Tips On How To Minimise Rooftop Underperformance

The Physical Causes Of An Underperforming Solar System

When designing a system on PV software or facilitating an on-site inspection, you can sometimes be faced with certain issues that affect the optimisation of your solar system.

Following are some of the main things that affect the optimisation a solar system on a rooftop:

1. Multiple Roof Directions

Sun irradiation is mismatched on a string of panels.

2. Shading Caused By An Antenna Or Chimney

Rooftop objects such as chimneys, satellite dishes, or TV antennae can interfere with the overall performance of PV panels by casting shadows.

3. Shading Caused By The Home Of A Neighbour

Houses that have shade caused by their neighbours home or any other building, should consider one of the shade-management systems to lower underperformance.

4. Shading Caused By Bird Droppings, Leaves, Or Trees

Bird droppings often lower panel output which affects efficiency. An optimised system accounts for this issue, until cleaning.

These are all scenarios that result in a mismatch when it comes to panel generation. This often results in dragging down the performance of the system for either an “array of panels” or the whole string. When panels are connected along a string in series, these should be operating from a mutual current. If one or more of these panels generates less power, the entire array usually suffers.

To explain this phenomenon, think about the analogy of water pipes. The water that flows through a pipe is usually constant, similar to the current that runs through cell strings. If a mismatch occurs between the panels, this is similar to a partial blockage in a water pipe which causes the flow rate to slow down, which in turn affects the flow of water to the other pipes that connect to it. In the same way, the current that runs through the string will start to reduce when a mismatch occurs.

Why Is It Important To Pay Attention To Shading?

1. Heating Problems

Fallen leaves reduce the output of the panels which prevents sunlight from reaching the panels in specific areas that negatively impacts efficiency.

2. Roof Direction

According to market research, around 2 out of 10 homes have to factor in roof direction and shading. The power output reduces and a mismatch could also lead to extensive damage to a panel known as hot-spot heating. In extreme cases, this can even result in a fire. Using the analogy that was mentioned above, think about the blocked water pipe. When the pressure starts to build up the pipe might explode as the pressure increases.

3. Rooftop Obstacles

Obstacles that cast shade across the panels such as vents, pipes, and chimneys can negatively impact panel performance. This is an important consideration when planning the panel layout for your home.

How To Gain A Better Yield And Lower Performance Loss

1. Panel Level Solutions

The traditional panels connect in series and come assembled with full cells. See the electrical diagram below that displays the interconnecting sequence on the solar cells in the panels.

The half-cut solar panel is regarded as 2 traditional independent panels (all the half-cut cells connected in series) that are parallel in connection.

If shading is blocking an entire column, performance will reduce similar to the full-cell panels. Around 1/3 of the performance decreases, causing the temperature of the cell to rise.

When shading is blocking an entire row, this means that only 50% of the panel performance will be affected. The other half-panel will continue to operate as normal in comparison to traditional panels that lose all their power.

When shading has only blocked a single cell, only 1 string is affected (1/6 loss) when compared to full-cell panels that lose around 1/3 of their power.

2. Vertical Panel Arrangement

In Australia, less than 90% of the panels that are installed on roofs are in a vertical direction.

3. Half-Cut Panels Vs Full Panels

The half-cut panels feature 6 separate cell strings, this offers improved partial-shade tolerance. This means that when 1/2 of a panel is in shade, the remaining half is still able to operate.

4. Shingled Solar Panels

The shingled panels feature a different type of solar-cell layout. For example, with LONGi HiMO-X the solar cells come in 6-strings and these strings work independently and connect in parallel. When shading has blocked one cell or an entire string, performance levels only drop by 16.7%, when compared to the traditional panels that lose about 33.3%.

5. MLPEs (Module Level Power Electronics)

MLPE solutions are one of the other loss minimisation methods for solar systems. Both power optimisers and micro-inverters can assist the solar panels to operate independently, which means the affected panel or panels will not drag down the performance of the entire system. An MLPE solution is another effective way to minimise the loss of efficiency in a solar system.

If you are looking for a trusted local solar company in Hervey Bay, please contact us today at GCR Electrical Systems on (07) 4120 7004 or leave an enquiry if you would like more information about our solar installation services.