Section 4: Solar Energy Fundamentals Flashcards
What is solar noon?
Solar noon is when the sun is at its highest (zenith) point during the day
When are the soltices?
Summer solstice: June 21
Winter solstice: December 21
When are the equinox?
Spring equinox: March 20, sun angle appears equal to that of equator
Fall equinox: September 22, sun angle appears equal to that of equator
What is solar irradiance?
Irradiance is solar power, aka the amount of sunshine hitting the surface of the planet at any given moment. Measured in watts per square meter.
Irradiance is measured with a pyranometer, which measures solar irradiance in a hemispherical field. It is generally accepted that the earth receives 1,000 watts per square meter of sun at sea level in peak times.
What is irradiation?
Irradiation is solar energy, aka solar irradiance over time. Measured in watts per square meter / unit of time.
What is PSH?
Peak Sun Hours = 1000 watts/square meter for an hour.
500 watts/square meter for 2 hours is also PSH
Where is magnetic north?
On the East Coast of the US, the north needle of a magnetic compass points slightly west (magnetic declination to the west).
On the West Coast of the United States, the north needle of a compass points slightly east (magnetic declination to the east).
The East Coast declines west and the West Coast declines east. You need to correct for these declinations if you are using a magnetic compass.
You only need to correct for magnetic compass. GPS and smart phones already take magnetic declination into account.
Types of solar radiation?
Global: All forms of solar radiation combined. This data is used for normal solar. Measured by pyranometer.
Direct: Direct beam radiation. Measurement is used for concentrating solar. Measured by pyrheliometer.
Diffuse: diffused from clouds or atmosphere, represents 10-20% of radiation on a clear day.
Albedo: reflected radiation, example is clouds, white wall, etc.
What’s the deal with shading?
Shading will reduce either current or voltage. Shading has a disproportionate effect on solar output. Even a small shade can cause 50% energy loss.
2 tools to measure shading?
Solar pathfinder
Solmetric Suneye
Fish eye lense on camera that takes pictures of the skyline at various points and it will spit out a report that will give information regarding total annual solar irradiance data
You can edit the skyline to take out trees and other shading
200 series also an optional GPS output that will allow to talk to various satellite programs
It will print out a report with all the solar data
What’s the deal with Air Mass?
By definition, 1 atmosphere is the thickness of the atmosphere if the sun was straight over your head at seal level.
PV is tested at Standard Test Conditions, which is 1.5 AM spectrum.
The atmosphere varies depending on humidity, pollution, temperature, etc
What are guidelines for PV tilt angle optimization
In the winter, optimum tilt is latitude +15 degree.
In summer, optimum tilt is latitude -15 degrees.
What is elevation angle, zenith angle, incident angle, and azimuth angle?
Elevation angle: the height of the sun from the horizon
Zenith angle: the height of the sun from straight overhead
Incident angle: direct angle striking a panel
Azimuth angle: degrees on a compass. 180 degrees is south
What is solar window?
This is where the sun will be in the sky throughout the year in a particular location
What are some types of solar design hardware?
CAD (Computer Assisted Drafting) programs are the industry standard.
Auto-CAD is for serious industry professionals. Used for much more than simple PV design. Very expensive.
Sketchup can be interfaced with Google software like Google Earth. Takes satellite images and places it in a drawing.
HelioScope - integrates with Google Sketchup. Skelion is another plugin for Sketchup.
PV specific software often has CAD embedded.
