Information required about Solar Tracker

[Siddhartha]

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

[wmbjk]

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

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.
**************

Post by Siddhartha
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?

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.

Post by Siddhartha
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.

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

[SJC]

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

Post by wmbjk

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

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.
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.
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.
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.
**************

Post by Siddhartha
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?

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.

Post by Siddhartha
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.

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

[SJC]

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.

"SJC" <***@yahoo.com> wrote in message news:BJy3g.8119$***@trnddc02...
I think trackers are worth it. You might actually get closer to the
power rating of your panels more hours of the day.

Post by wmbjk

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

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.
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.
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.
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.
**************

Post by Siddhartha
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?

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.

Post by Siddhartha
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.

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

[George Ghio]

How many panels are you starting with?

How much does the tracker cost?

Post by Siddhartha
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
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

[Bill Kaszeta / Photovoltaic Resources]

There are reasons that standalone PV systems for powering communication
systems seldom use trackers.

1. The design need is to provide energy thru periods of bad weather. While
trackers enhance output when the sun is shining, they do not improve output
on cloudy days. A reliable design can not be based on monthly averages
unless the energy storage (battery capacity at battery temperature) approaches
a month's worth. This is generally not practical.

2. There is the maintenance factor of moving parts.

3. There is the area requirement, trackers must be spaced far enough apart to
to avoid the shadow of one falling on the other. Generally takes more land
than fixed non-tracking.

Calculation is difficult. There is no free software or service to do the calculations
properly and take into effect the temperature effect on PV output. I once (1990-
1997) sold a program and data to do this worldwide, but the advent of Windows
and a lack of affordable software tools at the time to convert the code to Windows
made it not practical to continue. Most PV manufacturers have some capability
to design systems, contact your most likely PV supplier.

Post by Siddhartha
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
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

Bill Kaszeta
Photovoltaic Resources Int'l
Tempe Arizona USA
***@pvri-removethis.biz

[Duane C. Johnson]

Hi Bill;

Basically, I agree that the high reliability
application should not use a solar tracker.

Post by Bill Kaszeta / Photovoltaic Resources
There are reasons that standalone PV systems for
powering communication systems seldom use trackers.
1. The design need is to provide energy thru periods
of bad weather. While trackers enhance output
when the sun is shining, they do not improve
output on cloudy days.

Sure they do, but not by much.

Post by Bill Kaszeta / Photovoltaic Resources
A reliable design can not be based on monthly
averages unless the energy storage (battery
capacity at battery temperature) approaches a
month's worth. This is generally not practical.

I agree completely. For applications that require
high reliability a solar tracker is generally not a
good idea. OK, tracking can be done but the cost of
such a tracking mount tends to be expensive.

Post by Bill Kaszeta / Photovoltaic Resources
2. There is the maintenance factor of moving parts.

This tends to be quite low as the movements are low
and slow. The sun doesn't move very fast.

Post by Bill Kaszeta / Photovoltaic Resources
3. There is the area requirement, trackers must be
spaced far enough apart to to avoid the shadow of
one falling on the other. Generally takes more
land than fixed non-tracking.

True, but then extra PV panels also take more area.
However, for high reliability these extra panels are
required anyway.

I have consulted on several of these projects.
I discouraged the use of solar trackers.
I generally suggest using 2 to 4 times the PV panel
wattage of normal users. Use high efficiency mono-
crystalline panels as they are basically smaller in
size.

Build the fixed mounts very strong.

Use 2 charge controllers. Each on half of the panel
array. Each controller charges its own battery.
A pair of diodes combine the battery power for the
application.

All this sounds expensive and redundant, and it is.
However, the cost of failure may be more depending
on the application.

Post by Bill Kaszeta / Photovoltaic Resources
Bill Kaszeta
Photovoltaic Resources Int'l
Tempe Arizona USA

Duane
--
Home of the $35 Solar Tracker Receiver
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[Siddhartha]

Hi Bill,

Thank you for your valuable suggestion. I have dropped the idea of
using a tracker in my proposed system. But I am wondering if I use
concentrator modules instead of flat plate modules, what will be the
cost saving. Definitely I can save space also by using concentrator
modules.

Do you know if any company manufactures GaAs concentrator modules
commercially? How stable is this GaAs technolgy? Do you suggest me to
use GaAs concentrator modules for remote telecom load?

Regards.

Siddhartha

[SJC]

Post by Siddhartha
Hi Bill,
Thank you for your valuable suggestion. I have dropped the idea of
using a tracker in my proposed system. But I am wondering if I use
concentrator modules instead of flat plate modules, what will be the
cost saving. Definitely I can save space also by using concentrator
modules.
Do you know if any company manufactures GaAs concentrator modules
commercially? How stable is this GaAs technolgy? Do you suggest me to
use GaAs concentrator modules for remote telecom load?
Regards.
Siddhartha

That seems like the same question. As far as I know, concentrators have
to track the sun, so the reliablility issue comes right back into play.

[wmbjk]

Post by SJC
to track the sun, so the reliablility issue comes right back into play.

This "reliability issue" is way overblown. I have 3 trackers, about 25
tracker-years of experience. During that time there might have been a
total of a tracker-month's downtime waiting for controller repair
after lightning strikes. Even that could have been eliminated by
keeping a spare controller on hand. I've also had C Band satellite
dishes at my last three homes. Again, very little trouble in about 25
dish-year's experience. The mechanical complexity of dish drives is
pretty much the same as solar trackers. In fact, the motor drive on my
current dish is exactly the same as two of my solar trackers. Before
the little satellite dishes became popular, there used to be hundreds
of thousands of C Band dish-movers in service. The owners of those got
far less benefit from watching TV than the average solar home could
get from tracking.

I'm dumbfounded to read that so many folks who own cars, computers,
cell phones, inverters, and MPPT charge controllers believe that
there's something complicated or unreliable about a very small motor
turning a solar array. In my personal experience, the thing that
drives most solar shopping decisions is upfront cost, and that's the
main reason that trackers aren't used more widely. I also note that
when tracker benefits are discussed here, it's rare for the writers to
mention anything other than gross energy-production increases. The
fact that battery charging-versus-discharging hours almost never comes
up tells me that the writers don't have hands-on experience with
tracking.

Wayne

[SJC]

Post by wmbjk

Post by SJC
to track the sun, so the reliablility issue comes right back into play.

This "reliability issue" is way overblown. I have 3 trackers, about 25
tracker-years of experience. During that time there might have been a
total of a tracker-month's downtime waiting for controller repair
after lightning strikes. Even that could have been eliminated by
keeping a spare controller on hand. I've also had C Band satellite
dishes at my last three homes. Again, very little trouble in about 25
dish-year's experience. The mechanical complexity of dish drives is
pretty much the same as solar trackers. In fact, the motor drive on my
current dish is exactly the same as two of my solar trackers. Before
the little satellite dishes became popular, there used to be hundreds
of thousands of C Band dish-movers in service. The owners of those got
far less benefit from watching TV than the average solar home could
get from tracking.
I'm dumbfounded to read that so many folks who own cars, computers,
cell phones, inverters, and MPPT charge controllers believe that
there's something complicated or unreliable about a very small motor
turning a solar array. In my personal experience, the thing that
drives most solar shopping decisions is upfront cost, and that's the
main reason that trackers aren't used more widely. I also note that
when tracker benefits are discussed here, it's rare for the writers to
mention anything other than gross energy-production increases. The
fact that battery charging-versus-discharging hours almost never comes
up tells me that the writers don't have hands-on experience with
tracking.
Wayne

If this were quantified in terms of MTBF and MTTR,
versus power production gains then people could make informed decisions.
This information may be available, but I have never seen it on this group.

[Bill Kaszeta / Photovoltaic Resources]

Post by Siddhartha
Hi Bill,
Thank you for your valuable suggestion. I have dropped the idea of
using a tracker in my proposed system. But I am wondering if I use
concentrator modules instead of flat plate modules, what will be the
cost saving.

I would not expect cost savings for small scale systems. Flat Plate
(non-concentrating) PV modules are in mass production, concentrators
remain a specialty.

Post by Siddhartha
Definitely I can save space also by using concentrator
modules.

I do not believe so. A lot depends on the hours per year of direct
sunshine. A concentrator can only focus the direct beam of
sunshine, the blue sky (diffuse) component is lost, as well as
any ground reflection in winter.

Post by Siddhartha
Do you know if any company manufactures GaAs concentrator modules
commercially?

Try Google, I have no recent expertise.

Post by Siddhartha
How stable is this GaAs technolgy?

Cells in proper sealed modules are stable.

Post by Siddhartha
Do you suggest me to
use GaAs concentrator modules for remote telecom load?

No. Do a search to see if anyone has had success with that.

Post by Siddhartha
Regards.
Siddhartha

Bill Kaszeta
Photovoltaic Resources Int'l
Tempe Arizona USA
***@pvri-removethis.biz