Questions & Answers

Microinverters are small devices installed on each individual photovoltaic panel that convert the direct current (DC) produced by the panels into alternating current (AC). Unlike central inverters, which convert the current from all panels collectively, microinverters optimize the performance of each panel independently. This is particularly beneficial when some panels are shaded, have different angles, or the installation consists of different types of photovoltaic panels.

Although microinverters tend to be more expensive, they offer greater flexibility and efficiency in non-ideal conditions, as well as higher long-term performance. For these reasons, Green Effect chooses to use Enphase microinverters.

The efficiency of photovoltaic panels decreases as the temperature rises. Each panel has a temperature coefficient of performance that indicates how much the panel’s efficiency drops for every degree above 25°C. Generally, panel efficiency decreases by approximately 0.3–0.5% for each degree increase above this temperature. Systems installed in hot climates may require better ventilation to avoid excessive heat buildup. In some cases, panels can reach temperatures as high as 100°C, which may cause cell ignition. Green Effect chooses to use equipment with superior temperature coefficients and, through the microinverters it employs, provides fire protection.

PID (Potential Induced Degradation) is a phenomenon that causes the gradual performance degradation of photovoltaic panels, triggered by voltage differences between the panel’s cells and the grounding. Over time, this can significantly reduce the panels’ efficiency. Preventing PID involves using cells made from resistant materials, incorporating special protection systems, and ensuring careful installation to minimize voltage differences.

In the past decade, intense price competition among panel manufacturers has impacted the quality of photovoltaic panels. Green Effect uses PID-free panels to ensure higher reliability and long-term performance.

Monocrystalline panels are made from a single silicon crystal, which makes them more efficient but also more expensive. Polycrystalline panels, on the other hand, are made from multiple silicon crystals, resulting in lower efficiency but more affordable prices. Monocrystalline panels perform better in limited spaces and low-light conditions, while polycrystalline panels are more cost-effective for larger projects where cost per kilowatt is a critical factor.

Nowadays, there are many new cell technologies beyond these traditional types. At Green Effect, we choose equipment that offers enhanced performance during periods of low sunlight, which, combined with microinverters, helps speed up the return on your investment.

MPPT (Maximum Power Point Tracking) technology is integrated into inverters to optimize energy conversion. The MPPT continuously monitors lighting and voltage conditions and adjusts the voltage received from the panels to maximize energy production. This ensures that the system always operates at its best possible efficiency, even under changing sunlight, shading, or temperature conditions.

A typical residential central inverter has two MPPT trackers. By using microinverters, it’s as if you have one MPPT tracker for each solar panel on your rooftop!

1. Οι κύριοι παράγοντες που επηρεάζουν την αποδοτικότητα των φωτοβολταϊκών πάνελ είναι:

   • Τεχνολογία των κυψελών: μονοκρυσταλλικές, πολυκρυσταλλικές, λεπτής μεμβράνης κ.α.

   • Θερμοκρασία & αερισμός: οι υψηλότερες θερμοκρασίες μειώνουν την απόδοση των πάνελ.

   • Σκίαση: ακόμη και μερική σκίαση μπορεί να μειώσει σημαντικά την παραγόμενη ενέργεια.

   • Ρύπανση και σκόνη: συσσώρευση σκόνης πάνω στα πάνελ μειώνει την απορρόφηση ηλιακής ακτινοβολίας.

   • Γωνία κλίσης και κατεύθυνση: η σωστή τοποθέτηση των πάνελ σε σχέση με τον ήλιο βελτιώνει την απόδοση.

   • Ποιότητα υλικών και κατασκευής: τα ποιοτικά πάνελ και υλικά εξασφαλίζουν μεγαλύτερη αποδοτικότητα και διάρκεια ζωής.

   Στην Green Effect, λαμβάνουμε υπόψη όλους αυτούς τους παράγοντες κατά τον σχεδιασμό και την επιλογή των υλικών, προσαρμόζοντας τη λύση ανάλογα με τις ειδικές ανάγκες κάθε εγκατάστασης.

On-grid systems are connected to the electrical grid or use the grid as a backup. They are usually categorized based on their size and mode of operation, as there is a significant difference between self-consumption systems and systems designed for energy production and sale. Off-grid systems operate independently of the grid and require energy storage systems (batteries) to function. They are ideal for remote areas without access to the electrical grid.

All of the above require specialized knowledge and expertise to such an extent that it is impossible for one company to handle everything. Imagine if your home plumber claimed to design irrigation systems for fields, pools, and large storage projects—would you trust them? Green Effect specializes in small to medium-sized building self-consumption systems and does not engage in anything else.

Modern panels and new central inverters are smarter than older ones and usually manage to successfully handle some types of shading. This typically happens because the panel, or part of it, is ‘disconnected’ from the string, stopping it from negatively affecting the entire system. However, this also results in the loss of even the small amount of energy that panel would have produced.

Moreover, there is a wide range of shading scenarios that neither modern panels nor inverters can effectively address—for example, a pole, a bird, bird droppings, or a leaf. Fortunately, microinverters, which convert the direct current (DC) from each individual panel into alternating current (AC), provide the solution for shading issues.

For these reasons, Green Effect chooses to use Enphase microinverters.

Solar panels of different sizes require the same rooftop space to cover a home’s energy needs. For example, 10 panels of 600 Watts will produce the same annual kWh as 15 panels of 400 Watts. This happens because a panel’s efficiency per square meter depends on the cell’s performance and the percentage of solar energy converted into electricity.

In developed countries abroad, installing large-sized panels on rooftops is prohibited for safety reasons and out of respect for the workforce. Additionally, larger panels endure more stress from environmental conditions, which reduces both their lifespan and performance. Imagine holding a large umbrella in a storm while your partner has a small one — which umbrella do you think would break first?

For these reasons, Green Effect chooses to use smaller panels in its installations.

In every geographical area, different conditions prevail. For example, to achieve maximum performance in kWh per installed kWp annually, the optimal tilt angle of panels in Attica is 27 degrees, facing south (180°). However, it has now been proven that maximizing total annual energy production is not the most important factor when designing a system. What really matters is ROI (Return on Investment) or faster payback time.

The price of energy relative to the time of day, consumer habits, shading, and self-consumption rates are far more important factors than just maximizing annual kWh production. What’s the point of producing more energy at 1 PM and getting paid 1 euro per MWh when at 6 PM you could be paid 15 euros per MWh?

At Green Effect, we take all these factors into account when designing a photovoltaic system, which is why our installations achieve significantly higher ROI and faster payback times.