The walls use hydrogel bubbles inside a ceramic framework. Image: IAAC.
Air Conditioning is not a particularly eco-friendly technology. Yes, it cools down the room you're sitting in, but the energy used (around 200bn kilowatt hours of power per year in the US alone) contributes to global warming. As the planet gets incrementally hotter, the effect will be depressingly self-perpetuating: hotter air will result in more AC usage, which will create more heat, ad infinitum.
To break this depressing cycle, architects from the Institute for Advanced Architecture of Catalonia in Barcelona are developing walls that cool themselves without the need for electricity.
The technology uses a substance called "hydrogel", which absorbs water and can swell to up to 400 times its original size. When the air around the hydrogel heats up, the water evaporates, which cools the air around the gel by around 5° Celcius. The mechanisms not dissimilar to the way our body cools itself down by evaporating water from the skins surface in the form of sweat.
To create a self-cooling wall, bubbles of the gel are inserted between two ceramic layers. Heres a diagram of the final prototype from the IAACBs blog:
This video from the team goes into more detail:
The hydroceramic walls can be used to either replace or supplement an AC system. The designers say that they could allow ACs to be set 4°C higher, which could cut power consumption by around 28 per cent and reduce carbon emissions on a standard AC unit by 56.5kg a month.
So far, the technology's still at prototype stage, but it should be on the market soon. If it takes off, the days of sky-high summer energy bills are numbered.