Grid connected Solar system + a few questions...

[ThaidaGwaii]

Greetings electricians!

 I have quite a few questions regarding how electrical things work here in Thailand.

QUESTIONS:
> Is it possible to hook up to the grid and sell power back to the electrical company using a large solar system in Thailand?

   I would like to contact someone who is doing it...  Any suggestions where to get more information in English?

> I'm debating about getting 3 phase to the house instead of single phase...  Any opinions appreciated.
> 3 phase system:  What is the voltage between L1-L2-L3?  I assume to the common is 220 volts?

 

Thanks!

[Crossy]

1. Yes. As to finding information in English ...  

 

PEA did have the documentation on their website (in Thai) but for some reason I can't find it now. What do you consider "large", up to 10kW is considered a domestic system and has fewer constraints than an industrial system over 10kW.

 

Just how the authorities would treat locations with multiple <10kW inverters I don't know.

 

There are a few members who have installed solar, but as far as i know nothing over 10kW.

 

There is a feed-in tariff system (My Solar Roof) but it's poorly publicized and the requirements/contract are quite restrictive. Most domestic systems simply spin the meter backwards when exporting (net metering), you still need approval from the authorities for this and if you export more than you import you don't get paid for it.

 

2. Is your calculated prospective load over about 50A? Or are you in a remote location? If so investigate 3-phase.

 

3. Thailand is 3-phase, 4-wire. 220V phase-neutral, 380V phase-phase (230/400V in the MEA area). Single-phase loads are supplied phase-neutral.

 

[ThaidaGwaii]

Thank you for taking the time to answer my question with very good answers!

 

PEA tells me I can get 3 phase 30 A to my house...  I'm in Issan, very rural.  I assume power can move either way on that feed...

 

I understand the approval process.  But do you mean if you install solar system for your house without being hooked up to the grid? 

 

I thought of installing a solar array system on a 3 phase 30A service line from the grid, and a system which could support to sell power back to the grid..  Now you tell me they don't buy electricity back???  That is so out of touch with what the world is changing to!  They want to build coal power plants in tourist area like Krabi instead?  Something needs to change here...

 

Not sure what we are dealing with regarding kilowatts size of the array system.  What is the kilowatt capacity of 3 phase 30 A?  Please tell me!

 

Thanks,

 

 

 

[Crossy]

I'm not talking about off-grid or hybrid systems (there are currently no hybrid inverters on the MEA/PEA "approved" list), pure grid-tie only currently. If you are pure off-grid there's no approval, but of course you can't export.

 

Please read my post again, CAN sell to PEA but you need to be on the My Solar Roof scheme. The feed-in tariff is quite generous but read the contract very, very carefully, particularly the future rates.

 

If, like most, you simply use net-metering the meter spins backwards during the day when you're exporting, and forwards at night when you're not. So long as, on average, you generate less than you use there's no issue but if you become a net exporter then any excess isn't paid for.

 

When PEA said 3 x 30A supply was that a 30/100 or 10/30? There's a BIG difference.

 

A 30/100 would support a small factory (about 70kW) and you could do pretty much whatever you want (with the relevant approvals).

 

But I suspect, being very rural, it's a 10/30. This would support about 20kW, but there could be issues with the local distribution network if you bang that much solar on such a limited net. You will need to talk to PEA if you plan anything that big.

 

What is the purpose of your solar? To reduce your power bill, or gain income? How much space do you have for a solar array?

[ThaidaGwaii]

Thanks!

Lots of space, My wife owns lots of land around us.  I just want to save the planet...  Its a political choice.  But I'll take the money, to eventually pay back what I put into it.

 

Thailand ruling class pushing coal plants on places like Krabi is total BS.  It will ruin the local economy and wreck the place.  It's sunny every day here in Isaan...  <deleted>!  Only way it will change is if people like me get involved to push solar.  Anything bigger would require me to go industrial near a main distribution line.  None around me, and I'm too old for starting stuff like that and don't have that kind of money anyway...

 

I'll check regarding 10/30 and 30/100, I don't know.  I suspect you are correct on the lower numbers.
Can you explain what this means? (I'm guessing 10A or 30A per phase...)

 

I guess there is something I miss in my assumptions...  Doesn't installing a power system on an existing grid works as long as the system can handle the KW?  SO if the system can handle 20KW of power feed, you can install 20KW of electricity production on it?

 

THANKS!

 

P.

 

 

 

 

 

 

[Crossy]

The meter sizes are in Amps, the larger number is the maximum load, the smaller the calibration load. So a 10/30 will give you 30A per phase, a 30/100 can supply 100A per phase.

 

The problem with lots of solar on a limited network is one of stability. The inverter relies upon the mains to determine the voltage and frequency it should be operating at. If the network was infinite there would be no issues but it isn't. Pushing power the "wrong way" into a limited network can lead to voltage and frequency skew and all sorts of interesting and undesirable effects.

 

In a nutshell:-

 

The network maintains its stability by having a lot of rotating inertia in all those conventional power plants (think massive flywheels), putting significant amounts of renewables into the mix effectively reduces the inertia and thus the overall stability.

 

Case in point is the Isle of Man, a small island in the Irish Sea. They have a relatively large amount of renewable power and rely upon one of the few AC underwater power links (to the mainland UK) to provide for peak demand, but this link also (being AC) ties the island grid to the rest of the UK and its massive rotating inertia. Losing the link has major ramifications for the island grid as it hasn't enough inertia to maintain frequency and could drift off quite quickly, getting it back in sync is a massive undertaking.