Minki Kim

Wearable thermoelectric generator for harvesting human body heat energy

This paper presents the realization of a wearable thermoelectric generator (TEG) in fabric for use in clothing. A TEG was fabricated by dispenser printing of Bi0.5Sb1.5Te3 and Bi2Se0.3Te2.7 in a polymer-based fabric. The prototype consisted of 12 thermocouples connected by conductive thread over an area of 6 × 25 mm2. The device generated a power of 224 nW for a temperature difference of 15 K. When the TEG was used on the human body, the measured output power was 224 nW in an ambient temperature of 5 °C. The power of the TEG was affected by the movement of the wearer. A higher voltage was maintained while walking than in a stationary state. In addition, the device did not deform after it was bent and stretched several times. The prospect of using the TEG in clothing applications was confirmed under realistic conditions.

Estimation of Lateral Load Capacity of Rigid Short Piles in Sands Using CPT Results

Conventional methods for the estimation of the ultimate lateral pile load capacity are typically based on certain expressions of the lateral soil resistance pu and assumed distributions of the lateral soil pressure mobilized along the pile embedded depth. When soils are nonhomogenous, however, the application of conventional methods represents significant difficulties due to the nonlinear and irregular variation of pu with depth. In this study, a cone penetration test (CPT)-based methodology for the estimation of the ultimate lateral pile load capacity Hu was proposed, which can take full account of entire soil profile through the CPT cone resistance qc . A normalized correlation between qc and pu was proposed with correlation parameters corresponding to different existing methods. In order to validate the proposed CPT-based methodology, case examples of laterally loaded piles in various soil conditions were prepared and used to compare values of Hu from original and proposed methods. Calibration chamber ...

Triboelectric–thermoelectric hybrid nanogenerator for harvesting frictional energy

The triboelectric nanogenerator, an energy harvesting device that converts external kinetic energy into electrical energy through using a nano-structured triboelectric material, is well known as an energy harvester with a simple structure and high output voltage. However, triboelectric nanogenerators also inevitably generate heat resulting from the friction that arises from their inherent sliding motions. In this paper, we present a hybrid nanogenerator, which integrates a triboelectric generator and a thermoelectric generator (TEG) for harvesting both the kinetic friction energy and the heat energy that would otherwise be wasted. The triboelectric part consists of a polytetrafluoroethylene (PTFE) film with nano-structures and a movable aluminum panel. The thermoelectric part is attached to the bottom of the PTFE film by an adhesive phase change material layer. We confirmed that the hybrid nanogenerator can generate an output power that is higher than that generated by a single triboelectric nanogenerator or a TEG. The hybrid nanogenerator was capable of producing a power density of 14.98 mW cm−2. The output power, produced from a sliding motion of 12 cm s−1, was capable of instantaneously lighting up 100 commercial LED bulbs. The hybrid nanogenerator can charge a 47 μF capacitor at a charging rate of 7.0 mV s−1, which is 13.3% faster than a single triboelectric generator. Furthermore, the efficiency of the device was significantly improved by the addition of a heat source. This hybrid energy harvester does not require any difficult fabrication steps, relative to existing triboelectric nanogenerators. The present study addresses a method for increasing the efficiency while solving other problems associated with triboelectric nanogenerators.

Power generation of a thermoelectric generator with phase change materials

In this paper, a thermoelectric generator that embeds phase change materials for wasted heat energy harvesting is proposed. The proposed thermoelectric generator embeds phase change materials in its device structure. The phase change materials store large amounts of heat energy using the latent heat of fusion. When the heat source contacts the thermoelectric generator, dissipated heat from the heat source is stored in the phase change materials. When the heat source is removed from the thermoelectric generator, the output power of the thermoelectric generator slowly decreases, while the output power of conventional thermoelectric generators decreases rapidly without the heat source. The additional air layer in the proposed thermoelectric generator disturbs the heat dissipation from the phase change materials, so the thermoelectric generator can maintain the power generation for longer without a heat source. The experimental results for the thermoelectric generator fabricated clearly show the latent heat effect of the phase change materials and the embedded air layer.