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Solar cell

  1. Nov 27, 2003 #1
    Does solar cell really only absorbs energy from sunlight? What about other sources of radiation such as thermal radiation?

    Wouldn't it be great if there are some devices that can recycles energy produced in major cities and convert it into electrical energy?
  2. jcsd
  3. Nov 28, 2003 #2
    Yes I agree about the thermal energy idea. Any device that gives off heat is wasteful in my eyes. Like a light bulb gives off a great deal of heat, but we are not interested in the heat that is produced only the light, the heat is energy you paid for but are not utilizing so I consider it waste. We waste power everywhere; a lot of machines just let the heat escape into the atmosphere never to be returned. Light, heat, electricity all energy. An electric pump is hot or warm the heat dissipated off of it you paid for on the electric bill! A solar cell uses the photon to create power but if your talking thermoelectric check this out:) http://www.hi-z.com/ I think this technology needs to be enhanced to be put on motors, machines, anywhere you can think of that waste heat is created and then re-channeled back into our electric system, This should decrease the overall efficiency of our power use and cut down on co2 emissions and save us from harmful greenhouse effects in the future. Here I am trying to save the world:)lol anyway it is a cool idea:)
    Last edited: Nov 28, 2003
  4. Sep 5, 2009 #3
    Man i have thought about that idea for years.now i am planning on building solar cells, so communities that don't have access to electricity can get comfort like the big cities from such invention. I am talking cells as small as a "pen light battery" used in walkmans, and also cells as small as a car battery that can be used for running a fridge a tv
  5. Sep 6, 2009 #4


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    Staff: Mentor

    Solar cells make use of optical (visible) light via the photoelectric effect.

    To use thermal energy - one uses the thermo-electric effect - with thermoelectric materials.

    See also - Seebeck effect - "Seebeck tested a wide range of materials, including the naturally found semiconductors ZnSb and PbS."

    Super Soaker Inventor Invents New Thermoelectric Generator
    Lonnie Johnson has moved on from high-powered squirt guns to a chip that converts heat from the sun--or anything else--into electricity



    In the case of transporation systems, one has to consider power/mass (e.g., kW/kg).
  6. Sep 10, 2009 #5
    many devices emit energy like thermal radiation and we can't reuse these energy because of high cost. you can't use the thermal radiation getting out from you light bulb. but in car motor, you can use bit of thermal radiation by using Turbo, it reuse the combustion gases after expansion stork in cylinders and back it again to cylinder to use its high pressure and temperature.

    solar cell, i want to call it as photovoltic cell, just absorb light from the sun and convert it into electricity by using any materials with low band gap. it absorb light from the sun and force electron to move from valence band to conductive band. these electron goes through the external circuit and then through the load losing his energy and come back to its level in low band gap atom, ready for use it again.
    the current from solar cell is DC, you can use it as AC by using inverter
  7. Sep 11, 2009 #6
    I hear a lot about these "solar water heater" systems that bypass any kind of electricity or photovoltaic conversion and just use sunlight to heat water directly. We were looking at a house this weekend that had this set up. It consisted of a bunch of big black tarp things on the roof hooked up to what looked like water pipes. They're supposed to be more efficient, cheaper, and more environmentally friendly than photovoltaic cells.

    As for using waste heat as a power source, I'm sure at some point the second law of thermodynamics is going to place a cap on how much of that you can do...
  8. Sep 28, 2009 #7
    "Heat pumps" are one way they try to do that, use heat that you would otherwise not be able to use.

    Essentually the heat pump is an air conditioning system in reverse, the cold element is outside in the cold, and the "heat exchanger" part that is normally outside (for cooling) is not inside.

    So even it it's very code outside, the cold element should be colder, so it takes in heat from outside, and pumps it inside.

    As for PV's they have a fairly limited spectral response, obviously tailored to the spectrum of filtered sun light.
    Solar cells (PV's) generally come with specs showing their spectral response, fill factor, Isc (Current short circuit) Voc (Volts Open circuit).

    (from memory Fill Factor is a function of series and shunt resistances). I think idea FF is 1
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