Can solar power be used to help the problem of worldwide water scarcity?

Presentations by Karen Stummeyer and Toru Kannari in an IDA session considering Energy Sources, Use and Efficiency are compared and contrasted to conversations I’ve had with practitioners in the exhibition hall…

First, we have a geographical coincidence and advantage for solar desalination: the world’s sunniest places tend to be coincident with areas of greatest water scarcity.

The energy requirements for desalination are typically >50% of conventional production costs and so prohibitive to places that cannot afford these energy costs, have poorly developed energy infrastructure (e.g. remote communities) or where the ‘value-added’ to water and the customers ability to pay for the energy-water needs are minimal (e.g. large parts of the lesser industrialised world… coincidentally the regions in greatest need of water).

Stummeyer asks, ‘can solar powered desalination provide a sustainable solution?’

Presently solar desalination is in its infancy, there is a ‘steep learning curve’ and costs don’t appear to have the competitive edge for most applications. Energy storage is an issue: The presenters note that most large scale desalination facilities work best when they run continuously, solar radiation by contrast is subject to daily and seasonal variation, so we must look to storing energy if we don’t sell the energy directly to a grid and buy it back, integrating with conventional, hybridisation. Talk of ‘solar multiples’.

Kannari’s examples include Concentrated Solar Collectors of which there are several configurations (parabolic reflectors, towers, solar toughs). Solar energy is used to heat a medium such as oil to close to 400 degrees C of which an ‘excess’ can be stored (and drawn, still hot at night). The heat can be used directly for distillation of the saltwater or indirectly generating electrical power for pumps and RO systems. (These systems can also be backed-up with conventional energy if required.)

At face value, the environmental concerns about energy needs are minimised, but that does not mean that the water is necessarily any cheaper or that there is no significant impact on the environment. Stummeyer noted that the physical footprint of solar arrays may be high, and initial investment costs and subsequent repayment costs may be higher than conventional systems. Effective planning and optimisation of the design is also noted as important for cost and environmental minimisation, for example, Stummeyer observed that inland locations may have greater irradiance than coastal locations but are further from a seawater source so that additional pumping (and so more energy) is required.

In many aspects the issues considered with solar (large-scale, small-scale; on-grid, off-grid; energy storage; environmental concerns) are very similar to those concerning wind – see my IDA Portofino notes from Florien Bollen’s presentation for example.

I chatted with the representatives from General Electric on their trade stand. I said that I’d seen GE’s big signs around Perth advertising wind power solutions. Why are we not seeing more solar powered desalination plants? It will happen, incrementally and possibly in combination with other energy feeds. I’m told that a new breed of solar PV isn’t far away – same size, half the price, twice the output? Could this be a catalyst for low-cost desalination to address water scarcity issues?

Solar desalination can be much simpler. I chatted with F Cubed Australia Pty Ltd. They make a simple aluminium framed solar water processor – an evaporation still. For $400 and with very little electrical requirement up to 15 litres of freshwater can be produced from a panel approximately 3m squared. I’m reminded that the application of technology must be appropriate, affordable and adaptable to the environment and water needs.