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Rooftop solar eats up all demand in South Australia, world’s most renewable grid
(reneweconomy.com.au)
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this post was submitted on 19 Sep 2023
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In US. I pay my co-op to source my energy from renewables. It's more economical for them to put up solar in fields than it is to have a bunch of tiny roof projects.
So, we have a "tiny roof project" on our rooftop. And it really is tiny since we have a two bedroom home
For 9 hours a day (in winter - 11 hours in summer) they produce four times more power than our peak consumption. When it's cloudy... it produces about twice our peak consumption. In hindsight, we probably could have saved money with an even smaller system... but a bit of headroom is nice and it wouldn't have saved much money, since wiring and the inverter were about the same (we installed the maximum number of panels our inverter can handle).
We also have power now even if the grid goes down during the day - doesn't happen often but it does happen occasionally.
It reduces our electricity bill by between $3 and $9 per day depending on the season.
If we're at home and use a lot of power, we sell between $1.50 and $2 to the grid. If we're out of town and use no power during the day (except the fridge, etc) we sell about $3 per day to the grid.
At that rate, it will only take two years to pay off the upfront installation cost... the inverter has a 10 year warranty and the solar panels have a 30 year warranty. So I'm fairly confident it will last longer than two years.
If we couldn't sell power to the grid, it'd still pay for itself in less than 3 years. Over the life of the system it should easily pay for itself ten times over.
Is it "more economical to put them in fields"? I haven't had quotes for that, we didn't consider it as there are no fields nearby. But our panels are screwed into the roof which took a couple hours. If we put them in fields they would've had to dig concrete footings, put posts in the ground, etc which likely would've been a much bigger project involving multiple contractors instead of just an electrician and two apprentices. There would also need to be underground or overhead wiring to our which, if you do it safely, is a major headache in it's own right.
I'm pretty sure you're wrong about placing them in the field being cheaper. You're underestimating cost and complexity of getting the power from the panels to your home.
The fact is rooftop solar is very simple and very cheap.
As for the "asphalt shingle and roof" being too weak... we have four aluminium bars almost the full length of the building screwed down on the outside of the roof, and the panels are screwed to that. The bars alone are more than strong enough and they spread the load evenly over the whole roof structure - there would be minimal load on the roof and I'm sure it'd work fine on shingles.
Adding onto this, there's a benefit to decentralisation of the grid in general in making it less prone to grid wide problems, and cutting back on the need for transmission as you said (a big deal right now, given conservative farmers have been throwing a tantrum about it of late).
And home and vehicle batteries will help move demand to the middle of the day, meaning less supply needed at night.
I wonder how much effect reduced transmission is having on various things like efficiency because you're using most of the energy where it's being generated.
It's definitely more efficient to use energy close to where it's generated although I'm not sure by how much.
I think the answer is very complex and will depend on many factors.
It kinda becomes irrelevant if you're comparing solar to coal or something anyway. Who cares if solar is "inefficient" if you're replacing coal
We have a powerpal (measures grid usage) and i gotta say, it's absolutely orgasmic seeing that shit show zero grid power used in the middle of winter XD XD
...ok I know different latitudes and all that, but midwinter in melbourne we were still pulling 275kwh over the month and it was a bloody dark month
i can see the “more economical” argument, but it also plays right into the hands of commercial interests… rooftop solar doesn’t allow rent seeking unlike utility solar, which at least makes me question the argument
i’m not sure if you add management overheads (including grid management) and ROI on top of everything that it’d end up more economical, so IMO it’s really a toss up, and in that case i’d lean towards the non-rent-seeking option
if in doubt, invest in yourself; don’t rent your life and all that
In terms of rooftop solar and grid management, this is already a partially solved problem. New solar installs in my part of Australia use “Smart Inverters” that can receive signals to change the rate they’re feeding into the grid. You therefore create a “Virtual Power Plant” of interconnected rooftop solar, that reacts as one system.
https://www.solarquotes.com.au/blog/victoria-smart-inverters-mb1000/
oh yeah totally! i’m in vic too :)
i mean management of the grid to a centralised location IMO is always going to be a bigger cost, which would likely mitigate some efficiency gains from installing solar en masse by a utility
Oh hell yeah :)
It’s actually not as high of a cost as you might imagine. The signals to control the smart inverters actually work through the same system that communicates with smart meters. Which as you know, are already universal here. Whether it’s smart or not, an inverter is an essential part of a solar installation. Part of its job is automatically sensing if there’s a power outage and disconnecting from the grid. This is vital for the safety of repair crews and linesmen.
In talking about utility-level solar though, did you see this article about a prototype project in Western Vic? It’s a combination of solar and storing energy as heated water underground. It can then be turned back into electricity using the process geothermal uses. If I recall correctly, extra electricity from the grid can be fed into the system to be stored as well.
The genius part of that IMO is storing energy as cold, not just as heat.
You need a heat difference to run a heat engine, and the energy lost refrigerating the cold block is more than made up for by making the "waste heat" into usable energy.
Dandrews gov has some great strides to that front, the neighborhood battery initiative is one I'm particularly fond of. Not only islands areas in event of grid failure, but solves the issue of 'overfeed' with shitty street inverters