Overall project technical objectives can be summarised as follows:
Integration of PV cells into the Termoshield:
This makes it possible to reduce the operation temperature of the cell thus increasing the operational life, particularly in relation to the thermal stress of the mechanical structure of the cells; the Thermoshield allows the circulation of appropriate fluids around the PV cells, collecting the infrared radiation, thus improving the efficiency of the cell and collecting heat like a traditional solar-thermal element.
Two kinds of PV cells have been considered:
- Dye photo-sensitised cells - dye cells represent the optimal solution in the medium term; the coupling of the Thermoshield device with a dye cells has the potential to overcome some of the existing limits of the dye cells technology, specifically:
- allow to operate the device at a substantially constant temperature so as to minimise mechanical and electrical problems (leakage or solvent evaporation through the sealing between the two glass sheets; increase of internal resistance with increasing electrolyte viscosity at low temperatures);
- increase the energy utilisation efficiency by performing, in addition to conversion of visible light into electricity, storage and exchange of the heat produced by the near infrared and infrared portion of solar emission.
Research on dye cells will focus specifically on reducing the intrinsic resistance of the glass sheets by using a metal grid inside the cell, to be adequately protected by the attack of the liquid iodine based electrolyte placed between the two coated plates and to peripherally seal the cell in a way that guarantees the sealing while having enough mechanical rigidity and also offering long term stability; wide experience is owned by scientific proposers in the field;
- Silicon cells - this solution can be effective in the short term, thanks to the common availability of Si cells (amorphous and crystalline); the coupling of Si cells with the Thermoshield device is able to provide a stabilisation of cells efficiency and an increase of operational life; very low manufacturing costs can be assured for a-Si cells and therefore easy coverage of wide surfaces.
1. DYSC cells - Metallic grids- high conductivity glass sheets have been produced, thanks to the insertion of silver conductive fingers by screen printing, a current increase by a factor 7.5 respect to a cell without fingers and with the same active area has been achieved.
Insulation of metallic conductors - an ad hoc glass paste has been deposited on metallic conductors by precision screen printing, achieving full, reliable insulation from the aggressive liquid electrolyte.
Sensitisers - laboratory studies have been conducted in order to optimise sensitizers of nanocrystalline wide band-gap semiconductors
- Peripheral cell sealing - polymeric seals have been produced, whose durability has been sufficient to perform laboratory tests and provide final prototypes, but not enough for a stable long-term operation.
Prototyping A 20x20 cm dye sensitive cell has been produced, with glass protected Ag fingers and polymeric peripheral sealing
2. TPVS prototyping:
- Design and general arrangements of a large area TPVS device integrating Thermal Shields and PV silicon cells are available;
- A portable demonstrator of the TPVS concept has been built and tested by CEA/GENEC during 7 months;
- A PV/thermal roof of 100 m2 roof has been completed;
- A two glass-sheets transparent TPVS system has been prototype.
The Thermo PhotoVoltaic System (TPVS) is an innovative co-generation solar device that makes it possible to convert solar energy into thermal energy and electric energy at the same time using a single integrated system.
The TPVS is formed by the coupling of:
1. PV modules capable of collecting the visible spectrum of the light; these can be modules based on any commercial technology;
2. The ThermoShield, an innovative patented solar thermal system that collects the infrared side of the spectrum, cools the PV cell and makes the heat available for the thermal control of the building; The ThermoShield is made of Aluminium panels, behaving like a "living" skin surrounding the building, where a special liquid flows, capturing heat, storing in an insulated tank and making it available for heat control of the living environment;
3. Structural building elements (like panels or tiles); the system has been designed to withstand a structural function, being for instance the covering roof or the walls of a building.
The TPV provides allows to reduce the operation temperature of the PV cell thus increasing the operational life, particularly in relation to the thermal stress of the mechanical structure of the cells. In fact, the ThermoShield makes possible the circulation of appropriate fluids beyond the PV cells, thus improving the efficiency of the cell and collecting heat like a traditional solar-thermal element.
Funding SchemeCRS - Cooperative research contracts
28046 Edif Madrid