Photovoltaic installations are becoming more efficient and effective in generating electricity compared to those offered on the market a few years ago. On the market, we can use ON-grid, Hybrid, or OFF-grid systems. 

Which of them is better for us and why?

When choosing a photovoltaic installation, we can choose from two types of systems:

ON-grid
OFF-grid
Hybrid

Both systems obtain electricity from the sun, converted into electricity so we can later use it in our homes. Both systems use solar photovoltaic panels, an inverter that changes direct current into alternating current plus protection: mounting and monitoring system. The connection method to the external power grid distinguishes ON and OFF grid systems.

ON-grid photovoltaic installation is the system most often chosen in prosumer installations. It is the best solution for houses that can use electricity from external sources and want to maintain at least partial energy independence.

Connection to the public grid

The ON-grid system works on the same principle as OFF-grid. Photovoltaic panels use solar energy to transmit the direct current to the inverter. The inverter converts direct current into alternating current, which we can safely use in our home.

In the summer, we often produce more electricity than we need. What can we do with it?

In ON-grid installations, connecting the photovoltaic installation to the external power grid is most important. Thanks to this, we can transfer the excess electricity produced to a local or national energy supplier.

An essential element of our installation is a two-way meter, thanks to which we will know how much electricity has been discharged by our installation to the electrical network and how much has been taken from it. Meter replacement is free of charge and is carried out by the energy company.

On-grid installation – is it worth it?

ON-grid photovoltaic installations are much cheaper than off-grid systems. If we connect our network to an external power grid, we can also save on electricity bills. The network will be our energy warehouse, allowing us to store surplus electricity produced.

Tracking of the maximum power point in ON-grid systems

In addition, one of the significant improvements in ON-grid systems is the efficiency of the photovoltaic cells, which have gained importance in the industry. Another major advance is maximum power point tracking (MPPT), which has improved the performance of existing grid systems.

Maximum power point tracking is a technique used in photovoltaic systems that allows you to get the maximum power from your solar panels. The idea of ​​operation is that the system tracks the maximum power point on the IV curve of the solar panel and adjusts the operation of the converter so that the panel always operates at this point. Thanks to this, it is possible to obtain maximum power from the installation regardless of weather conditions and the level of panel exposure. 

MPPT is particularly useful in photovoltaic systems because it allows maximum power to be obtained from the panels even at low voltage and current, which is often encountered in non-ideal conditions such as cloud cover or changes in the angle of sunlight. Various methods are used to track the maximum power point, such as numerical algorithms, heuristic methods, and methods based on artificial intelligence. 

It is worth mentioning that tracking the maximum power point allows not only to obtain maximum power from the panels but also to increase the efficiency of the entire photovoltaic system, which translates into lower operating costs and greater efficiency. 

MPPT solar controllers will be handy in panels with higher operating voltage, with a power of 280 Wp and more, used to build larger island/hybrid photovoltaic systems.

What exactly is MPPT for?

Solar panels don’t receive as much electricity when they aren’t operating at their most efficient voltage. Without maximum power point tracking (MPPT), grid systems cannot utilize the maximum power available from solar panels, resulting in losses.

Therefore, MPPT is critical for optimizing the relationship between solar panels and the power grid. It maximizes energy harvesting under various conditions by maintaining the photovoltaic cell array in the ideal operating voltage range.

For solar systems with batteries, installing MPPT charge controllers is a way to achieve this because they regulate the voltage between the solar panels and the batteries. MPPT charge controllers can help protect your batteries and keep them running longer. Similarly, MPPT tracking is a feature built into grid drive inverters, but some have more advanced features than others. 

Understanding this critical topic can increase the productivity of your solar system and make your customers happier. Knowing when MPPT benefits a photovoltaic array is essential from a client service perspective.

How does MPPT work?

How exactly is the maximum power point determined? What are the technical challenges involved? These questions will be answered by methods for determining the optimal load characteristics of a photovoltaic panel. 

These include, for example:

1. Perturbation and observation. It is a reasonably simple tracking algorithm based on lightly nudging the MPP current set point, measuring the current and voltage, and determining whether the power produced has increased or decreased.

2. Hypertrophic conductivity. It measures changes in current and voltage to predict the effect of changing voltage using the system’s conductance – the slope of the power curve. When the perturbation and observation take steps of a fixed size and check that they go in the right direction, hyperconductivity modifies the step size depending on how far from the optimum.

3. Temperature. Used when there is no shade. We must measure the cell’s temperature and compare it with a given reference to determine the MPP.

Maximum power point tracking in grid systems

Solar panels are made of photovoltaic cells that generate electricity from the sun’s energy. However, the sun does not shine uniformly throughout the day, which means the panels do not receive adequate sunlight to produce electricity that can meet customers’ needs.

MPPT offers maximum energy harvesting from variable energy sources. This method is invariant concerning all constraints.

The MPPT checks the best power output a given PV system can offer. It then regulates the battery voltage and determines the best voltage to get the maximum current. MPPT establishes the optimal matrix voltage-to-current ratio for grid systems that feed maximum power to the inverters. Inverters are the primary device in a solar system that converts direct current into alternating current. They show much greater capabilities thanks to the MPPT function. This means they have a DC/DC converter, which increases the energy collection for the solar system.

The best conditions for the MPPT to do its job are when the sky is overcast, there is little sunlight on the ground, and the battery level is shallow.

MPPT types

Solar inverters have two different options: single or double MPPT tracking. The former offers board-level monitoring. Data is collected for the entire matrix, not individual strings or modules, even if the matrix contains multiple strings. In contrast, when tracking two MPPT channels, the inverter monitors power at the channel level instead of at the array level.

For solar systems with different azimuths, strand lengths, solar panels, or tilt angles, dual MPPT tracking offers significant benefits. Therefore, dual MPPT offers greater design freedom, especially for complex rooflines or designs with different modules. Unfortunately, this often comes at a higher cost but can pay for itself in more energy production.

What panels are best to invest in to take advantage of MPPT?

When choosing the proper solar panel installation in the Philippines, the house’s orientation relative to the sun and the panels’ power, efficiency, lifetime, weight, and dimensions should be considered.

In the case of power, the higher it is, the greater the efficiency of the installation. Power is measured in units of Wp (watt peak). Each 1,000 Wp will produce approximately 1 MWh of electricity per year.

The choice of panel will also be influenced by its service life. In the case of the highest quality devices, it can last up to 40 years. The performance warranty of such a panel is up to 25 years – which gives our customers the certainty that the efficiency will decrease by a maximum of 15% during this period.

The panels we decide to invest in will have different dimensions, e.g., 2108 x 1048 x 40 mm. The installation can be mounted both vertically and horizontally. The first type is cheaper and more common because it uses fewer mounting and anchoring elements.

Depending on the type of photovoltaic cells, the panels may be polycrystalline, monocrystalline, or amorphous. They differ in properties, efficiency, and ability to convert energy from scattered sunlight.

Monocrystalline panels have high efficiency under ideal conditions (angle of inclination and orientation of the roof relative to the sun). Although energy production is slower initially, these panels deliver it more efficiently.

Polycrystalline panels, on the other hand, have slightly lower efficiency but uniform power. Amorphous panels have a higher sensitivity at low solar irradiance. However, their efficiency is much lower, so it would be necessary to cover about twice as much area with them to achieve the same efficiency as in the case of the previous two types of installation.

Generally speaking, if you have a roof with an ideal orientation and inclination angle, monocrystalline panels will be more suitable. These panels are also the most commonly used in our latitudes. On the other hand, polycrystalline panels are more suitable for places where the light is more diffuse and falls from the side.