Osmotic (Sea Water) Power: Nano Generators could Turn âBlue Energyâ into 2 Terawatts of Clean Energy Per Year
âWith the potential to be a considerable source of energy, osmotic power has gained ground in recent years with several pilot power plants around the world.Â
Itâs estimated that a total of around two terawatts of clean energy â the equivalent of around 2000 nuclear reactors â could be harvested worldwide from locations where salt concentration gradients occur.
Two main membrane technologies exist to harness osmotic power from solutions with differing salt concentrations. One is pressure retarded osmosis (PRO) which uses membranes to exploit pressure differences and drive a turbine, while the other is called reverse electrodialysis (RED) which involves ion exchange across a charged membrane. However, both methods have been limited by the efficiency and power density of materials that have only been able to generate a few watts per square metre of membrane.
However, the worldâs first prototype PRO osmotic power plant, which was opened by Statkraft in Norway in 2009, was deemed uneconomical and shelved in 2013.
âIf the system can be further developed to draw from two separate reservoirs of different salinity with minimal energy consumption using innovative techniques, the nanogenarator system can be perpetually self-powered...These nanogenerators could be deployed in remote locations without having to be recharged or have batteries replaced, to power devices such as nanosensors.â
(via Osmotic (Sea Water) Power: Nano Generators could Turn âBlue Energyâ into 2 Terawatts of Clean Energy Per Year « Great Things from Small Things .. Nanotechnology Innovation)
Water Generates Electricity (with a pinch of salt)
Osmotic Power Plant by Statkraft
Analysis on Pressure-Retarded Osmosis Reveals High Energy Generation Potential
âThe Stanford researchersâ 2011 conclusion was that 13% of the worldâs energy demand by that time could be met by this renewable energy source.The PRO mechanism of exploiting renewable energy utilizes the potential difference in saltiness between the salty oceanic water and the riverâs fresh water. The American Chemical Society explains PRO as a process where âfreshwater flows naturally by osmosis through a special membrane to dilute seawater on the other side.â The generated pressure from that flow spins or turns a turbine generator which in turn produces electricity.
In their study, Yip and Elimelech conclude that PRO generated electricity could sustain 520 million people and yet emit no carbon dioxide in the process. To generate the same amount of power, in comparison, coal-fired plants would end up producing greenhouse gases to the tune of over a billion metric tons per year!â
(via Analysis on Pressure-Retarded Osmosis Reveals High Energy Generation Potential | The Green Optimistic)
REAPower: Electricity from brine
âREAPower targets an innovative concept based on the reverse electrodialysis technology. This technology consists of the extraction of the âosmotic energyâ from two salt solutions showing a large difference in salt concentration, what is called salinity gradient power (SGP).
For fueling the process, constant supply of two water streams with a salinity difference is necessary. Up to now, SGP research focused mainly on the combination of fresh water as the low concentration solution and seawater as the high concentration solution. However this approach has important disadvantages as the low salinity water increases the electrical resistance.
REAPower is overcoming this limitation by using brine and sea or brackish water for generating electricity.
The consortium worked on optimising materials and components tailored to the requirements of the SGP-RE technology operating with high salinity brine and seawater, developed and verified a simulation model through tests on laboratory stacks, evaluated and improved the performance of the overall system through tests on a prototype fed with real brine from a salt pond, analysed the economics, assessed the perspectives of the technology and defined the next R&D activities that are needed aiming at an eventual commercialisation.â
$10 million coming to Bay Area desalination project; but itâs not on the ocean
âThe ocean has been eyed as a panacea for Californiaâs perpetual trials with drought. The idea is that with enough desalination plants, the vast sea will provide an endless supply of drinking water.
But as a handful of these much-hyped projects take shape along the coast, many communities have found that desalination makes a lot more sense inland. Dozens of landlocked water districts are turning to briny groundwater basins or brackish rivers and bays, where the process of removing salt from water is generally a lot easier and cheaper.
About 2 percent of Californiaâs drinking water comes from desalination, according to the state Department of Water Resources, which awarded the grants. The top supplier is the $1 billion Carlsbad Desalination Plant in San Diego County, which opened in 2015 as the nationâs biggest desalting facility. It provides up to 400,000 people with treated ocean water in an area long dependent on water imports.
Less than a half dozen plants serve up seawater for residential purposes, however. About two dozen sites, meanwhile, are treating brackish inland supplies, state records show. And more are in the works.
Most plan to deploy the same reverse osmosis technology that is used in coastal projects, in which water is pushed through semipermeable membranes, to treat groundwater. Eastern Kern Countyâs Indian Wells Valley Water District, for example, is looking to tap underground basins in the high desert for desalination. The city of Camarillo in Ventura County is proposing to desalt water from a local aquifer, where supplies have become increasingly saline.
The exceptions are in Orange County and the city of Santa Barbara. The South Coast Water District in Laguna Beach received money for a new beachfront desalination plant, while Santa Barbara was funded for upgrades to an existing seawater facility.
Getting permits for oceanfront plants is more difficult as well, in part because they threaten marine life, with intake valves sometimes sucking in fish and the salt-removal process leaving behind a toxic brine.
The state money for desalination projects comes from Proposition 1, the $7.5 billion water measure approved by California voters in 2014, during the historic five-year drought. The funds are aimed at boosting water supplies and protecting watersheds. In addition to the latest round of money for desalination projects, another $50 million is earmarked for salt removal.â
(via $10 million coming to Bay Area desalination project; but itâs not on the ocean |SF Chronicle)
Opinion CommentaryMarine environmental damage will be a minimal trade-off
âProponents claim that the process is benign, while opposition groups decry the destruction of marine life. As a marine biologist and environmental consultant, I have been studying these issues for several years, and my analysis of the available scientific data indicates that the benefits of desalination outweigh its minor environmental impacts.
How could desalination affect our oceans? For simplicityâs sake, we can distill the answer (no pun intended) down to the fact that there are two major facets of the process that account for most potential impacts.
The first of these is called entrainment...the consensus amongst scientists who have published on this issue is that entrainment typically accounts for only about 1 percent or 2 percent of plankton mortality in a given area. In other words, the actual effect on marine life is negligible.
The second major potential impact is concentrated brine disposal. For each gallon of fresh water produced via desalination, 2 gallons of concentrated (twice as salty) brine are produced and pumped back into the ocean.
To deny that there are any environmental impacts associated with such a large-scale industrial activity as desalination would be silly. However, these impacts appear to be minor, and represent the trade-off we must be willing to accept for an increase in water supply to our drought-stricken state. Heightened scientific research, monitoring of coastal ecosystems in the vicinity of desalination plants, and innovative technologies to achieve ever-greener desalination methods, can ensure that the industry moves forward in an environmentally responsible manner.â
(via Opinion CommentaryMarine environmental damage will be a minimal trade-off | San Diego Union Tribune)
The idea of creating a desalination pipeline to create electricity and water for a forest in the Mojave Desert - Mojave Forest Project
The high energy needs of reverse osmosis of seawater desalination can be met by an osmotic power plant that feeds off of the waste brine created by a desalination plant, whose waste brine is normally mixed with treated sewage before being released back into the ocean. By using sea water and salty brine vs. using river water (fresh) and sea water, the former has a greater potential salinity range and thus greater extractable pressure potential, thus more turbine power generation, than that extracted using fresh water and sea water (also because of increased electrical resistance.) In addition to improved PRO osmotic power plants the RED shows the most promise for development of a membrane ideally made from graphene. The salty brine waste product of a desalination plant creates the fuelstock necessary to produce salinity-gradient power (SGP) in an osmotic power plant.Â
In the future California coastal desalination plants should not dump salty brine back into the ocean, the right thing to do is to reuse the salty brine to create electrical power which can be used for reverse osmosis desalination to make fresh water, as well as provide clean renewable energy through advancing RED, PRO and SGP technology. Because of environmental issues surrounding increased ocean salinity, coastal desalination plants cannot operate at capacity without damaging the ocean ecosystem and related oceanside tourism because of the increasing occurence of increased green slime, red algae and dead schools of fish in bays and harbors surrounding the coastal desalination plant.
A desalination pipeline could provide both an unlimited supply of sea water as well as generate the salty brine needed by a PRO and RED (SGP) osmotic power plants. Both the desalination plants and osmotic power plants do not have to be located on valuable coastal real estate and can be located where solar, wind and hydroelectric power work the best in deserts and mountain passes.Â
The US Department of Energy Office of Energy Efficiency and Renewable Energyâs Advanced Manufacturing Office who lead the Energy-Water Desalination Hub should invest in PRO and RED (SGP) osmotic power research and development, by building an osmotic power and seawater pipeline grid infrastructure, providing an affordable water solution for California, Nevada and Arizona, similar to the European Unionâs efforts to advance âblueâ renewable energy research and power plant development.