The Solar Scholars Program and Fundamentals of PV Design

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					  The Solar Scholars Program
and Fundamentals of PV Design



              Prepared by:
              Colin Davies & Eric Fournier


              Sept 2007
Outline

   Renewable vs. non-renewable
    energy
   The science of photovoltaics
   Principle design elements
   System configurations
   The Solar Scholars program at
    Bucknell
What’s wrong with this picture?

   Pollution from burning fossil fuels leads to an
    increase in greenhouse gases, acid rain, and the
    degradation of public health.
   In 2005, the U.S.
    emitted 2,513,609
    metric tons of carbon
    dioxide, 10,340 metric
    tons of sulfur dioxide,
    and 3,961 metric tons
    of nitrogen oxides from
    its power plants.
Making the Change to Renewable
Energy

   Solar
   Geothermal
   Wind
   Hydroelectric
Harnessing the Sun

   Commonly known as solar cells, photovoltaic (PV)
    devices convert light energy into electrical energy
   PV cells are constructed with semiconductor
    materials, usually silicon-based
   The photovoltaic effect is the basic physical process
    by which a PV cell converts sunlight into electricity
     – When light shines on a PV cell, it may be
       reflected, absorbed, or pass right through. But
       only the absorbed light generates electricity.
  The Science of Photovoltaics




http://www1.eere.energy.gov/solar/video/solarcell1.mpg   Source: Olympus Microscopy Resource Center
Crystalline Structure

   Single Crystal Silicon –
    Very efficient but
    expensive manufacturing
    process
    - A single seed crystal is place
    atop a crucible of molten silicon.
    As this seed crystal is slowly
    raised a large single crystal ingot
    is formed. This ingot is then
    sliced into several sheets for
    solar panel manufacturing.
                                          Source: U.S. Dept of Energy
Other options

   Multicrystalline Silicon – Less
    efficient than single
    crystalline silicon but also
    less expensive to produce

   Amorphous Silicon – Non-
    crystalline structure (even
    less efficient); very
    inexpensive depositional
    manufacturing process
Electricity Basics

   The power produced by solar arrays is in the
    form of direct current or DC power.

                                The outlets in our
                                 homes provide
                                 alternating current
                                 (AC).

                                Questions?
Design Elements: Going from DC to
AC power…

   The DC power generated by the array must
    first be converted to AC before it can be used
    in the home or sold back to the utility


       An Inverter
        converts DC power
        to AC power
Wiring

   Efficiency penalty associated with DC power
    over long distances
   AC line losses are minimal
   Resistance depends on conductor: gauge,
    length, material, and temperature
Getting Desired Voltage and Amperage

   Series: Voltages are additive, current is
    equal
   Parallel: Currents are additive, voltage
    remains the same
           Power (Watts) = Current (Amps) X Voltage (Volts)



IV Curve - MPP
IV Curve – Cell Temp & Irradiance
Response
Site Selection - Shading

   Shading effects important to site selection

   Orientation of
    shaded region on
    module is critical to
    output
Site Selection – Panel Direction



   Face south
   Correct for
    magnetic
    declination
Site Selection – Tilt Angle

Max performance is
achieved when panels
are perpendicular to the
sun’s rays



                           Year round tilt = latitude
                           Winter + 15 lat.
                           Summer – 15 lat.
Mounting Options

   Fixed
    –   Roof, ground, pole
    –   Integrated
   Tracking
    –   Pole (active & passive)
Configurations

   Grid-tied
   Grid-tied with battery backup
   Stand-alone
Grid-tied

   When grid goes down, you also lose power
   Excess
    power can
    be sold to
    grid
   Electricity
    can be
    bought
    from grid
    at night or
    on cloudy
    days
Grid-tied with battery backup

   More independence
   Batteries add complexity and cost
Stand-alone

   Remote locations
   Road-side
Energy Consumption

   Air conditioner (1 ton) ……………………           1500W
   Blow dryer …………………………….......              1000W
   Refrigerator/freezer (22 ft3) ……………..      540W
   Washing Machine ……………………......             1450W
   Incandescent light (75W) ………………..          75W
   Compact fluorescent (75W equiv.) ……..      20W
   Cell phone charger ……………………....            24W
                                            Avg U.S. home
                                            = 25 – 30 kWh
                                               per day
Energy Efficiency

   Home energy audit
    –   Insulation, windows
    –   Compact fluorescent lights
    –   Appliances
            Phantom loads
              –   $45 billion kWh annually
              –   $3.5 billion per year
              –   10 power plants
              –   18,000,000 tons of CO2
              –   More pollution than 6 million cars
              –   TVs and VCRs alone cost the US $1 billion per year in lost
                  electricity
Solar Scholars Overview


   Solar Scholars is an innovative, solar-energy education
    program for university students throughout Pennsylvania,
    created by The Sustainable Energy Fund of Central-
    Eastern Pennsylvania (The SEF-CEPA).

   Its goal is cultivating the “solar and renewable energy
    leaders, policy-makers and entrepreneurs of tomorrow.”
Solar Scholars Workshop
BUEC Installation
   Twelve 200 W GE panels (2.4kW)
   Ground mounted
   Fronius Inverter with Datalogger
   Grid-tied
Mod Installation

   Two pole mounted arrays: Eight 200 W GE panels
    per pole (3.2kW total)
   Fixed
   Passive tracker
   Two Fronius Inverters
   Grid-tied
Mod Installation (cont)




            All in a good days work…
Ready for a field tour?

   Questions?
    If you are interested in anything you have seen today
    and would like to get involved, please contact any
    member of the Solar Scholars team:
Colin Davies, Eric Fournier, or Jess Scott
     (cjdavies, efournie, jpscott)