Issue 1: My Energiewende
Giving an overview of my photovoltaic system and energy management in my house as a reference for future analysis.
After I got tired of the medium Twitter, I would like to share my knowledge and experiences with my photovoltaic system, heat pump and energy management in this newsletter. Since I will refer to this again and again in future analyses, I would like to describe the main components of the house and the PV system in this text.
The house
The single-family house was built in 2020 with prefabricated brick elements and then insulated on the outside with a thermal insulation composite system. The construction corresponds to the German efficiency standard "Effizienzhaus 55".
The location of the house is very favourable: the property is an elongated structure, with the broad side facing south. In addition, the floor plan of the house was chosen in such a way that the (currently unused) chimney and all downpipe ventilations are on the northern roof.
The south-facing roof can thus be used entirely for a photovoltaic system that remains free from shading. Large south-facing windows also allow plenty of sun into the house.
A special feature is the ceiling heating, called "climate ceiling" by the manufacturer. It is structured like underfloor heating, except that the heating pipes run in the ceiling and not in the floor. Ceiling heating works exclusively via thermal radiation and can also be used for efficient cooling in summer. Below is a picture from the factory, taken during the manufacture of a ceiling module (not mine).
Heat Pump
The heat pump comes from Daikin - a Japanese company, but the technology comes from the German company Rotex, which was bought by Daikin. The "Altherma 3R" model is designed as a split heat pump. This means that the compressor circuit of the heat pump is divided between the indoor and outdoor units, and the heat transfer to the water in the heating system only takes place in the indoor unit. The coolant (R32) is climate-friendly, but also flammable. Compared to oil and gas as fuels, however, this is a negligible problem.
The outdoor unit is oscillatingly mounted on a solid concrete foundation using rubber sleeves to reduce the transmission of structure-borne noise. There is a gravel bed under the outdoor unit so that condensation water can drain and seep away without any problems.
In addition to the controller and the control panel, the indoor unit contains in particular the heat exchanger, with which the heat from the compressor circuit is transferred to the heating circuit of the house. As described above, the house is equipped with ceiling heating, but this is irrelevant for the heat pump. For the heat pump, the function of the heating circuit is identical to that of underfloor heating.
One of the outstanding features of this heat pump is the very large operating range of the circulation pump, see the diagram below.
If the heat pump is running with the compressor in heating mode, the dashed area of the pump diagram can be used. As a result, the low heat requirement of a well-insulated house and clocking can be served without a hydraulic switch. A significant advantage.
Hot water is also provided by the heat pump. A fresh water station with two water reservoirs, each with a capacity of 300 liters, is used for this purpose.
The storage water of a fresh water station remains permanently in the storage tanks. Fresh water is passed through a heat exchanger inside and is thus heated in a continuous flow process. This allows the temperature of the water tank to be kept low without causing legionella problems. The hot water is always fresh from the tap.
Ventilation System
In order to achieve good insulation, modern houses are very airtight and in order to achieve the German "Effizienzhaus 55" standard, this must also be proven with a "Blower Door" test.
However, the tightness of the building envelope also brings with it problems. The exchange of air must be very disciplined. A ventilation system with heat recovery is ideal for this.
The diagram below is a screenshot of the app used for monitoring and control. It clarifies how the ventilation system works: used and warm air is extracted and passed through a heat exchanger in which the heat is transferred to the fresh but cold air from outside. This means that the air is exchanged with minimal heat loss.
The ventilation system works surprisingly quietly - not so much in the technical room, but in the living rooms and bedrooms, where it is not audible.
Phtovoltaic System with Battery Storage
The heart of the energy technology is the PV system with battery storage. As described above, the south-facing roof enables a large PV system with 42 modules each with 340 Wp, i.e. a total of 14.28kWp. The modules are from the manufacturer Trinasolar in China.
An S10E "Hauskraftwerk" from E3/DC is used as the inverter and battery management system. As is now common with many newer so-called hybrid inverters, the E3/DC system is based on the coupling of PV modules and battery via a direct current circuit. The electricity is therefore only converted into alternating current when it is transferred to the home network.
The system has a storage capacity of 13.5kWh net, a maximum charging/discharging capacity of +/- 3 kW and, in the event of a power failure, can supply all three phases of the house with emergency power or supply them in isolated operation.
The result of the effort
All of the measures described above result in the energy pass with a very low energy requirement and CO2 emissions of 1 kg per square meter and year.
In fact, the energy pass does not reflect the whole truth, because the house generates a surplus of green electricity in the annual balance, but more on that in future analyzes in this newsletter.
So much for this first issue of my newsletter. Hope you enjoyed my text and please bear with me for being a novice both on Substack as well as in online writing. Comments are welcome.