AndyH
Well-known member
I'm sure your installer has been in the industry for more than 20 years, is in fairly regular contact with the vendor's engineering crews, and has another source of income - that way he has not only the experience and info sources on which to make a valid comparison, but has no financial incentive to replace equipment as often as possible... But I'm probably wrong on all three counts, aren't I? :lol:
Here's a look behind the curtain. In the off-grid world, the charge controller is the interface between the solar panels and the battery bank. One of the most deployed models is the Outback MX60. As you can see here, this device has a two-year limited warranty: http://www.outbackpower.com/pdf/manuals/mx60_pv_mppt.pdf
In the real world, these devices are still in use past 15 years. There have been two subsequent generations of tech since those devices first hit the streets - the latest comes from Midnite Solar and was developed by the principal engineers that created the MX60. The Classic 150 and 200 incorporate improved cooling and component selection and are designed to be in service for more than 20. They have a standard 5 year warranty.
The simple fact is that the industry is evolving at least a quickly as computers did in the 1980s. There's been a strong push for a number of years to streamline manufacturing, improve reliability, and reduce balance of system cost. Some of that can be seen in this 2005 summary from the DOE:
http://www1.eere.energy.gov/solar/pdfs/inverter_II_workshop.pdf And in this on utility-scale equipment: http://energy.sandia.gov/wp/wp-content/gallery/uploads/Inverter_Workshop_FINAL_072811.pdf
This is a reflection of the work being done that led to today's improvements in PV, turbine, and automotive inverter tech - including the 20+ year SMA string inverters, the Enphase units, and the latest charge controllers. It's also why the current Enphase units should last longer than the initial products.
Considering that text books are about five years out of date when they're printed, and that it takes a number of years of field work to publish the first generation of papers on which the next tier summary papers are based, one would be unwise to base a decision today on published docs without becoming aware of the current state of the art And they'd be doubly-unwise to base a decision on hearsay from the internet or an installer that's done nothing more than read the out of date publications. That doesn't make any more sense than deciding not to purchas a generation four hybrid because there were reliability problems with some of the gen 1 cars (and having little awareness of what happened between gen 1 and gen 4).
And finally - back on track! Why would the OP consider expanding the system with a string inverter? The number one reason that drives me is that grid-tied systems MUST disconnect from the grid and shut down when the grid breaks. No grid, no PV, no electricity. One can expand their system with an inverter that sells to the grid while maintaining a battery. While the older segment of their PV system would drop off-line in the event the grid drops, the add-on system would disconnect from the grid, but would continue to generate power and keep the critical circuits in the house energized. This is exactly the reason that people on the East coast are looking for ways to keep their panels working when the grid goes down - one cannot buy fuel for the generator without grid power...
http://www.homepower.com/articles/choosing-inverter
http://www.homepower.com/articles/choosing-battery-based-inverter-0
And with that, I'm going back to assembling my power system - my lightning/surge suppressors have arrived. Cheers.
Here's a look behind the curtain. In the off-grid world, the charge controller is the interface between the solar panels and the battery bank. One of the most deployed models is the Outback MX60. As you can see here, this device has a two-year limited warranty: http://www.outbackpower.com/pdf/manuals/mx60_pv_mppt.pdf
In the real world, these devices are still in use past 15 years. There have been two subsequent generations of tech since those devices first hit the streets - the latest comes from Midnite Solar and was developed by the principal engineers that created the MX60. The Classic 150 and 200 incorporate improved cooling and component selection and are designed to be in service for more than 20. They have a standard 5 year warranty.
The simple fact is that the industry is evolving at least a quickly as computers did in the 1980s. There's been a strong push for a number of years to streamline manufacturing, improve reliability, and reduce balance of system cost. Some of that can be seen in this 2005 summary from the DOE:
http://www1.eere.energy.gov/solar/pdfs/inverter_II_workshop.pdf And in this on utility-scale equipment: http://energy.sandia.gov/wp/wp-content/gallery/uploads/Inverter_Workshop_FINAL_072811.pdf
This is a reflection of the work being done that led to today's improvements in PV, turbine, and automotive inverter tech - including the 20+ year SMA string inverters, the Enphase units, and the latest charge controllers. It's also why the current Enphase units should last longer than the initial products.
Considering that text books are about five years out of date when they're printed, and that it takes a number of years of field work to publish the first generation of papers on which the next tier summary papers are based, one would be unwise to base a decision today on published docs without becoming aware of the current state of the art And they'd be doubly-unwise to base a decision on hearsay from the internet or an installer that's done nothing more than read the out of date publications. That doesn't make any more sense than deciding not to purchas a generation four hybrid because there were reliability problems with some of the gen 1 cars (and having little awareness of what happened between gen 1 and gen 4).
And finally - back on track! Why would the OP consider expanding the system with a string inverter? The number one reason that drives me is that grid-tied systems MUST disconnect from the grid and shut down when the grid breaks. No grid, no PV, no electricity. One can expand their system with an inverter that sells to the grid while maintaining a battery. While the older segment of their PV system would drop off-line in the event the grid drops, the add-on system would disconnect from the grid, but would continue to generate power and keep the critical circuits in the house energized. This is exactly the reason that people on the East coast are looking for ways to keep their panels working when the grid goes down - one cannot buy fuel for the generator without grid power...
http://www.homepower.com/articles/choosing-inverter
http://www.homepower.com/articles/choosing-battery-based-inverter-0
And with that, I'm going back to assembling my power system - my lightning/surge suppressors have arrived. Cheers.