﻿How can we protect our wallets against rising energy prices and our homes against power outages?
In this video, I will show you things you better know before signing a contract for
a new PV system. Because not everything is as it looks, and your solar salesman probably will not
tell you. Or you find ideas to improve your installation? Please come with me on this journey
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.
In May, we started to build four PV systems on our roofs. You find links to the two videos
about the project in the video description. This video is a continuation; you may want to
watch the two others before continuing. Before the summer break, I left you with
unconnected solar panels, a pregnant neighbor, many empty beer bottles, and a to-do list.
So, first things first: We now have one more energy consumer because our neighbor’s girl
was born. And yes, all connections on the roof were okay, and the panels produced
the anticipated voltages. So we can go on with the installation in the basement.
In this episode - We will do the installation as well as the
connection to the grid and switch the power on - Then I will show you the first results of the
production and the influence of the batteries - To understand why my Shelly power meter started
to display weird values when we switched the solar power on, we have to deep-dive
into how inverters work and interact with the grid. It is pretty different than you
think. Unfortunately, not only good news - If you stay till the end, I will reveal
the status of our neighbor’s as well as of my brother’s solar plant and what we will do next
So a lot of content. Let’s continue in the basement.
As you know, we decided on a Huawei SUN2000 inverter with a LUNA2000 battery.
Fortunately, both are passively cooled and have no fan. Their efficiency is around 98%,
and the wasted 2% produce heat. So each kWh managed by this installation creates 20Wh of heat!
That is why they must be mounted at specific distances from the ceiling and surrounding walls.
As you will later see, we were fortunate that we got all the needed parts in time and could finish
the installation. The cabling is quite simple: The two solar strings from the roof are connected to
the two inputs of the MPP trackers. Currently, I have two batteries with a total capacity
of 10kWh. They have to be connected to the control unit. These are high volt batteries. Together they
produce roughly 800 volts, 33 times more than a usual 24-volt setup. This is good because the
higher the voltage, the lower the currents and the higher the efficiency. The same effect is used in
power grids, which use extremely high voltages to minimize losses. For me, this was a deciding
factor in selecting my inverter and battery. The battery control unit is connected to the
inverter and uses Modbus for communication. The output of the inverter is connected
to the fuse box. Because we have three phases, we need four wires for that.
The grid and the load were already connected, and the output of the inverter is just added
to this junction. Simple! Later we will see that this connection has severe implications.
Now we could switch the inverter and the battery on, and it would produce energy and feed it into
our home or even back to the grid. But we forgot a small thing: Here, we have to pay much more than
we get if we sell one kWh. That is why we want to use as much energy as possible in our homes
and only sell the excess energy. This is also one reason for the battery. To do so, the inverter has
to know if it has excess energy to charge the battery or to sell. But how can it decide this?
It has the information on how much solar power it feeds to the fuse box but has no idea if this is
used in the home or if it flows back to the grid. The utility company replaced the old energy meter
to get precisely this information. But we only will get their information on the next invoice.
In addition, their meter is in a different room. So we have to install a power meter and connect
it via Modbus to the inverter. We will talk about Modbus when we hack the data traffic
of the inverter in a future video, BTW. This ”Smart Meter” is connected to all
three phases between our home and the grid and measures voltage and current.
Precisely as my trusted Shelly 3eM, which I used to measure the consumption of our home.
Because they are installed in parallel, they should measure the same values.
Sebastian already applied the relevant parameters using the FusionSolar app
on his Smartphone. He also selected the“Maximize self consumption” strategy, which ensures that we
only sell energy when the battery is full, and we have excess solar power. He also selected
that the battery will be charged up to 95% and not discharged below 10% to extend its life.
So the task of the inverter seems to be simple: It has to measure the grid power and adjust the
battery charging or discharging to make sure that no energy flows from or to the grid for as long as
possible. With a charged battery, we would expect that this is true during the night,
and the Shelly should show zero watts. During the day, it should show the energy we sell to
the utility company. But look at its values: They are not at all zero during the night.
And some are even negative. Strange! Very strange! We only get the expected zero value when we sum up
all three phases. But with some unexpected peaks. What happens here, and why is this important?
Like many others, my inverter uses a trick: It produces the same amount of energy on all three
phases and uses the grid as short-term storage. This is possible because my utility company only
charges for the sum of all three phases. And this is mostly zero, as we saw before. So I should not
get an invoice apart from the short peaks. But why do we get those peaks? The inverter always has to
monitor all values. If a heavy load is switched on or a cloud starts to cover the sun, its controller
has to adjust the battery charging or discharging to an average value that the grid energy is
zero again. This takes its time. But because the grid has a lot of power, we hardly see a voltage
fluctuation in our home. I assume we will see a few cents for these peaks on our energy bill.
In a later video, we will see the implications of this design for the off-grid situation.
Do all inverters behave like that? I do not know because most inverter manufacturers do
not openly communicate such behavior, and it took me a while to find out.
What about your inverter? Do you know? What are the implications for my Shelly 3eM?
It mainly became useless. Before Solar was switched on, it showed the consumption on
the three phases, indicating which floor or room the energy was used.
Now its values are no longer related to the load, and I can remove or repurpose it.
The next plan was to mount an optimizer under one panel, which gets a shadow from the exhaust pipes.
I explained how optimizers work in my first video. Other than Solar Edge,
Huawei allows single optimizers, and you do not need to install optimizers below
every panel. The Huawei optimizers use the string cable for communication and are easily discovered
by the inverter—a promising concept in my eyes. But shit happens: Because we mounted the
optimizer in the evening and did not think too much, we mounted it behind the exhaust.
The other morning I discovered that the shadow traveled across a different panel.
Because I had to leave for my Route 66 Harley tour, it stayed there for a few weeks.
I am very comfortable because I have a second installation with nearly the same constellation on
the roof of my neighbor Hugo. The only difference is that he has one panel more in the east string,
and I have one more in the west string. If we compare the output power, we see that Hugo gets
more power in the morning, and I get more in the afternoon. So how can we compare the two to find
out about the influence of the optimizer? If we go to the data sheet of the solar panels, we see that
the current is proportional to the solar power. The current is always the same in one string,
independent of the number of panels. So we just have to compare the current instead of the power.
Let’s look if this is true: Indeed, the curves fit very well. There is a time difference because
I read the values every 30 seconds and not precisely at the same time. But the rest is
pretty much the same. What about the time around 9 AM, when one of my panels gets the shadow?
No noticeable difference here, too. So, do I need an optimizer as suggested by the industry!
It seems that small shadows do not hurt much. Optimizers everywhere would hurt much more
because they have an efficiency of 98% and permanently lose 2% of the entire plant.
Fortunately, I have other plans for the optimizer. So stay tuned.
Everything is in place and understood by now. Nearly. Two questions are left: One question from
the last video was: Why do we have to follow all the panels with the negative cable and not connect
it like a battery? The answer is because of lighting. If connected like a battery, the panels
would create a large loop, creating a high voltage even if the lighting would strike somewhere in the
neighborhood. If we do the wiring as we did, this loop is tiny, and no voltage is induced.
The second question was: What happens if the grid is down? The law says that our inverter
has to be shut down in a fraction of a second, too, and we would not have power even if the sun
shines and the battery is full. Frustrating, isn’t it? Why does the government create such laws?
Are they mad? Or is this a plan of Bill Gates to take over the world power?
Let’s have a look at what happens during a grid down. All our homes in our street are connected
to the grid in parallel, right? And our street is connected to the village with many more homes in
parallel. This is why they use quite thick wires, BTW. And these wires have to become even thicker
if everybody wants to charge their cars at home… So let’s assume the grid does no more deliver
power to our street, but our brave solar plant still produces energy.
Because we are still connected to all other homes, it immediately would start to supply our whole
street and maybe even others. In a fraction of a second, our inverter would overload and
switch off. Without the influence of Bill Gates. Second case: Let’s assume workers need to do some
maintenance in our distribution room. To protect themselves, they cut the connection to the grid.
Now they can safely work on the installation. Not with our solar plant switched on:
It would reverse supply the net and possibly kill them. You see, this time, the law is good.
And we have to think a bit more to solve the off-grid problem. A small teaser: The backup
box is already here, but I fear we will need to dedicate an entire video to solve this issue.
Because as usual, we want more on this channel. My panels started to produce on May 24th in the
afternoon. The Huawei cloud service provides the graphics. It was a cloudy and rainy day,
and we did not get a lot of sun. Still, the battery started to charge. The red curve
shows our consumption. Other lines sometimes cover it. As soon as the battery was full,
we started to deliver power to the grid. Later, we used the washing machine and cooked a meal.
Both had to be powered by the battery because the sun could no longer deliver enough power.
We lived off the battery during the evening and finally went to bed.
The next day was quite sunny, and the battery charged fast.
At 10:40 AM, it was already full, and we started to sell electricity.
No cooking and washing in the evening, but obviously, I worked longer.
Already here, you see the influence of the battery. Because our consumption
is not where the production is, we would have sold nearly all the energy and repurchased it
in the evening and night. With the battery, we did not need to buy any expensive energy.
The rest of May was okay, and we could sell more than 200 kWh.
Peak production was 46.36kWh in one day. On 28th, I left for Route66, and my lab was switched off.
June was the first full month and we already crossed the 1MWh production!
Because we were away most of the time, we could sell 831.8kWh, nearly 80% of
the production. We only had to buy 1% from the grid because of the reasons I explained earlier.
The overall earning was 125 CHF. No, not Yuan. I just was not able to change the currency sign.
Here you see a perfect day: Full sun from 7 AM
to 8:30 PM. This was the best day up till now with 54.05kWh.
How does this compare with the installed peak power? My panels have a nominal 8.1kW peak.
So I got 6.67kWh/kWp. Similar values were reached on other days in July.
And the consumption? When we are at home, we consume around 12kWh per day in July. But keep
in mind: The days are long, and the nights are short. We will see how this works out in winter.
Summarized: - We finished up the installation on the roof,
installed an optimizer at the wrong place, removed it, and learned that it was not needed
- We installed the inverter, the battery, and a smart
meter and connected the inverter to the grid - Because my neighbor has a very similar setup,
we could see that the optimizer was not needed. In the future,
we can try to find other potential for optimization. For example, the influence
of cleaning of the panels on power production - Because the load, the grid, and the inverter
are connected in the fuse box, it is no more possible measuring the consumption with my
Shelly 3em. We have to be creative to do so - The power of the three phases shows weird
behavior. The explanation is that my inverter produces the same power on all phases and
uses the grid to buffer the differences - The chosen strategy “optimize our own
consumption” forces the inverter to not consume grid power as long as the battery is charged.
As soon as the battery is full and enough solar energy is available,
it starts to deliver power to the grid - As soon as the grid is down also, the
inverter has to switch off, and we have no power for our home even if the sun
shines and the battery is full - We produced more than 1MWh
till the end of June. Most of this energy was given to the electricity company.
Because we had to wait for the final inspection and the stamp on the papers
In future episodes, we will: - Hack the Huawei inverter,
transfer its data via node-red to influxDB and finally display it in Grafana
- “Harden” our home by enabling off-grid operation as well as hunting down the power consumption
to save money and extend the autarky - And finally, we will have a look at
uninterruptible power supplies, how they work, and why we need them
One last thing: What about the installation of my neighbor? Mid of July, he still did not have
solar panels on the roof. And my brother? His solar panels are ready. However, Solaredge was
not capable of delivering the inverter. So I am at nearly 2MWh ahead of the other two! And including
my neighbors, we fast approach the 10MWh mark. This was all for today.
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