Clean energy started to have a great importance with the increasing population. In 2020, 330 billion 443 million 840 thousand kilowatt-hours of energy consumption and battery consumption waste cause great damages to nature. In addition, the electronic devices have a trend to be smaller, portable and wearable. Triboelectrification based electrical energy harvesting could meet the criteria of producing clean energy and being small, portable and wearable. In this paper, triboelectric energy harvester (TEG) has been designed and one of its application presented. Here, designed energy harvester has a foldable structure and has been produced with a low cost and straight-forward method. The working principle of the triboelectric energy generator is based on the travelling of electrons between different materials where they have opposite tendency to gain or lose electrons when they are in contact. When two material surfaces are subjected to physical contact and separation process, they yield to opposite surface static charges. Once the device is compressed, one surface is charged negatively and the other one is positively. When they are separated, due to high tendency of conductors attaining charge equilibrium, the electrons flow from ground to conductor or vice versa to make it neutral. Based on this energy harvesting mechanism, our aim is to design a device that works with triboelectric effect principle and provide the highest energy gain within the framework of the dimensions determined depending on the application. In line with this purpose, the design of the TEG, the material selection and the design of rectifier circuit were conducted to make the harvested energy usable for possible applications. In this paper, as an application of the energy harvester device, multiple TEG were connected parallel to each other to form a door mat and this mat was placed in front of the library entrance to track the number of people in the library to track the occupancy rate by hourly, daily, monthly and annually. The tracking of this information becomes crucial due to Covid-19. Therefore, the occupancy of the indoors like library could be tracked with the integration of this device at the entrances.