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Study of a Standalone Wind and Solar PV Power
Systems
Shafiqur Rehman
Center of Engineering Research, Research Institute King Fahd University of Petroleum and Minerals (KFUPM) Dhahran-31261, Saudi Arabia srehman@kfupm.edu.sa
Ibrahim M. El-Amin
Electrical Engineering Department King Fahd University of Petroleum and Minerals (KFUPM) Dhahran-31261, Saudi Arabia imelamin@kfupm.edu.sa
Abstract —This study utilizes hourly average wind speed and hourly total global solar radiation data for the years 2007- to study the energy yield from (i) a standalone wind power system of 6kW rated capacity and (ii) a standalone 6kW photovoltaic (PV) power system. These wind and PV power systems are installed in the campus of King Fahd University of Petroleum and Minerals at Dhahran, Saudi Arabia. The annual energy yields from standalone wind and solar PV power plants each of 6kW installed capacity were found to be 8,000 kWh and 10,364 kWh with respective capacity factors of 14.3% and 19.7%. The propose wind turbine could displace 2 tons of green house gases annually from entering in to the local atmosphere and the solar PV power plant could be able to reduce around 3 tons of these gases annually.
I. INTRODUCTION
The materialistic life styles and exponentially increasing population trends have become the modern threats to the societies in almost all regions of the world. These increasing trends putting hypertensive pressures on energy producers to increase generating capacities which is both cost, labor and time intensive process. The every increasing gaps between the energy supplies and demands are giving birth to social evils and at the same time the increasing generating capacities are adding green house gases in to the atmosphere which means polluted air and hence health hazard. To combat all of these problems of social unrest and environmental depletion, new and renewable sources of energy like solar, wind, geothermal, biomass, bio-fuels, tidal, and wave should be studied and implemented wherever possible. The distributive nature of these energy resources is further advantageous to provide electricity to remotely located populations who, in this advanced modern world of today, have not experienced the joy of electrical energy.
Middle East is situated in the western part of Asia and constitutes of countries like Saudi Arabia, Bahrain, Qatar, Oman, Jordan, Kuwait, UAE, Iraq, Iran, Syria, Lebanon, and Yemen. All of this region and countries experience high intensities of solar radiations and longer hours of availability with large number locations with higher annual average wind
speeds. Hence these renewable energy sources (RES) should be utilized to generate electricity for both small and large applications and off-grid and on-grid configurations. These applications may include the grid connected wind and PV power plants; isolated wind and PV power plants; and pv- diesel, wind-diesel, wind-pv-diesel hybrid power plants with and without battery backup.
Wind, sun, and hydro are clean, in-exhaustible and renewable sources of energy and are available free to everyone. Moreover, in one way or the other everyone has access to at least one of these sources of energy round the year. These days, the power of the sun and wind is being utilized to generate energy for small isolated grids and big grid connected power plants. Additionally, hybrid power systems such as wind and diesel, pv and diesel, wind pv and diesel with and without battery storage options are also being used to get reliable and continuous power supply. As per global trend; the utilization of wind and solar sources of energy is on the increase. The cumulative global wind power installed capacity reached 120,791 MW at the end of 2008. With 25,170 MW installed capacity USA lead the way while Germany, Spain, China, India, and Italy followed the trends with 23,903MW, 16,754MW, 12,210MW, 9,645MW and 3,736MW installed capacity as of December 2008 [1]. According to a recent report [2] the cumulative global PV installed capacity stood at 15 GW in 2008 compared to 9 GW in 2007. Spain represented nearly 50% of the new installations in 2008 by adding 2.5 GW new installation capacities. Germany, USA and South Korea followed the trend with 1.5 GW, 342 MW and 274 MW PV additional installed capacities during the year, respectively.
Nandi and Ghosh [3] designed a wind-pv-battery hybrid power system for a village in Bangladesh using measured wind and solar radiation data for the year 2006. The study showed that least cost of energy (COE) was about US$0.363/kWh for the community using 169kWh/day with 61kW peak and having minimum amount of access or unused energy. Dalton, Lockington, and Baldock [4] presented an analysis of the technical and financial viability of grid-only, RES-only and grid/RES hybrid power supply configurations
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for a large-scale grid-connected hotel. The authors used net present cost (NPC), renewable fraction (RF) and payback time as assessment criteria provided in RES software HOMER (National Renewable Energy Laboratory, US).
Saheb-Koussa, Haddadi and Belhamel [5] studied the techno-economical aspects of a photovoltaic/wind/diesel hybrid power system with battery backup option for seven remotely located sites in Algeria. Their results indicated that the hybrid system is the best option for all the sites considered in their study. It provides higher system performance than photovoltaic or wind alone. The cost-effectiveness of the solar PV system and the solar/hydro schemes for rural electrification were evaluated employing the HOMER simulation software, considering sustainability factors such as system efficiency, weather, fuel costs, operating and maintaining costs by Abdullah, Yung, Anyi, Othman, Ab. Hamid, and Tarawe [6]. The study found that hybrid systems can have efficiency range of 15%–75% compared to stand- alone of only 10%, indicating hybrid systems are more reliable and sustainable – in minimizing both energy losses and excess energy. A great deal of research related to performance, optimization, and other related parameters [7–12] has been carried out on hybrid energy systems.
In Saudi Arabia, the per capita energy consumption has reached to 20kWh/day in 2008 compared to 19.4kWh/day in 2007 i.e. a net increase of 3.1% in one year, as shown in Fig. 1, [13]. A maximum of 10% increase in per capita energy was observed in 2004 compared to that in 2003. On an average over 25 years period from 1984 till 2008, 4.1% annual increase in per capita energy per day has been observed [13] which really significant and needs to be addressed immediately. As a result of this per capita increase in energy consumption, the installed capacity has also been increased tremendously, as shown in Fig. 2. Kingdom of Saudi Arabia has vast open land and is the largest producer and supplier of fossil fuels in the world but still encouraging utilization of clean and renewable sources of energy.
Figure 1. Per capita energy consumption in Saudi Arabia [13]
In Saudi Arabia, work on wind speed and solar radiation data analysis and respective energy resource assessment has been reported in the literature as can be seen from [14-20]. Rehman, Halawani and Husain [14] studied the Weibull parameters for ten anemometer locations in Saudi Arabia and found that the wind speed was well represented by Weibull distribution function. Rehman and Halawani [15] presented
the statistical characteristics of wind speed and diurnal variation. The autocorrelation coefficients were found to be matching with the actual diurnal variation of the hourly mean wind speed for most of the locations used in the study. Rehman, Halawani and Mohandes [16], Rehman and AFtab [17] and Rehman, El-Amin, Ahmad, Shaahid, Al-Shehri and Bakhashwain [18] reported wind power assessment for various locations in the Kingdom and suggested potential sites for grid connected wind farms. Rehman [19] and Mohandes, Rehman and Halawani [20] developed empirical models for the prediction of solar radiations in different parts of the Kingdom and also conducted energy assessment using measured solar radiation data.
Figure 2. Cumulative power installed capacity of Saudi Arabia
The present study utilizes measured wind speed and solar radiation data in Dhahran, Saudi Arabia to estimate the energy yields from stand alone 6kW wind and 6kW solar photovoltaic power systems. In fact, the research team is in the process of installing a 5kW wind turbine and a 5kW PV system at the campus of King Fahd University of Petroleum and Minerals (KFUPM) to generate energy and conduct studies related to grid connectivity issues and controls. The study, as next step, will also conduct experiment for wind-pv hybrid power system with and without battery backup system.
II. SITE AND DATA DESCRIPTION The site for the installation of the wind and pv systems has been identified and equipment procurement and the site development work is in progress. This is an open from north, east and south direction and is visible from the university's entrance gate and also from out side the university. The wind mostly blows from north so this will be a good site from wind harnessing point of view. The wind, solar radiation and other meteorological data is being measured and recorded in the university campus jus 300 to 400 meters away from the actual site of development. The meteorological station is installed on top of 6 storied building and is open from all direction and there are no obstacles where as wind speed data concerned.
The seasonal and annual summary of meteorological parameters [Ambient temperature (Temp), Relative humidity (RH), Global solar radiation (GSR), Ambient pressure (Press) and Wind speed (WS)], used for the estimation of energy from wind and solar PV stand alone power systems, is given in Table I. The highest monthly mean WS of 5.5m/s was observed in June while a minimum of 3.8m/s in October with an overall annual mean of 4.5m/s at 10 meters above ground level. The global solar radiation values were found to be
Figure 5. Seasonal variation of global solar radiation on a tilted surface for Dhahran.
The annual energy yield from 6kW solar PV power plant was found to be 10,364kWh with capacity factor of 19.7%. The proposed solar PV power plant will be able to avoid annually 3 tons of GHG equivalents of CO 2 from entering in to local environment and 60 tons during 20 years of plant life.
Figure 6. Seasonal variation of energy yield from 6kW installed capacity solar PV power plant at Dhahran.
IV. CONCLUSIONS AND RECOMMENDATIONS The study basically presented the behavior and availability of wind and solar radiation sources required for energy extraction form respective sources along with other meteorological parameters such as ambient temperature, pressure and relative humidity which play important role both in the production and consumption of energy. Some of the major findings are listed below:
The highest monthly mean WS of 5.5m/s was observed in June while a minimum of 3.8m/s in October with an overall annual mean of 4.5m/s at 10 meters above ground level.
The global solar radiation values were found to be varying between 3.28 and 7.73 kWh/m2/d with annual average of 5.6kWh/m2/d.
The annual wind energy yield delivered to the grid was found to be 8000kWh with capacity factor of 14.3% after taking in to consideration all the losses and adjustments of temperature and pressure coefficients and availability factor.
The specific wind energy yield was found to be 306kWh/m^2.
The proposed 6kW wind turbine could displace approximately 2 tons CO 2 equivalent green house gases from entering in the local atmosphere and about 40 tons during the life time of the turbine.
The annual energy yield from 6kW solar PV power plant was found to be 10,364kWh with capacity factor of 19.7%.
The proposed solar PV power plant will be able to avoid annually 3 tons of GHG equivalents of CO 2 from entering in to local environment and 60 tons during 20 years of plant life.
The study recommends the following:
Both the systems i.e. wind and solar PV should be tested for different load conditions and availability of wind speed and solar radiation intensities.
Effect of the fluctuations of wind and solar radiations and thus the energy produced on grid should be studied in actual prevailing conditions.
Both above mentioned tasks should be conducted/repeated for a wind-pv hybrid power system
ACKNOWLEDGMENT
The authors would like to thank the Center of Research Excellence in Renewable Energy at KFUPM for providing the technical and financial support under the projects grant CoRE- RE-07 in carrying out this study.
REFERENCES
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