# Tag Info

## Hot answers tagged photovoltaics

15

Your equation is partly correct. You've calculated the energy per photon ($\hbar \nu$), but you've neglected the number of photons. That's why the units don't match (power is energy per unit time, while you've only got energy for each photon). The ideal power (energy per unit time) depends on the area of the solar panel, $A_p$, the number of photons ...

14

I don't think they existed, and it has its reason. First: a solar panel can be characterized mainly by its efficiency spectrum: on which wavelength, which ratio of light energy can it convert to electric power. This needs to have its maximum around the visible light, becausd the Sun gives most of its energy in this wavelength interval. This is because our ...

12

Keep in mind that P-N junctions are created in the first place by diffusing impurities (dopants) into the silicon at elevated temperatures (1000 - 1500 K). The efficiency of the junction is related to how sharply the dopant concentration changes at the junction (its gradient). At lower temperatures, such as those to which a solar array is exposed (say, 270 -...

12

The National Renewable Energy Lab (NREL) estimates something like 0.4%-1% degradation per year for solar panels. I don't know what the chemical action is here (the electrical result being an increase in series resistance of the PV cells), but the long-term degradation of the panels is correlated with UV exposure. Although damaging to the PV material, the UV ...

11

My gut feel is that you would be able to save more energy than you could re-capture by eliminating light wastage and lowering the energy usage of the light source accordingly. Let me use a thought experiment to explain: If you were in a white cube-shaped room with a light in the roof and a large window in one wall with black curtains. At night when there's ...

10

Yes, there are indeed combined PV-T (photovoltaic-thermal) hybrid panels that turn some of the incident light into electricity, and have a circulating fluid and heat exchanger to put some of the heat into a heat store. There's very little take-up of them, because they're just not economic in most circumstances. The theory looks great: PV panels are more ...

10

Yes, increasing the illumination on a solar cell by using lenses or mirrors increases the electric power output. However, there are limiting factors. The efficiency of a solar cell goes down with temperature. The current stays roughly proportional to the photon flux, but the open circuit voltage goes down as the semiconductor junction is heated. Still, ...

9

For a different angle, my experience with solar cells is space-based, rather than terrestrial. The biggest drivers for degradation of space based solar cells are particle radiation and orbital debris impacts. The particle radiation degrades by wearing down the junction, and the orbital debris degrades primarily by increasing the internal series resistance of ...

4

Some materials are somewhat better than others in lower light levels BUT in a typical indoor situation, even an extremely optimised material simply lacks the availability of input energy to convert. eg Mono-crystalline silicon is somewhat better at very low light levels than Poly-crystalline but neither can overcome the fundamental lack of energy. Full ...

4

Putting a single panel in series with two other panels that are in parallel does not accomplish what you think it does. The overall current of such a setup is limited by the single panel to 200 mA, so the three panels will not produce any more power than you'd get by just putting two panels in series. A single solar cell can be thought of as a current ...

4

If you want to charge a 12 V battery, you need a bit more than 12 V. One way to achieve that is to put enough individual cells in series. Another way is to have the panel produce a lower voltage and use a electronic circuit called a boost converter. These convert low voltage at high current to high voltage at low current. If you're clever, you can build ...

3

I had to draw electrical and hydraulic schematics in Microsoft Visio at a past job. I'm glad that is behind me because that software is barely good enough for making flow charts. I would never recommend anyone use it for engineering diagrams. There are expensive professional software programs that solve this problem much better, but if you are on a budget I ...

2

Fill Factor is important for PV (photovoltaic) cell and panel designers but of less direct importance to users. What is usually more important are the practical parameters which result from a given fill factor. Reduced fill-factor cells will also be found to have lower efficiency of conversion, requiring larger panel areas per Watt out. Actual insolation ...

2

Power output of a PV panel is driven by several exogenous factors: the amount and spectrum of light on it; the presence and distribution of any shadows; the voltage applied to the panel; and the temperature of the panels - which is driven partly by the ambient temperature. If you've got the power rating of the panel then you can calculate the fill factor: ...

2

That's a mess, and your labels about what is + and what is - out of each panel seem inconsistant. For the most effective use of the panels, wire them all in series. That will put out around 15 V under full sun. Now use a buck converter to make a regulated 5 V from that. There are many buck converter chips available off the shelf at these low voltages. ...

2

I work for a company that, builds custom truck bodies and upfits vans, though we do not work with GM/Chevy vehicles. Your best source of information will be in the Body Builder Guide that GM provides to upfitters and others that use their vehicles as a base for their own custom vehicles. You'll also want to review GM's Best Practices (found at the same ...

2

It's the temperature coefficient of the panel. It varies by panel, but 0.005 (0.5%) is a fairly normal value for it. Its unit is 1/degree C. It's the rate at which cell efficiency drops off, as the cell temperature rises above 25 degrees C.

2

Have you considered a solar oven? The kind that sits in the sun and is heated by the sun's rays with no electricity or other power source. For cooking it'd be more efficient than a PV system. Obviously it wouldn't work at night so it might not meet your needs.

2

The algorithm The standard control system is depicted below and has the following signals reference signal: $r(t)$ error signal: $e(t) = r(t) - y_m(t)$ input/control signal: $u(t) = K_p e(t) + K_i \int_0^t e(\tau)\mathrm{d}\tau + K_d \frac{\mathrm{d}e(t)}{\mathrm{d}t}$ output signal: $y(t)$ measured signal: $y_m(t)$. Using your notation, we get \$r(t) = ...

1

Without seeing the inverter, if the maker provides 3 separate pv- then I would keep them separate. If they could be joined together, then the maker would have done so.

1

A baseline grid-tie inverter samples the line voltage and produces current that is in phase with it and proportional to the maximum power it can squeeze out of the source (typically photovoltaic). So it's actually the grid itself that the inverters are synchronizing to. This can actually burden the grid with power it doesn't need, or make the job of ...

1

Per the non-imaging optics wiki, C is the "ratio of input and output aperture areas". It is not efficiency like it is in some other equations. So putting a 45 degree half angle into the equation gives C = 2. This means that if the input area is 1m^2 then the output will be 0.5m^2. A solar radiation intensity would increase from say 1000w/m^2 to 2000w/m^2. ...

1

"Building Integrated" can mean that the pv panels are the waterproofing roof layer in place of the roof tiles. That is compared to pv panels mounted on the roof supported some small distance (10cm) above the existing roof tiles. The pv panels work the same in either case as long as the roof integrated panels have sufficient cooling so that the performance ...

1

I found out the answer. The isolated subpanel serves a load-center or distribution panel for backup loads (incase of power outage, etc).

1

you'll need to be expert in (at least) these fields: photocatalysis electrochemistry photovoltaics In addition, you'll have to become intimately familiar with the published efforts others have made in this field over the last 45 years or so.

1

I might go with a set-up use an offset arm to translate a long beam. Said beam has a link at each solar panel to a pole which push/pulls the panel to the desired angle. Kind of like the strings in a window's Venetian blind. The drawback here may be in the amount of mechanical parts required at each panel.

1

You could consider idler sprockets to cause the chain to wrap around the drive sprockets more to increase the number of teeth in contact. the panels may move a bit due to play in the chain - tension and a brake may help... Or you could have a single long drive shaft with worm gears and gears to each panel. The advantage is that the worm/gear will “self-lock”...

1

More to the "even-distribution" question, I'd recommend your idea of water distribution. I'd use spray nozzles - they're designed for relatively even distribution. To that end, I'd recommend IS nozzles (lower budget) or NC nozzles (higher budget), with a distribution manifold. These will provide an easily repeatable test method. Simply dial down to the ...

1

A PV cell's system efficiency will vary exactly linearly with the amount of light blocked by the dust. For the particle sizes and wavelengths involved, refraction and multiple scattering effects are minimal. What this leaves you with is a way to "map" dust collection to the equivalent uniform, neutral density filter as SolarMike implied in his comment. I ...

1

I mounted 20 solar panels to the roof of my Airstream, which has a curved roof. I did this using two L brackets, attached together, then one attached to the panel, through the pre-drilled hole. The other bracket is attached to the top of the trailer using VHB tape. I topped off the attachment to the trailer with eternabond tape. This works great, no drilling,...

Only top voted, non community-wiki answers of a minimum length are eligible