1. Photovoltaic Solar Energy
Building Industry Technology Academy
Western High School

2. What is energy? Energy is often defined as the ability to do work.
We commonly think of gas, electricity, or other fuels
Several different forms of energy, including kinetic, potential, thermal, gravitational, sound energy, light energy, elastic, electromagnetic, chemical, nuclear, and mass have been defined to explain all known natural phenomena.
The first law of “Thermodynamics” is that energy cannot be created; only transferred between systems
Is electricity created?

3. Solar Energy The Sun gives of two forms of energy for free
Sunlight – solar radiation
This gives us both light and heat
Without it no life could exist on earth
Gravitational Pull
Along with the moon’s gravitational pull is responsible for the ocean tides

4. Sun Power

5. Free Energy Our Sun releases huge amounts of energy
Our atmosphere, and clouds reflect or absorb about half of what is directed at us
What hits the surface of the earth in one hour, more than equals the total energy requirements for the earth for an entire year!
The sun is responsible for 99.9% of all renewable energy sources on earth
Wind, wave power, hydroelectricity, biomass & solar
Even petroleum products originated from the sun

6. How do we harness all that power?

7. The Solar Industry Thermal Photovoltaic
Using the Sun’s heat to generate electricity
Solar cooking
Solar hot water
Photovoltaic
Using solar radiation to generate electricity
Solar calculators, light meters, & photovoltaic cells

8. Photovoltaic From the Greek word phos = light & volt = electricity
Solar cells are made from silicon crystals sliced thin and layered
Silicon is a semiconductor, electricity can pass but with high resistance
Solar radiation pushes electrons through

9. Solar Cells About the size of your hand
Electrical contacts both front and back
Positive one side negative the other
Covered with antireflective glass

10. Photovoltaic system

11. Photovoltaic system

12. Solar panels Most efficient solar panels available today 30 – 40%
Average solar radiation is 1000 watts per meter2
Output of that panel would be 300 – 400 watts
Very costly roughly $800 per watt
Usually used in space
Common efficiency rating for panels 16%
Much more affordable cost of $4 - $5 per watt
Installed cost of system $7 - $9 per watt is common

13. Cost benefit analysis Systems are sold on a per watt of output basis
Far easier to do a cost benefit analysis
First question asked by a salesperson:
How much did you pay for electricity last year?
Easy to obtain information on current electric bill
System is sized to cover 70% to 100% of expected use
More is not better!
Utility companies do not pay for extra – credits only

14. Output of panels Factors change the output of panels
Intensity of light source
Angle of light source
Panel temperature

15. Intensity of Light Relative strength of solar radiation
Strongest is at the equator
Black dots represent the
amount of sunlight needed
to replace all of the world energy use
We receive 6000 times the amount of energy used

16. Angle of light Best output is when light strikes at 90o to surface
Orientation is usually south
Suggested angle for best output
is the same as the latitude of location
Summer and winter changes in sun
angle
Tracking systems are optimal

17. Temperature High temperature will reduce the output of solar cells
Cool temperatures are best, hot to the touch, is bad
Elevated installations are suggested, with air circulation under panels
Evens the playing field,
northern climes can still have
effective PV systems because
of cooler temperatures

18. Inverter Panels generate DC current (like a battery)
Inverter changes DC current to AC current and changes the voltage to 120/240 for home use
Systems are tied into home electric panel
During sunlight, if output is greater then home use, electricity is put into the power grid
Electric meter will spin backwards
At night, electricity will flow into house normally
This system is called a “Grid tie system”

19. Design Many homes are designed for “net zero” energy use
Grid tie system, still use energy at night
Annual energy use is a net zero as panel output equals total home use.
Energy conservation is key to “net zero” design
Keyword – Sustainability
To live in a manner that is sustainable by the environment

20. Questions What are the two types of energy we receive from the sun?
What are two general types of commercial solar energy?
What is the most common material used to make solar cells?
For a home application, should the homeowner require the most efficient solar panels available? Why?
Can you think of a way to analyze the cost of a system to see if it is cost effective to install in a building?

21. Questions What factors should be considered in the cost analysis?
Would Southern California be a suitable location for a solar system? Why?
Use Google Earth or other mapping software off the internet to find out the Longitude and Latitude of this classroom.
When considering roof pitch, orientation and shading, which rooms on campus would make ideal locations for a photovoltaic solar system?
What information would you want to have from a client in order to prepare a bid to install a solar system?