Osmosis: In Search of the Perfect Membrane
Osmotic power is not the first thing that comes to mind when you think of renewable energy, nor is it a new concept. However, thanks to some initial research and development in Norway under Europe's largest renewable energy provider, Statkraft, the technology is gaining momentum around the world. Pursued for its mere potential, developers of innovative technologies are coming together in an effort to create systems that could potentially fill the renewable energy gaps of the likes of solar and wind power.
Based on the phenomenon of osmosis, the energy is created through the transport of water through a semipermeable membrane, similar to how plants absorb water through their leaves. In this case, when fresh water meets salt water, usually in areas where a river runs into a sea, monumental amounts of energy are released. That energy can then be utilized to generate power using a manmade membrane—the most critical piece of the process.
The flow of water is predictable, and therefore reliable, whereas wind and solar depend on the timing of sunlight and wind conditions. Areas where rivers meet water are also generally around industrialized centers, which would mean osmotic plants would be placed where consumers live. In areas like Northern Alaska or in developing countries lacking an operating infrastructure or a sufficiently functioning grid, osmotic power would be particularly beneficial.
In an osmotic power plant, fresh water and salt water are guided into separate chambers on the sides of an artificial membrane. The salt molecules on the sea water side suck fresh water through the membrane, increasing pressure that creates a waterfall that is used to generate a turbine for power. Although Statkraft's first system in 2008 was successful and generated a lot of excitement, it was incredibly small—generating only enough electricity to power a coffee machine.
“With the membrane we were using, we realized there was a large gap in taking an idea from the laboratory and scaling up,” says Statkraft's head of osmotic power Stein Erik Skilhagen.
One big issue concerning membranes is finding the right thickness, capable of withstanding extreme pressure without getting clogged up with salt. Last summer, Statkraft announced it would begin working with Japan-based Nitto Denko, the world's largest manufacturer of membranes. Unable to comment on the materials of the membrane, Skilhagen believes that by the end of 2012, the technology will be good enough to build a system that is significantly larger than one Statkraft has today.
With a promising market opportunity, supporters claim that the technology is unlimited. According to Statkraft, osmotic power has an estimated global potential of 1600 to 1700 Twh, based on figures from surveys of areas around the world where fresh water meets the ocean. That's roughly equal to China's total electricity consumption in 2002.
After Statkraft held an invitation-only event in Amsterdam to initially discuss the developments, it attracted over 100 participants in an event held in San Diego in 2010.
“The quality in presentations had significantly increased at that point and the global awareness and momentum in development of this technology had increased beyond belief from when he had met just two years earlier in Amsterdam,” says Skilhagen.
Following that conference, more initiatives have been procuring globally, which has led to an even larger event coming up this April in Barcelona, Spain.
“We have had so many requests, it's hard to believe how many people there are wanting to present their developments and technologies,” says Skilhagen. “We are looking forward to once again hosting a venue where the global leaders of this industry will come together and share their knowledge and results.”
Osmosis, also known as reverse electrodialysis (RED), has spurred other similar technologies. Researchers at Pennsylvania State, for instance, have developed a new device that combines two forms of renewable energy—using bacteria and saltwater—to generate more electricity than either alone, while cleaning wastewater at the same time.
While RED requires a large number of membranes and must be located by the sea, researchers have come up with a device that reduces the amount of membranes used to create an electric current. Using microbial fuel cells (MFCs), the system bypasses the need for salt water by using ammonium bicarbonate solution as a substitute, allowing it to be used in areas far from the ocean. The technique could be adopted in developing countries to provide clean water and power for homes.
Of course, osmotic power is still, for the most part, in the pilot phase and it could be a few years before the technology becomes a commercial reality. Regardless, figures of its potential are fueling motivation for more R&D.
“The more companies there are working on this, the more the competition grows and the higher the likelihood is to find solutions in reducing the costs and spreading the technology,” says Skilhagen. “In our upcoming conference, people are working together to get to the solutions we need in this field.”
Carbon dioxide removal revenues worth £2bn a year by 2030
Carbon dioxide removal revenues could reach £2bn a year by 2030 in the UK with costs per megatonne totalling up to £400 million, according to the National Infrastructure Commission.
Engineered greenhouse gas removals will become "a major new infrastructure sector" in the coming decades - although costs are uncertain given removal technologies are in their infancy - and revenues could match that of the UK’s water sector by 2050. The Commission’s analysis suggests engineered removals technologies need to have capacity to remove five to ten megatonnes of carbon dioxide no later than 2030, and between 40 and 100 megatonnes by 2050.
The Commission states technologies fit into two categories: extracting carbon dioxide directly out of the air; and bioenergy with carbon capture technology – processing biomass to recapture carbon dioxide absorbed as the fuel grew. In both cases, the captured CO2 is then stored permanently out of the atmosphere, typically under the seabed.
The report sets out how the engineered removal and storage of carbon dioxide offers the most realistic way to mitigate the final slice of emissions expected to remain by the 2040s from sources that don’t currently have a decarbonisation solution, like aviation and agriculture.
It stresses that the potential of these technologies is “not an excuse to delay necessary action elsewhere” and cannot replace efforts to reduce emissions from sectors like road transport or power, where removals would be a more expensive alternative.
The critical role these technologies will play in meeting climate targets means government must rapidly kick start the sector so that it becomes viable by the 2030s, according to the report, which was commissioned by government in November 2020.
Early movement by the UK to develop the expertise and capacity in greenhouse gas removal technologies could create a comparative advantage, with the prospect of other countries needing to procure the knowledge and skills the UK develops.
The Commission recommends that government should support the development of this new sector in the short term with policies that drive delivery of these technologies and create demand through obligations on polluting industries, which will over time enable a competitive market to develop. Robust independent regulation must also be put in place from the start to help build public and investor confidence.
While the burden of these costs could be shared by different parts of industries required to pay for removals or in part shared with government, the report acknowledges that, over the longer term, the aim should be to have polluting sectors pay for removals they need to reach carbon targets.
Polluting industries are likely to pass a proportion of the costs onto consumers. While those with bigger household expenditures will pay more than those on lower incomes, the report underlines that government will need to identify ways of protecting vulnerable consumers and to decide where in relevant industry supply chains the costs should fall.
Chair of the National Infrastructure Commission, Sir John Armitt, said taking steps to clean our air is something we’re going to have to get used to, just as we already manage our wastewater and household refuse.
"While engineered removals will not be everyone’s favourite device in the toolkit, they are there for the hardest jobs. And in the overall project of mitigating our impact on the planet for the sake of generations to come, we need every tool we can find," he said.
“But to get close to having the sector operating where and when we need it to, the government needs to get ahead of the game now. The adaptive approach to market building we recommend will create the best environment for emerging technologies to develop quickly and show their worth, avoiding the need for government to pick winners. We know from the dramatic fall in the cost of renewables that this approach works and we must apply the lessons learned to this novel, but necessary, technology.”
The Intergovernmental Panel on Climate Change and International Energy Agency estimate a global capacity for engineered removals of 2,000 to 16,000 megatonnes of carbon dioxide each year by 2050 will be needed in order to meet global reduction targets.
Yesterday Summit Carbon Solutions received "a strategic investment" from John Deere to advance a major CCUS project (click here). The project will accelerate decarbonisation efforts across the agriculture industry by enabling the production of low carbon ethanol, resulting in the production of more sustainable food, feed, and fuel. Summit Carbon Solutions has partnered with 31 biorefineries across the Midwest United States to capture and permanently sequester their CO2 emissions.
Cory Reed, President, Agriculture & Turf Division of John Deere, said: "Carbon neutral ethanol would have a positive impact on the environment and bolster the long-term sustainability of the agriculture industry. The work Summit Carbon Solutions is doing will be critical in delivering on these goals."
McKinsey highlights a number of CCUS methods which can drive CO2 to net zero:
- Today’s leader: Enhanced oil recovery Among CO2 uses by industry, enhanced oil recovery leads the field. It accounts for around 90 percent of all CO2 usage today
- Cementing in CO2 for the ages New processes could lock up CO2 permanently in concrete, “storing” CO2 in buildings, sidewalks, or anywhere else concrete is used
- Carbon neutral fuel for jets Technically, CO2 could be used to create virtually any type of fuel. Through a chemical reaction, CO2 captured from industry can be combined with hydrogen to create synthetic gasoline, jet fuel, and diesel
- Capturing CO2 from ambient air - anywhere Direct air capture (DAC) could push CO2 emissions into negative territory in a big way
- The biomass-energy cycle: CO2 neutral or even negative Bioenergy with carbon capture and storage relies on nature to remove CO2 from the atmosphere for use elsewhere