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Design Of A PV-Diesel Hybrid System

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Published: Wed, 21 Feb 2018

Design Of A PV-Diesel Hybrid System And Its Comparison With Grid Connected System In Pakistan

1. Project Background And Introduction

Introduction

The project with respect to this thesis is to design a PV Diesel hybrid system and to compare it with already existed grid connected system. This system is designed for a Jamia Masjid (Islamic center) in Pakpattan, Pakistan. The exact site of the project is a colony of Pakpattan which is in the south-west of the city Pakpattan. The Pakpattan city is situated around 161 Km south west to Lahore. The climate and weather data is almost same for Lahore and Pakpattan. Furthermore it will be first project of its own nature in this area and it will help to design the systems for the residential areas by which a common person can get benefits and get rid of power failures.

Pakistan is located between latitude 24 and 37 degrees North and longitude 62 and 75 degrees East. Pakistan has Afghanistan in the north-west, Iran on west boarder, India is on the east, China in the north and the Arabian Sea is on the south. Pakistan is ageographical centre of the Asian Continent because it builds a type of bridge between Far East and Middle East; also it has a continental type of climate which can be characterized by extreme variations of temperature. Generally the climate of Pakistan is arid, means very high temperature in summer and low temperatures in winter. High altitudes change the climate in the freezing northern mountains which are covered with snow.

There is little rainfall. There are some differences exist distinctly in various locations, e.g. the coastal line along Arabian Sea is usually under warm conditions, whereas the Karakoram mountain range and some other mountains of far north are so cold, completely frozen and covered with snow that these are only visible and accessible by some international world-class climbers for a couple of months of May and June of each year. The variation of daily temperature could be 11 0C to 17 0C but in winters the minimum mean temperature is about 4 0C in January.

Pakistan has tremendous recourses of energy but unfortunately due to mismanagement out of 170 million population just 65-70% has access to electricity. Demand is more than supply of energy to residential and industrial sector. Currently Pakistan is facing 3000 MW of power storage and it is expected that in year 2010 the demand will exceed supply by 5500 MW. The current power and electricity demand and supply gap shows that there is a big need to increases the current power generation capacity in Pakistan.

Aim Of The Thesis

The main aim of the project is to explain the design phase of a single home PV system. The procedures and details of the design are presented with step by step. There are main following aims which are supposed to be fulfilled by this thesis.

a) To go through and grab the core knowledge of the designing process.

b) To get familiar with different tools used for designing and make selection between them.

c) Beyond from bookish knowledge, get to know some real and practical aspects of different PV systems and projects.

The body and structure of the thesis is mainly divided into four phases.

a) Calculation of the primary load for this specific project with the help of PVSYST version 4

b) Division of the load to PV and Diesel Generator according to boundary conditions and design parameters.

c) Economical and technical look on already existed grid connected system.

d) Comparative study between this newly design system and already existed grid connected system in terms of economics, availability and life time

World Energy Situation

There are different factors which effect and play an important role in the consumption, demand and availability of energy, for example the consumption by individual user and business is being increased, everyday growing population and new government policies are some of these factors. But the fossil fuels are exhaustible. There are two aspects of the fossil fuels, 1st is their availability and 2nd is those harmful environmental impacts which appear after using and burning of these fossil fuels. It is equally harmful for the present generations as well as for future generations. But with the passage of time more and more people and governments are getting awareness about these impacts.

The current energy demand projections can be seen from the facts and figures provided by World Energy Administration (EIA)

“The total world energy consumption increases from 472 quadrillion Btu in 2006 to 552 quadrillion Btu in 2015 and 678 quadrillion Btu in 2030—a total increase of 44 percent over the projection period”

Renewable Energy Situation Of The World

When the first Renewable Global Status Report was published in 2004, many indicators have shown dramatic gains. In the last four years from the end of 2004 to the end of 2008, solar photovoltaic capacity increased six times which is more than 16 gigawatts (GW). Wind power capacity has been increased 250 percent to 121 GW; the total power capacity from new renewable recourses has been increased 75 percent to 280 GW which includes significant gains in small geothermal, hydro, and biomass power generation. During the same period of time, solar heating capacity become double to 145 gigawatts-thermal, while the biodiesel production has been also increased six times to 12 billion liters per year and ethanol production doubled to 67 billion liters per year.

The annual percentage gain for the year 2008 was also very amazing and more dramatic. The growth in Wind energy was 29% and grid connected solar PV by 70%. The capacity of utility scale PV plants also increased during this period. Solar hot water systems also grew by 15%. All around the world the governments are changing the policies about the future energy crises and energy markets and policy. In this race the United States of America became the leader and invested $24 billion for new capacity which is 20% of the total global investment. The United States is also leading in adding the total wind energy capacity and also surpassed Germany who was a wind power leader for a long time. Spain has added around 2.6 GW of solar PV, which is a full half of grid connected installations all around the global and five times increase over Spain’s 2007 additions.

China has doubled its capacity to produce wind energy and now ranked at fourth place all around the world. Another significant and important milestone was that the European Union and the USA added more capacity to produce power from renewable recourses than from conventional energy sources (as gas, oil, coal and nuclear) and it happened for the first time. The industries of Renewable energy boomed mostly during 2008. Global solar PV production was increased by 90% to 6.9 GW in 2008.

Energy Profile Of Pakistan

The energy profile of Pakistan is inadequate and there are always short falls of energy (electricity) especially during summer. Pakistan needs around 14,000 to 15,000 MW electricity everyday to meet all residential and industrial demands. But Pakistan can produce around 11,500 MW, so it means there is around 3000 MW to 4000 MW short fall. This shortfall was experienced extensively and on its peak this year and affecting industry, commerce and daily life. During this year the shortfall for electricity in rural areas was around 12 to 16 hours and in urban areas it was about 8 to 12 hours. The reasons for this deficiency are limited fossil fuel resources, weak economy and mismanagement of the available energy sources. There are some commercial sources of energy available in Pakistan, they are:

  • Hydro energy;
  • Nuclear energy;
  • Oil and gas;
  • Conventional fuels like agricultural wastes, animal dung and wood fuel.

Here, it is an overview of primary energy supplies in Pakistan in MTOE (TOE: ton of oil equivalent. It is an energy unit which is equal to the energy of burning of 1 ton of crude oil which is about 42 GJ)

From fig 1.3 it is clear that energy supply of Pakistan is highly dependent on Oil and Gas. Both Oil and Gas contribute more than 79% of total primary energy supplied. The other sources of energy like hydro- electricity, coal, nuclear electricity and imported electricity contribute about 21% of the total share. As energy is essential for all types of production processes. Pakistan has been growing in agricultural and industrial sector during last decade and that’s why energy demand is being increased. As population and industry is growing, the daily demand will increase up to 20,000 MW in 2010.

Pakistan meets around 75% of its energy needs by oil, gas and hydro electricity production. Natural gas has played an important role to meet the energy needs in recent years. But Pakistan needs to expand its energy resource on permanent bases. In order to overcome this energy shortage, Pakistan needs to expand and develop its indigenous energy resources such as hydropower, wind and solar energy. Pakistan is one of the highest solar insulation areas of the world.

Now we will briefly discuss the main energy sources in Pakistan.

Natural Gas

After the independence of Pakistan in 1952 Sui natural gas field resources in Baluchistan were discovered first time. The production at Sui started in 1955 and was on its peak in 1985. It was the most productive gas field of Pakistan in early 1990s. In FY 1993 it was accounting 46% of production. After that the second largest gas field was discovered which is also located in Baluchistan at Mari, which was contributing 20% of all production. Total 25 gas fields were fully operational in FY 1993. The estimation of recoverable natural gas reserves were estimated around 662.0 billion cubic meters, with an extraction rate around 14.0 billion cubic meters.

In order to meet the increasing demand of energy and for future planning, efforts from government are being made to increase the production of gas in the country. To do this exploration activities are the first step. The estimation of recoverable reserves of natural gas was 29.671 trillion cubic feet in January 2009. During July-March 2008-2009 the average production of natural gas was 3986.5 mmcfd (million cubic feet per day) but during the corresponding period of last year it was around 3965.9 mmcfd which shows an increase of around 0.52%. At the moment 26 public and private sector companies are engaged in exploration and production activities of oil and gas in Pakistan.

LPG

The contribution of LPG (Liquefied Petroleum Gas) is about 0.7% to the total energy supply of Pakistan. LPG is being supplied to many remote areas where the supply of natural gas is not technically suitable. To do this government has changed policies for energy supply and management and as a result of this modification the supply of LPG in 2007-2008 was 601,592 Metric Ton and in last few years the annual cumulative growth rate was 18.2%.years. Around 32,621 MT of LPG was imported during July-March, 2009.

CNG

The main reason of encouragement of Compressed Natural Gas (CNG) use is to improve environment and to decrease the dependency on other fuels. The price difference between petrol and CNG is about 60.0 percent, that’s why vehicles are being converted to CNG day by day and around 2.0 Million vehicles are using CNG. The numbers of CNG stations are also increasing day by day and there are around 2,700 established CNG stations in Pakistan which covers an investment of Rs.70 billion. At present Pakistan is the largest CNG user country.

Oil

The estimation of recoverable reserves of crude oil in total in Pakistan were around 313 million barrels in January 2009. The average production of crude oil during July-March 2008-09 was 66532 barrels per day. The average production of crude oil during last year was 70166 barrels per day which shows a negative growth of 5.2 percent.

The average production of oil in Pakistan remained 67,438 BOPD in 2006-2007. Oil and gas development company and limited (OGDCL) was the biggest oil producing company in Pakistan with a production of around 13.261 million barrels which contribute around 54% of the total oil production per year of Pakistan with an average rate of 36,332 BOPD. After that British Petroleum (BP) is the second largest oil producing company with total contribution of 16% of total oil production in Pakistan. BP produces around 4.025 million barrels averagely with 11,029 BOPD. Pakistan oil fields limited (POL) produced around 3.231 million barrels. There are other small oil production companies as well in Pakistan.

Coal

The total estimation of coal recourses of Pakistan is more than 185 billion tones. Thar coalfield (Sindh province) is the biggest coal source which worth more than 175 billion tones. Pakistan’s coal is generally ranked from lignite to sub bituminous. The production of coal was decreased in during July-March 2008-09 by 28.8%. About 60.4% of the total coal production is being consumed by the brick kilns industry. Cement industry is also using a large fraction of coal which is around 37.4% and almost all cement industry is being switched on coal from furnace oil. As energy demand is increasing day by day and government is reshaping the energy policies. Due to high prices of imported energy government of Pakistan has decided to increase the share of coal from 05 to 19% in the overall energy mix up to 2030. In view of expected shortfall of energy resources and electricity during the next 10 years the maximum utilization of coal would be needed for power generation and gasification. According to government energy security plan, a target has been set which is to generate about 20,000 MW power from coal by 2030 and 50% by 2050.

Nuclear Energy:

Pakistan is the 7th nuclear power of the world. In 2009, the nuclear power plants contribute up to 2.4% share to the total electricity production in Pakistan. Pakistan has two working nuclear reactors which produce about 425 MW power for the generation of electricity. The third nuclear reactor will be operational in spring of 2010. In Pakistan nuclear power contributes very small to the electricity production. The total generating capacity is around 20 GWe while in 2006; 98 billion kWh gross was generated. First nuclear power reactor was started in 1971 in KANUPP near Karachi and it has small capacity of 125 MWe and it is pressurized heavy water reactor (PHWR). The second unit was started in May 2000 and is known as Chashma-1 in Punjab. It has capacity of 325 MWe. It is pressurized water reactor (PWR) and was supplied by China’s CNNC under safeguards. It is also known as CHASNUPP-1. In December 2005 construction of its twin Chashma-2 was started. It is reported that it cost PKR 51.46 billion (US$ 860 million, $350 million were financed by China).

But these sources are not sufficient to overcome this energy crises and Pakistan needs to develop renewable energy sources.

Renewable Energy Sources In Pakistan

Pakistan is situated in such a special geographic location that it is blessed with abundant and inexhaustible Renewable Energy (RE) resources. These resources can play an effective and considerable role for the contribution towards energy security of Pakistan. When we look into current world energy scenario in general and energy scenario of Pakistan in particular, the development and adoption of RE technologies makes better sense. Government policies and objectives to develop RE technology are also matching with this sense so that the share of RE in overall energy mix should be at least 5% by the year 2030.

Wind potential: 0. 346 Million MW

Solar potential: 2.9 Million MW

Mini & Small Hydel: 2,000 MW [9]

There is a significant potential of wind energy in Pakistan especially in the coastal belt of Baluchistan and Sindh, and also in the desert areas of Punjab and Sindh. However this renewable energy source has not been utilized. AEDB collected the wind data of all Pakistan from Pakistan Metrological Department and was analyzed. On the basis of this collected data and analysis, it was stated that the coastal belt of Pakistan has a God gifted 60 km wide (Gharo-Keti Bandar) and 180 km long (up to Hyderabad) wind corridor. This wind corridor has the potential to generate 50,000 MW of electricity. AEDB has done other different surveys in Gharo and Jhimpir regions and some coastal area of Baluchistan. After these surveys it is concluded that in the south region most of the remote villages can be easily electrified through micro wind turbines. Furthermore it is estimated that in Baluchistan Sindh and Northern areas more than 5000 villages can be electrified through wind energy.

Sincere efforts and aggressive lobbying has been done by AEDB with national and international investors to invest and to make them realize the tremendous potentials of RE. AEBD is in negotiations with international companies to set up their business in Pakistan. However large wind mills have not been installed yet but 30 wind mills for water pumping have been installed on experimental basis in different parts of Baluchistan and Sindh. In southern coastal areas of Pakistan remote villages are currently electrified with energy and so far more than 17 villages have been electrified using micro wind turbines.

Around 95% of total electricity generation is from hydropower in Pakistan. But during summer in hottest and driest months of the year it becomes less productive and cannot meet the energy demands. Also, around 70% of the population lives in 50,000 villages. Many of these villages are very far from the main transmission lines and also it is not economically viable to connect these small villages to the main grid due to their small population. On the other hand solar energy has excellent and significant potential. Pakistan is one of those countries which receive solar radiations at high level throughout the year. Every day it receives an average of about 19 MJ/m2 of solar energy. Studies have been already done and solar systems have been developed and tested.

There is a list of different projects which are completed by Pakistan council of Renewable energy technology.

Potential Of PV In Pakistan

The location of Pakistan is very ideal to take advantage of solar energy as a source of energy because Pakistan is in the Sun Belt region. Solar energy is available abundantly and widely distributed all around the country. Following figure shows solar insolation map for Pakistan. The map shows around 200-250 W/m2 per day. The Baluchistan province is very rich in solar energy. It receives around 19-20 MJ/m2 per day averagely which is equal to 1.93-2.03 MWh/ m2 per day with annual 8-8.5 mean annual sunshine hours. These conditions are ideal for PV and solar energy applications.

Solar energy is very good option for off-grid villages. There are around 75,000 off-grid villages which contains 4 million homes and every home accommodates around 4-5 people. These off-grid villages are situated in the Baluchistan and Frontier Province. AEDB has set a target to electrify a thousand villages via solar technology by the year 2010. In this respect the first contract has been given to the Sehgal electronics group (Pakistan). Each home which is electrified with PV will have around 400 W power supply and lead acid batteries for overnight storage. There are also other plans to have local production using PV modules with and estimation of this production is around 3MW/year.

Possible Routes For Solar PV In Pakistan

The global demand of PV equipment is increasing day by day and due to this fact the prices for PV systems, equipment and electricity has gone down remarkably. PV could be exploited in Pakistan through following two routes.

Off-grid Or Stand-Alone Sector

Stand-alone systems generate electricity independently of the utility grid. Stand alone systems can be a very good option for the remote areas and very deep located villages, where the extension of power transmission lines would be more costly. Also it could be implemented in environmentally sensitive areas as parks, remote homes and cabins. In rural areas, it could be used for solar water pumps and farm lighting. [12]

Grid-Connected Sector

Grid-connected PV systems supply extra power when the home system’s power supply is not sufficient to fulfill the load. These systems remove the need of battery bank. In some situation, utilities allow net metering, by which the owner can sell extra power back to the utility.

Current Solar Energy Applications In Pakistan

Both PV and solar thermal have a wide range of applications in Pakistan. Although the scale of utilization and adoption has been very small but it has been utilized for last 25 years in Pakistan. Different applications mainly PV and solar thermal applications are summarized as.

Photovoltaics

Eighteen PV stations were built by the government in the early 1980s to electrify different villages the country. The installed capacity was nearly 440 kW but due to the lack of technical knowledge and follow up, these systems could not perform as required. Currently in Pakistan solar energy is being used for telephone exchanges stand alone rural electrification, cathodic protection, highway emergency telephones and vaccine refrigeration in hospitals. In different parts of Baluchistan, about 20 solar water pumps have been installed for drinking purposes by The Public Health Department. The northern and western area of Pakistan are mostly hilly and mountain areas (Hindu Kush-Himalayas, HKH region), which are blessed with a lot of sunshine with 4-6 kWh/m2 daily average solar radiation. Seven solar stations were installed in this region in the late 1980s for lighting by different companies. The total capacity of these systems was 234 kW. They are not in operation now due maintenance problems.

SIEMENS Pakistan has installed many stand alone solar systems in Pakistan. On the Lahore-Islamabad Motorway, it has installed power supply systems for many microwave-link repeater stations and more than 350 emergency call boxes.

Solar Thermal Applications

There are many applications which utilize solar energy directly by utilizing its heat characteristics. Such applications are much simple, low cost and easy to adopt. The applications include heating and cooling of homes and buildings, cooking, water heating for domestic and industrial use and drying agricultural products. A brief description of such applications in Pakistan is given here.

Solar Water Heaters

This technology is quite mature in Pakistan but very limited because of its higher capital cost as compared to conventional water heaters which operate on natural gas. But in last couple of years it has started to gain popularity because a number of public sector organizations are working to develop low cost solar water heaters. The prices of natural gas and electricity are increasing day by day, so people are adopting solar water heaters and also private sector has already started the production of such heaters.

Solar Cooker

Different public sector organizations have been working to develop low cost and efficient design solar cookers. In HKH region of Pakistan, more than 2000 solar cookers are in use. This number is very small. It needs to be more popularized. Pakistan needs to reduce the use of precious forest resources as fuel wood and to replace it with solar cookers.

Solar Dryers

Solar energy can be very good option for drying agriculture products. By this, we can get very good quality products at much less cost. Northern mountainous areas like Gilgit and Sakardu are very rich in fruit production like apricots which used to be wasted by tons every year. But now solar dryers are being used to dry large quantities of fruit, which is leaving a positive effect on the economy of this area. Different NGOs are working for the popularizing and the use of such dryers.

Solar Desalination

Drinkable water is unavailable in many parts of Sindh, Baluchistan and southern Punjab and it is very critical issue. Underground water is available but it is highly saline. This saline water is not fit for drinking at all and causes many dangerous diseases such as hypertension. Solar energy can be utilized to convert this available saline water into drinkable water. Solar desalination is very simple, low cost and easy to use. Also it is very easy to adopt. A successful solar desalination project is in operation and it is working very fine and helping to change the life style of the population of Gawader in the Baluchistan province. It consists of 240 stills and each can clean 6000 gallons of seawater per day.

2. Basics And Components Of A PV System

Basics Of A PV System

Photovoltaic is the technology which converts solar energy directly into electricity and this process is carried out though solar cells. Solar cell is a device which converts sun energy into electricity. We can say solar cell as photovoltaic cell as well but solar cell term will be used when the source of light is defined as “sun” but if it is not defined than we can say it as photovoltaic cell.

Now days when entire world is looking for a neat and clean environment and want to meet huge energy requirements without disturbing and populating the environment, sustainable energy sources seems to play their important role. Researchers and scientists from all around the world are looking for these types of renewable sources. They are trying to get the energy needs from these renewable energy sources. The main advantages of using renewable energy sources are

1. Neat and clean environment

2. Yield of energy is higher

3. Safer for electricity production as compared to convention methods (low voltage)

4. Long life times

5. Low maintenance cost

6. Use of natural sources which are being wasted with time.

These are the reason, why people prefer renewable energy sources. There are different types of renewable energy sources as

1. Solar energy

2. Wind energy

3. Tidal energy

4. Geothermal energy

5. Wave power

6. Hydropower

7. Bio energy

We will discuss solar energy in detail and its related topics in this report. There are different units in a PV system and all these units combine to make a full working PV system. These are

PV System Components

1. PV Panels

2. Trackers and tracking system

3. Array DC Disconnect

4. Blocking diodes

5. Charge Controller

6. Battery Bank

7. System Meter

8. Main DC Disconnect

9. Inverter

10. Kilowatt-Hour Meter

11. Backup Generator

PV Panels

PV panels are the defining components of a PV system, which uses sunlight to make direct current (DC) electricity. Wafers of semiconductor material are used for this purpose. They use light (photons) to produce electricity (photovoltaic effect). When the electricity is generated than it powers our electric loads such as lights, computers, and refrigerators. PV panels differ from each other on the basis of power rating in watts which is based on their maximum power generation capacity.

Solar cell is the fundamental and basic building block in a PV system which acts as power conversion unit of this system. There are different types of solar cells now days available having different power about 1 or 2 watts. Usually solar cells are made of single crystal silicon and they are limited to about 25% efficiency. The reason is that they are most sensitive to IRL (infrared light), and the radiations in this region of electromagnetic spectrum are relatively low in energy.

Another type of solar cells is Polycrystalline solar cells. They are made by a special casting process. In this process molten silicon is being poured into a mould, allowed to cool down and then it is sliced into wafers. By this process we can make relatively cheaper cells as compared to single crystal cells, but their efficiency is less than 20%. The reason is that there is internal resistance on the boundaries of silicon crystals which affects the efficiency.

The third type of solar cells is amorphous cells and they are made by a special process in which silicon is deposited onto a glass substrate from a reactive gas such as silane (SiH4). These types of solar cells are used in solar powered watches and calculators, but now day’s bigger modules are also manufactured. They are also rather cheap and their efficiency is only up to 10%. The reason is, since amorphous silicon cell has no crystal structure and there are much internal energy losses.

Solar cells are not just restricted to semiconductor materials; solar cells are available now days which convert sun light into electricity by organic molecules. Their efficiency is up to 10%. Apart from various types of silicon, other materials can also be used to make solar cells like cadmium telluride and gallium arsenide. There are different types of cell packing’s. The most common are “raw cells,” and they are often with cover sheet. Now we have discussed solar cells. These solar are combined together to make a module to get boosted power for practical purposes. Than these modules are combined together to make a panel, these panels are joined together to form a big array.

Trackers And Tracking System

Solar tracker is a device on which solar panels are fitted and the motion of the sun is tracked through this device. It ensures that the maximum amount of sunlight will strike to the panel throughout the whole day. Actually it is a mounting rack which follows the sun constantly. By using trackers, we can utilize maximum sunlight and thus can produce more electricity. In the morning time, it is low on eastern horizon while at the sunset it is low at western horizon. But at noon the position of sun is very high in the sky. This motion is due to the rotation of earth. Trackers keep PV modules perpendicular to incoming sun radiations and maximize the energy production. The increment in the energy production using trackers depends on the site and the type of tracker. Usually energy production increases 25 to 40% annually, which is shown in more detail in the following figure.

To get maximum efficiency tracker must be placed in a suitable location. A good tracker site is that on which sun can be seen very early in the morning time and receive sunlight until sunset. There should be no solar obstructions like trees and buildings on the site or near the site in order to work perfectly. Before considering the tracker into system design, an evaluation of the site is done using Solar Pathfinder. Trackers are usually mounted on ground and use a heavy steel pole which is sunk into a concrete foundation. There are some systems where the trackers are mounted on the roofs, but it can create structural problems. There are two basic types of trackers.

1. Electrically operated

2. Thermally operated

Thermally Operated Trackers

These trackers are based on mass transfer from one side to the other side of the tracker to track the sun. This transfer of mass causes the tracker to turn from east to west by following the sun. Actually two tubes filled with Freon (which vaporizes and become gas) are mounted on east and west sides of the tracker. With the sunlight, the temperature of Freon becomes higher on one side of tracker, it starts to become vapors. These vapors take more space than as compared to the liquid Freon, which pushes Freon (liquid) to the other side. This transfer of mass from the one side to the other side of the tracker causes the change in the balance of tracker which eventually rotates it to the west. Usually they are slow


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