On Grid Solar

[phoneJunky]

But my load *IS* during those times! That's the whole freaking point! This isn't a household that we're talking about, this is a energy hungry business from home! My load are 24x7 actually.... When IDLE (i.e. all appliances off, except business related services), I sit here currently pulling 5A @ 220VAC, that's 1.1kW of energy...

There's two things that I want to address here,
1) I want to supplement feed by offloading energy from the Grid to Solar. Yes, even if that's just during those few hours during the day
2) I want to be able to run for those 2 or 3 hours during load shedding (we are shed from 4PM till 6:30PM), and I know there may not be enough sun left at those times to do what I want - especially not during winter.
3) I want to gradually scale this up (i.e. more panels / batteries) over time as budget allows.

I don't think it's unrealistic, and I don't think it is unreasonable too. Frankly, I actually believe very much that it is do-able...

Then you are going to have to look at something like this:

http://www.sustainable.co.za/sustainable-co-za-17kwp-grid-tied-system-3-phase-solar-power-kits.html

But from what I am reading you want a hybrid system. The one above is grid tied only - I only saw now that it is also 3 phase.

Couldn't find a hybrid one on sustainable that is that big, which will be more expensive than the one I listed, which is already expensive.

 

[oober]

1) I want to supplement feed by offloading energy from the Grid to Solar. Yes, even if that's just during those few hours during the day

Work on your average load rather, don't try to install solar for peak loads. I doubt your servers/home will manage to pull 12KW for 5/6 hours so installing such a big array, without batteries is not worth it. Unless you can do net-metering, then the whole story changes...

2) I want to be able to run for those 2 or 3 hours during load shedding (we are shed from 4PM till 6:30PM), and I know there may not be enough sun left at those times to do what I want - especially not during winter.

A grid tie system turns off during load shedding, you will not have power.

3) I want to gradually scale this up (i.e. more panels / batteries) over time as budget allows.

You cannot scale your battery bank, you buy a new bank each time. You can scale your panels.

You are confusing grid tied systems with hybrid systems. As per my suggestion and according to your needs you should rather get a hybrid inverter with an appropriate sized battery bank.

There are quite a few other things you should be aware of that we are not even mentioning since you only wanted to know if your calculations are correct or not...


Edit. You are setting yourself up for huge financial losses, aka ruined battery banks, if you are not interested to learn and listen to what people have to say.

You should maybe find out if your municipality has sell- or net metering tariffs, then going for a huge solar array makes more sense.

 

[savage]

Work on your average load rather, don't try to install solar for peak loads. I doubt your servers/home will manage to pull 12KW for 5/6 hours so installing such a big array, without batteries is not worth it. Unless you can do net-metering, then the whole story changes...

That makes sense too, in the case of a grid-tied system.

A grid tie system turns off during load shedding, you will not have power.

THAT I didn't know, and that does defeat the purpose most certainly. At least, it entirely wipes the biggest reason as to why I am looking at this. So if there's no supply from the grid the inverter goes bye bye.

You cannot scale your battery bank, you buy a new bank each time.

That I didn't know, and that doesn't make sense either. More batteries in series increases the voltage, more batteries in parallel increases the run time that you can get off those batteries, yes? If you have batteries in series to get, say 24V at 200aH, why can't you add additional strings of the same spec to the battery bank?

EDIT: The same can be asked for the PV array too.

You are confusing grid tied systems with hybrid systems. As per my suggestion and according to your needs you should rather get a hybrid inverter with an appropriate sized battery bank.

There are quite a few other things you should be aware of that we are not even mentioning since you only wanted to know if your calculations are correct or not...

Edit. You are setting yourself up for huge financial losses if you are not interested to learn and listen to what people have to say.

I'm quite sure that there's a lot of things that I'm not even thinking about (yet). I also never said I'm not prepared to listen (sigh). Before anything can be researched and/or looked at, you need to understand what you need to get. My question was in terms of what I would need to get...

The question now becomes, HOW do I get that... It's an entirely different discussion as far as I am concerned.

 

[P924]

If his house pulls 12KW+ loads constantly then it won't be a waste yes but will it have such constant loads?

I think we talked past each other. I have been working with the assumption that you could do grid feed in capetown. But if that is not the case I understand what you meant.

 

[oober]

That makes sense too, in the case of a grid-tied system.

That I didn't know, and that doesn't make sense either. More batteries in series increases the voltage, more batteries in parallel increases the run time that you can get off those batteries, yes? If you have batteries in series to get, say 24V at 200aH, why can't you add additional strings of the same spec to the battery bank?

...

I'm quite sure that there's a lot of things that I'm not even thinking about (yet). I also never said I'm not prepared to listen (sigh). Before anything can be researched and/or looked at, you need to understand what you need to get. My question was in terms of what I would need to get...

The question now becomes, HOW do I get that... It's an entirely different discussion as far as I am concerned.

You can scale the batteries, up to a point, when they are all the same age, size, type.. I meant you cannot add new ones later on. Unless you want to ruin them of course.

 

[oober]

I think we talked past each other. I have been working with the assumption that you could do grid feed in capetown. But if that is not the case I understand what you meant.

+1 Net metering makes things so much easier and worth while... He needs to find out if he can do it.

 

[savage]

You can scale the batteries, up to a point, when they are all the same age, size, type.. I meant you cannot add new ones later on. Unless you want to ruin them of course.

Uhm, yes of course. Even two penlights in a flash flight, you never mix old and new batteries. That's obvious.

+1 Net metering makes things so much easier and worth while... He needs to find out if he can do it.

Feed is directly from Eskom (not municipality). As far as I am aware they (and NERSA) is busy looking into it but nothing definite yet as far as I know?

The fact that grid tied inverters goes dead with the feed, does change quite a lot however yes. This now essentially means I will -have- to go Hybrid, and I wanted to try and avoid batteries due to the maintenance (and costs). So is hybrid worthwhile and sustainable, maybe, maybe not. All I know is I don't want something that requires that amount of maintenance.

To store say, a 1.1kW / 2kW load and be able to run off batteries for 3 or 4 hours - that's a serious amount of batteries that we're talking about IMHO.

Even a grid-tied system with a say 10KVA/20KVA UPS will still require quite a battery bank for the runtime required, the question is how much batteries, and how much maintenance then I suppose.

At the end of the day, I suppose it boils down to there's no such thing as a free meal.

 

[P924]

Uhm, yes of course. Even two penlights in a flash flight, you never mix old and new batteries. That's obvious.




Feed is directly from Eskom (not municipality). As far as I am aware they (and NERSA) is busy looking into it but nothing definite yet as far as I know?

The fact that grid tied inverters goes dead with the feed, does change quite a lot however yes. This now essentially means I will -have- to go Hybrid, and I wanted to try and avoid batteries due to the maintenance (and costs). So is hybrid worthwhile and sustainable, maybe, maybe not. All I know is I don't want something that requires that amount of maintenance.

To store say, a 1.1kW / 2kW load and be able to run off batteries for 3 or 4 hours - that's a serious amount of batteries that we're talking about IMHO.

Even a grid-tied system with a say 10KVA/20KVA UPS will still require quite a battery bank for the runtime required, the question is how much batteries, and how much maintenance then I suppose.

At the end of the day, I suppose it boils down to there's no such thing as a free meal.

2kW with 8kWh of batteries @2000 cycles will be around R35k for batteries and R15k for a 2kw bidirectional inverter. (Actually you should be able to get a 3kW for 15k). If you use less than 8kWh the batteries will last longer.

You will still need to add installation and a watering kit for the batteries.

 

[savage]

You will still need to add installation and a watering kit for the batteries.

And let's not forget real-estate too... All those batteries need to stand somewhere...

+-35K for batteries,
+-35K for gried tied inverter (let's be conservative)
+-60K for PV panels,

Somehow I think a large UPS may just be cheaper...

 

[oober]

And let's not forget real-estate too... All those batteries need to stand somewhere...

+-35K for batteries,
+-35K for gried tied inverter (let's be conservative)
+-60K for PV panels,

Somehow I think a large UPS may just be cheaper...

Also you won't be able to run your whole house from this sort of setup. Your geysers will kill it.

You really need to analyse your usage and work from there.

You cannot mix grid tied inverter with batteries. . You would need either a hybrid inverter, can do both, or get a grid tied inverter and a bi-directional inverter.

Ohh and by looking at your setup I'm assuming 2KW contant load? So for 4 hours you would need 8000W stored. This translates to about 18000W of battery capacity or about 375 Amp Hours@48 Volts.

This is at about 50% discharge which will give you the shortest acceptable battery life. You need something like this and you'd need 8. So about R40k for batteries yes.

 

[Arthur]

Talk to MLT Drives. Their HO is in Kenilworth. www.mltdrives.com. They have hybrid grid-tied inverters designed and made for local conditions.

I've used them since 1999, and currently have a 12kW array at my house with a 12kVA Powerstar II (could only get single phase here). They have 18kVA and 24kVA 3-phase hybrid grid-tied inverters. A few months ago they established a separate division focusing on inverters, here.

 

[savage]

Also you won't be able to run your whole house from this sort of setup. Your geysers will kill it.

Any element will kill it. Hair Dryers, Kettle, Geyser(s), Heater(s) Not only in term of solar generation, but even a UPS too...

I suppose I would have to sit and think about this and make some choices, i.e. what's more important... Save monthly by paying less for my electricity bill (generate my own with PV - even if it's 5kWH instead of 12kWH) and go grid-tied, or, continue to be able to work in the case of load shedding and not loose the production time (i.e. UPS).

Maybe a better option would be to generate grid-tied say, 1.5kW only to lessen the load during the day (this is what is killing me, as the household is not "switched off" during the day when 99% of ppl are at work), plus combining a UPS for runtime during load shedding...

To be efficient regardless of which route I take, I will have to rewire the house in any case, period. There's no getting out of that. At least with that option the house can be brought up to spec in terms of COCs and what not (it is a mess). But ai... Dedicated plug points, trenching into walls, new DB boards... It's not the money that's putting me off, it's the amount of work required!!!!

 

[oober]

Talk to MLT Drives. Their HO is in Kenilworth. www.mltdrives.com. They have hybrid grid-tied inverters designed and made for local conditions.

I've used them since 1999, and currently have a 12kW array at my house with a 12kVA Powerstar II (could only get single phase here). They have 18kVA and 24kVA 3-phase hybrid grid-tied inverters. A few months ago they established a separate division focusing on inverters, here.

+1. Arthur recommended them to me and I'm also very happy with their service and products. The inverter is quite expensive though. About R40k for the entry level hybrid 6KVA.

 

[wetkit]

Savage, I would reccomend you look at the MLT range of invertors.
It is a local company, but they make good equipment. They do big invertors that will do everything you looking for. The MLT Powerstar range is hybrid invertors with loads of added features.
Doing the complete house in a single go will save you money on wiring and system complexity, but it will cost you on the solar side.
Doing only a couple of small changes you will still be able to save money on electricity cost, but halve your solar system outlay cost.

I think something screwed up your billing during June/July, as the avg does not look too bad.

Regarding servers, sometimes it works out cheaper on energy cost to run newer less power hungry servers than the old stuff just generating heat. Cutting down on your day to day overheads will make you more money in the long term....

 

[savage]

Talk to MLT Drives. Their HO is in Kenilworth. www.mltdrives.com. They have hybrid grid-tied inverters designed and made for local conditions.

I've used them since 1999, and currently have a 12kW array at my house with a 12kVA Powerstar II (could only get single phase here). They have 18kVA and 24kVA 3-phase hybrid grid-tied inverters. A few months ago they established a separate division focusing on inverters, here.

Arthur - if you don't mind me asking... What did the kit (only) set you back? I take it you're located in CPT? Where abouts? Would be interesting to pop over

 

[Arthur]

Arthur - if you don't mind me asking... What did the kit (only) set you back? I take it you're located in CPT? Where abouts? Would be interesting to pop over

I'm in Oudtshoorn - moved from Joburg a few years ago. Much the same latitude at Ctn. Plenty of sun in the Little Karoo. You're welcome to pop in in anytime, just drop me a PM.

 

[savage]

Bit far to drive

 

[savage]

Doing the complete house in a single go will save you money on wiring and system complexity, but it will cost you on the solar side.
Doing only a couple of small changes you will still be able to save money on electricity cost, but halve your solar system outlay cost.

But this is exactly what I would need to find out more about. In the case of grid-tied OR hybrid for that matter... Why can't you start with say a 12KW inverter (so that you don't have to replace it after a few years), but gradually build up your PV array and batteries?

if I have a 12KW inverter, and 500W in PV, surely the inverter should just pull more from the Grid? As the PV array increases, the load from the grid should just become less, not so?

In the case of batteries, let's say you work on a 3 year replacement (cheap batteries for a reason), why can't you just gradually increase the size of your battery bank every 3 years?

Say, you start at a 12KW inverter, but with 500W PV cells growing by say 10% or 25% per year, whilst your battery bank is expanded by say 25% every 3 years when it's time to replace the battery bank?

That means that your initial outlay is less, but yes, on the other side of the coin it will mean commitment and investment from the owner's side in terms of expanding and scaling the system...

There MUST be a way that you can gradually scale and build these things out. What if I (or anyone) invest R500K into a system, and outgrow it in 3 years due to what ever reason? Do they now throw the system out in it's entirety and put in a new system from scratch, meaning now you need to fork out another R750K for a upgraded system?

I think something screwed up your billing during June/July, as the avg does not look too bad.

Yes - they didn't send a bill in June (not an estimate or actual), so July was double billed (June + July). The efficiencies of our government, what can you do...

 

[oober]

if I have a 12KW inverter, and 500W in PV, surely the inverter should just pull more from the Grid? As the PV array increases, the load from the grid should just become less, not so?

Yes if you foresee you would need such big loads it will be better to get a big inverter. R70k excl. VAT

In the case of batteries, let's say you work on a 3 year replacement (cheap batteries for a reason), why can't you just gradually increase the size of your battery bank every 3 years?

Life cycle for batteries are usually 5-10 years but if you are willing to reinvest in a new bank every three(3) years you can do it. Your return on investment will just be out the window by a large factor.

Say, you start at a 12KW inverter, but with 500W PV cells growing by say 10% or 25% per year, whilst your battery bank is expanded by say 25% every 3 years when it's time to replace the battery bank?

Generally you should not really mix solar panels, you are asking for trouble. You'd typically install a new solar array with a new charge controller. So you will have a new array and an old one.

...

There MUST be a way that you can gradually scale and build these things out. What if I (or anyone) invest R500K into a system, and outgrow it in 3 years due to what ever reason? Do they now throw the system out in it's entirety and put in a new system from scratch, meaning now you need to fork out another R750K for a upgraded system?

Yes if you do not size your system correctly then you are forced to sell and buy new components. Except for your solar arrays which you should be able to keep. Or keep your older components and split your house's usage between the old system and new system.

 

[savage]

Yes if you do not size your system correctly then you are forced to sell and buy new components. Except for your solar arrays which you should be able to keep.

I don't see it as a sizing issue. It's called growth. Over time, people/businesses require more energy, period. It's unfortunately a fact of life.