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Posted by Siddhartha on April 25, 2006, 2:15 pm
 
Hi,

I am designing an off-grid pv system for a remote telecome load. I am
considering of using a solar tracking system in that to maximise the
solar energy. I would like to know the following:

1. How to size the Solar Array for tracking system? It cannot be like
fixed tilt angle type. How to do the calculation?

2. What are the advantages and disadvantages of using tracking system
over fixed tilt angle type? Do I get any financial benefit, if I go for
a tracking system by using less modules?

3. What are the maintenance issues to be considered while calculating
overall costing of the project? Can tracking system withstand harsh
weather condition like desert, mountain etc.

Regards.

Siddhartha


Posted by wmbjk on April 25, 2006, 7:42 pm
 
wrote:


From http://www.redrok.com/electron.htm#led3x

*************
Many have said that it makes no sense to use a solar tracker with PV
systems as it is cheaper to just add an extra panel for every three.
To this I say bunk.

Using the NREL data:
My link.
http://rredc.nrel.gov/solar/pubs/redbook/redbook_index.html
I find that in Minnesota a single axis tracking PV panel will have a
40% increase in output in December and a 100% increase in June.
In Minnesota:
A PV panel with 15% efficiency
in December tilted to your latitude plus 15 degrees.
http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/
2 to 3 kWh/m^2/day lets say 2.5 solar
2.5 kWh/m^2/day * 15% = .375kWh/m^2/day electric

Or a single axis north-south tracking panel at lat. +15 deg.
3 to 4 kWh/m^2/day lets say 3.5 solar
3.5 kWh/m^2/day * 15% = .525kWh/m^2/day electric
.525 / .375 = 140%
This shows 40% improvement with a tracker in December.

Lets do it in June:
4 to 5 kWh/m^2/day lets say 4.5 solar
4.5 kWh/m^2/day * 15% = .675kWh/m^2/day electric

Or a single axis north-south tracking panel at lat. -15 deg.
8 to 10 kWh/m^2/day lets say 9 solar
9 kWh/m^2/day * 15% = 1.35kWh/m^2/day electric
That's a 100% improvement with a tracker in June.

Of course your location will have different results. For instance I
just did it for San Jose, CA and got an increase of only 14% in both
June and December. Clearly this is not a good place to do tracking.
**************


Don't forget to calculate the benefits of having a longer charging
day, which depending on load schedules might mean increased efficiency
and  less wear and tear on batteries. For example, at our place we
average about 15kWh consumption per day, yet thanks to tracking (and
wind power) we sometimes go for months without exceeding 3kWh per day
battery discharge.


Maintenance consists of inspection and occasional lubrication of
moving parts. Tracking does add components and risk of component
failure though, so on an electrically powered tracker you might allow
for say, replacement of a controller perhaps every five years. More
often if it's a lightning-prone location.

Wayne

Posted by SJC on April 25, 2006, 11:59 pm
 I think trackers are worth it. You might actually get closer to the
power rating of your panels more hours of the day.



Posted by SJC on April 26, 2006, 12:39 am
   But, if this is a remote telecom load, you would want to consider
reliability was well as power output. For reliablility as the major
factor, I would tend not to use a tracker. Wind and moving parts
can cause a problem.

I think trackers are worth it. You might actually get closer to the
power rating of your panels more hours of the day.



Posted by George Ghio on April 26, 2006, 10:40 am
 How many panels are you starting with?

How much does the tracker cost?

Siddhartha wrote:


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