Solar System Specs for my needs? 12 sqm roof

[ElephantEgo]

I have a building on-grid that needs to run approximately up to 5000 watts at most.

The roof is slanted to the west and only bout 12 sqm.
I have an electrician on staff but do not know which equipment to procure.
1. I heard that investing in a battery is what adds too much cost to solar systems. Is that true? What battery might be recommended or not?
2. It might be preferable to just have the panels -- what kind is recommended?
3. And whatever else is needed/recommended?

 

Thanks in advance!

[Bandersnatch]

Hi Jake 

 

I have 3 x Growatt SPF 5000 ES - 5 kW inverters one would suit your needs. I run it off-grid with a grid connection for backup.

 

Unfortunately panels are 2mx1m = 2 sqm per panel, so you have only room for 6. The 500+ Watt panels are even bigger.

 

What else would you need: brackets and rails for your roof; solar cable extensions; breakers etc. 

 

I have batteries and they are extensive. One option is to use the battery as a big UPS for a separate circuit for your house for low power items during a power cut.

 

I have 3 nRuit 9Kw LiFePO4 they cost me ฿68,000 each

 

My system :

 

 

[007 RED]

Hi Jake,

 

I’m by no means an expert when it comes to creating a solar panel system.  I can only speak from my own experience after having recently designed and installed a small grid tied system on my car port roof, and I don’t wish to sound negative, but I think your proposal to create a 5kW system on a 12m², West facing roof is a little bit over ambitious.

 

Firstly, the area that you have to mount the solar panels is small.  As @Bandersnatch pointed out, most panels measure 2m x 1m (+/- 1 or 2 cm).  This would mean that you will only be able to mount 6 panels onto your roof.

 

At present I believe that the largest solar panels that are available are rated at 455W, so 6 x 455W will only give you 2.73kW maximum, which is far below your desired 5kW.

 

It must be borne in mind that the power rating given by the solar panel manufacturer is under ideal conditions.  That is to say in a laboratory with the sunlight shining perpendicular to the individual cells of the panel, and the panel being maintained at a constant 25C. 

 

In the real world you may need to work on the assumption that you are going to lose approximately 25% of the potential power rating due to the sunlight not hitting the cells at right angles all the time and because of the heat that the panels generate whilst producing electricity plus the heat radiated from the sun.  The higher the temperature of the panel the greater the loss of their efficiency.

 

Hence, the potential 2.73kW created by the 6 solar panels may well only be just over 2kW.

 

Secondly, in order to obtain maximum sunlight, the solar panels need to be facing South, and preferably angled upwards, so that the sun light will strike the panels for most of the day.  Again, it needs to be remembered that the sun is lower to the horizon during the winter months, and this will also reduce the power that the panels can potentially produce. 

 

So unfortunately mounting the panels facing west means that the panels will only get limited sun light for part of the day, hence considerably reducing their potential output.

 

As I mentioned at the beginning, I recently created a small grid tied solar panel system on my car port roof (inspired by @Crossy’s original thread "How about a solar car port on a budget": 

My aim was to reduce our monthly electricity bill by 75%.  Having obtained a printout of our previous 12 months usage from our local PEA, I calculated that I need a system that could in theory produce approximately 1.7kW per day, given 6 hours of good sunlight a day. 

 

Considering a potential efficiency loss of 25%, 1.7kW system would in reality produce nearer 1.2kW per hour, which with 6 hours good sun light per day should in reality reduce our electricity bill by the desired 75%.

 

I opted for 4 x 415W = 1.66kW, half-cut monocrystalline solar panels feeding a 2.2kW GTI inverter.

 

The 4 solar panels are mounted on the South facing aspect of the car port roof as shown below.

 

The inverter and isolator boxes are mounted onto the metal structure under the apex of the car port roof which provides shade and protection from the elements, as shown below.

 

The system has now been operational for just over a month and given that we are currently in the ‘winter’ period with the sun being lower in the horizon, the system is happily producing on average 7kW per day which is about what I originally was hoping for.  Our recent electricity bill (16/12/21) showed that it had been reduced by approximately 75%, over the previous bill.

 

The graph below shows the system's power production for this month (December 21).  Note: the reduced output on the 14th,15th and 16th was because the NO Export device was active due to the meter reader normally coming on the 15th.  Sods law, he came at 10:30am on the 16th.

 

My system is currently fitted with a ‘simple’ manual NO Export device (e.g. light switch) which gets activated the day before the meter reader normally comes (e.g. 15th of the month).  Once he has been the switch is deactivated and surplus power is allowed to feed into the grid.  I have plans of installing Crossy’s automatic No Export device in the near future.

 

FYI... My little DIY system cost approximately 28K THB.

 

I hope my comments are constructive and not destructive.  Best of luck with your proposed project.

 

[007 RED]

In my post above, I mentioned that the solar panels can lose as much as 25% of their efficiency due to a combination of the angle at which the sunlight hits the individual cells which make up the solar panel and the heat generated by the panels and radiated heat from the sun.

 

My 4 x 415 half-cut monocrystalline panels should in theory be capable of producing 1.66kW, but because the sun is currently low on the horizon during the winter season, the system is only producing 1.24kW max at midday as shown in the graph below.

 

It will be seen from the above graph that the system wakes-up at about 06:30am with very low power being produced because the sun is just breaking over the horizon.  The power gradually increases, almost exponentially, as the sun climbs to its maximum at midday.  The output power then slowly reduces, again almost exponentially, until the sun disappears below the horizon at approximately 6:00pm.

 

FYI… On the 8/12/21 it was a good sunny day and the system produced a total of 8.31kW slightly higher than expected.

 

Based upon the above graph, I may well find myself having to 'throttle' the system back during the summer season so as not to run into negative meter readings.

[MJCM]

12 minutes ago, 007 RED said:

Based upon the above graph, I may well find myself having to 'throttle' the system back during the summer season so as not to run into negative meter readings.

Sorry to but in, but may I ask?

 

You are reducing your electric bill by spinning the meter backwards, but what are you going to do when they come UN-announced and they see your Meter spinning backwards (happened to @Thaifish) and give you a NON-Spinning backwards meter. Will you then still see a 75%  reduction of your electric bill??

[007 RED]

1 hour ago, MJCM said:

Sorry to but in, but may I ask?

 

You are reducing your electric bill by spinning the meter backwards, but what are you going to do when they come UN-announced and they see your Meter spinning backwards (happened to @Thaifish) and give you a NON-Spinning backwards meter. Will you then still see a 75%  reduction of your electric bill??

You not butting in... Your making a very valid contribution to the discussion.

 

You make a very valid point and one which was highlighted in @Crossyoriginal solar panel car port thread.

 

Yes it is always possible that the local PEA may turn up unannounced to do some work on their pole which is directly outside our house and we are either out at the time or don't see them in time to flip the NO Export switch.

 

If that does happen, and they do fit a meter that prevents backward spinning, it will not be the end of the earth.  Whilst my target for the system was to reduce our bill by 75%, and it appears to be currently achieving that aim, the system monitoring facility has shown something that I was not really expecting.

 

As mentioned in my previous post, the meter reader historically comes on the 15th of each month at around 10:30am.  Occasionally because of holidays in the month or the 15th falls on a Sunday, he comes a day later, as a result I activate the NO Export device on the 14th.

 

As will be seen from the monthly graph in the earlier post, power production was somewhat down on the 14th and 15th.  During those two days the No Export facility was active, and the current transformer (CT) was then feeding back info to the inverter.  The inverter was then trying to producing only enough output power to match what we were actually using in the house and not exporting any surplus power to the grid, as can be seen in the graph below.

 

 

So if the worse does come to the worse and the PEA do fit a meter to prevents backward spinning, because of our relatively low consumption (average 7units per day) I estimate that the system will still provide sufficient output power to meet 60% plus of our average daily needs.  At night we only have the fridge and a fan in the bedroom on, so quite low consumption.  So not the end of the world.

 

The real worse case scenario would be that the PEA disconnect our supply and tell us to remove the system.   Now that would hurt. 

[BritManToo]

10 minutes ago, 007 RED said:

Yes it is always possible that the local PEA may turn up unannounced to do some work on their pole which is directly outside our house and we are either out at the time or don't see them in time to flip the NO Export switch.

Had mine connected for 2 years, meter reader doesn't seem to care, or PEA doesn't seem to care.

[MJCM]

16 minutes ago, BritManToo said:

Had mine connected for 2 years, meter reader doesn't seem to care, or PEA doesn't seem to care.

Good for you, but Past results is no guarantee of future results ????

 

Remember TiT

[Thaifish]

Good thread!!! My 2 bobs worth being a newbie to solar for nearly a year now. Orientation of panels important.. I have noticed that even though the Sun is low on the horizon I am averaging more production now per day than when the Sun was overhead. In  the wet season I could see my 10Kw system pump out easily 9.5++Kw whereas now the panels are struggling to make 8KW. Even though less KW the average sunshine is greater so more production per day. During the wet season the clouds build up from midday on so panels facing West are not going to be fully efficient. Your orientation is not the best. My 2 bobs worth!

 

For the record I got caught by PEA through my own fault being Cocky running the meter backwards. In a way I wanted to get caught as I thought it might hurry up the installation of the PEA Smart Meter so I could sell power back to them.... Big mistake learnt...!!   

[BritManToo]

7 hours ago, Thaifish said:

I have noticed that even though the Sun is low on the horizon I am averaging more production now per day than when the Sun was overhead.

Me too, but that's because when the sun's overhead it's also monsoon and there's lots of clouds and rain. I've got my panels lying flat.

[DUNROAMIN]

With the cost of power here and at my age solar power is a waste of money, look at enitial cost against what you spend on power every month and for me about 10-15 years before start to re-coup money, I'll be dead by then. Lets not forget breakdowns and replacement parts. I had solar in Oz where it was worth the outlay against power costs per month. Here in Thailand not worth it.

[BritManToo]

16 minutes ago, DUNROAMIN said:

With the cost of power here and at my age solar power is a waste of money, look at enitial cost against what you spend on power every month and for me about 10-15 years before start to re-coup money, I'll be dead by then. Lets not forget breakdowns and replacement parts. I had solar in Oz where it was worth the outlay against power costs per month. Here in Thailand not worth it.

3-4 years to make the money back in Thailand (assuming nothing breaks).

Unless you pay for someone to install it at 3x the materials cost.

I'm already two years in, saving 500bht/month.

[RocketDog]

On 12/18/2021 at 2:28 PM, 007 RED said:

Hi Jake,

 

I’m by no means an expert when it comes to creating a solar panel system.  I can only speak from my own experience after having recently designed and installed a small grid tied system on my car port roof, and I don’t wish to sound negative, but I think your proposal to create a 5kW system on a 12m², West facing roof is a little bit over ambitious.

 

Firstly, the area that you have to mount the solar panels is small.  As @Bandersnatch pointed out, most panels measure 2m x 1m (+/- 1 or 2 cm).  This would mean that you will only be able to mount 6 panels onto your roof.

 

At present I believe that the largest solar panels that are available are rated at 455W, so 6 x 455W will only give you 2.73kW maximum, which is far below your desired 5kW.

 

It must be borne in mind that the power rating given by the solar panel manufacturer is under ideal conditions.  That is to say in a laboratory with the sunlight shining perpendicular to the individual cells of the panel, and the panel being maintained at a constant 25C. 

 

In the real world you may need to work on the assumption that you are going to lose approximately 25% of the potential power rating due to the sunlight not hitting the cells at right angles all the time and because of the heat that the panels generate whilst producing electricity plus the heat radiated from the sun.  The higher the temperature of the panel the greater the loss of their efficiency.

 

Hence, the potential 2.73kW created by the 6 solar panels may well only be just over 2kW.

 

Secondly, in order to obtain maximum sunlight, the solar panels need to be facing South, and preferably angled upwards, so that the sun light will strike the panels for most of the day.  Again, it needs to be remembered that the sun is lower to the horizon during the winter months, and this will also reduce the power that the panels can potentially produce. 

 

So unfortunately mounting the panels facing west means that the panels will only get limited sun light for part of the day, hence considerably reducing their potential output.

 

As I mentioned at the beginning, I recently created a small grid tied solar panel system on my car port roof (inspired by @Crossy’s original thread "How about a solar car port on a budget": 

My aim was to reduce our monthly electricity bill by 75%.  Having obtained a printout of our previous 12 months usage from our local PEA, I calculated that I need a system that could in theory produce approximately 1.7kW per day, given 6 hours of good sunlight a day. 

 

Considering a potential efficiency loss of 25%, 1.7kW system would in reality produce nearer 1.2kW per hour, which with 6 hours good sun light per day should in reality reduce our electricity bill by the desired 75%.

 

I opted for 4 x 415W = 1.66kW, half-cut monocrystalline solar panels feeding a 2.2kW GTI inverter.

 

The 4 solar panels are mounted on the South facing aspect of the car port roof as shown below.

 

The inverter and isolator boxes are mounted onto the metal structure under the apex of the car port roof which provides shade and protection from the elements, as shown below.

 

The system has now been operational for just over a month and given that we are currently in the ‘winter’ period with the sun being lower in the horizon, the system is happily producing on average 7kW per day which is about what I originally was hoping for.  Our recent electricity bill (16/12/21) showed that it had been reduced by approximately 75%, over the previous bill.

 

The graph below shows the system's power production for this month (December 21).  Note: the reduced output on the 14th,15th and 16th was because the NO Export device was active due to the meter reader normally coming on the 15th.  Sods law, he came at 10:30am on the 16th.

 

My system is currently fitted with a ‘simple’ manual NO Export device (e.g. light switch) which gets activated the day before the meter reader normally comes (e.g. 15th of the month).  Once he has been the switch is deactivated and surplus power is allowed to feed into the grid.  I have plans of installing Crossy’s automatic No Export device in the near future.

 

FYI... My little DIY system cost approximately 28K THB.

 

I hope my comments are constructive and not destructive.  Best of luck with your proposed project.

 

Thanks for solid info. It is very useful to this thread.

But please understand that power and energy are two different things.

A panel that produces 1kW for one hour has produced one kilowatt hour. A pump consuming 1kw for an hour will consume one KWh.

It seems that you understand this from your comments, but it's vital to use proper units when discussing engineering especially for neophytes.

 

Remember the Hubble Space Telescope mirror screw up because one group assumed centimeter units and the other inches?

My pool pump runs for five hours a day and consumes [email protected],or approximately 1kW. So without battery storage I need a 1kW panel that will produce that power for at least half the day. On cloudy days it may run intermittently though. Given seasonal variations, inverter losses and other things you mentioned, even having the panel pointed due South I probably would need at least four 500W panels just for the pool. In my case that would probably cut my total monthly consumption in half and I wouldn't worry about grid-tying at all. I'd wire the panel/inverter to the pumps and never touch the house wiring. Your post has inspired me to take a serious look at doing that. Thanks

[bangon04]

On 12/18/2021 at 8:20 AM, 007 RED said:

Based upon the above graph, I may well find myself having to 'throttle' the system back during the summer season so as not to run into negative meter readings.

Some countries / power companies are happy to accept negative meter readings. Are there any possibilities in Thailand?

[DUNROAMIN]

14 hours ago, BritManToo said:

3-4 years to make the money back in Thailand (assuming nothing breaks).

Unless you pay for someone to install it at 3x the materials cost.

I'm already two years in, saving 500bht/month.

Not every body has the skill set for self installation, so as I said the cost out weighs a return for 10-15 years depending on the system you install.

[Crossy]

7 hours ago, bangon04 said:

Some countries / power companies are happy to accept negative meter readings. Are there any possibilities in Thailand?

 

There is a feed-in scheme, they pay about 50% of the retail rate for power you export. It's not the easiest thing to get on and there is an apparent "shortage" of the export meters, at least one member has been waiting for nearly a year after his approved system was installed.

 

Most small (and some not so small ) system owners just spin the regular meter backwards and mitigate the meter reader seeing it.

[007 RED]

15 hours ago, RocketDog said:

(Snip).....

But please understand that power and energy are two different things.

A panel that produces 1kW for one hour has produced one kilowatt hour. A pump consuming 1kw for an hour will consume one KWh.

It seems that you understand this from your comments, but it's vital to use proper units when discussing engineering especially for neophytes.

(Snip).....

Many thanks for pointing out my mistake.  They say your never to old to learn, and today I learnt the difference between kW and KWh (apart from the upper/lower case difference).  Unfortunately it's to late now to go back and edit my original post, so I hope that other members who read it will understand what I was trying to convey.

 

As my school teacher used to write in my school reports, "must try harder next time" ????

 

Good luck with your well pump project.

[Crossy]

3 hours ago, 007 RED said:

kW and KWh (apart from the upper/lower case difference).

 

Actually it's "kWh" although the "h" isn't actually an official scientific unit and is sometimes an uppercase H ???? 

 

Whilst it does matter, most of us understand what's meant. Probably safest to call then "units" ???? 

[MJCM]

 

On 12/24/2021 at 7:30 AM, DUNROAMIN said:

Not every body has the skill set for self installation, so as I said the cost out weighs a return for 10-15 years depending on the system you install.

I agree. but at the moment it's for us a better investment to do the Solar Install (even when if the break even is years) then getting 0,5% interest (or even have to pay interest (yeah in some European countries you have to pay interest to have savings in a Bank Account).

 

Plus electric is only getting more expensive, an increase in the rates (here in Thailand) early next year of 4,63%, plus you also have the proposed vat increase to 10% so that would be another 3% added..

 

Quote

THE Energy Regulatory Commission (ERC) has decided to increase the fuel tariff (FT) rate to 1.39 satang per per kilowatt-hour (unit) during the first four months of next year leading to average electricity rate of 3.78 baht per unit, or a 4.63 percent increase from the current period

 

https://thainewsroom.com/2021/11/19/electricity-bills-set-to-rise-in-2022/

 

So breaking it down

 

I am planning to spend (approx) 300.000 THB on my Solar

 

The bank would give me 300.000 / 100 = 3000 * 0,5% = 1500 THB of interest

With my Solar I suspect that we already have saved 1500 THB in the first 2 months after Solar Installation. And I have then still 10 Months of the year remaining.

 

If you could install it yourself (like @Crossy, @007 RED or @BritManToo) (WHICH I CAN'T) you make lots and lots more profit (and it would be of course cheaper as well)

[ElephantEgo]

Thanks for everyone's comments. Apparently I cannot do this on my small roof and would need to install the panels on the ground instead.

So basically I would need the: panels, the inverter, switch, brackets to hold it together, breakers and the isolation box?

 

I calculated that the panels would run about 70,000 THB (5800 watts) (12x panels at 535 watts each -- spread over 24 sqm)

Other components?

Assuming decent south facing light, what might I be looking at for ROI period?

[BritManToo]

Looks like Global House have been reading @Crossy thread.

If you have a spare 130kbht to spend why not buy a car port (5m x 12m), looks like 30 panels on the top.

https://www.globalhouse.co.th/product/detail/072104095056

 

[ElephantEgo]

It seems like this is the system I need (along with supports to hold them above the ground)?

https://www.lazada.co.th/products/solar-loff-ongrid-hybird-huawei-528kw-3-phase-i2541775272-s9040130519.html?exlaz=d_1:mm_150050845_51350205_2010350205::12:12654756915!117524295342!!!pla-294682000766!c!294682000766!9040130519!505884294&gclid=Cj0KCQiA5aWOBhDMARIsAIXLlkdl0KIVrM66DHeu-2aqCYKEBvk6hHlMedcp1KQTvoWdz17ki-rnpgcaAnrdEALw_wcB

However the return on investment might be like how long (for materials)? Considering I (live in Phuket and) can use south facing.

[BritManToo]

3 minutes ago, JakeR said:

It seems like this is the system I need (along with supports to hold them above the ground)?

https://www.lazada.co.th/products/solar-loff-ongrid-hybird-huawei-528kw-3-phase-i2541775272-s9040130519.html?exlaz=d_1:mm_150050845_51350205_2010350205::12:12654756915!117524295342!!!pla-294682000766!c!294682000766!9040130519!505884294&gclid=Cj0KCQiA5aWOBhDMARIsAIXLlkdl0KIVrM66DHeu-2aqCYKEBvk6hHlMedcp1KQTvoWdz17ki-rnpgcaAnrdEALw_wcB

However the return on investment might be like how long (for materials)? Considering I (live in Phuket and) can use south facing.

The 12 panels are worth 4k5 each = 54kbht

The inverter 75kbht, but there's a wide choice available for under 30kbht, do you really need '3 phase'

 

So 130k for the equipment, 60k for a few bits and pieces seems a little excessive.

[BritManToo]

10 minutes ago, BritManToo said:

The 12 panels are worth 4k5 each = 54kbht

The inverter 75kbht, but there's a wide choice available for under 30kbht, do you really need '3 phase'

 

So 130k for the equipment, 60k for a few bits and pieces seems a little excessive.

Tell you what, pay me the 190kbht and I'll supply and fit a similar 12 panel system for you.

12 x 440w split panels, a 5k inverter (single phase), and I'll throw in a backup generator.

 

PS.

I'll be making 100kbht out of the 190kbht for my work.

[ElephantEgo]

In summary we are looking at about 90k for materials (+ any installation costs if labor is hired).

 

And a short return on investment then?:
Lets say it supplies just 1/3 of my 6000 THB bill. So it'd be paid off in 4-5 years.
Is this realistic and sounds about right?

[Crossy]

7 hours ago, JakeR said:

In summary we are looking at about 90k for materials (+ any installation costs if labor is hired).

 

And a short return on investment then?:
Lets say it supplies just 1/3 of my 6000 THB bill. So it'd be paid off in 4-5 years.
Is this realistic and sounds about right?

 

I reckon you're in the right ball park (assuming on-grid with no batteries). For this to work you need to have a conventional disk-type meter which will run backwards on export (some don't), if you post a photo of your meter (redact the meter ID) we can hazard an educated guess whether it will or not.