switching between mains and off grid supply

[donkey07]

Thanks for the heads up on the hair dyer. I'm using a blow heater but might look into other alternatives which might be more practical and/or safe.

[J.P.M.]

I live a few hours east of Cobar and we do get a number of cloudy days (When not in drought). On cloudy days we generally run the house as normal unless we have 3-4 in a row forecast in which case we adjust the usage accordingly as it takes the PV system considerably longer to charge the battery. I might add we hang our clothes outside meaning we don't use a dryer, we use propane to boost the hotwater system, we have an electric oven but propane cooktop, No d which lightens the load on the system.

The only time thus far when i needed to use a different power source (the generator) to charge the battery was after 3 days of snow and heavy cloud (fairly rare here) and the snow had covered the PV panels affecting generation. I might note that this weather also created an interesting issue with the lithium ion battery as the core dropped to below -6 degrees Celsius which meant the battery management system shut it down to 50% of its capacity to protect it, which caused a few headaches until we worked out we just needed to warm the battery up with a blow heater on low (positioned at a safe distance) to get it back up to full capacity.

I know i gave more info than you asked but i am enjoying the conversation and the difference between countries. It's really fascinating. Thanks

G'Day.

You've most welcome. It looks to me that your climate might be similar to that of the American desert Southwest in the higher elevations such as New Mexico. About 300+ mostly clear days with lots of sun and with warm to hot summers and moderate winters with some snow in the higher elevations but still lots of sun. I lived in Albuquerque for several years. One of the best solar climates on the planet. Passive solar architecture has a home in such places.

Many around here may not be aware of it, but Australia has been a hot bed of alternate energy and particularly solar energy advances for a long time, particularly since the days of the founding of the International Solar Energy Society by providing some gov. funding through CSIRO and thus helping to stave off staving off bankruptcy for the fledgling society. But even before that at CSIRO, a guy by the name of Roger Morse and a few others pretty much single handedly kick started the solar energy industry in Australia. Morse wrote the solar water heater installation manual that served as the bible for many years and also got two major solar thermal firms off the ground. One of them - Solahart - had a large hand in bringing back and updating the idea of thermosiphon systems. Their systems are still around as are they.

Over the years, Australia's contributions to the body of solar energy knowledge and advances has been way out of proportion in both quantity and quality to the country's population, but that tends to happen in places with lots of sun and also fewer fossil fuel resources or less fossil fuel resource development.

As for too much information, among other purposes, this is supposed to be a place to exchange information and ideas. Besides, I figure if I don't like/need some information, no one has a gun at my head forcing me to read it.

On warming that battery, try not to use an electric hairdryer. (I'm a retired engineer so I know this stuff).

Good Luck

[donkey07]

Unless I'm screwing something up, it looks like donkey7 may live in a place that doesn't get many clouds. If he's near a place called Cobar, an 8.5 kW system will produce ~ 19kWh/day for all but 30 or so days/yr. and > ~ 14 kWh/day for all but maybe 15 of those 30 days. 3 day min. ave. totals are about the same. Looks like a place with a high clearness index (~ 0.63 or so) and not a lot of seasonal variability.

I live a few hours east of Cobar and we do get a number of cloudy days (When not in drought). On cloudy days we generally run the house as normal unless we have 3-4 in a row forecast in which case we adjust the usage accordingly as it takes the PV system considerably longer to charge the battery. I might add we hang our clothes outside meaning we don't use a dryer, we use propane to boost the hotwater system, we have an electric oven but propane cooktop, No d which lightens the load on the system.

The only time thus far when i needed to use a different power source (the generator) to charge the battery was after 3 days of snow and heavy cloud (fairly rare here) and the snow had covered the PV panels affecting generation. I might note that this weather also created an interesting issue with the lithium ion battery as the core dropped to below -6 degrees Celsius which meant the battery management system shut it down to 50% of its capacity to protect it, which caused a few headaches until we worked out we just needed to warm the battery up with a blow heater on low (positioned at a safe distance) to get it back up to full capacity.

I know i gave more info than you asked but i am enjoying the conversation and the difference between countries. It's really fascinating. Thanks

[SunEagle]

As donkey07 explained, each particular situation is different. I have a friend in the US who also had a tough choice: go off-grid or pay a fortune to run power to his house. He elected to go off grid and found that 3 forklift batteries were an economical solution to nighttime power. They aren't sexy and won't last forever. But in his case, they worked out.

"...Is this a British thing you got brained washed with in school?" <= Sorry, but to me, that is rude and insulting. It's fine to disagree with the approach, but to blame your nationality or a stereotype of that nation is misplaced.

That post from Sunking is almost 6 years old so I wouldn't expect an answer. He was a little anti PC, so most people offended by his comments were told to let it go and just try to learn something from him. There were just too many thin skinned people that showed up thinking they were solar experts only to be exposed as nuisance posters. He may not have expressed himself nicely but he was usually trying to keep someone from wasting their money before they learned about solar technology.

[bob-n]

As donkey07 explained, each particular situation is different. I have a friend in the US who also had a tough choice: go off-grid or pay a fortune to run power to his house. He elected to go off grid and found that 3 forklift batteries were an economical solution to nighttime power. They aren't sexy and won't last forever. But in his case, they worked out.

"...Is this a British thing you got brained washed with in school?" <= Sorry, but to me, that is rude and insulting. It's fine to disagree with the approach, but to blame your nationality or a stereotype of that nation is misplaced.

[J.P.M.]

Ok. I understand. I guess my question is what do you do on the days you don't get any sunshine for the pv system? Do you decide not to run any loads or do you use some other power source?

Unfortunately even here is sunny Florida we get a number of days each year when the sunshine is non existent due to bad weather.

Unless I'm screwing something up, it looks like donkey7 may live in a place that doesn't get many clouds. If he's near a place called Cobar, an 8.5 kW system will produce ~ 19kWh/day for all but 30 or so days/yr. and > ~ 14 kWh/day for all but maybe 15 of those 30 days. 3 day min. ave. totals are about the same. Looks like a place with a high clearness index (~ 0.63 or so) and not a lot of seasonal variability.

[SunEagle]

Sorry, I should clarify that we use more than 13.9kwh per day (more like 18-20kwh over a 24 hour period. The 50% referred to overnight usage when the PV panels are not generating power. During the day the house runs off the PV panels and not the battery. The battery only kicks in when the load from the house is greater than what is being produced form the panels, Sorry for the confusion.

Ok. I understand. I guess my question is what do you do on the days you don't get any sunshine for the pv system? Do you decide not to run any loads or do you use some other power source?

Unfortunately even here is sunny Florida we get a number of days each year when the sunshine is non existent due to bad weather.

[J.P.M.]

Hi J.P.M,

Sorry for the confusion, I'm in The central western Ranges of NSW, Australia so A$ is the currency.

As for cost of running electricity it was a typo the cost quoted was $140 thousand dollars. Our grid electricity prices have risen sharply in the last 10 years so we on ave, are paying between 35-40cents per kwh plus a 85-95 cent daily supply charge. With 11,000kwh/yr its about $4700 inc, supply charge, so $366/month which all adds up. You can get discounts from suppliers which make a difference if you shop around but you usually need to bundle gas as well.
Hope that clears up a few things, Thanks for you reply

Thank you for the reply and information.

If I was off grid because of high per kWh charges or high costs of getting grid power to a site, I'd only be using electricity for tasks such as lighting or communication or that that could not be done any other way by using nat. gas, propane or solar thermal. I still use a solar clothes dryer. Works great.

[donkey07]

Hi J.P.M,

Sorry for the confusion, I'm in The central western Ranges of NSW, Australia so A$ is the currency.

As for cost of running electricity it was a typo the cost quoted was $140 thousand dollars. Our grid electricity prices have risen sharply in the last 10 years so we on ave, are paying between 35-40cents per kwh plus a 85-95 cent daily supply charge. With 11,000kwh/yr its about $4700 inc, supply charge, so $366/month which all adds up. You can get discounts from suppliers which make a difference if you shop around but you usually need to bundle gas as well.
Hope that clears up a few things, Thanks for you reply

[J.P.M.]

System is 8.5kw tier 1 PV (32 panels) array with 2 sunnyboy inverters connecting to the house and the sunnyisland battery inverter with a 13.9 kwh BYD lithium ion battery as storage, The orientation is Solar North (southern hemisphere) with a 30 degree pitch/tilt. I have a 6kva generator as back up which i have used once.
I never said anything regarding new being necessarily nice! I said you need to make sure your not fluffing around with crap as there are plenty of sharks out there willing to take your money and provide dodgy equipment i.e tier 3 PV panels being sold as tier 1... New can be crap, and second hand can be very good you need just need to be careful. I don't intend on running anything I do run the system and have done for the past 18months with little or no issue. I use approximately 50% of my battery overnight if I'm running the dishwasher and have run the oven, if I don't run these things I use 30-40%.
As for reality and validation.......i'm not sure what you mean as i don't need validation and i live in the reality of a system which works.

OK. Understood.

The reality/validation question was in response to your: "... I'm new to this site so be nice". Sometimes folks show up here and want to do little more than brag about some insipid stuff they've done, looking to get praise, and then get all pissed off when their folly is called out. To my experience only, the "please be gentle" stuff often come from such folks.

You're obviously a better informed person.

Was the cost to run power $14,000 or $140,000 ? That is, what was the "$140,00" as you wrote a typo ?

FWIW and not my concern, but if it's $14,000, depending on grid reliability, I'd probably spring for it. $140K changes the calculus.

Also, is the currency US$, or A$ or NZ$ or some other kind of dollar ?

Many/Most posters around here are, for better or worse, from the U.S. Telling us all where you are located up front helps us understand your situation or at least flags us ignorant U.S. posters that some of our assumptions about your conditions, including electricity prices and grid reliability may not be valid. For example, a $6,000 annual electric bill gets a bit more understandable if you're on some Micronesian island (that uses U.S. $) and power costs a buck/kWh and the cost of everything, including running power lines is through the roof because of relative isolation.

My question about annual usage was meant to go with my location question and what would have been a follow on question about grid electricity prices/kWh, and then a price/usage question that might provide some insight as to why the average annual (residential ?) power cost where you are runs ~ $6,000/yr, in whatever currency you're using.

One other thing: Not everyone in the U.S. has $100/month bills. While the ave. U.S. usage (11,000 kWh/yr.) and ave. U.S. price (.1331/kWh) works out to $122/month, I If I used the ~11,000 kWh/yr. as is about the ave. residential usage in the U.S, I'd be paying ~ $3.6K/yr, not $1.5K/yr.

But you are singing my tune when you write that users need to do their homework. Just too bad that most of them are ignorant of what's required to make informed decisions and apparently, at least how I see it, choose to remain so.

Welcome to the forum of few(er) illusions.

[donkey07]

Well I am glad you can get enough power from your system. Unfortunately most USA consumers use much more than 13.9kWh each day let alone only 50% of that each night.

I believe you have justified that living off grid system requires a very conservative power usage plan. I am glad you are ok with that.

Sorry, I should clarify that we use more than 13.9kwh per day (more like 18-20kwh over a 24 hour period. The 50% referred to overnight usage when the PV panels are not generating power. During the day the house runs off the PV panels and not the battery. The battery only kicks in when the load from the house is greater than what is being produced form the panels, Sorry for the confusion.

[SunEagle]

System is 8.5kw tier 1 PV (32 panels) array with 2 sunnyboy inverters connecting to the house and the sunnyisland battery inverter with a 13.9 kwh BYD lithium ion battery as storage, The orientation is Solar North (southern hemisphere) with a 30 degree pitch/tilt. I have a 6kva generator as back up which i have used once.
I never said anything regarding new being necessarily nice! I said you need to make sure your not fluffing around with crap as there are plenty of sharks out there willing to take your money and provide dodgy equipment i.e tier 3 PV panels being sold as tier 1... New can be crap, and second hand can be very good you need just need to be careful. I don't intend on running anything I do run the system and have done for the past 18months with little or no issue. I use approximately 50% of my battery overnight if I'm running the dishwasher and have run the oven, if I don't run these things I use 30-40%.
As for reality and validation.......i'm not sure what you mean as i don't need validation and i live in the reality of a system which works.

Well I am glad you can get enough power from your system. Unfortunately most USA consumers use much more than 13.9kWh each day let alone only 50% of that each night.

I believe you have justified that living off grid system requires a very conservative power usage plan. I am glad you are ok with that.

[donkey07]

System is 8.5kw tier 1 PV (32 panels) array with 2 sunnyboy inverters connecting to the house and the sunnyisland battery inverter with a 13.9 kwh BYD lithium ion battery as storage, The orientation is Solar North (southern hemisphere) with a 30 degree pitch/tilt. I have a 6kva generator as back up which i have used once.
I never said anything regarding new being necessarily nice! I said you need to make sure your not fluffing around with crap as there are plenty of sharks out there willing to take your money and provide dodgy equipment i.e tier 3 PV panels being sold as tier 1... New can be crap, and second hand can be very good you need just need to be careful. I don't intend on running anything I do run the system and have done for the past 18months with little or no issue. I use approximately 50% of my battery overnight if I'm running the dishwasher and have run the oven, if I don't run these things I use 30-40%.
As for reality and validation.......i'm not sure what you mean as i don't need validation and i live in the reality of a system which works.

[J.P.M.]

We decided to go off grid with no grid connection because it was economical. The local power company wanted $140,00 just to get power 250m down the road! Our system cost $29,000 which runs a 4 brm house with no trade offs regarding energy use, so the decision was no brainer. I understand the fact using battery will often cost more that using grid power but I also think i depends on where you live. The average cost of power here runs at $1200-$1800 per quarter well over the $100/month you guys are lucky to have. In the end though you need to do your homework based on your local area as in some cases it is actually cheaper to move to battery over the long term as long as what you get is quality and your not fluffing around with crap products which don't work as promised.
Just my thoughts, I'm new to this site so be nice

Where is the site ? if in U.S : zip ?
How much electricity (in kWh) do you use, or plan to use, over 12 months ?
How big is your system, what is its orientation - tilt and azimuth ?
How big and what type of storage do you intend to employ ?
What type of backup generation are you planning on ?
What does new have to do with nice ? You want reality or validation ?

[Ampster]

That sounds like a reasonable economic trade off. Tell us more about your system. Panels, Inverter and batteries?