The INSOLENSYS technology proposed a game-changing concept for solar energy management. It has introduced, for the first time ever, an integrated approach to the generation and storage within PV cells to compensate the main drawback of current approaches, i.e. the need to manage the intermittency of solar energy through costly and polluting external storage systems.
A solution for integrating capacitors or batteries directly onto solar cells, applicable immediately post-manufacture was successfully achieved. It was demonstrated the interconnection in series and parallel compatible with solar cell integration into PV panels for suitable voltage/current output. However, for large-scale energy storage, the development of high-power capacitors or batteries is still needed.
INSOLENSYS delivers a flexible technology that can be adapted to all the types of solar cells, being a starting towards eliminating the need on external storage.
The successful integration of a capacitor directly onto a crystalline single solar cell has been accomplished. A capacitor 10cmx10cm spray-deposited onto the rear surface of a 12cm x 12cm crystalline commercial solar cell serves as a potential demonstrator of technology (TRL3), enhancing both energy production and storage. The solar cell operates independently from the capacitor, but the capacitor functions both day and night.
During the project several challenges were overcome: 1) degradation of contacts and the interface between contacts and capacitor electrodes; 2) electrolyte degradation over time; 3) degradation of the solar cell depending on the type of connection to the capacitor, electrode types, etc.
The power output of capacitor increases linearly with its size and with the solar cell irradiation intensity. Therefore, the charging of the capacitor with light was successfully achieved and demonstrated. This response is consistent across all repetitions of the light being switched ON and OFF over period of test. A linear increase of current density is observed when transitioning from dark to AM1.5 radiation intensity. To avoid influence of temperature it was maintained below 40C during light exposure experiments. However, for temperatures above 50C, there is significant increase in the capacitor’s current. This is a notable breakthrough, as an increase of cell temperature is beneficial for enhancing the capacitor’s current. Thus, the capacitor operates and has improved characteristics with either high ambient/cell temperature or radiation on the solar cell.
The proposed technology is poised to contribute to the goals of the EU in terms of the Green Deal policy not only because it facilitates the widespread of the renewable energy, but also because it is based on eco-friendly and available raw materials, like Cellulose and Carbon-based materials.
The materials utilised for the capacitor include based cellulose separator/electrolyte, and exfoliated graphite for the electrodes, using a common polymer as a binder. The solvents comprise water, and acetone. The application method is also straightforward, involving a film applicator or spray. These methods can be scaled up and automated for more efficient reproducibility and can be used for both electrolyte and electrodes.
The cost of the capacitor materials considering a prototype of 10cm x 10cm is less than 0.50 €. Furthermore, it was proved their reusability. Even though more detailed tests are required, from the preliminary tests the ionic conductivity of electrolyte and CV measurements of a capacitor constructed with the recycled electrolyte and electrodes and original capacitors are quite similar.
The INSOLENSYS project PI’s team proved the feasibility of the technology and in partnership with the Venture Building company D1 developed the business and marketing strategy.
The scalability of capacitors has been demonstrated. The power output of a capacitor relative to its size showed a linear relationship. There is no degradation of the capacitor’s characteristics over 8 months period, nor has it been negatively influenced by the radiation on the solar cell. The CV characteristics before and after several cycles of charge-discharge show a stable capacitance up to 9900 cycles.
The feasibility of the process, as well as its durability, economic viability, and environmental benefits, were demonstrated. The scalability of the process has also been proven. Owing to the materials used, there are no issues regarding large-scale scalability in terms of material quantity, recyclability, or environmental concerns.
