The Solar system, the numbers.

Solar was installed today, here’s some relevant technical stuff,

heck, it’s not retro related, but, i’m back blogging stuff again!

The solar system installed is quite simple…just panels, inverters, not fancy optimisers or anything else!

32 x Longi – LR5-54HPH-415M – Himo 5M split face solar panels – 21.8% efficiency!! Datasheet – Here . Website link Here

2 x SH5.0RS 5kW solar inverters by Sungrow – User manual – Here

This all adds up to a peak of 13,280 kiloWatts of energy production split over 64 panel segments into 4 strings into two inverters…a maximum of 10kW of production!

the 10kW limit on 13kW of panels…. well, that comes from legislation here in NSW that allows a maximum of 5Kw generation to send to the power company on a single phase for domestic

Our typical power use is over 5kW at any given point, so, we’re allowed two inverters, one to power ourselves during an average day, another to pass excess energy to the grid / provide more power…I’ve ensured that we have ample space to roughly double the number of solar panels and inverters in the future when funds allow…AND, w’re in an ‘Ausgrid’ region which allows 10kW instead of the standard 5kW…

Another factor in limiting sizing comes from the way our government provides incentives to install solar in zone 3 areas! I’m entitled to 146 STC‘s!! which at current rates gives me quite a few grand ‘rebate’ to pay towards the solar system…

an older pic of the roof

And, a picture of the house roof. I decided against the configuration shown which was done via a phone consultation / internet survey – in real life, it wasn’t that practical..

The roofs have a 20 degree slope, and are pretty much North at the top south at the bottom…And, every PV user knows that solar panels should face the equator…So, at least in the southern hemisphere, south facing panels aren’t the ideal situation.

I requested an installation of 16 north facing panels, 16 south facing. (cue every PV armchair expert screaming WHHHHHHYYYYYY)

Well, here’s why.

Back in 2015 when we purchased this place, we had a lovely northen facing roof with several kilometers of thin piping sat on top providing solar hot water (not unlike this –

The neighbour sold up and the new family decided to build a 3rd story….which blocks most of the direct sunlight during winter on all but that top row.

shading is a bad thing for solar panels. One long ‘string’ of solar panels will reduce its entire output, from all panels, even if only a single panel is shaded!.

shading is why people go to the expense of using micro-inverters or DC optimisers , people even argue which ones are best.

Well, those things cost real money, and add more complexity. They have to be installed ‘at the edge’ near the solar panels and, here ,down under when the ambient air temperature often sits in the mid-high 30’s, and on occasion in the 40’s…Putting complex electronics on a black concrete surface in direct sunlight is a bad idea..My day job often involves putting electronics into poles, those things get to the high 60’s internally!

So, lots of extra money, cost complexity to re-gain low double digits in panel output efficiency during shading….OR..just shove more panels on!.

Think about it , I decided to spend around $15k AUD to get 32 panels….maybe if i’d added 32 off $200 inverters, I won’t lose 50% of the power during the day…Yep, $6.4k of electronics will mean I just lose (say) 2 or 3 panels (10%).

Better still, those ‘fancy’ panels I’ve had installed are ‘split face’ – or really just a single panel split into two smaller panels, but tied together. This means when half can be shaded, it’ll still generate full energy from the top half that isn’t…thus not dragging down the whole string quite as much…

Or, to summise. I could spend about half of my 15K budget to roughly half the panels, but they’ll have a 40% increase in efficiency during the winter when they’re partially shaded and be more likley to fail quicker…..Nah

Instead, why not spend most of the budget on fancy solar panels that during peak ideal summer generate twice as much energy, but in high winter, maybe only half. I’ve got ample roof space, so the decision was a no-brainer

AND…more solar on the roof reduces heat getting though the ceiling into the house!

One final benefit of having an over-sized solar system, the ‘Feed In Tarriff’

Here in NSW, we get a (paltry) 7.5c per kWh fed back into the grid . that’s free money really!. If i switched off the entire house and generated 10kWh of electricity, fed into the grid for 10 hours a day 365.25 days a year, I could pay off the $15k in under 6 years……

Given that we’re heading into Autumn here in the southern hemisphere, i won’t know how much power the solar will generate at high noon during the summer solstace (nearly 12.5 hours of sunshine!)…i’ll find out next year

How to fry an egg with the sun…

Add 13.6 kW of solar panels on the roof!

16 off 425 Watt panels this side
And another 16 this side, in two strings due to shading from next door

I’ll detail more about the system and some numbers in the future, but I saw it as a simple choice,

Pay energy bills at XYZ per month

Or, pay an identical repayment on a small loan at XYZ per month.

Really, the math is that basic.

We don’t have a battery, so will have some energy bills, but switching everything to Time Of Use (TOU) will mean we can shave at least 75% off our energy use by simply not using tumble dryer at midnight, or not heating water automatically after sunset!

We chose to pay a $3k deposit to make the math work out such that our predicted energy bills matches the loan repayments…

Anyways, enough waffle, stuff should arrive early next month, then I can really start playing and getting back to Amiga / speccy thingies