Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inverter

michelb
michelb Registered Users Posts: 9
Hi,
Silly newbie question but would it make sense to use 240W panels instead of 200W panels with Enphase 190W inverters? I'm looking at building a grid tie system for Ontario's microFit program (max cap is 10kw (lower of inverter or panel capacity) so I could do 52x190=9880W on the inverter side and 52x240W=12480W in panels). My thinking is that in peak light the 240W panels will generate the same as the 200W panels but in low light / non optimal conditions, the 240W panels might get me 20% more production (i.e. I'd be closer to peak production more of the time). Is this correct?

Let me know. Thanks, Mike

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve

    I see where you're coming from, as panels tend to average an output somewhat less than their nameplate rating. 80% is typical, so 80% of 240 Watts is 192 which would keep the inverter running at peak output most of the time. The question is: will the inverter suffer from higher output when the sun shines bright on your ol' Kentucky (or wherever) home? Check the Enphase specs for their maximum recommended panel size. Off-grid charge controllers don't really care if there's "too much" Wattage behind them, so long as the input Voltage isn't exceeded. Perhaps the Enphase is the same?

    Edit: just found the specs. Enphase recommends a maximum 210 Watt panel for their 190 model.
  • michelb
    michelb Registered Users Posts: 9
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve

    I did check with Enphase and they said the inverter will support the 240W panel. Elsewhere I read that the M190 inverter will actually output up 199W (I guess anything more DC power is just 'tossed' although I don't know the technical details) so in peak sun, assuming no loss, I'd get 199W from the 200W panel and 199W from the 240W panel (no difference) - what I'm more interested in is when it's overcast or hazy or in the morning / evening when the sun is low, instead of getting maybe 100W from the 200W panel, I would get 120W from the 240W panel - does that make sense? I guess another benefit would be as the panels degrade over the years, I'd still produce closer to peak power (if I lose 20% after 20 years, the 200W panel would then put out 160W, the 240W panel would then put out 192W)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve

    I would have no problem with an 80% rating of a solar panels on my GT system... There are only a few times a year when the panels will output more (hot weather will derate panels more, very cold weather will increase panel output--depends on your area).

    But, for Grid Tied systems--you need to meet the Listing requirements for Enphase to be legal (you should be safe--but that is a different issue).

    MPPT charge controllers and GT inverters should all limit output current/power to their rated limits--unlike PWM charge controllers which cannot limit the current throughput.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • drees
    drees Solar Expert Posts: 482 ✭✭✭
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve

    Yep, as the others have said, it can make sense to use inverters much larger than the 190W rating of the inverters. Enphase recommends a 230W (STC, DC) panel (not sure where you got 210W, Cariboocoot).

    I've seen on the Enphase Enlighten web site that the inverters will output up to 199W AC.

    How often the inverter will reach it's limit before the panels do will depend on the details of your particular install - weather, mounting angle and direction. Can you supply these along with the specific panel you are looking at?

    Enphase has a white-paper where they claim that with a 235W panel you only "lose" 1% of the possible power output and that this goes down as the panels age.

    In most installs output doesn't generally get above 80% of the DC rating of the panel except for short periods of time as the others have said, so it's generally not an issue.

    Here's the link to their whitepaper: http://www.enphaseenergy.com/downloads/Enphase_White_Paper_Module_Rightsizing.pdf
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve
    drees wrote: »
    Enphase has a white-paper where they claim that with a 230W panel you only "lose" 1% of the possible power output and that this goes down as the panels age.

    That sounds fishy, or they are using horrible fright panels. PV panels aren't supposed to age (much). (5% over 20 years)
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve

    Panels do much better than 80%, even in my heat I see more like 90% of STC at solar noon.

    The 80% number thrown around is the net AC values, which covers the inverter, wiring and other losses.
  • michelb
    michelb Registered Users Posts: 9
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve
    drees wrote: »
    ...
    How often the inverter will reach it's limit before the panels do will depend on the details of your particular install - weather, mounting angle and direction. Can you supply these along with the specific panel you are looking at?
    ...

    I'm looking at assembling a ground mounted, 1-axis tracking system near Ottawa, Ontario, Canada. It will be in an open field so there will be no shading issues and no restriction on orientation (probably looking at doing 180 @ 37-38 deg which seems to be optimal according to NREL). I'm planning on using 52 Enphase M190 inverters and 52 panels (210W to 240W or 250W). During the summer months, I'm sure I'll hit the limit at peak sun but I'm hoping that outside that time (e.g. morning, evenings and during the winter when there's not nearly as much sun), I'd gain 5-10+% power output by using the oversized panels.

    Normally it would probably make more sense to just match the panels better to the inverter and just get more inverter/panels to increase production but since I can't exceed 10kw on the inverter, I'm thinking I could still see some production increase with the 'oversize'. Looking at the output graph from a typical solar setup (e.g. http://enlighten.enphaseenergy.com/public/systems/FtN72874), it looks like for most the 'generation time' (period of the day that you're actually generating power), the system doesn't produce at maximum capacity anyway, my thinking is that by using the 20% larger panels, I could bump that curve up so that for much of the day, I generate more power except when I reach maximum in which case, I flatten out. Does this make sense?
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve

    If going ground mount, what do you see as the advantage of going with 52 enphase inverters vs 3 large fixed ones ?

    And for tracking, what is the warranty and repair for the drive gear of the tracker? Vs 4 more panels good for 20+ years ?
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • michelb
    michelb Registered Users Posts: 9
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve
    mike90045 wrote: »
    If going ground mount, what do you see as the advantage of going with 52 enphase inverters vs 3 large fixed ones ?

    I'm actually still on the fence on this and do admit that I need to do more research / education but my initial feeling is to go with the micro-inverters (maybe I should start a new thread for this). As far as I can see, the biggest benefit of using large inverter is the cost. The advantages of the micro-inverter are: I think (without anything to really back them up other than the warranty and what I'm reading) that they are more reliable and last longer, less affected by full / partial shading (at very extreme angles, I suspect the tracking mount will partially shade other panels), ease of installation (no high voltage, no strings), single failure points for panels and/or inverters, ability to mix/match panels (over the lifetime of the system, it's probably not unlikely that I may have to replace some of the panels because of damage or defect). Also, in my case, I'm hoping to create several 10kw installs - at the end of the 20 year contract, I'll likely move all of them to one location, I think (probably incorrectly) that it might be easier consolidating everything if I'm using micro-inverters instead of string inverters (e.g. if I end up with 5 x 10kw installs and eventually, I want to bring them together and have 1 x 50kw install, it may be easier to do with micro-inverters). Lastly, to qualify for the Ontario Government feed-in-tariff, I may need to get "locally" produced inverters (if I get system(s) running this year, I don't, any system(s) I get running next year will probably need to - I can get Enphase inverters that meet this, I'm not sure of which larger string inverters would qualify). As I said though, I'm not decided on this and I'll have to talk to the suppliers and installers before making a final decision.
    mike90045 wrote: »
    And for tracking, what is the warranty and repair for the drive gear of the tracker? Vs 4 more panels good for 20+ years ?

    Tracker is warrantied for 10 years. I need to confirm maintenance on it but from initial conversations it's inspection only. With the tracker, according to NREL, the system will generate over 25% more power. Because of the limitations on the size of the system, I cannot add more panels / inverters since that would exceed the maximum to qualify in the program (also to match the increase generation of the tracker, I'd be adding 14 panels + inverters, not 4, which is probably pretty close to the cost of the trackers (although that's still a moot point since I cannot increase the size of the array)). The other consideration for a tracker is that my area gets snow in the winter and obviously I can't let snow accumulate on the panels or I won't generate anything until it falls off or melts. Most trackers (including the one I'm looking at) will 'rest' in a vertical position which will effectively prevent snow accumulation.
  • drees
    drees Solar Expert Posts: 482 ✭✭✭
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve
    Panels do much better than 80%, even in my heat I see more like 90% of STC at solar noon.

    The 80% number thrown around is the net AC values, which covers the inverter, wiring and other losses.
    Right, and the Inverters are rated by their AC output, so you lose 5% of your 90% output right there.

    Anyway, looking at PTC outputs for a number of 240W panels, most seem to put out between 207-217W DC (1000 W/sq meter, 20*C ambient, wind 1 M/s) which is normally much more realistic. Subtract inverter losses (95%) and that gets you a range of 197W - 206W AC output.
    michelb wrote: »
    I'm looking at assembling a ground mounted, 1-axis tracking system near Ottawa, Ontario, Canada. It will be in an open field so there will be no shading issues and no restriction on orientation (probably looking at doing 180 @ 37-38 deg which seems to be optimal according to NREL). I'm planning on using 52 Enphase M190 inverters and 52 panels (210W to 240W or 250W). During the summer months, I'm sure I'll hit the limit at peak sun but I'm hoping that outside that time (e.g. morning, evenings and during the winter when there's not nearly as much sun), I'd gain 5-10+% power output by using the oversized panels.
    It's going to depend on your exact panel (see above), but I suspect that you will be reaching inverter limits much more frequently than normal because if your tracking system.
    michelb wrote: »
    Normally it would probably make more sense to just match the panels better to the inverter and just get more inverter/panels to increase production but since I can't exceed 10kw on the inverter, I'm thinking I could still see some production increase with the 'oversize'. Looking at the output graph from a typical solar setup (e.g. http://enlighten.enphaseenergy.com/public/systems/FtN72874), it looks like for most the 'generation time' (period of the day that you're actually generating power), the system doesn't produce at maximum capacity anyway, my thinking is that by using the 20% larger panels, I could bump that curve up so that for much of the day, I generate more power except when I reach maximum in which case, I flatten out. Does this make sense?
    Yes, if you are trying to maximize output at the expense of losing some of the potential output of your panels (which it seems like you are trying to do), then using larger panels is the way to go.

    Most of the time people prefer to avoid hitting inverter limits as the inverter is less expensive than the panels. But I still think that even with 240W panels you'll only be hitting inverter limits when temperatures are below 70*F and the sun is within 15-20* perpendicular to your array.
  • michelb
    michelb Registered Users Posts: 9
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve
    drees wrote: »
    ...

    It's going to depend on your exact panel (see above), but I suspect that you will be reaching inverter limits much more frequently than normal because if your tracking system.

    That's a good point, I hadn't thought of that (although I think that in my area, there are so many months that we don't get maximum output that it could still be beneficial)
    drees wrote: »
    ...

    Yes, if you are trying to maximize output at the expense of losing some of the potential output of your panels (which it seems like you are trying to do), then using larger panels is the way to go.

    Most of the time people prefer to avoid hitting inverter limits as the inverter is less expensive than the panels. But I still think that even with 240W panels you'll only be hitting inverter limits when temperatures are below 70*F and the sun is within 15-20* perpendicular to your array.

    Yup, I don't really *want* to lose potential output but I do want to maximize (within a reasonable cost) the amount of power I can generate given that my output is limited the lesser of 10kw DC or 10kw AC installed. Obviously makes more sense to max the output to 10kw AC and then try to figure out how I can generate as much power as I can from that 10kw AC. If I can increase the generation for most of the day by having larger panels at the expense of losing a bit of potential generation at peak then that might be a good trade off.

    Thanks for all the info.
  • trends
    trends Registered Users Posts: 6
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve

    I may be able to help sort you out a little here as I've completed the DC watts in vs the AC watts outs for the Brantford area in southern Ontario. All data based on PVWatts with 2 axis tracker! You can do your regular PVWatts calculation then there is a option to output in text format, paste the text into excel and use excels math functions to do your calc's.

    10KW DC input = 16480KW out with 0hr per yr > then 10KW
    11KW DC input = 18100KW out with 12hr per yr > then 10KW
    12KW DC input = 19704KW out with 93hr per yr > then 10KW
    13KW DC input = 21093KW out with 252hr per yr > then 10KW
    14KW DC input = 22537KW out with 537hr per yr > then 10KW
    15KW DC input = 23653KW out with 836hr per yr > then 10KW

    Somewhere you are going to find your balance between cost to install and revenue recieved (my was 12KW).

    As for inverters fabricated in Ontario, you have other options besides Enphase, Solectria is now shipping Microfit compliant inverters as well as Sunergy (however last I talked to them only 208V was CSA approved). There are a couple more whose names excape me.

    One question I have is that you stated a single axis tracker then commented about 180 deg at 37-38 deg incl so I've assumed you are going with a slew drive but I though I also read sending the array vertical for snow which means you have the capabilities for 2 axis?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve
    Panels do much better than 80%, even in my heat I see more like 90% of STC at solar noon.

    The 80% number thrown around is the net AC values, which covers the inverter, wiring and other losses.

    Actually, the 80% figure I throw around here is the averaged panel output over the "good sun hours", based on personal experience.
    I think Tony's figure of 50% panel rating for AC output is smartly conservative for off-grid systems.:D
  • johnl
    johnl Solar Expert Posts: 30
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve

    I'm considering the exact same trade-offs for a 10kw microFit system in NW Ontario (Enphase vs Solectria, pole-mount tracker vs roof-mount, 215watt vs 230 watt panels).

    I understand that to meet the 40% domestic content rule for this calendar year, only one of either the inverters or the racks must be Ontario made, so long as all the balance-of-system electrical components (wiring, junction boxes, disconnects, lightning arrestors, etc) are purchased from an Ontario supplier, and all the installation services (engineering, electrical, panel and rack install) are provided by Ontario contractors. That is to say, if I purchase a racking system made in the US or Germany, then I have to purchase Ontario-made inverters. Or if I purchase inverters made in Singapore, then I have to purchase Ontario-made racking.

    The Solectria Ontario-made inverters seem to be priced in-line with similar traditional grid-tie inverters - there is little price premium being charged over say a non-Ontario made Solectria or SMA or Xantrex inverter. Similarly, the roof-mount racking systems from Unirac or Dyco seem to be priced about the same as for their non-Ontario product.

    However, Enphase's Ontario distributors are charging a hefty price premium for the M190's coming off the Flextronix line in Ontario compared to the same M190's built in California or Singapore. The Ontario Enphase inverters are going for about $230 to $260 each, while the going rate in the US for the M190s seems to be around $170 to $180. For 52 inverters, that's a $2500 to $4600 price difference.

    The big advantage that I can see for using Enphase in Ontario is that it may significantly reduce the labour cost of the electrical install. Instead of needing someone who specializes in solar to pull the ESA permit and do both the DC and AC wiring to ESA's liking, the DC side of the job is now plug and play for whoever is mounting the panels and racks, and any competent sparky who can handle standard residential 240v AC can do the AC wiring from the junction boxes where each Enphase string terminates on the roof to a breaker box and AC disconnect switch located beside your meters.

    The local solar experts I've talked to tell me that in NW Ontario, a tracker (either single or dual axis) has about a 50% production advantage over fixed-mount for the same amount of installed kW. PVWatts seems to agree. That tells me that unlike with feed-in-tarrif rules in most other jurisdictions, trackers will be quite useful in Ontario to maximize revenue where the maximum amount of panels/inverters you can install is limited by the province to 10kW for microFIT.

    I see that TrueNorth, Sun-Link, and PowerFab all have Ontario-made pole-mount racking, but so far it seems to me that only Sun-Link has an Ontario-made PV tracker, and their model only holds 6 to 8 panels. That suggests to me that a large microFIT system with tracking mounts has to use Ontario-made inverters and perhaps foreign-made tracker mounts like the Watt-Sun AZ-225 or the DegerTraker 7000NT. (Unless anyone knows of tracking components that can be added to another manufacturer's pole-mount system.)
  • michelb
    michelb Registered Users Posts: 9
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve
    johnl wrote: »
    ...
    The Solectria Ontario-made inverters seem to be priced in-line with similar traditional grid-tie inverters - there is little price premium being charged over say a non-Ontario made Solectria or SMA or Xantrex inverter. Similarly, the roof-mount racking systems from Unirac or Dyco seem to be priced about the same as for their non-Ontario product.

    However, Enphase's Ontario distributors are charging a hefty price premium for the M190's coming off the Flextronix line in Ontario compared to the same M190's built in California or Singapore. The Ontario Enphase inverters are going for about $230 to $260 each, while the going rate in the US for the M190s seems to be around $170 to $180. For 52 inverters, that's a $2500 to $4600 price difference.
    ...

    Personally, I'm hesitant to spend the money on Solectria - if I need domestic, I'd get Ontario Enphase (or look for other suppliers - I'm not sure who else is available for microFit). If I went with string inverters (not domestic), I'd probably be looking at SunnyBoy (SMA) or Xantrex. I'm certainly no expert but from the information I've seen, the Solectria just doesn't look as good. The biggest issue for me is that the Solectria comes with a 5 year warranty (SunnyBoy and Xantrex have 10, Enphase has 15) and from the specs (and I really don't know if that means much), the Solectria doesn't look as good to me (400V maximum voltage vs 600V for the others, something like 125-350V optimal range vs 200-550V for the others). Again, I'm far from an expert but I thought the higher voltage was preferable and the others seem to offer more flexibility in install. I'd be concerned about support available for Solectria, monitoring software, replacement parts, etc.
  • michelb
    michelb Registered Users Posts: 9
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve
    trends wrote: »
    I may be able to help sort you out a little here as I've completed the DC watts in vs the AC watts outs for the Brantford area in southern Ontario. All data based on PVWatts with 2 axis tracker! You can do your regular PVWatts calculation then there is a option to output in text format, paste the text into excel and use excels math functions to do your calc's.

    10KW DC input = 16480KW out with 0hr per yr > then 10KW
    11KW DC input = 18100KW out with 12hr per yr > then 10KW
    12KW DC input = 19704KW out with 93hr per yr > then 10KW
    13KW DC input = 21093KW out with 252hr per yr > then 10KW
    14KW DC input = 22537KW out with 537hr per yr > then 10KW
    15KW DC input = 23653KW out with 836hr per yr > then 10KW

    Somewhere you are going to find your balance between cost to install and revenue recieved (my was 12KW).

    As for inverters fabricated in Ontario, you have other options besides Enphase, Solectria is now shipping Microfit compliant inverters as well as Sunergy (however last I talked to them only 208V was CSA approved). There are a couple more whose names excape me.

    One question I have is that you stated a single axis tracker then commented about 180 deg at 37-38 deg incl so I've assumed you are going with a slew drive but I though I also read sending the array vertical for snow which means you have the capabilities for 2 axis?

    Thanks for the info.

    For the inverters, as mentioned in the previous message, there's no other 'domestic' company (that I'm aware of) that appeals to me now other than Enphase.

    For the tracker, I don't know the exact details but the manufacturer stated that it goes to vertical when in rest mode (maybe it's only 70degs and not completely vertical but if nothing else, it's likely better than 35 or 40). I'm actually still early in my tracker assessment so need to do more research there.
  • johnl
    johnl Solar Expert Posts: 30
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve

    SMA is supposed to start production in Ontario in Q4 2010 - likely a bit late for most folks trying to beat the Dec 31 deadline when the domestic content rules go up. Xantrex is planning to start production of their larger GT 100kw and up inverters in Mississauga in August for bigger commercial FIT installs, but I haven't seen any word about smaller inverters suitable for microFIT.

    The Solectria specs don't seem too bad as listed here:
    http://www.solren.com/pvi3000.html
    (200V DC - 550V DC MPPT optimum range, 600V max input voltage, 10 year warranty).

    I'm not really sure about support/warranty issues with any of these inverter companies.
  • michelb
    michelb Registered Users Posts: 9
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve
    johnl wrote: »
    SMA is supposed to start production in Ontario in Q4 2010 - likely a bit late for most folks trying to beat the Dec 31 deadline when the domestic content rules go up. Xantrex is planning to start production of their larger GT 100kw and up inverters in Mississauga in August for bigger commercial FIT installs, but I haven't seen any word about smaller inverters suitable for microFIT.

    The Solectria specs don't seem too bad as listed here:
    http://www.solren.com/pvi3000.html
    (200V DC - 550V DC MPPT optimum range, 600V max input voltage, 10 year warranty).

    I'm not really sure about support/warranty issues with any of these inverter companies.

    You're right about the Solectria, I just noticed that I had been looking at the 2500 specs which aren't as good as the other models (not sure why I clicked on that one - I'd probably want the 5000 anyway ...).
  • trends
    trends Registered Users Posts: 6
    Re: Does it make sense to use 240W panel instead of 200W panel with Enphase 190W inve
    I see that TrueNorth, Sun-Link, and PowerFab all have Ontario-made pole-mount racking, but so far it seems to me that only Sun-Link has an Ontario-made PV tracker,

    Try also Sentinel Power systems