Transcript Solar Home Systems Part 5

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2-11. Preventive Maintenance
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Marshall Islands March 31-April 11, 2008
Marshall Islands March 31-April 11, 2008
e8 / PPA Solar PV Design Implementation O&M
Preventive maintenance
• Maintenance is of two types:
– Preventive maintenance is carried out on operating systems
and is intended to reduce the risk of failure
– Response maintenance is carried out where a problem has
occurred and maintenance has to be carried out to fix the
problem. This may also be called repair maintenance
• Preventive maintenance is vital for solar systems because failure
is usually the result of many small problems that could mostly be
prevented. Proper preventive maintenance only takes 15-20
minutes to complete but will do much to ensure long, reliable life of
the components.
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Activities (1)
• Clean, clean, clean. Many problems occur because of
accumulation of dirt and corrosion
– Clean the battery and check connections. Add
protective grease to connections if needed.
– Clean out battery cap vent holes so charging gas
can be released from the cells
– Clean and check connections if there are visible
problems
– Clean the lights
– Clean panels if needed
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Marshall Islands March 31-April 11, 2008
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Activities (2)
• Check battery for voltage and take hydrometer readings
to see if cells are equal and if battery charge seems
normal under the conditions existing at the time of the
visit.
• Fill the battery to the proper level with pure water. Do
not overfill.
• Periodically check the voltage drop at switches to see if
any have a voltage drop over 0.05V when switched on.
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Activities (3)
• Interview the user to see what is felt to be the
status of the system. If there are problems try
to determine why.
• If the condition of the battery indicates
possible controller malfunction, check the
controller.
• Check to see if additional appliances have
been connected to the system
• Examine the panel to see if the mounting
remains solid and the wires properly attached
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Marshall Islands March 31-April 11, 2008
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Activities (4)
• Check the wiring to see if it has become
detached from the building.
• If there are underground wires, check to be
sure the pipes remained properly sealed with
silicone rubber
• If problems are uncovered, correct them on the
spot if possible.
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Record keeping
• For every installation there should be a list of
components and their serial numbers. A wiring
diagram should be made. These papers should
be copied for storage at the main office and
copies kept at the installation
• Any time components are repaired or changed,
a note of the action taken should be made so it
is clear what components are causing
problems and to bring site records up to date
with corrections also made to the office copies.
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Marshall Islands March 31-April 11, 2008
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Monitoring
• Because battery problems may take months to
show up clearly, there needs to be a continuing
record of battery measurements (voltage, time
and date of visit, hydrometer readings for each
cell, and the amount of water needed by the
battery) so problems that are increasing in
severity can be easily identified by comparing
prior readings.
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2-12. Troubleshooting
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Marshall Islands March 31-April 11, 2008
Marshall Islands March 31-April 11, 2008
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Know how the system is supposed to
work
• When the system is new and working well,
disconnect the panel from the controller and
check amperes on a sunny day so you can
later make the same measurement and know if
the panel is working properly or not.
• When the system is new measure the voltage
drop at all switches so you can tell if they are
getting worse over time
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Types of failures for SHS
• Total failure, no power day or night
• Partial failure, power for some appliances
during the day but not at night
• Reduced capacity, the system works ok but for
an unacceptably short time.
• Abnormal characteristics (fast water loss, some
appliances don’t work while others do, etc.)
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Total failure – Battery discharged
below LVD cutoff
• When there is no power available the possible
problems are:
– Panel wires disconnected or broken.
 Disconnect the panel at the controller and
measure Amperes from the panel to see if current
flow is normal. Voltage measurements are NOT
adequate for checking the panel.
– Controller not charging the battery
 Voltage at controller panel connections normal for
charging but voltage at battery connections is
below the LVD voltage
– Battery connection loose
– Battery failure
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Marshall Islands March 31-April 11, 2008
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Total failure. Battery has low charge but is
above LVD Cutoff voltage
• Low voltage disconnect has activated due to low
battery and the battery charge has not recovered
enough to reset.
• Battery connection loose
• Fuse blown
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Marshall Islands March 31-April 11, 2008
Total Failure. Battery has reasonable
charge
• Fuse at battery blown.
• Wiring between battery and controller has a problem
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• Battery connection loose
• LVD control cut off appliances and did not reset.
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Marshall Islands March 31-April 11, 2008
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Partial Failure
• No power at night, some power during the day
– Battery failure (open circuit) so during the day the
panel operates some appliances directly but the
battery does not charge
– Battery disconnected or loose connection.
– Battery fuse blown
• Some appliances work some do not.
– Switch failure
– Loose connection
– Appliance failure
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Reduced capacity
•
Increased shading
•
Charge Controller cuts off the charge at too low a voltage (check
battery voltage when fully charged)
•
LVD cuts off the load at too high a voltage (check battery voltage
when power disconnects)
•
Loose connection at panel, controller or battery
•
Unusually long period of cloudy weather
•
User has increased appliance use and is running the system down
faster
•
Battery is damaged and has lost capacity (consider battery age
and knowledge of its history, do a simple capacity test).
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Marshall Islands March 31-April 11, 2008
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Causes of inadequate system
capacity
•
Panels: Shading, incorrect orientation, loose connections,
damaged panel
•
Controller: Charge set point too low, LVD set point too high
•
Wiring: Bad connection in Panel to Battery circuit, high voltage
drop in switches, wires too small
•
User: Excessive use.
•
Battery: Loss of capacity due to sulfation or repeated deep
discharge, loose connection, low electrolyte, old age
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Marshall Islands March 31-April 11, 2008
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Battery Replacement
• Before replacing a battery be SURE all the rest of the system is
operating properly. Installing a new battery in a poorly working
system dooms the new battery to early failure
• If the battery is shown to be bad, replace it and recondition all
the rest of the system including:
– Full checks of the controller to be sure it is working correctly
– Cleaning and restoring all connections to new condition
– Checking all wiring for proper attachment to the building
and proper location of wire fasteners
– Check all wiring for proper sizing
– Check panel mount for orientation, corrosion and any need
for repair to maintain needed storm resistance
– Check of all appliances for proper Ampere draw and correct
operation.
– Check for possible shading increases considering the
different locations of the sun over the year.
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Marshall Islands March 31-April 11, 2008
What’s Wrong in this Picture? What’s right?
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