His Majesty King Willem-Alexander will put the first blue-energy power plant in the world to use on Wednesday, 26 November. In this test plant at the Afsluitdijk the joining of river and sea water is used to generate sustainable energy. This is because by using cleverly designed membranes (special filters), you can generate electricity directly from the difference in salt concentration. Researchers from the University of Twente's MESA+ research institute supplied the knowledge for the membranes and the technology for this power station.
In the future it will be possible to generate ten percent of the Dutch energy consumption via this technology. With its large rivers such as the Rhine and the Meuse, the Netherlands has great potential in this area. The company REDstack BV now takes 'Blue Energy' to market in the Netherlands. The University of Twente makes an important contribution to the research and the further development of the plant, which involves intensive collaboration with the research institute Wetsus, Fujifilm and other organizations.
The expectation is that Blue Energy will succeed in generating energy for 8 cents per kilowatt-hour (without subsidies). Solar and wind energy are currently a lot more expensive, energy from petroleum is still cheaper at the moment. In addition, Blue Energy can be generated continually, contrary to solar and wind energy, which are both dependent on availability and the weather. The total quantity of electricity that could be generated on the Afsluitdijk is equal to 1200 billion AA batteries a year, or, in other words, sufficient for the energy requirements of 500,000 households. It is potentially possible to generate the entire electricity consumption worldwide with Blue Energy.
How it works
"Electricity can be generated wherever fresh water and salt water meet, for instance where rivers flow into the sea," explains Professor Kitty Nijmeijer of MESA+ research institute of the University of Twente. Over the past eight years she, together with her department, put a lot of work and effort into developing and improving the membranes and the Blue Energy technology.
"This is because there are many more charged particles - ions - in salt water than in fresh water. Separating salt water from fresh water, using a membrane that only allows positively or negatively charged particles to permeate, results in a difference in voltage which you can convert into electricity. The principle has been known for some time, but its efficiency had always been far too low to make large-scale application interesting."
More efficient membranes
"At the moment our membranes in the lab can supply a capacity of about 1.3 watt per square meter of membrane," continues Nijmeijer. "We need to increase this to 2 to 3 watt per square meter in order to make blue energy economically profitable. Our PhD candidates will use the power plant on the Afsluitdijk as a research facility for improving efficiency on a large scale and to research the effects of using the natural sea and river water."
The installation currently contains some four hundred square metres in membranes, which can process 220,000 litres of salt water and 220,000 litres of fresh water every hour. This figure will be increased to 100,000 square metres during the next few years. In order to save space, different membranes are placed immediately adjacent to one another, at a distance of 0.3 to 0.5 millimetres. A commercial installation will eventually need millions of square metres of membranes. "This seems much, but practically speaking this is certainly feasible," states Nijmeijer.
Doctoral researchers
Earlier this year two researchers from Nijmeijer's Membrane Science & Technology department already obtained their doctoral degree in the field of Blue Energy. David Vermaas busied himself with the hydrodynamics and pollution of the membranes. He optimised the way in which water passes through the membranes and came up with a number of ways in which to reduce pollution of the membranes. Enver Güler occupied himself with the membrane development. He developed a membrane which yields the highest energy to date. Recently two new PhD candidates started on the project who are working onwards from these developments.
The research is a joint venture by the MESA+ research institute and the Green Energy Initiative of the University of Twente.
