[RE-wrenches] P1 micro performance

Carl Emerson Carl at solarking.net.nz
Tue Mar 26 17:29:00 PDT 2013


Friends,

 

Keeping the record straight.

 

I need to say that I have had correspondence 'off list' from a development
engineer from a prominent manufacturer who assures me that his product is
designed to run 'flat out' 24/7. 

 

The unit in fact is just coasting at it's maximum power rating. 

 

This allows for a projected life matching that of the PV.

 

In this case power clipping will not shorten the products life.

 

I am unable to confirm if all manufacturers are taking this approach, buyer
beware.

 

Regards
Carl Emerson

 

Nick,

 

Is Enphase going to be introducing to market any time in the near-term a new
micro with a higher output?  It seems very likely that the trend toward
higher output mods will continue.  The M215 will surely be left behind to a
greater degree as this trend continues if there are higher and reliable and
comparably priced, on a dollar/watt basis, micros available.

 

Thanks,

marco

 

Hi Carl, Marco, and Wrenches,

As a longtime installer, I understand your point of view.  Historically, I
designed my string and microinverter systems with the same consideration for
maintaining conservative DC to AC ratios.  That being said, the costs of
modules have decreased significantly and the dynamics have changed.  Solar
companies should be focused on selling systems that offers a great rate of
return.  Maximizing the customer's investment is most important.  Isn't that
what your customer wants?

What Enphase is encouraging is the development of cost effective PV systems
that will generate a healthy return.  Considering that the modules are only
20% of the total system costs today, it is smart to give up 0.2% or more of
the module production to lower the overall system costs by 5-10%.  The NEC
requires that the AC panel boards, conductors, and circuit breakers are
sized to the inverter continuous output current rating.  We should be
maximizing this infrastructure.

 

The data available indicates that when a system is installed with a 1.2 to
1.25 DC to AC ratio, it will rarely operate at peak output.  Installing a PV
system with a 1.25 DC to AC ratio is not driving the equipment to the
maximum.  In the case of the Enphase M215s; they are designed to operate
continuously at peak output, so reaching that level a few hours in the first
years is not problematic.  To be clear, this limiting will occur the most
during the spring months, because you have a combination of both cool
weather and high irradiance levels.

As Dan mentioned, this applies to string inverters as well as
microinverters.  One of the most common system designs of the early US
grid-tied market was installing 18- 165 watt modules on an SWR-2500.  I
designed hundreds of projects like that.  That was a ~1.2 multiplier, and
was at a time when the modules cost $5 per watt; not $1 per watt.  Why be
more conservative now?

  

 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20130327/46bd49bc/attachment-0003.html>


More information about the RE-wrenches mailing list