Renewable energy sources such as wind, biomass, solar, geothermal, hydro, ocean are considered to be the most viable and environment-friendly option for generating clean and pollution free energy. Among several resources available solar and wind energy have great capability to meet the growing power demand but due to unpredictable and intermittent energy availability from single source there arises a need for innovative hybrid renewable energy system which involves wind and solar energy. This paper concentrated on the solar-wind hybrid power system that harnesses solar and wind energy to generate electricity. Performance of 275 kW solar-wind power plant at Wind Turbine Test/Research Station, Kayathar, Thoothukudi Distt. (T.N.) was studied. Several parameters used for analysis were wind capacity utilization factor, solar capacity utilization factor, performance ratio and overall hybrid power. Eight months data recorded of 2017 were used in calculations. The results of this study suggests that on integrating the existing wind turbine generator with solar photovoltaic plant the overall capacity utilisation factor increases thereby improving the performance of the plant.
Keywords: PV system, Wind system, Hybrid capacity utilization factor, Performance ratio
Our planet is under a serious threat of depleting fossil fuel reserves. Most of our energy consumption is from fossil and nuclear power plants and very few parts are met by renewable energy resources such as wind, solar, biomass, ocean and geothermal as we are still in transition phase of adopting to these new technologies. There will be time in near future when there will be severe fuel shortage. As per the law of conservation we can neither create energy nor be destroyed but it can only be converted from one form to another. Most of our research is focused on developing consistent and robust technology to tap renewable energy sources potential and how to conserve and utilize effectively. Among them wind and solar had a strikingly increase in the past ten years as both are pollution free resources and abundant in nature.
With rapidly growing economic rate and contributing to over 17percent of worlds population, India is indeed a remarkable consumer of energy sources 1 India consumes its maximum energy in residential, industrial and agriculture purposes in comparison to China, Japan and Russia. Solar energy is basically energy generated from sun which is non- conventional and inexhaustible.by adopting proper technology according to geographic location, we can extract maximum energy from sun and battery stored energy can be utilized for 24hrs during night time and irrespective of bad weather conditions. Moreover, solar energy is demonstrated as the new era of energy generation. Further, with surge in prices of fossil fuels it became almost impossible to meet energy demand-supply ratio especially in far-flung and rural areas. Alternative source of conventional energy that is generators is a good option but its cost of refueling is high if it is to be used for commercial purposes.
Wind energy is the Kinetic energy of moving air and wind power system is the one which converts kinetic energy of wind into electrical energy. Wind energy systems for irrigation have been in use since ancient history but its conversion to power started in late 20th century. 2Wind turbines convert the kinetic energy present in the wind into mechanical power which can be used for milling and grinding purposes and for further conversion to electric power. Array of wind turbines is known as “wind farm”.
The major drawback of renewable energy systems is their unpredictable nature which poses a great challenge before researchers so there’s being increasing focus on hybrid renewable energy systems by utilizing different sources like wind and solar, solar biomass in order to save the situation. With the above goal in mind a solar –wind hybrid power plant with installed capacity of 275kw was identified and studied as a model for performance analysis.
Fig.1. Schematic arrangement of Solar-Wind Hybrid Power system
2. Proposed Hybrid System Configuration
The hybrid power plant selected for study has been installed in 2016 at Kayathar WTTRS, Tamil Nadu, India. Since the 200KW (Micon) wind turbine generator was underperforming, a 75KW solar system was integrated thus increasing its capacity to 275KW for the maximum utilization and improving its overall cuf with existing infrastructure facilities. This plant is designed to produce 200kwh/day thus the annual energy generation should be up to 1752000KWh.The implemented hybrid power generation system makes use of solar PV and wind turbine to produce electricity and supply the Grid through 200KVA Transformer.
2.1. Wind Power Plant Details
Wind turbine uses AC-DC-AC type converter and a wound rotor induction generator. This rotor is fed at variable frequency through this converter while its stator winding is connected directly to the 50 Hz grid. The wind turbine output power which is AC is again converted into DC power using the 3- phase bridge rectifier. The bridge rectifier output and solar output is combined and given to the inverter that will produce 3-phase AC power which is connected to the grid. The wind turbine captures kinetic energy from wind and converts it into mechanical energy. The power output from the wind turbine is calculated as
Po = (1 )/2 p AV^3Cp
where, Po = Power output
? = Air density (Kg/m3),
A = Area swept by the rotor blades (m2)
V = Velocity of the air (m/s),
Cp = Power Coefficient.
Table 1. Wind turbine specifications
S.no Parameter Values
1 Power output 200KW
2 Manufacturer MICON
3 Air density 1.225kg/m3
4 Rated wind speed 15m/s
5 No of blades 3
6 Output voltage 400 V
2.2 Solar Power Plant Details
The solar power plant is installed at the Kayathar, WTTRS, TamilNadu, The grid connected plant consists of 100 polycrystalline silicon solar modules 250 Wp each one and comprised 60 solar cells with an overall installed capacity of 75 kWp spanning a total surface area of 450 m2 and inclined at 32° toward the north . The PV modules are arranged in 3 parallel arrays, with 25 modules in each array having rated voltage of 30.2V.
Table 2. PV module specifications
S.no Parameter Values
1 No of Cells in a Module 60(10*6)
2 Maximum Power (Pmax) 250Wp
3 Rated Voltage (Vrated) 30.2 V
4 Rated Current (I rated) 8.42A
5 Open Circuit Voltage (Voc) 37.4 V
6 Short Circuit Current (Isc) 8.86 A
7 No of Modules/Array 100(25*4)
8 No of Arrays 3
9 Voltage of Solar Array 750 V
10 Current from Solar Array 33A
11 Current from Solar Panel 100A
3. Inverter details
The PV modules are arranged in 4 parallel arrays, with 25 modules in each array connected to a 25550 W (LCA SB5000TL) inverter feeding direct supply into the grid and then futhur to the transmission lines. Its full load efficiency is between 94-98.5%as rated. On the output side of the inverter there is a single phase alternating voltage of 230 V, 50 Hz and on the front side there is a display to read out the voltage and DC current values, output power, daily and total amount of electrical energy generated by the solar PV modules.
Table 3. Technical specifications for inverter
Power 25550W Prated 25KW
Vmax 1000V AC Voltage 230V
Vrated 392 to 800V/ 600V Frequency 50Hz
Imax 33A Imax 36.2A
It starts with the filtering of all the faulty logs in the SCADA system where the record was missing or not available for that date, time or month and was replaced with ‘NAN’ as these events can’t contribute to the evaluation and hence were removed. After that, events which were recorded in seconds interval were divided into fifteen minutes time interval in order to calculate the plant performance parameters, like Hybrid power generation, standalone power generation shared by the wind and solar power generation units, capacity utilization factor (CUF) of both wind and solar and the overall increase in capacity utilization factor from the recorded performance data for the hybrid model. The obtained results were analysed and compared with the corresponding plant design parameters using both tabular as well as graphical representation, so as to check for their conformity. The power generation and performance data of this power plant was recorded over the period of 240 days i.e. from February to December 2017 via automatic data logger. Additional readings were also recorded, as and when required, for the analysis purpose.
4. Parameters for Performance Evaluation
The various desired performance parameters were calculated and tabulated. The sample calculations for the various parameters are given below:
Solar Energy Generation (kWh) = Energy generated from solar power plant can be calculated by multiplying power produced by solar with time for the given year and is calculated using
SEG = (Solar power output (kW) × (Time)
Wind Energy Generation (kWh) = Annual energy generated from wind power plant can be calculated by multiplying power produced by wind with time for the given year and is calculated using-
WEG = (Wind Power output (kW) × Time)
Hybrid Energy Generation(kWh) – Annual energy generated from hybrid (wind and solar) power plant can be calculated by multiplying submission of power produced by both wind and solar with time for the given year and is calculated using-
AHEG = (Hybrid power output (kW) × Time
Capacity Utilisation Factor (C.U.F) = The performance of any renewable energy power plant is often denominated by a metric called the capacity utilisation factor. It is the ratio of actual output over a period of time to the rated plant capacity and can be calculated using-
CUF = (Actual energy generated from the plant (kWh))/(Plant capacity (kwp×Time) )
3Global Tilted Irradiance (GTI)–The total amount of direct and diffuse radiation received from above by a tilted surface.
Global Horizontal Irradiance (GHI) – The total amount of radiation received from above by the horizontal surface.
Performance ratio solar (%) – Performance ratio is a measure for the performance of a PV system considering environmental factors like temperature, irradiation climate changes etc. The performance ratio (PR) is stated as percent and describes the relationship between the actual and theoretical energy outputs of the PV plant and can be calculated by using-
PR = (Energy generated(kwh)× PV reference irradiance(W/m2) )/((Installed capacity(kw)×Total plane irradiance(kWh/m2) )×100
4Reference yield- The reference yield (YR)can be calculated by dividing the total daily in-plane irradiation(KWh/m^2) by the module’s in-plane reference irradiance (KW/m^2).
YR = (Total daily in-plane irradiation)/(Module in-plane reference irradiance)
4. Results and discussions