x Abu Dhabi, UAESunday 23 July 2017

UAE summit to discuss if desalination can be made less energy-intensive

Can desalination be made less energy-intensive? This question will be one of the most important issues discussed in the capital next week when experts gather for the International Water Summit.

Can desalination be made less energy-intensive? This question will be one of the most important issues discussed in the capital next week when experts gather for the International Water Summit.

Leading desalination experts from across the world will gather at the Capital Gate Hyatt on the sidelines of the summit at Adnec for a special session of the International Desalination Association's (IDA) Energy Task Force on January 15 to discuss how to lower the process's energy demand by a fifth over the next two years.

The question is of particular importance for the UAE, which relies on desalination for the vast majority of its potable water. The Arabian Gulf region produces nearly half of the world's desalinated water.

According to Dr Corrado Sommariva, the president of IDA, making desalination more energy efficient is not only possible but necessary. "The energy footprint is the most important aspect needed to make desalination technology ... sustainable in the short and long-term," he said.

"In general, energy consumption has been greatly reduced over the past decades through a gradual introduction of innovative solutions and the task force is building on this accomplishment."

Desalination, a process in which the salts dissolved in seawater are removed to produce potable water, is energy-intensive. This is why the task force set a challenge to the industry to lower energy requirements by 20 per cent by 2015.

"The purpose of this discussion is to make people aware of our commitment," said Dr Sommariva, explaining that utility companies that own and operate desalination plants, technology providers, contractors and policymakers had been invited to participate.

The simplest way to cut the energy used in desalination was to make existing facilities more efficient, Dr Sommariva said.

"A large number of the plants in the country installed in the 1980s and 1990s are still in operation and have a very low performance ratio," he said.

In the UAE, desalination is often coupled with energy production. When natural gas is burned to produce electricity, the waste heat produced is captured and used to heat seawater for the desalination process. Most plants use a process called multi-stage flash distillation (MSF) in which water is pressurised into steam and the condensation collected.

A plant that has a low performance ratio needs more steam to produce water, and is thus less energy efficient but Dr Sommariva said there were a number of ways to increase efficiency.

For example, steam could be used at lower pressures, or electrical pumps, very often oversized by designers, could be downsized. "Most of these interventions are not rocket science," he said.

A bolder approach could be to opt for more efficient technologies, which are already well-established. While the UAE has almost half a century of experience operating MSF plants, it could generate substantial energy savings by opting for another thermal technology, called multi-effect distillation, which has "intrinsically lower power consumption". Reverse osmosis, which does not heat seawater but rather passes it through a series of membranes, is another alternative that has already proven its reliability, he said.

The shift is already happening in Abu Dhabi where, for instance, the Al Mirfa Power Company is replacing three of its MSF units, installed in 1996, with reverse osmosis units. Dr Sommariva estimated the move would save between 35 and 40 kilowatt hours of electricity for every cubic metre of water produced.

While these were examples of already well-proven technologies, Dr Sommariva said decision-makers could also think of how to encourage "the solutions of tomorrow" - the adoption of newer, more efficient technologies that could challenge the state-of-the-art technology on large-scale use.

One promising technology is low-temperature distillation, which also relies on thermal processes to produce water, but requires lower temperatures and can be readily coupled with renewable energy sources. Membrane distillation and forward osmosis are also promising in this respect.

"Clearly the entry barrier for these technologies is high and therefore it is essential that the industry stakeholders bridge the gap between the research and development stage and commercialisation," Dr Sommariva said.

vtodorova@thenational.ae