What if I told you there is a clean energy technology that turns hot air into electricity, even after the sundown? This idea might sound like something straight out of science fiction at first. But humans have been using the same principle, called chimney effect, to cool down their houses for centuries. Solar updraft towers (SUT) are one of the promising renewable energy technologies that could help us to eliminate fossil fuels.

Solar updraft towers consist of a rather simple structure: a large collector area, a long cylindrical chimney and turbines. Sun warms up the air under the large glass or plastic roof, then that hot air rises to the top (chimney effect) thus, creating a constant air flow that drives the turbines. The whole process can be explained coherently in a single sentence. In fact, it is so simple that you can build your own small SUT using tin cans. 

Environmental and economic advantages:

Solar updraft towers use sunlight to generate electricity, which means there is an unlimited resource. It does not release greenhouse gas, soot or other toxic elements to the atmosphere. It shares all the benefits of any other renewable energy technology, but most importantly SUTs don't need cooling water like fossil plants or cleaning water like solar panels. Water is not a resource that can be easily found in the desert area, so it makes SUTs even more 'environment friendly'.

The large area under the collector is basically a huge greenhouse. With a few adjustments, collector area can be turned into a farming land, which would increase its economic efficiency as well as provide for the people living in that area.

As mentioned above, solar updraft towers can generate electricity even without sunlight. Energy storing can happen by placing few water tubes under the collector area. During the day, water collects and stores some of the heat from hot air, and releases it when the collector cools down.

Solar panels only convert direct radiation, which means that their efficiency level drops significantly when the sky is cloudy. On the other hand, SUTs can use both direct and diffuse solar radiation, and not affected much by the climate conditions.

Unlike solar panels, which lose much of their energy when covered by a thin layer of dust, SUTs can work in dusty desert environments where the sunlight is most abundant. They continue to work even after the sundown using the heat absorbed by the land. Besides, the technology and main principle is much simpler than any other power plant we are using today, making it possible to be built without investing in high-tech manufacturing.  

Then why aren't SUTs widely used?

The main problem that we are facing today is the funding. In order to work efficiently, solar towers need to be built in large scales, thus raising the production cost. Investors avoid of this kind of project because it was not tested widely in the past. The only prototype ever built was in Spain. Despite the fact that it over exceeded its test period for almost 7 years, no successful SUT has been built since 1982. But the increasing cost of fossil fuels due to their decreasing resources, building Solar updraft towers will eventually become cost efficient in the near future.

Humanity has long been dreaming about maintaining a stable energy resource and many people thought nuclear energy was the one dystopian endless energy supply. Although, bigger threats such as global warming makes us reconsider our choice, and turn into cleaner resources, rather than cheap ones. Combined with other renewable energy technology, solar updraft towers most certainly can be part of the solution.