Phase-Change Energy Storage On Barge, On Thames, In London

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Energy storage is the key to feeding more wind and solar power into the grid, but the question is how to get all that stored-up renewable energy to someone who can use it. The same goes for recovering waste heat from industrial operations. UK firm Sunamp has come up with a unique solution that involves scavenging heat from one place and transporting it on water to another place, with the help of a new phase-change material that can last for 40,000 cycles or more.

A More Sustainable, Less Costly Phase-Change Energy Storage Solution

Phase-change materials absorb and release heat with every change, which is why they are of interest in the energy storage field. One challenge, though, is to come up with a material that can disassemble and reassemble without losing integrity.

Phase-change materials are not hard to come by. The melting and re-freezing of ice is a classic example, and ice-based systems can be used to store off-peak electricity for later use. Phase-change waxes and oils are also used in industrial applications and performance-type fabrics.

In terms of energy storage, though, commercial applications have proved limited. As described by Sunamp’s Materials Development Manager, Dr. David Oliver, phase-change bio-oils are expensive, which limits their application to high-value products. He notes that they also have low energy density and “questionable sustainability.”

“Add in the rather alarming fact that they are also combustible, and it was clear to Sunamp that there was a need in the market for a re-think,” Oliver explained in the company’s blog back in May of 2022.

A Long Lasting, High Energy Density Solution

Sunamp’s researchers spent years working with scientists at the University of Edinburgh in Scotland to find an alternative to industrial phase-change bio-oils. They are not giving away the whole game, but Oliver did drop some hints about the nature of Sunamp’s new phase-change material. Called Plentigrade P58, it can be thought of as a kind of futuristic ice composed of “water and salt hydrate syntheses,” along with other additives Oliver describes as  “game-changing.”

One of those additives is sodium acetate trihydrate, which sounds rather mysterious, but which is a common potato chip flavoring.

As for why one would want to make an energy storage material taste like salt-and-vinegar potato chips, that’s a good question. Along with other additives, the point is to formulate a high-performance, water-based solution that melts evenly and re-assembles itself into “the right crystal structure.”

“Our PCMs have an enviable high energy density, avoid costly or scarce components and there is no question over their sustainability as the salts are either mined, are by-products of the existing chemical industry or are simple commodity chemicals with diverse supply chains,” Oliver wrote.

As for the calculation of 40,000 cycles, that remains to be seen. Doing the math, that’s about 50 years of use, based on two cycles per day, which seems rather ambitious. Sunamp did not pull that figure out of a hat, though. The company based its findings partly on a high intensity X-ray analysis at the Diamond Light Source, the UK’s synchrotron facility.

Transporting Energy By Barge, On The Thames

Much has happened in the two years since that blog post. In the latest development, last week Sunamp announced the launch of a new consortium aimed at capturing waste heat from one of the biggest waste-to-energy facilities in the entire UK the Cory Riverside Energy plant on the River Thames in Belvedere, in East London.

Cory is yet another example of a pre-21st century firm adapting to a new era of resource recovery. The company got its start back in the coal trade of the late 19th century. The Riverside plant began operating in 2012 to handle nonrecyclable “black bag” waste. The waste-to-energy system also recovers metals, and the ash is repurposed for construction materials.

Since Riverside already receives most of its waste by barge, the idea of a waterborne energy storage solution was a natural one. The containerized energy storage solution takes up no space on the premises of the user because it just sits on a barge while charging up and discharging, too.

“At the discharge location a water pipe is run out along a jetty and draws heat from the batteries via an internal heat exchanger,” Sunamp explains.

“The Thames Mobile Heat Consortium will take heat from along the river — initially from Cory’s Riverside energy from waste (EfW) plant, located on the banks of the Thames in Belvedere — store it in Sunamp thermal batteries, and transport it via barge to major heat consumers, such as district heat networks,” Sunamp explained in a press statement.

Also involved in the consortium is the recently incorporated firm Sheen Parkside, which Sunamp describes as “an arranger of innovative low carbon infrastructure projects,” along with technical and maritime industry stakeholders.

The idea has already attracted a large-scale user. The Westminster City Council’s Pimlico District Heating Undertaking is said to be considering the system for its roster of 3,000 homes and 50 other buildings.

Sunamp’s energy storage solution would replace the gas boilers that currently supply the district. “Heat would be transported on two barges, each carrying up to 120MWh in 40 batteries, travelling 28km each way along the river,” Sunamp explains.

“Heat supplied on this basis has been modelled to provide heat at 12gCO2/kWh or lower, which is a substantial reduction compared to gas which is modelled at c.216 gCO2/kWh,” the company adds.

More Energy, Less Transmission Hassle

The Westminster barge-based energy storage project may sound like a one-off project, but Sheen Parkside co-founder and CEO David Carter points out that the UK “wastes a huge of amount of high-grade industrial heat, simply because it’s in the wrong place.”

Here in the US we know the drill. The juiciest wind and solar resources are often far from large-scale energy consumers, requiring new transmission lines. These can take years to get through the permitting process, if they ever do. In contrast, Sunamp estimates that it can set up the Westminster system within a year.

The company is already looking past London to tailor its system for riverside communities in other locations, so hold on to your hats.

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Image: Sunamp’s energy storage solution deploys a new, transportable phase change material that can be put on a barge and ferried to points of charge and discharge (courtesy of Sunamp).