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May 18, 2015

A solar revolution in Pakistan

Opinion

 
May 18, 2015

Pakistan has taken its first step towards the solar revolution that is gripping the entire world. Pakistan’s energy mix, for the first time in the country’s history, has incorporated solar power instead of relying solely on conventional methods of power generation. While this momentous step is a source of pride for many, others have, as is customary in Pakistan, focused on the negative aspects of solar power in Pakistan – without there being any real basis for their criticism.
It is important to understand that the incorporation of solar power projects in the energy mix is an advantage, and not a menace as some may suggest. The primary advantage is that the fuel is free; there is no fuel risk or fuel cost that is incurred through the lifetime of the project. Moreover, in the case of solar energy, the burden on foreign reserves due to import of fuel is also absent, and there is no effect on the rate of inflation.
What solar power plants require, though, is a one-time investment with a quick payback period. For instance, the 100MW solar power plant in Pakistan has a payback period of five years on its investment. This is significant given that negligible cost is incurred on operation and maintenance (O&M) of the solar plant. Further reduction in the cost is possible if investors are provided with better financing and cheaper loans by financing institutions.
Despite these advantages, it is imperative to understand that renewable energy plants including solar power projects are innately different from conventional power plants, and comparing the two is akin to comparing apples and oranges.
For instance, power produced from solar is largely dependent on irradiation. This is the inherent nature of the technology: no sunlight equals zero power. Were the sun to shine 24 hours a day throughout the year, solar power would have been the sole source of power generation in the world. As nature has it, this is not the case. Solar power plants can only

harness the sun from sunrise to sunset, and this duration too varies throughout the year.
This simple fact is not taken into account when the output capacity of solar power projects is compared with conventional ones, and even technical experts tend to overlook this fact when analysing the impact of solar power on the energy mix.
Consequently, some experts assert that over a period of 24 hours a day, a 100MW solar power project effectively produces less than 20MW. While this number seems true, one has to first look into the basis of this analysis.
The figure is derived using an analysis known as Capacity Utilisation Factor (CUF): the ratio of the total energy exported divided by the rated output power in 8,760 hours (24 hrs x 365 days) of the year. This compares the power produced in a year to what the maximum power could be produced if the plant were to run continuously day and night for 8,760 hours.
But can this analysis be extended to solar power projects? The answer is a resonating no! Solar power plants do not, and cannot, operate for 24 hours a day.
This technology can only be used for 10-16 hours a day depending solely on the sunshine available. It makes no sense to compare a power plant that has a maximum capacity of running 12 hours at average with a power plant that can, at its maximum, run for 24 hours a day. This is similar to claiming that a human is only 33 percent efficient because he works for eight hours a day, and the remaining time is ‘wasted’ in resting, eating and other activities.
Moreover, the calculation of capacity utilisation factor does not take into account environmental variables such as irradiation, wind speeds or temperature. For solar panels, increased temperature reduces their efficiency and increased irradiation increases the power output. Such environmental factors play a negligible role in the power produced by conventional power plants, but have to be taken into account for solar power projects.
Instead of the CUF analysis, solar power plant efficiency is globally calculated using a term known as Performance Ratio (PR). This is the ratio of the total power output to the irradiation available on solar modules over a specific time period.
This is a much more effective method of analysis used throughout the world for solar power plants which acts as an effective quality control instrument. It gives direct feedback of what output power was achieved versus what could have been achieved considering the given climatic conditions. According to international best practice, the PR of a solar power plant must be greater than 70 percent.
Another important difference to be noted is that the electricity generated from solar panels is DC as opposed to the AC power used in the homes and industries. Solar power plants convert this DC power to AC using inverters, and there is an insignificant power loss during this conversion. However, drawing room criticism would find such insignificant loss to be the gossip of the town.
Inverters and transformers in general have very high efficiency (upward of 90 percent) which can be verified by inverter manufacturers. Moreover, the inverters are based on feedback from the grid and regulate the frequency of the output power depending on this feedback. This means that the grid frequency is not affected by solar power projects as some critics of solar power projects have propagated.
On the contrary, solar power plants improve the stability of the grid. The inverters and the Static VAR Compensators (SVC) used in the solar power plants are able to inject reactive power quickly and efficiently based on the feedback from the grid. This reactive power is required when there is unbalanced load, and the SVCs are able to improve the grids dynamics while reducing line losses.
Grid stability can be further improved using on-grid distributed solar power plants close to load centres. For instance, industrial estates are major customers of the national grid, and because of their inductive load such as large motors, adversely affect the grid’s power factor. With the introduction of solar plants close to such load centres, the power factor can be improved dramatically which in turn will reduce the grids line losses while improving the grid stability.
Further relief to Pakistan’s overburdened grid can be provided by promoting net-metering under which users can consume solar power through the day and sell the excess to the grid. In return, the grid can use this power evacuated from the consumer to offset the electric energy it provides to the consumer during the night. The grid can hence be relieved during the day while at the same time the consumer can benefit from the excess energy produced: a win-win scenario.
Solar power has similar applications off-grid and can be virtually installed anywhere with ease ranging from a single module to several hundred thousand. Due to its modular nature, a solar power plant of 250W solar modules can generate peak power of any multiple ranging from 250W to several mega watts.
For Pakistan, both solar power projects and conventional projects are the need of the time. A shortfall of over 4,000MW cannot be overcome by renewable energy alone, and there is a dire need to revive or set up new conventional power projects to meet the base load. At the same time, the role of renewable energy in Pakistan must not be downplayed based on irrational assumptions. After all, renewable and conventional sources of energy complement each other towards a single goal – the resolution of the energy crisis in Pakistan.
The writer is a Lahore-based freelance contributor.
Email: [email protected]