12 hours ago, flamegrilled said:

@Elbowhave you done any Youtube research on the AMI meter? I did and did not like the meter after that and to make things worse you have to pay upfront and a monthly fee.

Hi,

Yes, I decided that for me I will register my setup as off-grid and implement it that way.

I’ve come up with a design that puts most of the high total energy using stuff on the inverter, but leaves the intermittent but power-hungry stuff (appliances etc) on the grid.  I’ll put a changeover switch for the appliances so under my control something like the microwave can be used on the inverter in a power cut.

the net benefit of this comes out better than paying for the AMI meter and I think will get quite close to what my 3.5kw array can deliver in terms of energy.

I’ll find out in practice and I can always tweak.

 

6 minutes ago, Elbow said:

power-hungry stuff

Gas cooking,Solar water heating PV or thermal and the IOT to control/monitor the devices.

16 minutes ago, flamegrilled said:

Gas cooking,Solar water heating PV or thermal and the IOT to control/monitor the devices.

Yeah - I've got gas hob, but electric oven.

My hot water uses about 4.5kWh/day so its not the biggest user of energy in my house.

I have Openenergymonitor so I know lots of detail about what uses what and when.

I have Homeassistant/NodeRed and smart power switches so I will use that to manage loads as I go along.

32 minutes ago, Elbow said:

hot water uses about 4.5kWh/day

I  had an EVT system experience  in our previous house.

Changed to PV heat water system with ptc element in current house as the EVT system gave problems all the time.It was not regulated (IOT).It got too hot in summer.

The non returned valve packed up(inner melted).The brass pump stopped(sediment) and high pressure protection valve went too.

The PV system allows for 2 HWC's or 1 HWC and one Battery bank charge.The EVT system can only heat water.The PV system gives you more options IMO.

 

43 minutes ago, Elbow said:

Homeassistant/NodeRed

Installed on a PI yes I agree.I have not got there yet.

3 hours ago, flamegrilled said:

The PV system allows for 2 HWC's or 1 HWC and one Battery bank charge.The EVT system can only heat water.The PV system gives you more options IMO.

Heating water with PV is much much less efficient than using a regular solar geyser. 

But if you have spare power from your panels above your daytime load and battery charging then pushing it to a low power element in the geyser can make sense. 

In my case 4.5kWh of electricity needed to heat the water. With a 1kw element I could put that into the geyser in 4.5 hours (existing 3.2kw element can do it in 1hr 20 mins or so) 

A 1kw heatpump is also an option and much more efficient (3x apparently) than a traditional geyser.  So with that you could do the job with 1.5kwh from the solar. 

Edited February 24, 20197 yr by Elbow
More to say

1 hour ago, Elbow said:

Heating water with PV is much much less efficient than using a regular solar geyser. 

But if you have spare power from your panels above your daytime load and battery charging then pushing it to a low power element in the geyser can make sense. 

Agreed, if you have spare.

Why waste precious restricted PV resources on heating water, as @phil.g00 has so eloquently pointed out.

7 hours ago, The Terrible Triplett said:

Why waste precious restricted PV resources on heating water, as @phil.g00 has so eloquently pointed out. 

I hear lots of people complaining about overheating EV systems, and then they go for PV heating instead. Am I the only one who wonders why the conventional flat-plate got skipped? That thing might not be particularly efficient when its overcast... but neither is PV... and it still kicks PV-butt in terms of efficiency AND doesn't have the overheating issues (I'm specifically talking about a thermosyphon system). I have one on my roof... I haven't been up there in years... okay I was up there last week to make sure these rats with wings (aka wild doves) aren't nesting up there... but I haven't been up there for the water heater! And while I was up there I noted that the worst bit of wear is that the plastic cap on the thermostatic valve has been burned a little white by the sun (but it's still perfectly operable)...

🙂

8 hours ago, plonkster said:

Am I the only one who wonders why the conventional flat-plate got skipped? That thing might not be particularly efficient when its overcast... but neither is PV... and it still kicks PV-butt in terms of efficiency AND doesn't have the overheating issues (I'm specifically talking about a thermosyphon system)

Agree 100 % with @plonkster. 

A simple flat plate collector, painted black in a thermosyphon confirguration is the cheapest and most effective way to heat water in South Africa. It will kick the butt off any pumped system, PV system or heat pump system by a long way. 

The only potential issue, in my opinion, is that you have no way of controlling the heating (i.e. You cant switch it off.) so if you oversize your panels (to cater for winter radiation) you may end up with overheating issues in summer. The efficiency of the flat plate collector drops off at higher temperatures which goes some way to alleviate this overheating issue.

On my house i have a thermosyphon system that was installed in 2007 and it hasn't given me any issues at all. Last year, my backup electrical element consumed less than 50 Kwhr for the whole year. 

In comparison i have a rental property with a Pumped Solar system and a selective coated flat plate collector which was installed in 2012. I have had endless problems with the temperature probes failing on the collector (during Stagnation this particular collector reaches temperatures of around 280 degress celcius), the pump has burnt out once and the Non Return Valve flap broke once. 

3 minutes ago, Carl said:

A simple flat plate collector, painted black in a thermosyphon confirguration is the cheapest and most effective way to heat water in South Africa. It will kick the butt off any pumped system, PV system or heat pump system by a long way. 

 

Hi,

You said the same to me in person. And it is very good to have hear from someone with practical experience.

Are there physical constraints to thermosyphon systems - the panel positioning relative to the geyser itself?  Presumably you also need a geyserwise or home made control system to turn on the electric element if required (or, mark-I eyeball and a switch...)

My point about heating with PV was simply that if you put in a typical 3Kwp PV system then it is likely to have excess capacity much of the time.  So you can opportunistically divert some to hot water as and when load permits.  It maximizes the use of the system you already have and understand.

So it’s an incremental cost argument - only requiring a lower power element, a temperature probe, and a little bit of control logic.

 

 

I'll tell you what I have installed. This might not be what everyone wants to do, but it works well enough. I have a normal electrical geyser, and this is fed FROM my solar geyser, in other words it is a prefeed system. This means I need to use a little electricity to keep the internal tank hot, especially for morning showers (around than 2KWh a day). The collector on my 150liter thermosyphon system is not oversized, so in the three coldest months it might be accurate to say that this thing is just about useless. The rest of the year it makes far more hot water than I could with the same area of PV. The remainder... that I can actually heat with surplus PV, and a simple time switch.

I didn't plan this, this is sort-of just how it worked out, and I like it. It's not an either/or setup. It's both-and. I heat water both with PV and directly... mosly directly 🙂

Seems this has gotten off topic a bit here...

I am posting the following to CoCT, please have a look an see if I missed anything that hasn't been answered in these posts. 

Sending this on Tuesday (2019/03/05):

1.       Various questions came through regarding more specific assistance from City of Cape Town. I believe I noted something similar in regard to the guidance document last week (updating this to be more accurate and specific). Is this currently being worked on at this time?

2.       On the previous communication there was more confusion than clarity on the following statement: “The generation capacity is declared in GEN/OFF-GRID and GEN/EMB”

·         I would like to go back to a practical example: If the Hybrid Inverter of 5kVA is installed with 3kW of PV modules, with battery back-up. What and how should this be reported on the forms and be understood?

                                                               i.      Would Gen/Off-Grid be 5kVA

                                                             ii.      Would GEN/EMB be 3kW

                                                           iii.      Will you be able to install this on a 60A breaker? (As I understand the section quoted the answer here is no, please verify)

3.       Change over switch (continued): You noted the following: “If the inverter don’t have a separate interlocked change-over switch compliant with Appendix 4, use the output of the inverter switch to automatically control the separate change-over switch, else operate manually”

·         Do you have practical examples of how this was implemented and with which inverters?

·         Both Victron and GoodWE ES does not have facility to communicate with an external change over / disconnect switch. Thus the unit will (<20ms) connect the “back-up” side of the inverter to battery back up (or in case of Victron it is permanently on “battery-mode”).

·         This would in effect result in non-compliance to the CoCT requirements?

·         Previously you noted the standards, but is there a practical way of actually doing this? The only change over switch configuration that can be implemented would be on the back-up side or grid-out side.

4.       For Installation (legacy / old) that exceed the NRS097-3 limits, how would a person proceed to get this signed off (example here: the correct approach for owners with existing systems with inverters exceeding the above limit is. A Goodwe GW5048D 4.6kW inverter with 4.4kW of PV and 20kWh battery capacity. The grid supply is single phase 60A with a prepaid meter ALSO 4.4kW Grid Tied on a 60A breaker)

·         In short how to approach CoCT if limits are exceeded, is there a way to get confirmation and acceptance?

5.       How does City of Cape Town define? [Very basic but it must be clarified]

·         Grid-tie

·         Grid connected

·         Hybrid

6.       In the requirements you refer to a Reverse Power Flow Relay, can you please define this as this is confused with reverse power flow blocking for purposes of not exporting (via internal Inverter / external CT measurements and curtailing the Embedded Generator).

7.       What is the average response time from CoCT from submitting (Step 1) to receiving a response (currently)

24 minutes ago, Rautenk said:

I am posting the following to CoCT, please have a look an see if I missed anything that hasn't been answered in these posts. 

I think this is great.  Thanks.

I just did "Step 1: Log a service request" to start my process so lets hope this road isn't too bumpy.

 

Seems we are running 2 similar threads: https://powerforum.co.za/topic/2862-coct-extends-registration-date-for-solar-systems/page/6/?tab=comments#comment-46721

20 hours ago, Rautenk said:

2.       On the previous communication there was more confusion than clarity on the following statement: “The generation capacity is declared in GEN/OFF-GRID and GEN/EMB”

·         I would like to go back to a practical example: If the Hybrid Inverter of 5kVA is installed with 3kW of PV modules, with battery back-up. What and how should this be reported on the forms and be understood?

                                                               i.      Would Gen/Off-Grid be 5kVA

                                                             ii.      Would GEN/EMB be 3kW

                                                           iii.      Will you be able to install this on a 60A breaker? (As I understand the section quoted the answer here is no, please verify)

Hi there @Rautenk - could you add batteries to this example to try understand also the effect of the storage on the generation limits that is mentioned in the NRS definitions?

Just received the following email from the CoCT regarding my SSEG application. As suspected they will at the moment not accept more than 3.5kW on a 60A supply. I will wait for the reply Rautenk receives to his questions regarding this issue. In the meantime I will also explore the possibility to upgrade to an 80A supply.

 

"

Good morning Mr.

Please note that for your SSEG application you’ve indicated that your capacity embedded generation is 4.6 and the size of your existing house is 60A single phase. Kindly note that the maximum you’re allowed to generate is 3.5KVA as per the size of your supply on your premises. Kindly see attached SSEG Guideline (see page 14) for the maximum sizes allowable on residential premises. This information is also available on the website.

 

Kind regards,

 

Yonela Makuleni
Service Connection Planning - East

 

First Floor, Section, Electricity Head Office
Bloemhof Street, Bellvile 7350

 

Tel: 021 444 8532
Email: [email protected]
Web: www.capetown.gov.za

"

 

2 hours ago, Fuenkli said:

Just received the following email from the CoCT regarding my SSEG application. As suspected they will at the moment not accept more than 3.5kW on a 60A supply. I will wait for the reply Rautenk receives to his questions regarding this issue. In the meantime I will also explore the possibility to upgrade to an 80A supply.

 

"

Good morning Mr.

Please note that for your SSEG application you’ve indicated that your capacity embedded generation is 4.6 and the size of your existing house is 60A single phase. Kindly note that the maximum you’re allowed to generate is 3.5KVA as per the size of your supply on your premises. Kindly see attached SSEG Guideline (see page 14) for the maximum sizes allowable on residential premises. This information is also available on the website.

 

 

 

Kind regards,

 

 

 

Yonela Makuleni
Service Connection Planning - East

 

 

 

First Floor, Section, Electricity Head Office
Bloemhof Street, Bellvile 7350

 

 

 

Tel: 021 444 8532
Email: [email protected]
Web: www.capetown.gov.za

"

 

I would love to know why they limit it to 3.5Kw. Most people, who can afford solar systems can easily go above 3.5Kw/hr during an average day. Our washing machine uses 3Kw. The tumble dryer (although only used on cloudy days) uses 2Kw. Make coffee while the tumble dryer is on you and're above 4KW. 

This just doesn't make sense. 60A @ 220V = 13.2Kw 

56 minutes ago, SilverNodashi said:

I would love to know why they limit it to 3.5Kw

It's not about the size of the cable. It is about how much the supplier has to "pick up" if your embedded generator trips. Imagine a brown-out condition where the voltage momentarily sags to 180V. Now imagine an entire neighbourhood of embedded generators tripping (as they should according to regulation). As it is (with 3.5kw limits), it means 25% pick-up... roughly the same kind of thing that happens when you turn everyone's geysers on with a ripple-switch.

24 minutes ago, plonkster said:

It's not about the size of the cable. It is about how much the supplier has to "pick up" if your embedded generator trips. Imagine a brown-out condition where the voltage momentarily sags to 180V. Now imagine an entire neighbourhood of embedded generators tripping (as they should according to regulation). As it is (with 3.5kw limits), it means 25% pick-up... roughly the same kind of thing that happens when you turn everyone's geysers on with a ripple-switch.

But you're not supposed to feed back to the grid when the power fails, or even if there is a brownout. I would imagine that the inverters on the approved list would not feed back above and below certain thresholds, probably 200-240V?

1 minute ago, SilverNodashi said:

But you're not supposed to feed back to the grid when the power fails, or even if there is a brownout. I would imagine that the inverters on the approved list would not feed back above and below certain thresholds, probably 200-240V?

I think you're misunderstanding me. Imagine we're happily bowling along at 230V, and then a brownout event drops the voltage to 180V for 2 seconds before picking up again. Suddenly all the embedded generators in that part of your city/country disconnect (as they should). Suddenly you have to pick up an extra 25% load on the upswing... and this happens precisely because regulations and/or safety requirements says your embedded generators must disconnect (then wait 60 seconds before reconnecting).

If you let everyone feed in as much as the cable can handle, then the pickup is much more severe.

Now of course you might argue that not everyone has an embedded generator, so the total number is far from 25%. That is true, but also remember that this 25% is also only an "automatic" number, one you can do without too much extra homework. It is possible to do more... it just takes a lot more paperwork... a lot more money... more engineers and impact studies and things.

Anyway, so that is the WHY of it. It's about planning.

1 hour ago, plonkster said:

I think you're misunderstanding me. Imagine we're happily bowling along at 230V, and then a brownout event drops the voltage to 180V for 2 seconds before picking up again. Suddenly all the embedded generators in that part of your city/country disconnect (as they should). Suddenly you have to pick up an extra 25% load on the upswing... and this happens precisely because regulations and/or safety requirements says your embedded generators must disconnect (then wait 60 seconds before reconnecting).

If you let everyone feed in as much as the cable can handle, then the pickup is much more severe.

Now of course you might argue that not everyone has an embedded generator, so the total number is far from 25%. That is true, but also remember that this 25% is also only an "automatic" number, one you can do without too much extra homework. It is possible to do more... it just takes a lot more paperwork... a lot more money... more engineers and impact studies and things.

Anyway, so that is the WHY of it. It's about planning.

I do understand what you're saying, but I am trying to argue that in no event should you feed back if there's a power failure (hence the reason for this regulation), but you raise a valid point, 2 seconds is very quick and it might be too quick for most devices to stop the back feed. 

 

That being said, surely there should be a technical way around this? 

Just now, SilverNodashi said:

I do understand what you're saying, but I am trying to argue that in no event should you feed back if there's a power failure (hence the reason for this regulation), but you raise a valid point, 2 seconds is very quick and it might be too quick for most devices to stop the back feed. 

 

That being said, surely there should be a technical way around this? 

I don't think you are understanding.  It's not about the feed back, it's about the stopping of the feedback. 

Let's say 100 10kw sseg systems in a neighbourhood.  Pushing 1MW into the grid.  Maybe there are 1000 homes behind that transformer and drawing average of 2kw each, so 2MW of load. 

Half the load is being carried by the solar systems. 

Oops - brown out. 

All those inverters follow all those fancy requirements.  So klunk klink klunk, they all drop off the grid at the same time. 

But all those houses didn't get the memo and the stoves keep stoving, and the geysers keep geysering, and etc. 

So suddenly that transformer has to double its output. 

Since a Power grid is an ac system - a very very low frequency tuned circuit - it is not going to enjoy that sudden change. 

I guess the result could be bang for that transformer, a trip for the whole area, or...? 

 

51 minutes ago, SilverNodashi said:

2 seconds is very quick and it might be too quick for most devices to stop the back feed. 

The brownout causes the generation to get lost... but the loads remain on. So 2 seconds later... still have to carry all the load, but 25% of the generation has left the building. The effect is more load on the supply side that has to be "picked up"... precisely at the time it would have been kinda useful to have that extra generation!

Edited March 7, 20197 yr by plonkster

1 hour ago, Elbow said:

Let's say 100 10kw sseg systems in a neighbourhood.
I guess the result could be bang for that transformer, a trip for the whole area, or...? 

And yet still we debate over and over the "why's" of not being allowed to install what "I" want.

Be gone the regulators and regulations!!!
How DARE "they" limit me from using my 2 x 10kva proudly Chinese grid tied hybrid inverters (no "papers")!!
That I installed myself (I have no "papers" either) because "I KNOW electricity"!!! ... my grandpa taught me,

🤣

14 hours ago, plonkster said:

It's not about the size of the cable. It is about how much the supplier has to "pick up" if your embedded generator trips. Imagine a brown-out condition where the voltage momentarily sags to 180V. Now imagine an entire neighbourhood of embedded generators tripping (as they should according to regulation). As it is (with 3.5kw limits), it means 25% pick-up... roughly the same kind of thing that happens when you turn everyone's geysers on with a ripple-switch.

Could take it a step further, even some cloud cover passing over a neighbourhood could cause random dips and surges in localised power output onto the grid. 

16 hours ago, SilverNodashi said:

I would love to know why they limit it to 3.5Kw. Most people, who can afford solar systems can easily go above 3.5Kw/hr during an average day. Our washing machine uses 3Kw. The tumble dryer (although only used on cloudy days) uses 2Kw. Make coffee while the tumble dryer is on you and're above 4KW. 

This just doesn't make sense. 60A @ 220V = 13.2Kw 

With SSEG/Grid-tie I think the point is not so much what your maximum or instantaneous power requirements are, but how much power you generate and exchange in parallel to the grid over an extended period. So say 3.5kW of panels will generate maybe 18-20kWh of power per day. Boiling the kettle for 5 minutes will consume just 0.16 kWh of that, and the washing machine may consume for argument's sake 1.5 - 2 kWh over the entire wash cycle, even if it needs more power during the short spin cycle. Maybe best to match the energy consumption to production and make peace with the fact that grid tie means remaining dependent on the grid.