FOXES Power Cube
FOXES Power Cube is going to be a novel stand-alone zero emission power generating and storage system, which combines a photovoltaic energy harvester with a multilayer capacitor. The system is designed to provide energy autonomous operation for a multiplicity of applications even in low illumination conditions.
FOXES Power Cube is constituted by the combination of three elements:
- A lead-free perovskite solar cell (PSC) for energy harvesting.
- A multilayer thin film capacitor (TFC) with high energy density for energy storage.
- An energy management circuit (EMC).
This structure allows to store the energy surplus produces by the solar cell in the capacitor, to be used during periods of time when light is not available. The Energy Management Circuits ensures a positive energy balance for powering the load, which, in proof-of-concept demonstration target by the project, is represented by a wireless air-sensor node.
The three components of FOXES Power Cube will be fully 3D monolithically integrated using low-cost solutions and sustainable processes, minimising the use of harmful chemicals, toxic elements or critical raw materials. The TFC will be deposited on a standard substrate (e.g. glass), the control electronics will be deposited on the TFC and the PSC on top of the electronics. Graphene will be used as electrodes and as a protection layer between the metal oxide electronics and the PSC, in order to improve PSC stability and to protect the underlying layer system against chemical interaction with the precursors used for the preparation of the PSC.
Within the project, FOXES Power Cube will be realized with a dimension of 2 x 2 cm2. In this specific configuration, the system can harvest an average energy of ~260 mJ/day even in very low light conditions. Assuming an input voltage of 4 V (as provided by the solar cell), the capacitor will be able to store 0.3 mJ per layer. The energy storage of the capacitor can be up-scaled by charge-pumping the input voltage to ~34 V (for which 40 mJ can be stored at full capacitor charge), and/or by using a complex multi-layer approach.
The sensor node
The FOXES project aims at demonstrating that the Power Cube can supply, in a sustainable manner, a fully functional IoT application including all the expected features: sensing, actuation, control, processing and wireless communications.
The application chosen is one of the most challenging in terms of power budget: environmental gas sensing. These kinds of sensors are operated under heat or light excitation, and therefore involve power hungry actuators (heaters, light sources) that have jeopardized to date their use in autonomous IoT networks .
In FOXES, we will develop our own IoT Bundle that will include a gas sensor element and the necessary control and communication electronics. Altogether the sensor node will have less than 50 µW power consumption per readout.
The combined Power Cube – IoT Bundle will be tested in the lab against gas mixtures during variable irradiation conditions for the photovoltaic cell. Several sensor readout schemes will be tested to forecast the Power Cube performance against demanding applications.