Table 1 Recent advances in PEH technology for roadways

A stacked configuration of transducers

Not reported

Able to support loadings up to 150 kN and remained effective after 100,000 cyclic loadings

Yang et al. [47]

Stacked units including U-shaped interlayer copper foil electrode structure

Output power: 22.8 mW at a resistive load of 20 kΩ, under 0.7 MPa (compression loading) and 10 Hz (vibration frequency); output voltage: 28.0 V

Stable performance after 50,000 simulated cyclic loading, with attenuations of: open-circuit voltage by 4.4 V, output power by 3.3 mW

Wang et al. [48]

Bridge transducer with layered poling and electrode design

Output power: 2.1 mW at a resistive load of 400 kΩ, under 0.07 MPa, 5 Hz; output voltage: 556 V

Balanced the desire for improved energy output and the need for less risk of stress concentration

Jasim et al. [49]

Several PEH prototypes to be embedded into asphalt pavement

Output power: >  25 mW under 15 MPa (for each piezoelectric element) and 10 Hz; output voltage (nearly 20 V) and output current (>  100 μA) at a load of 3 kN

Higher frequency “represents higher traffic speed and greater traffic volume” (e.g., on Interstate highways), and leads to better output power.

Roshani et al. [46]

One layer of “piezoelectric elements with a higher piezoelectric stress constant” and two layers of “more flexible conductive asphalt mixtures”

Output power: ranging from 1.2 mW to 300 mW at 30 Hz

The cost of electricity produced by this PEH can be as low as “$19.15/kWh at a high-volume roadway within a 15-year service life”.

Guo and Lu [44, 45]

A 100-m piezoelectric pavement with packaged multi-layer transducer

Output power: up to 231 mW (0.58 J), under 0.7 MPa

Under the daily traffic volume of 15,100 vehicles, this 100-m pavement can produce up to 1.93 MJ (i.e., the energy needs of 35 mobile phones). The additional construction cost: approximately $57/m.

Cao et al. [50]