After much deliberation, the family decided to install solar panels in our holiday home.
When it came to sizing, we set ourselves the goal of avoiding back-feeding, as the rules for this can change all the time and the calculation of the return on investment is fraught with too much uncertainty.
As the summer house is mostly used in summer and therefore our consumption is higher in summer, this fits well with the annual production cycle of solar PV systems. In summer we regularly charge our hybrid car, which means a consumption of 15-20 kWh per day. Circulating and tempering the small swimming pool requires 5kWh of energy per day, and other household consumers (fridge, hobs, air conditioning, etc.) consume on average another 5 kWh. So it can be seen that we are quite heavy consumers in summer, with an average daily consumption of around 30kWh.
Regarding the timing of the consumption, it is possible to match it to the instantaneous production of the generating unit by switching some of the consumers on and off. The swimming pool, the fridge, but also air conditioners are relatively large heat consumers, and car charging can be slid too.
The first step was to monitor the time distribution of actual consumption over a period of one month (this can now be done very cheaply using smart meters connected to the internal wifi network). The required solar panel capacity and the storage to match it were then sized. The system thus consists of a 10kWh battery and 16 solar modules, as this combination yields the best payback figures, assuming that the option of recharging will not come back to us.
In winter, the cottage is converted to a low-temperature control heating – using the heating mode of the air conditioners. The cost of this is of course highly dependent on the weather, but it is certainly considered to be more economical than the case without the use of renewable energy.
When 14-year-old Peter, who lives in the neighborhood, asked to see our equipment, I was happy to show him all the components. He looked at them with interest and then asked me how they were connected. Then he took out his mobile phone and pressed it thoughtfully. I didn’t pay much attention to what he was doing, as teenagers are always busy with their mobile phones.
Peter thanked me for showing him the system and went home. An hour and a half later he turned up again and said he had something to show me. He came in again and showed me on his mobile phone how he could switch off the soul of the installation, the inverter, in a few seconds. I watched in disbelief, certain that only I would have access to the password-protected device.
I had heard a lot about the attacks and threats to which IT equipment is exposed. But it’s one thing to hear something and another to experience it! After all, my house is not the only one with solar panels, and it’s bad to think that Peter’s game is to turn them all off! On a hot summer day, it would be like Peter turning off a large nuclear power plant!
I started looking for a suitable technical solution for protection. Consulting experts, I was surprised to find out how much it would cost. I was told that solutions are being developed to protect the IoT systems I use, which are cheap but provide high security, because the owners of many small systems cannot be expected to purchase expensive solutions.
But there is a need for such solutions. In our country, for example, a system that is shut down by external intervention can lead to frost damage in winter and disruption of comfort in summer. Strangely, the hybrid inverter at the heart of the system is easily accessible by anyone, no high-level hacking required. We have decided to provide this delicate IoT system with anti-piracy protection.
After much enquiry, we met with the IoTAC project specialists. The modular protection system they are developing will be able to protect our household. We will be installing them soon and I will report on the results in an upcoming blog.