July 5, 2018
Finding Nature-Inspired Solutions for Energy Use Design Challenges in Engineering and Architecture
By Peter Dean
Unfortunately, many engineering solutions to both past and current architectural and industrial design challenges have relied on abundant and cheap energy for their effectiveness. When energy is cheap and plentiful, using increased amounts of horsepower is a seductive default position when designing industrial systems and processes.
A problem the University of California at Davis (UC Davis) experienced with a drinking water reservoir in 2005, involving a one-million-gallon open-air surface reservoir, serves as an instructive example. The water in the reservoir came out of the ground cold and would then striate as it got closer to the surface, with the temperature ultimately becoming warm enough to promote and support algae growth. The algae would then die off and decay, creating biological oxygen demand (BOD) in the decaying process, thus removing oxygen from the water. This resulted in algal blooms, which are not always benign, they can be toxic as well. In this case, it led to an objectionable taste.
A conventional treatment for such a problem at the time was to add chemicals to the water to kill the algae, a solution which required repeated applications of the chemicals, similar to the treatment for algae in swimming pools. These chemicals usually rely on chlorine, which also spoils the taste of the water and would cause an adverse reaction from the university community.
Another conventional engineering solution was to retrofit the reservoir with a mechanical system, which would require draining the reservoir, installing perforated pipes along the bottom of the tank, and connecting these to compressors that would pump air through the pipes. The bubbles would then rise through the water in the reservoir, mixing it and hopefully yielding a temperature unconducive to algae growth. The downside of this design strategy was that it required draining one million gallons of drinking water and taking the reservoir offline during installation and testing. These downsides, in addition to carrying costs, mechanical maintenance, and electrical power that the compressors would continually require would have led to an increasingly large carbon footprint.
However, there was another option. Jay Harman, founder and CEO of Pax Scientific was contracted to explore another design/engineering strategy to address the need to mix the one million gallons of drinking water. His company came up with a technology called the “Lily Impeller,” a biometric design strategy. Harman demonstrated the technology by filling a clear tank of water approximately three feet in diameter with water to a depth of four feet. Suspended in the water were neutrally buoyant day-glow green balls about a quarter inch in diameter. The “Lily Impeller” was inserted just below the surface, and Dr. Harman turned on the small electric motor and, after a moment, there emerged from the bottom of the impeller a perfect vortex extending to the bottom of the tank. All of the day-glow green balls could then be seen circulating from top to bottom of the water in the tank.
Harman’s impeller design was inspired by the form of a Calla Lily. Natural organisms, plants, and animals grow in proportional patterns that are optimally efficient, and mimicking these patterns and proportions yields forms that behave in similarly efficient ways. The project team at Pax attached the Lily Impeller to a 24-watt electric motor and affixed this to a floating structure similar to a life-ring, with the impeller submerged eight inches into the water. This structure was then fitted with a 32-watt solar collector and the entire assembly was floated onto the surface of the drinking water reservoir. Twenty hours later, all one million gallons were homogenized to a temperature below what would support algae growth—a feat that was accomplished without using a drop of fossil fuel, instead using just a single moving impeller with a biomimetic inspired shape. In addition, it was accomplished without any decrease in water quality or disruption of the delivery of drinking water to the UC Davis campus community.
The cost efficiencies achieved were significant and self-evident. There are now hundreds of these “Lily Impellers” mixing all manner of fluids all over the country.
As a design strategy, biomimicry presents the designer with time-tested solutions found in nature that are characterized by elegance, efficiency, and often unforeseen ancillary benefits when applied to conventional human design challenges.
Another example of the application of biomimetic-inspired design comes from Sweden. Twenty years ago, architect Anders Nyquist was commissioned to renovate a 1930s-era primary school and design a new addition to double the size of the facility. The school, home to 135 students, is located in Laggarberg, Sweden, 400 kilometers south of the Arctic Circle. The ventilation system that Nyquist designed for the school is inspired by the structures that termites build to ventilate their nests and keep their queen comfortable and happy.
Termites build their mounds, which can reach fifteen to twenty feet, in response to ambient temperature and humidity. While the termites do not live in these mounds, they serve as ventilation chimneys for the termites’ underground home, as the soil temperatures two meters below ground is roughly fifty-five to sixty degrees. The termites create tunnels from the surface to cool soil, and the tunnels feed into the chimneys in the above-ground mounds. Simple convection powered by the sun draws the ambient air off the surrounding land into the cool soil and ventilates it up and out through the chimney. This is a solar-powered air conditioning system in the summer and a preheating system in the winter.
Using this example from the natural world, Nyquist designed a ventilation system that turns over the entire internal air volume in the school building every half hour without the use of any electric fans, and without a single moving part, resulting in substantial savings of energy and money. The most interesting ancillary benefit is that the students and teachers of the school reportedly enjoy the lowest absentee rate of any school in Sweden and the highest student performance in science and math. Families move to Laggarberg from all over Sweden so that their children can attend this school. Fresh air is powerful.
As winters in Laggarberg get very cold, a reliable source of heat is crucial. Sweden is largely a forest economy, producing wooden building materials. A primary waste material produced from that industry is sawdust, which is carbon-based and combustible. At the Laggarberg School, the sawdust is pelletized, delivered to a silo, and fed into a furnace with an Euclidean screw. Up-cycling waste into a resource is another example of an anti-entropic behavior, as discussed in the first blog post in this series.
Why mention these two examples of Biomimicry inspired design?
The built environment is responsible for approximately 40 percent of the greenhouse gas emissions in the United States wreaking havoc on the global climate system. The financial investment and embodied energy contained in existing building stock are monumental and the commitment to adapt and reuse these buildings following a low/no carbon design ethos will be, by necessity, equally monumental. The fact remains that these biomimetic design adaptations are real and they work, often with unforeseen added benefits.
Learning to be good stewards of the resources we have is the “great work” before us. This is not the work we choose, but the work that is thrust upon us, and let us get started in earnest.
Peter Dean is a senior fellow at the Atlantic Council Global Energy Center.