Thursday, May 06, 2010
Gulf News
Because of the energy intensive nature of desalination plants, the push to power them using solar energy is becoming increasingly important for this region, where the availability of fresh water becomes more and more limited.
"We're embarking on a big desalination industry. In the UAE we started 15 years ago with the Umm al Nar solar desalination plant which then proved to be economically unfeasible. But as the technology improves, the cost is going down and the efficiency is increasing," says Mohammad Dawoud, Water Resources Department manager at the Environment Agency-Abu Dhabi (EAD).
Desalination plants, which convert salt water to fresh, making it suitable for human consumption and irrigation, have been a fixture on the Middle Eastern landscape for 20 years. By mid-2007, Middle Eastern desalination accounted for nearly 75 per cent of world capacity.
Out of the top ten largest desalination plants, five are in the UAE and nine in other GCC countries, according to Global Water Intelligence.
The Jebel Ali desalination plant, the UAE's largest, is capable of producing 300 million cubic metres of water per year. By comparison the largest desalination plant outside the UAE, in Tampa Bay, Florida, produces about 12 per cent of the output of the Jebel Ali desalination plant.
As renewable energy becomes more available, there has been a greater push in developing more environmentally friendly and cost-effective ways to provide fresh water. With prices of fossil fuels like oil or gas having increased by 300 per cent since 2000, fossil fuel powered desalination plants are neither sustainable nor economically feasible in the long term.
"The lifetime of oil will last a maximum of 100 years from now and people are now starting to look for another option. This has become particularly important in the GCC area where we can gain to benefit from the sunshine and light to increase productivity," says Dawoud.
Each square kilometre of land in the MENA region receives solar energy that is equivalent to 1.5 million barrels of crude oil a year.
Booming population
According to the United Nations World Population Prospect 2004, the population of the MENA region will grow from about 300 million today to about 600 million in 2050.
"With the rapid population growth and shift towards urbanisation, access to water in an efficient, cost-effective manner is going to become increasingly important.
"There's also a great deal of focus on addressing the challenges of greenhouse gases and climate change so the application of forward technology and making solar more commercially viable is the second major object," said Rich Lechner, vice president of Energy and Environment at IBM.
The growing interest in implementing it is demonstrated by research and development initiatives with government entities such as the King Abdulaziz City for Science and Technology (KACST) in Al Khafji, Saudi Arabia.
IBM's research collaboration with KACST has resulted in the installation of the world's largest solar powered de-salination plant which is set to be in production by 2012. This plant will be able to produce 29.9 million litres of water a day, serving 100,000 people.
"The aim is to improve the efficiency behind the desalination project by making the reverse osmosis more efficient, requiring anything between 20 to 50 per cent less energy," says Lechner.
Newly developed membrane technology will be used for the first time with this plant which will be powered by ultra-high concentrator photovoltaic (UHCPV) technology, capable of operating a CPV system at a concentration greater than 1,500 suns, which is about three times the solar concentration of most concentrator photovoltaic panels currently in operation.
As well as being far more energy efficient, this use of membrane technology will mean the plant will be more durable and improve its commercial capability.
Another important aspect of the technology is that the membranes are far more effective at removing harmful chemicals from water.
In Abu Dhabi the Environment Agency is also pushing forward with solar powered systems and is in the process of installing 30 small-scale solar-powered desalination plants which will provide animals with watering holes in Abu Dhabi's desert environment.
Four plants are currently in use and the rest are due to be finished by March 2011. These plants will be installed or constructed in remote areas where there is no access to fresh water for wildlife or access to electricity.
Costs
Currently the cost of one desert desalination plant, with a capacity of five cubic metres of water per hour, is Dh3 million. The plants will be operated remotely and solar power will be harnessed through solar panels spanning 300 square metres at each site, enough to create 45 kilowatts of electricity per hour.
"We consider this project as a research and development project to increase energy efficiency through the use of renewable energy and the evidence is already there," says Dawoud.
According to the International Desalination Association, the daily production of desalinated water in the UAE is 8.4 million cubic metres.
Future desalination production investments by Abu Dhabi and Dubai are estimated to reach $40 billion (Dh146.8 billion) to meet increasing water demand.
One of the main hindrances to implementing solar power, according to Dawoud, is the initial construction cost. In the long run, with maintenance costs and consumption of energy taken into consideration, solar is the cheaper option.
Efficiency in land use is another problem presented in installing solar powered plants.
"With one square metre of photovoltaic cells you could only recover 18 per cent. As technology improves, it has increased up to 30 per cent. In areas where the land is expensive such as Abu Dhabi, this is very important as you are covering a huge area to produce a small amount of electricity," says Dawoud.
Other improvements have included developing inclined photovoltaic cells which can reach 300 metres in height inclined at a sharp angle so less land mass is used.
osmosis
WHAT IS MEMBRANE TECHNOLOGY?
In the last decade, membrane processes have developed very quickly.
The most common methods for desalinating water are currently through membrane systems such as reverse osmosis. This system uses less energy than thermal distillation, which has led to a reduction in overall desalination costs over the past decade.
In reverse osmosis, water is forced through a polymer membrane using pressure to filter out salt. The main challenge with large scale desalination plants is that it is a highly energy intensive process and particles in sea water tend to clog the membrane making it less effective therefore requiring more energy.
Membrane technology uses a chemical composition that causes the membrane to resist the particles from contaminating and clogging the membrane resulting in a reduction of 25 to 50 per cent in energy usage.
The second half of the technology is harnessing solar energy through concentrated photovoltaic plates to power the plants in a much more environmentally friendly, commercially viable fashion.
Photovoltaic technology uses lenses for mirrors to focus the sunlight on to silicon chips converting it into electricity. The industry norm is to concentrate the equivalent of about 500 suns on to a square centimetre of silicon. Trying to do any more will fry the chip.
The technology developed by IBM that will be used in its new desalination plant in Saudi Arabia will use new chips that are designed using highly conducting liquid metal that sits under the silicon chip. The liquid absorbs the heat from the chip and ferries it away.
"By using these new chips, we are able to concentrate 15 suns or three times the amount the photovoltaic lenses today can absorb generating up to three times the amount of power using the same amount of silicon technology," says Lechner. With the launch of the its solar powered de-salination plants, Lechner hopes it will be a growing trend.
"We are looking at ways to bring this intellectual property to market in other regions in the world not just for desalination but for applications with improving the safety of fresh water," he said.
How it works
An intake pump is positioned near a sea water source and pumped into the system and given initial pre treatment. Water is then forced through a polymer membrane using pressure to filter out salt in the desalination process. Once the fresh water and sea water are separated the freshwater should be stabilized and the ph tested to make sure it's fit for consumption before going into a fresh water storage tank.
— A.L
FUTURE
Other research initiatives by IBM include micro weather forecasting which can be placed on solar systems to optimise energy generation.
A further focus is on improving the efficiency of the smart grid to make more efficient use of the renewable power that is being distributed and stored. They are working in over 100 smart grid projects around the world to improve the efficiency to enable grids to support this generation in storage.
"For renewable to emerge we must have a grid that can support it. Energy of this kind has a much higher degree of varied fluctuation in terms of its generation capacities and we must be able to handle the distribute stores because the sun doesn't shine all the time," says Lechner.
By Aya Lowe
Gulf News 2010. All rights reserved.
