When exposed to visible light, iron oxide (more commonly known as rust) produces a small electrical current. The energy that this creates also has the potential to be easily stored and used on demand. The ability to both produce and store energy means that rust may emerge as something of a ´super material´ in the quest to achieve affordable solar energy for all.

To date designers have been largely ambivalent towards rust as a material – with many viewing rust as a material to be left in the scrap yard. Others have chosen to feature the vivid orange colour and materiality of rust prominently in their designs. The Kraton 230 building in Rotterdam by Mei Architecten is an example of this, with a façade composed of rusting iron panels, juxtaposed with sleek dark glazing. In the United States, rust has been used deliberately as a design strategy to give buildings in regenerated neighbourhoods a patina or weathered appearance that recalls formerly industrial surroundings. Sometimes referred to as ´rust belt chic’, this trend has caused some to question the authenticity of using rust to re-capture the material feeling of an industrial age from the past.

However, the unique solar energy generating properties of rust may move the debate about rust as a material beyond a question about aesthetics or the authenticity of building materials. One particular challenge with the use of solar energy is that it can only be used at the moment it is generated. As a result, a way to store the energy created is essential so that it can be used when the sun is not shining. Batteries are a common solution. However, their low energy-density and cost of fabrication and replacement mean that solar energy has been a relatively expensive technology to date.

Rust offers an interesting alternative. While rust cannot compete with the efficiency of other materials, such as silicon, at turning sunlight into energy, rust is able to directly electrolyse water to make hydrogen, whereas materials such as silicon cannot. This is beneficial because hydrogen is a very versatile element. Not only is hydrogen able to store 170 times as much energy per kilogram as a standard lithium ion battery can, hydrogen can also be easily stored in fuel cells and burned to create energy on demand. Imagine households in the future using the energy generated from panels of rust to electrolyse their household waste water, creating their own source of hydrogen fuel as a result!

Rust also has an added advantage over other materials as there are nearly limitless amounts of the material sitting in landfills. It is also, of course, literally as cheap as dirt. This is important to the future viability of solar energy, as inexpensive ways to generate and store the sun’s energy are urgently needed. As author, academic and political scientist Bjorn Lomborg explains, ´We need to invest dramatically in green energy, making solar panels so cheap that everybody wants them. Nobody wanted to buy a computer in 1950, but once they got cheap, everybody bought them.´

In the future, we imagine large swathes of rust may no longer be seen only as a thing of aesthetic beauty (or blight depending on your position). We would rather see rust as a type of solar tapestry that generates renewable energy everywhere and anywhere.