The solar experiment has been concluded and the equipment sold. The information is here just as a record of the activities.
Solar Power System for a Solar Powered Repeater
This project is to build a solar power system that can be used to power a repeater. The system will power a remote receiver and a very low power repeater during the non-winter months.
MAIN COMPONENTS
The main components of the system are the solar modules, two 6 volt batteries wired in series, an MPPT Charge controller, a current shunt, a current tracking device called the WhizBang Jr. (which is connected to the shunt) and several 30 and 15 amp DC Circuit breakers. All of the major components were purchased from Northern Arizona Wind and Sun via their web site at solar-electric.com .
Solar Modules
SolarWorld Sunmodule Plus SW 275 mono (Soon to be 2)
This module is rated to generate 275 watts of power in standard test conditions (which rarely exist in real life).
The performance ratings at 800 W/m^2 are somewhat more realistic conditions than standard test conditions, but even these conditions are likely to only exist for a couple of prime hours during sunny days that are hardly interrupted by any cloud cover. Here are the these performance ratings at 800 W/m^2:
Maximum power (Pmax) = 205 W
Maximum power point voltage (Vmpp) = 28.4
Maximum power point current (Impp) = 7.22 A
SolarWorld Web Site
SolarWorld Sunmodule Plus SW 275 Mono Data Sheet
Charge Controller
Midnite Solar Kid
The charge controller provides several critical functions
It is a DC to DC converter to convert high voltage input (roughly 30v solar modules in this case) to a voltage level suitable to charge the 12v battery system
Provides the optimal combination of voltage and current to charge the battery system without overcharging it
Disconnects the load when the state of charge is low. This minimizes battery wear.
MidNite Solar Web Site
Batteries
Two 6 volt Batteries
Sun Xtender PVX-2240T AGM Sealed
These have a higher temperature range rating than some renewable energy batteries
Storage Temperature -55 C (-67 F) to 50 C (122 F)
Operating Temperature: -40 C (-40 F) to 71 C (160 F)
These batteries are wired in series to form a 12V Battery
Very large operating temperature range
AGM (absorbed glass mat) style batteries - best for low maintenance applications
Sun Xtender Web Site
Miscellaneous
Whiz Bang Jr Midnite Solar current sense module (for enhanced current monitoring and state of charge indication)
50mv/500A Shunt for the Whiz Bang Jr to connect to (this is in line with the negative power connection near the battery)
Din Rail (mount breakers to this)
Terminal strips (Interconnect multiple wires to a common point)
Battery interconnect cable #4 AWG (connect the 2 6v batteries in series)
#10 Stranded AWG Wire (most connections to breakers, controller, and terminal strips)
2 Conductor #10 AWG Stranded outdoor wiring cable with MC4 connectors (connect to the MC4 connectors on the solar module)
50 Amp switch to power the test load which is a 12v utility light that draws about 5 amps
Ring connectors, screws, wood mounting board, plastic tote enclosure
MAIN COMPONENTS
The main components of the system are the solar modules, two 6 volt batteries wired in series, an MPPT Charge controller, a current shunt, a current tracking device called the WhizBang Jr. (which is connected to the shunt) and several 30 and 15 amp DC Circuit breakers. All of the major components were purchased from Northern Arizona Wind and Sun via their web site at solar-electric.com .
Solar Modules
SolarWorld Sunmodule Plus SW 275 mono (Soon to be 2)
This module is rated to generate 275 watts of power in standard test conditions (which rarely exist in real life).
The performance ratings at 800 W/m^2 are somewhat more realistic conditions than standard test conditions, but even these conditions are likely to only exist for a couple of prime hours during sunny days that are hardly interrupted by any cloud cover. Here are the these performance ratings at 800 W/m^2:
Maximum power (Pmax) = 205 W
Maximum power point voltage (Vmpp) = 28.4
Maximum power point current (Impp) = 7.22 A
SolarWorld Web Site
SolarWorld Sunmodule Plus SW 275 Mono Data Sheet
Charge Controller
Midnite Solar Kid
The charge controller provides several critical functions
It is a DC to DC converter to convert high voltage input (roughly 30v solar modules in this case) to a voltage level suitable to charge the 12v battery system
Provides the optimal combination of voltage and current to charge the battery system without overcharging it
Disconnects the load when the state of charge is low. This minimizes battery wear.
MidNite Solar Web Site
Batteries
Two 6 volt Batteries
Sun Xtender PVX-2240T AGM Sealed
These have a higher temperature range rating than some renewable energy batteries
Storage Temperature -55 C (-67 F) to 50 C (122 F)
Operating Temperature: -40 C (-40 F) to 71 C (160 F)
These batteries are wired in series to form a 12V Battery
Very large operating temperature range
AGM (absorbed glass mat) style batteries - best for low maintenance applications
Sun Xtender Web Site
Miscellaneous
Whiz Bang Jr Midnite Solar current sense module (for enhanced current monitoring and state of charge indication)
50mv/500A Shunt for the Whiz Bang Jr to connect to (this is in line with the negative power connection near the battery)
Din Rail (mount breakers to this)
Terminal strips (Interconnect multiple wires to a common point)
Battery interconnect cable #4 AWG (connect the 2 6v batteries in series)
#10 Stranded AWG Wire (most connections to breakers, controller, and terminal strips)
2 Conductor #10 AWG Stranded outdoor wiring cable with MC4 connectors (connect to the MC4 connectors on the solar module)
50 Amp switch to power the test load which is a 12v utility light that draws about 5 amps
Ring connectors, screws, wood mounting board, plastic tote enclosure
OBSERVATIONS
RF Noise
There is some RF Noise that is heard over quite a range of frequencies, this needs more troubleshooting to see if it can be reduced to an acceptable level.
Low Voltage Disconnect
This is built in functionality of the charge controller that is being used, but is not working the way I expected. This needs more research.
High Temperature
Temperature is an issue even without a load running. The sun shining through the plastic container heated it up to 129 degrees one day even though it was shaded by the solar module for a good part of the day.
Generation
These are amps going into the battery at a little over 12v. On most clear days the system generates 5 to 8 amps for 4 to 5 hours (sometimes up to 9 or 10 amps for part of that time in perfect conditions) and then is a bit less for another couple of hours before it tapers off to nothing. The system easily adds 40 amp hours to the battery system in one day during good summer conditions. This has been done many, many times. It has not been tested much beyond the 40 amp hour point because it is best not to drain this particular battery system beyond that. The 40 amp hours is getting close to a 20% depth of discharge on the 224 amp hour battery system. The prototype setup is with the solar module at a sub-optimal angle for most users. Instead of tilting the panel to be perpendicular to the suns rays for the best performance, the module is perfectly vertical. This is to get a realistic look at the performance on a mountain top. On top of a mountain, the solar modules will likely be placed without much tilt, if any at all. They will be vertical to make it harder for the snow to build up on them. This will reduce the generation capacity, but it is better than no generation capacity due to being covered in snow. Even with the solar modules mounted vertically, some high elevation sites with rough Winter weather patterns may still present a challenge. It is likely that snow and ice buildup will still occur during the Winter just from the snow and frost building itself up even on the perfectly vertical surfaces.
The system is designed to charge a 12v battery system to supply power to a 12v load. The voltage supplied from the controller to the battery system will be converted down to roughly 14 volts, and the current can still be around 7 A during times when no clouds are blocking the sun to the solar module when it is vertically mounted.
The conditions listed above only last 4 to 6 hours per day in good Summer conditions with clear skies. During harsh Winter conditions, performance will be very, very significantly reduced. At high altitudes that experience harsh Winters, solar modules may become completely covered in ice for a few months and the charging system will stop generating electricity to charge the battery system. This is one reason the low voltage disconnect is important. If it is set to disconnect the load once the state of charge drops to about 20 or 25 percent, the battery system will remain healthier than depleting them to below 12v. Even if the batteries don't get charged for a couple of months, significant damage to the battery system may be prevented by shutting it off when it hits the 20 or 25 percent state of charge since the self discharge rate of most GOOD batteries is about 5% per month in many conditions.
Freight Shipping
Freight shipping is a wild world for those of us who are not used to it. And, probably wild even for those who are used to it!
Solar modules cost a little under $150 to ship from Arizona to Washington for businesses with shipping accounts. I had mine delivered to a local business.
I ordered 2 solar modules at different times. The first one arrived in great shape. The second one was damaged. Unfortunately the damage was not visible until the packing material was removed. In the future, I will make sure someone is available to remove the packing material from the pallet and inspect the module before accepting the delivery. One option is that the delivery can be held at the terminal of the shipper and I can pick it up there. After many phone calls, my vendor agreed to help me with this even though it was not their fault. It still cost me a lot of extra money. I tried to ship the damaged module back to the vendor, but it was going to cost me well over $400 since I did not have a volume freight shipping account. I paid my solar vendor to process the return shipping for me. They have an account with the freight shipping company that I proposed to use. When I had the solar vendor set up the shipping for me, the cost was under $150.
RF Noise
There is some RF Noise that is heard over quite a range of frequencies, this needs more troubleshooting to see if it can be reduced to an acceptable level.
Low Voltage Disconnect
This is built in functionality of the charge controller that is being used, but is not working the way I expected. This needs more research.
High Temperature
Temperature is an issue even without a load running. The sun shining through the plastic container heated it up to 129 degrees one day even though it was shaded by the solar module for a good part of the day.
Generation
These are amps going into the battery at a little over 12v. On most clear days the system generates 5 to 8 amps for 4 to 5 hours (sometimes up to 9 or 10 amps for part of that time in perfect conditions) and then is a bit less for another couple of hours before it tapers off to nothing. The system easily adds 40 amp hours to the battery system in one day during good summer conditions. This has been done many, many times. It has not been tested much beyond the 40 amp hour point because it is best not to drain this particular battery system beyond that. The 40 amp hours is getting close to a 20% depth of discharge on the 224 amp hour battery system. The prototype setup is with the solar module at a sub-optimal angle for most users. Instead of tilting the panel to be perpendicular to the suns rays for the best performance, the module is perfectly vertical. This is to get a realistic look at the performance on a mountain top. On top of a mountain, the solar modules will likely be placed without much tilt, if any at all. They will be vertical to make it harder for the snow to build up on them. This will reduce the generation capacity, but it is better than no generation capacity due to being covered in snow. Even with the solar modules mounted vertically, some high elevation sites with rough Winter weather patterns may still present a challenge. It is likely that snow and ice buildup will still occur during the Winter just from the snow and frost building itself up even on the perfectly vertical surfaces.
The system is designed to charge a 12v battery system to supply power to a 12v load. The voltage supplied from the controller to the battery system will be converted down to roughly 14 volts, and the current can still be around 7 A during times when no clouds are blocking the sun to the solar module when it is vertically mounted.
The conditions listed above only last 4 to 6 hours per day in good Summer conditions with clear skies. During harsh Winter conditions, performance will be very, very significantly reduced. At high altitudes that experience harsh Winters, solar modules may become completely covered in ice for a few months and the charging system will stop generating electricity to charge the battery system. This is one reason the low voltage disconnect is important. If it is set to disconnect the load once the state of charge drops to about 20 or 25 percent, the battery system will remain healthier than depleting them to below 12v. Even if the batteries don't get charged for a couple of months, significant damage to the battery system may be prevented by shutting it off when it hits the 20 or 25 percent state of charge since the self discharge rate of most GOOD batteries is about 5% per month in many conditions.
Freight Shipping
Freight shipping is a wild world for those of us who are not used to it. And, probably wild even for those who are used to it!
Solar modules cost a little under $150 to ship from Arizona to Washington for businesses with shipping accounts. I had mine delivered to a local business.
I ordered 2 solar modules at different times. The first one arrived in great shape. The second one was damaged. Unfortunately the damage was not visible until the packing material was removed. In the future, I will make sure someone is available to remove the packing material from the pallet and inspect the module before accepting the delivery. One option is that the delivery can be held at the terminal of the shipper and I can pick it up there. After many phone calls, my vendor agreed to help me with this even though it was not their fault. It still cost me a lot of extra money. I tried to ship the damaged module back to the vendor, but it was going to cost me well over $400 since I did not have a volume freight shipping account. I paid my solar vendor to process the return shipping for me. They have an account with the freight shipping company that I proposed to use. When I had the solar vendor set up the shipping for me, the cost was under $150.
OTHER THOUGHTS
Snow and Ice Melting
Needs a lot of research!
How do we prevent and / or remove snow and ice from the solar modules?
Can enough electricity be generated to use heat tape?
Could a snow sensor be used to control power to the heat tape?
Could a water heating solar system be used to circulate hot water around the modules?
How do these options affect the solar modules?
Power Levels
How can the transmitter be switched between high power and low power depending on charging conditions
To Do
Cost effective shelter
This may need to be done without digging and without creating a permanent structure
- Construction site tool chest?
- Concrete structure?
Solar module and antenna mounting structure
This may need to be done without digging and without creating a permanent structure
- Treated timbers?
Grounding
- Particularly as related to mountain tops and mostly rock environments
Ground fault protection
Surge protection
Ventilation
Rodent proofing
Snow and Ice Melting
Needs a lot of research!
How do we prevent and / or remove snow and ice from the solar modules?
Can enough electricity be generated to use heat tape?
Could a snow sensor be used to control power to the heat tape?
Could a water heating solar system be used to circulate hot water around the modules?
How do these options affect the solar modules?
Power Levels
How can the transmitter be switched between high power and low power depending on charging conditions
To Do
Cost effective shelter
This may need to be done without digging and without creating a permanent structure
- Construction site tool chest?
- Concrete structure?
Solar module and antenna mounting structure
This may need to be done without digging and without creating a permanent structure
- Treated timbers?
Grounding
- Particularly as related to mountain tops and mostly rock environments
Ground fault protection
Surge protection
Ventilation
Rodent proofing
