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Solar Energy

Solar Energy Systems

Matt AldemanSenior Energy Analyst

Center for Renewable EnergyIllinois State University

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SOLAR ENERGY OVERVIEW

1) Types of Solar Power Plants2) Describing the Solar Resources3) Photovoltaic (PV) System Components4) Photovoltaic (PV) System Mounting Types

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Solar Energy• Types of “Solar Energy”:

– Solar Thermal• Residential Systems (hot water)• Utility-scale trough collectors• Power Towers• Solar Chimneys

– Solar Photovoltaic• Monocrystalline• Polycrystalline• Amorphous Silicon (thin-film)• Multi-Junction• Concentrated PV

Solar Energy

• Types of “Solar Energy”:– Solar Thermal

• Residential Systems (hot water)• Utility-scale trough collectors• Power Towers• Solar Chimneys


Photovoltaic Effect

Photovoltaic Panel Components

• Cell• Module • Array

Source: US DOE

Solar Energy

• Types of “Solar Energy”:– Solar Thermal

• Residential Systems (hot water)• Utility-scale trough collectors• Power Towers• Solar Chimneys


Path of the Sun• Actually, path of the Earth• Two motions of interest:1) yearly rotation of Earth about the Sun. The Earth rotates in a circle (actually a slight ellipse) around the Sun. The perimeter of this ellipse defines the ecliptic plane

2) daily rotation about Earth’s axis. Earth’s axis is 23.5 degrees tilted from the ecliptic plane. The equator of the Earth defines the equatorial plane

Ecliptic vs Equatorial planes

Ecliptic plane Equatorial plane

Angle between ecliptic plane and equatorial plane is always 23.5°

Solstices, Equinox• Summer Solstice: Solar declination is at its maximum (+23.5°).

Days are longer than nights in Northern Hemisphere. All points south of Antarctic Circle are in total darkness. Sun is at zenith (straight up) at noon for locations on Tropic of Cancer.

• Equinox (Spring, Fall): Every location on Earth has equal length day and nights. Sun is at zenith at noon on the equator. Sun rises due east and sets due west across the globe.

• Winter Solstice: Minimum solar declination (‐23.5°). Days are shorter than nights in the Northern Hemisphere. All points north of the Arctic Circle are in total darkness. Sun is at zenith at noon for locations on Tropic of Capricorn.

Where is the sun?• Azimuth Angle: The horizontal angle between a

reference direction (typically south) and the direction that a solar array faces

• Solar altitude angle: The vertical angle between the horizon and the sun (how high is the sun in the sky?)

• Tilt angle (for solar arrays): vertical angle between the horizontal and the plane of the solar array

Sun Paths

U.S. Solar Resources

Worldwide Solar Resources

Absorbed by O3, CO2, H2O

Scattered by particles

Atmospheric Effects

10-20% diffuseclear day

Atmospheric Effects

100% diffusecloudy day

Atmospheric Effects

Flat plate collectors use diffuse and direct radiation

Concentrating collectors use only direct radiation

Irradiance is a measure of solar power

Sunrise SunsetNoon

1000 W/m2 = peak sun

1000

500

Insolation is the solar energy in 1 day

Sunrise SunsetNoon

4.5 kWh/m2 /day

1000

500 4.5 peak sun hours

North South

East

West

Sun path at equinoxesSun path at

summer solsticeSun path at winter

solstice

Solar Window

Photovoltaic panels are rated at 1 peak sun (1000W/m2)

200 W x 4.5 sun hours/day

900 Wh or .9 kWh of energy/day

200W

How much electric energy is produced by a PV Module?

PV Market Segments

• Residential Market: <30kW– Homeowners

• Commercial Scale: 30 – 300 kW– Factories and Retail outlets

• Utility Scale: >300 kW– Subject to same regulations as

power plant contruction/operation

Solar Energy Annual Growth

System Types

1) Grid Tie2) Grid Tie with Battery Backup3) Off-Grid

Home Power, December 2011, p.60

Grid Tie SystemsMost systems installed in the US are grid tie.

Grid tie inverters use high voltage PV series strings for simplified wiring.

Grid tie systems cost $6-8 per watt installed.

The system does not have to support the entire load, keeping costs low.

The system cannot function when the grid is disrupted.

http://256.com/solar/

Grid tie inverter

To grid

http://256.com/solar/

Grid tie inverter

To grid

Net Metering

Stand Alone (Off Grid) SystemsBattery based inverters use low voltage PV wiring. This is more complex and expensive.

Off grid systems cost $10-12 per watt installed.

The system must support the entire load, usage must be carefully monitored

Batteries require maintenance and must be replaced.

Home Power, April/May 2010. p. 82

Off grid systems require extra equipment.• Battery bank• Charge controller• Generator backup• Transfer switch

Roof Mount SystemsMost systems are installed from the top

Clips are used to mount panels to railsRails are bolted to rafters

Roof Mount SystemsModules are close to roof for neat appearance

Flashing guards against water damage

Panels get hot and performance is reduced

Many of these homes have no south facing

roof slopes.

Crystalline PV modules mounted on steel roof

http://www.nrel.gov/data/pix/Jpegs/17843.jpg

PV modules mounted on standing seam steel roof

Special clips are available to mount directly to seams

http://www.coolflatroof.com/ib-solar-roof.php#intro

PV integrated with cool roof membraneGood application for California because many roofs cannot support much extra weight

http://www.nrel.gov/data/pix/Jpegs/13455.jpg

Rack mounted and ballasted on flat roofs

Inexpensive and easy to install, no roof penetrations

Adds extra weight to roof

2.4 kW PV array, Turner Hall, Illinois State University

Ground Mounts for Large Scale PV

Single Axis Trackers on N-S Axis

Single Axis Azimuth Trackers

Dual Axis Trackers

Up to 30% more energy compared to fixed mounted PV

Questions?

Matt AldemanSenior Energy Analyst

Center for Renewable EnergyIllinois State University

[email protected](309) 438-1440

solar energy - illinois state university energy.pdfsolar energy • types of “solar energy”: –...

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