Q: I have just finished Ch:1-6 of you book. It was very clear, informative, and funny. Here are my questions/comments from Ch 1 on the facts & Figures. FYI, I am a visual learner. 1. Do you know of a video/resource that reviews IV curves (Isc, Imp, Voc, Vmp)? 2. Do you know of a video/resource that explains optimal tilt angle . Any practice questions would also be helpful 3. Can you expand on the power factor? Why is it significant? I assumed when current increased, voltage decreased, and vice versa 4. Do you have additional magnetic declination questions? 5. When looking at residential and commercial SWGR, where can I find the busbar rating? A: Thanks for liking the book! Let me answer the questions here: 1. Do you know of a video/resource that reviews IV curves
(Isc, Imp, Voc, Vmp)? I am uploading a part of my SOLAR
PV INSTALLER BOOT CAMP TRAINING + NABCEP ENTRY LEVEL EXAM PREP course, so
you can see some video on IV curves. Everything in that course is fair game for
the NABCEP PV Technical Sales Exam. Just uploaded now and you can watch in the assignments of week 2 of this course. 2. Do you know of a video/resource that explains optimal
tilt angle? Any practice questions would also be helpful There is no exact science on the optimal tilt angle.
Historically, people were using what they called "rules of thumb" and
were taking latitude tilt as optimal for annual production, latitude plus 15
degrees for winter production and latitude minus 15 for summer production. More
recently for annual production, people have been using 30 degrees tilt
throughout much of the latitudes in the US. It is more accurate to use
software, such as www.pvwatts.nrel.gov There are many practice questions in the book and here is
another: What would be the best tilt angle of the following for
winter production at a latitude of 30 degrees? a. 40 degrees b. 30 degrees c. 45 degrees d. 15 degrees The correct answer would be 45 degrees, since the sun will
be lower and we will have to tilt up the PV higher to catch the winter sun. What would be the best tilt for summer in the question
above? 15 degrees is 30
- 15This NASA tool also gives you an optimal tilt angle: 3. Can you expand on the power factor? Why is it
significant? I assumed when current increased, voltage decreased, and vice
versa Power factor is something that can take years to fully
understand and I would not worry too much about it for the NABCEP PV Technical
Sales Exam. What you should know is that when current and voltage are in phase,
then power factor is perfect, which is a PF of 1. When they are out of phase,
then the power factor is less than one. When you have different kinds of loads,
it will cause current and voltage to go out of phase. Motors are especially
well known for causing power factor to decrease. We can fix power factor with
the electronics commonly found in inverters if the inverter manufacturers want
to spend more money making this happen. Many factories and utilities correct
for power factor. Large utility scale PV plants are usually going to be
required to do power factor corrections. In some cases reactive power is
required to be made by inverters. If you see VA or kVA that is like power, but
accounting for the current and voltage being out of phase. Some of the terms
that are used are reactive power and apparent power. Here is a good source for further information on the basics
of power factor: If you can consider Wikipedia a good source (don’t tell
anyone). The thing about current increasing when voltage decreases
would have to do with transformers, dc to dc converters or other forms of
converting power. If you are making power with PV, you can increase current and
voltage by adding extra modules. When you are just converting power from one
form to another, then you are swapping more current for less voltage or more voltage
for less current. 4. Do you have additional magnetic declination questions? If you are in San Francisco where the magnetic declination
is 14 degrees east, what would be the true azimuth if your compass read 180
degrees? a.
180 degrees b.
194 degrees c.
166 degrees d.
346 degrees The right answer is…. Scroll down some more 194 degrees. When you are on the west coast your declination
is positive and you add to magnetic. Other one: If you are in New York where the magnetic declination is 14
degrees west, what would be the true azimuth if your compass read 180 degrees? a.
180 degrees b.
194 degrees c.
166 degrees d.
346 degrees The right answer is…. Scroll down some more 166 degrees. When you are on the
east coast your declination is negative and you subtract from magnetic. 5. When looking at residential and commercial SWGR, where
can I find the busbar rating? Usually you look for a label. Residential is going to be on
the label of the service panel (aka panelboard). Sometimes the label falls off
and you assume that since the busbar cannot be less than the main breaker that
the busbar is the size of the mainbreaker. For example, if I see a main breaker
that is 100A, I know that the busbar is at least 100A, so I go with 100A for
the busbar unless I can prove otherwise. I have a friend who goes door to door looking for other main
service panels where the label did not fall off if he runs into this problem. For commercial switchgear, you have to look for evidence and
labels. You can also use engineering supervision for systems over 100kW and let
the professional engineer make the call. Hope this helps and you can also ask your questions one at a
time when you have them if you like. Thanks, Sean White |

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