How Solar PV Works

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Measure Solar PV Efficiency

How Solar PV Systems Work:

Inverters, Batteries, Shading & Monitoring Explained

Solar photovoltaic (PV) systems are becoming the go-to solution for clean, renewable energy in homes and businesses. But how do they actually work? Whether you’re a homeowner considering an installation or a solar installer building your knowledge base, this guide explains how solar PV systems generate power, how shading and system design affect efficiency, and how to get the most from your investment.

What Is a Solar PV System?

A solar PV system converts sunlight directly into electricity using photovoltaic cells, typically made of silicon. When sunlight hits these cells, it excites electrons, generating direct current (DC). This DC electricity is then converted into alternating current (AC) by an inverter for use in your home or for export to the grid.

How Solar Cells Are Wired Together

Individual solar cells produce about 0.5–0.6 volts each. To make them practical:

    • Cells are wired in series, which increases voltage

    • Parallel wiring increases current (amperage)

These cells are assembled into panels, typically with 60, 72, or 96 cells, producing 250–450 watts per panel under ideal conditions with a voltage of around 30 volts. A variety of solar panels are manufactured to suit different applications, such as 3.5-volt panels for charging phones and ones used to help power your home. The price of one 400 watt solar panel is around €70  (2025 prices).

What Are STC (Standard Test Conditions)?

Solar panels are rated under Standard Test Conditions (STC) to ensure uniformity and help you compare one product against another. This ensures that one can compare the performance of one supplier against another when you go to buy a solar panel:

    • Solar irradiance: 1,000 W/m²

    • Cell temperature: 25°C

    • Air Mass: 1.5 (when the sun is shining at an angle of 48 degrees from the ground elevation, which approximately equals an air mass of 1.5)

How do solar panels perform in real life.

Sometimes you will see more power generated from solar panels when the sun is higher in the sky than the STC conditions above. If you can mount your solar panels perpendicular to the sun for most of the day as the sun moves across the sky more power will be generated. These laboratory STC conditions can occur in real life, but expect less output under actual outdoor conditions due to the factors mentioned below such as design factors or shading for example. If there is cloud and sun at the same time you may see the power increase because the sun is reflected from the clouds and the direct light falling on the solar panel increases. If there is only cloud then there will be less power because the sun can not shine directly on the solar panel. If the solar panel points directly at the sun (perpendicular to the sun) there will be more power generated . This is why pyranometers are used to measure the power of the sun (irradiance) in watts/m2. With meters like the IN-SOL pyranometer from Solar PV Innovations the input power and output power can be calculated. One can also use the IN-SOL meter to help decide on the best position and angles to site your solar panels . If one enters values into the free calculator on this site one can see the effect different system factors have on the power you generate. In the winter the sun (if it shines) is at a very low angle in the sky (around 12 degrees).

Factors to consider for the design of your solar PV system.

Do you want to maximize winter sun or ballance your system for both summer and winter sun. As mentioned above the sun tracks different angles over the seasons.One can download a free app such as Sun Surveyor lite (free) to track and simulate where the sun will be at different times of the year.  If one can mount solar panels to get the most from the winter and summer sun then you will be generating power for most of the day while the sun shines. In Ireland some panels pointing south east and some pointing south west can yield the most power. This can be done with PV systems that have different strings in the inverter. One would need a string in the inverter for south east and another for south west panels. Mounting panels flat is also an option but the angle needs to be at least 3 degrees so that water can drain from them. Expect to clean the panels more frequently because more dirt/dust will collect on the panels when they are flat.

Mounting

There are multiple mounting systems available to mount solar panels. Ground mounting is an option if one has space as they will be easier to maintain. All types of roof mounting systems are available for metal, flat or traditional roofs. Vertical mounting is another option as garden fencing for example. Automatic solar tracking mounts are also available but the cost and maintenance is prohibitive. Keeping things simple is always the best option. 

Central Inverters vs Microinverters vs Power Optimizers

Central (String) Inverters or Hybrid Inverters

In traditional setups, panels are connected in series (forming a “string”) and feed into a central inverter. If you are installing solar panels on your roof and some panels are south/east-facing while others are south/west-facing, you should use two strings. The reason for this is that the power may be greater in the morning for string 1 while the other string is shaded. If only one string is used, the output power will be restricted because the shaded panels will generate less power. A way to understand this is to think of what happens when one stands on a water hose stretched out on your lawn -the water will be reduced, this is similar if all your solar panels are stretched out in a line. The power will be reduced on the panels that are shaded thus affecting all the other panels. 

Pros:

  • Lower upfront cost
  • Simpler system architecture

Cons:

    • One shaded panel can reduce output across the entire string

    • Limited visibility into individual panel performance (unless using power optimizers)

Microinverters

With microinverters, each panel has its own inverter, converting DC to 230V AC or 110V AC right at the source.

Pros:

    • Panels operate independently – ideal for shaded or complex roofs

    • More detailed monitoring: you can track the performance of each panel individually
    • Less chance of fire because they use low voltage and alternating current (AC).

Cons:

    • Higher upfront cost ( approximately €130-2025)

    • More components that could potentially fail

Power Optimizers (for Central Inverter Systems)

Power optimizers are installed at the panel level and work with a central inverter. They:

    • Maximize the energy output of each panel individually

    • Reduce the impact of partial shading

    • Provide per-panel monitoring capabilities (similar to microinverters)

Solar Batteries and Inverter Options

If you’re considering a solar battery, you’ll need the right inverter setup to match. Here are your options:

Inverter Type Description Best For
Hybrid Inverter Combines solar and battery management in one unit New systems
AC-Coupled Separate solar and battery inverters Retrofitting existing systems
DC-Coupled A battery typically has its own inverter High-efficiency setups
 Microinverters  The battery typically will have its own microinverters,   High reliability and safer.
     

Tip: If you’re installing solar now but want batteries later, choose a hybrid inverter for easy expansion.

How Shading on Your Solar Panels Affects Solar Output

Shading is a major cause of reduced system efficiency. Common causes include:

    • Nearby trees

    • Chimneys or flues

    • Leaves, debris, or bird droppings

Why Shading Matters for Solar PV

In string inverter setups, even partial shading on one panel can drag down the performance of the entire system on that string. Shading can also lead to hot spots that degrade panels faster over time.

Solutions:

    • Use microinverters or power optimizers to isolate affected panels

    • Perform a comprehensive shading analysis before installation

Monitoring Solar PV Efficiency with IN-SOL Pyranometer

Monitoring your solar PV installation ensures you’re getting the output power you paid for. Here’s how:

Step 1: Measure Solar Irradiance

Use an IN-SOL Pyranometer to measure the actual solar radiation (in W/m²) reaching your panels. Position it with the same orientation and tilt as your solar array.

Step 2: Use the Calculator

Visit www.solarpvinnovations.com and scan the QR code to open the app on your phone or click on this link.

Enter data about your system and pyranometer readings to calculate:

    • Expected output based on current conditions

Efficiency Formula

This calculation takes into account the efficiency of the solar panel, the glass area of the solar panel, the temperature of the solar panel, and the power you are receiving in kW for that solar irradiance value shining on the solar panel:

 

Efficiency (%) = (Actual System Output) / (Theoretical Input) × 100

 

Final Thoughts & Checklist

Solar PV is a long-term investment. Make it count by choosing the right configuration and monitoring tools.

    • ✓ Assess shading before installation

    • ✓ Choose microinverters or power optimizers if shading is a concern

    • ✓ Plan ahead for battery integration with hybrid inverters

    • ✓ Use condition monitoring for long-term efficiency tracking

👉 Ready to get started? Visit www.solarpvinnovations.com for tools, calculators, and expert advice on system performance and optimization.