gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
101011-1553 EST
Have any of you installed enphase inverters?
.
Have any of you installed enphase inverters?
.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
Enphase inverters
- Thread starter gar
- Start date
- Status
- Not open for further replies.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
101011-2123 EST
drive1968:
Yes questions.
Yesterday I went to the fall remodelers show. Talked for a long while with an installer of PV systems. This person seemed quite knowledgeable.
I have been looking at on-line data from a couple local PV installations, and when I calculate the ratio of KWH per year to the WATT rating of the entire PV array I get values in the range of 0.76 to 0.8 . This is southeastern Michigan. This is below what most proponents of PV claim in our region, 1.1 .
The individual suggesting the Enphase micro-inverters claims he can get up to about 1.5 for the ratio using Enphase and Sunpower 225 W panels.
On the other hand the web site for the company the individual works at makes this claim:
Because there are so many inflated claims made for power production I am trying to get some real world data to counter the claims.
In looking at the Enphase literature and arguments I see good reasons for use of their equipment.
If one used Enphase inverters and Sunpower panels in southern Michigan with optimized south facing fixed arrays what will be the real world energy harvest per year divided by the array wattage rating?
Are there any of these installations with useful on-line data?
.
drive1968:
Yes questions.
Yesterday I went to the fall remodelers show. Talked for a long while with an installer of PV systems. This person seemed quite knowledgeable.
I have been looking at on-line data from a couple local PV installations, and when I calculate the ratio of KWH per year to the WATT rating of the entire PV array I get values in the range of 0.76 to 0.8 . This is southeastern Michigan. This is below what most proponents of PV claim in our region, 1.1 .
The individual suggesting the Enphase micro-inverters claims he can get up to about 1.5 for the ratio using Enphase and Sunpower 225 W panels.
On the other hand the web site for the company the individual works at makes this claim:
Here the claim is a ratio of 1.4 to 1.8 .Do we have enough sun in Michigan to produce electricity? Absolutely. Michigan receives over 2000 peak sun-hours per year, on average. You can expect between 1400 and 1800 kWH per year from each kW of PV installed in Michigan. That?s only 15% less than Florida receives and it?s more than Germany. Germany is the global leader in PV with over 3500 MW of PV installed.
Because there are so many inflated claims made for power production I am trying to get some real world data to counter the claims.
In looking at the Enphase literature and arguments I see good reasons for use of their equipment.
If one used Enphase inverters and Sunpower panels in southern Michigan with optimized south facing fixed arrays what will be the real world energy harvest per year divided by the array wattage rating?
Are there any of these installations with useful on-line data?
.
I work in the San Francisco area, so my data will be somewhat different than Michigan. I haven't put together data on a whole year basis, but I looked very closely at a recent installation I did. I installed 24 Sanyo 210W panels, which would be a 5.04 KW system. I used M210-84-240-S12 inverters. During the months of July and August, the peak production averaged a reported 4.48 KW in the peak timeframe and the daily production was about 34 KWh. The panels face South-Southwest and have a good pitch. I don't know how that would work out on a yearly basis, but it seems to me the Enphase microinverters are working fairly efficiently by getting a reported 4.48 KW from a 5.04 KW panel system. By the way, the production that the inverters report seems to be overestimating by about 4% the true amount of power being backfed. I testing with my amp and volt meter and the reported amount was consistently a bit overstated.
Even during October, the production is still pretty good and the peak production is about 3.96 KW, although the production starts later in the morning and stops earlier in the evening. From everything I've read and researched, the Enphase inverters are on par regarding efficiency with the standard centralized inverters.
Even during October, the production is still pretty good and the peak production is about 3.96 KW, although the production starts later in the morning and stops earlier in the evening. From everything I've read and researched, the Enphase inverters are on par regarding efficiency with the standard centralized inverters.
Last edited:
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
101012-1615 EST
drive21968:
Thanks.
What does average peak power mean vs maximum peak power? During the day if there are no clouds or other atmospheric obstructions, then maximum peak power should be about noon in sun time. Sun time is probably displaced from clock time. Is average peak power the average of all of the daily maximum peak powers, or something else? I do not have an Enphase or any manuals on the Enphase.
Whatever average peak power means the ratio you have observed for July is 4.48 KW / 5.04 KW = 0.89 . At the Ypsilanti Food Coop for a previous week, probably means last week, there was a peak power, I believe, of 1.95 KW from a 2.28 KW rated array. This ratio is 0.85 . Good correlation, but may not be significant. Their charts are flaky and I have to guess at what the scales are. Until you have talked with them you do not have any way to make sense of the values, other than qualitative. Their site is http://solar.ypsi.com/index.php?siteDetails=foodcoop .
Your daily production of 34 KWH provides a ratio of 34/5040 = 0.0067 and extrapolated to a year is 2.46 . This will be very high compared to a full actual year of real data. However, California will be higher than Michigan. For the Ypsi Coop from the July data I get 318/2280 = 0.139 . Extrapolated to a year is 0.139 * 12 = 1.67 . For the actual year from May 2009 thru April 2010 the Ypsi Coop was 1643 KWH / 2280 W = 0.72 . Thus, the yearly value was less than half of the extrapolated value from this July. However, the July 2009 production was about 75 % of this July's output.
I like some of the design philosophy of the Enphase inverter. It is totally potted, it can optimize its output for each panel, if one panel or inverter fails the whole system is not down, information is available from each panel without additional wires (depends upon carrier current signals), inverter power dissipation is distributed, inverter temperatures probably run lower than for single inverters, there should not be much RFI noise propagated on the AC lines from the inverters to the main panel, the dual inverter uses a separate parallel bus for the AC rather than sequentially thru each inverter, and the DC voltage is low to the inverter and this reduces the stress level on components.
A claim is that the Enphase starts producing with less light on the panel and in cold climates this clears the panel of moisture, frost, and snow earlier and therefore more daily production than for central inverters.
Do all of the claims, etc., prove out in practice?
.
drive21968:
Thanks.
What does average peak power mean vs maximum peak power? During the day if there are no clouds or other atmospheric obstructions, then maximum peak power should be about noon in sun time. Sun time is probably displaced from clock time. Is average peak power the average of all of the daily maximum peak powers, or something else? I do not have an Enphase or any manuals on the Enphase.
Whatever average peak power means the ratio you have observed for July is 4.48 KW / 5.04 KW = 0.89 . At the Ypsilanti Food Coop for a previous week, probably means last week, there was a peak power, I believe, of 1.95 KW from a 2.28 KW rated array. This ratio is 0.85 . Good correlation, but may not be significant. Their charts are flaky and I have to guess at what the scales are. Until you have talked with them you do not have any way to make sense of the values, other than qualitative. Their site is http://solar.ypsi.com/index.php?siteDetails=foodcoop .
Your daily production of 34 KWH provides a ratio of 34/5040 = 0.0067 and extrapolated to a year is 2.46 . This will be very high compared to a full actual year of real data. However, California will be higher than Michigan. For the Ypsi Coop from the July data I get 318/2280 = 0.139 . Extrapolated to a year is 0.139 * 12 = 1.67 . For the actual year from May 2009 thru April 2010 the Ypsi Coop was 1643 KWH / 2280 W = 0.72 . Thus, the yearly value was less than half of the extrapolated value from this July. However, the July 2009 production was about 75 % of this July's output.
I like some of the design philosophy of the Enphase inverter. It is totally potted, it can optimize its output for each panel, if one panel or inverter fails the whole system is not down, information is available from each panel without additional wires (depends upon carrier current signals), inverter power dissipation is distributed, inverter temperatures probably run lower than for single inverters, there should not be much RFI noise propagated on the AC lines from the inverters to the main panel, the dual inverter uses a separate parallel bus for the AC rather than sequentially thru each inverter, and the DC voltage is low to the inverter and this reduces the stress level on components.
A claim is that the Enphase starts producing with less light on the panel and in cold climates this clears the panel of moisture, frost, and snow earlier and therefore more daily production than for central inverters.
Do all of the claims, etc., prove out in practice?
.
What I meant by peak power is roughly what you described - from about 11 am to 3 pm. Basically when I review the production during the best times of the day, the production was about 4.48 KW. The monthly production I saw for the two summer months is sure to drop further as we head into fall and winter, so it is difficult to know what the whole yearly figure will be, but it will definitely be below 2.46 when months like December and January are factored in. The reason I prefer Enphase is for the reasons you listed. It is true that production starts almost as soon as the sun shines on the panels in the morning and ends shortly before sun set. I think alot of that has to do with the quality of the panels too and not just the inverter. Clouds drop production substantially, but that too is probably largely related to the quality of the panels.
Last edited:
The one area I am disappointed with Enphase is the Envoy monitoring device. The individual inverters communicate their production over the neutral wire and the Envoy is supposed to read those communications so that the production can be reported. The signal from the inverters is either too weak or the Envoy does a poor job of reading the signals. I have had an Envoy 50 feet away and it couldn't read the signal on the neutral. I had to install a new receptacle immediately next to the loadcenter for the Envoy to reliably receive the communications and then I had to run computer wire from the internet so that the Envoy could be online.
- Status
- Not open for further replies.