Few in the solar industry would argue that solar energy systems perform best when facing due South at or around an angle equal to the sites geographic latitude. The problem we face as solar professionals is that many homes are less than perfect. Luckily, East and West facing locations in full-sun conditions are capable of producing good energy yields. Having design options on two or even three areas of a potential client’s rooftop gives homeowners and designers some flexibility when it comes to creating good looking designs that perform well.
Another problem frequently encountered is shading. When our designers are looking at which solar energy system options are best for your home we often are weighing not only what roof section is best due to its orientation but also what inverter technology is best suited to get the most out of your system.
More and more we are seeing microinverters being pushed as a magic elixir that will get 25% or greater yield out of a given solar panel. We also hear that having a bunch of separate microinverters on your roof is an advantage because it eliminates a “single point of failure” That is certainly one way to look at it but here’s another.
Having 30 or more microinverters on your roof rather than a single string inverter on the side of your home means that you now have 30 potential points of failure on your roof rather than a single wall mounted unit that can be swapped out by a single technician in about 15 minutes.
Think about it for a minute. In order to swap out a single failed roof mounted micro-inverter safely a minimum of two technicians must:
- Drive to your home
- Set up a ladder or in some cases rent or bring a lift and get into position
- Install fall protection or connect to an existing fall protection system
- Remove the solar panel from the racking system
- Replace the unit
- Reinstall the module with new grounding clips.
- Replace mounting hardware to proper torque settings (often impossible due to galling of stainless steel hardware)
- At least in the case of Enphase the manufacturer will reimburse the installer $150 to swap out a failed unit but as a solar contractor I can tell you for certain that it costs more than $150 to dispatch a crew. When multiple failures occur (and yes we have seen this more than once) maybe the reimbursement covers the cost of labor but usually that’s a negative.
Now let’s pull out a crystal ball and look into one possible future for a problematic microinverter system. Let’s say 15-20 years ago you had a microinverter system installed and you have noticed a decrease in the kilowatt-hours you are feeding into the grid each month. You put in a call to the installer, but that guy retired long ago. You find another company to come out and take a look. They log in and see the problem inverter. Great, now it’s just a matter of getting up there and swapping the unit! Now good ole Murphy steps in and the problem module is in the middle of your array, meaning multiple modules will need to be removed to access the unit! This means more modules will be going offline for a while. When the technician gets to the problem module as indicated by the monitoring portal he finds the inverter working just fine. It looks like the original installer made a mistake in mapping the location of the inverter. What now you ask? Modules must be removed from the array until the faulty inverter is located. Do you think you technician is going to do all of this for you for only $150?
Microinverters are often adopted and heralded by new contractors based on lofty promises of performance gains above traditional systems despite numerous studies showing only marginal 1-2% gains for systems where all modules are located in full-sun conditions with no shading.
At South Coast Solar our philosophy is to propose module level optimization technology ONLY when it is needed to create an energy harvest that makes the financial decision to use solar energy a clear choice. We do not believe using this technology as a marketing tool to make our clients believe they are going to see magical returns of 25% or greater over more affordable options.
When our site analysis determines module level optimization is necessary we have chosen SolarEdge as the technology choice because:
- SolarEdge puts fewer electronics under the harsh conditions present on your rooftop
- SolarEdge is 2% MORE efficient than Enphase based on the California Energy Commission (CEC) ratings
- SolarEdge features lower start up voltage rating, which increases yields during the morning/evening “shoulder” periods
- SolarEdge units do not experience “clipping” during sunny days when your solar panels are working the hardest. More on this below.
- And last but not least, Expert studies confirm SolarEdge’s superiority over Enphase and other microinverters.
“SolarEdge consistently passed every test in our labs when we were looking for solar solutions that could withstand Florida’s extreme weather conditions. SolarEdge came out on top every time.”
Ray Johnson – Engineer at the US Solar Institute
http://ussolarinstitute.com/enphase-vs-solaredge-picking-the-right-tools-for-the-job/
“The (SolarEdge) system produced additional yield in all scenarios, even when no shadows were cast”
A study by trade journal and testing lab Photon International determined that Solaredge outperformed Enphase in every shading scenario. Read a summary of the Photon study:
http://www.southcoastsolar.com/docs/se-case-study-photon-summary.pdf
Solaredge optimizers can handle the full power of today’s larger wattage modules with “Clipping” The only Enphase microinverter currently compliant with Louisiana tax credit law is the m215 microinverter. The problem with only being able to output 215 watts of power is that many solar panels today are 260 watts and greater. Clipping is when potential energy yield is lost because the microinverter cannot handle any more energy from the solar panel even though more energy is available for conversion into AC electricity. This is what it looks like when potential energy savings is lost due to undersized microinverters.
The post How we choose the best technology to bring you the benefits of solar. appeared first on South Coast Solar.