Would an east facing array outperform a west facing array?

[glandpuck]

Ah, somebody mentioned air conditioning. Just remember that panel rating is based on 77 degrees at the panel surface at noon under bright light. ALL panels produce less energy as the panel surface warms. In San Diego county, summer time panel surface can reach about 150 degrees with an ambient temp in the 90's to low 100's and sun out shining. This is when you need the most AC running to keep cool. Your system will produce about 20-30% less energy because besides the panels producing less, so do the batteries if not kept cool and the inverters all degrade above 77 degrees too. So plan for the worst case scenarios when it comes to energy needs and your system sizes.

 

[ksmithaz1]

Yes
It's a bidirectional DC to DC converter.

Hmm, I might be full of it, but I think it's somewhat more involved. I can tell you one of the biggest annoyances I have, that got improved but did not go away completely with firmware, has to do with my load floating just below to just above my PV output. In every case going from battery supplementing to pure PV and back there is a noticeable flicker. It is worse going down, ie when PV production drops below demand and the batteries must supplement. This makes no sense to me, but, ...

Obviously somewhere there must be a voltage up conversion at least on the battery side. I assumed the voltage conversion was at the AC side, since it would be a simple transformer, say 48VAC -> 240VAC 1:4.5 winding or something. Easier to knock down/manipulate the 48V feed to control the output voltage I would think. On the DC side you just need a simple circuit to convert your DC into a nice pretty 0-48V sine wave. You should be able to convert your higher DCV from the panels to 48V with minimal loss as well. But if you were always inverting 48V why the flicker? Then again if your panels are only putting between say 150-500v you can't count on having 240v to push out. Gotta get my neutral from somewhere.

DC-DC upconvert is annoying. I've done it without an IC. You use a choke and a diode with an oscillator on a switch, feeding a big capacitor. You pulse the choke, triggering a voltage spike and hold it with a capacitor. The other method involves series capacitors, where you rapidly switch your DC output to each capacitor in the series with an oscillator and step circuit. Pretty simple if you are just doubling, more complicated to go higher, still dirty DC with a high ripple, then regulate it back down. Switching power supplies do some interesting magic, but they start with AC.

I would love to hear from an engineer on this. It's easy to go down with an electronic switch, much harder to go up cleanly, you have to do some sort of stack & store, as far as I know, but who knows someone may have perfected a heavy duty power IC that magically increases voltage by passing it thru something esoteric.

 

[ksmithaz1]

My experience with some identical 250W panels, would tend to support the 5-10% number. I get 5-7% less total output / panel from an array facing SW at a 25 pitch than from an array laying flat on the ground (I keep moving them around playing). However, the SW facing panels produce usable power about 30 minutes longer/later in the afternoon.

Bottom line is a few extra panels are just not that expensive. You can spend time and dollars on mounting hardware tweaking angles to get an extra 10%, or you can just buy 33 panels instead of 30, and throw them up the cheapest way you can fit them for the same result.

 

[Rabbit]

So on paper east and west should have the same production correct? But like the heat gain through a window, east and west should have the same heat gain but west ends up having more because of higher ambient temperature.

So, since temperatures are lower in the morning(summer time) does it mean east facing panels would be cooler and produce more than west facing panels?

In my area it clouds up and rains far more often in the afternoon than in the morning. So around here I'm pretty confident that east will do better than west. Your mileage may vary, but it's something I'd investigate.

 

[timselectric]

Hmm, I might be full of it, but I think it's somewhat more involved.

It's a whole lot more involved.
But I don't go down the rabbit hole of how the magic happens. I just stick with the overview of what is happening.

I can tell you one of the biggest annoyances I have, that got improved but did not go away completely with firmware, has to do with my load floating just below to just above my PV output. In every case going from battery supplementing to pure PV and back there is a noticeable flicker. It is worse going down, ie when PV production drops below demand and the batteries must supplement. This makes no sense to me, but, ...

This could be either a hardware or software issue.
Something is switching from one state to another.
I know that with my system. This could happen in "solar first" mode. I never had any flickering. But if I were close to the system, I could hear the relay switching.

Obviously somewhere there must be a voltage up conversion at least on the battery side. I assumed the voltage conversion was at the AC side, since it would be a simple transformer, say 48VAC -> 240VAC 1:4.5 winding or something. Easier to knock down/manipulate the 48V feed to control the output voltage I would think. On the DC side you just need a simple circuit to convert your DC into a nice pretty 0-48V sine wave. You should be able to convert your higher DCV from the panels to 48V with minimal loss as well. But if you were always inverting 48V why the flicker? Then again if your panels are only putting between say 150-500v you can't count on having 240v to push out. Gotta get my neutral from somewhere.

It depends on if it's a high frequency or low frequency unit.
Low frequency has a transformer, and does the voltage changing on the AC side.
High Frequency does it on the DC side.
High frequency split-phase units are basically two 120v inverters, stacked inside one enclosure.

I'll stop, now.
This is way off topic, for this thread.

 

[JWLV]

I know NT is New Technology, but what is SE?

I don't know. I thought we were just making up acronyms that nobody else knows.
NT=Night Time, SE=Solar Eclipse

 

[Quattrohead]

I will be using 18 panels east and 18 south for CO, and then adding more later on the west roof that faces away from the road. No one can see what I am up to on the back roof ?