Why won’t your solar panels save you from a blackout?

Why won't your solar panels save you from a blackout?

Illustration: Energy Revolution, Image: David Trebosc – Flickr CC.

Unless a battery is associated with it, a domestic solar plant cannot take over in the event of a grid power outage. During a blackout, therefore, you will be left without electricity, whether or not you have photovoltaic panels on your roof. If the situation seems absurd, it is explained by ultimately logical technical and security rules. explanations.

The fear of a blackout next winter may encourage some people to equip themselves with a solar power plant. People who already have one may also think they are safe from general power outages. However, photovoltaic panels can only replace the network when they are associated with a battery. A configuration that is still rare in France, because it is very expensive.

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Auto power off in case of power outage

The vast majority of photovoltaic plants installed in private homes are for self-consumption: they inject their production into the domestic network, then into the public network in the event of a surplus. Ultimately, the two networks are not so different: the electrical cables of a house constitute the end of the great public network.

Thus, during a general outage, the production of the solar panels installed there is interrupted in the same way as the other plants located in the affected area. it is a legal obligation. Shutdown occurs automatically thanks to the decoupling relay integrated in the inverter.

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a security issue

This is primarily a security measure. This avoids the presence of current in the lines, where agents are likely to intervene. The interruption of production also prevents risks linked to an imbalance of loads on the network.

During a blackout, the photovoltaic panels that would continue to inject their production would deliver irregular voltage and intensity, because they were not synchronized with demand. Therefore, there is a risk of deterioration of the devices, overheating of the conductors and, therefore, of fire.

In addition, “network inverters”, which convert the direct current produced by the panels into alternating current intended solely for injection into the network (public or domestic), can only operate when they detect a voltage in the latter. They are designed to deliver a current perfectly in accordance with the specifications of the public network and so stop when inoperative or out of sync.

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How to be autonomous with solar panels?

To be autonomous in the event of a cut with photovoltaic panels, the only solution is to install a battery and a “Hybrid” or “off-grid” inverter. The system will automatically take over during the interruption and will only inject the energy necessary for the operation of your electrical devices, without sending current to the public network.

The set is often marketed as “anti-cut solar kit” in online stores specializing in photovoltaic equipment. It generally includes a hybrid inverter, one or more batteries (lead or lithium), cables and devices necessary for connection and sometimes includes panels.

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These devices are sold between €1,3000 and almost €10,000 depending on the battery capacity and the power delivered. Please note that it is essential to have irreproachable skills as an electrician or call a professional to install it at home. These kits should not be confused with “ready-to-plug-in self-consumption kits”.

Domestic battery: expensive but useful

Bought alone, a battery capable of powering a fridge-freezer, a computer and a 150-litre water heater for 24 hours without any other power source costs around €5,000 (10kWh).

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photovoltaic installations able to be independent during a power outage are therefore particularly expensive. However, this can be interesting if you live in an area subject to regular interruptions or if you cannot do without electricity, even for a few hours a year.

The investment is not only useful for compensate for power outages. The rest of the time, the battery will allow you to maximize your self-consumption rate and avoid injecting free or very low-cost electricity (currently only €100/MWh) into the public grid.

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