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Off-Grid Photovoltaics: How Independent Power Supply Works

Terms like autonomy and energy independence are very popular at the moment. How does an independent power supply work with the use of off-grid systems?

An off-grid photovoltaic system, also known as an off-grid system or island system, is a form of power supply that operates completely independently of the public grid. Unlike conventional PV systems, which are connected to the public grid and can feed surplus electricity into it, an off-grid system is not connected to the grid. Therefore, no bureaucratic procedures are required – the produced PV electricity is exclusively used for self-consumption. Bureaucratic procedures that are normally necessary for connecting a photovoltaic system, such as grid access authorization, registration at the energy supplier, etc., are thus becoming obsolete. An additional advantage is cost savings: With a direct current solution, i.e., the direct use of photovoltaic electricity from the modules, no inverter (usually the "weakest link" in the PV system with a lifespan of 10 years) is needed – this results in savings ranging from €1,500 to several thousand euros, depending on the power of the photovoltaic system. When comparing these savings with the minimal feed-in tariffs, it is already worthwhile, especially for smaller PV systems.

In which cases is the use of an off-grid system advisable?

An autonomous form of power supply through an off-grid system is particularly advantageous in remote areas where there is no access to the public grid. A typical application can be found, for example, in an alpine mountain hut where there are no power lines within close proximity. Here, an island system enables cost-effective and environmentally friendly electricity generation – as well as forced 100% autonomy.

Nevertheless, off-grid systems are increasingly being used in single-family homes. This is partly due to the very low feed-in tariffs, which make feeding surplus electricity into the grid unprofitable for owners of PV systems. In some regions of Austria, there has even been a complete stop regarding grid feed-in for photovoltaic systems for several months due to limited grid capacities.

While the energy generation of an off-grid system usually does not suffice to fully cover the entire electricity demand of a single-family home throughout the year, other energy generators such as a small wind turbine can serve as a good complement. Alternatively, specific storage forms can be utilized, such as battery storage, to ensure maximum and continuous supply. However, an even more convenient option is to combine an off-grid system with another storage form, namely autonomous hot water provision. What is not (always) autonomous in this context is the water itself – but even here, some households are equipped with their own water source.

Power-to-Heat: Autonomous Hot Water Provision with ELWA

With our ELWA system, the produced solar electricity can be exclusively utilized for the generation of hot water. The linearly regulated hot water preparation device channels the direct current from the PV modules into the integrated heating element in the hot water tank, converting the generated solar electricity into heat without any loss. This means that during the summer, the solar energy from the entire yield of the off-grid system can be used to heat water. This is sufficient in many instances from March to October, the sun-rich half of the year, to solely provide hot water using our linearly regulated heating element. Even during winter, ELWA supports the conventional heating system for hot water provision or heat generation in a potential buffer tank.

Our latest reference project demonstrates how efficient even a small off-grid system can be when combined with ELWA: Our customer from Germany utilizes an island system with only 1.4 kWp to prepare hot water during the summer, thereby saving 1 cubic meter of gas daily. More details about this project can be found here.

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