Solar Energy

Solar energy has been an under-achiever

renewable sources

(non-nuclear)8%

wind0.5%

biomass 38%

hydroelectric 55 %

geothermal5%

solar1%

nuclear electric8%

coal22%

petroleum39% natural gas

23%

Source: U.S. Department of Energy

http://symposium2011.serdp-estcp.org/Technical-Sessions/3C

• 2500+ years – Passive – take advantage of ambient conditions

• 250+ years– Active Loop – capture, store, & deliver thermal

energy• 50+ years

– Photovoltaics – convert sunlight into electricity• 25+ years

– Hybrid Systems - concentrating collectors & others

Solar Energy Has A Long History

Passive solar collectors can be as simple as a house designed to take advantage of daylighting.

Passive solar heating recognizes the seasonal position of the sun.

Passive Day Lighting System• tracking dish to collect

sunlight• visible spectrum

transmitted using fiber optics

• packaged like a fluorescent light

• commercialization underway by Oak Ridge Lab

Active loops capture, store, and distribute heat.

Subtle details influence energy recovery for active loops

Photovoltaics capture, store, and distribute electricity.

How does a photovoltaic cell work?

http://science.nasa.gov/headlines/y2002/solarcells.htm

Optimum Mounting Angle

• Solar tracking systems improve overall efficiency up to 30% by keeping panels perpendicular to the sun.

• A fixed panel set at the same angle as the latitude of the site will receive the maximum annual solar radiation.

• If the load demand is high in the winter (northern hemisphere), set the panel tilt at latitude plus 15°.

• If the load demand is higher in the summer (northern hemisphere) set the array tilt angle at latitude minus 15°.

Solana 280 MW CSP plant in Arizona3 square miles of mirrors

Solar Energy Influenced by:

• atmospheric conditions• geographic location• time of day• pollution• season

Solar energy is impressive on sunny days…

…but there’s not much solar energy on cloudy days

Solar energy

changes seasonally

Sizing a Photovoltaic Array

daily energy requirements (kW-hr)/dayArray Size in kW =

Electric Loads

How much solar energy is available?

Average sunshine hours (hr/day)

Quantifying Home Electric Loads• Search using some of the following terms

– Residential– Electric– Calculator

• http://www.nhec.com/residential_energycalculators.php• http://www.tampaelectric.com/TEHMEnergySaversCalc.html

Web-Based PV Array Sizing

• Combine the power of – Mapping programs– PV sizing algorithms– Satellite-based weather data– Databases of rebates, tax credits, and other

incentives• http://www.nrel.gov/eis/imby/

Solar energy challenges

• Better methods of energy storage

• Cheaper manufacturing methods

• Better installation techniques

• Higher efficiency

Is solar energy a viable option?

pro’s• free, renewable, and

non-polluting• provides day-

lighting, heat, & electricity

• low maintenance• independence

con’s• more expensive

than conventional power

• energy source fluctuatesmust evaluate

case-by-case