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Cryo-desalination – A nature inspired solution to obtain freshwater

New water innovations are needed to secure freshwater supply for human use, even in the Nordics that are typically perceived as water secure nations. Cryo-desalination, also known as freeze-melt desalination or freeze-thaw desalination, allows to obtain fresh water by freezing seawater. Is that even possible, how energy efficient is it and why is it not implemented yet?

In pursuit of new methods to obtain freshwater
Global availability of clean water is one of the Sustainable Development Goals set by the United Nations for 2030. The rise of global temperatures due to climate change is a major problem impacting every continent and threatening the ability to secure SDG 6. In many parts of the world the water footprint has already exceeded sustainable levels, whereas due to the global dimension of water consumption, many countries have significant impact on water consumption and pollution elsewhere. Looking into the future, it is important to think creatively about the types of innovations that will form tomorrow’s toolbox for securing not only water but also the health of ecosystems. Desalination is a very attractive nature inspired solution for obtaining fresh water from the seawater, which comprises 97% of the water in the world and yet has a marginal role in human water consumption. Traditional desalination processes (e.g. thermal evaporation, membrane processes) despite having improved performance over the years, they still lack sustainability and have systemic problems (e.g. linked to pollutants and membrane fouling).

The sustainability potential of cryo-desalination as opposed to traditional desalination is higher if we consider energy demand over the entire process.  As the melting of ice takes approximately 7 times less energy than boiling water, cryo-desalination has the potential to be more energy efficient.  In addition, since this approach does not rely on any filters in it can be fully sustainable form the perspective of new materials usage as well.

What is cryo-desalination?
Cryo-desalination, the separation of water and salt upon freezing, utilizes the natural tendency of water to push out salt upon freezing. In practice, one utilizes energy to cool water and form ice. As ice is forming it expels most of the salt, resulting to the so called brine, which is very highly concentrated saltwater. Then the ice and brine are separated followed by the warming up of the remaining ice in order to obtain the fresh water.

Most of the energy required for the freezing and melting of ice can be recovered by an external thermal bath and coupling to a process that has excess cold energy such as liquid natural gas. Thereby, this technology can be applied equally to both cold and warm climates. The ice-brine separation is the critical step that defines the amount of seawater that can be obtained. There is a difficulty here though since during freezing salt and water mix down to microscopic level forming small brine pockets inside the ice. Understanding the water-salt separation mechanism could therefore be an important part of creating better technological solutions for cryo-desalination.

A schematic describing the steps in cryo-desalination (also known as freeze-melt desalination). Most of the energy required of the cooling and heating can be recycled, whereas the ice-brine separation limits the amount of fresh water that can be obtained.

 

 

 

 

 

 

 

From water molecules to societal mainstreaming
There is no doubt that cryo-desalination is an expanding field of innovation with potential to address challenges of water insecurity. Nevertheless, few initiatives bridge this fundamental understanding of water with implications of the technology for market and societal mainstreaming.

Importantly, we find that a more broadly defined interdisciplinary approach could be beneficial for advancing cryo-desalination. It could for example combine basic research at the molecular level, with engineering and the social sciences, and thereby attempt to explore new connections across different fields of knowledge, with water as the common element.  How might a molecular study of water become combined with insights from a social study of key water players in a growing city such as Stockholm to deepen insights about its feasibility?

A combination of field observations and interviews with water experts, energy and water utility companies but also business actors could provide a better insight into whether decisions about future investments in different water innovation portfolios can include more radical solutions. We know that insights from basic research such as from theoretical physics are crucial for solving complex water questions at the molecular level, but how could we further couple these investigations with other important fields of study?

Creating a safe space for new partnerships
Entering the recent Skolar Award competition which took place in Finland has been an incentive to push ourselves to think outside the box.

As water researchers ourselves (from theoretical physics and the social sciences), we have entered what might at times feel like an uncomfortable partnership. Because of the distance, we sometimes feel between our own disciplines. Moving forward however, we are excited to explore how this new partnership around cryo-desalination could provide a platform for asking a different set of questions around water that joins insights from molecular and societal perspectives.

Foivos Perakis
Assistant Professor at Stockholm University.
Timos Kaprouzoglou
Researcher, Division of History, Science, Technology and Environment, KTH.
Research coordinator of the WaterCentre@KTH.

Water scarcity on islands: how to stage and navigate collective learning

There I was on the island Vis far out in the Croatian archipelago, surrounded by beautiful turquoise water to participate in a workshop about water shortage on small European islands arranged by the Water Saving Challenge Project. Once again the same ingredients; a wicked problem, a diverse group of knowledgeable actors and the tension between holistic ambitions, and specific and localized solutions – they seem to attract my attention. Collaboration, cross-sectoral dialogues and broad participation are argued for as key measurements in almost all sustainable development policies. This seems logical given that the present complex challenges require combination of a diversity of knowledge, and multi-scale and multi-sector approaches. However, I think we have all been participating in too many workshops, discussing challenges, barriers and potentials, with a nagging feeling that it is not enough for the needed societal  transformation. I was curious to find out if the workshop at Vis could be different.

The setting and process leadership are keys for successful collaboration and learning

Shortage of water is one symptom of our inability to handle water as a wicked problem, which has become an everyday reality for the inhabitants on many small islands. The task for the group of islanders gathering on Vis in September was to identify strategies to re-match water use with water availability but without losing sight of other important values such as a viable tourism providing jobs and income or local food production. What new ways of thinking, organizing and doing are needed to transform the water governance and how can the islands help each other?

Our process leader Christian Pleijel from the Kökar Island in Åland, works at KTH Executive School and is also the vice president of the European Small Islands Federation, used two tools to facilitate the discussions. The Ishikawa fish bone is designed to identify causes building up to a certain effect – in our case to identify all aspects of importance to achieve a water saving effect. The fishbone was combined with a method for parallel thinking by the use of six thinking hats developed by Edward de Bono. The thinking hats is a way to look at a certain issue from one direction at a time – the white hat as fact based and neutral, the red hat emotional, the black hat cautious, the yellow hat optimistic, the green hat creative and the blue hat organization. I had not before experienced these tools and looked forward to learn more about their potential.

However, what I soon discovered is that these are just yet another set of tools and with many similarities with tools that I have used or experienced in various collaborative processes before. It is not the tools that make a workshop contributing to real learning and change, it is the setting in which they are operationalised. What made this workshop a collective learning about island water saving was the stage, the actors and the process leader that used the tools.

The stage was very carefully designed based on extensive field studies on each of the eight islands represented. These field trips were as much about investigating the present water situation on respective island, as they were about establishing relationships and building trust that enabled the islanders’ engagement in the knowledge exchange and their support of a collective learning community. Furthermore, the stage is not just about what happens in the sessions which usually have a clear structure, roles and goals, but what happens in-between the sessions, during field-trips, coffee breaks and dinners. This is when new relationships are established that are necessary for future remote collaborations to be successful.

The importance of the space between sessions in a workshop. This is when relationships are built and long term learning partnership can start. A much appreciated visit to the Vis Island water center.

The actors also need to trust the process leader and each other in order to fully contribute to the joint process – the workshop play. Christian is himself an islander with personal experiences about what it means, combined with a long career working with people, leadership, innovations and businesses. In order to address wicked problems a diverse set of knowledge needs to be combined, demanding the process lead to be like a chameleon when interacting with this diversity. Like a director of a play you need to know when to start, stop, go back, fast forwarding by tweaking the tools so they are as purposeful as possible in relation to the process dynamic.

In the end fish bones covering many aspects of the water saving challenges on each island was drawn and the participants had been cautious, creative and emotional along the way with a strong foundation in facts and possible interventions in terms of governance. But, most importantly it was decided that this workshop was just the beginning of a more long-term exchange between the islands and that they will become learning labs to support a larger network of islands in the future.

What I bring with me from the three days with great islanders from all over Europe is that a workshop that enable not just knowledge exchange but real learning, needs to be carefully designed as part of a larger setting and requires deep skills in how to set a stage, encourage actors and use the right tools in the right moment. This might be common sense in other sectors but within sustainable development there is a clear need to highlight and develop skills in process design, leadership and facilitation so that we can move away from disappointing efforts of collaboration into meetings that enable societal transformation.

Sara Borgström

Assistant Professor, Strategic Sustainability Studies

KTH Royal Institute of Technology

 

Readings:
How to read an island by Christian Pleijel
Six thinking hats by Edward de Bono
Att leda samverkan: En handbok för dig som vill hantera komplexa samhällsutmaningar by Martin Westin, Camilo Calderon och Alexander Hellquist.