Chart showing the share of net metering in total generation, reflecting increased adoption of solar energy and reduced dependence on the grid. Source: NEPRA, AHL Research
If your electric bill went up in August even though your roof is covered in solar panels, you can blame Mother Nature for the price, but only to a point. It was hot, the sun was shining, but you still ended up paying K-Electric for grid power.
For example, my house is 1100 square feet and half of the roof has solar panels installed. In August, our solar generation was 1,304 kWh (kilowatt hours) and we ended up paying a much larger bill than usual. Let’s compare this to September, when our generation went up to 1503kWh and our bill went down.
The contribution of solar energy to Pakistan’s grid decreased in August. It provided just 0.7% of the total 14,218 GWh (gigawatt hours) produced that month, according to research firm Arif Habib Ltd.
“This August there was heavy rainfall and solar generation depends on sunlight levels,” said Dr Javed Iqbal, director of the Institute of Space and Planetary Astrophysics at the University of Karachi. “So the main culprit for poor solar generation was cloud cover.”
Read: Pakistan’s solar boom causes water shortages, fiscal problems
So the culprits are Sindh’s cloudy skies, high temperatures and discrepancies in the way solar energy is reported. “We see an increase in solar generation in September and we have also seen less cloud cover overall,” he added. “Therefore, it is safe to say that the low solar generation is mainly attributed to increased cloud cover.”
rainy days
August 20 and 21 were the wettest days recorded in Karachi. The weather station at the old Karachi airport terminal, for example, recorded 163.5 mm, the highest rainfall observed in that area since 1979, according to Anjum Nazir, spokesperson for the Sindh meteorological department. The least amount of rain was recorded in Bahria Town and Orangi Town, with 5 mm and 81 mm, respectively. The highest rainfall recorded in the city in these two days was
Heavy rainfall reduces solar irradiance, or the intensity of sunlight a surface receives per unit area. Low irradiance reduces photovoltaic (solar) generation. This means that the type of clouds over an area can affect the intensity of sunlight. The thick monsoon clouds depress the irradiance by high percentages.
Safety valves
Most parts of Karachi faced power outages during the monsoon. This is due to something called “standard anti-island protection.” It is a safety mechanism that prevents a power source from supplying the grid when it is down. Grid-connected inverters shut down during a grid power outage. Rooftop panels stopped exporting power to the grid and stopped serving homes until the grid stabilized, further reducing solar production.
Heat and dust levels
High heat levels also affect the efficiency of your solar panel’s operation. A group of researchers from Chengdu University of Technology and Imperial College London explain how the environment affects solar photovoltaic production. The panels lose about 0.5% per degree Celsius, which limits their productivity in warmer climates. This may be a smaller factor than cloud cover and blackouts, but it still affects midday solar performance.
The researchers also note that air conditions, such as pollutants and dust, can reduce solar energy generation. They can reduce solar generation by up to 60%.
Underestimated solar production
In a conversation with an official from an energy company, I learned that solar generation has two aspects: behind the meter (BTM) and net metering.
“BTM is when a customer uses solar generation solely for self-consumption. No prior approvals are needed for its installation, nor are there regulatory requirements for reporting,” he stated.
According to an energy snapshot from REN21, a global network focused on renewable energy construction, a growing portion of Pakistan’s solar boom is undocumented because in buildings with newer solar connections, when the power goes out, the building relies on solar energy to operate directly. Although this affects the measured solar production, the difference this would have is minimal, since this effect persists between months and would not only reduce the measured production of August.
