Graph showing net meter share of total generation, reflecting increased use of solar energy and reduced grid dependency. Source: NEPRA, AHL Research
If your electricity bill went up in August, even though your roof deck is covered in solar panels, you can blame Mother Nature for the price tag, but only up 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 sq m and half of the roof has solar panels installed. In August, our solar output was 1304 kWh (kilowatt-hours), and we ended up paying a much larger bill than usual. Compare that to September when our generation went up to 1503 kWh and our bill dropped.
Solar energy’s contribution to Pakistan’s grid fell in August. It supplied just 0.7% of the total 14,218 GWh (giga watt-hours) produced that month, according to research firm Arif Habib Ltd.
“This August had heavy rains, and solar generation is dependent on the levels of sunlight,” said Dr. Javed Iqbal, Director of the Institute of Space and Planetary Astrophysics at the University of Karachi. “So the biggest culprit for poor solar generation was cloud cover.”
Read: Pakistan’s solar boom triggers water stress, fiscal woes
Sindh’s cloudy skies, high temperatures and inconsistencies in how solar energy is reported are thus to blame. “We’re seeing an increase in solar generation for September and we’ve also seen less cloud cover overall,” he added. “So it’s safe to say that low solar generation is mostly attributed to higher cloud cover.”
Rainy days
August 20 and 21 were the wettest days on record in Karachi. The weather station in Karachi airport’s old terminal, for example, had 163.5 mm, the highest rainfall seen in this area since 1979, according to Anjum Nazir, spokesperson of the Sindh Meteorological Department. The lowest amount of rainfall was recorded in Bahria Town and Orangi Town, with 5 mm and 81 mm respectively. The highest rainfall recorded in the city on these two days was
Heavy rain lowers insolation, or the strength of sunlight received by a surface per second. area unit. Low irradiance slows photovoltaic – solar energy – generation. This means that the kind of clouds over an area can affect the strength of sunlight. Thick monsoon clouds suppress the irradiance in high percentages.
Safety valves
Most of Karachi faced power cuts during the monsoon. This is because of something called “standard anti-island protection”. It is a safety mechanism that prevents an energy source from supplying the grid when it is down. Grid-tied inverters shut down during a power outage. Rooftop panels stopped exporting power to the grid and stopped serving homes until the grid stabilized, further slowing down solar power.
Heat and dust levels
High heat levels also eat away at how efficiently your solar panel works. A group of researchers from Chengdu University of Technology and Imperial College London explain how the environment affects solar cell production. Panels lose around 0.5% per degrees Celsius, limiting their productivity in warmer climates. This may be less of a factor than cloud cover and precipitation, but it still affects midday solar output.
The researchers also point out that air conditions, such as pollutants and dust, can shrink solar energy production. They can reduce solar energy production by as much as 60%.
Underreported solar production
In conversation with a power utility official, I learned that solar generation has two aspects: the back meter (BTM) and net metering.
“BTM is when a customer uses solar energy solely for their own consumption. No prior approvals are required for installation, nor is there any legal requirement for it to be reported,” he said.
According to an energy snapshot by REN21, a global network focused on building renewable energy, a growing part 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 power itself directly. While this does affect solar’s measured output, the difference this would make is minimal as this effect persists between months and would not only lower August’s measured output.
