Solar panel installation questions

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Uber Geek

#2046245 29-Jun-2018 22:24

Those optimisers seem to mostly intended to correct for poorly designed systems. Mismatched panels, different panel angles etc. Considering that you can buy solar panels for around $1 per watt output. Instead of spending $1500 on optimisers, get an extra 1.5KW of panels instead.

And since you will have the panels facing in 3 different directions. The panels will never all output peak power at the same time. So you can actually connect slightly more panels than the inverters rated output power if you want. But still important that you group the panels based on which direction they point. (eg NW facing panels to MPPT input A, N facing panels to MPPT input B, NE facing panels to MPPT input C)

MichaelNZ

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#2046246 29-Jun-2018 22:31

pstar008:

1. Hot water timer vs Power diverter?

Some suggested the diverter solution and the timer solution for hot water heating as a cheap alternative, but one odd one suggest timer solution over diverter as he said people complains that the diverter solution can cause the water not been heat sufficiently during winter. Not good if that is true! I am consider a system with roughly 4 kW panel output, unfortunately, it is not all facing north, will be spreed across east, north and west.

Diversion is a waste of time imho. We use gas.

You will need a separate mppt charge controller for each direction. Have you factored this in?

pstar008:

2. 3 kW inverter for a 3kW plus panel output?

As the panel as spread across multi directions, one quoted my a 3kW converter as it can handle up to 4.5 kW output which is exactly the maximum output I am looking at for a premium LG panel solution(320 watt per panel), so it should be fine I guess? But I think I am going to throw 5 kW inverter upgrade for future proof as I am consider install battery in few years, it is too expensive to make finical sense at the moment.

Size your panels for the amount of charge current you need and size your inverter based on peak load, even if this is instantaneous.

pstar008:

3. Panel optimizer or not?

When provide quote, some mentioned panel optimizer, and one don't think I will get best result without using it, at 100 bucks each, it will add about 1500 over the installation cost, how much difference it will make? I am going to look at the data sheet he provided, but real world difference?

4. Smart meter installation?

One does mentioned an optional smart meter installation so that I can see my power usage, otherwise without it, I can only see my solar output. Which is fine as some may not bother to tell that cost upfront, but a $1400 for a smart meter to see my power consumption ( he did mentioned that as my power switch board is full, that's why it's expensive, maybe?)? What's the difference between the one I got from my current power provider?

What the hell is a "panel optimiser"?

I have a check meter installed in my system and it cost me < $100 from Stewarts.

WFH Linux Systems and Networks Engineer in the Internet industry | Specialising in Mikrotik | APNIC member | Open to job offers

pstar008

362 posts

Ultimate Geek

#2046254 29-Jun-2018 23:25

Aredwood:

Those optimisers seem to mostly intended to correct for poorly designed systems. Mismatched panels, different panel angles etc. Considering that you can buy solar panels for around $1 per watt output. Instead of spending $1500 on optimisers, get an extra 1.5KW of panels instead.

And since you will have the panels facing in 3 different directions. The panels will never all output peak power at the same time. So you can actually connect slightly more panels than the inverters rated output power if you want. But still important that you group the panels based on which direction they point. (eg NW facing panels to MPPT input A, N facing panels to MPPT input B, NE facing panels to MPPT input C)

The panel optimiser seem like a replacement for MPPT solution, or cheaper and simpler version of micro-inverter. Based on my research, the solaredge inverter they provided don't have a MPPT and is designed to be working their ower optmizers.

https://www.solaredge.com/products/pv-inverter/three-phase#/

https://en.wikipedia.org/wiki/Power_optimizer

Sorry, the proper term probably should be power optimizer.

Of course, the point is not whether is it useful or not, but cost effectiveness, compare to other solution, like simple MPPT solution, and probably more panels, but to me, my current thinking is not put more panel, but have a more efficient system, so that my roof can have bit more space to be extended in future, my north side seems can put only about four panels maximum.

Your second point is bit more interesting when think about it, the other quote I got is a 2 MPPT inverter, which means, it will not working efficient enough if I indeed put panels into three directions, so I do need the optimizer which was listed as optional. And the other quote give me a two direction roof solution, which looks bit odd, but the inverter is ad Dual MPPT as well, which means it expending into three roof direction will need different inverter or looking for extending that with other solutions in the future.

pstar008

362 posts

Ultimate Geek

#2046256 29-Jun-2018 23:38

1. yes, either MPPT or power optimizer are needed for my setup, I am afraid that I probably used the wrong term for the optimizer.

https://en.wikipedia.org/wiki/Power_optimizer

My understanding is that optimizer is an evolution of MPPT, but comes as more expensive and seem it is not optional with Solaredge inverter they quoted me, either optimzer or non-optimizer and not MPPT for that inverter.

2. Very good point, I'll trying to lookup the datasheet to check the max charge current.

4. I can not find the brand of power consumption meter they quoted, now think about that, it is useful to learning better using my solar energy. I will probably looking at options to buy one and install myself or had someone install one for me. But yeah, I was surprise about the cost of the power meter, and he explained that it is the installation cost, not the meter.

MichaelNZ:

pstar008:

1. Hot water timer vs Power diverter?

Some suggested the diverter solution and the timer solution for hot water heating as a cheap alternative, but one odd one suggest timer solution over diverter as he said people complains that the diverter solution can cause the water not been heat sufficiently during winter. Not good if that is true! I am consider a system with roughly 4 kW panel output, unfortunately, it is not all facing north, will be spreed across east, north and west.

Diversion is a waste of time imho. We use gas.

You will need a separate mppt charge controller for each direction. Have you factored this in?

pstar008:

2. 3 kW inverter for a 3kW plus panel output?

As the panel as spread across multi directions, one quoted my a 3kW converter as it can handle up to 4.5 kW output which is exactly the maximum output I am looking at for a premium LG panel solution(320 watt per panel), so it should be fine I guess? But I think I am going to throw 5 kW inverter upgrade for future proof as I am consider install battery in few years, it is too expensive to make finical sense at the moment.

Size your panels for the amount of charge current you need and size your inverter based on peak load, even if this is instantaneous.

pstar008:

3. Panel optimizer or not?

When provide quote, some mentioned panel optimizer, and one don't think I will get best result without using it, at 100 bucks each, it will add about 1500 over the installation cost, how much difference it will make? I am going to look at the data sheet he provided, but real world difference?

4. Smart meter installation?

One does mentioned an optional smart meter installation so that I can see my power usage, otherwise without it, I can only see my solar output. Which is fine as some may not bother to tell that cost upfront, but a $1400 for a smart meter to see my power consumption ( he did mentioned that as my power switch board is full, that's why it's expensive, maybe?)? What's the difference between the one I got from my current power provider?

What the hell is a "panel optimiser"?

I have a check meter installed in my system and it cost me < $100 from Stewarts.

raytaylor

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#2046261 30-Jun-2018 00:10

The optimisers are an MPPT controller on each panel rather than a shared mppt inverter.

They raise the voltage output of the individual panel which lowers the amps/current so you loose less voltage when transporting it down the cable from the roof to the inverter.

Typically one would wire up 4x 200 watt panels which might put out 36v 5.55amps each in parallel, meaning you are sending 36v 22.2amps down the cable and might loose a few volts. A 3 volt loss would be 66 watts lost. Though if one of the panels gets shaded, its output will drastically drop and you could loose the output from almost a whole panel / 150+ watts, though others will continue perfectly fine.

However you can almost eliminate the transport loss by wiring them up in series so they put out 144v at 5.55 amps and with less amps going down the cable means less voltage lost in transport. The problem with this is if one panel gets slightly shaded, the whole string will be limited by the output of the shaded panel.

Optimizers or mppt controllers for each panel will raise the voltage much higher, lower the amps and push that on to a common bus before going down the cable to the inverter. If one panel is slightly shaded, it will still take whatever power it can get from the panel and invert the panel output to match the high voltage of the other panels, even though the amps coming from the individual panel might be lower.

The benefit is a higher voltage means less amps required to transport the same amount of power thus less voltage lost in transport. While also preventing one panel from bringing down the output for an entire string of panels.

I have seen some that put out 230V direct from each panel, and others that use a higher common rail voltage and then drop it down using a shared inverter.

But honestly, right now the cost of micro inverters / optimizers is not worth it when you can just buy a few extra panels to offset the small bonus in efficiency that they can provide. Its also more things that can go wrong with a system.

If you are saying your main controller-inverter needs the optimizers or micro inverters then i would be looking at a different model.

Definitely look for multiple inputs for each sun direction if you have panels facing different directions, or at least confirm that the panels have blocking /bypass diodes.
If panels in two directions are sharing the same cable, then strings must be made up of panels facing the same direction, parallel to strings facing a different direction. Each panel must have a blocking and bypass diode in it so that power from the strings of direction A doesnt flow into the shaded panels in direction b causing them to warm up and power to be lost through heat.

Ray Taylor

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MichaelNZ

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#2046390 30-Jun-2018 11:57

pstar008:

1. yes, either MPPT or power optimizer are needed for my setup, I am afraid that I probably used the wrong term for the optimizer.

https://en.wikipedia.org/wiki/Power_optimizer

Thanks for that. With a name like "power optimiser", it sounds like some quackery my system is most deficient without. ;-)

raytaylor:

The optimisers are an MPPT controller on each panel rather than a shared mppt inverter.

They raise the voltage output of the individual panel which lowers the amps/current so you loose less voltage when transporting it down the cable from the roof to the inverter.

Thanks @raytaylor.

Based on this I would think "power optimisers" are pointless for a grid tied system. Just go with micro-inverters. This will also solve your issue with having panels in 3 different alignments.

Remember - the higher the DC Voltage -past a certain point - the bigger the PITA factor.

When working with battery banks higher voltage is better - so 48V is better than 24 and a lot better than 12.

But as long as you can stick whatever you are using through 6mm PV cable, go with that. Circa 100VDC is fine (That's 72V nominal). Going to 300V+, as commonly used in larger scale systems comes with it's own set of hassles and risks.

WFH Linux Systems and Networks Engineer in the Internet industry | Specialising in Mikrotik | APNIC member | Open to job offers

MichaelNZ

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#2046394 30-Jun-2018 12:11

raytaylor:

Typically one would wire up 4x 200 watt panels which might put out 36v 5.55amps each in parallel, meaning you are sending 36v 22.2amps down the cable and might loose a few volts. A 3 volt loss would be 66 watts lost. Though if one of the panels gets shaded, its output will drastically drop and you could loose the output from almost a whole panel / 150+ watts, though others will continue perfectly fine.

However you can almost eliminate the transport loss by wiring them up in series so they put out 144v at 5.55 amps and with less amps going down the cable means less voltage lost in transport. The problem with this is if one panel gets slightly shaded, the whole string will be limited by the output of the shaded panel.

To add to @raytaylor contribution -

Unless one is absolutely sure what the Voc (Volts open circuit) rating is at the lowest temperature for the location, then it's a really bad idea to fly too close to the sun.

There are plenty of panels out there where the Voc rating can easily exceed the charge controller's rating on a cold day if wired in strings of 4.

So, strings of 3 are a lot safer.

This assumes a standard charge controller rating of 150VDC. Some charge controllers are higher than this but the same caveat still applies. Know what the maximum possible Voltage for your array strings is.

Also be aware the Voc rating on the back on the PV panel is at 25C / 77F. The Voc figure will be higher on a colder day.

WFH Linux Systems and Networks Engineer in the Internet industry | Specialising in Mikrotik | APNIC member | Open to job offers

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pstar008

362 posts

Ultimate Geek

#2046399 30-Jun-2018 12:28

Thanks all the the input especial a few more technical which I am still digesting.

Micro-inverter is solution more expensive than array of optimizers plus a single inverter right?

If I go with 3-way panel arrangement, I can't go with string converter, thus we are compare with Micro-inverter with optimizer solution, right? Please correct me as I am obviously still catching up.

MichaelNZ

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Integrity Tech Solutions

#2046400 30-Jun-2018 12:31

pstar008:

Thanks all the the input especial a few more technical which I am still digesting.

Let's go back a bit - what are you trying to achieve with this project?

WFH Linux Systems and Networks Engineer in the Internet industry | Specialising in Mikrotik | APNIC member | Open to job offers

pstar008

362 posts

Ultimate Geek

#2046405 30-Jun-2018 12:48

MichaelNZ:

pstar008:

Thanks all the the input especial a few more technical which I am still digesting.

Let's go back a bit - what are you trying to achieve with this project?

High level?

Savings over my power bill and as I am mostly funding it through my mortgage money, I need be careful not paying more than I need to as if I do not want saving over the power end up I am paying more interest.

MichaelNZ

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#2046408 30-Jun-2018 12:52

pstar008:

Savings over my power bill and as I am mostly funding it through my mortgage money, I need be careful not paying more than I need to as if I do not want saving over the power end up I am paying more interest.

I would think pay down your mortgage and / or install gas and / or spend money on saving power (insulation for example if necessary)

Solar PV is not cheap electricity.

WFH Linux Systems and Networks Engineer in the Internet industry | Specialising in Mikrotik | APNIC member | Open to job offers

pstar008

362 posts

Ultimate Geek

#2046418 30-Jun-2018 13:31

You are probably right, and it is good that I haven't commit to Solar yet.

But the mortgage money is relative cheap now. would be good to get an idea of what kind of cost to introduce gas hot water, might be worth considering? Insulation already done, and might be underfloor, will help a bit?

Solar PV is obviously more fun than paying back mortgage, that's the really reason :D

But I am still trying let the number do the talk. I am using this https://pvwatts.nrel.gov/pvwatts.php and added up three different directions.

Most variables I used is relative conservative, but I am not sure about the self consume rate of 60%. It's hard to find real word number for it, and I think part of the reason is that the number range will be varied differently as usage of power can be varied quite bit. Not even sure that realistic, I have baseline consumption of 600 watts upwards, and we cooking simple lunch most of the days.

And I end up with electricity saving annually from 5.5 - 7(?)%, depending on solutions I select and before consider electricity price inflation which was 3% annually from historical data(may or may not going to hold for future, but most likely will I think), and not consider that I can fixed my contract for better buy back rate or switch company for better buy back rate. So I think Solar might just about make the cut as one of the ways can save money?

MichaelNZ:

pstar008:

Savings over my power bill and as I am mostly funding it through my mortgage money, I need be careful not paying more than I need to as if I do not want saving over the power end up I am paying more interest.

I would think pay down your mortgage and / or install gas and / or spend money on saving power (insulation for example if necessary)

Solar PV is not cheap electricity.

MichaelNZ

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#2046420 30-Jun-2018 13:42

pstar008:

Solar PV is obviously more fun than paying back mortgage, that's the really reason :D

(emphasis added)

That is a valid reason - moreso than any environmental claims, as some offer.

My reason for suggesting gas is heating is where the bulk of the power use goes. So if you can offload this to another form of energy you don't need a lot of power. Likely less than 10 units per day.

This means gas for hot water, space heating and cooking. There is a couple of brands of all-gas oven on the market - as in gas for cooktop and oven.

If you look at it this way, electricity from the grid becomes fairly cheap. You use this to run your cpomputer, lighting, TV (If you have one), etc. This strategy also puts in place what you will need should you later decidee to go off grid (if this interests you) but even if you stay connected, gas is cheaper energy than electricity. It's also a bit magical as well.

This suggestion is based on my own personal experience, except I am off the grid, but it's expensive electricty.

If you still want to go the PV route, I would suggest only going for a grid-tied system (ie: no batteries) unless you want to go the full way and go off the grid (keeping in mind this will cost about $30k+). I think this will offer the most benefit for the least expenditure. Batteries are a PITA and I would only recommend their use if you are going the whole way and flipping the bird at the power company (metaphorically speaking - I do not recommend actually doing this or even telling them of any offgrid plans).

If you are around this area (Manawatu) you are welcome to come here and have a look. The basic theory of solar is the same whether grid-tied or off-grid.

WFH Linux Systems and Networks Engineer in the Internet industry | Specialising in Mikrotik | APNIC member | Open to job offers

pstar008

362 posts

Ultimate Geek

#2046458 30-Jun-2018 15:55

Nah, that's cheating, you can't go wrong with that guess, it's so obvious ...

Think about it, go with gas will make PV solution and eventually off-grid much cheaper.

But as you guessed again, I think I am going to stick with PV route, simple because I believe it is the future, but again, as you said: gas can be part of PV solutions, which never really stick to me until now. Thanks for that!

MichaelNZ:

pstar008:

Solar PV is obviously more fun than paying back mortgage, that's the really reason :D

(emphasis added)

That is a valid reason - moreso than any environmental claims, as some offer.

My reason for suggesting gas is heating is where the bulk of the power use goes. So if you can offload this to another form of energy you don't need a lot of power. Likely less than 10 units per day.

This means gas for hot water, space heating and cooking. There is a couple of brands of all-gas oven on the market - as in gas for cooktop and oven.

If you look at it this way, electricity from the grid becomes fairly cheap. You use this to run your cpomputer, lighting, TV (If you have one), etc. This strategy also puts in place what you will need should you later decidee to go off grid (if this interests you) but even if you stay connected, gas is cheaper energy than electricity. It's also a bit magical as well.

This suggestion is based on my own personal experience, except I am off the grid, but it's expensive electricty.

If you still want to go the PV route, I would suggest only going for a grid-tied system (ie: no batteries) unless you want to go the full way and go off the grid (keeping in mind this will cost about $30k+). I think this will offer the most benefit for the least expenditure. Batteries are a PITA and I would only recommend their use if you are going the whole way and flipping the bird at the power company (metaphorically speaking - I do not recommend actually doing this or even telling them of any offgrid plans).

If you are around this area (Manawatu) you are welcome to come here and have a look. The basic theory of solar is the same whether grid-tied or off-grid.

MichaelNZ

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#2046460 30-Jun-2018 16:00

pstar008:

Nah, that's cheating, you can't go wrong with that guess, it's so obvious ...

Think about it, go with gas will make PV solution and eventually off-grid much cheaper.

But as you guessed again, I think I am going to stick with PV route, simple because I believe it is the future, but again, as you said: gas can be part of PV solutions, which never really stick to me until now. Thanks for that!

You must use an alternative energy source for heating if you ever plan to go offgrid.

PV does not produce enough power year round to replace electricity for high demand uses.

Gas is the easiest because it works year round, is a lot of energy for it's storage space and does not require a permit to install.

It's also on-demand - a definite benefit in the warmer months.

WFH Linux Systems and Networks Engineer in the Internet industry | Specialising in Mikrotik | APNIC member | Open to job offers

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