11.1.12b Mr. Scott Schopke’s Machines
Mounted 1 ampere PV
chargers keep batteries
charged & ready to go!
Photos by F. Leslie, 2004; courtesy of Scott Schopke
Forklift (top) and Piling
Grouting Drill Machine (left)
050203
11.0 Solar Energy
Frank R. Leslie,
B. S. E. E., M. S. Space Technology, LS IEEE
2/8/2010, Rev. 2.0.0
fleslie @fit.edu; (321) 674-7377
www.fit.edu/~fleslie
In Other News . . .
 Haggling continues over $1 B for home heating
subsidies in US House
 Senate: $11.5B for mass transit and rail projects
 House: $12.4B for mass transit including $4.6B to buy
transit equipment such as buses
 House: $31B to build and repair federal buildings, etc.
 Pickens reports, “in December we had imported just
under 380 million barrels of oil at a cost of $19.3
billion.“ Then, “In January, according to the Department
of Energy, we imported 408.7 million barrels which cost
the United States about $17 billion, so the transfer of
wealth from America to foreign governments is
continuing. “
090209
11 Solar Energy Overview
 Solar energy is best suited for sunny places to be able to
save enough to ever pay off the equipment investment
 Other possible locations might be where utility power
isn’t available, and payback time doesn’t matter!
 Climate records show the availability of this solar energy
and must not be ignored when designing a system
 Like all climates, the statistical variability requires that a
“long” sample be used, perhaps five years to fifty years
 You estimate the long term from what you have
 Cloudy weather or persistent darkness (Alaska) requires
storage to be able to provide energy at night and
through low light conditions; Alaska solar energy
systems must use wind or diesel energy; 6 months of
storage costs too much!
080205
11.0 About This Presentation
 11.1 History
 11.2 Incoming Solar Energy, or Insolation (note “o”, not
“u”; incoming solar radiation)
 11.3 Solar Resource Availability
 11.4 Solar Variability




100208
11.5 Roberts Hall Solar Modules
11.6 Solar Path Considerations
11.7 Solar Energy Systems Decomposition
11 Conclusion
11.1 History of Solar Energy
 1500 BC Egyptian ruler Amenkotep III supposedly had “sounding
statues” that emitted a tone when air inside was heated by the sun
 800 BC Plutarch noted that vestal virgins used metal cones to light
ritual fires
 212 BC Archimedes purportedly used burning mirrors to set fire to
ships according to Galen in De Temperamentis (see Mythbusters)
 ~1700 AD French scientist, George Buffon, made multiple flat
mirrors to concentrate light to a point. ~1747, he ignited a wood
pile 195 ft away (wood ignites at ~250°C with flux of 4.7kW/m2)
 ~1760 Swiss de Sanesure made a solar oven that reached 320°F
 1837 Herschel used a solar oven to cook food at 240°F in South
Africa
 ~1860 Bessemer made a solar furnace that melted copper and zinc
 ~1860 Augustin Mouchet built “axicons” (simple cone) to focus on
a tube; built steam engines with a 40 ft2 reflector
090210
11.1.1 History of Solar Energy, part 2
 1868 John Ericsson built a solar-powered 2.5 HP
engine that used a parabolic reflector
 1878 William Adams built a 2 kW solar water pump
near Bombay, India
 1880 E. Weston suggested a thermocouple for
generating electricity
 1882 Abel Pifre & Mouchot demonstrated a steam
engine at Tucleries Garden, Paris, driving a printing
press to supply fair visitors with handouts
 1896 C.G.O. Barr patented an idea to place mirrors on
railroad cars, precursor of solar towers
 1912 Prof. C.V. Boys & Frank Shuman built a 50 HP
solar pumping engine at Meadi, Egypt
080130
11.1.2
1903 Meadi, Egypt Solar Engine
http://www.solarenergy.com/info_history.html
http://www.freeenergynews.com/Directory/Solar/Tesla/Experimentor_1916_Solar_Article.pdf photo follows on next page
080205
http://www.freeenergynews.com/Directory/Solar/Tesla/Experimentor_1916_Solar_Article.pdf
11.2 How Much Solar Energy Strikes Earth?
The sun gives off 3.90x1026 Watts (Universe 4th edition, p585)
The earth intercepts energy equal to a disk equal to the earth's
diameter
Earth's radius is 3,393,000 meters (WGS84 value is 6,378,137 m/2)
Earth's solar interception area is (3.14)(3,393,000)^2
This equals 3.62x1013 m2
The amount of power crossing earth's orbit is 1388 watts / m2
Therefore: the earth intercepts 5.02x1016 watts
We see that the earth intercepts 50 quadrillion watts of solar power
each day
We could use some of this energy without depleting the sun!
080205
11.2.1 Solar Energy on Earth
 Energy from our sun (1366 W/m^2) is filtered through
the atmosphere and is received at the surface at ~1000
watts per square meter or less; average is 345 W/m^2
 Air, clouds, and haze reduce the received surface energy
 Capture is from heat (thermal energy) and by
photovoltaic cells yielding direct electrical energy
 Solar “constant” varies
1366.1 W/m^2 Atlas 3
1367 W/m^2 NREL
1376 W/m^2 NOAA
1388
080130
W/m^2 NASA
11.2.2 Solar Spectrum peaks at ~.5 micron
050203
http://www.lowell.edu/users/jch/workshop/gjr/gjr-p1.html
11.2.2 Solar Spectrum changes at surface
080130
http://www.globalwarmingart.com/images/thumb/4/4c/Solar_Spectrum.png/672px-Solar_Spectrum.png
11.2.3 Radiation paths are critical
Over a year, radiation peaks near the summer solstice. Direct
radiation is straight from the sun, while global adds reflected light from
the clouds and other objects.
060201
http://www.jxj.com/magsandj/rew/2000_02/images/solar_radiation_350.jpg
11.2.4 Pyranometers measure light intensity
Sensitivity approximately
70 µV/Wm-²
The upper dome contains the incident surface sensor, while the lower
sensor measures only indirect light intensity from ground
070206
http://www.omniinstruments.co.uk/airweath/cm7b.jpg
11.3.1 How Much Sun is There in the World?
Equator
http://www.oksolar.com/images/world_performance.gif
070206
11.3.2 How Much Sun is There in the US?
030204
11.3.3 How Much Sun is There in the US?
kWh/m2; June average over 30
years
050208
http://www.eren.doe.gov/pv/solarresource.html
11.3.4.1 How Much Sun is There in the US?
030205
http://www.wattsun.com/images/insolation_maps/Flat_Plate_Tilted_South_at_Latitudeminus15_Degrees_JUN.gif
11.3.4.2 Insolation in Melbourne/ Palm Bay Area
 The annual solar energy available in Palm Bay, Florida is estimated at
1715 kWh/square meter-year
Irradiance from this FSEC plot shows the higher energy level available with a
tilted collector. Note the ragged effects of clouds in the sun path
050208
11.4.1 Variations in Surface Energy Affect Potential Capture
 A flat-plate absorber aimed normal to the sun (plate at
90 degrees to incoming sunlight) will receive energy
according to the amount of atmosphere along the path
(overhead air mass Ξ 1)
 The received energy varies around the World due to
local cloud attenuation; in Florida, direct normal
radiation is 4.0 to 4.5 kWh/(m2 - day)
 Throughout the Contiguous United States (CONUS),
daily solar energy varies from <3.0 to 7.0 kWh/(m2 day)
080205
11.4.2 Cloud Variability vs. Location
 Cloudiness attenuates the insolation by reflection and
absorption
 Orographic effects from nearby mountains may cause
local cloud generation or limit the hours of sunlight by
shadows
 Rattenburg, Austria installed reflectors on a blocking
mountain to bounce light into the town
http://findarticles.com/p/articles/mi_qn4158/is_20050326/ai_n13471484
 Lake and sea breeze effects generate clouds that will
block or attenuate the sun’s intensity as received
 Differences of just a few miles can significantly change
the solar collector system effectiveness
 Placement of collectors is important
080205
11.4.3 Module mounting affects energy
 Fixed modules must maximize energy absorption over a year
unless they are to be manually adjusted (perhaps once a
quarter)
 Modules are normally tilted to the south (in the Northern
Hemisphere) by the latitude angle if they are not to be
moved; tilted to north in Southern Hemisphere
 Near the equator, extra tilt is used to drain off rainwater
and accumulated dirt without greatly affecting output
 The PV module can be mounted on an axis parallel to the
Earth’s axis and rotated by a clock drive or servomechanism
 Avoid shadowing of the module cells or a string may not work
 Two-axis tracking uses balanced photocells and drive motors
to tilt the mount to be normal to the sun throughout the day
 Any mounting must also survive storm winds (130 mph in
Melbourne, Florida)
080205
11.4.3.1 Solar Module Annual Tilt
NP
Summer
Solstice
Spring
Winter
Solstice
NP
NP
-23.5°
SP
+23.5° tilt
NP
SP
SP
Fall
SP
 Modules are tilted at latitude angle to be aimed at sun on
equinoxes; at solstices, they are off by the obliquity angle
070206
11.5.1 Roberts Hall Solar Module
 A 300-watt solar-electric module is mounted at 28°
latitude angle and facing south on the south end of the
seventh-floor roof (that’s 4 by 6 feet up there)
A Campbell Scientific datalogger (specialized
computer) collects all data each second
The datalogger records the intensity, average output
voltage, and current at one-minute intervals
The panel provides enough current to charge a 24 V
battery and power the datalogger with 12Vdc
We download the data every 15 minutes, and
process it for http://my.fit.edu/wx_fit/roberts/RH.htm
and for
http://my.fit.edu/wx_fit/realtime_data/fitroofdata.php
100211
11.6.1 Solar Path Calculations
 Equations: see FSEC brochure: McCluney, Ph.D., Ross.
Sun Position in Florida. FSEC-DN-4-83, Florida Solar
Energy Center, Cape Canaveral, FL, 1985
 Website calculations
 http://www.susdesign.com/sunangle/
 http://www-sci.lib.uci.edu/HSG/RefCalculators4.html#SOLAR
 http://www.wattsun.com/resources/calculators/photovoltaic_tilt.htm
100211
You
are
here!
To Sun
Zenith (up)
Zenith
Angle
To Sun
North
Pole
Solar Declination Angle
Horizontal Plane
Latitude
Angle
Equatorial Plane
Zeni
Sun’s zenith angle is measured from local
vertical
Equator
11.6.1 Zenith Angle of Sun
South Pole
070206
Boyle, p 25. is part of reading assignment for ENS4300/ENS5300
11.6.2 Optimum Solar Module Tilt
 Website calculations
PV ARRAY: SOLAR NOON TILT
DATA
Latitude = 28 Degrees North
Month
Sun
Altitude
Array
Tilt
Array
Points to:
JAN
42
48
South
FEB
51
39
South
MAR
62
28
South
APR
74
16
South
MAY
82
8
South
JUN
85
5
South
JUL
82
8
South
AUG
74
16
South
SEP
62
28
South
OCT
50
40
South
NOV
42
48
South
DEC
39
51
South
Array Tilt = 90 degrees - Sun Altitude
http://www.wattsun.com/resources/calculators/photovoltaic_tilt.html
050208
11.7.1 Solar Energy Systems Decomposition
 What are the functions of a solar energy system?
030207
11.7.2 Solar Energy Systems Decomposition
 What are the functions of a solar energy system?
Collect & Distribute
Energy
A systems engineering technique
050207
11.7.3 Solar Energy Systems Decomposition
 What are the functions of a solar energy system?
Collect & Distribute
Energy
Start
Collect Energy
Regulate Energy
Store Energy
Control Energy
Distribute Energy
Use Energy
Each function drives a part of the design, while the interfaces between them will
be defined and agreed upon to ensure follow-on upgrades
030207
11 Conclusion: Solar Energy
 Received solar energy varies widely as evidenced by
climate records and vegetation
 Dry desert areas indicate lots of sun and low moisture!
 This variability affects the economic viability of a system
 Solar energy systems are simple, robust, and easy to
install and maintain
 Solar modules are still expensive, approximately
$3.20/W (2010) for large 150W modules to $16/W for
small, dependent upon size; $5/W to install
A 300W module (4x6 ft) weighs 107 pounds and is
harder to carry and install than smaller modules
One person can readily install 120W to 150W
modules
100208
Olin Engineering Complex 4.7 kW Solar PV Roof Array
Questions?
080116
References: Books
 Cheremisinoff, Paul N. and Thomas C. Regino. Principals & Applications of Solar
Energy. Ann Arbor: Ann Arbor Science Publishers, Inc., 1978.
 Kreith, Frank, and Jan F. Kreider. Principles of Solar Engineering. NY: McGraw-Hill
Book CO., 1978.
 Brower, Michael. Cool Energy. Cambridge MA: The MIT Press, 1992. 0-262-02349-0,
TJ807.9.U6B76, 333.79’4’0973.
 Duffie, John and William A. Beckman. Solar Engineering of Thermal Processes. NY:
John Wiley & Sons, Inc., 920 pp., 1991
 Patel, Mukund R. Wind and Solar Power Systems. Boca Raton: CRC Press, 1999, 351
pp. ISBN 0-8493-1605-7, TK1541.P38 1999, 621.31’2136
 Sørensen, Bent. Renewable Energy, Second Edition. San Diego: Academic Press,
2000, 911 pp. ISBN 0-12-656152-4.
030204
References: Websites, etc.
www.fsec.ucf.edu Our local Cocoa, Florida experts at the Florida Solar Energy Center
(FSEC)
http://www.usc.edu/dept/architecture/mbs/tools/vrsolar/Help/solar_concepts.html
http://www.usc.edu/dept/architecture/mbs/tools/vrsolar/Help/solar_concepts.html#sh_ang
les
http://findarticles.com/p/articles/mi_qn4158/is_20050326/ai_n13471484
______________________________________________________________________
www.dieoff.org. Site devoted to the decline of energy and effects upon population
solstice.crest.org/
dataweb.usbr.gov/html/powerplant_selection.html
080204
Slide stockpile follows!
Older slides follow this one.
Look at these if you have
interest or time. It’s difficult
to decide what to leave out
of the lecture to save time!