PhotoVoltaic Frequently Asked Questions

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This is Version 0.17 of the PV FAQ, written and maintained by H.E. Taylor, last updated July 8, 2002. The original document is archived at http://www.autobahn.mb.ca/~het/energy/pv_faq.html and http://www.autobahn.mb.ca/~het/energy/pv_fqa18.html .
The document is posted irregularly.

A FAQ is a question which gets asked in a newsgroup (in this case alt.solar.photovoltaic ) often enough to be annoying or which is so controversial that it tends to foster argument and thus stifle useful conversation. A FAQ document is one way to maintain a tolerable signal to noise ratio. Note that this document is divided into a FAQ [Frequently Asked Questions] and a FQA [Frequently Questioned Answers].

In general I have opted for a 'storm of questions' format rather than an extended essay, because it is more interesting to me (Socratic dialog) and because it more closely matches the usual newsgroup interaction. Because this is an internet document, it is liable to be read by people of widely varying levels of knowledge, capability and perspective. My aim is to have a document which will be useful for everyone, but this makes defining scope difficult. It might therefore be useful to consider what this document is not. This FAQ does not cover Solar Thermal, generic Renewable Energy or Free Energy. Further, it is not my aim to teach all the background material necessary for a complete understanding -- material, such as basic electronics or quantum mechanics. Where these topics are covered by other FAQs or documents, I have supplied pointers to those other documents, if I know about them. Defining scope can also be difficult, because 'things are deeply intertwingled ', which I think one must take as a blessing, not a curse. It means however that certain topics are mentioned but not extensively explained. eg. the periodic table. Linking helps this somewhat.

Where there are matters of controversy I have indicated them so.

There is a section on acronyms and they are so convenient, that I have felt free to use them liberally. 'Photovoltaic' can get to be a mouthful, for example, so I usually alternate it with 'PV'.

I am not an engineer; I am not a physicist; I am not a lawyer; I am not an electrician; I am not in the photovoltaic industry; and I am not in the building trades. I cannot be responsible for what you do. If you're at all uncertain about what is correct or safe, contact someone qualified -- a licensed electrician, or a local electrical inspector. Where electricity is concerned, safety comes first. For the record, I am just a guy; but as Snoopy said, 'on the internet nobody knows you are a dog.'

It is entirely possible that this document contains errors. If you think that is so, I would appreciate your telling me 1) the error and 2) a reference to further and/or correct information on the matter. Disagreements on controversial topics should be posted to alt.solar.photovoltaic .

Certain particulars of photovoltaics depend greatly upon country. However, the aim here is to make this a globally useful document. I live in Canada and so my perspective may be (unavoidably) somewhat North American. If you have relevant information pertinent to other jurisdictions, please forward to the address in the footer.

Copyright (c) 2002 H.E. Taylor
Copyright on quoted material reverts to the original authors.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Section, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License .

The Questions

  1. What is PV?
    1. What is a solar cell?
    2. What is a PV module?
    3. What is the history of PV?
    4. How has the price of PV changed historically?
    5. Who first used PV in space?
  2. How do photovoltaics work?
    1. What is the photoelectric effect?
    2. What is the photovoltaic effect?
    3. What is the photoconductive effect?
    4. What is the Seebeck effect?
    5. What is the Peltier effect?
    6. What materials show the photovoltaic effect?
    7. What does light do the material to make electricity?
    8. What are solar cells made from anyway?
    9. What is a semiconductor?
    10. What is band gap anyway?
    11. What types of PV cells are there?
    12. What is the electromagnetic spectrum?
    13. What is black body radiation?
    14. Are there PV cells that work in Infrared wavelengths?
    15. What are ThermoPhotoVoltaics?
    16. Are there PV cells that work in Ultraviolet wavelengths?
    17. What is an anti-reflection coating?
    18. What are the different grades of silicon?
  3. What constitutes a complete PV system?
    1. What is an Inverter?
    2. What sorts of Inverters are there?
    3. Are Inverters always noisy?
    4. Are there any plans for a DIY (cheap) Inverter?
    5. What does a Grid Connected system mean?
    6. What is a Solar Tracker?
    7. What sorts of Solar Trackers are there?
    8. How much does a tracker improve output?
    9. What are Concentrators?
    10. What are the issues in using Concentrators?
    11. What is a voltage regulator?
    12. What about lightning protection?
    13. What is a blocking diode?
    14. What is a hybrid system?
  4. How do I figure out what size of system I need?
    1. What is an energy audit anyway?
    2. What is a phantom load?
    3. What kind & how many Batteries do I need?
  5. How much sunlight do I get at my location?
    1. What is the Solar Constant?
    2. When does the sun rise/set at my location?
    3. Can I get software to calculate sun rise/set at my location?
    4. Where can I get statistics about cloudy days?
    5. At what angle should I have my panel mounted?
  6. What about the legal & regulatory controls on PV systems?
    1. What is Net Metering?
    2. Where can I get a grant to put in PV?
    3. What agency controls connection to the grid?
    4. What building approval do I need to add a PV system?
  7. Who makes PV?
    1. Who makes PV cells?
    2. Who makes PV modules?
    3. Who makes PV line equipment?
    4. Who makes PV grade silicon, semiconductor grade silicon?
    5. Can I make PV cells, modules myself?
  8. Who sells and/or installs PV?
  9. What about these specialty items?
    1. What about solar pumps?
    2. What about solar garden lights?
    3. What about solar battery chargers?
    4. What about solar powered street lights?
    5. What about solar powered fans?
    6. What are these solar tiles?
    7. What are Building Integrated PhotoVoltaics?
    8. Does anyone make flexible PV?
  10. What is the highest efficiency PV?
    1. What is the highest efficiency PV possible?
    2. How has the efficiency of PV changed historically?
    3. What is quantum efficiency?
    4. What is the recombination factor?
    5. What is diffusion length?
    6. How do band gap and the solar spectrum affect efficiency?
    7. What is Performance Ratio?
  11. How much do PV cells degrade with time?
    1. How much do PV cells degrade with rising/falling temperature?
    2. How do companies make standard PV measurements anyway?
  12. What is the Payback Time of PV?
    1. What is the Financial Payback Time [FPBT] of PV?
    2. What is the Energy Payback Time [EPBT] of PV?
    3. How much energy does it take to make a PV module?
  13. What is a good school to study PV?
  14. Who is doing PV research?
  15. Can I run my computer on PV power?
  16. Where can I get DC operated appliances?
  17. How can I connect modules with different ratings?
  18. :
  19. :
  20. What are all these electrical terms?
    1. How do you measure power?
    2. What is the difference between Energy and Power?
    3. What are volts, amps, watts, joules, etc?
    4. What's with this SI system anyway?
    5. What's with this old English system anyway?
  21. Where can I get more information about PV?
    1. Are there any magazines dedicated to PV?
    2. Are there any good books about PV?
    3. What newsgroups discuss PV?
    4. Are there any PV related organizations?
    5. Where can I find PV information on the WWWeb?
    6. Are there any PV related mailing lists?
    7. Are there any other PV FAQs?
  22. What does this TLA (Three Letter Acronym) mean?
  23. Credit to those who helped in the preparation of this document.
  24. GNU Free Documentation License

Last modified July 8, 2002

Questions about or problems with the document (eg. broken links) may be sent to -het
Disagreements or questions about PV are best posted to alt.solar.photovoltaic