Easy to install and inexpensive, save money with plug & play photovoltaics!

In general, the expression plug and play (which literally translated means “connect and use”) is used in different contexts with reference to technologies that can be put into use within a system without the user of the system knowing or implementing a specific installation or configuration procedure.

Plug-and-play photovoltaic systems can be of two types:

• Grid-connected photovoltaic system without accumulators
• Grid-connected/non-grid-connected photovoltaic system with accumulators

In this article, we want to focus on plug-and-play grid-connected photovoltaic systems without accumulators as these are having great success in Europe, Australia and the USA. In particular, we want to talk about micro photovoltaic systems with a power of less than 800W, for which the Italian reference standard is CEI 0-21. Higher powers can still be installed, but require authorisation from the electricity distribution company and in some cases, even adjustment of the power lines that may not support the increased power generated by the system. For this reason, a separate regulation has been made for so-called plug-and-play micro photovoltaic systems below 800W and which do not require specific authorisations.

How does it work?

The system we want to talk about consists of only two components:

• One or more solar panels of the maximum capacity permitted by law (800W in Italy, 600W in Switzerland)
• Grid Tie type inverter for grid connection via plug.

Thanks to our photovoltaic kit, it is possible to feed the energy produced by the photovoltaic modules into the domestic grid during peak sunshine hours and consume it at the time with great advantages in terms of bill savings.

These micro-photovoltaic systems, are capable of producing a few hundred Wh (watt hours), which however, for example, can zero out the fixed consumption of a flat (mainly refrigerator, standby lights, etc…) or other, depending on the available surface area to be dedicated to production, and in any case remains the only alternative for the self-production and use of photovoltaic energy in limited spaces such as flats in buildings in large cities.

The objective of these systems is to transform totally passive flats from an energy point of view into active flats in terms of energy requirements. In the long term, these systems installed on a large scale can reduce the use of fossil fuels for energy production, thus forming a network of micro-generators that can not only produce energy for self-consumption, but also feed the excess energy produced into the grid.

For its functionality, the system will have to be connected as follows:

• The photovoltaic modules in our KIT must be connected in series
• The inverter must be connected to the grid via the output plug, which will be plugged into the nearest socket, and it is preferable to keep it indoors.
• Only energy net of self-generated energy will be taken from the grid.

The operating logic of a plug-and-play grid-connected photovoltaic system is different from that of systems with batteries. In fact, the energy produced by the panels is directly fed into the domestic circuit by connecting the output plug from the inverter directly to the socket nearest to the system; in this way, the energy produced is self-consumed at the very moment of production, i.e. there is no energy storage and consequent savings on the bill. The picture clearly shows an example of installation:

The electrical circuit is simplified compared to battery systems, and installation is quicker and accessible to even less experienced people. All connectors are different and there is no possibility of error when connecting the system to the grid, which practically turns it into a household appliance. As a disadvantage, if you can call it that, the system does not produce in the event of a blackout, i.e. if there is a power failure it automatically switches itself off and disconnects. Regulations prohibit feeding energy into the grid in the event of a failure of the grid itself as it would be extremely dangerous for operators who are sure that they are not connected to the grid and could be shocked by energy produced by systems of this type. For this reason, grid-connected inverters have a special mechanism that ‘shuts them down’ in the event of a power failure from the conventional grid.

Who can install it?

As mentioned earlier, the encouragement of plug-and-play photovoltaic micro-systems comes from a European directive on renewable energy and simplification. Many countries such as Germany and Switzerland have already transposed this directive to the point of even allowing the sale of these devices in supermarkets and without the need to request any authorisation for their use. The only limitation is the power of the generator, which must be of limited power so as not to risk overloading the grid. In Italy, the CEI 0-21 standard has the task of defining the rules for these systems. 

Having said that, anyone can install these systems, but a distinction must be made by paying attention to the meter that the electricity company has installed to measure our consumption. The new generation of electricity meters are all bidirectional, that is, they are able to differentiate between energy withdrawn from the conventional network and energy fed into the network by plug and play or other systems.

If we have a bi-directional meter, we can install a plug-and-play photovoltaic system without any additional precautions, and if we have produced excess energy, it will be ‘given’ to the grid at no cost to us. If, on the other hand, we still have an old type of meter, we must be aware that these do not differentiate between energy fed into the grid and self-produced energy, so only in the case of excess energy will the meter add the energy fed into the grid to our bill. One way to avoid this problem is to disconnect the inverter from the grid when we are sure that we are consuming less than our plug-and-play PV system is producing. One way to understand this is to use a plug-in or wireless consumption/production meter such as an OWL micro or similar.

Bi-directional meters are easily recognisable as they have a very clear symbol on the label represented by two inverted arrows as shown in the picture below: