Backup down under

[wattmatters]

Quite the jump in value recently as energy tariffs have risen substantially.

And on that, just got notice today of changes to tariffs applying from 1 July:



The tariffs are all cents per kWh, the daily charges are cents per day.
CL = controlled load, a utility controlled circuit for water heating (which I hardly use as I divert solar PV to the water heater)
FIT = feed-in tariff, credit for excess energy sent to the grid

The price changes are pretty rude. Over $2/day for service connection alone.

 

[nezjnr]

Almost exactly what I'm thinking about doing, I'm also going to add some relays in to cut and control power based on predicted solar production.

There is a damping setting for the forecasting if you want to play with that, HA just says it "adjusts the results in the morning and afternoon".

I've got 3 MPP 11kW, and 10 and 5kW GTI. I'm going to move move 4 of the strings from the GTI to my MPP.
Feeding the grid is almost worthless, Maybe in the peak of summer I'll have some of the roof strings plugged in for credits because I'll just produce so much power that it doesn't matter, but my goal is to use every watt I produce, in load or stored to battery.

I think I'm going to run in SBU mode, and just use from recitfiers to feed the inverters/batteries and control them with a relay and HA.

I really wish I had some way to fill my dish washer/washing machine and just let HA run the cycle when Solar is available, but the smart appliances don't seem be that available in Australia or there just way too expensive for that benefit.

 

[nezjnr]

And on that, just got notice today of changes to tariffs applying from 1 July:

View attachment 152925

The tariffs are all cents per kWh, the daily charges are cents per day.
CL = controlled load, a utility controlled circuit for water heating (which I hardly use as I divert solar PV to the water heater)
FIT = feed-in tariff, credit for excess energy sent to the grid

The price changes are pretty rude. Over $2/day for service connection alone.

OUCH!

I'm on Powercor network in Victoria with Momentum Energy.

Daily: $1.2450
Peak(3PM-9PM): $0.25630
Off-peak: $0.14520
FIT: 0.054

I need to export 3kw to "earn" 1kw at off-peak rates, peak is 5kw for 1kw.
I'm entirely on electric, my GPU miners heat the house and I have Heat-pump hot water.

 

[wattmatters]

There is a damping setting for the forecasting if you want to play with that, HA just says it "adjusts the results in the morning and afternoon".

That's for HA's in-built PV forecasting option. It's a neat feature but unfortunately doesn't help in my case as my shade impacts at this time of year are a combination of things which cause production at different times of day to suffer. There's a chimney and various trees in play. The effects vary depending on time of year and when I get my annual tree lopping done.

e.g. yesterday was a lovely clear sunny Winter day. Normally you'd expect a nice curved production line but this is what we get instead:

I really wish I had some way to fill my dish washer/washing machine and just let HA run the cycle when Solar is available, but the smart appliances don't seem be that available in Australia or there just way too expensive for that benefit.

I just set the start delay on our dishwasher to a time I know when the PV output is going to be ample. Usually around 11AM.

I do the same with the washing machine and heat pump clothes dryer. Most modern appliances have start delay options.

I have smart plugs for them but that's just for power/energy monitoring (and for automations to send an alert to our phones that the load is finished). I don't use the plugs for switching power supply on/off. Most smart plugs are not robust enough for that job, they tend to fail eventually. My washing machine smart plug one failed a month or so back even though it is not used to switch power.

The one which I do use for switching is the pool pump. It has a soft start so not so bad and I use HA automation to control when it starts and stops. I used to have delay in the start time to account for solar availability but I don't really need to (it's around a 320 W load) and so the automation adjusts the duty cycle based on an offset to sunrise and sunset, in that way the duty cycle is automatically shorter for Winter and longer for Summer.

Feeding the grid is almost worthless

Here I can still get reasonable value for exporting excess but for sure self-consumption of PV is way more valuable than exporting. The way I look at that is if I can reduce consumption and export instead (as long as battery gets charged), then it's worthwhile.

My last big hurdle is dealing with the ducted aircon consumption which is on grid supply only (too much power/energy to put on the off-grid side). It's OK in the daytime as the grid-PV mostly covers it, so it's at night I am working on various solutions.

 

[nezjnr]

I just set the start delay on our dishwasher to a time I know when the PV output is going to be ample. Usually around 11AM.

I do the same with the washing machine and heat pump clothes dryer. Most modern appliances have start delay options.

My last big hurdle is dealing with the ducted aircon consumption which is on grid supply only (too much power/energy to put on the off-grid side). It's OK in the daytime as the grid-PV mostly covers it, so it's at night I am working on various solutions.

My dishwasher can do that, but not so much the washing machine. The biggest and hardest factor is the Wife factor to be honest, not much of workaround for that.

How much power does your AC use? Is it Single ro Three phase? Don't see many ducted aircon in Victoria.

I had a pallet of Solar panels in my driveway infront of my garage and Sunday monay some peices of shit came and stole 5 panels, must have backed a ute up. I'm blocking my drive way off now with my bins and the empty pallets, need to put a gate or some fence or something up, third time shit has been stollen, but first two were nothing valuable.

The first panel that they stole was damaged as well, window blew the panels I was unloading from the pallet infront into and did some nice damage, not the smartest thieves.

I want to build a raised garden bed with bifacial panels on top in the front, but this really sours my feelings on that.

Have you looked at using any of those wholesale retailers and using your battery to move off and on depending on pricing? Just saw there's a plugin for Amber electric, would be pretty easy to to have HA monitor price and switch to battery as needed, seem like when wholesale is negative you also get paid to use power.

 

[wattmatters]

How much power does your AC use? Is it Single ro Three phase?

It's a single phase unit, rated at 10 kW cooling capacity. It typically draws ~3 kW but can draw more, mostly when it's cold out and being used for heating. Here's a sample from a recent five day period. Used in the evening and mornings sometimes but have tried to limit use of late.

some peices of shit came and stole 5 panels

That sucks. Sorry to hear that.

Have you looked at using any of those wholesale retailers and using your battery to move off and on depending on pricing?

My system is off-grid, there is no possibility to export to the grid. It requires a grid-tied battery system which involves more approvals and costs.

Just saw there's a plugin for Amber electric, would be pretty easy to to have HA monitor price and switch to battery as needed, seem like when wholesale is negative you also get paid to use power.

I think you'll find you need a battery compatible with Amber's system. But yes it's an interesting option for some - there are a few on Whirlpool forums who have been running with Amber smart shift.

You really need to have a lot of flexibility with loads and lots of PV to both be able to satisfy your own demand and have spare capacity to export.

 

[nezjnr]

My system is off-grid, there is no possibility to export to the grid. It requires a grid-tied battery system which involves more approvals and costs.


I think you'll find you need a battery compatible with Amber's system. But yes it's an interesting option for some - there are a few on Whirlpool forums who have been running with Amber smart shift.

You really need to have a lot of flexibility with loads and lots of PV to both be able to satisfy your own demand and have spare capacity to export.

Mine is off-grid only as well, I'd never sign up for a battery export plan they don't seem worth it in terms of income or the cost of certification, certified hardware etc.
Maybe if battery costs and capacities eventually got cheap enough and I had a big enough system and where you could try and sell into the peak times to really milk some money.

We can use our batteries to just go off-grid when peak pricing is in effect, but the problem is the times aren't set for peak pricing it's all dynamic and the peak really peak high.

NEM data dashboard

The NEM's key data points including price and demand, dispatch, and short and medium-term outlooks.

aemo.com.au

Has historical data here, might need to spreadsheet this, I'm also waiting for my retailer to anounce prices increase for July.

Might have a look at the whirlpool thread.

Have you done any monitoring on the effiency of your inverter? how much is it pulling from batteries vs how much AC power is actually supplied?
My three units pull about 1.1A from the grid when in SBU mode ~200W.

 

[wattmatters]

Have you done any monitoring on the effiency of your inverter? how much is it pulling from batteries vs how much AC power is actually supplied?

I trust the accuracy of the Victron shunt but I'm less sure about the accuracy of the the AC output data from the inverter. I could put one of my IoTaWatt CT's on the output but frankly it's not that important as I can't really do anything about it.

It's confounded by the fact I have the grid supply connected to the AC input of the inverter, so during the day typically it's passing through grid power, and even though at night it's in SBU mode there still seems to be some low level of grid power consumption.

 

[wattmatters]

A series of outages over last 24 hours. Yesterday we had two, one for a couple of hours right during peak solar PV hours and another in the afternoon for an hour.

Then again last night from just before 1AM, restored at about 8:15 this morning.

System didn't blink an eye. But I did light a fire this morning as the ducted AC is a grid only appliance.

 

[Nobodybusiness]

Greetings from down under. I live in a home near the small town of Bellingen, in northern NSW, Australia. Glorious country:

View attachment 47709

That's our home at left centre, and obscured by the tree and slightly off the left of the image is a secondary dwelling where my Mum lives. 12 acres, behind our home (to the left) is bushland. Aside from that, the beach I take our dog to is 20-min away:

View attachment 47713

We've been here living the dream for a little over five years now.

While semi-rural (~1km out of town) we have 3-phase grid connected power. What you can't see in the pic above is another building which was originally a builder's workshop, hence the 3-phase supply. That building was in ruins when we got here but I have resurrected it and created a mancave escape with 115m² of indoor mancave goodness.

Before:

View attachment 47723

After:

View attachment 47722

Has since been decked out with bed, furniture, storage, workbenches and is a self contained living space / office / workshop / training facility.

I had installed an 11kW grid tied solar PV array, with a Fronius Symo inverter on the primary dwelling:

View attachment 47725

It's great, has made a massive difference to our power bills and our investment will be recovered inside of 5 years. Our home is all electric except for the hot water in the second dwelling and mancave which each have Rinnai continuous flow gas HW units with 45kg propane tanks. Heating/cooling is all via reverse cycle aircon. Apart from working on the energy supply side with the solar PV, we've also made a few changes on the energy demand side and have managed to reduce our average electrical energy consumption over the past 5 years by 19kWh/day.

That's the good stuff. The downside is rural electrical supply is less reliable than what I was used to when we lived in inner Sydney. With the Fronius meter data I collect, I have been able to keep a complete record of our grid outages and each year we average a dozen longer outages totalling about 36 hours. Plus a lot of shorter brown-out type outages. It's seasonal, with Summer storms being responsible for half the outages.

The longest was a 2-3 days outage after a mini cyclone took out power lines across the district, and it was when we had family staying for holidays with fridges full of all our Christmas food and goodies. Not happy Jan.

It was clear based on our experience over several years that grid outages were going to be an ongoing fact of life here so I did what most probably do and started with a small cheapie generator and lots of extension cords. That was OK and got us through a few outages but it was tedious to set up and put away again, only to have another outage soon after. And once we decided to build the extra dwelling for my elderly Mum to live in, well we were going to need a better solution for some energy security.

So about 18 months ago I decided it was time to have backup power supply wired into the main circuit board. Keeping it simple I started with a 15A power inlet (we are 230V AC here, so that’s enough to handle 3.5kW) which can supply all the home’s circuits via a cutover switch.

View attachment 47726

While the home is supplied via 3-phase, when on back up supply the home is effectively on a single phase supply. We have no 3-phase appliances or loads, and if we did they would not be connected to the backup side of the cutover switch in any case. I kept the oven and induction stove on the grid-only side - and the oven clock tells us when the grid power comes back on, it also makes a bleeping sound on power up so we know when we can cut back over to grid power.

I bought a pre-loved Yamaha EF3000iSE inverter generator with keyed electric start in near new condition for half the new price. It’ll supply up to 2.8kW continuous without problem. It’s quiet and easy to start/use and this has been our mainstay for power backup and we’ve been very glad to have it.

However, despite how easy it is to use, the wife is still not keen all that keen on using the generator when I’m not home, plus if we were both not home my Mum would have little hope of turning it on.

Hence I wanted to move up another step with our backup power system to make it even easier to use and also provide automation for my Mum for the occasions when we are both away.

So I’ve started an off-grid inverter/battery/solar project. Since this post has been long enough already, I’ll end it here and next post will be about that part of the project.

Dang. That’s a beautiful view.

 

[wattmatters]

Today marks one year since I put the LiFePO₄ battery into service to join the sealed lead acid backup system bank.

Since then the system has discharged 2.9611 MWh, an average of 8.11 kWh/day.

The value of the discharged energy was A$754 while it consumed A$78 worth of supplemental charging from our grid PV system (i.e. foregone export credit, while most of the charge energy comes from our off-grid PV array). That's a net discharge value of $676 ($1.85/day).

In recent months our grid import tariffs have gone through the roof, so the net daily value of battery discharge has increased substantially and since 1 July has averaged $2.85/day.

With fewer hours available to discharge as Spring and Summer roll on I expect that daily value will drop back.

Balancing that is our cottage, our second dwelling - the home we build for my (now late) mum a few years ago, will be occupied once again, by a young couple so it will be interesting to see the effect on our consumption.

The cottage is fully covered by the off-grid system.



The battery has really contributed to a significant reduction in energy imported from the grid over the past year, as has the smart PV diverter for our water heating system. Combined they have reduced our grid imports by ~ 13 kWh/day.

Long term trends with our grid energy imports:

 

[wattmatters]

Our power distribution company is pretty responsive with outages, lots of time they are 1-3 hour duration, typically a power line brought down by something even though they do a lot of work keeping trees clear of the lines.

Occasionally the outage is a lot longer, or is scheduled for maintenance / upgrade works. Glad to have our system which keeps us power on through. We've had several 8+ hour outages this year.

Water supply outages are less common but they too can happen.

On Monday night, after a day or two of slightly lower than normal water pressure we discovered the water main right where it feeds our water meter down by the fence line of our property had sprung a "leak", i.e. it was gushing up through the ground. I found it at dusk and rang the local Council (who are also our local water authority). Being after hours my call was put through to an after hours call centre.

To their credit Council guys were there within an hour and worked to repair it during the evening. It required them to shut off the mains further upstream and that required negotiating with some local businesses, including a restaurant, about shutting off the water supply. So they waited until 8pm to shut off the mains while they did what they could in the meantime. Repair was done by about 9pm. Another crew came first thing the next morning to clean up the mess and fill the hole.

The clamp around the main which secures the tap into the main pipe had broken.



They couldn't remove the clamp, at least not within a reasonable time, so they just knocked it up along the pipe a bit to give room to fit the new tap and clamp.



Then a new connection to the water meter and the next morning the crew cleaned up.



They were glad the problem got called in as the town supply had lost 400,000 litres more than normal. I'm just glad it was on their side of the meter!

We have some local water storage for backup, just one 4000 litre tank with water collected by the cottage roof.


It's not set up as a potable supply, mainly it's for garden use but is plumbed into the cottage for the toilet and washing machine if we needed to use it for that.

It could certainly be used for drinking/cooking with some secondary treatment/filtering, so we do have an emergency water supply should it be needed.

 

[wattmatters]

Balancing that is our cottage, our second dwelling - the home we build for my (now late) mum a few years ago, will be occupied once again, by a young couple so it will be interesting to see the effect on our consumption.

The cottage is fully covered by the off-grid system.

They finally moved in night before last.

I have the IoTaWatt energy monitor and the cottage consumption is recorded, along with my mancave and all our home's circuits.

So I can provide them with daily and hourly consumption data if they like.



They are not separately charged for their use of power, so it's more for their interest/education.

It also helps me to understand our own consumption and impacts of our own strategies to reduce energy use.

 

[wattmatters]

BMS SOC measurement drift.

I'd noticed that my two older (13 months) server rack batteries had begun to show their SOC was lower than it actually was. The 6 LED SOC indicator would show only 4 or 5 LEDs lit when fully charged. It's been getting worse and last week the SOC indicator on their displays was somewhere in the 70-80% range. The newer Jakiper battery is still showing 100% at end of charging.

It's just a classic case of BMS SOC measurement drift and why relying on BMS for SOC should be done with caution. I have a shunt on my system and use that for SOC.

My batteries are set to charge to 56.4 V (an average of 3.525 V/cell). As a result my batteries' BMSs never invoke any high voltage protection. However these PACE BMSs are made to reset the SOC to 100% only if an over voltage protection occurs (not an ideal way to reset SOC but that's how they do it). Else they just count energy in/out and so gradually the indicated SOC drifts away from reality, seemingly erring on a slow drift downwards.

So I decided to do a once-off charge up to a higher voltage to invoke an over voltage protection in the batteries. Once the batteries where close to full I reset the charge voltage setting to 57.0 V, then to 57.4 V and they took a tiny bit more charge (not much) and voltage rose quickly. Sure enough the BMS took action with cell over voltage protection and SOC was reset to 100% on each.

Let them sit at the higher voltage for ~ 10-min and took a look at the cell voltages. The delta for the two older batteries was ~ 60 mV. The newer Jakiper was ~ 40 mV. Then I reset the charge voltage back to 56.4 V.



Interesting behaviour during that final ramp up in voltage, with the BMSs cutting charging off, looks like back on briefly at times and off again, perhaps as the cells settled / rebalanced and fell back under a threshold. The three server rack batteries operate independently, no communications.

These batteries are also in parallel with my SLA backup bank, so the very small tail current at the end was going to them.

 

[wattmatters]

Added a new power flow card to my Home Assistant dashboard.



Shows the PV output from grid tied and off-grid PV arrays, battery power (DC), grid power flow and proportion of imports which are low carbon, plus individual consumption by the water heater (uses a PV diverter) and the second dwelling (cottage).

 

[wattmatters]

Have a new backup battery:



64 kWh battery on board. It has V2L capability (I have the adapter on order) and a fair chunk of that capacity would be available for backup power delivery if needed.

I'll need to test the V2L power output, it's nominally 2.4 kW (240 V AC) but I believe it can do 3.6 kW. I know some in the UK have tested up to close to 7 kW.

Even 2.4 kW would be very helpful for any particularly long grid outages beyond the capacity of my existing home system. I have 15 kWh of LiFePO4, plus 20 kWh of sealed lead acid backup reserve. I consider 10 kWh of that as being for regular outage coverage, while the balance of the SLA capacity is for emergency, no solar happening / can't get the generator going scenario.

 

[Hedges]

What I'd like to see is any surplus PV going to EV, and power drawn from EV as needed for house/load.

How do you integrate EV with your system, or does it just serve as "backup generator"?

 

[wattmatters]

What I'd like to see is any surplus PV going to EV, and power drawn from EV as needed for house/load.

Car is charging with the granny charger this morning (using the grid-PV):



Also the home battery is charging from the off-grid PV array, the smart PV diverter is sending power to the water heater and I am still exporting some energy to the grid. This was the status a bit before 9AM this morning.

I have a smart EVSE station with OCPP on order and when that's connected it will be able to vary the charge rate into the car between ~1.6 kW up to 6.6 kW depending on how much excess grid-PV capacity there is. It will (mostly) avoid the need to import energy from the grid to charge the car.

How do you integrate EV with your system, or does it just serve as "backup generator"?

I have no intention/need to attempt to regularly run the home from the EV. I have my grid-PV and off-grid PV/battery system which does that.

I consider the V2L as a third/fourth level of backup and a convenient AC power supply when away from home if we ever need it.

I have our daily cycling battery capacity, reserve battery capacity, a generator and now the V2L option with the EV.

 

[curiouscarbon]

driving to a (hopefully nearby) DC fast charging station to recuperate ~60kWh of backup capacity in ~2 hours seems like a nice reassuring extra option to have during an outage. of course, such stations might not be operating when residential grid outage is occurring.

nice visualization of the sources/sinks!

 

[wattmatters]

driving to a (hopefully nearby) DC fast charging station to recuperate ~60kWh of backup capacity in ~2 hours seems like a nice reassuring extra option to have during an outage. of course, such stations might not be operating when residential grid outage is occurring.

Our nearest fast chargers are about a half hour drive away on the highway (north or south), so there is a fair chance they would not be affected unless it was a very wide area outage. The one to the south is a 75 kW charger and the one to the north is a 350 kW charger. My car can only charge at up to 150 kW. Still, a couple of hours for the round trip and charge would see us with enough backup reserve for several days.

The car does limit how much you can use for V2L, I think the floor is 20% SOC, which is ~14 kWh. A drive home from the fast charger would use about 6 kWh, so call it 20 kWh which isn't useable capacity, leaving up to 44 kWh as extra backup reserve.