What's the longest you've gone without a sunny day?

CALLD · May 2015

One thing I love doing is collecting data. I've been collecting a lot on my batteries, charge controller, inverter, panels, wiring and the weather.

The weather is by far the most notorious!

I'm going on 13months of collecting data on the weather and I'm struck by a very strange phenomenon - I've not seen a perfectly clear and sunny day since April 22nd! That's 34 days!!!

It's not actually as bad as it sounds because it's also been 57 days since I've seen a totally gloomy overcast day...

Today was shaping up to be the first clear sunny day to break the dull stretch but noon produced some high level cirrus clouds (yet again) to dash that prospect.

What's interesting to me is last year was totally different. The month of May had 12 sunny and clear days, 13 partly cloudy or hazy days, 6 very cloudy or overcast days. Where I live the climate is classified as "oceanic", but due to the latitude of 34° South it is considerably sunnier than other places with this climatic designation like London for example. Annual expected insolation at ground level on a flat surface is 1650kwh per m2.

Last year the climate didn't vary by much throughout the year, with nearly as many sunny days as cloudy days with the rest in between. So what is going on at the moment? Why are the best days only producing a sort of hazy sunshine?

Is it El Niño?
Is it a recent volcanic eruption?
Is it climate change?

I don't think anyone knows...:(

SolarPowered · May 2015

Some of my grid tied micro inverter systems are at 98% harvest for this month. All built out to 110%. Worst month for harvest in 7 years recorded.

mike95490 · May 2015

Nov 2014 19 heavy cloudy days in a row. 38 genset hours
Dec 2014 22 heavy cloudy days in a row. 77 genset hours
Jan 2015 30 genset hours (groups of 4 & 5 cloudy days)
February 2015 13 heavy cloudy days in a row. 20 genset hours

The genset (3Kw) hours were no longer than 3 hours each day, usually 90min AM and 90 min PM, to provide BULK charge only, no absorb. NiFe batteries are much more forgiving, having no sulfation issues.

CALLD · May 2015

mike95490 wrote: »

NiFe batteries are much more forgiving, having no sulfation issues.

I'm strongly considering moving away from lead acid chemistry for my next set of batteries for this reason.
Taking the need for getting a fully saturated charge out of the equation is the best bet for any renewable energy system as it may iliminate the need for a genset if your array is large enough and complimented with wind turbines...

froggersix · May 2015

SolarPowered wrote: »

Some of my grid tied micro inverter systems are at 98% harvest for this month. All built out to 110%. Worst month for harvest in 7 years recorded.

i think he means off-grid systems because grid doesn't matter you just use it when there's no sun.

H2SO4_guy · May 2015

We had 17 days without much sun at all and I still haven't had to run a genny for almost 2 years. During that 17 days, I did heat with propane instead of batteries however.

mike95490 · May 2015

CALLD wrote: »

I'm strongly considering moving away from lead acid chemistry for my next set of batteries for this reason.
Taking the need for getting a fully saturated charge out of the equation is the best bet for any renewable energy system as it may iliminate the need for a genset if your array is large enough and complimented with wind turbines...

There are some other drawbacks to NiFe, such as electrolyte replacement every 5-10 years, lower efficiency 70% vs 80% lead acid, lots of water usage..... So there is that to consider

kaipo_boy · May 2015

mike95490 wrote: »

There are some other drawbacks to NiFe, such as electrolyte replacement every 5-10 years, lower efficiency 70% vs 80% lead acid, lots of water usage..... So there is that to consider

I would have added HIGH INITIAL COST to that... that's the one that makes a difference to me anyway

Photowhit · May 2015

Last Nov(early Dec) we had 14 days with 1 hour of direct sun total.

Dave Angelini · May 2015

CALLD wrote: »

This is my daily production graph since mid-December, as you can see the weather is very unstable year-round where I am. There was a week-long stretch between Christmas and New Year where I made less than I would have in this time of year were it sunny. But looking at the peaks (which show what is possible on a clear sunny day) it shows just how much cloudy weather there has been lately. The sudden jump in production in February was when I expanded my array and got an MPPT charge controller, the red dotted line is an assumption of what it would have been if I had the expanded array from the start of this record.

I have good friend up near Victoria and he says the same thing. The difference is I talked him into installing alot more solar. There is a magic point offgrid where 3 or 4 thousand watts of panels just makes it all good. You charge almost always, you don't need a generator in the right locations like yours, and you basically do not have to do much but verify it is working.

Three days is about our max up in the mountains.

CALLD · May 2015

Dave Angelini wrote: »

I have good friend up near Victoria and he says the same thing. The difference is I talked him into installing alot more solar. There is a magic point offgrid where 3 or 4 thousand watts of panels just makes it all good. You charge almost always, you don't need a generator in the right locations like yours, and you basically do not have to do much but verify it is working.

Three days is about our max up in the mountains.

Yes a 4kwh array would satisfy nearly all my needs in summer except when it's very hazy hot and humid (aircon use soars and production drops), but in winter it would fall a little short. With a serious energy efficiency drive I could make it work though. My ultimate goal is to get up to about 7kw PV, 48v/ 1500Ah battery system - then I'd never have to worry about a generator or grid power again...

BB. · May 2015

CALLD wrote: »

then I'd never have to worry about a generator or grid power again

Famous last words... Until the batteries start to fail, an inverter goes bad, 2 weeks of bad weather, etc... Then backups (genset, fuel, spare parts, grid, etc.) are handy until you can get resupplied.

-Bill

CALLD · May 2015

BB. wrote: »

Famous last words... Until the batteries start to fail, an inverter goes bad, 2 weeks of bad weather, etc... Then backups (genset, fuel, spare parts, grid, etc.) are handy until you can get resupplied.

-Bill

I would disagree, with a system of this calibre - 7kw array, 72kwh battery bank - one would have 2 inverters to provide redundancy. The battery bank would be high quality and there would be 2 charge controllers as well. Monitoring of the system would allow sufficient time to identify battery problems before it results in a catastrophic failure. The PV array is sized to provide double the required power on a typical day so that on the worst days it is mostly still sufficient. In your worst case scenario of "two weeks bad weather in winter" one would simply have to adjust power demand by removing non-critical loads. Fortunately for me those long stretches of bad weather are more likely to occur in summer than winter. On the worst day of the year - a terribly cloudy day on the winter solstice a 7kw array would still yield me about 6kwh for the day - which is enough for all my critical loads. 2 consecutive days like that would be incredibly unlikely.

Photowhit · May 2015

I think Bill is more on the "something always happens" side of things.

In truth, Living off grid, becomes, doing what has to be done. I've been living with my 4Kw system for almost 2+ years now, I understood my battery bank might be slightly undersized. For 2 years I have lived with what hot water I can generate between the solar and the wood stove in winter. I'm fine with that for the most part. I've had an additional 2500+ watts of panel waiting to be installed, and it will mainly be for daytime loads like heating water, I'll throttle back my 3 charge controllers (24v system, because I had the battery already) so I don't run too much current at one time into the battery. So I thought I had plenty on my plate, but someone was selling 4 - 250 watt panels that happened to match my 2 - 2kw arrays perfectly, for 55 cents a watt, so I'll max out my current 2 CC, likely before adding the additional array. Of course the added project also made it 'worthwhile' to pickup 3 sets of scaffolding for the 2 projects as well as a few other projects.... It doesn't seem to have an end, largely have more energy than I can use now, better. system tools, setting up a relay for the water heater is needed and cheap...

Dave Angelini · May 2015

If you are smart enough to anticipate and talented enough to wing it for some time keeping a large system running is not hard to do. These days I can drop ship to most places in the world in 48 hours and even a sailboat out in the south pacific can get spare parts for the spare parts pretty quickly.
I do remember the guy Bill and I helped who had wired a 48V XW to (2) strings of 48V batteries, IN SERIES. Definitely famous last words!

What's the longest you've gone without a sunny day?

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