Unlike some renewable energy sources like solar and wind power, which can be harnessed by individual buildings, hydropower typically comes from massive dams. Historically, watermills were used for generating small-scale hydropower, but they need to be next to some kind of falling water and are relatively rare today.

Students from Universidad Tecnológica de México have proposed a building-scale hydropower solution, which could harness this energy in places without the large infrastructure of dams. Their new technology, called "Pluvia," is a micro turbine, a very small spinning wheel that fits within a half-inch diameter pipe, that is integrated into a house's downspout system. (The system is custom-built, so houses don't need to have an existing downspout system.) Rain is collected and stored, then pumped to the micro turbine. When the turbine spins, it generates a current and delivers useable electricity. 

But according to IEEE Spectrum, the pump mechanism currently needs more power than the turbine generates. The system recharges the batteries after the pump electricity is factored out of the equation. In other words, the system would not power anything without the pump.

While this tiny turbine can only power portable 12-volt batteries, enough to run LED lamps, even a little bit of light is likely welcome for families without access to affordable, reliable electricity. So far, Pluvia has been tested in Mexico City's Iztapalapa community.

Pluvia also includes activated charcoal filters, which cleans roof runoff. According to designer Omar Enrique Leyva Coca, a recent test produced water of an equal or higher quality to Mexico City drinking water. Most North American guide books recommend boiling the water or drinking bottled water in Mexico. Regardless of the potability of this water, cleaning gray water that runs off a roof, where it gathers pollution and dust, to a quality level that is above tap water is notable—even if it doesn't quite rise to the standard Americans feel safe drinking. 

The concept is a creative deployment of "micro" hydropower, and could aid less-advantaged families with a simple and easily deployable energy source. Again, the power generation for Pluvia is very low. Like many off-grid renewable technologies, this might catch on in poor communities where any amount of power is a plus (for charging cell phones, LED lights, etc.) and there are funding sources that help with installation. Otherwise, the return on investment is minimal.

I agree with the IEEE Spectrum article: This research is valuable as a start. Even though it is impractical at this point, there are other ways to make it work, such as by providing integral rooftop photovoltaics or wind energy to power the pump, or developing a more energy-efficient micro turbine (or both). These strategies will add more to the installation cost, but as technology improves, could still lead to beneficial outcomes.

Blaine Brownell, AIA, is a regularly featured columnist whose stories appear on this website each week. His views and conclusions are not necessarily those of ARCHITECT magazine nor of the American Institute of Architects.