In this dissertation, an energy harvesting system based on solar and wind energy is proposed for the structural health monitoring applications. The proposed system consists of two main components, which can harness the solar and wind based energy respectively. The combination of these two components makes it possible to harvest the natural energy on the days when either of the energy sources are not available due to weather conditions.
Firstly it is proposed to use highly efficient thermoelectric (TE) system to harness the abundantly available and not tapped at large solar thermal energy. In order to enhance the efficiency of a thermoelectric (TE) energy harvesting system, a thick graphene layer was used. This is a simple and effective way to widen the temperature difference across a conventional TE module by improving heat dissipation on the cold side of the system. Aqueous dispersions of graphene nano sheets were used to prepare a 112- $\mu m$ thick graphene layer on the cold side of the TE system with aluminum as the substrate material. The maximum efficiency of the proposed system was improved by 25.45 %, as compared to the conventional TE system, which does not have a graphene layer. Additionally, the proposed system shows very little performance deterioration (2.87 %) in the absence of enough air flow on the cold side of the system, compared to the case of the conventional system (10.59 %). Hence, the proposed system, when coupled with the latest research on high performance TE materials, presents a ground breaking improvement in the practical application of the TE energy harvesting systems.
Secondly in order to harness the second major energy source i.e., the wind energy it is proposed to be harvested by coupling of wake galloping phenomenon and piezoelectric material based cantilever beam. Wake galloping phenomenon is known for reasonably constant vibrations after certain wind flow velocity. It is proposed to use two cylinders with the downstream cylinder mounted on a cantilever beam which contains Macro Fiber Composite (MFC)films. The proposed system is reliable is a sense that it provides reasonable energy at the lower wind speeds and also can be a stable structure even at reasonably high wind velocities. In the proposed system, two cylindrical bodies are placed with wind flowing parallel to them, and the downstream cylinder is placed on top of a unimorph cantilever beam with piezoelectric film attached to it while the upstream cylinder is fixed at one end. A wind tunnel test was considered to validate the effectiveness of the proposed system. The tests were carried out for wind speeds up to 10 m/s and for several cylinder spacing values. The results show that the optimum spacing of two cylinders is 3D and the cut-in speed is determined to be 4 m/s. The proposed system was found to be effective at the optimum spacing and the wind speeds higher than 4 m/s.
본 논문은 구조물 건전도 평가를 위한 태양 전지, 풍력 에너지 기반 에너지 수확 시스템을 제안하고자 한다. 제안된 에너지 수확 시스템은 태양에너지 와 풍력에너지를 이용한다. 두 에너지 시스템의 조합을 통하여 기상악화로 인한 에너지 공급이 어려운 상황에서 에너지 수확을 가능하게 할 수 있다.
먼저 대형 태양열 발전에 자주 활용되고 풍족하게 사용 가능한 고효율 열전 (TE) 방식을 제안하고자 한다. 열전 (TE) 에너지 수확 시스템의 효율을 향상시키기 위해서, 얇은 그라핀 층을 사용 하였다. 이 방법은 시스템의 열 소산 방법을 개선함으로써 기존의 열전 모듈의 온도 차이를 증진시키는 간단하고 효과적인 방법이다.
다음으로는 풍력에너지와 같은 주요 에너지 공급원을 활용하기 위해서, 웨이크 갤로핑 현상과 외팔보 기반 압전 재료의 결합에 의해 수확 할 것을 제안한다. 이는 두 개의 실린더를 사용하며, 매크로 섬유 복합 (MFC) 필름을 포함하는 외팔보에 장착 된 하향 실린더를 함께 이용한다. 제안 된 시스템은 낮은 풍속에서도 만족할만한 수확 에너지를 제공하며, 큰 풍속에서도 안정된 구조물의 상태를 나타내기 때문에 신뢰할만한 결과를 나타냄을 알 수 있다.
