Hot water directly from PV

Hot water from solar energy was previously only known from solar thermal systems. These are relatively complicated and maintenance-intensive systems that work inefficiently, especially in the transitional period and in winter. It is much easier and cheaper to transfer direct current from photovoltaic modules directly into a power controlled immersion heater and convert it into heat without loss.

This works quite simply with ELWA from my-PV, an electronically controlled PV immersion heater. For operation, no connection to mains is required as the unit is powered from PV (pure off-grid operation). Optionally ELWA can also maintain a minimum temperature in the tank (from mains power).

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Standard PV system • with high optimization potential

A photovoltaic system with inverter supplies household appliances if demand happens simultaneously. Without a possibility to store excess yield, the degree of self-utilization ratio is limited. Different my-PV solutions will massively increase the degree of self-consumption.

Hot water from PV • Power Manager + immersion heater

Simply use excess PV energy for hot water production and thus optimize self-utilization ratio of the system. A standard heating element is installed in the hot water boiler or buffer tank. The heat output is linearly controlled by a Power Manager which regulates the PV feed-in power to zero and thus maximizes your self-utilization.

This works with my-PV´s AC•THOR / AC•THOR 9s. Standard electric heaters become “PV ready”. Optionally AC•THOR / AC•THOR 9s can also maintain a minimum temperature in the tank from mains power. A separate temperature sensor can optimize energy taken from the public grid.

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PV Hot water + space heating • for low energy houses

In modern low-energy houses, conventional, water-guided heating systems are oversized. Therefore, in addition to the hot water production, space heating of the building is also supplied electrically - solar-electrically and thus predominantly with excess PV energy. At the same time, even at night or on short winter days with little PV yield, it is guaranteed that the indoor climate remains comfortable thanks to electricity from the grid.

The heart of the solar-electric house is my-PV´s linearly controlled photovoltaic Power Manager AC•THOR 9s for grid-connected photovoltaic systems.

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Electricity rate:

You will find your tariff for purchase and feed-in on your electricity bill. Make sure that the price is made up of the energy price, grid charges, as well as levies and taxes.

Typical values for

• Austria: 4 ct/kWh for feed-in, 20 ct/kWh for purchase
• Germany: 11 ct/kWh for feed-in, 28 ct/kWh for purchase

Typical prices for energy sources in Austria in Euro ct/kWh are:

• Heating oil 8,30
• Natural gas 5,45
• Wood pellets 4,96
• Wood logs 5,19
• Wood chips 5,23

Prices incl. taxes and additional costs (e.g. filling lump sums)

Source: Energy Institute Vorarlberg, February 2020.

Settings for the conventional heating system for hot water preparation:

• "Entire year" - Hot water is produced all year round with the normal heating system. Excess PV energy is used additionally if possible. There is no hot water preparation with mains power.
• "Heating period" - Hot water preparation only in summer with mains power (boost backup), in winter with the normal heating system.
• "Off" - Boost backup is provided all year round with electricity only.