Sustainable energy solutions for stand-alone IoT devices : Technical, environmental and economic assessment to find alternative technologies to power RecySmart and Single Sensor IoT devices

Abstract: This work is intended to provide a high-level assessment of energy solutions to power Internet of Things (IoT) devices. The criteria for the evaluation are technical, environmental, and economic. Different technologies will be covered with support from published scientific research and the market existing solutions. The analysis will be done for a particular case study but the followed steps should serve for others looking to tackle the same issue. The intended outcome is a preselection of one or more alternatives to improve the power supply of the case study devices according to the mentioned criteria. The selection of alternatives will also include a guideline on which developments to follow and the main reasons to do so. The work is done from a business and practical perspective, meaning that after taking a first decision thanks to this work or the steps followed on it, the R&D departments of the ICT (Information and communications technologies) companies applying the methodology should then study the selected alternatives in a deeper technical analysis. In the conclusions, general next steps to carry out the development will be established. Throughout the work, it is demonstrated that there is not one single combination of technologies that is the best in all aspects, for all weathers and locations, and all applications. On the contrary, the assessment reveals how different devices and conditions affect the decision on which is the most suitable decision. In addition, there is not any alternative that has the best ranking in all aspects, as there are always technical, environmental and economical compromises. As for the specific assessment for the current status of RecySmart device (the first device of the case study), it is recommendable to follow the development towards solar photovoltaic panels in combination with Li-ion or LiPo rechargeable batteries to remove the current primary cells. The selected alternative will involve some developments but has the capability of reducing the cost of the device’s power supply by 48.9% in a 5 years period, while reducing the overall environmental impact. Thanks to the use of a solar panel and secondary cells, it is possible to eliminate 92.1% of the lithium batteries used (moving from primary to secondary cells) and ensuring the autonomy of the device. Finally, for the Single Sensor studied (the second device of the case study), the recommendation is different to the one of RecySmart, as it is more suitable to use secondary cells but without energy harvesting units.