For heating houses, greenhouses. In Iceland, located at the Arctic Circle, tropical fruits are grown in greenhouses all year round. And the capital of Iceland, Reykjavik, is the cleanest city in the world thanks to the use of geothermal waters (hot springs) for heating houses. There are no boiler houses in the city, which in other cities emit tons of soot and smoke.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.