Solar panels are hot! Due to the plunging prices
of solar panels in the last years, the allowance on solar
panels and
the ever increasing cost of electricity, thousands of
solar panel
systems are being installed on privately owned homes.
After reading a
lot on solar panels and calculating the break even point
(7 years in my
case) I made my decision: I want solar panels as well!
What is a solar panel?
A solar panel is a panel made from so-called photovoltaic
cells (better
known as solar cells). It are (in most caes) blue panels
that convert
energy in sunlight into electric energy. Solar panels are
available in
all different kinds of sizes and can be used for a lot of
purposes,
like parking meters. On this page I concentrate myself in
the use of
solar panels as a matter of private powersupply for homes.
Solar panels are mostly made from two different layers of
silicon.
Solar panels use sunlight or daylight and by absorbing of
photons in
the solar panels, a direct current of roughly 0.5 Volt
emerged. By
connecting different solar cells with each other, the
current becomes
higher.
The photovoltaic generates power is transformed to a 230 V
alternating
current by an inverter. The inverter is connected to the
electricity
grid in your home and van be used to power a refrigerator
or a TV. In
case more solar power is generated than what you need at a
certain
moment, the unused power flows back to the electricity
grid of your
supplier. This causes the electricity meter to run
backwards (unless it
is blocked to turn backwards). This means that no solar
power goes to
waste and that one can save extra on their electricity
bill.
The service life of a solar panel is estimated to be at
least 30 years.
Many manufacturers don't hesitate to guarantee a certain
production
capacity of their product for 25 years.
The hardware
What do you need for a solar power system to
generate solar power?
Solar panels
Many of the used solar panels in privately owned system
are so-called
crystalline panels. Crystalline panels come into two
different flavours
(mono crystalline and poly crystalline). Both types use
the same
physical principal to generate power, but the way they are
produced is
different.
Poly crystalline silicon and mono crystalline silicon are
both made
from the same raw material, silicon sand. In the process
of
solidification when making poly crystalline ingots, the
manufacturer
simply lets the fluid silicon solidify. The crystals are
disordered
when the ingots are ready. When manufacturing mono
crystalline ingots,
the manufacturer influences the way the crystals behave
when
solidifying so all the crystals are lined up in the same
direction. In
direct sunlight, a mono crystalline solar panel produces a
bit more
energy than a poly crystalline solar panel. In other
words: a solar
power system of a given capacity is a bit more "compact"
when it is
made from mono crystalline solar panels. Of course, mono
crystalline
solar panels are a bit more expensive than poly
crystalline solar
panels but the quality and guarantee given by the
manufacturer are the
same.
It is hard to report the best solar panels on this site. Panasonic
(Sanyo),
Sharp
and
SunPower
are well known. I used information on the internet from
people that own
a solar power system and based on that information and the
offers send
to me by companies, I made my choice.
Inverters
The electrical power that is produced by a solar panel is
a direct
current. Depending on the number and type of the panels
and the amount
of sunlight, the intensity of this direct current
variables. An
inverter converts this variable direct current into a 230
Volt
alternating current to be able to connect the solar power
system to the
electricity grid in your house.
Well known manufacturers of inverters are
SMA,
Delta,
Mastervolt,
Kostal,
Omnik
and
Steca.
As with the solar panels, I used a lot of information on
the internet
to pick my inverter.
The service life of an inverter is estimated to be 10 to
15 years.
Mounting systems
To mount solar panels on your roof, special mounting
systems are
developped. The mounting systems for sloped roofs in
general use hooks
that are being attached onto the roof underneath the roof
tiles. On
these hooks, special aluminium rails are attached that are
used to
mount the solar panels on the roof.
For a flat roof, special mounting systems are designed to
mount the
solar panels in a tilted position. The mounting system can
be made
heavier to provide the solar panels from being blown away
by the wind.
For the same reason, the rear side of this mounting system
is closed.
The most known brand is ClickFit,
but the
German brand Wasi
sells
a similair mounting system for solar panels.
Break-even point
An important fact in the decision to invest in your own
solar power
systems is the break-even point. This break-even point
depends on the
neccessary investment on the solar power system, the
expected output of
the system, the future price of electricity and the
expected life span
and corresponding future price of the new inverter. Next
to that, the
interest on savings, the way how you pay for the system
and the yearly
degredation of the solar panels also play their role. In
most cases,
the interest rates and yearly degredation of the solar
panels are
disregarded to avoid the calculation to become too
complex.
Later on this page, an Excel sheet can be downloaded that
takes all the
facts mentioned above in account.
Compensating the produced power
In the Netherlands, the power companies are obliged by law
(article 31c
of the Power Act 1998) to compensate the owner of the
solar power
system for the power that is being produced. Basically
this means that
the power company deducts the produced solar power from
the consumed
power by the owner of the solar power system. When an old
electricity
meter is installed, the meter turns backwards and with a
modern
'clever' meter, the produced power is measured seperately
and deducted
on the yearly bill.
This means that the consumer gets the same price for the
self produced
solar power as what he pays for the power he buys from the
power
company, as long as the amount of self produced solar
power is less
than the power he buys from the power company. This system
works as
long as the self produced power is less than the power
that is being
used by the consumer and as long as the self produced
power isn't more
than 5,000 kWh.
In case the solar power system produces more electricty,
each kWh of
electricty above 5,000 kWh or above the own power
consumption is worth
€ 0,05 - € 0,08 (price level 2013). This means that when
your solar
power system produces more than your own power
consumption, the earn
back time increases drastically.
Development of price for electricity
A key factor in the calculation of the earn back time is
the expected
average increase of the price for electricity. Based on my
own annual
power bill I was able to calculate that since 1997 the
price of
electricity has increased each year by 4.85%.
Estimation of output of system
On this
website
one can get an estimation of the annual output of your
solar power
system. Pick your location and a number of parameters
regarding the
capacity of your system, the slope of your roof and the
azimuth. The
14% for the estimated system loss is a good pick.
Calculating the earn back time
I've made an Excelsheet
that allows you to calculate the earn back time of your
solar power
system. The sheet uses for instances the annual increase
of the price
of electricity, the different ways to finance your system
and the cost
for replacing the inverter. The results are being shown in
a chart.
My system
Below are the details of my own solar power system.
Roof
My roof is perfect to install a solar power system. 7.10
meters wide,
4.30 meters deep, an incline of 30° and an azimuth of 186°
(180° =
south). Between half April and late August there is no
shade. Outside
these months there is a bit of shade in the last two hours
of the day.
Based on a couple of sunny days during the period with a
bit of shade
during the end of the day, I've estimated the yearly loss
to be 1.8%.
Panels
On my roof are 16 panels of the Chinese brand Yingli. The
panels are
installed in 4 rows of 4 panels each and are landscape
orientated. The
panels are the Yingli
Panda 255C-30b of 255 Wp
and the total capacity of the system is 4,080 Wp. These
fully black
panels look stunning. Due to the black color, these panels
may produce
a bit less electricity during the summer, but I don't
think it is a big
problem.
Inverter
The 16 Yingli Panda's are connected in one string with an
SMA
SB3600TL-21 inverter. The inverter is about 4 meters
away
from the last panel. The maximum effectivity of the
inverter is about
97%. In between the inverter and the electricity meter is
a cable of
about 6 meters and an extra fuse.
After
almost 11 years of use, the inverter was irreparably damaged
due to a short circuit and was replaced by a Goodwe
GW3600D-NS. The costs of the Goodwe are approximately half
that of the SMA, while the warranty period is 10 years
compared to 5 years for the SMA.
Mounting system
The panelen are mounted on the roof with the
mounting
system for tilted roof by
the German brand Wasi. First there are hooks that are are
attached onto
the roof underneath the roof tiles. On these hooks,
special black
coated aluminium rails are attached that are used to mount
the solar
panels on the roof. Even the bolts are coated black to the
solar power
system looks stunning!
Monitoring
Because I use an old fashioned electricity meter, I can't
monitor the
exact output of the solar power system. The SMA was
monitored by the free
software SunnyExplorer. This software
shows the production in a graph and also allows
the inverter
to be programmed. The production was also uploaded to
PVOutput.org by using a Raspberry Pi and SBFspot. The
production of the Goodwe are also uploaded to PVOutput.org.
This is currently still done manually.
Photos
A huge box with solar panels
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The hooks that go underneath the roof tiles
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Connecting the solar power system
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Installing the inverter
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Placing the hooks
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Placing the vertical rails onto the hooks
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The first panels are mounted on the roof
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The next panel is carried onto the roof
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Detail of the mounting system
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The finished solar power system of 4,080 Wp
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Output of the system
My solar power system was installed on 30 January 2013
and connected to
the electricity grid at 4.35 pm. During the final 30
minuts of sunshine
on this first day, the system produced 0.021 kWh. The
100 kWh barrier
was broken on 18 February 2013 at 5.45 pm and the
first Mwh was
produced on 5 May 2013 at 5.10 pm. Just over 2 months
later (on 9 July
2013 at 12.00 pm) the system reached 2 MWh. 3 MWh was
reached on 7
September 2013 at 1.40 pm.
Sites to store the output of the system
It is possible to store the output of your solar power
system online.
This is possible on www.pvoutput.org.
This way, other people can see the output of your
system. The details
and output of my solar-energy-system are available on
pvoutput.org. By using a Raspberry Pi
with
SBFspot, the output of my solar-energy-system is
uploaded to
pvoutput.org every 5 minutes.
Output up to August 2024
The graph below shows the output of my system up to
August 2024 The reference values are obtained by using this
website.
Between 30 January 2013 and
31 December 2013, the system produced 3,749 kWh. The
reference
production during the same period is 3,672 kWh,
which means that the
system has had a 2% larger production than
anticipated. On 30 January
2014 at 4.35 pm the system has been online for 12
months. During this
period, the system produced 3,869 kWh. In 2014, the
system produced
3,902 kWh. The 10 MWh barrier was broken on 6 July
2015, the 20 MWh barrier was broken on 9 March 2018
and the 30 MWh barrier was broken on 13 June 2020.
After exactly 10 years of service the system produced
40,080 kWh. At the time of the SMA SB3600-TL21's
failure, the system had produced exactly 43,592.543
kWh.
Last update: 1 September 2024
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