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TFSC (Thin Film Solar Cells) |
The Thin Film Solar Cell (TFSC) experiment will test the latest developed TFSC of Dutch Space for their performance in space. The main characteristic of photovoltaic cells is the IV curve related to the temperature. In order to gather this information a measurement system will sample data, which will be addressed by the CDHS for further processing. Since the TFSC experiment is one of the main payloads of DelfiC3, it is necessary to implement redundancy: a set of two TFSCs in series are placed at the tip of each of the four solar panels and the measurement electronics are made redundant by implementing two measurement boards. The cells
The Thin Film Solar Cell is one of the latest developments in the area of photovoltaic cells by the Dutch space company Dutch Space. The cells consist of a CIGS photovoltaic layer which is deposited by evaporation on a titanium base layer of 25 micrometers. The cells will be integrated tile-wise, ensuring a minimal loss of active cell area. The interconnects are covered by the next cell, with an overlap of 5 mm at the longest side (Fig. 5). The mechanical interconnection has a low resistance (~1mΩ); it is placed between the gilded contact pads under low compressive pressure. The aim of this new type of solar cell is to create a light-weight and low-cost product for future space applications. The target is a 50% cost reduction of solar arrays, while improving the power to mass performance with 50% compared to conventional solar cells. Cost is projected to be lower than 350 Euro per Watt at solar array level, and the power is expected to be more than 100 Watt per kilogram. The cell will have no need for a cover glass, but it will have an emissivity‑enhancing and encapsulating dielectric coating. The efficiency will be more than 12 % under AM0 light conditions | |
| IV measurement
For the TIVM, a total of eight measurement points are taken for each IV curve. The concept is based on a short circuit current (Isc) measurement. From this first measurement, the other 7 points are made by taking a percentage of this measurement through switching resistors with fixed values. The Isc cannot be measured directly because of the measurement resistance of 100mΩ: this will have to be calibrated for. The second to the eighth measurement will have a percentage of the measured Isc of respectively 100, 99, 95, 85, 70, 50, 25 and 0 percent. A sample and hold circuit will offer the Isc to the measurements. Each measurement point will be addressed by the PIC of the measurement board. The PIC will measure all points and send them to the CDHS when called upon. TFSC Temperature Measurement
In order to measure the temperature of the TFSCs, a strip of TFSC will be used as a RTD (Resistor temperature detector). RTDs operate on the principle of changes in electrical resistance of metals and are characterized by a linear positive change in resistance with temperature. A strip of TFSC of the same batch as the TFSC payload of 3.0 x 80 mm will be used and delivered by Dutch Space. The resistance of the strip will be amplified through a differential amplifier and measured by the measurement system PIC. Future work
Breadboards are on the way for being tested. After the breadboard the actual prints will have to be made. For anyone interested in producing flight hardware, there are openings here for internships! |
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