Eingebaute DC ELWA mit Messgerät (Eigenbau) my-PV

ELWA in old building in Thuringia

Supporting the heat pump with ELWA

An uninsulated old building with hybrid heating in Thuringia benefits from solar energy in the buffer storage.

Datos sobre el proyecto

Type of building:
Construction year and number of square meters:
PV-power and orientation:
Heat storage size:
my-PV product in use:
Eingebaute DC ELWA mit Messgerät (Eigenbau) my-PV

How did you find my-PV?

An uninsulated old building with 130 m² was the starting point for the solar project of Mrs. Linke from a small community in the rural area of southern Thuringia in Germany. The single-family house built in 1929, did not offer many options for the heating system, so it became a hybrid heating system. In addition to oil heating, a heat pump was used. With the necessary heating requirements for the two floors of the existing old building, electric – or better still, solar-electric – room heating would not have been possible either. Nevertheless, the power of the sun can be used in the house. The 500 liter buffer tank offers enough storage volume to bunker the solar energy in the tank or to support the primary heating.

After doing research on the Internet and finding information on the my-PV website, for Mr. Oßwald, the solution was clear. It should be inexpensive, efficient, and easy to retrofit, so the choice immediately fell on the ELWA.

The direct current solution from my-PV, which can be connected directly to the photovoltaic modules, uses the 2.24 kWp PV system to directly pass on the photovoltaic power generated in the modules to the heating element – and this can be linearly controlled!

Obstacles/specialities during the installation

The challenge of this project was the unfavorable roof orientation of the house and the outbuildings, which would not have allowed any other type of installation than the one chosen: By means of inclined elevation on the house wall, there is a noteworthy yield also in winter, due to the almost vertical orientation, which from the ELWA is converted directly into heat in the buffer tank. In this way, the heat pump and oil heater are relieved and "forced" to undergo fewer and shorter switching cycles, which means that the operating time of both primary heaters can be reduced and the service life extended.

Brief explanation of the system – what should be mentioned?

The cost-effective, efficient arrangement of the photovoltaic panels, which were to be placed alongside the heat pump with minimal installation effort and the shortest cable routes, was decisive for the implementation of the project. At the same time, the maximum output can be achieved with minimal effort for retrofitting, to minimize operating costs for the uninsulated single-family house and to relieve the primary heating system.

The ELWA is located in the 500 liter buffer tank of the heat pump, i.e. in the heating circuit. This is permanently hydraulically connected to the combi storage tank of the oil heater. The hot water required is therefore heated in the combi storage tank of the oil heating system, even though it is not running in summer. During summer, only the heat pump runs, but now effectively supported by the ELWA. If there is a need for heating in the transitional period and in winter, the oil heating "steps in" automatically.

In addition, there are two people living in the single-family house who need around 90 liters of hot water per day. The ELWA is approved for use in fresh water and heating water applications, which means that it can also be installed in drinking water storage tanks. In this way, the hot water is also generated efficiently and in an environmentally friendly way using the sun – without increasing operating costs.

Is hot water backup with mains power used?

Even if a primary heating system is available, the hot water backup is used by the ELWA. On days with too little solar radiation, this enables reheating with conventional household electricity from the public grid. In this way, a comfortable temperature can always be maintained, even if too little photovoltaic yield is available for a few days.

"In this project, the hot water backup with mains electricity was only used very sporadically," says Mr. Oßwald.

Opinión personal del cliente y resumen

"The planned support of the existing heat pump by the ELWA works very well – especially on sunny days we are satisfied with it. The only problem is that the sun doesn't always shine - but that's not because of the ELWA!

Since then, the use of the ELWA has significantly reduced the number and duration of the heat pump's switch-on cycles!" summarizes Mr. Oßwald, the patron of the reference project in southern Thuringia.

Eingebaute DC ELWA mit Messgerät (Eigenbau) my-PV
Eingebaute DC ELWA mit Messgerät (Eigenbau) my-PV
Eingebaute DC ELWA mit Messgerät (Eigenbau) my-PV
Eingebaute DC ELWA mit Messgerät (Eigenbau) my-PV
Eingebaute DC ELWA mit Messgerät (Eigenbau) my-PV
ELWA Seitenansicht


in use

ELWA is a 2 kW photovoltaic water heating device. Direct current from photovoltaic modules is transferred directly to the built-in heating element and immediately converted into heat without loss.

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