Why is there no osmosis in the solar pond?

Book of Synergy

Using the salinity of the sea to generate energy is a relatively new idea. Information that the aforementioned French engineer Georges Claude 1929 attempts to do this in Cuba have not yet been confirmed. The osmotic power is described for the first time 1748when the French physicist Jean-Antoine Nollet puts an alcohol-filled pig's bladder into a tub of water, whereupon the bladder swells and bursts.

In today's technical implementation, the high osmotic pressure between fresh and salt water, i. H. the difference between the high salinity of sea water and the low of 'sweet' river water, used as an energy difference. Are fresh and salt water namely through a semipermeable membrane separately, water flows from the fresh to the salt water side - driven (or sucked?) by the difference in concentration of the salt. To a certain extent, this principle forms a mirror image technology for reversible osmosis (RO), which is already being used successfully for seawater desalination.

Of the approx. 30 available worldwide · 1012 W could be about 2.6 · 1012 W can be used. The efficiency of osmosis power plants is given as 25% to 30%. There are currently three methods available, all of which are based on semi-permeable membranes:

The use of the osmotic pressure between the different surface water and deep water salinity in the sea itselfwith the 'stronger' saline solution rising. The rise and / or the subsequent fall is intended to generate electricity.

Another form is the use of osmotic pressure at the mouths of the sea of the rivers. The fresh water meets the sea water here with an osmotic pressure difference of around 24 atmospheres, which should be sufficient to build up a 238 m high salt water column. Extreme cases like the Salt Lake in the USA with an osmotic pressure difference of 380 atmospheres or the Dead Sea between Palestine and Jordan with as much as 500 atmospheres (compared to the fresh water of the Jordan) can of course be exploited particularly well. With these pressure differences, correspondingly high columns of salt water could be built - where the free fall is then used again to generate electricity. At the Dead Sea, the theoretical difference in altitude is around 5,000 m (!).

A plus point of this method is that many large cities are located directly at the mouth of rivers - which makes a lossy transmission of energy unnecessary. For the mouth of the Columbia River, Californian scientists have calculated that this would result in a useful power of around 4,600 MW if the flow rate of the river (6,600 m3/ s) only 50% could be used with an efficiency of 30%.

Alternatively, seawater can also be drained from oil submarine salt domes pumped to dissolve the salt. The resulting high-percentage saline solution is then pumped to the sea surface, where the osmotic pressure difference to normal seawater is used. The positions of many submarine salt domes are known through decades of oil exploration, but the fairly safe occurrence of oil residues in the salt solution would require energy-consuming pumping of the salt solution back into the salt cave if this approach were implemented.

However, a 'membrane-less' method is also available, in which the different steam pressure of fresh and salt water is used. At the same temperature, more water evaporates from a container with fresh water than from one with salt water. Due to the lower steam pressure above the salt water, the water vapor moves from the fresh water to the salt water tank. If a turbine is interposed here, energy can be generated with it. The surface of the water itself acts like a membrane. However, only small pressure differences are achieved in this implementation, so that very large turbines are required here. The heat exchangers that are also required are, however, still cheaper than the membranes.

The technical realization of Osmosis- or Salt power plants therefore mostly depends on the special membranes that hold back the salts efficiently and as completely as possible - but at the same time are well permeable to water. Due to the lack of suitable membranes, the principle can be applied to the 1970s Years ago, when the Israeli scientist Sidney Loeb looked at it. Since the middle of 1990s For years, however, there have been various new approaches to develop and manufacture suitable membranes from polymers.

Let us now come to the chronology of development and implementation:

1999 the company is founded in Laguna Beach, California, by inventors Warren Finley and Edward Pscheidt Wader LLC founded, which deals with the generation of energy from the mixing of fresh and salt water without the use of membranes. The company tries its patented Hydrocratic Generator to market that also under the name Wader Tower becomes known. The patents date from 2001, 2006 and 2008.

In May 2004 experiments with pipes of different lengths and diameters are carried out on board the research platform FLIP off San Diego. This over 100 m long platform belongs to the US Navy and is operated by the Marine Physical Laboratory of the Scripps Institution of Oceanography. A video also shows a laboratory test in which the fresh water is fed from a higher reservoir into a vertical buoyancy tube that is completely located in a basin with salt water. The rising fresh water rotates a small turbine that is located inside the tube. 2010 However, the company is still looking for funding to build a demonstration plant.

A similar system has already been used under the name SHEOPP Converter reported (Submarine hydro-electro-osmotic power plant). This system seems to the Italian M. Reali from Milano in the year 1980 to go back.

2001 the government-owned Norwegian energy company launches Statkraft Energi, Oslo, who has been 1997 busy with PRO technology (Pressure Retarded Osmosis), together with scientists from the GKSS research center in Geesthacht near Hamburg, the Portuguese Instituto de Ciencia e Tecnologia de Polimeros, the Norwegian Institute of Technology (SINTEF) and the Helsinki University of Technology, an EU-funded joint project to develop an osmosis power plant. First of all, more than 50 different types of membranes are examined until two of them remain that have proven themselves for years in osmosis systems for seawater desalination: cellulose acetate, which is also processed into rayon, and the so-called thin-film composites (TFC), which consist of a wafer-thin polyamide film and a carrier material for stabilization (polyamides are known under trade names such as nylon or perlon).

2004 The Norwegian state and Statkraft will take over the further financing of the test facility at the Sintef headquarters in Trondheim and the two planned ones Salinity Power Pilot plants.

Osmosis power plant (graphic)

The critical factor in the implementation of this technology is the power that can be generated with one square meter of membrane area. While the plastic membrane from Geesthacht can initially only deliver an output of less than 0.1 watts per square meter, three years later the scientists achieve just under 2 W / m2. The target is, however, the power to 5 W / m2 to increase, because only then does the membrane work economically.

The European Commission and the Statkraft Group (which currently operates 133 hydropower plants in Norway, plus 19 in Sweden and four in Finland) put the potential in Europe at 200 terawatt hours per year, which is roughly twice the electricity consumption of a country such as Norway corresponds. The Rhine alone could generate 3 GW of energy at its estuary in the Netherlands.

At the numerous Norwegian river mouths, a total of up to twelve billion kW / h could be generated per year - which would correspond to around 10% of the annual demand. For the entire European area, one comes to a possible energy production of 200 billion kW / h per year.

The biggest challenge, however, is still to find membranes that are efficient, robust and yet inexpensive. The scientists expect at least another five years of research to develop membranes that can also be used commercially by the middle of the decade.

In October 2007 A message spreads rapidly through almost all media: The Norwegian Statkraft Group is going to build the prototype of an osmosis power plant with an output of 2-4 kW in the municipality of Hurum, at a river mouth in the southern foothills of the Oslofjord. By then, the company had already invested ten years of research and development in the technology. The costs for the upcoming project are estimated at around € 13 million at this point in time.

In the press, the modest plant is presented as a worldwide pioneering act of great importance. Either Statkraft has a very efficient press department - or the remarkably broad publication of this news is an indication of the great need for new proposals and solutions to the energy question ...

Construction will start in summer 2008, and in November 2009 the prototype plant in the former Södra cellulose factory in Tofte, 96 km southwest of Oslo, goes into operation. It will be opened personally by the Norwegian Princess Mette-Marit. According to current statements, the system cost $ 5 million and now generates between 1.5 kW and 2 kW of electricity.

The membranes used by the Institute for Polymer Research GKSS generate an electrical output of 3 W per square meter. They are 0.1 micrometers thin and consist of several layers on a stabilizing carrier fabric. The test system will initially work at 12 bar, which corresponds to a waterfall 120 m high.

To 2020 Statkraft already sees dozens of large-scale plants in operation, which together cover 12 TWh, or around 10% of Norwegian demand.

With start-up capital financing from Syddansk Teknologisk Innovation A / S 2005 the company danish Aquaporin with headquarters in Lyngby, north of Copenhagen, with the aim of revolutionizing the filtering and desalination of water through the use of industrial, biotechnological methods. The core business is the development of the aquaporin membrane technology, which is starting 2011 to be marketed and licensed.

Knowing that aquaporins (AQP) are proteins that form channels in the cell membrane to facilitate the passage of water and some other molecules, you understand the choice of the company name.

In April 2007 The company receives 37 million DKK investment capital, and a three-year EU development project is started, which Aquaporin is carrying out together with European industrial and research partners.

2008 the development of the artificial proteins, which is being carried out by the partner company Novozymes, is still at an early stage, while aquaporin is working on the grids and membranes themselves. However, there is now also a collaboration with the French water company Veolia in the field of desalination. In the medium term, the technology is then to be used in the field of osmotic energy generation (see EP No. EP1937395 from 2008).

2010 Aquaporin is owned by the M. Goldschmidt Holding A / S Group, further shareholders are Morten Østergaard Jensen Holding ApS and Arteffekt Holding ApS. The second EU and first US patents are also granted this year.

Already in March 2007 builds the Dutch energy research center KEMA, which has since 2002 busy with the salinity energy, together with the also Dutch company Volker Wessels (VWS) on a 250 kW prototype, which is based on the principle of the so-called reverse electrodialysis (Reverse Electrodialysies, RED) works.

The project is based on the objective of putting together a 200 MW system in the future from individual 250 kW modules, each of which is the size of a sea container. It is calculated that using this technology at all of the country's estuaries would produce a total output of 3,300 MW.

In March 2009 is proposed in Holland, the 75 year old Afsluitdijk dike up 2020 to be converted into a salt water power plant that will generate 200-300 MW of electricity. At the Dutch Research Institute for Hydrotechnology Wetsus At this point in time in Harlingen, a small rotor is already turning in a laboratory system. Researchers from the international consulting firm KEMA, who are responsible for the Blue Energy baptized system received an innovation award.

In November 2009 Jan Post received an award from Wageningen University for his corresponding doctoral thesis ('Blue Energy: electricity production from salinity gradients by reverse electrodialysis'), and another dissertation from Piotr Dlogolecki at the University of Twente was entitled' Mass Transport in Reverse Electrodialysis for Sustainable Energy Generation '.

She is also already involved 2005 founded company REDstack B.V., a spin-off from Wetsus. The company announces on its homepage that - at least theoretically - from a volume of 1 m3/ s fresh water and the same amount of sea water 1 MW of electricity can be generated. In the same year, the European Salt company (ESCO-salt), Wetsus, Harlingen Industries and Magneto Special Anodes in Schiedam agree to build a 5 kW Blue Energy test facility in Frisia / Harlingen. This plant will be available from June 2008 by REDstack companies.

In July 2010 the company receives approval to build a 50 kW demonstration power plant near Breezanddijk on the 20 km long Afsluitdijk dike, which separates the salty North Sea from the less salty IJsselmeer. However, the financing of the € 3.5 million project has not yet been secured. In October 2010 start two research projects funded by the EU, in which REDstack is also participating. Further details are not yet available.

For the future, a commercial plant with an output of 25 MW and 5 million m2 Membrane area talked about, possibly around 2015 could be built. It would be the size of a football stadium.

center 2009 Another technology becomes known that is being developed by the physicist Doriano Brogioli at the University of Milano-Bicocca in Monza. His prototype cell is based on two pieces of activated carbon, a porous carbon that is generally used to filter water and air. Yury Gogotsi, director of the A.J.Drexel Nanotechnology Institute at Drexel University in Philadelphia refers to the technology as Reverse capacitance desalination.

The electric double layer capacitor (Electronic Double Layer, EDL) consists of two porous carbon electrodes that are immersed in salt water. The electrodes are connected to a power supply so that one is charged negatively and the other is charged positively. Since salt water consists of positively charged sodium ions and negatively charged chloride ions, the positive electrode attracts the chloride ions and the negative electrode the sodium ions. With the help of the electrostatic force that keeps the oppositely charged ions close to their respective electrodes, the EDL capacitor can store a charge. To remove this, fresh water is pumped into the device, causing the sodium and chloride ions to diffuse away from the electrodes against the electrostatic force.

The system basically converts the mechanical work of mixing salt and fresh water into electrostatic energy, which can then be extracted as usable energy. A typical cell, according to Brogioli, requires about three dollars worth of activated charcoal, and with sufficient water flow, it should be able to meet the needs of a small house.

The Almaden Research Center of the IBM company is also busy in Mitte 2009 with the osmotic pressure between fresh and salt water and prepares a corresponding study. The company has been developing RO membranes for seawater desalination for some time and is working with the Japanese materials company Central Glass, the University of Texas in Austin and the research center of the King Abdul Aziz City for Science and Technology in Saudi Arabia. Arabia together.

In contrast to the approaches described, in which the osmotic pressure is generated by adding fresh water to the salt water, the researchers at IBM are trying to achieve this pressure by adding clean (or largely clean) water to the extremely salty wastewater from desalination plants.

Oasys Water Inc. (Osmotic Application Systems) in Cambridge, MA, a spin-off from Yale University, received in February 2009 Investment funding of $ 10 million to create a patented technology called Engineered osmosis (EO), which should cut the costs of seawater desalination in half. Investors include Advanced Technology Ventures, Draper Fisher Jurvetson, and Flagship Ventures.

In the technology invented by Robert McGinnis, the waste heat from power plants is used to increase the osmotic pressure considerably. Instead of dividing it into salt water and fresh water, Oasys divides salt water and very salty water. This consists of water mixed with a special kind of salt, the thermolytic salt is called - in the present case this consists of ammonia and carbon dioxide. When heated, these salts turn into gas.

This extremely salty solution presses fresh water from industrial sewage or seawater through the membrane, leaving brine behind. The thermolytic mixture is then slightly heated, causing the ammonia and carbon dioxide to outgas and leave fresh water behind. To repeat the process, the ammonia and carbon dioxide are brought back together. The heat required is relatively small at around 20 ° C, so that the waste heat from a power station or factory is sufficient.

Also, since only a small amount of electricity is required to pump the water (as opposed to reverse osmosis, which requires very high pressure), Oasys explains that fresh water can be produced at one-tenth the cost of today's reverse osmosis systems. Until December 2009 a tiny pilot plant will be built in autumn 2010 a larger demonstration plant is to follow. Then you want to tackle the topic of energy.

The company believes its system can also be used as an inexpensive, large-scale storage device for power. In contrast to an output of 3 W / m2 With the previous membranes, Oasys reckons with the high osmotic pressure of the ammonia-carbonic acid salt up to an output of 200 W / m2 get.

Such a large battery would consist of two huge collecting tanks, one for salt water and one for fresh water, which would be built next to a power plant. The waste heat from the system is regularly used to desalinate the water. Geothermal and solar energy are also mentioned as alternative heat sources. As soon as more power is required during peaks in demand, salt water and fresh water are used to generate electricity, with an efficiency between 50% and 80%.

According to the company, up to an additional $ 50 million is required to develop the technology to product maturity.

At the Chair of Energy Systems and Energy Economics at the Ruhr University Bochum, Mitte 2010 Dipl.-Ing. Peter Stenzel the criteria with which suitable locations for osmotic power plants can be identified. In addition to the technical and economic aspects, ecological considerations are also included for the first time. The river has to tolerate a certain amount of water being withdrawn, whereby a minimum level should not be fallen below in order not to endanger plants and animals. In the estuaries analyzed around the world, locations on the Mediterranean coast, in Scandinavia and America are particularly promising. The potential in Germany is rather low.

Also in the middle 2010 Cleantech consulting firm Kachan & Co. from San Francisco publishes a 17-page report (for $ 395!), in which it is stated that the potential of osmotic energy is large enough to last for about a year 2030 to be able to cover around 50% of Europe's electricity needs.

Overall, the use of marine salinity is still associated with extremely high system costs, the necessary semi-permeable membranes are very expensive and the technology is still poorly developed overall. The membranes currently in existence cost around € 30 per square meter (as of 2010).

Objections from environmentalists regarding these projects have not yet been raised - assuming there would be no impact as a result would be a bit short-sighted.

Sea Solar Power International in Baltimore, Maryland, a company of Abell Foundation, analyzed beginning 2006 the US patent by Richard M. Dickson of Portland, Oregon, whose proposal is based on the use of the pressure difference between surface water and water at great depths, which should make possible outputs of up to 500 MW. Both Howaldtswerke-Deutsche Werft AG (HDW) in Kiel and Florida Hydro Inc. in Palatka, Florida, have already assessed the system, but details have not yet been published.

The animation on Dickson's homepage shows an underwater construction with a diameter of 15 m at a depth of 100 m, in which a kind of piston moves cyclically, whereby - albeit more slowly - the sea surface also rises and falls cyclically.

Dickson got the idea for this year 2001when he read in a book about Dr. William Beebe from the 1930s Years ago read how a device filled with water at a depth of around 450 m, which was then brought to the surface, released the overpressure inside with incredible force. A patent application for the Submersible Hydroelectric Propulsion System (SHPS) from the end 2006 is rejected.

According to Sterling D. Allan of peswiki.com (November 2006) is a system that has no clear input energy. So he doesn't expect it to work. The contact with the HDW had nothing to do with an 'evaluation' but was limited to a polite refusal.

In February 2008 receives Dickson for his hydrosphere concept, which he likes to use in interviews Air Water Gravity Generator (AWGG) or Ocean Pressure Electric Conversion (OPEC) system, a certificate of honor from the History Channel and the Modern Marvels Invent Now Challenge 2007. When this chapter is updated, it ends 2010 however, his site is no longer online.

The latent hydrostatic energy (read: the water pressure) is also said to be the reason for the function of the Spiteri water pump of the Maltese inventor Joe Spiteri-Sargent for which he 2007 receives the Energy Globe Award of the European Parliament - although patenting of the system has been rejected twice in England. A patent 2006 in Malta, on the other hand, seems to have been accepted.

The machine works below the surface of the water and uses a rhythmic tilting process to convert the hydrostatic energy of a body of water using buoyancy and gravity in such a way that water can be pumped up and ultimately an artificial waterfall is created, the energy of which generates electricity via a turbine.

Spiteri gets the inspiration for his machine 1989 in Canada, where he has lived for a long time, and owes this to former Prime Minister Dom Mintoff, the 1980 said: "If only Malta had something like a waterfall, our electricity would be much cheaper." 1991 Spiteri starts together with the hydraulic engineer Marco Cremona with the development of prototypes and the implementation of practical tests in a 4 m high water tank in Luqa.

In his company Sargent Enterprises Ltd. (SEL) are investing 22 family members and friends, which is what makes development and prototype construction possible in the first place. The photo shows a 1st generation model. In the medium term, the inventor is thinking of stations with several individual pumps that produce up to 250 kW.

Newspaper publisher Ruben Pesebre invented a possibly similar system. Together with his partner Nemesio, Boyet ’Antonio Jr. he leaves 2005 in the Philippines one Underwater Pressure Energy Converter (UPEC), about which I have not yet been able to find out more details.

Brazilian researchers from Campinas University present at the American Chemical Society meeting in Boston in August 2010 proposed a system in which panels on house roofs generate electricity from the energy in the atmosphere that would otherwise be discharged in lightning bolts.

At high humidity, aluminum particles are charged positively, silicon particles, however, negatively. According to the scientists, this proves that water in the atmosphere collects electrical charges, transforms them and transfers them to other materials. The resulting charge will Hygroelectricity called, where hygro stands for moisture.

The electricity from the atmosphere is therefore a perspective especially for the tropics with their many thunderstorms. The Brazilians are currently testing which metals are most suitable for panels.


This new technology also forms the appropriate transition to water vapor - the engine of the first industrial revolution. As one of the physical states of water, it is also important enough to be considered here a little closer.