Facts about the project

Client/owner/planner:: Owner of single-family house
Location:: Melides, Portugal
Construction type:: Single-family house with a guest house
Construction year and number of square meters:: 1995, 100 m²
PV-power and orientation:: 2.82 kWp
Heat storage size:: 400 liter boiler, 200 liter buffer tank
my-PV product in use:: 2 ELWAs, one for each tank (used in stratification charge)

How did you find my-PV?

The Portuguese house owner discovered the DC solution from my-PV at the photovoltaic trade fair Intersolar in Munich. With the use of ELWA, the owner makes the transition from a fossil-fueled hot water generation to a solar-powered one.

Obstacles/specialities during the installation

The responsible plumber had faced difficulties due to a lack of experience with photovoltaic installations, which involved initial problems with the installation of the ELWA in the tanks. The rest of the commissioning process was simple and easy.

Brief explanation of the system – what should be mentioned?

The system comprises of two tanks. One is a boiler with a volume of 400 liters and a buffer tank with a volume of 200 liters, which is used for hot water supply for the two bathrooms of the house and the guest house.

Both ELWAs are programmed according to the “stratified storage mode”. Hereby, in the first step the 400 liter boiler is heated up to a temperature of 60ºC and afterwards the 200 liter buffer tank is heated until it reaches a temperature of 65ºC. The PV system consists of 12 Panasonic modules of 235 W each, whereby two strings are connected in parallel. The distance between the PV modules and the 400 liter boiler tank is 38 meters and 25 meters distance to the 200 liter buffer tank. The first winter is over and the system worked already great during the winter months.

Persons in the household and hot water demand?

There are usually around 3 to 8 persons that are requiring hot water.

The power of the sun can also cope with the fluctuating demand – the storage tank must be dimensioned large enough to store the solar energy in sufficient quantities in the form of hot water during the day with ELWA.

Is hot water backup with mains power used?

Hot water backup of an additional 750 W (AC power) is used during the night with power from the grid, only via the AC plug of ELWA. This way, uncomplicated reheating is possible to ensure that there is enough hot water available.

Any cost changes/ROI?

The return on investment of the new system with the two ELWAs is approximately 6 years. What’s more is the fact that the hot water was previously heated with gas cylinders. The new system brings – besides the environmental aspect – a great level of convenience and a higher quality of life, as there is no longer the need to buy and transport gas cylinders.

Personal customer opinion and resumee

The owner is very satisfied with the system and concludes “The system worked well in winter as well and I think it will work even better in summer. The change from fossil fuel to a solar-based electrified water heating system is one of my contributions to climate protection and gives me a really good feeling each time I am taking a shower.“

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