Completely oblivious of its surroundings, our single most, massive source of energy, the sun, produces power that amounts roughly up to 3.85x 1017 GW — that has contributed to a substantial amount of the world’s power needs, as the cost of the developing technology has gone down over the past years.
Pakistan’s location makes it an ideal country to tap into the solar resource, having an average annual irradiation of 6kWh/m2/day, to fulfill its power needs and add an increasing chunk to its economy.
The topography of Pakistan varies greatly ranging from the frostiest of the areas to sites realizing a 50 degrees Celsius. The variation of environment factors, such as ambient temperature, humidity, precipitation, wind, and the solar irradiance encourages solar PV system designers to select the optimal PV and storage technology and vary designs according to application and location’s environment to optimize power output, increase system efficiency and decrease the levelized cost of energy (LCOE) to make solar accessible and practicable.
The 100-MW Quaid-e-Azam Solar Power Plant, at Bahawalpur, was the first grid-connected IPP that was installed in 2015 and has been operational since August 2015, exceeding expectations and demands by the National Electric Power Regulatory Authority in terms of producing energy, GWhs, for the months with optimal solar irradiance and temperatures. The plant is on its way to become the world’s largest with a peak capacity of 1,000 MW, installed with polycrystalline PV modules. The plant is not only intended to help the country meet its power requirement, decreasing the power deficit, but also to provide a model for foreign companies to invest in solar PV and earn profits up to huge margins.
The location of the plant bears high temperatures, moderate to high levels of relative humidity with low rainfall and ample solar irradiation — and annual of 1860 kWh/m2. The PV module selection exhibits a 15.6 percent efficiency and a temperature co-efficient of -0.41 percent/C — indicating the thermal loss of power generated by solar PV modules as temperature increases above standard test conditions (STC) of 25 degrees Celsius. The 100-MW installation also suffers excess soiling due to sand storms and unsettled dust in the ground.
The performance of a solar PV installation is highly dependent on the environmental factors. As the environmental parameters change, the power output varies. High solar irradiance causes an increase in output; however, increase in ambient and panel temperature has a decreasing effect. The intermittent clouds or days with higher humidity tend to hinder the energy production as high energy wavelengths (shorter wavelengths) of the electromagnetic spectrum are absorbed in the atmosphere, leaving diffused radiation reaching the earth consisting of low energy wavelengths, not enough to fulfil the bandgap of the PV device.
Similarly, a change in declination angle of the earth toward the sun causes a variation in power production throughout the year — requiring an optimal tilt of solar PV modules. The PV plant produces optimal energy during and around equinoxes, as the major deciding parameters irradiance and temperature are moderate and closer to STC.
With commercialization of numerous other PV module technologies, the PV designers have a lot of variety to pick from PV module technologies. The 100-MW PV plant’s power production can be optimized. Analyzing the environmental factors of the plant’s location, the thin film cadmium telluride (CdTe) would have been a more beneficent technology for energy production. The First Solar, 112.5-Wp module was used in the analysis, with an efficiency of 15.6 percent, matching exactly the efficiency of the Cry-Si
module used, implicating almost the same amount of land required for the deployment of this technology, which was not possible due to lower efficiencies of the CdTe in the past.
Spectral Response of Different PV Technologies
Source: European Commission, Joint Research Centre, Via Fermi 2749, Ispra 21027, Italy
Simulations and calculations run to analyze the effect of replacing the crystalline-silicon technology with thin film CdTe prove that, the first-year production of the plant would have produced 13 GWhs more than the Cry-Si production — an increase from 160.2 GWh to 174 GWh. Over the span of 25 years — an excess of 276.2 GWhs could have been extracted from the solar PV plant. Owing to these figures, an excess of US $38.8 million could have been added to the collected revenue — a net increase in profit of US $3.2 million per year. Under these production values, the LCOE of the plant reduces from $0.14 to $0.13. The net present value of the plant increases up to 60 percent of its initial rate. The stakeholders not only earn a much greater profit, but also ensure a larger energy grid-injection.
The performance ratio of the solar PV plant increases from 80.6 percent to 83.3 percent as a result of more energy production. The annual specific yield also sees a rise from 1602.3 kWh/kWp to 1739.6 kWh/kWp.
The excess electricity production owes to better temperature performance of the CdTe compared to Cry-Si, temperature coefficient of -0.34 percent. The ambient temperature is expected to reach as high as 43 degrees Celsius, causing the PV module temperature to rise up to 70 degrees Celsius at occasions. The CdTe module has a better spectral response — the ratio of the current generated by the solar cell to the power per wavelength incident on the solar cell — in hot and humid conditions and in cloudy weather as well.
Under high humidity or when overcast by clouds, the lower wavelengths (high energy wavelengths) of the electromagnetic spectrum are absorbed in the atmosphere; as compared to Cry-Si, the thin film CdTe has a much higher spectral response to the incident spectrum of lower energies thus producing more power in those times, relatively to Cry-Si. Similarly, the thin film CdTe performs for a much larger part of the day due to improved performance at dawn and dusk, owing to the absorption of lower energy wavelengths because of better spectral response, contributing more kWhs throughout the day.
The efficiencies for the thin film technology have been improving, which has been one of the major reasons of the technology’s lesser market share in PV installations on a global level. Although the 100-MW installation at Bahawalpur has been performing well for the past year, an additional value could have been added using the CdTe technology. The remaining 900 MW is being added to the Quaid-e-Azam Power park, with the same polycrystalline technology. If the thin film CdTe were to be used for the upcoming phase of 300 MW out of the 900 MW installation, one could practically observe the plausible outcomes the technology holds, for irradiance-rich locations such as Pakistan. Not to mention, a great potential market for the key global market drivers of thin film technology.
The data, for analyses, was extracted from the QA Solar Plant website and the 8.2 feasibility report, available on the AEDB website. The methodology of the analysis consisted of simulating the Cry-Silicon design and then compare the results with the output of the Thin film CdTe. The simulations were run on the ECAT tool available on the First Solar website and on Valentin Software PV*SOL. MATLAB was used to calculate certain parameters for computing input parameters and results.
The difference between the 8.2 report results and the PV*SOL simulation in terms of Energy injection to grid was -0.15% and in terms of revenue generation over the period of 25 years was 0.5%. The NPV and LCOE increase due to Thinfilm production were calculated on basis of PV*SOL simulation. Similarly, in terms of excess revenue generation, the difference between the ECAT tool results and the PV*SOL simulation (Thinfilm) is of -0.6%. Complete cash flow analyses, simulation reports, list of assumptions, datasheets of products, calculation of results and sources of data are available and proof for the excess energy and revenue generation can be provided.
This article was originally published on LinkedIn and was republished with permission.
Lead image credit: NREL