Archive for March 10th, 2011

10 March

How Do You Measure the Power Produced by Solar Cells ?

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Excellent question from more than one of our readers:  How Do You Measure the Power Produced by Solar Cells ?

To set the stage for our following two film clips, please allow me to explain what a multimeter (or multitester) is:  it is an electronic measuring instrument that combines several measurement functions (measuring voltage, current, and resistance)  in one unit.  Multimeters are available in a wide range of features, precisions,  and prices, anywhere from less than US$10 to more than US$5,000.  To find out how much the power is produced by solar cells, we need to know the voltage and current produced and the fact that power equals to the product of voltage multiplied by current.

  • voltage (unit of measurement is volt, V): electrical driving force, energy per unit charge, electrical potential difference between two points
  • current (unit of measurement is ampere, A): rate of flow of electric charge ( carried by moving electrons in a conductor such as wire or in an electrolyte carried by ions, or in a plasma by both)
  • resistance (unit of measurement is ohm, Ω): measure of the degree to which an object opposes an electric current through it
  • power (unit of measurement is watt, W): power is the rate at which work is performed or energy is converted.  In direct current resistive circuits, electrical power is calculated using Joule’s law. In the case of resistive (Ohmic or linear)loads, Joule’s law is combined with Ohm’s law (I=V/R)
  • such that R represents numerical value of ohm or resistance, I represents numerical value of ampere or current, V represents numerical value of volt or voltage, P represents numerical value of watt or power
  • Joule’s law: P= VI, so solar cell or solar module measured at 2V and 1A would produce power at 2W, solar cell or solar module measured at 3V and 2A would produce power at 6W, solar cell or solar module measured at 2V and 1mA would produce power at 2mW (note: mA=0.001A  or mA means milliA)
  • Joule’s law + Ohm’s law: P=(I2)R=(V2)/R
  • series circuit:

    Series Circuit

    the current through each of the components of the circuit is the same, voltage across the components is the sum of the voltages across each component

  • parallel circuit:

    Parallel Circuit

    the voltage across each of the components is the same and the total current is the sum of the currents through each component

  • 1. Multimeter Tutorial-Solar Schoolhouse

    2. Solar Panels-How to Test-AltE Video Tip

  • Again, thank you for your questions and comments.
  • Posted by sunisthefuture-Susan Sun Nunamaker, sunisthefuture@gmail.com

Homepage: http://sunisthefuture.net http://sunisthefuture.com http://sunisthefuture.org
Any comments and suggestions are welcomed at sunisthefuture@gmail.com

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10 March

What Is Peak Oil?

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If you are in favor of renewable/CLEAN energy, please sign the petition page showing support for FIT/CLEAN Program at http://sunisthefuture.net/?page_id=1065 Thank you.

I am glad to see that our posts last week generated some interesting questions.  One of our readers was inquiring about the terminology, Peak Oil:

Thanks, L., for asking about this very important while often confusing topic in the discussion of renewable and/or solar energy.  Peak Oil is the point in time when the maximum rate of global petroleum extraction is reached, after which the rate of production enters terminal decline.  Peak oil is often confused with the oil depletion;peak oil is the point of maximum production while depletion refers to a period of falling reserves and supply. This concept, derived from Hubbert Curve,

A logistic (continuous probability) distribution  shaped production curve, as originally suggested by M. King Hubbert in 1956.

is based on observed production rates of individual oil wells, and the combined production rate of a field of related oil wells.  The combined production rate from an oil field over time usually grows exponentially until the rate peaks and then declines, until the field is depleted.  M. King Hubbert created and first used the models behind peak oil in 1956 to accurately predict that United States oil production would peak between 1965 and 1970. Did you know that United States used to be one of the largest exporters of oil and now United States is one of the largest importers of oil?

More questions will be answered in the following posts.  Your comments and questions are always welcomed.  Some times it may take a while before all of the questions are addressed, so please be patient with me.

Posted by sunisthefuture-Susan Sun Nunamaker, sunisthefuture@gmail.com
Homepage: http://sunisthefuture.net http://sunisthefuture.com http://sunisthefuture.org
Any comments and suggestions are welcomed at sunisthefuture@gmail.com

Please also get into the habit of checking at these sites below for more on solar energy topics:

www.sunisthefuture.net

www.youtube.com/user/sunisthefuture

www.kiva.org/team/sunisthefuture

www.facebook.com/sunisthefuture

www.pinterest.com/sunisthefuture

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