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Wanting to go Solar... omg so much info


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Hi,

I am obviously new and I was sent here by a forum member on MyBB. I am purchasing a house in Northern JHB near Northgate and I'm looking to go green as well as avoid escalating Eskom costs in the future.

The house has a Solar Geyser already and Water capture tanks, which is part of the purchase decision.

Before saying DIY kits... I'm overwhelmed with the info out there (even on this forum) and I'd rather have an install done by someone whose made all the decisions alongside me and get recommend, purchase and install the kit.

ATM I use about 20KW a day (with the current geyser tied into the grid and on all day), we have one of those Eskom electricity monitor things that shows monthly, weekly, daily usage. Ill upload the numbers here.

My rough thoughts are as follows:

Grid tied to Eskom, Can run the generator when both Eskom and batteries are dry/low and approximately 10 hours worth of Battery power for:

Fridge, TV & Audio centre, Internet components (Fibre CPE, Firewall, switch & Wifi) and perhaps 2 PC's.

We'll be going gas with the stove and I can't think of any other big requirements.

I've seen all kinds of DIY kits so I'm really confused as who to go to.

 

What I would like is an A-Z install, from inspection to purchasing, implementation and integration into the existing electricity supply with the electrical certificate and other compliances done.

Lastly, I would like some network connectivity so that I can centrally monitor the system through a raspberry Pi or similar (that's the part I will do and am good at :))

Thanks :)

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Welcome @DMNknight ... you have entered the realm of us confusing you, and then you will know what not to do. :D

Step one: You understand the difference in price on "Needs" vs "Wants"?

Step two: You understand that batteries are not cheaper than Eskom, as you are in the city. Your idea of a gennie is good for load shedding to save on large battery bank.

Step three: Can you reduce your consumption even more before you solarise? How low can you go in other words?

Step four: Then we can focus on what you need to take that onto solar.

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Welcome to the forum @DMNknight 

I think @The Terrible Triplett's step one should be budget. Lot of things that could be done different between a R50k and a R500k budget. If you've got the budget the "want vs needs" part can become debatable. I think there's a very fine line when one's got the budget to go big. Return on investment is a whole different ballgame though.

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Hey TTT,

Yes, much optimsation is to be done, like switching all the lights to LED, geyser is already solar and the stove will be Gas.

I understand the Needs vs Wants.

Needs:

Absolute must - Lights and cellphone charging and house security (beams). Internet and network equipment. Laptop. This is for short term outage/working from home.

Secondary needs TV & Media box which uses internet to stream and on occasion 2 PC's which are used for gaming.  This is for extended outage where you can only read a magazine so many times before you start quoting the articles verbatim.

Wants:

Run 100% on Solar during the day, including a tumble dryer (which has a secondary saving in terms of clothes not being bleached by the sun) and everything else... possibly a dual geyser setup with PV/Eskom "heat-up"

Microwave / Convection oven limited use (max 1hr in the evening)

Slow cooker and other kitchen utilities.

4 Already installed Aircons. Unlikely for them all to be on at once though.

Eskom only:

Only the Oven that I can think of.. for baking things.

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From what I understand I need to determine the KW's I need for the "Want's" table because the solar panels are much cheaper than the batteries.

Then determine "Needs" in PV KW to charge the batteries and then determine the KvA of the batteries I need. Apparently the battery type are important and need to be applicable to the use I am going to be putting them. (Gel, LeadAcid and Lith_Ion?)

Oh and I don't need 3 phase, as I will only have enough draw for which 1 phase is fine (even though there is efficiency in 3 phase)

That's as far as I got because then parallel 24v or single 48v and DC and AC and all those other buggers entered the fray and got me confused :)

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@DMNknight - you are on the right track.

Your Wants above, are std stuff to run off solar during the day. A given, a must. It will be done. The guys here have LOTS of clever ideas to maximize the usage,

Your "Needs" I presume are musts at night if there is a power failure. The computers / media center ... eish, it gets very expensive running anything at night off batteries, that is the costly exercise for all solar systems. So if there are power failures, ideal is not to use the heavy loads like gaming computers and media centers. Tablets and laptops till they need to recharge is a thought to share.

You would probably need batteries for the inverter, so if done right, loads like lights / cell / internet - small loads - to not use more that 20% of the batts ah capacity, that is fine. It depends on ah and make batts you decide on. Idea is to get some ROI from said batteries seeing as load shedding is a thing of the past. OR a even smaller battery bank, even better.

Ps. I suspect the 20kWh per day is largely made up of the computers and media center. :D

 

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You appear to be the std system: 5 4 3.

5kva 48v Axpert - as you are heading towards connecting the house? But, it becomes an issue if the batts must power the house.
400ah bank - the expensive part - guys are trying to get smaller banks as batts are the costly part.
3kw panels - it seems to be the general consensus for a home to use a 3kw array to its fullest extend, takes a bit of juggling. There are Experts here on that.

And then the flip side.
Me, and few others, have approach it differently. We want to get rid of the constant 500w or less that is always there. At night reduce that to 200w or less. So our systems are much smaller, like mine 930w panels, 1300va max inverter, yet I run up to 800w during the day and fridges and such at night and seldom go below 80% SOC on my 225ah 24v bank. 24v because we don't like to spend on batteries. :-) 

So, back to your system:
Daytime Load + batt recharge = the panels required to do it.
Batts needed = what you "NEED" to power at night if there are power failures OR during the day in bad weather and a power failure. 

 

 

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Hello @DMNknight

When it come to reducing you "baseload" you need to look at the things that runs 24/7 , 20kWh implies that your base is about 800w. 
In my experience computers (Desktops) are quite bad and then all the gadgets that you run all adds up. Remember 10 x 20 chargers that is plugged in all over the house will give you a base of 200w right there. A laptop can draw a load of 50 - 80 on its own and if you have a screen you are on 120 w , by now you should get the picture :) .

Fridge freezers are also something that that you need to look at , Bosh is very good if you look at there A+++ ratings.
Remember that LED's are the same as energy savers 10w is 10 w led's only last longer so replace as you go , unless you still have 50w globes :o.

The effergy meters measures VA so it will give you a good indication what your consumption looks like but as a rule they will measure higher that what you actually are doing. 

Then you need to contend with the SWAMBO and make sure that she is Solar compatible :) . 

If you plan to ga on batts at night I have bad news with regards to ANYthing that heats up as it will draw a lot of ah from the bats at once. On a 3kw system the biggest peak load that I would recommend is about 2000w as the panels rarely will produce 3000w all the time. Night time I would not go above 1500 w and then only for a short time.

Here is a Graph of my general consumption in a "normal" day you will note that the peak for that day was only 1600 w


2017-05-10_172107.thumb.png.fa005a679099dfca9db9baf7a4f292a5.png

Night use when all is sleeping

2017-05-10_172608.thumb.png.88a345657d2c1d96772979ab086078d2.png

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The main issue then, is to address the times of heaviest use which is the "Needs" part 2.

In the evening when the sun is not shining, we get home and fall into our usual routines of TV watching and gaming. That's about 8 hours worth at worst... which is where the cost of batteries vs Eskom comes in I guess?

Is there a way of switching over to Eskom at about 4 hours use (75%) and once the load drops below X amount of load (i.e. the pc's and tv's are off) then switch back to batteries until morning and the sun does it's magic?

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14 minutes ago, DMNknight said:

... which is where the cost of batteries vs Eskom comes in I guess?

Spot on. A kWh from a battery bank is a lot more expensive, and must be replaced every X years, than a kWh from Eskom, especially if you reduce the loads even more at night. Only time batteries make sense is if you are off-grid and only have a generator, then batts are way cheaper.

To mitigate a smaller battery bank during power failures, a small gennie becomes more sensible for us in the cities, used infrequently

 

Another point to ponder. You can also split / view loads like this:
1 - Loads that are purely night time like lights. You have to have batteries.
2 - Other small loads that are on 24/7, fridge, internet, alarm etc. over 24 hours some is solar, some is batteries.
3 - And then there are loads like Microwave and kettles etc. - the bigger the combined load, the bigger the inverter and the bank = more expensive.
4 - Pool pumps startup current.

1 and 2 are for smaller systems, making them a more cost effective hobby. Hobby because Eskom is cheaper.
3 necessitates bigger inverter, 5kva+, to be able to power the Microwave / kettle for the minutes they are on per day with the rest of the load. So I ask, how much does one save on these types of loads when you work out what the bigger inverter and bank costs. 
4 is a very good saving if a pool pump is powered daytime from purely panels, never ever from batteries on a 5kva inverter.

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There are a few options that you could consider , if you are using a Axpert inverter you can use the Axpert as a "ups" where by you disconnect eskom via a high amp relay and on the switch side you use the BMV and soc status to switch over to the grids when you reach x soc. There is also some software option where by you change the mode of the inverter and then you will switch over. 
Personally I use a bit of both so if the software bums out you still got the hard switch as a backup..

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7 minutes ago, DMNknight said:

... switching over to Eskom at ...

Done and dusted. Is the standard here. We and others supply software for that.

To make it happen, a Victron BMV 700/702 monitor is a must.

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TTT: I'd pretty much go to about 50% into option 3 where our househole Quality of Life items sit. Gaming and TV.

Then it's down to how much and who do I call :P I think I have a fairly healthy budget for this... but If I use google I get anything from 50k to 150k for a 5KvA system (In South Africa) and I don't know who to trust. A lot of them also seem to be DIY which is a little beyond me as I probably need a proper DB installed.

I'll do the IT stuff as I have some other systems I intend to integrate.

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7 minutes ago, DMNknight said:

I think I have a fairly healthy budget for this

If you do, I would also have suggest a look at Victron. @plonkster can go into details of how to best utilize what Victron has to offer, grid tied, little battery use and all that, using Victron's free software on a Pi.

Obviously a Axpert is like in beyond comprehension cheaper than a Victron setup, but us Victron supporters are quite satisfied with our rigs. Plug and Play and walk away kinda thing.

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2 hours ago, The Terrible Triplett said:

Welcome @DMNknight ... you have entered the realm of us confusing you, and then you will know what not to do. :D

Step one: You understand the difference in price on "Needs" vs "Wants"?

Step two: You understand that batteries are not cheaper than Eskom, as you are in the city. Your idea of a gennie is good for load shedding to save on large battery bank.

Step three: Can you reduce your consumption even more before you solarise? How low can you go in other words?

Step four: Then we can focus on what you need to take that onto solar.

"you have entered the realm of us confusing you, and then you will know what not to do"

Haha Laughed now.

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1 hour ago, The Terrible Triplett said:

@plonkster can go into details of how to best utilize what Victron has to offer, grid tied, little battery use and all that, using Victron's free software on a Pi.

Dude, you'll get me in trouble. Look, the blue kit is 250% of the price of the cheap Taiwanese inverter and a hard sell. I mean, I can give you a list of at least 5 right now why the blue inverter is better, but it remains a hard sell, and a lot is tied up in two rather unknown quantities, namely the expected life, and the support factor. I actually went back and did more research on the pricing on other brands, looking also at our local makes (MLT power, JSM, Microcare), I mean go to sustainable.co.za, we don't buy from them because they are overpriced, but if you assume a more or less consistent overpricedness over everything you get an idea of what's available in the >1.5kw bracket that costs less than an Axpert, there's basically a thing that looks like a Xantrex rip-off, an Omnipower or two, a Cotek and a Vision. Far as I know none of these bundle an MPPT, ie there is nothing as cheap as the Axpert, nothing with the kind of value vs cost. That thing is literally too good to be true.

I think that is what frustrates me so much about these comparisons. There isn't even a proper spectrum to choose from, it's like you either take the cheap one.... or you take the Victron because you might as well... :-)

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1 hour ago, PaulF007 said:

Just to add to some of the fun and games here you can see the impact of running the TV on the system 

We were away for the weekend and the system was on idle , tonight the kids got spoiled and watched tv from early :) 

 2017-05-10_192909.thumb.png.65e3e70975e6a810d79c1f862ee6beb3.png

It all adds up ;;

I wonder what those odd spikes are on the TV? Perhaps when the loud commercials kick in?

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I really want to do a proper THD and/or voltage regulation test (on the output side) at various loads on the various brands and come up with a proper comparison. I'd like to do the same wrt DC ripple coming out of the MPPTs and things like that. To do any of that I'll need to blow at least 7k on an oscilloscope that has a storage facility as well as fourier analysis. At present, I simply cannot justify it. But if I ever acquire such a neat piece of kit... I'll be coming to visit someone with an Axpert and we'll draw some pretty pictures.

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14 hours ago, PaulF007 said:

Just to add to some of the fun and games here you can see the impact of running the TV on the system 

We were away for the weekend and the system was on idle , tonight the kids got spoiled and watched tv from early :) 

 2017-05-10_192909.thumb.png.65e3e70975e6a810d79c1f862ee6beb3.png

It all adds up ;;

Little Women USA? :>

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18 hours ago, The Terrible Triplett said:

And then the flip side.
Me, and few others, have approach it differently. We want to get rid of the constant 500w or less that is always there. At night reduce that to 200w or less. So our systems are much smaller, like mine 930w panels, 1300va max inverter, yet I run up to 800w during the day and fridges and such at night and seldom go below 80% SOC on my 225ah 24v bank. 24v because we don't like to spend on batteries. :-) 

This appeals to me for some reason... perhaps my german blood shouting efficiency uber alles!

What are the ups and down of the former "std" system compared to the above?

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18 hours ago, The Terrible Triplett said:

24v because we don't like to spend on batteries. :-)

I recently discovered that many of the NCA-chemistry (Lithium Ion with Nickel-Cobalt-Aluminium in the cathode) batteries come in 24V modules. They are expensive little buggers, around 4400 Euro a piece, so if you only need to buy one it really helps :-)

I also have a small system. I now have 1.5Kwp on the roof (I should update the signature) but it is specifically arranged to point in different directions for a flatter curve, so I hardly ever see a peak of more than 1.2kwp. The inverter is only 1.6kva, 24V. But I run ESS, so basically everything under 1000W runs from PV/battery during the day, at around 5PM I set the limit to 250W (which is roughly a C20 discharge rate for me) and I let it "assist" the evening loads (as much as 250W can assist things) up to a minimum SoC. The peaks and the evening loads run from the grid. Tomorrow, when the sun is up, we recharge the batteries and power all the loads again.

If the grid fails, we can run anything up to 1kw for as long as the batteries hold. I have little battery capacity right now... but that covers almost everything in the house, bar the microwave (the vacuum cleaner is border-line).

This system is going to ROCK with Li-Ion.

If I had the money back in 2013, I would have gone with a 3kva inverter. But I didn't... and I'm almost okay with it. The one thorn in my flesh: The tumble dryer runs during the day, and with very little effort I can completely cancel that thing out... but at 2.2kw peak I can never cancel out more than 50%. If I had a 3kva inverter and the fabled Li-Ion battery I dream of... the sky would be the limit.

Something to note though: If you go Multiplus with ESS, the MultiGrid would be the better option (it's a multiplus with the added extra anti-islanding required by NRS097-2-1). This inverter is not on the local lists, but it does have German and Australian certification and I was told it's been tested by the local testing houses. I have to find out about that...

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