SOLAR PANELS

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