Transcript The Solar Scholars Program and Fundamentals of PV Design

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 – Noncrystalline 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) ……………………
Blow dryer …………………………….......
Refrigerator/freezer (22 ft3) ……………..
Washing Machine ……………………......
Incandescent light (75W) ………………..
Compact fluorescent (75W equiv.) ……..
Cell phone charger ……………………....
1500W
1000W
540W
1450W
75W
20W
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 CentralEastern 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)