Re : A column about Quaid e Azam Solar power plant
12:22 PM
Recently, a friend of mine posted a link of an urdu column published by Daily Dunya newspaper written by a technically illiterate person on Quaid e Azam Solar Park (QASP). The subject matter was poorly understood by the writer which apparently is because technical aspects are quite different from 2+2=4. Since in Pakistan generation of electrical power through non conventional energy sources is a relatively new experience therefore, the quantum of false flags raised in this column could be large. In this blog post i want to argue technically about some stupid numbers provided in that column. The original column can be accessed by clicking here.
A lot has been written on the pros and cons of a grid tied solar PV system. The crux of the debate is that a typical solar PV plant has a non linear curve that needs specific algorithms to track the maximum power point in any given environmental condition. PV power plants are easy to install, as such they need a mechanical fixture normally referred as Balance of system (BoS), a dc-dc converter with an inverter in case of a multistage system and only a grid tied inverter in case of single stage inverter. For a layman perspective it is important to explain this important point before i proceed with the negation of this urdu column.
A lot has been written on the pros and cons of a grid tied solar PV system. The crux of the debate is that a typical solar PV plant has a non linear curve that needs specific algorithms to track the maximum power point in any given environmental condition. PV power plants are easy to install, as such they need a mechanical fixture normally referred as Balance of system (BoS), a dc-dc converter with an inverter in case of a multistage system and only a grid tied inverter in case of single stage inverter. For a layman perspective it is important to explain this important point before i proceed with the negation of this urdu column.
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| A typical charecteristic curve of a single PV panel. |
- Point # 1 : You go to a shop and order a PV panel. The trader will connect its mutimeter with the terminals of the PV panel and tells you "See it is 28 V ". And you purchase it making your mind that you need to have a DC-DC converter to step up the voltage and an inverter to make it useful for your home appliance. Result : PV panel will not work as desired because the voltage measured was open circuit voltage and nothing operates at open circuit.
- Point # 2: You go to the shop and ask the trader to measure the current. He connects his multimeter in series with the panel and shows you some reading telling you that it will produce even more current during noon. Correct, it will produce much more current but no device works at short circuit. Result : Your PV panel will not work as desired.
- Point # 3 : Always ask for the fill factor when purchasing a PV panel . The ideal value is 1.
- Point # 4 : PV is a nature dependent source of energy, meaning that the curve will vary with the variation in environmental conditions (irradiance and temperature). However, under any given environmental condition a single PV panel will have only one point of maximum power, and this is where Maximum power Point tracking is applied. Don't confuse yourself with the motor that tracks the position of sun. That arrangement is known as Sun tracking. For grid tied systems in northern hemisphere the sun is mostly on the south side therefore, in countries like Pakistan PV panels are fixed with their front facing the south side at 24.73 degrees.
These basics are not very technical yet provide important information about the nature of the PV based electricity generation. Now lets bust the quack facts presented in the column
- QASP dont have batteries :D
- OK. i know this :D is to laugh but seriously, someone should tell this so called seasoned COLUMNIST about the technical limitations of storing a peak power of 100 MW that too with the use of batteries. The added cost the losses in power storage and their maintenance and that too for nothing. No where in the world a PV power plant connected to grid has batteries connected to save the energy. This is for a very obvious reason, that a grid tied system has a grid connected as a load that can absorb maximum generated current throughout the day. Batteries are connected in stand alone PV systems because of two reasons; First, standalone PV system are deployed in a place where there is no other source of electricity e.g far flung villages in deserts and mountaintop huts, therefore, for the nocturnal use of electric appliances we need to have some backup. Secondly, it may happen that during the daytime the maximum available power exceeds the load connected with the PV system. Therefore, that extra energy is not wasted and is stored in a battery. Refereeing back to the statement made by author of "Kathra" it is rudimentary and lacks the basic understanding of PV systems. I would also like to mention that a grid tied solar PV plant such a QASP is designed to supplement the peak load during the day time. This helps in achieving the peak load profile of Punjab during the peak daytime loads.
- Electricity generated by the solar PV is not of same cycles. :ROFL
- Seriously, he should have asked some freshman of NFC IET Multan, or even a civil engineering student of BZU because they too study basic electricity course. Its a DC source that has zero frequency so whats the stupidity of raising the issue of cycles. A cycle is a period of a typical waveform. But unfortunately, author belongs to mass communication/journalism hence it is not his duty to read EE 1010.
- An easy way to convert DC into AC is to use inverter.
- Although i have been in the field of EE since 2001, i would be very much obliged if the columnist can tell me if there is any other way of converting DC into AC. For a technical aspect the conversion of electrical power from one form to another comes under the category of Power electronics and fortunately i am currently pursuing my doctoral studies in Power Electronics. Any device that converts the DC power into AC is referred as an Inverter. How conveniently Mr.Khalid Masood Khan has portrayed that there could be multiple ways of converting DC-AC and the most easy is the use of inverter.
- 20 percent losses occur during the DC-AC conversion
- I am sure that Khalid Masood Khan must have consulted some engineer who deals with the UPS based inverter. I am going a bit technical because this is the most rubbish claim made in this quack column. Following are the important points
- There are various configurations of grid tied PV system. If you see the figure below you can safely assume that the inverter referred in the column of Khalid Masood is perhaps the central inverter (although i am sure neither he nor his technical adviser know anything about grid tied inverters). How conveniently he has said that 20% power is lost in the process of DC-AC inversion. Mr. Khaled you know what ? science is moving at a very rapid pace ,no one likes to waste 20 MW out of the total 100 MW. And imagine where the losses will go, obviously they will be dissipated as heat so for your next column call some meteorologist and ask him to tell you some more quack science facts and write next column on temperature increase due to QASP.
- I being a doctoral student have studied a lot on the power conversion of PV systems. Let me quote the work of famous Prof. Dr. Jih-Sheng Li (Fellow IEEE and director Future Energy Elctroncis Center, Virginia Polytech Inst , USA) . He explained in his tutorial presented in Applied Power Electronics Conference 2012 that a typical central inverter has a peak efficiency of around 92%. The quack fact presented by Khalid Masood in his column are valid only for partial shading conditions, that i am sure Mr, Khaled has never thought in this wildest dreams. Therefore, this stupid argument that 20% current is wasted in the conversion is a over estimated false figure that highlights the lack of basic understanding of the system
- The discussion about the peak power of the QASP.
- Mr. Khalid is correct in this regard that the 100 MW figure is the peak power calculated under standard testing conditions of 1000 W/m2 at 25 C temperature, however, in love of the hatred against the government he presented another quack science. Pakistan is located in Southern hemisphere where the downfall of the peak available sunlight starts around 1300 HRS. How is it possible that under a falling irradiance the peak power is available after midnoon and then continues till 1400 hrs? The matter of fact is that during the summer the maximum available power is almost a flat line from 1030 to almost 230. Other than this time the irradiance curve is almost linear with rising and falling slope. In the nutshell the overall picture of QASP is deliberately made ugly by twisting the facts, spouting inflated losses in inverter stage and by doing pseudo economical analysis about the per unit cost without considering that how can we compare apples with the oranges. To understand the last lines please refer to this video lecture.
- I agree with the view point of Mr. Khaled on Piran Ghaib power plant and MESCO power station.
- About India, i have a lot to say but let me say thi for the time being that India has almost every kind of power plant in their country that helps their students being better engineers. Secondly, they do have indigenous facility of solar plant production that certainly has an effect on the cost of the project.
- Rest about you not being invited, i am so sorry for your inferiority complex. but a person like you who thinks technically it is just easy to start production of electricity using coal and that PV system is a nightmare, its justified. Keep writing against every project in Pakistan so that easy money and cheap fame can be harvested without sacrificing 20% losses in inverter stage.
Note: This blog was first published at pkpolitics.com and can be accessed here.
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