Monday, March 13, 2006

Desalination in Spain

Continued from Page 6

Canary Islands Renewable Energy

Researching methods to reduce energy use has long been a focus of the Canary Islands Institute of Technology (ITC), a research facility supported by the regional government of the Canary Islands. And scientists there are taking this one step further: they are investigating how to produce freshwater from saltwater without using fossil fuels at all.

“Here, we have a great deal of sun, wind, and seawater. It is an excellent place to develop systems,” said Gonzalo Piernavieja, ITC energy and water director. “It is also an ideal place to simulate conditions in many developing countries.”

The engineering involved in using renewable energy to power a desalination plant can be relatively simple: solar or wind generators can be hooked up to an existing utility grid, which then offsets the power demands of the desalination plant.

The challenge, however, in coupling desalination directly with renewable energy such as solar or wind power lies in the variability of renewable energy. The membranes used in reverse osmosis need to be kept wet, and the systems that make up a desalination plant have been developed to handle a steady stream of water. Solar energy is plentiful when the sun shines and wind power only when the wind blows.

Researchers in the Canary Islands have spent the past decade developing stand-alone small plants that could provide water for approximately 100 to 300 families, about the size of a small village in a developing country. ITC projects are also carried out in conjunction with other international research institutes or companies.

On one Canary Island test site, photo-voltaic panels are hooked up to a battery, which feeds a steady supply of electricity to a small desalination plant. “But batteries aren’t great because you have to replace them after, say, five or 10 years, and then you have to dispose of them as well,” says Piernavieja. “It’s better to develop a system that needs no batteries in the first place.”

Other solutions tested at the Canary Islands site make use of wind power. In one, a small wind-energy converter powers a seawater RO plant designed to operate even with the stops and starts of wind power. In another, a small wind farm creates a small stand-alone electricity grid that then feeds electricity to the desalination plant.

The Canary island of El Hierro, which has 10,000 inhabitants, hopes to model the future of island living. ITC is involved in a project there in which eventually 100 percent of the island’s energy needs will be served by renewable energy; that energy, through a grid, will also power desalination plants that supply all the island’s drinking water and irrigation needs.

The ITC research group is one of only a handful focusing on developing and testing plants in which wind turbines directly power the desalination process without going through any grid.

Though all of these systems could be used in industrialized countries, the main goal of the ITC is to develop plants that could theoretically supply water to even a fraction of the billion people around the world in need of clean drinking water. “Many of these people live in areas that have abundant renewable energy resources and yet no electricity grid, and they may never be connected to a grid. This is the philosophy behind our research,” says Piernavieja.

ITC research on coupling desalination with renewable energy is already being tested in the world outside the Canary Islands. The ITC has placed four small desalination plants among a population of African fishermen living within the boundaries of a national park called Banc D’Arguin in Mauritania. In 2006, the diesel-run desalination plants are being converted to run using a hybrid of wind, solar, and diesel power. Wind–solar RO plants are being installed in Morocco, and a solar plant is destined for Tunisia.

Still, these types of applications have many hurdles to overcome. Says Medina, “These types of systems need maintenance. If you install such plants in such a remote place, and if the plants break down, it could take months until someone can be sent there to fix them.”

There are applications for these types of stand-alone plants in industrialized countries as well. The ITC is in discussion with the engineering company MTorres, based in northern Spain, about combining the technology developed in the Canary Islands with the ones MTorres is developing: offshore desalination plants powered by wind. MTorres, with extensive experience in wind power, has plans to connect the two fields.