b 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)

11.0 Solar Energy Frank R. Leslie, B. S. E. E., M. S. Space Technology, LS IEEE 2/8/2010, Rev (321)

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. “

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!

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 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/m 2 ) ~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 ft 2 reflector

History of Solar Energy, part 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

Meadi, Egypt Solar Engine photo follows on next page

11.2 How Much Solar Energy Strikes Earth? The sun gives off 3.90x10 26 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 3.62x10 13 m 2 The amount of power crossing earth's orbit is 1388 watts / m 2 Therefore: the earth intercepts 5.02x10 16 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!

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 W/m^2 Atlas W/m^2 NREL 1376 W/m^2 NOAA 1388 W/m^2 NASA

Solar Spectrum peaks at ~.5 micron

Solar Spectrum changes at surface

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

Pyranometers measure light intensity The upper dome contains the incident surface sensor, while the lower sensor measures only indirect light intensity from ground Sensitivity approximately 70 µV/Wm - ²

How Much Sun is There in the World? Equator

How Much Sun is There in the US?

How Much Sun is There in the US? kWh/m 2 ; June average over 30 years

How Much Sun is There in the US?

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

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/(m 2 - day) Throughout the Contiguous United States (CONUS), daily solar energy varies from <3.0 to 7.0 kWh/(m 2 - day)

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 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

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)

Solar Module Annual Tilt Modules are tilted at latitude angle to be aimed at sun on equinoxes; at solstices, they are off by the obliquity angle NP SP NP SP NP SP NP SP +23.5° tilt -23.5° Summer Solstice Winter Solstice Fall Spring

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 and for

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   

Horizontal Plane Zenith Angle of Sun Zeni Zenith (up) North Pole Equator To Sun Equatorial Plane Latitude Angle Solar Declination Angle Zenith Angle Boyle, p 25. is part of reading assignment for ENS4300/ENS5300 To Sun You are here! Sun’s zenith angle is measured from local vertical South Pole

PV ARRAY: SOLAR NOON TILT DATA Latitude = 28 Degrees North Optimum Solar Module Tilt Website calculations MonthSun Altitude Array Tilt Array Points to: JAN4248South FEB5139South MAR6228South APR7416South MAY828South JUN855South JUL828South AUG7416South SEP6228South OCT5040South NOV4248South DEC3951South Array Tilt = 90 degrees - Sun Altitude

Solar Energy Systems Decomposition What are the functions of a solar energy system?

Solar Energy Systems Decomposition What are the functions of a solar energy system? Collect & Distribute Energy A systems engineering technique

Solar Energy Systems Decomposition What are the functions of a solar energy system? Collect & Distribute Energy Store EnergyRegulate EnergyCollect Energy Use EnergyDistribute EnergyControl Energy Store EnergyRegulate Energy Start Each function drives a part of the design, while the interfaces between them will be defined and agreed upon to ensure follow-on upgrades

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

Olin Engineering Complex 4.7 kW Solar PV Roof Array Questions?

References: Books Cheremisinoff, Paul N. and Thomas C. Regino. Principals & Applications of Solar Energy. Ann Arbor: Ann Arbor Science Publishers, Inc., Kreith, Frank, and Jan F. Kreider. Principles of Solar Engineering. NY: McGraw-Hill Book CO., Brower, Michael. Cool Energy. Cambridge MA: The MIT Press, , TJ807.9.U6B76, ’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 , TK1541.P , ’2136 Sørensen, Bent. Renewable Energy, Second Edition. San Diego: Academic Press, 2000, 911 pp. ISBN

References: Websites, etc. Our local Cocoa, Florida experts at the Florida Solar Energy Center (FSEC) gles ______________________________________________________________________ Site devoted to the decline of energy and effects upon population solstice.crest.org/ dataweb.usbr.gov/html/powerplant_selection.html

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!