There are various types of photovoltaic systems: stand alone, grid-connected, storage grid-connected, plug&play. Here’s a list of characteristics
The main types of photovoltaic systems are:
- stand alone systems.
- grid-connected systems;
The evolution of these types of systems has introduced new models: the storage model connected to the network and the innovative plug & play.
To identify the type of system that best suits your needs, we analyze the characteristics and advantages of each system.
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Stand alone photovoltaic systems
The first of the 2 types of photovoltaic system is the ‘stand alone PV system, or island system. This type of photovoltaic installation isn’t connected to national electricity grid, but is connected to an autonomous energy storage system – with batteries – that store the electricity produced by the plant and return it to the user at the time of need.
The typical elements of a stand-alone system are:
- photovoltaic field;
- MPPT inverters;
- charge regulators.
How do stand-alone photovoltaic systems work?
A stand-alone system works as follows:
- the solar panels capture incident solar energy and convert it into direct current;
- the DC energy collected is transformed into AC (alternating current) by the inverter;
- the produced alternating energy can be consumed immediately by the user or can be stored in batteries and then used when necessary.
This process implies that the accumulator (the battery) is charged and discharged; in order not to compromise its efficiency, the charge regulator manages this mechanism.
What are the advantages of stand-alone photovoltaic systems?
With the reduction of component costs and the spread of lithium technology, stand-alone photovoltaic systems are increasingly competitive compared to systems that involve the use of fossil fuels.
In fact, this type brings many benefits to the environment and the end user:
- zero emissions: utilities consume the electricity produced and do not generate polluting gases;
- constant energy cost over the life of the installation: the energy cost is not affected by energy price fluctuations linked to the cost of oil and gas;
- extreme flexibility: the installation is fully scalable as is the size of the electrical storage system.
Grid-connected photovoltaic systems
The second photovoltaic system type is the grid-connected photovoltaic system. A solar system connected to the national electricity grid.
In this type of plant, the national electricity grid becomes an infinite storage tank in which energy from renewable sources is introduced when the plant produces and the user does not consume and from which electricity is taken at the time of need, when the plant does not produce (at night).
The Solar PV single-line diagrams for a grid-connected system is formed of these following elements:
- the solar panels;
- MPPT inverters;
- energy production meter;
- energy exchange meter.
How do a grid-connected photovoltaic systems work?
The grid-connected system operates according to the following phases:
- the solar radiation hits the photovoltaic generator;
- the inverter converts the produced electricty from DC to AC;
- the produced energy is exchanged and used instantly by the user if required or, alternatively, is sent to the national grid, from which energy is also taken when necessary.
In this system the production meter will count the energy produced and consumed directly by the user, while the exchange meter will count the energy consumed by the user taken from the network.
What are the advantages of grid-connected photovoltaic systems
The installation of a grid-connected photovoltaic system can be convenient and advantageous, both in economic and environmental terms.
More precisely, the benefits are:
- reduction of the weight of bills;
- reduction of polluting emissions;
- the possibility to monetize produced energy.
Plant with “storage” electricity storage connected to the electricity grid
Among the types of photovoltaic system the most common today is the model withstorage of electricity, connected to the electricity grid.
It is an innovative system in which the energy produced is first stored in storage systems (or accumulation) and, once the capacity of the batteries is reached, the residual energy is fed into the national electricity grid. For this feature it is also called a hybrid photovoltaic system.
A “storage” photovoltaic system connected to the electricity grid consists of:
- solar panels;
- MPPT inverters;
- energy production meter;
- energy exchange metering system.
The main features to consider in a home photovoltaic storage system are:
- the power of the storage system, i.e. the storage capacity of electricity;
- the lithium battery’s lifecycle;
- the activity of the inverter;
- the efficiency in storage and charging;
- the size and weight of the storage.
How do photovoltaic systems with grid-connected storage storage work?
The photovoltaic “storage” system, connected to the grid, works according to the following mechanism:
- during daytime, the photovoltaic solar panels recharge the storage batteries;
- when the batteries have reached their maximum capacity, the energy produced and not self-consumed, is fed into national-grid;
- during evening or night hours, the energy is supplied from the storage system, in complete autonomy from national-grid;
- when the storage runs out of energy and the batteries are discharged, domestic energy requirements will then need to be powered by the national electricity grid, completely automatically and without any interruption of service.
A “storage” storage system is therefore always working and also performs the function of emergency power supply: in the event of a power grid blackout, in fact, the plant continues to operate.
A storage system also offers additional advantages:
- high level of self-consumption equal to 90÷100%;
- partial independence from the power grid of public and private buildings.
For all these reasons it is important to carefully evaluate the type and model of system to be installed. To simulate the preparation of a system connected to the grid, I recommend you to test the trial version of a photovoltaic software that will guide you in the design of any type of photovoltaic system connected to the electricity grid.
Plug & play photovoltaic systems
The plug and play photovoltaic system, also often referred to as plug in. It’s an innovative solar micro-plant with nominal power below 350 W and that can be installed on balconies, windows or in the garden.
Generally, a plug and play solar system consists of:
- photovoltaic module, the actual panel, which can be composed of monocrystalline or polycrystalline photovoltaic cells;
- micro-inverter, and any other accessories, to convert the direct current produced by the panel into usable alternating current;
- support frame and fixing and anchoring brackets, to facilitate installation on balconies, terraces, gardens, external walls of the house.
How do plug & play photovoltaic system work?
A “plug and play” photovoltaic system provides green and renewable energy by connecting to the plug of the home current.
This system produces energy as follows:
- place the solar panels outside your home with an exposure that is as far south as possible, so as to capture the maximum amount of solar radiation;
- the inverter makes the captured energy usable;
- connects the output plug from the inverter, directly to the outlet closest to the system: in this way the energy produced is self-consumed at the moment of production.
What are the advantages of plug & play photovoltaic systems?
The plug and play photovoltaic system is available to everyone.
The installation of this type of solar system has numerous advantages:
- installation versatility: it can be installed on a balcony, on a terrace, on the roof, on solar flooring, on the external walls of the house, on the fences or in the garden and, depending on the needs of each one, you can choose different fixing brackets;
- extreme simplicity of assembly: it can be connected without the need for special authorisations;
- savings on the electricity bill of about 20%;
- environmental sustainability;
- energy efficiency.
In addition, the average life of a plug and play panel ranges from 15 to 25 years. It is, therefore, an advantageous solution considering that the cost of the device could be amortized in a few years.
The following image summarizes the main types of solar plant on today’s photovoltaic market.
The configuration and design of any system requires a precise analysis of the input variables to the system and the output variables.
To date, grid-connected photovoltaic systems are the most sustainable considering the value for money and the amount of energy produced.
In case you opt for a grid-connected system, storage or not, I recommend the use of photovoltaic software capable of supporting you for systems on new or existing buildings, in every location and with every type of panels and inverters. Try it for free to design in 3D, size the system, create your single-wire diagram in one solution.