Volcanic Ash: Efficient and Budget-Friendly Solar Storage

When a region finds itself covered in volcanic ash, it’s usually not a positive development. However, researchers from the University of Barcelona have uncovered a unique set of beneficial characteristics in volcanic ash, rendering it remarkably valuable as an energy storage medium.

We’ve discussed both incredibly affordable thermal energy storage solutions and remarkably efficient heat batteries operating at extremely high temperatures on multiple occasions.

Volcanic Ash as a Middle Ground

The most economical of these utilize abundant materials, while the most effective can withstand exceptionally high temperatures employing substances such as liquid tin and carbon materials. However, volcanic ash presents a potential middle ground, offering a balanced option that may be just right for specific applications.

The primary focus of a recent study in the Journal of Energy Storage is concentrated solar power, distinct from photovoltaic panels. This entails the use of towers surrounded by extensive arrays of parabolic mirrors in desert landscapes, meticulously positioned to accurately track the sun’s movement and concentrate its rays onto a central point.

Currently, these concentrated beams produce immense heat, frequently exceeding 1,000 °C (1,832 °F) – akin to magnifying glass heat on steroids.

Options for Utilization and Storage

This heat can serve a dual purpose: either directly converting it into electricity, often through a steam turbine, or storing it for future use by heating a thermal battery. Many installations opt for molten salts due to their efficient heat storage and recovery capabilities at high temperatures.

However, molten salts come with notable drawbacks; they can be highly corrosive, damaging equipment and shortening the lifespan of installations. Moreover, they can be costly to produce and may solidify at lower temperatures, complicating handling processes.

Introducing volcanic ash. When a single volcano erupted on La Palma Island in the Canary Islands in 2021, it blanketed the surrounding area with an enormous 200 million cubic meters (equivalent to 7.06 billion cubic feet or 80,000 Olympic swimming pools in standard measurements) of igneous rock and ash debris.

Investigating Volcanic Ash as a Heat Storage Solution

This resource is abundant, as volcanic ash is commonly used in civil engineering projects for its cost-effectiveness. However, the researchers from Barcelona aimed to explore its potential as a heat storage medium. To do so, they compressed the ash into pellets and subjected them to repeated heating and cooling cycles between 250 and 750 °C (480-1,380 °F) over 1,000 iterations.

The researchers discovered that the volcanic ash demonstrated remarkable thermal conductivity and heat capacity while maintaining its physical and chemical stability, showing only a 0.54% increase in mass due to oxidation over the thousand cycles.

Enhancing Molten Salt Systems with Volcanic Ash

Moreover, they observed that volcanic ash could effectively complement molten salts. When mixed with molten salts, the ash could reduce the corrosive impact of the salts and also store sufficient heat to prevent their tendency to solidify, all at a low cost. Alternatively, when kept separate in tanks utilizing molten salts for heat transfer, the ash could still perform this function almost as effectively.

Volcanic Ash in Direct Solar Energy Conversion

Additionally, volcanic ash proves suitable for use as a direct “open receiver” setup, where concentrated solar beams are directed at a structure constructed from the ash. This configuration enables operation at extremely high temperatures and facilitates highly efficient conversion of heat into electricity.

According to the researchers, “Volcanic ash from La Palma Island has enormous potential as an alternative and sustainable material for application in the thermal energy storage (TES) field… Providing cost-effective solutions and potential savings in energy storage.”

Read the original article on: New Atlas

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