As anyone knows who has changed a tire along a busy roadway, an incredible amount of turbulence is created by airflow over and around passing vehicles. This turbulent air is an untapped, kinetic-energy resource; though, it is difficult to harness due to the chaotic intensity and irregular vectors of the energy. A system—HEAT—is proposed to convert this turbulence into useful electric current. This “free” energy source can offset costs of electrical needs such as lighting of roadway features, facilities, or operating systems. Public benefits will accrue from reduced operating expenses for transportation systems as well as improved safety and security from expanded lighting along roadways.
The HEAT system consists of multitudes of “swirlers” which will flex, bend, and sway, as they are affected by the turbulence from passing vehicles or from ambient winds. The “root” of the swirler is anchored in a flexible, piezoelectric substrate which produces current as it stresses the piezoelectric substrate. Electric current is generated as the swirlers move in response to the turbulence. Each array of swirlers are connected to a common circuit, where the current is used and/or combined with current from other swirlers. Small amounts of current generation from each swirler, when multiplied, will create a significant current that can be used immediately or stored.
The HEAT swirlers are small and thin: approximately 5 cm long and 5 mm in diameter. Individual swirlers must have physical attributes that allow stiffness, flexibility and mass to generate sufficient deformation in the piezoelectric substrate as the swirlers respond to turbulence. Different swirler designs may be required depending on the intensity of the turbulence flow (see Figure).
Since the HEAT system will be situated near busy roadways, there will be a fairly constant supply of turbulent energy. In tunnels, for example, the HEAT system might be applied around the upper circumference using multiple, connecting strips on the walls and ceiling to maximize turbulence-scavenging capability. The generated direct current along each strip is transformed, and combined to operate lighting, ventilation fans, or other applications. Any excess electrical current generated would be stored in battery systems or could be returned to the electrical grid. It is expected that the capital investment in a HEAT system in most applications would be returned within three to five years.
The HEAT system combines reliable, available components with modular design to reduce production and life-cycle costs. Swirlers are fabricated with proven (e.g., piezoelectric) and inexpensive materials (e.g., carbon fiber). The swirlers use interlocking modules so that they could be removed and replaced; this attribute will allow mass production and reduced cost. Different HEAT system designs may be required depending on site-specific environmental, weather conditions (e.g, icing), or other requirements. Testing and development may be necessary to “optimize” design and performance of the HEAT system to maximize energy production at each site. For example, the distance between the attachment points of the swirlers may differ according to concerns of debris, levels of turbulence and environmental factors.