How about a solar car port on a budget?

[Crossy 27,210]

Some of you may remember us building this back in 2015.

 

 

Thread here https://forum.thaivisa.com/topic/481794-housebuilding-thread/?do=findComment&comment=9603407

 

Well the time has finally arrived for me to get my finger out and actually put some solar on the car port.

 

We spoke to our local PEA office who were quite enthusiastic and helpful until we said we didn't want to join the government scheme (IIRC it's called My Solar Roof), the contract was too long and restrictive and the feed-in rate silly.

 

So, we are NOT permitted to spin the meter backwards (net-metering) - At least not officially "don't let the meter reader see it going backwards" said the supervisor (he's not over enamoured with the government scheme either).

 

That along with the costs associated with doing the job "officially", approved inverters, approved installers (no DIY) decided me to do this on the QT.

 

Luckily for us (but not my wallet) we have a standing load of about 1100 Watts (mostly Madam's koi and the freezers), our base consumption hasn't gone below 1000 W for the last year or so (yes, I'm sad, we keep a log - ok the supply monitor does). So 1000W or so of solar would cover the base without the meter going backwards and still produce a visible saving on the power bill.

 

A quick and dirty estimate:-

 

1000W x 5 hours per day = 5 units per day generated. Times 30 days per month = 150 units per month. @ 4 Baht per unit thats 600 Baht per month = 1 case of beer!!

 

Our bill is usually 5500-6000 Baht so 10% reduction, enough to keep Madam's green desires happy.

 

So I went shopping:-

 

4 x 300W solar panels from Global House - On offer at 3,890 Baht a pop.

2 x 600W WVC micro-inverters from AliExpress -  6,500 Baht for the two including duties and VAT.

 

The cost of the "proper" mounting hardware scared me so a visit to our local steel supplier got us 1¹/2" square x 2mm wall thickness at 300 Baht a 6m length. I got 6 pieces, we don't need it all for 4 panels but I'm going to put all the mounting stuff up whilst I'm in roof-climbing mode. So 1800 Baht.

 

We also need some stand-off parts to keep everything off the actual roof, I had some 3" x 1¹/2" x 2mm "in stock" so I made 36 x 100mm long stand off pieces. This steel would probably cost another 400 Baht or so.

 

Washers, self drilling screws, angle fixings, primer and paint are all from stock, but I doubt they would cost more than a grand or so.

 

So, we've spent about 25 grand to save 600 Baht a month. Payback period 41 months, about 3.5 years. I can live with that.

 

I've not decided how to configure the rest of the roof space (there is room for 18 panels) yet, but if back-feeding remains off the option list I expect something with batteries is going to be on the cards (look up hybrid inverters). This would also provide a whole-house UPS facility and render our (noisy) genset redundant.

 

 

Photos as we progress so hopefully all will become clear.

 

Comments always welcome of course (or I wouldn't be posting).

 

 

[Crossy 27,210]

Ok some photos.

 

The roof spacers look like this, the large (14mm) hole in the top is to allow the driver to get to the head of the self-drilling bolt that will hold it to the roof (drilled through the tile into the roof steel).

 

 

They will work something like this.

 

 

The steel mounting rails primed ready.

 

 

The 600W inverters, each links to two panels.

 

 

And, just in case you don't know what they look like, 4 x 300W solar panels.

 

 

 

 

 

[tjo o tjim 347]

Do you run any air conditioning during the late afternoon?  Might be able to pre-cool things and drop another kW off your demand before investing in batteries. Demand-side management is much cheaper than source-side management with batteries. 

[Crossy 27,210]

27 minutes ago, tjo o tjim said:

Do you run any air conditioning during the late afternoon?

 

At present, no. But I see where you are coming from.

 

I have ordered (it's not arrived yet) the wireless modem that goes with the inverters. I'm hoping to control the export level from my Arduino based power monitoring system https://forum.thaivisa.com/topic/1022293-new-year-project-power-quality-logger/

 

Someone has already developed a program using Node Red IOT software https://github.com/invite-frey/wvc-inverter which I could possibly adapt parts of to run on the Arduino, it only needs to control the output level of the beasties.

 

 

[taninthai 2,334]

Little sketch off how it going to connect up be nice,,how s it connect to main electrics system??

[Crossy 27,210]

12 hours ago, taninthai said:

Little sketch off how it going to connect up be nice,,how s it connect to main electrics system??

 

Something like this:-

 

[taninthai 2,334]

So your cu is dual feed and box of electronics in inverter stops the panels getting fried...ie the juice can only flow one way...didint realise you can set it up this way

Edited September 1, 2019 by taninthai

[Crossy 27,210]

These little inverters are grid-tie, they sync to the mains and add their power to it.

 

EDIT If you are generating more solar than your house is using you will export to the grid (meter will spin backwards).

 

[Crossy 27,210]

Moving right along we start screwing the standoff pieces into position. If this was the house roof I'd put a good splodge of silicon under the part before bolting down, I didn't bother, the odd leak in the car-port won't hurt.

 

 

And the rails get screwed to the stand-offs.

 

[Crossy 27,210]

Warning - solar panels are 'kin heavy when you have to lift them onto the roof

 

Finally, the 4 panels are in place.

 

 

Panels are fixed using plates and long screws into the rails.

 

 

The plates are actually furniture joining plates with a hole drilled in the centre.

 

 

The ends are secured with angle brackets, from the same place as the furniture plates.

 

 

and

 

 

Next job, inverters, after a cuppa!

 

 

 

 

[johng 17,126]

Imagine how much power would be produced if every roof top in Thailand was covered in solar panels..they would (probably) not have to import any electric from neighbouring countries and save billions on gas and oil.

 

[Naam 14,106]

neat job Crossy!

[Crossy 27,210]

I've hooked up the inverters temporarily to check it's all working, then the heavens opened!

 

More photos tomorrow after work.

 

And I look like a ruddy lobster, well toasted 

 

[johng 17,126]

 
And I look like a ruddy lobster, well toasted [emoji20]
 

Lots of free vitamin D [emoji38]
rub some "harng jorakea" AkA aloe Vera on the burnt bits.

[Crossy 27,210]

2 hours ago, johng said:

Imagine how much power would be produced if every roof top in Thailand was covered in solar panels..they would (probably) not have to import any electric from neighbouring countries and save billions on gas and oil.

 

The problem with renewables, and solar in partcular, is that they are often at maximum production when the load is at a minimum and at zero production (at night) when the load is, if not maximum, certainly significant. So either there needs to be conventional backup (which doesn't start quickly and so needs to run inefficiently at small loads during the day) or we need a LOT of storage (a ruddy big battery).

 

Another issue (which may have had a part in the recent UK blackout) is the question of grid inertia. Without the huge flywheel effect of conventional generation (large rotating masses) the grid frequency can vary rapidly and possibly uncontrollably causing renewables (inverter based systems) to drop off-line when they can't follow the variations, reducing the available supply, causing greater frequency instability, causing more renewables to go off-line, causing greater frequency instability ...