fresh water/cooling/tidal energy
Dr Paul Dougan
Head of Drilling
CEO - Caribbean
Dr Zara Mohsan
Juan La Cruz
How do you fit 130 litres of water in a single cup?
The answer: fill it with coffee.
Growing coffee beans is a thirsty business, as is growing cotton – 10,000 litres of water in a pair of jeans – and 2,500 litres in the average T-shirt. Avocados, almonds – even bottles of water themselves, are all highly water-intensive enterprises. Agriculture uses about 70% of freshwater across the globe.
Regions that export water-intensive crops are effectively exporting their water, in a trade known as “virtual water” or “invisible water”. Agricultural products are the most obvious trades in virtual water, but vast numbers of manufactured goods also require large quantities of water. When countries and regions with water shortages pour their water into exports, on the surface it can look as if they are making a profit, but in the long term their reliance on diminishing water resources will be damaging.
The planet’s biggest water resource, seawater, is in no danger of running out, making up 97% of Earth’s water. Why not harness it for drinking?
The most basic technology to do so has been in use for nearly as long as fire: distillation, the process of boiling water and catching the steam, condensing it into liquid. In small quantities, this can be done easily, and cleanses water of other impurities as well as salt. But at large scale, such as providing the drinking water needs for a city, the process is fuel-intensive, even using modern methods such as low-pressure vessels to lower the boiling point.
Alternative technologies use electrical currents, which when passed through the water can separate out salt and other minerals, and reverse osmosis, by which saline water is passed at high pressure through membranes that exclude salt and impurities. Both these methods also have high energy requirements, which makes them costly, and adds to global greenhouse gas emissions. Sucking in seawater can also suck in fish and damage coastal ecosystems. Waste from the plants is another issue: the salty residue is usually released back into the sea, but this must be carefully managed because at the concentrations produced it is toxic to marine life.
Energy costs have proved prohibitively high for most countries, so the main users of desalination to date have been among the fuel-rich and arid countries of the Middle East. However, the water crisis has gripped so hard in some areas of the world that some cities see little alternative. Cape Town’s first desalination plant has just started operating, after some severe budget woes. China, Pakistan and India are exploring new desalination plants. If renewable energy can be used to power the plants, this should reduce the impact on climate change.
"Subsurface seawater intakes for water quality improvement, and enhanced economics of freshwater production"
The diagram above shows typical pretreatment process trains for a SWRO plant (a, b, c) with the I AM AQUA simplified system using a subsurface intake (d). A subsurface intake may be any to produce feedwater that can bypass the pretreatment system and flow directly to the cartridge filters.
Well intake system located along a shoreline. This is truly a “beach well” system that promotes direct recharge from the sea and minimizes capture of landward water resources. Minimal flow should come from the shoreline direction to avoid aquifer impacts and entry of poor quality water.
Typical design from a radial collector or Ranney well. The laterals can be designed to extend beneath the seabed to all only vertical recharge through the seabed, precluding landward impacts. Note that the laterals occur on a single plane and many can be installed.
Beach gallery intake system showing the concept of allowing the breaking waves at the shoreline to mechanically clean the face of the filter, reducing the potential for clogging.
Diagram showing angle well intake system. Note that the recharge direction is vertical compared to the typical vertical well intake system and the issue of impacts to coastal aquifers can be avoided