Everything Solar Forum

Hi David,

If you are incorporating energy storage into your project, these guys make an interesting 3 phase solution:

https://www.yottaenergy.com/yottaecosystem

Brian

Haven't done 3P before. However something you said triggers a thought. You said 10KW is the largest array for net metering. But then you said a larger one does not make sense, making me think that a larger one is not prohibited. If I am right, if you do put in more than ten, how do they define the largest net payout they will give you? Or if you put in 11KW, they pay you nothing..??..

Also you say string combiners are not allowed below 20KW. String combiners are necessary the minute you hit the max number of panels approaching the OCV of the inverter (More than one string), which will be WAY smaller then 20KW by the number of panels. SO I am confused by that statement...

""There is no way to peace. Peace is the way."
- A. J. Muste"

An interesting quote, but pretty much meaningless and just a play on words, assuming your conclusion not allowed.

Hi:

Thanks for the response. In reverse, my judgement was on the "sound bite", not necessarily the author.

Without penalty, I would spring for the 20KW if monies were available. You will almost always be maxed on the credits to the utility. You will almost never pay for electricity from the utility, even on cloudy days meeting your daily demand. A small 10KWH battery added could take the daily over production and apply to the nighttime load when beyond the max net meter daily, probably bringing you very close to no yearly bill, excluding connection fees. Given the fact that electricity will not be going down, the value of more production in my opinion, is never lost.

The utility telling you adding more production (End result of their comment) is not the best idea is of no surprise. Anyone who makes money on selling an "item" will never tell the customer to go get it for free.

Good luck on whatever you do.....

SOL-ARK  has 30 and 60KW 3 phase hybrid inverters.

Also, the SOL-ARK (and associated "knock offs" from China) now include a nice color LCD touch screen that allows you to CONFIGURE the operation of the inverter in ANY manner you want. If you cannot "backfeed", you simply set the "backfeed" parameter to ZERO, and you will no feed any power back to the utility. In the event of lack of sun, the utility will Still keep the batteries up to snuff, IF YOU PROGRAM IT THAT WAY!.  Really, you can make the inverter operate LITERALLY in any manner you desire. Visit their website, download some user manuals, and you will be totally SOLD on Sol-Ark. MADE IN TEXAS, USA!!  ( I have no association or relationship with Sol-Ark, other than having installed quite a few to VERY happy and satisfied solar clients!) They're NOT cheap, but sometimes YOU GET WHAT YOU PAY FOR!

Hi David,

Without knowing much else about the site and the array azimuth and tilt, possible shading, etc, I will respond generally.  First, it sounds like you do not want to export more than 10kW because after that the credit given is pretty poor. That is fine, but remember the array size, for example, a 20kW array, is the DC rated output under ideal laboratory conditions of temperature, light, cleanliness, etc.  Under those conditions, the light source is a full 1,000 W per square meter, applied directly perpendicular to the panel, and the temperature is cool.  There is also the effiency los of the DC to AC conversion byt the inverter, and any optimizers, as well as losses in the DC and AC cable runs, and losses due to dirt or dust on the panels, and voltage sag during hot days. And, the power output of a fixed array will vary with the position of the sun, with the peak generally only lasting an hour and reduced output before and after that peak.

I would recommend you model your Nature center system, or have those that are quoting it do it, with the model as close to the real system as possible. Then export the expected production and look at the data. SolarEdge's design tool and PVWatts let you export hrly data.  What you will find is that a 10kW (DC) array will rarely produce 80% of 10kW (AC), and when it does, it is only for a few hrs here and there. Also, how much of the solar energy procduced will be used in the nature center and so not exported? If the base load during the day is 1-2kW, then you can add that to your AC production goal.

Depending on where you are and how good the site and solar resource is, it could be that an array of 14kW to 17kW DC capacity would meet your goal of minimizing export above 10kW but still maximize your benefit, and it would cost less per watt than a 10kW system. PV systems get cheaper per watt as their capacity increases, generally.

As for which inverter, most 3-phase string inverters have a capacity much larger than 10kW. Is it 208Y120 service or 480Y277?  Without knowing details it is hard to make a recommendation on brand or model.  For such a small system, microinverters may be the way to go.

Best, Ken