• Tip-controlled local breakdown (TCLB) is a technique to 'drill' microscopic holes into membranes to improve the effectiveness of osmotic energy.
  • Osmotic energy, also known as blue energy, takes advantage of the energy released when solutions of different salinities mix.
  • These conditions occur in locations all over the world and improving the effectiveness of the technique could lead to an abundant source of renewable energy.

A new technique could enable the production of robust, high-performance membranes to harness sea water as an abundant source of renewable energy, researchers report.

Blue energy, also known as osmotic energy, capitalizes on the energy naturally released when two solutions of different salinities mix—conditions that occur in countless locations around the world where fresh and salt water meet.

The key to capturing blue energy lies in selectively permeable membranes, which allow only one constituent of a saltwater solution to pass through—either the water molecules or the dissolved salt ions—but not the other.

To date, large-scale blue energy projects such as Norway’s Statkraft power plant have been impeded by the poor efficiency of existing membrane technology. In the laboratory, researchers have developed membranes from exotic nanomaterials that have shown great promise in terms of the amount of power they can generate relative to their size. But it remains a challenge to turn these vanishingly thin materials into components that are large enough and strong enough to meet the demands of real-world applications.

In results recently published in Nano Letters, researchers have demonstrated a technique that may open the way to overcoming this challenge.

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Osmotic energy takes advantage of the energy released when solutions of different salinities mix.
Image: Nano Letters

“In our project, we aimed to remedy the inherent mechanical fragility problem while exploiting the exceptional selectivity of thin 2D nanomaterials by fabricating a hybrid membrane made of hexagonal boron nitride (hBN) monolayers supported by silicon nitride membranes,” explains lead author Khadija Yazda, a postdoctoral researcher in the physics department at McGill University.

To achieve the desired characteristic of selective permeability, Yazda and her colleagues used a technique called tip-controlled local breakdown (TCLB) to “drill” multiple microscopic holes, or nanopores, in their membrane. In an advance on previous research that focused on experimental prototypes with a single nanopore, the team was able to exploit the speed and precision of TCLB to prepare and investigate membranes with multiple nanopores in various configurations of pore size, number, and spacing.

“Our experiments on pore-pore interaction in nanopore arrays shows that the optimum membrane selectivity and overall power density is obtained with a pore spacing that balances the need for high pore density while maintaining a large extent of charged surface (≥ 500nm) surrounding each pore,” Yazda says.

Having successfully produced an array of 20 by 20 pores on a membrane surface 40µm² in size, the researchers say the TCLB technique could be used to produce much larger arrays.

“A natural next step for this research is to try scaling up this approach not only for large-scale powerplants but also in nano- or micro-power generators,” Yazda says.

What's the World Economic Forum doing about the transition to clean energy?

Moving to clean energy is key to combating climate change, yet in the past five years, the energy transition has stagnated.

Energy consumption and production contribute to two-thirds of global emissions, and 81% of the global energy system is still based on fossil fuels, the same percentage as 30 years ago. Plus, improvements in the energy intensity of the global economy (the amount of energy used per unit of economic activity) are slowing. In 2018 energy intensity improved by 1.2%, the slowest rate since 2010.

Effective policies, private-sector action and public-private cooperation are needed to create a more inclusive, sustainable, affordable and secure global energy system.

Benchmarking progress is essential to a successful transition. The World Economic Forum’s Energy Transition Index, which ranks 115 economies on how well they balance energy security and access with environmental sustainability and affordability, shows that the biggest challenge facing energy transition is the lack of readiness among the world’s largest emitters, including US, China, India and Russia. The 10 countries that score the highest in terms of readiness account for only 2.6% of global annual emissions.

To future-proof the global energy system, the Forum’s Shaping the Future of Energy and Materials Platform is working on initiatives including, Systemic Efficiency, Innovation and Clean Energy and the Global Battery Alliance to encourage and enable innovative energy investments, technologies and solutions.

Additionally, the Mission Possible Platform (MPP) is working to assemble public and private partners to further the industry transition to set heavy industry and mobility sectors on the pathway towards net-zero emissions. MPP is an initiative created by the World Economic Forum and the Energy Transitions Commission.

Is your organisation interested in working with the World Economic Forum? Find out more here.

Funding for this study came from the McGill Sustainability Systems Initiative (MSSI) Ideas Fund, the Natural Sciences and Engineering Research Council of Canada, the Discovery Grants Program, and the Fonds de recherche du Québec–Nature et technologies.