cost to moving water around. The new distributed system approach encompasses greater reuse of waste water, but treatment of waste streams also has an energy cost. In the context of action on global warming any expansion of the water supply that adds to CO2 production creates a problem.
A similar shift to distributed systems is already evident in bio-energy and renewable (or low-carbon) electricity supply. Energy production is dispersed and, in the case of electricity, ‘the grid’ is becoming a load-sharing system, through which excess supply (above the demands of local consumption) is delivered to where it is needed. The potential for grid-connected micro-generation of electricity from renewable or low-carbon sources is widely recognised as a significant element in a future sustainable energy system. In such systems combined heat and power (CHP) usually play a significant part. A fuel is used to generate electricity (to be fed into the grid) and the heat from that generation is utilised locally, for building or residential communities. In Australia this growth of CHP has been limited by the lack of demand for heat.
The idea of CWP however recognises the potential to utilise heat from a CHP system to clean local supplies of waste water via distillation. Such systems could be both efficient in energy terms and in terms of CO2 production. For most of Melbourne an available (low greenhouse impact) fuel is gas. The CWP system under development (dubbed the Blue Box) is small enough to be transported to waste water sites. It is a device that takes ‘gas and waste water IN’ and gives electricity and clean water OUT.
Constructing a pilot unit should not be difficult as it would combine established technologies – a simple example of the idea of recombinant innovation . A network of Blue Box’s could be efficiently serviced in the way that distributed small-scale CHP units are organised in countries such as Finland, through on-line sensors reporting operational data to a central service agency.
A distillation CWP unit could also use biomass to deliver a carbon neutral source of electricity and pure water.
The draft paper on Combined Water and Power is available for download from our library.
- Anthony Kitchener (SVW Consulting Engineering and Environmental business consultant)
- Dr Michael Brear (Senior Lecturer in the Department of Mechanical and Manufacturing Engineering at the University of Melbourne)