The Bio Intelligent Quotient (BIQ) building in Hamburg, Germany, is powered entirely by algae. It has been in operation since 2013 and is still going strong. Microalgae are incorporated directly into its walls, giving it a living "bio skin." The tiny plants grow in a secondary glass layer or shell on the sides of the building that receive the most sunlight. The bubbling green liquid is visible from both the interior and exterior of this unique structure.
"The [algae] are continuously supplied with liquid nutrients and carbon dioxide via a separate water circuit running through the façade," according to the Hamburg International Building Exhibition site. The heat energy created by the plants' photosynthesis is stored and used to warm the buildings' rooms and water. One resident estimates she saves close to € 1,000 annually on utility bills.
The algae are also periodically harvested and reused for the creation of biogas, food supplements, and in research or other applications.
quote source: https://www.iba-hamburg.de/en/projects/the-building-exhibition-within-the-building-exhibition/smart-material-houses/biq/projekt/biq.html