Collapse early and avoid the rush

22 06 2020

The title of this post is of course a well known line from John Michael Greer’s masterful blog. I’m using it today, because apart from everything else happening in the world today, we have stretched our off grid solar power system to the limit. I always knew this would happen, but now I’m reporting on how we are literally powerless, even with state of the art equipment….

Intermittence was one of the shortcomings of solar energy that was mentioned in Planet of the Humans and poopooed by the film’s critics. Ten years old, they said, we’ve moved on they said…. Well no, we haven’t moved on. Solar energy is still intermittent.

We’ve been stretching the envelope down here in wintery Tasmania for about a month. Apart from it getting colder, the biggest change is the length of the days. Yesterday was the solstice, and with hills all around us, the sun doesn’t rise until 8am; and it sets before 4:30pm. Then there are the clouds. Lots of them. Don’t get me wrong, clouds down here are beautiful….

Winter sunrises can be stunning

It’s not unusual at this time of year to get no proper sun until 9am. and if your batteries went flat at 2am, and you’re hanging out for a coffee but you can’t even pump water from your taps, it feels like collapse. I’m the first to know if the batteries go flat in the middle of the night, my CPAP machine stops working and tries to suffocate me. Just joking. An alarm comes on to wake me up, just in case.

NiFe batteries don’t ACTUALLY go flat, the inverter spits the dummy when the voltage drops to 32.6V. with everything shut down, the battery voltage starts rising again until a critical voltage is reached and the inverter restarts. But if the blackout was caused by a biggish load, like the fridge, the voltage quickly drops again, rinse and repeat. So I have to get up and turn the fridge off, and the light circuit too, because we have two lights on sensors in the bathrooms, and two remote controlled lights in the bedroom fans which automatically come back on when the power returns. I didn’t know they were designed that way when I bought them, we have to live with it. No biggie. Just more stuff to learn.

But wait there’s more….. if the sun comes out full bore next morning, it will of course start recharging the batteries. Trouble is, I discovered, as soon as the charging voltage of 64.3V is reached, which is the entire system’s maximum operating voltage, the maximum power point tracker charging the battery bank drops the Amps coming in, going into absorption mode, and reducing the power going into the batteries…! I’ve seen our 2.2kW array reduced to producing under 1kW in full sunshine conditions.

Never having lived with off grid solar before, I had no idea of just how inefficient such systems were. So even though we’ve had the odd day or two of reasonable weather, our batteries were never fully recharged. Now that the whole fury of roaring forties winter has been unleashed on Tasmania, we’re bearing the brunt. At midday, total solar input was a paltry 20W. That’s 0.001% of full capacity. The upside is, after more than 36mm of rain by lunchtime, our tanks are overflowing again…

Now I’ve had people say to me, put more panels in, or more batteries, but in truth, none of this would help because a 4.4kW array would put 40W into the batteries instead of 20W. AND would a bigger battery bank ever get fully charged? Not to mention the fact that all that extra capacity would be simply wasted on a bright sunny day.

My son’s been onto me to install a wind turbine as backup, but since getting my personal weather station, I’ve discovered that wind speeds rarely reach the necessary 22km/hr required to reach cut in speed…..

Fans of 100% renewables always make me laugh…. Because living without fossil fuels, as imperative as the need to do so is, means taking the grid off the grid. And good luck with installing huge storage capacity with the economic calamity we’re now facing.

Things could be worse. I’ve just cooked a risotto on the AGA, and to avoid using the pump, we’re collecting the tanks overflow in buckets to washup….. we’re still living way better than at least half the people on the planet. AND for the first time ever, I’ve written a blog post on my phone. It wasn’t quite the ordeal I was expecting either…..

UPDATE

After speaking to my mate Bruce in Queensland who has also bought a bank of NiFe batteries to replace his aging lead acid ones, and who’s having the exact same problem (only with much older equipment) I decided to remove two cells out of service.

This was easy as it turned out, I just loosened three nuts, swung the connector between the two lines of cells over, and retightened the nuts. Those two cells amount to 2×1.65V = 3.7V. The battery bank’s new voltage was then 64.4V – 3.7V = 60.7V. This voltage drop now forces the MPPT to ‘overcharge’ the remaining 38 cells to, theoretically, 1.7V which will increase the battery bank’s storage capacity in the poor winter weather conditions that are normal here. Don’t worry about the ‘overcharge’, you can’t hurt these batteries, they’re pretty well indestructible, that’s why I love them.

Instead of going into absorption mode, the MPPT is now in bulk mode, forcing the whole output of the panels into storage. You can even see the bank voltage has already gone up from 60.7V to 61.2V in just the time it took me to reconnect the system, check everything, and decide to take a photo…… by the end of the day, with a mixture of Sun and clouds, we managed 5.4kWh, the best result in ages. Best of all, the following day of full sun resulted in 7.2kWh, an outstanding result for winter. Our batteries are now full, and the next three days that may bring snow to the hills should be survivable…. some time after the equinox, I will put the battery bank back into normal mode, let’s see what happens…..


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28 responses

22 06 2020
Perry Welsh

Welcome to off grid living dear Sir. We’ve been off grid for over 9 years now and winter is the eternal moderator and the Yamaha 2.4 generator gets an occasional workout in the mornings. FYI, I filled in the western verandah to make another bedroom.craft room and powered it with a 12 volt battery, regulator, small panel, 12v LED’s, car radio etc and works wonderfully. As a retired submariner, I have a red light fitted in the toilet that I turn on at night as night vision is essential when there is no moon. Pitch black is an understatement. You have probably thought of this but a small system like the above will give you lights in an emergency, ie should inverter not want to play. Loving your work mate and updates relished. Keep smiling, as free energy is hopefully not too far away, that’s if you believe it’s out there, hidden from us.

24 06 2020
Glenn

A familiar story.

My super green earth loving friends refuse to even watch the new Moore film.

The solar thing – same here. We usually turn the geni on for a blast early evening. And again first thing in the morning.

Everything gets turned off over night.

Yep … tanks filled some time ago.

Also need to keep an eye on our gravel roads .

Cheers from Cygnet area.

G.

22 06 2020
Chris Harries

Mid summer insolation in Tasmania is five times that of mid winter insolation. To make matters worse we need more lighting and space heating in Winter when solar energy input is at its lowest. That’s why hybrid wood heating coupled with solar is complementary. But doesn’t help with electrical demand.

This one is a bit of a surprise to many.

https://www.lowtechmagazine.com/2020/05/thermoelectric-stoves-ditch-the-solar-panels.html

22 06 2020
mikestasse

I know, I know……. 🙂

22 06 2020
mikestasse

I’ve seen that before, very inefficient, but better than nothing I suppose….

22 06 2020
Hugh Spencer

Thermal converters are very inefficient and think of the EROI! (Bismuth and tellurium too?) – Yes even in the WET tropics of NE Qld, we have had 4 months of shite weather – and despite our fairly large solar array, we have had to run the generator (a Yamaha EF2400 iS – an “inverter generator” – an amazingly tolerant machine we have had for 5 years) – almost every other day. One learns rapidly about the intermittency of solar. Our saviour is our Trimetric 2020 AH meter – as we use AGM cells (Sonnenschein) – a lead acid technology, they must not be discharged below 1/3 capacity, if they are to last. So the Trimetric allows us to easily keep track of discharge levels. I suspect you need someone who understands your system to sort out the MPPT behaviour. We occasionally have had the same problem – and I have had to raise the float voltage limit.

22 06 2020
mikestasse

Andrew Bartlett from It rang me this afternoon after reading my little story, and we discussed my MPPT’s settings….. I may actually lower the float voltage, currently set the same as absorb to 64V and see what happens.

We’ve had the wettest day I’ve ever experienced here, 50mm and the Huon is predicted to flood tomorrow morning.

22 06 2020
Hugh Spencer

Gawd – only 50 mm! Anyway – the idea is to convince the MPPT charger that the batteries are NOT charged – usually by upping the bulk voltage – you are not going to damage the batteries – maybe in late spring ratchet the voltage down a bit – you really need a Trimetric, bugger the weird and wonderful displays on the various units (although I’m not sure a Trimetric would be happy with your voltages) – what battery technology are you using?

23 06 2020
mikestasse

I use a midnite classic, which is state of art and recommended with NiFe batteries because they’ll operate at the wider voltage range the batteries are capable of.

My absorption and float voltage is 64.3V. if the voltage is set higher, the inverter won’t cooperate.

23 06 2020
Hugh Spencer

Ah – NIFE – that complicates things – maybe you should split the battery bank and parallel them – Is your inverter happy at 32V? – the MPPT should be able to deal with that easily. What happened to the big bank of AGMs you showed in an earlier post from Qld? If your components are happy – I’d go for splitting and paralleling – you don’t lose capacity – and you don’t have the voltage problems.

24 06 2020
mikestasse

You’re getting confused….. I never had a big bank of AGM batteries. Wouldn’t touch them with a barge pole! Those cells were sealed wet.

Also my system is 48V.

https://damnthematrix.wordpress.com/2016/10/08/white-mans-magic/

24 06 2020
Hugh Spencer

>You’re getting confused….. I never had a big bank of AGM batteries. Wouldn’t touch them with a barge pole! Those cells were sealed wet.
Also my system is 48V.<

OK – to my knowledge there is no such technology as "sealed wet cells" – they would have been AGM's, judging by the pix.

I'm not that familiar with NiFe – but those elevated voltages don't make sense. Maybe you should check cell voltages under full charge – they should all be within 100 mV of each other.

25 06 2020
mikestasse

Oh but there are, don’t know if they’re still available, by far the best lead acid batteries ever made, used by Telstra. They have recombining caps on them, and can even be laid flat on their sides, which is how the ex Telstra ones I bought were used in the exchange, and how I laid them out in Cooran…

https://damnthematrix.wordpress.com/2010/10/04/powering-up-for-the-collapse/

25 06 2020
mikestasse

I can understand that you can’t make sense of those battery voltages, NiFe chemistry is a completely different mindset. You should REALLY consider switching next time your batteries die!

https://damnthematrix.wordpress.com/2016/03/13/why-i-chose-nickel-iron-batteries/

https://damnthematrix.wordpress.com/2018/07/24/more-on-nickel-iron-batteries/

22 06 2020
Lloyd Edwards

Good to hear things are going ok down in Geeveston. I have also lived thru the low battery Tasmanian winters and now am on-grid and even town water. I trust neither though and have a 7kVA genset (yes fuel is an issue), and only 10000l back-up tank at present. I’m sitting in front of my Esse waiting for a stew to cook. It also helps out the solar hot water at this time of the year, and warms the bathroom radiator.
I trust the new house is warm and comfortable for the winter. It has been interesting to read how it has come along. Would love to come and check it out one day, efficiency is not really the strength of the 1930s west coast cottage we live in. Anyway nice to see you posting again and hope the clouds break regularly.
Lloyd
Strahan

22 06 2020
mikestasse

The house is cosy as, the AGA is supplying food, as we sit in complete darkness with phone batteries going down…!!

Must get some candles…..

23 06 2020
leonard dieckmann

we live in cambodia, do have 2 truck batteries and an inverter for the storms, seems to work well, for computers,fan and internet.
beautiful picture of the sunrise.there in geeveston

23 06 2020
lemmiwinks

As I’ve said for ages, you *can* run a civilisation on renewables, you just can’t run *our* civilisation on renewables. You have to figure out what’s going to get the chop.

24 06 2020
mikestasse

What….. Like most of it…? 🙂

30 06 2020
Mark

Agree, mes, most of it will have to go. And oddly, one casualty will be the internet, at least as we know it.
Fibre will still exist, exchanges will still be there, but damn them data/server hubs chew power and solar don’t operate at night.

27 06 2020
Troy Porter

Hi Mike,
Is it possible for you to locate a water tank uphill (or build a raised platform) so that you can pump a month’s worth of water to it when you have enough power and just gravity feed it in to your house?

27 06 2020
mikestasse

The short answer is no.

27 06 2020
Angella Mount

We’ve been off grid for just over 20 years, welcome to winter Jane Austen style! Most people have a hard time comprehending how we live. I worked out along time ago not to say anything because it just made people who live on grid, but believe tech will save us, really angry. Cheers Angella

13 07 2020
Sam Powrie

Hi Mike, very interesting post as are several of the comments from others. As someone embedded in the grid, I’m particularly interested in the possibilities of lower voltage systems. What is it that won’t run on 12, 24 or 32 volts? Fridge? Freezer? I think your correspondent’s comment about the ‘Jane Austen lifestyle’ is a useful one. I’ve always thought there was good reason for all the servants and co-dependent relationships in those 18th and 19th century novels…

21 07 2020
mikestasse

Hi Sam, yes you can get low voltage fridges and freezers, but they’re double the price, hard to get, and not as efficient as the devices we use. Hence everything here runs on 240V….

22 07 2020
Hugh Spencer

Actually, they are more efficient – especially if you use the chest type (with a controller). They certainly weigh a lot less! Of course the curse of the chest style is access to the contents. We have been lucky in that we found some plastic re-useable packs (ex Woolies, I think) which stack neatly. But you still have to lift them out to get at the next layer. A small DC fan helps as well, as does having the sensor in a small bottle of water (evens out temperature fluctuations).
I’m not surprised that the system operates more contentedly with the reduced voltage – you were pushing the MidNite’s friendship!

22 07 2020
mikestasse

Can you point me to a DC fridge that only consumed 0.1kWh/day…?

22 07 2020
mikestasse

I don’t understand your midnite comment, when I first got the system charging, i had the batteries at 70V for weeks….

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