I think it's safe to say that the only thing worse than not having a solar system, is having under-utilised capacity 😮‍💨

 

Ok first, some background and system context.

 

This 6kWp PV is split into two arrays (Figure 1). My main array (feeds AC loads and charges batteries) is a 4.8kWp array (12x 405W panels in a 4S3P configuration). The remaining 3 panels heat our 200L geyser via an PowerOptimal Elon 100 system.

 

 

Based on the NREL PV Watts Calculator, my 4.8kW array has an average generation capacity of 24kW per day. I graphed my daily consumption averages (based on the last three years' utility bills). This brings our average daily consumption (across all months) to 48kW (Figure 2). 

 

 

 

 

 

 

 

 

 

 

 

 

Here's the part that irks me...

 

My installer has done a good job of bringing as many loads as possible to run off solar/battery. The only excluded loads are my electric stove/oven, one central A/C unit and two 150L geysers. You'll notice that while the delta between my generation capacity (based on NREL figures) and consumption is significant (Figure 3), I'm expecting a trend closer to the one shown for December as we've only had our solar system installed since mid'ish November.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

All that said, my ratio of grid vs solar consumption figures is what's grinding my 🥕 given that my generation capacity and average usage should bring me closer to 80%+ solar consumption...

November: Grid: 59.9% // Solar: 40.1%

December (so far): Grid: 43.4% // Solar: 56.6%

 

I know I'm not using anywhere near the capacity I have in my system (average daily PV generation for Nov and Dec respectively is 12.43kW and 14.42kW) which means I'm paying City of Tshwane/Eskom more than I need to.

 

Now onto my request for advice..

 

I was hoping to have an EM24 three-phase energy meter installed before my installer closed shop for December, but alas no joy so will have that put in as early as possible in January. My motive is to quantify who the big offenders are from a grid usage POV and put in whatever measures are necessary to replace/minimise that usage.

 

If you either own or have experience with a similar sized system and usage patterns, what would your advice be in terms of interventions and priority.

 

My current thinking is to follow this sequence (but mindful of my lack of experience/knowledge hence the ask for input)

 

1. Install energy meter and quantify usage
2. Replace (what are likely 3kW) elements in my two 150L geysers with 1.5kW ones
3. Consider replacing our electric hob/oven with an induction hob–current setup is rated at 7.5kW (hob) and 3.65kW (oven) – I'm really keen to hear from those who've had induction hobs installed and what your tips would be to manage peak loads etc..
4. Add an extra 4.8kW Pylontech UP5000 battery to increase storage capacity (which I'd like to hold off as long as possible to reassess my actual energy storage requirements)

 

Appreciate any and all inputs!

 

I am mindful that these are in all likelihood the cries of an impatient noob and the fix may well be some patience on my part 🙈

Edited December 27, 20213 yr by Bigawatt

You have just discovered the solar power problem; optimization of solar production. Some people have fancy PI systems to heat geysers etc when the sun shines and then turn off when the PV production is low...

Depending on where you are situated, a rule of thumb;

In Winter you'll probably get 4 * 4.8= 20kWh/day 

In Summer (in JHB, I get my peak yield in Sept, Oct) max of 6*4.8 = 29 kWh/day if there no cloud, rain, high temperatures etc.

Of course that is over the entire day, so to perfectly optimize your load will have to mirror PV production, which is virtually impossible.

I cook on gas and have a solar tube assisted geyser which helps.

Use whatever power you have to charge your batteries and then deplete your batteries from 10pm to 7am. make use of 10am-2pm solar production to heat geyser etc...You have to align your load with solar production which is very difficult to do..

Thanks @FixAMess – my takeaway from your comment is that I'd be better off focusing on optimising the various appliances, including geysers etc..

I'm already using PV to heat my largest geyser and cycle my batteries to a minimum 20% DOD (although by the time the PV kicks in the next day, I'm usually sitting at 45-50% SOC). Would agree that trying to align loads to solar production is not an option, the incremental gains aren't worth the admin and effort IMO. 

I had a quick look at my long term usage...

 

1 hour ago, FixAMess said:

I had a quick look at my long term usage...

 

Interesting... If I'm following this graph, it's showing how much of your PV yield is being used (e.g you used approx. 80% of your total yield in Nov). Can you share what your array capacity and typical total monthly consumption for context?

Sorry its not what I've used its the % of load self generated...

 

Also, generation Vs Consumption....%kW inverter and 6075W installed panels.

Edited December 27, 20213 yr by FixAMess

Ah ok understood! Thanks!

@Bigawatt

My 2c worth:

You've not indicated if you are feeding excess PV power to the grid, from you explanation it seems you are not.

>Based on the NREL PV Watts Calculator, my 4.8kW array has an average generation capacity of 24kW per day.
You can only generate as much Solar as you use or store at that instant in time.
if your batteries are full and your load is low, there will be limited draw from the panels.

The below image shows what happens with me, I'm not feeding the grid.
After +/-11:30am, the battery gets full and solar production drops because there is nothing to consume the solar.
For the rest of the day after 12:00, the spikes are geyser and normal house loads.



>3 panels heat our 200L geyser via an PowerOptimal Elon 100 system
Tip: Normally you would just add the 3 panels to the Victron and use a timer to limit to sunlight time.

>The only excluded loads are my electric stove/oven, one central A/C unit and two 150L geysers
Your diagram is not detailed enough in terms of how the non-essential / excluded loads loads are connected.
There are two ways to connect "excluded loads" - the ACout2 or the ACin1.

If your "excluded loads" are on the ACin1 side, you need the EM24 or Current Sensor / CT coil to implement PowerControl & PowerAssist.
Below is a typical diagram showing the current sensor just after the meter, before the "excluded loads".
Victron PowerContol & PowerAssist.

As stated the "excluded loads" can be connected on ACout2 or ACin1 (between the Current Sensor and the Metro's meter).
If connected on ACin1, the inverter can be programmed to feed excess into the "ACin1" to power "excluded loads".
It will use the Current Sensor provide just enough to power the "excluded loads" but not enough to feeding back to the grid.

>Replace (what are likely 3kW) elements in my two 150L geysers with 1.5kW ones
Just use timers to ensure that geysers come on during sunlight hours.
I've set my geyser timers as follows:

• 11:30am - 16:00pm (sunlight) after the battery full
• 5:00am to 6:00am (so I can have a warm shower in the morning)

Note: I have a SunSynk and there are settings which can limit PV power use - took a while to get my settings optimal.
I assume Victron would have similar settings.

In general, for Solar I have the following tips:
1) Measure, measure, measure.
Know where and when your electricity is being used.
I've used a "kill-a-watt" meter (~R500) and then upgraded to "tasmota/tuya" smart power plugs.
2) Become efficient first and you will save 3x
- Use LEDs globes - get rid of CFL & incandescent
- Make sure you PC & PS4 goes to sleep - mine uses 50w with the screen off and 2.5w in sleep mode.
- Replace your PC with a laptop - uses less
- Use a solar geyser or a heat exchange geyser
- Use gas for cooking or induction stove
- Use AAA rated appliances (test with kill-a-watt first) eg. Heat Pump Tumble dryer vs traditional dryer.

For every Watt saved, you save 3x because you need less panels, less battery and less inverter.

I also notice you have "pool pump, Diswasher, Washing machine, Air Cons" on "Critical Loads" - these would normally be on ACin1 or ACout2.
The inverter will still power ACout2, except during power fail / load shedding lengthening the uptime of critical loads.
Ensure the pool pump timer runs only during the day.

Hope this helps.

Super helpful @system32 thx!! 

 

Quote

You've not indicated if you are feeding excess PV power to the grid, from you explanation it seems you are not.

I'm not feeding excess power back to the grid, understand the point you made about generation being limited to charging/demand–hence my search for options to move loads over to solar to increase utliisation (lower wattage geyser elements, induction stove etc)
 

8 hours ago, system32 said:

Tip: Normally you would just add the 3 panels to the Victron and use a timer to limit to sunlight time.

Thanks for the tip! Including the 3 panels as part of the main array would be ideal as this would make it visible in Victron Remote Management. The Elon system was installed after the solar was done, so I'll get in touch with my installer to make this change. I already have my 200L geyser set to use only PV for heating between 3am and 5pm, so as long as we take our showers in the morning and conditions aren't too crappy, it'll use solar to heat up the geyser.

 

8 hours ago, system32 said:

Your diagram is not detailed enough in terms of how the non-essential / excluded loads loads are connected.
There are two ways to connect "excluded loads" - the ACout2 or the ACin1.

Yeah I see how my diagram was oversimplified. So I have my pool pump and one 12,000BTU aircon on non-essential with everything else (other than the excluded loads I mentioned) on critical loads. I'll have a look at my inverter to investigate how the non-essential/excluded loads are connected. My sense is that my non-essentials are likely connected to the "ACout2" as they are powered by PV/battery provided the grid is up but will make sure. I imagine, as you say, that my excluded loads are connected on the "ACin1" side.

 

8 hours ago, system32 said:

Just use timers to ensure that geysers come on during sunlight hours.

I was considering a "both" solution where I've reduced the elements' kW draw by replacing them and including them into non-essential loads AND utilising a timer to control when the geysers are on/off. Again, the main motivation is to bring as many viable loads as possible over to utilise a higher % of the latent capacity.

 

8 hours ago, system32 said:

I've used a "kill-a-watt" meter (~R500) and then upgraded to "tasmota/tuya" smart power plugs.

Have seen the "Kill-a-watt" mentioned here and there. I had hoped to have had the EM24 installed as that would've given me a better sense of what my "excluded loads" are doing from a power consumption POV, similar to what I expect the kill-a-watt would.

 

Thanks again for sharing your thoughts/tips–lots to consider and digest and a few immediately actionable tips in there too. Cheers!

 

@Bigawattremember that loads connected to ACin1 can also benefit from Solar - you need a CT clamp/EM24 meter for the PowerAssist/PowerControl function to work.