Taking Desalination to the Next Level
Energy Efficiency Is Key to Tapping the Seas
Jim Rush Oct 12, 2011
Earth: the Blue Planet. Its nickname is derived from the fact that about 70 percent of its surface is covered by water. Yet despite its abundance, water that is readily adaptable for drinking is in short supply. In fact, about 97 percent of all water found on our home planet is saltwater that must be treated before it can be used for consumption, irrigation or industrial processes.
To make matters worse, trends in human population, as well as changes in climate, are placing an increasing demand for freshwater across the globe. A growing global population needs water for consumption, as well as irrigation for food production, while industrialization in emerging areas like China, India and Brazil, among others, is stressing water resources even further. In the United States, a population shift to the Southwest and Southeast means that those arid areas must find new ways of obtaining water.
To address water shortages, utility managers and government leaders are turning to water conservation, water recycling and desalination. Increasingly, desalination is being viewed as a viable alternative, which is not surprising given the abundance of seawater readily available to coastal population centers.
The concept of desalination is certainly not new. Man has been desalting water for centuries using the thermal desalination method – essentially boiling seawater to separate the water and salts, and collecting and condensing the steam. In recent years, advances in membrane filters have led to the process of reverse osmosis (RO) desalination, which involves pumping seawater through ultrafine screens that collect the salts, allowing only fresh water to pass.
The problem with both of these methods has been the intensive amount of energy required. The thermal method requires an abundance of heat energy while RO desalination requires high-pressure pumps to move large amounts of water from the sea and force it through the filters.
The key to expanding the use of desalination has come down to finding a way to reduce the energy required to desalinate water, thus making it an economically viable option. One company, based in San Leandro, Calif., is making cost-effective desalination closer to a reality.
Energy Recovery Inc. was founded in 1992 with the development of a technology that would help recycle energy used in the RO desalination process. The PX Pressure Exchanger (PX) is an energy recovery device that basically recycles pressurized water that does not pass through the RO filters back into the high-pressure loop at 98 percent efficiency, reducing the amount of energy required by 60 percent, Energy Recovery Inc. president and CEO Tom Rooney says.
In addition to maximum energy savings, the PX device has significant economic benefits to desalination plant owners and operators. ERI PX technology offers very high availability and durability. With zero unplanned downtime and a 99.8 percent uptime advantage, facilities can secure their water production and save millions of dollars over the lifetime of a plant. In addition, the unique ceramic (alumina) materials that make up the device are designed to last a lifetime - of no less than 25 years. As a result, the PX technology offers the best economic solution to all stakeholders.
Since developing its product in the 1990s and improving it in the early 2000s, Energy Recovery Inc. went public in 2008. During that time the product has gained a leading position in the marketplace.
“We went from a little-known company with interesting new technology to being by far the most dominant technology in the industry,” said Rooney, who estimates his company has an 75 to 80 percent market share.
Using an energy recovery device allows a plant to operate using much less energy. According to Rooney, an RO plant operating without energy recovery devices would require two and half times more power. The devices, Rooney says, are “making desalination more economical while the demand for water is skyrocketing.”
Demand for desalinated water is high across the globe, from obvious places like the Middle East, the Mediterranean, the Caribbean and the desert Southwest in the United States, but also South America, Asia and even Europe (London opened its first desalination plant in 2010).
The demand for desalinated water is increasing, but the recession that began in 2008 has had an impact on the short-term market. “Following the global economic collapse we saw a massive contraction of desalination plants being built around the world due to a lack of access to capital markets; these plants are very large and expensive to build, in the range of hundreds of millions of dollars,” Rooney said. “We are just now seeing the market come back.”
Desalination in the United States is not as prevalent as it is elsewhere in the world, but there is increasing interest. Tampa Bay Water is operating a 25 mgd plant in Florida, and there are proposals for new facilities on the West Coast.
Desalination plants often face criticism due to their energy footprint, as well as the potential impact on the ecosystem. Getting a plant built can take years to get all the required support and approvals. “What happens is that there is a tremendous amount of pushback to a new plant being built, but once it built and is operating, and clean water is flowing, people realize that there is effectively no downside,” Rooney said. “Then that opens the door for more projects to follow.”
That is the case in California where the proposed 50 mdg desalination plant in Carlsbad, near San Diego, has spent more than a decade getting required approvals. At 50 mgd, it would be the nation’s largest. At stake, perhaps, is the future of desalination in California as there are a reported 20 current desalination proposals for the California coast.
Rooney says Energy Recovery Inc. does about 8 percent of its business in the United States, but he views it as a growth opportunity. “It is likely a gigantic market, but it is still fighting its way through getting the initial projects built,” he said. Opportunities exist not only in California but also in the entire Southwest, Texas and the Southeast, particularly Florida.
That bodes well for Energy Recovery Inc. with its energy-saving devices. “With energy recovery devices you can drop your energy cost by 60 percent in one fell swoop,” Rooney said. “And with the cost of the devices about 1 percent of the total construction cost, it makes it a slam dunk to put these devices in.”
While the company was rooted in the desalination market and has a leading position in it, Rooney recognizes the opportunity to move into new market sectors. “There are many markets that have fluid flows that would benefit from energy recovery devices, including chemical processing, oil and gas, potable water, and mining,” Rooney said.
Jim Rush is editor of UIM.
[NOTE: White papers and uptime savings calculators can be found at www.energyrecovery.com]
An Environmentally Friendly Approach to Desalination
As part of Water Corp.’s and Western Australia’s commitment to promote energy efficiency and reduce greenhouse gas emissions, the Perth seawater reverse osmosis (SWRO) plant is the largest facility of its kind in the world to be powered by renewable energy. The plant buys its power needs from electricity generated by the Emu Downs Wind Farm, located 120 miles north of Perth. The 83 MW wind farm consists of 48 wind turbines and contributes over 272 GWhr per year into the grid, fully offsetting the Perth SWRO Plant’s estimated electrical requirement of 180 GWhr per year. In addition, instruments that continuously monitor plant discharges automatically shut down the process in the event of an exceedance.
The plant, with 12 SWRO trains with a first-pass capacity of 42 million gallons a day (mgd) and six brackish water reverse osmosis (BWRO) trains delivering a final product flow rate of 38 mgd, will have one of the world’s lowest specific energy consumption rates, due in part to the use of Energy Recovery Inc.’s PX Pressure Exchanger energy recovery devices (ERDs). The PX device is an isobaric-chamber ERD that recovers pressure energy from the brine reject stream and delivers it to fresh seawater going to the SWRO membrane feed at a net transfer efficiency of up to 98 percent, making it the world’s most efficient ERD. PX technology saves the Perth SWRO Plant 15.6 MW of energy.
The combination of unheralded environmental protection and monitoring, low specific energy consumption and the use of a renewable energy make the Perth SWRO Plant a world model for providing water in an environmentally sound and sustainable manner, converting wind to fresh water. Water Corp. has demonstrated that a well-planned alliance approach can produce a desalination plant that is environmentally responsible, well designed, and cost effective all at once.
“I sincerely believe that the MDJV (Multiplex Degrémont Joint Venture) Alliance has produced a design that is unmatched and will result in the most sophisticated seawater desalination plant in the world, the Perth Seawater Desalination Plant. It will no doubt be the world’s model desalination plant incorporating some of the most advanced components including the highly efficient – simple to operate – with low maintenance isobaric energy recovery devices from ERI,” said Gary Crisp, Principal Engineer, Desalination, Water Corp. of Western Australia.