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29 Cards in this Set
- Front
- Back
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What does a resistive load IV curve look like? |
Straight line, the gradient of which is 1/R |
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Where will the resistive load system operate? |
At the intersection between the PV IV curve and the resistor IV curve |
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Where does maximum power point occur on an IV curve? |
knee region |
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What does MPPT stand for? |
Maximum Power Point Tracking |
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How thick are PV cells generally? |
200-500um |
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What are the two types of Solar Cells? |
Poly- and Mono-Crystalline |
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How are the cells fabricated? |
Mine high quality silica or quartz Melt it down Form crystals from molten silica |
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How is single cell fabricated? |
Get seed crystal by dipping a turning rod into the silica and slowly extracting it out. The rod forms a single crystal and then you slice it up |
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How is waste created? |
When you saw the rods, they can be sawed very thinly and the dust can form 50% wastage. |
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How do we ensure the sunlight doesn't get reflected off the silicon? |
Apply non-reflective coating |
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How is mono fabricated? |
Molten silicon is cooled carefully Increased recombinations in grain boundaries cause lower efficiency. Still need to slice it. |
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What is thin film pv? |
Deposited extremely thin layers of semiconductor onto a substrate. |
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What is a disadvantage of thin film PV? |
No longer a crystalline structure and the efficiency is therefore lower |
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What is amorphous silicon? |
. |
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What is cadmium telluride? |
Better than amorphous silicon - superior temperature coefficient Absorbs diffused sunlight Cadmium is toxic however |
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What are standalone systems? |
Used when grid electricity is not readily available |
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What are inverters? |
Convert DC to AC - modern ones have additional functions such as MPPT and battery integration |
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What are batteries for? |
Storing and providing energy when the sun is not available |
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How is battery capacity specified? |
Amp-hours - energy required to supply 1A for 1 hour |
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What is a C rating |
Indication of capacity for various currents drawn e.g. C5 means current drawn for 5 hour discharge time |
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What are the characteristics of an Li ion battery? |
maintains steady voltage for various levels of discharge, then drops quickly when nearly discharged |
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What are the characteristics of a lead acid battery? |
Steady voltage drop as discharge percent increases |
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What are the benefits and costs of Li ion batteries? |
100% discharge higher efficiency high life cycle light weight better performances at high temperatures higher charging higher current discharge |
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What are the disadvantages of lead acid? |
80% discharge lower life cycle |
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Standalone system sizing |
. |
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Load analysis |
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What data do we use to size the PV? |
Insolation data to obtain peak sun hours during design month |
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What is the rule of thumb surrounding generator sizing? |
Should be able to replenish batteries no faster than a C/5 rate |
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How do we calculate the system costs? |
Add costs of PV, batteries, inverters, other components. Estimate generator fuel and maintenance costs using equations in slides. |
