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Nerdishness and Solar power

boyo

Mark Ella (57)
Catalyst - 02/02/2016

Batteries 24 Hour Renewable Power

Dr Jonica Newby investigates home batteries - how they work, why you will want one, how they will change the way we consume electricity & what they mean for the future of the world's power generation.
 

Pfitzy

George Gregan (70)
Quite overcast in Sydney today, so only 14.5 kW generated - basically 3 hours of full sun equivalent.

Today would be one of those days where you let the battery top up, run minimal power all day, and sell as much to the grid as possible. Good news is, because it wasn't hot, I don't need the air con.

I'll be keen to see how the Reposit handles this situation when I'm selling power at market rate instead of bullshit feed-in tariff.
 

Pfitzy

George Gregan (70)
Interesting stories on 730 Report and Catalyst tonight.

730 took the "what is this technology?" route, practically ignoring the history of batteries, then getting the "experts" at Choice in to convince everyone it would take more than 20 years to see a return on Powerwall in particular, based on their sample of 1. But maybe if you were some kind of super-genius you could do it in 14-17.

LOT of assumptions made. Shortcomings in maths notwithstanding.

Catalyst took a scientist's approach - looked at different options, added power sharing (GridCredits) like Reposit, and looked at the future of battery tech. Didn't attach a price figure to it.

But if you go find an online calculator (solarchoice.net.au has a good one) and plug in the figures, even the most pessimistic doesn't blow out past 13 years.

So, Choice Australia, let me be the first to say: Fuck off you twats, and I'll see you on the wrong side of an ROI calculation from my lofty tower.
 

Pfitzy

George Gregan (70)
Oh - I'm basing that on a power generation of 32.68kWh today. That's probably as high as it will get, but if I can grab 6 hours of sunlight most days of the week, I'll be well into the mid-20s.
 

2bluesfan

Nev Cottrell (35)
Have to say I'm impressed with the nerdishness evidenced in this thread. We either have some clever nerds in the GAGR community or there is a lot of Googling going on. Probably both.
 

cyclopath

George Smith (75)
Staff member
Have to say I'm impressed with the nerdishness evidenced in this thread. We either have some clever nerds in the GAGR community or there is a lot of Googling going on. Probably both.
Better than Yahooing, from what I read about where that company is going. I'm sure Pfitzy doesn't Google, as he assures me he knows everything there is to know about tech.
 

Pfitzy

George Gregan (70)
Yahoo are fucked. The misogynists will say its because they put a woman in charge. I just think they were fucked the moment Facebook pushed Google into 2nd place as a content sharing platform.

But I nerdgress.

Just shy of 30kWh today - fucking CANING the electricity generation. Once my meter is installed, and my Reposit setup comes down the tube, maybe as early as next week.
 

Pfitzy

George Gregan (70)
Just figured out my phone number is in the white pages (asked my ISP to stop that) when I got a random call from some random bloke in Melbourne. That was weird.

Price of fame I guess ;)

And yes, I'm asking for it to be silenced again.
 

Pfitzy

George Gregan (70)
This is kicking arse. Stats from the last week

Date - kWh
02/02 - 32.679 (PB)
03/02 - 29.941
04/02 - 14.339 (scattered showers)
05/02 - 21.438
06/02 - 23.456
07/02 - 24.698
08/02 - 31.859

Tomorrow they finish installing the polyphase meter (to allow me to sell power out) and the Reposit device is done shortly thereafter.

So if I can start exporting to the grid for peanuts, that at least starts to take the edge off whatever billing amount is left, and the battery assembly will start to take effect once the meter understands what its doing.
At that point, I start to get a true understanding of how beneficial the battery is, and look ahead to Reposit selling power out of it to ramp up the ROI. Reminder on Reposit - its about GridCredits:

http://www.solarchoice.net.au/blog/resposit-power-gridcredits-trade-homes-energy-on-grid

Let's look at a theoretical scenario - with as many concrete figures as I can get from what I know so far.

First assumption is average consumption of 25kWh per day in summer, with my current provider, Energy Australia, whose numbers are as follows:
  • $0.2226 / kWh inc GST after all discounts
  • $0.7495 / diem connection fee inc GST after all discounts
  • $0.051 / kWh feed in tariff
On a summer's day without panels or battery, I'll be spending $6.31 on electricity. On an average day across the year, I'll be spending $5.65.

To put that into context - if my panels + battery + Reposit allow me to net zero my electricity costs on average, then ROI = 8.14 years based on what I paid for the entire system (the Reposit added $800). That's where I got the original figure.

So here we go:
  1. Based on figures to date, my panels generate around 30kWh on a clear day.
  2. It will need a bit over 7kWh to top up the battery (because science n electrons n shit).
  3. Of the remaining ~23kWh generated, let's say ~15 are used to run the house during the day (when the panels are cranking I set the needs of the house accordingly e.g. washing machine, ironing), with 8 left on the plus side of our equation for now.
  4. That means I still have to cover 10kWh usage this day of the original 25. Remember this now.
  5. Reposit is engaged due to a peak event alert - its a hot day and people are reaching for the air con, with power stations needing to ramp up production. Or something.
  6. The market rate for power goes to 40c / kWh. I sell 4 kWh out of the topped-up battery for $1.60 total.
  7. Of the 8 kWh generated off the panels that we haven't used from above, I top the battery back up (~4.2kWh) and feed 3.8kWh into the grid directly for the peanuts rate (another ~19c with Energy Australia).
  8. Now I have a battery that can deliver around 6kWh to power the house overnight (it doesn't drain 100% of the 7kWh because lithium life span) and still have 10kWh average to cover for this fine summer's night.
  9. So, I need to buy 4kWh from the grid @ $0.2226 / kWh inc GST = $0.8904 plus my connection fee that day of ~$0.7495 = $1.64 (rounded)
  10. I've made $1.79 in power selling total, so my profit is a grand total of 15 cents!
But really, the issue is that I didn't pay for a single cent of electricity that day, net. And this is the factor that blows Choice Australia's "23 year ROI" equation out of the water.

If I sell more power out of the battery, or the Reposit gets a better market rate, ROI is even better. They've seen anywhere up to $1 per kWh which I'm sure is an outlier, so most of my estimates are based on 30-40 cents. As long as its higher than what I pay for electricity per kWh.

You can tweak figures back and forth and get a more or less promising result e.g. my new energy provider (Diamond Energy - who are partnered with Reposit) have a lower price per grid kWh but a slightly higher connection fee BUT a better feed-in tariff. Swings and roundabouts.

And of course, this isn't going to happen every day :) But the closer I stay at net zero on a daily basis, the better things are.

If I don't have Reposit, I have no concerns about topping up the battery and keeping it there. But I can't make as much from selling.

If I don't have the battery, I have to buy power at a far higher price what I'm selling it (up to 4 times).

If I don't have the panels, I'm faced with uncertainty over power prices in general, carbon tax, etc. I'll have that anyway, but on a much smaller scale.

So you can see how investment in each piece of technology adds to the whole equation.

I'll keep this updated as much as possible as time moves forward.

Or I might just start a blog and use my limited web dev skills to get the power feeds straight through for the interest of the general public.
 

terry j

Ron Walden (29)
the reposit controller, it in and of itself is just a 'dumb controller' sitting in your house?

If so, then it don't know shit about the prices it can get at different times thruout the network.

SOOoo, does that mean it is connected 'back to base' (reposit HQ?) and therefore the knowledge required on when to sell and where is controlled from HQ?

How does that all work.
 

terry j

Ron Walden (29)
Ahh, found the answer in the link you gave above

Reposit’s software puts your energy storage device in constant communication with the NEM, so that it ‘knows’ when to sell electricity to maximise your profits, based on parameters such as your home’s energy consumption habits, weather, grid demand, and future energy prices
 

Pfitzy

George Gregan (70)
There you go - its more software than box I suppose. I'm curious as to whether its heuristic (self-learning) or what kind of parameters I have to set up. More as I discover it. The app looks pretty slick.
 

Pfitzy

George Gregan (70)
Polyphase meter didn't go in today because Endeavour Energy are shunts.

But I got a firmware update to the inverter as part of the battery management config, so the web portal now shows the level of consumption as well as export etc. I can more easily start to analyse patterns now based on this sort of data.

Of course, because it can only track the things like self-consumption as of the firmware update, the stats need some time to even out as its only been up for a bit over an hour.


20160209_solaredge.png
 

Pfitzy

George Gregan (70)
The new monitoring has told me just how shitty my ducted air con is in terms of efficiency - pulls about as much as my solar array provides on its own, at fairly low running speed and cooling requirement.

I knew the guy who built this place was a fucking tight arse, but I didn't realise he'd buy the shittiest ducted system he could find.

Becomes a case now of looking at summer as a loss-leader in terms of power versus the other months where I can generate much more. And of course, limiting how often that evil device runs.
 

Pfitzy

George Gregan (70)
Merde! This is today, 5PM, comparison of air con off or on. Fuck a duck... Time to look at getting West-facing windows tinted or shuttered or something.


20160210_AirConComparison 5PM.png
 

boyo

Mark Ella (57)
The new monitoring has told me just how shitty my ducted air con is in terms of efficiency - pulls about as much as my solar array provides on its own, at fairly low running speed and cooling requirement.

I knew the guy who built this place was a fucking tight arse, but I didn't realise he'd buy the shittiest ducted system he could find.

Becomes a case now of looking at summer as a loss-leader in terms of power versus the other months where I can generate much more. And of course, limiting how often that evil device runs.


Do you have appropriate levels of insulation?
Is double-glazing of your windows economic?
External shading of windows (awnings, deciduous trees, etc.) is more efficient than internal shading (curtains, etc.).
 

Pfitzy

George Gregan (70)
Wife refuses to get awnings on the west side of the house, because she doesn't want to make things ugly or something. That side faces the street so she has a point, if not a very good one. The only room on that side (besides garage) is the kids rumpus room, but she is stubborn on this.

Insulation is at appropriate levels, with batts everywhere (except around lighting transformers) and quality sarking under the corrugated steel roof. When I bought the house, it had no batts over the garage, so I fixed that. In addition, I have a solar-powered extractor fan on the roof so the roof space is actually quite mild by comparison.

Double glazing is of limited value in terms of keeping heat out - better in winter for thermal retention, not direct sunlight. Awnings are far better, and will cost far less. But the wife won't be moved. Her comment was "We're not going to keep doing these things just to protect the numbers!"

I feel misunderstood :(
 

blindsider

Billy Sheehan (19)
We put in a solar power system last year and our energy bills have halved. 2 adults, 1 child & 1 toddler. We did the math and the ROI was about 6 years, even with fuck all cents per Kw on power fed back to the grid


Sent from my iPhone using Tapatalk
 

blindsider

Billy Sheehan (19)
Wife refuses to get awnings on the west side of the house, because she doesn't want to make things ugly or something. That side faces the street so she has a point, if not a very good one. The only room on that side (besides garage) is the kids rumpus room, but she is stubborn on this.

Insulation is at appropriate levels, with batts everywhere (except around lighting transformers) and quality sarking under the corrugated steel roof. When I bought the house, it had no batts over the garage, so I fixed that. In addition, I have a solar-powered extractor fan on the roof so the roof space is actually quite mild by comparison.

Double glazing is of limited value in terms of keeping heat out - better in winter for thermal retention, not direct sunlight. Awnings are far better, and will cost far less. But the wife won't be moved. Her comment was "We're not going to keep doing these things just to protect the numbers!"

I feel misunderstood :(

What about electric shut out blinds? We've installed them in a few houses (Aussie john Symonds included). They're pretty good, look tidy and definitely keep the sun out). Also window glazing can cut down a heap of heat. When I did my 'green electricians' course, that was one of the biggest ways hotels and office blocks save on a/c bills. Tinting the office windows!!


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