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Starting a new system from scratch


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Gents,

I would really like some suggestions before forking out a lot of money. 

My thoughts are for:

24 off 265w panel array mounted on a car port (to be constructed to suit - space no concern).

A 6kW 48v inverter. Is a combination inverter charger preferred? Must be hybrid to balance loads in the background.

4 off 200ah batteries to supply 48v

I need recommendations for:

Are there ideas or designs available to tilt the panels to suit the season. I read about different angles for winter, summer etc. No big trees around.

What makes do you recommend.

Is there a way of making a house distribution board more intelligent to control or manage different loads at  different times as solar energy is generated? By interlocking circuit breakers to switch on or off sequentially. 

Which companies are recommended - I am not looking at one man shows here. People die and retire.

I am looking for at least a 10 year backup service as I am getting older - already retired :-)

my non technical wife must be able to manage it when I am not around.

My house is in Witbank.

 

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Morning  @Johandup how long is a piece of string :) :P. Just joking but as you stated a lot of money is involved.

The principle that most of us adhere to should give a some guidance as to what you should look at. 

  • You need to decide do you want to go Off grid or Grid tie as this will determine the rest of your design (Remember Going Solar is a way of life) 
  • I prefer grid tie as this will give you the most "stable" system in terms of the SWAMBO  ( No need to check if she decided to switch every thing n at once ) 
  • Then out of a financial viewpoint I would say look at what your base load is during daylight hours and how much of your night consumption you can move to day (Remember the Lifestyle in point 1 :) ) . You could find that up to 80% of your consumption will fall below the 1 kw range and then the rest could be up to 6 kw - so it would be silly to increase your design by 35% ( 2 kw - 6 kw) for just 20% saving. ( Example boiling a kettle for 2 min @ 2500w will cost you a few cents from eskom but running a PC at 500w 24/7 will cost you a lot more)
  • You also have the advantage that , if you go grid tie , you do not need to rely on batteries which is quite a pain ( IMO - some might differ) 

Also keep in mind that the more you spend on a inverter the less you need to fiddle on it , here Victron , SMA works very well and it is , sort off , plug and play. Once it is running , it works well.
The Axpert inverters is quite a lot cheaper but you will need to fiddle with it and the family would most likely need to get trained to live with the system. ( I have a Axpert and if I had the cash , for the sake of the SWAMBO , I would go victron in a heartbeat) 

This should give you a general idea , there is a couple of manne here that will chip in with quite a bit more technical info. @plonkster @Chris Hobson ..... Chris is also the the instalation market so he might also be able to assist.

 

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Paul pretty much covered it.

Upfront disclaimer: I'm employed by an inverter maker.

First decide if you want to save money, want (some?) backup power, or if you want to be completely independent. If you just want to save money, install a grid-tied inverter. By far the cheapest, and it needs no batteries. My personal choice is either Fronius or SMA. I normally recommend Fronius because they integrate well with a Victron Multiplus/Quattro, if you decide to add one later (perhaps to backup a few loads).

If you decide that you want backup (perhaps not everything, maybe just essential loads), then your choice is between the Voltronic Infinisolar, the Goodwe, and the Victron Multiplus/Quattro. I want you to buy the last one of course. It is the better inverter. For sanity reasons no debate will be entered into :-)

The Axpert inverter can sort-of do hybrid work, in that it can switch to the grid if the load is too high, but you need a bigish battery bank for it to work well. I think the manufacturer recommends at least 200Ah. I think if people actually factored in the cost of the battery bank, the other options start to look a lot more appealing.

We're at the point now where for 50k you can buy either a large lead-acid bank, or a small lithium ion battery. Depending on your application, the answer is no longer obvious :-)

 

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Thanks to the people who took the time to reply. Much appreciated.

I thought this morning what the real cost per kWhr is for solar installations.

All items have a life time and looking at posts from every where this is evident.

So the term “free solar energy” is actually misleading as it costs money to convert it into electricity.

Has anyone tried to do this?

How long does what last before there is a need for replacement?

What is the cost per kWhr for a set of batteries? Especially with their ongoing decrease in efficiencies. Just look at how lithium batteries are guaranteed.

Has anybody got an inverter that last longer than five years with everyday use?

If a R30 000 inverter generates 500kWh per month and lasts 5 years the cost would be R1 per kWh - example only off course.

Then there is the small but expensive replacements for damages as well - lightning that has damaged my borehole just now added a new meaning to the term “free water”.

It all adds up in my book.

I see the convenience factor but not the economy factor in all of this.

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2 hours ago, Johandup said:

Thanks to the people who took the time to reply. Much appreciated.

I thought this morning what the real cost per kWhr is for solar installations.

All items have a life time and looking at posts from every where this is evident.

So the term “free solar energy” is actually misleading as it costs money to convert it into electricity.

Has anyone tried to do this?

How long does what last before there is a need for replacement?

What is the cost per kWhr for a set of batteries? Especially with their ongoing decrease in efficiencies. Just look at how lithium batteries are guaranteed.

Has anybody got an inverter that last longer than five years with everyday use?

If a R30 000 inverter generates 500kWh per month and lasts 5 years the cost would be R1 per kWh - example only off course.

Then there is the small but expensive replacements for damages as well - lightning that has damaged my borehole just now added a new meaning to the term “free water”.

It all adds up in my book.

I see the convenience factor but not the economy factor in all of this.

Hi,

I once did a calculation of expenses vs Eskom. If you take a modest 6% increase in Eskom tarrifs and a modest 6% increase year on year for equipment, then assume that your equipment will last 20 years (with proper care), and we assume that your monthly Eskom bill is R700, you're expenses on solar equipment bought should not exceed R160k or something like that. And thats R160k cash, not financed.

 

That should save you enough money to get you ahead of the curve and pay for the next replacement in 20 years time, theoretically.

 

-G-

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3 hours ago, Johandup said:

What is the cost per kWhr for a set of batteries?

That one is fairly easy to calculate. Take for example the LiFePO4 bank sold my someone like FreedomWon. Just sucking numbers from appendages (look at the spec sheet if you want the real numbers), they normally go for around 10k for each kwh installed, and you can cycle them down to 70% DoD and still get some 3500 cycles out of them, or so they claim. So on each cycle you get 0.7kwh, times 3500, that's 2450kwh over its lifetime. 10k/2450 ~= R4.10. They say 7000 cycles if you limit discharge to 50%, that gets you closer to R2.85 per kwh. But they define end of battery life as that point where it has irreversibly lost 20% of its capacity (eg your cell phone starts to die at 8PM instead of bedtime), so technically the price is perhaps even a bit below that. This is however only storage cost. As you pointed out, the other equipment also has a lifetime and an associated cost. The PV panels are actually the least of it, if you bought the right ones!

3 hours ago, Johandup said:

Has anybody got an inverter that last longer than five years with everyday use?

Mine was 4 years old this July. Daily use, hasn't been off for more than a few hours when doing maintenance.

With some inverters you can extend the warranty. With Fronius I believe you can extend it all the way to 15 years.

3 hours ago, Johandup said:

If a R30 000 inverter generates 500kWh per month and lasts 5 years the cost would be R1 per kWh - example only off course.

That's only the inverter cost. And it would depend on how hard it works, most inverters tend to idle away at night because of battery cost. For 30k you can get a 3KVA Multi and an MPPT, so we can actually work it out for this inverter. It has a 5 year warranty, so we can assume it will last at least that long (or you get a new one). If it runs continuously at 3kva, let's sal 2kw to add in some power factor, then in 5 years it will make 87MWh. That's 34 cents per kwh. But the way most people will be running it, it needs to last 15 years to get anywhere near that price :-)

3 hours ago, Johandup said:

I see the convenience factor but not the economy factor in all of this.

The value has to be measured some other way. When I installed my system in 2013, the main motivation was that I lost too much money (as a computer programmer) during load shedding. The initial system paid for itself in a matter of weeks. There is also the wife factor: I love the fact that she loves the luxury, simple things like a power failure at night, and the wife is happy because the outside lights are still running...

You don't have to spend a lot of money to run a few lights... :-)

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10 hours ago, gallderhen said:

... for the next replacement in 20 years time, theoretically.

Jip, batteries (never) and inverter (seldom if ever) lasts 20 years.

Only the panels may last +-20 years.

The minute you bring in replacement costs, the numbers for solar becomes unattractive fast in cities.

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This morning contemplating my retired life with my newly acquired boswa (fetched it yesterday :-) I was looking at the pvoutput website checking some local stats.

What jumped out is some very big solar panels systems with an approximate average daily output of 3.25kwh per installed kw on the highveld.

So this must become the basis of calculations to satisfy daily kWh requirements.

A 24 panel 6kw setup would only give 25,5kwh when the sun is shining. 

So the arguments for measuring hourly power requirements become very valid.

A point to ponder is the short time the majority of working parents with kids at school actually spend at home six days per week.

Such families will benefit very little from solar systems unless it has a big battery backup.

Financial calculations in such cases would make little sense. My opinion only.

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For some people, the cost per kWh is perhaps irrelevant. Not because of availability of it, but rather the reason for going "green".

It could be various reason, like medical - need machines to keep someone alive, and can't trust our grid

or convenience - can't bear to miss favorite soapy/hot shower/aircon....etc

Whatever the reason - to each their own.

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1 hour ago, Johandup said:

What jumped out is some very big solar panels systems with an approximate average daily output of 3.25kwh per installed kw on the highveld.

Aaah!  Johan what you have noticed is music to my ears. Solar installers work on 5 hours of good solar sun per day and yet in practice we do not nearly achieve that.

 

1 hour ago, Johandup said:

A 24 panel 6kw setup would only give 25,5kwh when the sun is shining. 

If you have a 25,5 kWh load shaped to your solar production. One of the disadvantages of lead acid is you have this long float necessary for the health of your batteries - not helping you daily production. @plonkster has recently purchased a lithium bank and is benefiting from the ability to operate it with the taps open so to speak. The is no need for a long taper charge (float).

 

1 hour ago, Johandup said:

A point to ponder is the short time the majority of working parents with kids at school actually spend at home six days per week.

Such families will benefit very little from solar systems unless it has a big battery backup.

Financial calculations in such cases would make little sense. My opinion only.

 This is the reason why some European solar engineers are advocating East West facing panels. In the Northern hemisphere South facing panels give you the maximum solar production but the utility companies are paying so little for solar energy that it makes sense to generate power when there is at least someone at home.

If you plan to go off-grid then reduce you consumption by acquiring energy efficient appliances and light but also factor in 20-25% extra for growth. You don't want to be a solar Nazi for the rest of your life. "We can't have XYZ because we are on solar" does not cut it with the rest of the family. Obviously the heavy draw items are an issue but as the kids grow up they want fishtank/ game console etc - things that consume electricity.

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2 hours ago, Johandup said:

What jumped out is some very big solar panels systems with an approximate average daily output of 3.25kwh per installed kw on the highveld.

One of the reasons for that is the popularity of the cheaper Taiwanese inverters. An off-grid inverter used to do self-consumption will always do less than a proper grid-tied or hybrid inverter. These systems are often also sized towards the peak power requirements, which skews the calculation a little. In fact, I'd go as far as saying that sometimes the kwh/kwp efficiency number doesn't even matter. The price of the PV modules have dropped so significantly that even oversizing an array to 150% or 200% is sometimes a no-brainer. If you oversize the array, then of course the efficiency will suffer (and it doesn't matter, because it is not the point).

2 hours ago, Johandup said:

A point to ponder is the short time the majority of working parents with kids at school actually spend at home six days per week.

Correct. By far the most efficient way to use solar power is directly, as it is generated, so that you don't need storage. If you are at home during the day, you move your loads to day-time. For the past 7 years, I spent 5 working from home, and my wife works just down the road. That works really well for us, we let the washing machine, dish washer and tumble dryer run during the day. Some people run their geysers during the day too, just to use that power. Pool pumps are another popular load for this purpose.

But this is actually precisely the use-case for inverters such as the Tesla powerwall or Victron's ESS setup (hybrid inverters, they grid tie using battery power at night). The idea is that whatever you don't use during the day, you put that into a battery and use it tonight. This only makes sense if the batteries are cheap enough.

1 hour ago, Chris Hobson said:

purchased a lithium bank and is benefiting from the ability to operate it with the taps open

I got lucky with that, a mutually beneficial arrangement helped me to get that bank a little cheaper than usual. I fully understand why people don't do it... BUT (man I use that word a lot today), looking at the options available locally now (FreedomWon, BlueNova, Mypower24, pylontech), the prices has come down significantly. A decent lead acid bank starts at 20k, more like 30k-50k, and you can get a very decent LiFePO4 bank for 50k now. Which is why I said earlier that the answer is no longer obvious.

Let me just justify the prices, bolster it with some arithmetic :-P If you bought the best bang-for-buck lead acid today, you'd be buying 8 Trojan T105 RE batteries at roughly R2.5k each. That's 20k, and it will give you 48*225 ~= 10kwh storage, of which you only want to use half if you want the battery to last its rated 1600 cycles, so it is effectively a 5kwh battery that will last 5 years, and it will be totally shot at that point. On the other end of the scale, LFP batteries cost around 10k per kwh and last 3500 cycles or more, and have 80% of their original capacity left after that (9 or ten years). In other words, I'm saying they cost about the same.

Speaking of BN though, this starts bothering me more and more now. They claim 7000 cycles to 70% DoD (which sounds too good to be true), but they also spec their batteries by C10 rates (which is odd, for LFP batteries). Just watch out for that when doing price comparisons. At 7000 cycles to 70%, the price per kwh storage is around R2.05, which beats grid prices in many places (high end in Cape Town for example)... but the entire thing depends on that battery actually doing 7000 cycles... and I have to say I'm beginning to doubt it.

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It’s a real pity that we cannot use Eishkom and their distributors as battery banks at night time. The buyback tariff, where it is applicable, is minute and not worth the hassles. All over the world btw.

The light in the tunnel is the development of super capacitors and next generation lithium batteries aka Elon Musk.

Elon is planning to put up two additional battery factories. The current one is going to replace half of the world’s current output (rumour) - bad if you are Chinese.

But it will push prices down to where the current old generation batteries will disappear like the old tv’s.

The super capacitors will happen for the next generation people. On YouTube there are many videos to illustrate this. Just be patient.

What all of this implies is that any system you buy today must be futured proof.

Chargers must be able to do lithium charging as well - don’t tie yourself to old technology.

If you go to all the trouble for solar panel rooftop installation put up the frames for more panels when you need it or can afford it. Less hassles at the time.

When doing calculations do combine the costs for all the different elements.

Battery costs must be combined with the generation costs as an example.

Buy decent Trojan batteries now instead of more expensive types because the replacement one in five years time will be more advanced and less expensive.

That is about guaranteed.

The implementation of huge solar plants will be more common in future and will drive the prices of electricity down. Not like Eskom where the output stayed even over the years but their manpower doubled. In the news yesterday they wasted R80 BILLION last year. What’s that between comrades....

That is not sustainable and we should benefit “some time” in the future.

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1 hour ago, Johandup said:

next generation lithium batteries aka Elon Musk

No new tech really. It's NMC batteries as far as I know. Mass production might bring down the cost though, that is what we hope. In addition, these cars now do significantly more than 200km on a charge, and rumour has it that some early models are showing 3000 cycles on their batteries already. That means many batteries will outlast the cars they are fitted to, which means a healthy second-hand battery market.

Also, they aren't the only people getting in on this. Bosch acquired Seeo a while ago. That's for NCA batteries, slightly lower energy density but still better than LFP, good enough for cars that is. Again, not really new tech, but hopefully cheaper as demand goes up.

1 hour ago, Johandup said:

super capacitors

Trouble with those is linear discharge behaviour, the voltage is proportional to the state of charge, and as soon as the voltage drops below the point where you can do reasonable work you cannot discharge any further. Also higher self-discharge I'm told. I think there will be a place for them, but I'm not sure they will replace battery banks soon.

2 hours ago, Johandup said:

Buy decent Trojan batteries now instead of more expensive types because the replacement one in five years time will be more advanced and less expensive.

We've been predicting that for at least 5 years now :-)

I've given up waiting on the new advanced tech that is supposedly coming. The tech that is coming is here already. It's Lithium Ion. It will just get cheaper.

If I am wrong, then at least we'll all be pleasantly surprised :-)

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I am a little more enthusiastic about supercapacitors. If used in conjunction with for instance LP type Ni-Cad or Ni-Fe, you could have the best of both worlds, so to speak. Long life and very deep cycling characteristics of the LP types (with no or very little harm). Now you can run a "soft" load for very long periods AND have the punch when needed to start and run heavy loads, especially in daytime. 

Just my thought......

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On 10/11/2017 at 6:31 AM, Johandup said:

I thought this morning what the real cost per kWhr is for solar installations.

Its been a while but I tried to do a comparison between Eskom and solar , there is  few things that I would add now but it should give you a general idea. 

 

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Eskom is currently seeking a 20% increase though, and chances are Nersa is going to give them more than half of that. Also, I'm told that in the cities the amount can be as high as 27%, again, it will likely be tempered somewhat by Nersa, but the increase will be above 15% at least. I know OUTA and others are fighting this, but in my experience, we have to expect that it's just a matter of time before that load of bricks hits us.

Now a 20% increase on the current Cape Town base of R1.93 brings you to around R2.30. What's more, the current R2.34 for consumption above 600kwh will go to R2.80. Take into account also that in many European countries cost is around 20 cents (R3) per kwh, in Germany it's 29 cents, in other words, I see no reason why it won't continue to grow faster than inflation for the next decade to catch up with European rates eventually.

All we need is for the cost of  batteries to come down by 30% to 40%. I think...

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Now, if only I can get my swambo to agree to a gas stove.

We have a Paloma gas geyser where you can set your bath’s temperature and liters.

What a joy to use.

I bought a packet of 12 Panasonic Eneloop AA batteries with a guaranteed 2100 recharge cycles. It cost the same as Duracell but with far better performance. 

So yes, the world is improving. 

And, sad to say, the current regime will keep on milking the paying consumer for all they can.

The issue with solar is to store the extra energy you generate.

Batteries is but one of the methods. 

If some bright spark can invent another method we’ll go for it.

I see my meter is reporting a power factor reading of 56%. It indicates seriously bad engineering in my town.

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5 hours ago, Sidewinder said:

My SWAMBO loves the full gas stove I put in two years ago. Doesn't want to go back to electric. The new generation gas stoves do bake and roast etc as good as any thermofan.

Can you share the make model and the cost price...  I'm also looking for one?  Thanks

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9 hours ago, Johandup said:

Now, if only I can get my swambo to agree to a gas stove.

Gas is generally much nicer to cook on. It's actually not cheaper. Per unit of energy it costs about the same, and the gas flame is less efficient at heat transfer. But it's nicer to cook on, you can cook even when the power is off, and if you're attempting to go completely off-grid it is much cheaper than inverter/panels/batteries for the same.

9 hours ago, Johandup said:

I see my meter is reporting a power factor reading of 56%. It indicates seriously bad engineering in my town.

What kind of meter is that? Power factor depends on the loads on your side, not what the grid might be doing. With a zero load the power factor is also zero (cause it's the V vector times the I vector times cos(theta), but the magnitude of I is zero so the dot product is also zero). IE, power factor depends on the load.

I have LED downlights with a power factor of 0.2. Induction motors are generally around 0.7. Remember that when sizing an inverter, you have to size by apparent power.

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9 hours ago, Mark said:

Can you share the make model and the cost price...  I'm also looking for one?  Thanks

We got a ELBA Gas Stove and was a bit expensive (R 20 k)  at the time but the wife loves to bake.. (She did a wedding cake a few weeks ago and I havent heard her complain once about hot spots or anything , a couple of times about me but not the stove ---- go figure ---).  We use about 48 kg a year and last time we filled a bottle and I got screwed at the local shoppie we paid R 1200 for the bottle so thats R 100 per month for gas. 

I am pretty sure the cheaper one will work just as well. There are a few other brands like Defy ectr. but they all felt thin in comparison. I would "poke" the tops and check how much deflection I got the less you get the thicker material was used and that should relate to the workmanship.  You could go SMEG - maar bogger daais groot geld ....

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3 hours ago, PaulF007 said:

SMEG

Honestly don't quite know why people do it. Must be an image thing. Those things are really overpriced for what you get (and this is coming from boy blue here). I feel the same way about Siemens fridge/freezers as well, double the cost of the Bosch, but is it really that much better? :-)

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1 hour ago, plonkster said:

Honestly don't quite know why people do it.

I suppose it is a point of view thing. Looking from the bottom up will always look different. The guy that earns 2.5k a month will look at Kellogg's or Pronutro and say why do people eat those things it is a waste of money , the oke with R 20k will say who pays R 80 for 500g Granola cereal and so on. Personally I agree that there needs to be a balance somewhere in all of this but to find it thats the life long question. 

But back to topic - Bosh freezers is good value for money when you are looking at solar I have two fridges and one freezer and between them they use a average of 100w (guessing) per hour. My total average consumption , when the house is in standby , is about 160w so it could be a little more. 

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