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Our daily infrastructure, safety, health and comfort relies on a continuous availability of electricity. Due to the volatile nature of electricity and the limited ability of storing electrical energy, it is challenging to implement changes and improve energy efficiency, conversion effectiveness and generator size and weight. In this regard, a wide range of sufficiently high, but currently unused, energy sources are available. Harvesting unexplored waste heat or abundantly available thermal energy sources such as industrial, solar, and geothermal waste heat and abundantly available heat from friction or the human body enables local powering of electronic device, extension of battery lifetime, and even provides accumulated base load power supplies, resulting in the recovery of otherwise unused thermal energy. For this reason, solid-state thermal to electrical energy conversion utilising the pyroelectric effect provides a convenient and direct way of converting temperature fluctuations into an electrical potential difference available for discharge. In this thesis, the nature and the principles of pyroelectric energy harvesting are presented in a complete review of materials, structures and devices for thermal energy harvesting applications, followed by a detailed experimental set-up providing reproducible experimental results under constant laboratory test conditions. Introducing contactless and harmonic temperature oscillations using a radiative heating lamp allows examination of energy harvesting devices and helps to develop an geometrical optimisation approach. For radiative heating, a meshed micro- size electrode structure on polyvinylidene difluoride (PVDF) improves the pyroelectric conversion efficiency. The here presented photolithographic manufacturing technique on a flexible substrate provides new device architectures resulting in a 1050 % higher energy trade off. Further electrode modifications involve a graphene-ink based black body radiation absorber on flexible PVDF. With graphene-ink, a laminate structure introduces piezoelectric activity in response to the change in temperature. The inherent need of temperature oscillations for pyroelectric energy harvesting requires an alternating heat flow. By linking the subject fields of heat transfer in oscillating heat pipes (OHPs) for high performance cooling, together with a pyroelectric energy harvesting device, the experimental system exploits a heat induced liquid-vapour transition of a working fluid as a primary driver for a pyroelectric generator.