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Some advice needed for a noob


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I'm a complete noob with regards to solar panels. Maybe you can help me in suggesting some directions in the decision process. Thank you very much for your contribution.

 

First, not a big consumption of energy, bill is not higher than 400-500 baht per month. Let's say 4kw per day. Biggest consumer during the day is induction stove 2.2kw, rice cooker 0.8kw and a fridge and water pump. Try to use AC as little as possible. To make the house more comfortable, I want to install roof exhaust fans that will run on free solar electricity during the day. Purpose of a solar installation is self consumption during the day and for the future [when batteries are much cheaper], to store some of the free electricity for evening use and use that to run ACs on stored solar electricity. Not so interested in ROI, UPS or backup scenarios.

 

Here are my questions:

 

1) for the future I would like to add batteries, so I am thinking of a hybrid inverter. On the other hand, hybrid inverters have to work 24x7 compared to grid-tied [with zero export or limiter]. Anyone knows life expectancy of hybrid vs grid-tie at ambient of 30C? Hybrid also need bigger sizing to cater for my high kitchen load [~ 5kW], while grid-tie only need to cater for the PV load, which would typically be around 1.5kW for a 4kw day consumption.  Any recommendation which direction I need to go? 5kW hybrid which I probably will need to replace more often than a 2-3kW grid-tie?

 

2) my pitched roof is oriented east-west, so some shading between morning and afternoon sun. I don't trust micro-inverters  for Thailand due to the heat on the roof [70C], so I'm looking for string inverters that support 2 strings, for each side of the pitched roof. In the beginning I want to generate 1.5kW and later extend it to 3-5kW. Any recommendation for such an inverter, or just put everything on 1 string where most of the sun will shine [west side in afternoon]?  

 

3) i'm worried about the amount of fan noise or other noise that any inverter will make, especially hybrid inverters that work in the evening. The easiest location to install would be near the main circuit breaker box, however located next to the bed room. This area is also warmer than at the other option, the cooler storage room. However would cost extra 20m extension cable.  What would your recommendation be?

 

4) I am considering to have the system installed by a certified electrician, who knows about PEA regulations, how to deal with the difference between DC/AC and know surge protection and proper grounding. Have any of you done similar before? Any advice about essential knowledge that cannot be expected from the average electrician in Thailand? I expect that inverter technology is not the electrician's cup-of-tea. 

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Have a look at this thread, there's also a link to the contractor who seems to be reasonably competent 

https://forum.thaivisa.com/topic/1207148-my-issan-10kw-on-grid-solar-project-fully-installed-by-contractors-337500bht/

 

To directly answer your questions.

 

1.

  • I see no reason that hybrids should be any less reliable than grid-tie when of similar quality.
  • If you choose a grid-tie hybrid rather than a simple hybrid you can make it as small or as big as you like. Any overload will come from the grid (just like a pure grid-tie). Something like this https://www.lazada.co.th/products/i1638698423-s4528348897.html 
  • Note however that the Sofar units won't run without batteries, so a minimal battery pack would be needed from day one. The Huawei units used by @Thaifish appear to be grid-tie hybrids (they have battery terminals) but his are running without batteries.

2.

  • See the link above, two independent MPPT string inputs.
  • We have a Sofar grid-tie, Sofar support from China has been excellent.

 

3.

  • Again see the Sofar, no fan.
  • With the correct size cable the location shouldn't really matter.
  • Our inverter is effectively outdoors (shaded) the heatsink gets pretty warm when it's working hard but not too hot to touch.

4.

  • See the thread linked to above for contractor who knows what's what.

 

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@4myr. Everything you are looking for is in my system I just installed Feb 2021. As @Crossy mentioned have a read of my thread. I could not fault the contractors workmanship they were organized. I did have some software issues which you can read about in my thread. The inverter I installed is a Huawei brand with connections to install batteries at a later date. Part of the installation quote included a Grid Smart Meter (PEA). I was told it could take up to 6 months for PEA to install. I was/am planning on selling power back to PEA for 2.2/1.9 bht p/Kwh. PEA say verbally 2.2bht but I have read and also heard 1.9bht? I have been warned that to install the smart meter there is a lot of paperwork and a PEA inspection of wiring. The reason I am mentioning this is in hindsight maybe I should not have ordered the Meter. One reason is because I have not been exporting as much as I expected. The second reason more importantly is the meter I have already is an older style which spins backwards with export power acting like a battery storage for overnight.   It is illegal but common practice. The Huawei inverters have no fans and does get warm but that is the design. The cooler you can keep the Inverter the more efficient it will be also the longer the cables the more power you will lose over distance. For roof cooling I have set up 3 x 12v car (brushless) radiator fans bought from wreckers and mounted them to the vents. I power them with 3 x 40w solar panels. Good luck if you can find a sparky to do the installation correctly. I have 5 years warranty. @Crossy is on the money with his answers to you. Feel free to PM me.

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@Crossy, thanks for your thoughts.

 

The Sofar hybrid fits the bill, except on the hefty price tag and it needs a battery. Yes it is one of the few hybrids with 5yr warranty. 

 

Due to the high price tag of the Sofar I have been looking at other options, I came across the MUST inverters.

I wonder why the grid-tied versions [3kW and 5kW, also PEA approved] have 5 yrs warranty, while the hybrids [PH1800 models] only 1 yr. Maybe due to higher complexity of firmware and components, so more maintenance/updates needed?

 

The 5 yr warranty is tempting, however I think I'll go for a 5kw hybrid [23-25k baht] first. Batteries can be added later. And I can add a 2nd or 3rd unit to work in parallel, after having more panels on different strings.  The Must hybrid can also disable feed in to the grid. Any thoughts on the reliability and service mindedness of Must inverters in general?

 

@Thaifish, I have not thought of using a car radiator fan for the roof. What a brilliant idea! 

 

They are way lighter than a bathroom 12 inch exhaust fans from Mitsubishi. I need 4 of these [12kg total for the Mitsu's] to have more than 2170 cfm air displacement for my 18x16m2 attic floor. Have you figured out how many cfms your radiator fans support?

 

I will look into your extensive thread. I was first put off by the installation costs, I am not willing to pay. I also don't intend to have a FIT contract and deliver to PEA. Yes I agree with you, any inverter installed must not feed in illegally to the grid, even though my PEA meter is not a smart meter yet.

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17 hours ago, 4myr said:

I have not thought of using a car radiator fan for the roof. What a brilliant idea! 

 

Car radiator fans cost me 500bht each from wreckers.. I had 3 x 12v x 40watt PV panels laying around doing nothing. Not sure of price as I bought them years ago for a dam oxygenator. The radiator fans can handle 80watts so mine are way under powered. I'm deaf but I have asked the Issan Luv Machine if she can hear them running which she said she can but not a bothersome noise. A bonus side is we used to have a rat problem in the roof space which the fans seem to keep them away now. I have not worked out air displacement. I have tell tails hanging outside the vents so I can see the fans are working. 

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