I will build a solar system on my roof in an unusual way.
Together with my neighbors and supported by young enthusiasts who had an excellent idea.
This video will focus on the choices and implications you have for building such a system.
In the end, we get an answer to GreatScott's question: DIY or Buy.
Grüezi YouTubers.
Here is the guy with the Swiss accent.
With a new episode and fresh ideas around sensors and microcontrollers.
Remember: If you subscribe, you will always sit in the first row.
Recently, energy has become more critical.
The “decarbonization” Megatrend was joined by the war in Ukraine, the higher demand after
Corona, and the e-mobility trend.
This is why my long-term wish was catapulted to my #1 priority: Solar panels on the roof
of our house and a battery in my basement.
We live in a small townhouse with a flat roof.
I always feared that I would destroy its sealing by adding solar panels.
This was the main reason for shifting the project year after year.
So I will start with this topic.
Then I will cover two ways of mounting the panels: South or east-west.
Next, I will cover the inverter and the battery in my basement.
Then I will tell you a few things about optimizers the manufacturers do not tell you.
And finally, I will talk about cost.
But let’s start with the most important decision: How I will build my project.
It all started with a newspaper article: “Boom in Basel: Homeowners build their own solar
systems.”
That caught my attention because it was exactly what I wanted: Building my DIY solar system
but profiting from the know-how of others to reduce the risk.
As you know: I love to stand on the shoulders of giants to reach my goals.
The next idea was born at the same moment: I will try to convince my neighbors!
To get good arguments, I used an offer from our local electricity supplier: Comparing
three offers from professional companies for my solar system.
I hoped this would give me reasons why do-it-yourself is a good idea.
So said and done: I got the three offers, and we will learn with them.
But what about the potential destruction of the roof?
All three offers included mounting systems from K2, a German company.
They are only laid out on the roof.
No screws or anything to tie them to the building.
Very good!
Like that they should not harm our roof.
But what about the wind?
They use a simple trick: Adding weight, as you see in the manufacturer's video.
So my biggest concern was removed, and I went on with the comparison.
Here is the overview of the three offers from a technical perspective.
Two suppliers offer around 6kW peak, and one offers 9kW peak.
What does this mean, and why the big difference?
kW peak is the maximum power a solar cell can produce.
Here is the datasheet of a typical module.
The nominal output power at 1000W/m2 solar irradiance is 450 watts at 41.39 volts and
10.88 amperes.
If open, the module delivers 50.1 volts.
And if shorted, it delivers 11.48A.
This is the typical behavior of solar panels discussed in video #142.
An MPP Tracker must adjust the current and voltage for maximum power.
We will discuss these trackers later.
Because of the standard measuring conditions, we can use kW peak for a cost comparison,
not for the overall performance.
As we will see, the produced power per year is influenced by other parameters, too.
If we have a closer look at the three offers, we see that their arrangement is different:
One setup has gaps between the panels, and the other does not.
What is the reason for that?
This is direction south.
If we mount panels like that and at an angle of 37 degrees, they provide the maximum overall
power per m2 panel surface.
Why do I know?
I used this page for simulation.
I entered my data and asked for an optimized slope.
I always use 1kW peak for our comparison, and this configuration provides 1.1kWh per
year.
This arrangement was used in the past because they wanted to get the most out of their expensive
panels.
But unfortunately, panels mounted at such an angle also create a shadow.
This is the reason for the gaps.
Nobody wants to mount panels in the shadow, right?
The other two suppliers chose a different concept: They mount the panels east-west and
at a slope of 10 degrees.
Clearly, this is not optimal and creates reduced maximum power per panel.
The east orientation at 10 degrees provides only 950Wh.
And the western panels even less.
But because we need nearly no gaps, we will get more power for the whole roof.
Because solar panels became much cheaper, optimizing the roof performance instead of
the panel performance became possible.
We see another effect: The power varies between summer and winter.
If we had the chance to add a few panels to the front of the building, it would help in
winter.
After this discussion, a question emerges: Does the company with the “old” setup
not know these facts?
I assume they know.
But there is a second reason we have to consider: In German, we call it “Eigenverbrauch,”
translated as “own consumption.”
Because we also consume electricity during the night or on days without sun, we still
have to purchase electricity from our provider.
And we sell excess energy produced during hot summer days to them.
Unfortunately, they pay much less for the power they buy than we have to pay for the
energy we consume.
A stupid concept, in my opinion, if you want to motivate homeowners to invest.
But this is the case in most countries.
This is why it is best if you can use your own electricity, and the optimum payback period
usually is not reached with the biggest panel area.
People focused on payback do not install maximum power but smaller-sized systems.
This is probably what the guys with the smaller area had in mind.
I will not join this discussion for two reasons: First, we need a lot of energy, and second,
these calculations are made with the current energy prices in mind.
Solar panels will live 25 years, and these calculations heavily depend on the price difference
created by the energy supplier.
I definitively will go for maximum power for the roof, which means more peak power, east-west
orientation, and more investment in solar panels.
But you will see that the price of solar panels is not so important.
So we already covered the risk of water entering our home and the proper orientation of the
panels.
Now we have to talk about the installation in the basement.
Our system will be integrated into the grid.
This is why the inverter has to be approved by the electricity company.
So I decided to buy a ready-made device instead of creating my own.
But what is the function of this inverter?
As we saw before, solar panels provide DC.
And our homes run on 3 phase AC.
So let’s look at the block diagram of such an inverter.
It has two inputs and two MPP trackers.
Why two?
The eastern panels will get more sun in the morning, and the western panels will get more
in the evening.
This is why the “maximum point” will be different for the eastern and the western
string.
The panels in one string will behave very similarly, BTW.
Later we will see that this is not always the case and what can be done against it.
So we will create two strings and attach them to the two MPP trackers.
Also, after the trackers, we have DC.
This is why a battery can be connected here.
Next, DC must be converted into 3-phase AC at 240 volts.
Do not think this is easy.
Because the grid is still connected to our home, the inverter has to synchronize its
frequency and phase before joining the net.
And it has to manage the current inserted into the network according to the sun.
And it has to manage the battery.
And it has to switch to an off-grid scenario during a power outage.
And switch back if power comes again.
And provide information to my home automation system for statistics.
You see, this is a mastermind.
And you see something essential for Radio operators: Everywhere filters.
Because these devices have fast switches, they could easily emit signals which interfere
with your radios.
And, as we will later see, they do if you make wrong decisions.
This leads us to the next topic: Optimizers.
I said before that all panels heading to the east have the same MPP at a given time because
they get the same illumination.
What if we had a big chimney providing shadow to only one panel?
That would not be good.
All panels of one string are in series, and therefore they have to carry the same current.
If one panel is in the shadow, it will limit the current for the whole string.
Not what we want.
This is why panels have diodes to“bypass” the current in this situation.
So the panel in the shadow does not provide energy but does not prohibit the others from
doing so.
There is even a better solution: Optimizers.
These DC-to-DC converters attached to each solar panel align the current to the string
current by reducing the voltage.
Like that, you always get the best performance out of a shaded panel.
Sounds good.
But unfortunately has some disadvantages you better know before you decide.
First, they have to operate in a hot environment directly below the panels.
This is why their life span is short.
Second, you usually need more than one, which increases the risk of the early death of one
optimizer.
Some suppliers even try to sell you on buying an optimizer for each panel.
Third, they are not easy to replace because they are on the roof, and often you have to
pay a specialist to come to your home and on your roof.
And fourth: If they are made cheaply, they create a lot of interference.
Devices produced by SolarEdge are famous for that.
Fortunately, I do not need them because I have no significant shadow on my roof.
Now we have all together.
But wait, I forgot something: The optional battery.
Optional because grid systems do not need one.
And if you do your calculations, it usually is hard to justify the extra cost.
A payback is possible if you can increase your own consumption by transferring excess
energy produced during the day to the night.
Like that, you buy less expensive energy and sell less cheap energy to your provider.
I wanted one and did not care too much about the payback.
You remember: My scenario is that we will have higher electricity cost in the future.
And I am a curious man, always interested in new things.
But I also do not like too much risk.
So I ordered a LiFePo4 battery that does not explode or burn quickly.
Please pay attention when you select your inverter.
Not all provide off-grid functionality.
And most only for one phase.
Now let's have a look at the cost.
Be aware that I live in Switzerland and your cost might be very different.
This is why I will not focus on the amounts but on cost components and their relations.
All costs are in Swiss Franc, which is close to a dollar or a Euro.
If we go back to the comparison chart, we see three numbers:
1.
The overall investment, which includes parts and works
2.
The investment after the deductions of investment help from the government or tax savings
3.
The investment per kW peak is an excellent way to compare offers.
We see that I would end with 2-3k CHF per kW peak.
The bigger system is cheaper.
Which is an indication of fixed cost.
So let’s have a look at the cost distribution.
There are three main parts: - Material costs, including panels, the inverter,
and the optional battery - Work to mount the panels and the inverter
- Planning and acceptance work.
We need an official “stamp” that everything is ok to switch it on as well as to get the
government money The best commercial offer has a material cost
of 14k, work of 10k, and planning and acceptance of 4k, which gives a total of 28k plus 7.7
VAT=30k The solar panels alone are around 5k or 16%.
So you see why I said it is best to mount as many as possible.
The fixed or step cost is immense!
If I had ordered this system, I could go on holiday during the installation.
Now comes the ultimate question: How does the DIY variant compare?
A bit of background: The cooperative I chose was founded by a young guy who wanted to help
reduce CO2.
It is already big and has helped to install more than 500 systems.
It provides know-how for planning and installation, the needed material, some specialized tools,
and the overall coordination work with the authorities, which is not easy where I live.
So let's compare their offer to the best commercial one: 13k for the material.
This is comparable but contains a 10kWh battery for 4.5k CHF.
Comparing apples with apples, the saving in material costs is 40%.
Cool!
This is the result of the good prices they get because they can buy in large quantities.
And because they are a non-profit organization.
And what about the work?
Here we should see the biggest difference because we have to work a lot.
After all, the project is DIY!
3.5k compared to 10k.
As expected, I would say because we need scaffolding and electrical installations which we cannot
do.
The planning and acceptance cost is 5.4k.
A little higher.
So we have a total of 22k, including a battery.
The solar panels alone are 3k, BTW.
The installed peak power is comparable: 9 and 8.6kW.
Up till now, I only compared my installation.
Fortunately, I convinced three of my neighbors to come along with me.
Because our first meeting was when the war in Ukraine started, the talking became a bit
easier for me.
Also, doing it together should reduce the fixed cost, and it is more fun.
So which components can you expect in the build?
As said: We will use the K2 mounting system.
The huge solar panels are from the German company Axitec.
They measure 209 x 104 cm and weigh nearly 25kg.
And they use the innovative “Half-Cut-Technology,” which seems to provide the best bang for the
buck.
The SUN2000-8KTL-M1 inverter and the LUNA2000-10-S0 battery are from Huawei.
Because they showed lots of filters in their block diagram, I trust that they know what
they do in this respect.
That is one reason why I chose them.
The second reason is that their battery uses LiFePo4 cells and works together as a system.
Now you know the setup.
Currently, we are waiting for the material to arrive.
Getting the material was not easy.
I will keep you updated with a second video where you should be able to watch our progress.
The drone is already waiting for its next flight.
So stay tuned and comment if you like the idea of a second video!
As always, you find all the relevant links in the description.
I hope this video was useful or at least interesting for you.
If true, please consider supporting the channel to secure its future existence.
Thank you!
Bye