Experimenting with Solar Panels

As I mentioned earlier, we are building a house in my home town Bad Langensalza. Since my teenage years I’ve been fascinated by technology of many kinds. That lead me to study computer science and later on focus my entire professional life around that. Now, building a house is – generally speaking – a rather traditional kind of engineering work. Putting up walls, a roof, do some ground, etc. We’ve found a great company to take care of all of that, but more about the house topic in later blog post.
Let me give you a little insight into my motivation on experimenting with solar panels. The house “package” we chose, came with a standard natural gas-powered heating system. That system is supported by simple solar tubes to pre-warm water. Those solar tubes don’t generate electricity, they just warm up the water. It’s basically just black tubes with water inside. We personally feel that fossil resources are generally something we should try not to use too much of. So we upgraded our “package” from the natural-gas-powered heating to an entirely electric-powered air-water-pump system. It is generally speaking quite similar to a split-type A/C that’s popular in Asia and other parts of the world. One reason for choosing that and paying for the additional costs was to allow us to eventually support our heating system with solar panels that generate electricity (see photovoltaics). Heating is in Europe what air-conditioning was in Hong Kong. It is essential for a comfortable home with Gemütlichkeit. Especially in the winter months, of course.

Before I left Hong Kong, I bought a “solar panel kit” from China and shipped it over along with my household. It consists of the following:

  1. 100W Solar Panel (monocrystalline cells)
  2. Controller unit
  3. Power inverter unit (convert DC to AC)
  4. Some cabeling

Back in Hong Kong, I already unwrapped the set to test it. You can’t be too trusty with the mainland Chinese vendors. I quickly realized that I needed a battery to get the entire thing working properly. So I decided to push that testing back to when I’m in Germany. I was quite sure my dad still had some car battery hidden in his garage somewhere. Guess what? Of course, he still had a battery!

After finally having found some time to do my experiment, I unpacked everything and set it up in their garden. I connected the solar panel to the controller. Connected the controller to the battery and connected the power inverter to the battery as well. Then I connected a consumer (a FM radio) to the power inverter to test it and switched everything “on”. Guess again: What happened?  Yep! Nothing happened. Here is how that set up looked like:

Basic solar panel setup: panel – battery – inverter – controller (left to right)

Here is a quick video about that:

Technically, it should work like this:

  1. The solar panel converts the sun’s energy into 14.4V DC electricity.
  2. The controller takes that electricity and passes it on to the 12V car battery to charge that battery.
  3. The controller ensures, the correct charge is passed. So you have to configure which type of battery you have. This depends mainly on the number of cells your battery has (e.g. 3 cells, 4 cells, 6 cells, etc).
  4. The converter simply consumes the 12V DC electricity from the battery and converts it into 240V AC electricity.
  5. Any standard consumer electric appliance can then be powered by the converter’s output (e.g. a radio).

As my radio didn’t turn on, there was apparently something wrong with my setup. So I tried several other options. The controller (the most right device in the photo above) also has two more additional outputs besides the one for the battery:

  1. A direct consumer output (voltage can be adjusted), and
  2. Two USB ports

I tried to connect the power inverter to the direct consumer output of the controller to see if my radio turns on then. Nothing happened again. Yet, the controller has a display that appears to be operating correctly. So I quickly got a USB cable and tried to charge one of my old phones through one of the USB ports. That worked flawlessly and with about ~2A output current, the phone charged up quite quickly. Have a look at the charging working properly:

Conclusion Test 1

It appeared that the solar panel worked well. The controller seems to have worked too. Also, when the battery is connected, the controller’s display output indicated that it is charging correctly. Hence, I assumed there was a problem with the inverter unit. I double-checked whether I connected the unit properly. It appeared to be getting enough electricity. That’s because the fan turns on automatically when I switch the inverter on. So it seems to be receiving enough electricity from the battery or in the other test directly from the controller. My conclusion was to try another inverter. So ordered one on Amazon.

Test 2 – New Inverter

The new inverter I ordered off Amazon cost just €20, but is also just a 300W inverter as opposed to the original inverter I got with the whole set that can do 1000W. Anyhow, I only have a 100W solar panel so far. The whole setup with the new inverter looked like this:

Setup #2: solar panel, battery, inverter, controller, radio.

Believe it or not, the setup worked out-of-the-box now. I managed to get some sound out of the radio and finally listen to the weather forecast. The lawn obviously needed some rain soon! Here is a quick video of the setup with the radio playing:

Solar Panel Photo Gallery


Upcoming Solar Panel Tests

I’m now curious on how this works with multiple solar panels and larger electricity storage. Especially, how I need to wire it to get it working properly and how much electricity it can actually collect, convert and store. Of course, there are all these theoretical calculations you can easily run based on how much a solar panel can process, what the average sunshine time is in your area, how you convert and store the electricity and so on. But all these are theoretical values and I was never a fan of plain and dry theories. I got to try it myself. See it in action and experience its practicality.

So my next solar goal is now to:

  1. Get 2 more 100W flexible monocrystalline solar panels
  2. Replace old battery with 2 new car batteries that store at least 80Ah each
  3. Install all 3 panels and 2 batteries in a more semi-permanent setting
  4. Let this run / charge / consume for a few days / weeks


The Purpose

My end goal is to cover certain roofs of our new house / property with solar panels. As we are planning to have a carport and a permanent awning for the terrace, my plan is to cover both with solar panels. Here in Germany we of course have service providers / construction companies where you can order your terrace awning or carport with a solar panel roof including the construction of such. Think: all-inclusive-service. That would be the laziest option, but also the easiest one of simply getting it done. As you can imagine, these installations are then quite expensive. I was looking at a 10m x 4m terrace awning that’s completely covered by solar panels and the price was something in the range of €35k ($41k). That is quite A LOT I find and not even close to my budget. Though, including labor I guess it may be a fair price. Yet, we still wouldn’t have a carport yet.

So, I’m experimenting with these solar panels to figure out if the solar panel part is something I could perhaps do myself. It may or may not be practical for various reasons.

  • Perhaps there’s too much work involved?
  • Perhaps the pure material costs are too high to justify their use?
  • Perhaps the efficiency of the solar panels aren’t as good on average as sellers claim them to be?
  • Perhaps my plan gets killed by special EU customs duty on Chinese solar panels?
  • Perhaps storing electricity is not efficient enough?
  • Perhaps the batteries for storing them aren’t as reliable as they should be?

There are so many questions and there are probably a lot more I haven’t even thought about yet. I won’t be able to answer at least some questions to my satisfaction, if I don’t get started. I simple need to get at least some steps closer to entirely understand the practicalities behind using solar panels. That’s what I’ll do in the next months. Let’s see how that goes.

Stay tuned for more stories on solar panel experiments and our house construction process, progress or non-progress. 


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5 Replies to “Experimenting with Solar Panels”

  1. What about legaland insurance issues? Are you even allowed to connect something like this to the grid/your house circuits?
    Also when I let checked a professional setup was much cheaper and there where also subsidies and special credits by KfW. Might benqorth exploring…

  2. Good points.

    I’ve looked at several KfW support packages, but generally most of them were plain and simple loans. Their conditions only look attractive at first sight, though. Also, if you don’t have much of a credit score, it’s not that easy to get it. Subsidies are often coupled with loans (think: you get a discount on your outstanding loan payment at some point), but again you’ll need to get a loan for that in the first place.

    From a grid point of view, well I don’t even know yet whether I’d connect it to the grid in the end. But for sure, there will some kind of certification required that everything is proper. That’s another question that would need to be answered 🙂

  3. Hey man, intresting experiments, first: please be careful with electricity, especially DC voltages. Anyway second: my parents set up a complete solution for their house a week ago and it now runs great. It is at about the same area in germany(comparable solar radiation) but with 6kW much bigger. can supply the whole household including warm water. quite a clever setup, but costly. the main thing is the management unit, it determines the efficiency of everything else. does not even need a big battery if the load is balanced well. connection to the grid has become easier the last years but pays no more. you can can only return you investment by ‘saving’ i.e.not buying, electricity. if you like i can ask them for the specs / suppliers / service company. anyway welcome back in middeldeutschland*g

  4. @Hin: Thanks. I’ll check that out.

    @Leone: Surely, I’m always careful. We’ve received some great electronics education at uni, right? We’ll see if that was sufficient 🙂

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