The Truth about going Solar

My one year milestone is coming up and I thought it would be valuable to write up my experiences about going solar.

Before we get started, let's address a few easy misconceptions:

• A small to moderate size system will take you off-grid: ?
• The system will manage itself and maximize its yield: ?
• A 5kVA inverter is enough for your entire home: ?
• There won't be any issues: ? if you're lucky, otherwise: ?

Don't get me wrong here, I'm not a nay-sayer for going solar. I'd just like to share my honest thoughts and experiences to better prepare people for what lies ahead. I'll address each of these points later ??

?? HOLD UP ?? Ensure you've read and understood my Disclaimers at the bottom ??

Terminology

There will be terms used in this article that a lot of people won't understand. If you have a general understanding of electricity, skip forward ?? Or just refer back if something doesn't make sense later.

Please research terms not listed by searching: "define: <term>". E.g. define: kVA

• V | Volt(s) | Voltage -- Electric potential difference. Let's work with the classic river analogy: This is how fast the water can potentially flow when the flood gates are opened.
• A | Amp(s) | Ampere | Current -- An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. Back to the river analogy: This is how wide the river banks are (e.g. how much volume the river can carry).
• W | Watt(s) | Power -- This one is probably the most useful and you should have some understanding of this already as appliances are commonly marked with a Watt rating. It's an easy way to reason about power consumption over time. E.g. A 3000W electric heater will consume 3000 Watts of energy every hour. Therefore, your prepaid meter will reduce by 3 units every hour (aka kWh ??) if the heater is continuously running. Back to the river analogy: This is how much water passes the flood gates over time. Calculated by (Voltage × Ampere) aka (how fast × how wide).
• kWh | Kilowatt Hour(s) -- Basically how many Kilowatts (W ÷ 1000) every hour. Back to the river analogy: This is how much water passed the flood gates every hour.
• DC | Direct Current -- A one way directional flow of Current. Solar panels and batteries are good examples of DC power sources. Back to the river analogy: This is the direction the water is travelling.
• AC | Alternating Current -- Current flow that periodically changes direction. Utility supply is AC 220V or 110V at 50Hz. Check with your supplier. Boop. Our river analogy breaks down here. But, work with me for a second. Imagine the water freezes and there is zero friction at the banks. Now, the frozen water moves a little forward then a little backwards... 50 times a second ?? ? hopefully as a pure sine wave ?.
• Inverter -- A device that can convert between AC and DC. For solar installations this will be the heart of your system. Everything will be connected to this device. Power sources (aka Inputs): Grid, Generators, Solar, Batteries, Wind, etc. Power consumers (aka Outputs): House, Batteries, Car, etc.
• PV | Photovoltaic -- You'll see this come up a lot. Installers generally assume you know what they're talking about. They say stuff like: "We can install your PV system on Tuesday." "The live PV lines come here and connect into this breaker." Basically, they're referring to the Solar / Panel system that collects Photons and converts them into a Voltage potential / Current.

??Understanding of these few terms will get you 99% of the way. Let's make it concrete by example:

You have a 2.4kWh battery, it's nominal discharge Voltage is 48V. How long can we power a 3000W electric heater from this battery? PS: Don't do this practice, it's only an example.

# Convert W to kWh
    3000W / 1000 = 3kWh

# Get total time the battery can keep the heater running
    2.4kWh / 3kWh = 0.8 hours

# Convert to minutes
    0.8 hours * 60 minutes = 48 minutes

Therefore the heater will run for 48 minutes.


# Let's calculate how much Amps the heater will need to pull at 48V
    3000W / 48V = 62.5A

Ooohf, that's a lot of Amps! Now let's do it properly
by connecting an Inverter.

# Inverter takes DC 48V converts into AC 230V.
# Let's recalculate Amps
    3000W / 230V = 13A

Muuuuch better. HOLD UP?!? Does the heater still
run for 48 minutes at 230V ??? YES, this is why
reasoning in Power / Watts / kWh is so great.

Hopefully this example shows you how useful the W or kWh notion is. The battery will last 48 minutes regardless of the what the output Voltage (and therefore Current) was. *Just keep in mind nothing is 100% efficient, there are always small amounts of losses in conversion and transmission. I'm just explaining in simple form.

My Journey ??

Overview ??

15x 340W CNBM Mono Solar Panels
4x  2.4kWh LiFePO4 Dyness Batteries

1x  Victron MPPT 250/100 Solar Charger
1x  Victron Quattro 48/10000/140-2x100 Inverter
1x  Victron Color Controller (aka CCGX)
1x  Victron Lynx Power In, DC Distribution bus bar

The last year's consumption stats:

The high-level journey:

Extrapolating Feb 2021 to what Feb 2020 would have been, you'll notice a big difference. My system is functioning way more efficiently than before. This is no easy feat as it pretty much requires you micro manage all aspects of power consumption. The barrier to entry is quite high here. I think the common misconception is that you'll add solar to your home and magically all your power needs are met. More on this later ??

The Issues Phase ??

Along the way I also had a few issues that were beyond my control (or my installer). The fact that we were in the middle of a lockdown also didn't help.

The faulty battery was by far the most puzzling one. It required close observation and good understanding to know / figure out what was going wrong. It took months of hardship and loads of research. In the end it required me to sit and watch the physical SOC (State of Charge) lights on the batteries to understand the fault.

Each battery reports its DCL (Discharge Current Limit) aka, how many Amps each battery can supply safely.

This screenshot shows that currently the Inverter can pull 120A - That's 30A for each battery. Now, the faulty one reported ?? ready ?? to go. But when the time came, it didn't chip in, causing the other 3 to discharge at 40A each ?? exceeding their limits. Luckily these batteries each have a BMS (Battery Management System) built in. They'll quickly cut operation when boundaries are exceeded. In such an event, the Inverter will switch to Grid power or trip if no other source is available.

Next issue was Voltage reading miss-match on the MPPT vs the BMS:

Closer inspection shows the fuse didn't burn through, rather started burning / melting at the one contact point. This was due to a bolt not being fastened properly on the DC bus bar. ???♂?

There is a lesson in here somewhere, I can feel it. ??

Luckily, EASY fix once identified.

From this point my system has been running as intended! Ultra happy with everything. From here I could start optimizing and we were going into ?? summer ??.

The Optimizations Phase ??

I've achieved ~85% off-grid by:

• Reducing usage and increasing efficiency. Think power saving lights, LED downlights, digital inverter appliances (e.g. fridges, aircons), properly insulated hot water tank, etc. This must ALWAYS be the first step. Swap out the easy things like lights first; larger appliances as and when necessary. Turn the hot water supply temperature down to 50℃ -- This will make a HUGE difference -- Your skin will register "too hot to touch" at ~45℃. This alone reduced my hot water power consumption from ~215kWh to ~100kWh per month. That's a ~50% reduction going from 65℃ to 50℃. ?? AND I still need to add some cold water while showering!
• Running large power consumers during the day. E.g. Dishwasher, Geysers (aka Boilers), Heat Pump, Pool Pump, Oven, Air Conditioners, etc.
• Home Automation. This is a biggy and totally optional, but I believe it's the only true way to utilize your system fully. Using a fully integrated system allows me to scale my power consumption alongside power generation. E.g. Running the Pool Heat Pump only when I have excess energy. My utility supplier (Eskom) doesn't allow selling back onto the grid, so this the only way ensure the solar power isn't curtailed (fancy word for "wasted") when the batteries are full. ?? I might do a full article on this topic, drop a comment if you'd like to see that in the future.

Ok, Ok, I hear you. Why not just add MORE batteries? Sure, have you seen battery prices? They'll be of one the most expensive parts of your system with the shortest lifespan ??. My initial idea was to hold out a bit longer until better & cheaper means of energy storage becomes available. But, in the end, the whole system becomes less useful and efficient without enough storage. That's why I decided to add 2 more batteries shortly after my initial installation. PS: I'd need about 24kWh storage to cover my needs ??, that's 10x 2.4kWh. ?? See below what adding 2 more cost me.

The Cost ??

I'm in Cape Town, South Africa ????, so this will all be in R (Rand) and rounded to the nearest thousand.

Initial Parts + Installation
----------------------------

12x Panels
R33k

Inverter + MPPT + CCGX + Wifi + Cables
R84k

2x Batteries + Cabinet
R42k

Consumables
R21k

Labour
R25k

------------
Total: R210k
------------


Upgrade - Add 2x Batteries (self installed)
-------------------------------------------

2x Batteries
R30k

Cabinet
R2k

-----------
Total: R32k
-----------


Upgrade - Add 3x Panels + odds and ends
---------------------------------------

3x Panels
R7k

Labour + Consumables
R17k

City Council Registration
R5k

-----------
Total: R29k
-----------


------------------
Grand Total: R271k
------------------

In South Africa ????, our utility supply undergoes regular Load Shedding (they shed load from the grid as Eskom can't supply enough power to meet demand). HOWEVER, my system makes me immune to Eskom failure / load shedding!! Price of that!? Priceless of course!

Having electricity while there are rolling blackouts means I can still do my job or sleep comfortably as my air conditioner still operates. You can't put a price on that. It's unfortunate that our beautiful country is in this state. I don't see it getting any better any time soon. ??

I've also saved R17k on my electricity bill over the last year, but this is just an added bonus for me. Knowing that I'm contributing much less CO2 to the atmosphere ??, priceless of course! South Africa ???? mainly runs on dirty-dirty-wet charcoal.

Your Journey ??

The Research Phase ??

I'm guessing this is where you are right now (?? welcome, I hope you find this informative). Below are a few questions you need to think about.

What are you trying to achieve with your system?

Fully Off-grid? Partially Off-grid? Backup power in case of blackouts? Save on electricity bill? Decrease carbon foot print? ?? All of them?

Obviously, this all depends on how deep your pockets are, what subsidies are available in your area, what the local regulations are, what brand of devices you choose, how integrated / modular the parts are, etc. I'd suggest speaking with a local installer (or two) to get a general sense of your local situation. Really think about what you want and how much on-going effort you'd like to put in. Set and forget? Tinker and optimize? Telling the installer what you'd like to achieve is a great first step. They'll be able to guide you from there.

I'm a software engineer by trade, I love technical things. Telemetry and the ability to tinker is important to me. This one of the reasons why I decided to go with Victron Energy. They also seem to be the industry leaders, based on my research and what installers are telling me. Think Rolls-Royce of solar equipment. Naturally they are more expensive, but you know what you're getting, the price tag gives you quality and experience. These are long term decisions; I'd rather fork out a little extra now and be guaranteed the company will be around in 20 years' time when I need support.

What size system should you install?

A good place to start is to look at your current consumption. Get your monthly kWh usage from your utility bill or if you have a prepaid meter, well, you know how much you need to load each month.

Let's use my numbers as example:

1080kWh per month / 30 days = 36kWh per day

36kWh per day / 24 hours = 1.5kWh per hour

Ok, simple enough. The two important ones are your daily usage and hourly average.

>> Inverter <<

The Inverter's job is to aggregate all power inputs and output. You need choose whether you'd like your entire house on the system or just critical loads connected to the system. The Inverter has maximum capacity, it puts a very hard limit on your power draw on the connected circuits.

Badly designed example (DON'T DO THIS):

Your entire house is connected to a 3kVA Inverter ???♂?.
The Inverter has a continuous power output of 3000W
and peak output of 6000W.

You switch on the microwave ??; it draws 1600W.
Ok, all is still fine. What you don't realize is
that the electric geyser in the ceiling also decided
it's time to heat the water ??. It draws 3200W,
putting us at 4800W. ?? What happens now? ??

Well, the Inverter will try its best to maintain 4800W,
but will only manage a few seconds ??. It will break the
circuit and cut the power ??.

What's the lesson here? It doesn't matter if the grid is connected or not. The Inverter has reached its output capacity. Thus you can't use more than that, period.

How do we fix/avoid this example? ?? Here are some things you can expect from the power rating ??. By no means set in stone, speak with your installer!!

?? Residential homes in ???? generally have a 60A limit. Your breaker will trip if you exceed it. That's 60A x 230V = 13800W. Nice.

• 3kVA - One critical load circuit (e.g. fridge, internet, computer, TV) and maybe the power efficient/emergency lights. This circuit should not run any long running high consumers, like electric heaters, kettles, etc. It also should be clearly marked. You should not exceed 3000W of continuous power draw in total.
• 5kVA - Two/Three critical load circuits and lights. Nice medium sized system, but I think it falls prey to "almost big enough". I'd be very disappointed spending that much money and only getting 80% of the way. Would not recommend for entire house connection.
• 8kVA - Depending on your power consumption, you could put your entire house on this system. It's still a little on the low side, but with smart management you could make it work. I'd recommend putting your water heater on non-critical circuit, it's always the surprise high load. Using the oven (3200W), kettle (3000W) and toaster (3000W) at the same time will also overload the system. Keep in mind that your fridges, pool pump, computers, etc. might also be running. That all said, 8kVA is a very good option.
• 10kVA and up - No compromises system. I opted for this size and haven't had a single overload trip event ??. I've also exceeded 10kW on numerous occasions. It's a testament to the quality of the Victron products. Their inverters can deliver a peak output of 2x their rating ??.

?? Inverter capacity reduces depending on the ambient temperature! Check the data sheets!

?? That's a lot to digest, I know, but choosing what you'd like to achieve and what Inverter you want is the most important part!

>> Batteries <<

This is where it gets hairy. Technically, you should scale your battery bank with your Inverter, depending on what you want to achieve with your system.

This also adds a hard Capacity limit, much like the Inverter limit -- but -- only when you're not connected to the grid / collecting enough Solar power. Remember, the Inverter will trip in any scenario where the requested load can't be satisfied.

Inverter: Can I satisfy load?
  -> Requested load: 6000W

Solar yield? 600W
  -> Remaining load: 5400W

Battery max discharge: 2400W
  -> Remaining load: 3000W

Grid status? N/A
  -> Remaining load: 3000W

!! 3000W not satisfied !!

>>>>>>> ?? Trip ?? <<<<<<<
  

Also keep in mind that a cloud ?? could pass overhead at any moment, making a serious drop in power supply. The Inverter uses the Batteries and Grid to smooth this out, but only if it can.

My suggestion here is try and cover at least half of your Inverter capacity or about a third of your daily usage (e.g. 36kWh ÷ 3 = 12kWh). More would definitely be better. It will also require less smart management / optimizations to utilize it efficiently at all times.

>> Panels + MPPT <<

What's this MPPT (Maximum Power Point Tracking, aka Solar Charger)? It smartly manages the panels to maximize yield and efficiently charge the batteries.

Angle & Orientation - Identify the suitable location on your roof by looking on Google Maps which sloped roof section is pointing towards the equator, i.e. pointing South for the Northern hemisphere and North for the Southern hemisphere. There is an optimal angle the panels should be placed at based on how far north or south you are. See Solar Angle Calculator and input your location - this screenshot is for Cape Town. Your installer should advise you on this, as every roof is unique. Try and strive for the Spring/Autumn angle.

Roof space & Shade - Realistically, how much usable space is there on the roof? How shady is it? Take photos of the target roof at (sunrise + 2 hours), noon and (sunset ? 2 hours). Compare shadows at each extreme to estimate how shady the area is. This might seem obvious, but shadows really kill off PV productivity. Avoid as much as possible.

Back to size calculations, panels are generally 2x1 meters in size. Now, do some back of the napkin maths to calculate the available usable space.

How many panels can fit side by side?
  -> roof-width / panel-width = columns

How many panels can fit top to tail?
  -> roof-height / panel-height = rows

What's the total?
  -> columns * rows = total

Just make sure to bring your estimate back into the real world! There will be gaps in-between panels. You can't place them edge to edge on the roof, there could be other obstructions and/or restrictions, etc.

Mono vs Poly - This is the type of crystal the PV is manufactured with. Basically, Mono = more efficient and more expensive. Poly = less efficient and less expensive. Nowadays it seems to be much of a muchness. If you're constrained for roof space, go Mono. If not, consider either.

Finalize by calculating MPPT size - At this point you should have a good sense of how many panels you can realistically place on your roof, but might still be undecided on the crystal type to get.

See Victron's MPPT calculator. The important thing here is that you get your panel count by multiplying Series by Parallel (5 × 3 = 15). Once inputted, you get the forecasted kWh estimation graph. I can tell you this estimation is very accurate, my system out performs this by only ~5kWh as my peak yield in Dec/Jan was 34kWh per day. That's pretty close!

Unsure about Battery and System Voltage? Just use what I inputted. Your installer will redo all of this with proper values based on what panels/batteries are available. Also, it doesn't affect the kWh estimation we wanted.

>> Bring it all together <<

Ok, now here's the bit where you tie this all together. Hopefully all this information can help you decide what's theoretically possible for your home and align your expectations to reality. So if you consume 40kWh a day and you can only produce 20kWh, don't expect to go off-grid or buy a huge battery bank.

The Action Phase ??

Armed with a better understanding, it's time to phone your local solar installer, have a conversation. Let them work out a quote, maybe arrange a site inspection, etc. Make sure to double check what they are saying. I've heard of horror stories of panels fixed away from the equator ???♂? or people having completely unrealistic expectations and being disappointed after spending loads of cash ??. Ensure they follow local regulations!

Disclaimers ???♂?

• I am not a qualified electrician. Please consult qualified professionals before attempting to do anything yourself. Electricity is dangerous, always proceed with caution and safety first.
• I live in ?? sunny (and windy) Cape Town, South Africa -- your solar yield will vary. South Africa's power supplier Eskom supplies 230V at 50Hz AC for single phase. This is common for standard residential households.
• Photos may or may not be showing proper warning stickers or have completed wiring -- please be rest assured, all earth leakage and warning stickers are in place in finalized setup.
• All products and brands shown were my personal choices, no sponsorships or endorsements.
• I cannot be held liable for any damage/harm resulting from advice given here.

Closing ??

Thanks for reading! ? I know it turned out a bit long, but I hope it provided some insight and simplicity into this complex world of solar power.

If you have experience, please leave a comment and feel free to point out where I have things incorrect ??.

Till next time ??