Urban Eco-Greenergy TM Hybrid Wind-Solar Photovoltaic Energy System and Its Applications

Transcription

1 INTERNATIONAL JOURNAL OF PRECISION ENGINEERING AND MANUFACTURING Vol. 16, No. 7, pp JUNE 2015 / 1263 DOI: /s ISSN (Print) / ISSN (Online) Urban Eco-Greenergy TM Hybrid Wind-Solar Photovoltaic Energy System and Its Applications Wen Tong Chong 1,#, Wan Khairul Muzammil 1,2, Ahmad Fazlizan 1, Mohamad Reza Hassan 1, Hamid Taheri 1, Mohammed Gwani 1, Hiren Kothari 1, and Sin Chew Poh 1 1 Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur, Malaysia 2 Faculty of Engineering, Universiti Malaysia Sabah, Jln. UMS, Kota Kinabalu, Sabah, Malaysia # Corresponding Author / chong_wentong@um.edu.my, TEL: , FAX: KEYWORDS: Hybrid renewable energy, Omni-direction-guide-vane, Wind energy, Solar energy, Vertical axis wind turbine, On-site power generation This paper introduces the Eco-Greenergy TM hybrid wind-solar photovoltaic energy generation system and its applications. The system is an integration of the novel omni-direction-guide-vane (ODGV) with a vertical axis wind turbine (VAWT). The ODGV is designed to surround the VAWT for wind power augmentation by creating a venturi effect to increase the on-coming wind speed before it interacts with the turbine blades. In wind tunnel tests, the ODGV improves the power output of the VAWT by 3.48 times compared with a bare VAWT at its peak torque. Furthermore, the rotor rotational speed of the wind turbine increased by 182% at 6 m/s of wind speed. A solar PV panel can be mounted on the top surface of the ODGV for solar energy generation. Estimation on wind-solar energy output shows that the system can generate a total of kwh of energy per year. By comparison, the ODGV increases the annual wind energy output by 438%. The green energy generated from the hybrid system can be used to power LED lights or other appliances (e.g., CCTV camera). Manuscript received: August 21, 2014 / Revised: March 18, 2015 / Accepted: April 13, Introduction In the search for cleaner ways of generating energy, numerous efforts have been carried out in the past few decades. Renewable energy researches, particularly wind and solar have been gaining popularity and recognized as potential sources for clean, inexhaustible and free energies. The concept of on-site renewable energy generation is to extract energy from renewable sources close to the populated area where energy is required. In the modern era, on-site energy extraction from renewable energy sources in urban settings is regarded as the next step in the process of reducing dependencies on the usage of conventional power generation using fossil fuels. A hybrid system consisting of wind and solar renewable energy sources is more beneficial than a system that only depends on one source of energy. Also, the power supply from a hybrid system is more stable and reliable. In addition, optimization of hybrid renewable energy system is crucial for researchers to maximize the energy output from the system with the lowest cost and highest reliability. 1,2 There are many discussions on the advantages of using hybrid wind-solar energy generation systems in the literature. 3-5 These advantages, however, depend on the climatic pattern and distribution of wind and solar energy resources. The benefits include: Supplying load demand under varying weather conditions. Overall costs for self-powered systems may be reduced drastically. High reliability without backup power sources. Traditional methods of extracting power from the wind in urban areas using wind turbine alone is not efficient due to the uncertainty of wind speed and the turbulence generated from the surrounding buildings. Therefore, requiring methods such as increasing the oncoming wind speed before it interacts with the turbine blades. 6-9 Moreover, for a wind turbine to be used in an urban area, issues such as the structural strength of the wind turbines, failures of blades, acoustic pollution (due to large wind turbine blades) and electromagnetic interference should be addressed. 10,11 Due to the advantages of a hybrid system and to further improve the performance of small wind turbines, this paper presents the urban Eco- Greenergy TM hybrid wind-solar energy generation system. The design of the system is adopted from the larger building integrated omni- KSPE and Springer 2015

2 1264 / JUNE 2015 INTERNATIONAL JOURNAL OF PRECISION ENGINEERING AND MANUFACTURING Vol. 16, No. 7 Fig. 2 Eco-Greenergy TM hybrid wind-solar photovoltaic energy system Fig. 1 Eco-Greenergy TM hybrid wind-solar energy generation system design and general arrangement (Patent no: PI ) direction-guide-vane (ODGV) The ODGV was originally designed to be installed on top of a high-rise building, shrouding a vertical axis wind turbine (VAWT) that covers much of the roof area of the building. However, the large size of the system drew concerns on the structural, safety and vibration issues that would affect the building and its occupants. Furthermore, installing the system with this scale requires high capital and maintenance costs. Hence, this paper introduces a small scale Eco-Greenergy TM hybrid wind-solar system that employs the ODGV integrated with a VAWT and solar photovoltaic (PV) panel for on-site standalone energy generation. This minimizes the risks posed by the large scale system, and with reduced costs. 2. Working Principles and General Arrangement of Eco- Greenergy TM System The Eco-Greenergy TM system combines the hybrid wind-solar energy generation and energy-saving lighting feature into one compact design. The philosophy of the system is to increase the on-coming wind speed before it interacts with the wind turbine blades. Using the principle of the venturi effect, a shroud-augmentation device called the omni-direction-guide-vane (ODGV) is used to harvest more energy from the wind by increasing the natural wind-stream speed before the wind interacts with the turbine. Fig. 1 shows the overall design of the system. Under the ODGV, multiple lamps can be adapted and arranged for optimum illumination. The height of the pole can be designed between 2 to 30 meters above ground level. The height and size of the system depend on the location s weather pattern and distribution of wind and solar energy resources. The system can be deployed to illuminate parks, lawns, streets or sky-gardens. In remote areas, the system can be adapted to power weather data collectors, flood monitoring systems or as emergency beacons for hikers and travelers. To harvest wind energy from all directions, the ODGV has several guide vanes that surrounds the VAWT. The VAWT sits in the middle of the ODGV, where its driveshaft is directly connected to a generator. On top of the upper wall duct, a solar panel is strategically placed for optimum solar energy generation. The combined green energy generated from the wind and solar sources is used to power the light source. In order to minimize power consumption, the LED lamp is adapted as the light source due to its durability. A battery can be used to store energy generated from the wind turbine and solar panel. Excess energy generated from the system can be used to power other electrical appliances or fed into the grid. The compartment housing is designed to place the hybrid controller and battery. A prototype of the system installed in University of Malaya, Malaysia is shown in Fig Omni-direction-guide-vane The ODGV can be fitted with any form of existing or new VAWT (S-rotor, H-rotor or Darrieus or a hybrid of Darrieus and S-rotor). As shown in Fig. 3, the guide vanes are used to guide the on-coming wind stream to the optimum angle of attack of the VAWT blades. The design of the guide vanes can be adapted into various forms, i.e. curve plates or straight plates with constant or varied thicknesses. The guide vanes, together with the upper and lower wall ducts form the channels through which the wind stream passes through before the wind interacts with the turbine blades. The cross-sectional area at the intake of the channel is preferably two times or more than the cross-sectional area at the exit. Furthermore, the upper and lower wall ducts surfaces are inclined at a fixed angle from the horizontal plane. The venturi effect created by the channels can induce a higher wind speed into the VAWT, which allows for smaller and lighter rotating wind turbine parts to be used to produce similar power output. Moreover, this eliminates or further minimizes the electromagnetic interference issue and noise level caused by the long blades of large wind turbines. The small blades of the VAWT used in the system exert less pull compared to the blades of a HAWT. Hence,

3 INTERNATIONAL JOURNAL OF PRECISION ENGINEERING AND MANUFACTURING Vol. 16, No. 7 JUNE 2015 / 1265 Fig. 4 Omni-Direction-Guide-Vane 13 Fig. 3 Design of the omni-direction-guide-vane (ODGV) and variations of the guide vanes the VAWT produces much lower levels of noise and vibration. 10 Besides, as the VAWT is surrounded by guide vanes, the noise level of an ODGV integrated VAWT is lower than a bare VAWT. 3. Methodology To assess the energy output of the hybrid system, the performance of the ODGV was evaluated in a wind tunnel testing. The estimation of energy output from the hybrid wind-solar system was calculated from the acquired meteorological data from Sepang, Malaysia. As a case study, the Eco-Greenergy TM hybrid wind-solar photovoltaic energy system is assumed to be installed on the top of a 150 m building in an urban area. The system has two 15 W LED lights to illuminate its surroundings. The following sub-sections describe the methodology of the wind tunnel testing, as well as the calculation of the energy output of the hybrid wind-solar system. 3.1 Experimental study of the omni-direction-guide-vane The experiment was conducted to show that the ODGV fitted on the hybrid wind-solar energy generation system can improve the performance of the wind turbine. In the following sub-sections, the ODGV design to be used in the experiment is presented and the methodology carried out in the wind tunnel testing is described Design of the ODGV The ODGV outer diameter was 1000 mm, the inner diameter was 540 mm and the height was 450 mm. The ODGV shown in Fig. 4 has four pairs of guide vanes to form channels which will guide the wind stream towards the wind turbine. The guide vanes for each pair are tilted at angles of 55 and 20, as shown in Fig. 5. At equal spacing, each of the guide vane pairs are positioned around the tapered central cylinder. The four channels are designed to guide the oncoming wind stream towards the wind turbine at 0, 90, 180 and 270 positions. The placement of guide vanes at the outer radial band of the tapered cylinder permits the wind turbine to capture wind energy from every direction. Thus, yaw mechanism can be omitted. Fig. 5 Guide vanes angles Initial test A preliminary test was carried out to simulate swirling and turbulent airflow similar to the real world environment. Three industrial fans were placed to simulate wind flow from three different directions, i.e. 0, 30 and 60. The fans were arranged in parallel. A Wortmann FX bladed VAWT was enclosed by an ODGV model with dimensions shown in Fig. 4. The results from the preliminary test showed that the wind turbine rotor rotational speed was increased by about two times more when the ODGV was in place. This proves that the ODGV has positive effects on the wind turbine performance. Thus, further tests in a wind tunnel were carried out to thoroughly examine the ODGV Wind tunnel testing The wind tunnel test was conducted at the Aeronautics Laboratory of University Teknologi Malaysia. Similarly, the ODGV integrated VAWT from the preliminary test were used in the wind tunnel test. The wind tunnel experimental set-up is shown in Fig. 6. Two types of configurations were tested, i) a bare vertical axis wind turbine without ODGV, and ii) an ODGV integrated vertical axis wind turbine. To assess the self-starting behavior of the wind turbine for both of the configurations, the wind speed in the wind tunnel was increased gradually until the rotor started to rotate. The wind turbine was in freerunning condition where the rotor was only subjected to inertia and bearing friction. No external loads were applied during the self-start assessment. Consequently, evaluations on the power generated and the rotational speed of the wind turbine for both configurations were carried out. In order to conduct the test, the wind speed was fixed at 6 m/s. An

4 1266 / JUNE 2015 INTERNATIONAL JOURNAL OF PRECISION ENGINEERING AND MANUFACTURING Vol. 16, No. 7 Fig. 7 Calculated mean monthly wind speed after passing through the ODGV at the height of 150 m from 2007 to 2009 Fig. 6 ODGV integrated wind turbine test rig 13 external load was applied through the use of hysteresis brake on the shaft rotor. The brake is adjusted to increase the load exerted on the shaft. When the rotational speed of the rotor was stabilized, the maximum torque and power generated calculated from the hysteresis load was recorded. 3.2 Wind energy system The acquired wind speed data from the meteorological station in Sepang, Malaysia is used to estimate the wind energy output generated from the system. The height of the sensor above the ground level is 10 m. To calculate the wind speed at a height of 150 m above the ground level (the Eco-Greenergy TM hybrid wind-solar PV energy system is assumed to be installed on the top of a 150 m building), the following wind shear equation is used: VZ ( ) = V r ( Z/Z r ) α V(Z) = wind speed at height Z V r = wind speed at the reference height Z r above the ground level α = wind friction coefficient The wind friction coefficient 16 is taken as α = 0.3. In this analysis, the height of a high-rise building was taken as the reference height (Z r =150 m). The calculated wind speed is then multiplied with the ODGV rotor rotational augmentation ratio of 1.8 (as shown in Table 4). This is the effect of using the ODGV. Therefore, the monthly wind speed at the height of 150 m in an urban area for years is tabulated in Fig. 7. The wind power is proportional to the cubic power of the wind speed approaching the ODGV. The power available in the wind can be calculated using the following equation: P = 0.5ρC p η g η ODGV AV 3 (1) (2) Table 1 Specifications of the wind turbine 17 Rated power 50 W Starting wind speed 2.0 ms -1 Working wind speed ms -1 Rated wind speed 10 ms -1 Maximum wind speed 35 ms -1 Swept area (height diameter), A 0.8 m 0.6 m Number of blades 5 Generator efficiency, η g 0.8 Efficiency due to ODGV loss, η ODGV 0.9 Rotor efficiency, C p 0.4 Air density, ρ kg/m 3 Fig. 8 Monthly global radiation in Sepang, Malaysia from year 2007 to 2009 ρ = air density C p = rotor efficiency η g = generator efficiency η ODGV = Efficiency due to ODGV loss A Darrieus-type vertical axis wind turbine was chosen for the system due to the advantages of blade profile, generator position, selfstarting behavior and noise level. The technical characteristics of a commercial VAWT are shown in Table Solar energy system Estimation of the solar energy is a function of the mean daily global irradiation, G s (kwhm -2 /day) array active area, A s (m 2 ) the PV module conversion efficiency, η pv and the solar power loss, K. Using the meteorological data from Sepang weather station, the following equation can be used to calculate the potential solar energy generation: E solar = G S A S η pv K Fig. 8 shows the monthly global radiation for three years (2007 to 2009) in Sepang, Malaysia. A stable output of solar radiation can be expected from this source, with the maximum solar radiation of kwh/m 2 occurred during the month of May The daily solar radiation of this source range from kwhm -2 /day, depending on the weather conditions in this area. The specifications of an 80 W mono-crystalline silicon solar PV panel are listed in Table 2. (3)

5 INTERNATIONAL JOURNAL OF PRECISION ENGINEERING AND MANUFACTURING Vol. 16, No. 7 JUNE 2015 / 1267 Table 2 PV panel specifications Peak power 80 W Maximum voltage 18 V Maximum current A Module performance data and dimensions Estimated PV module conversion efficiency, η pv 17.40% Estimated power/performance efficiency, K 80% Dimensions of module mm PV cells area 0.6 m 2 Estimated percentage of cell active area 75% Estimated cell active area, A s 0.45 m 2 Table 3 Comparison of self-starting wind speed and maximum rotational speed at free running conditions 13 Parameter Bare VAWT ODGV integrated VAWT Self-start wind speed (m/s) Maximum rotational speed at 6 m/s (rpm) Results and Discussions 4.1 Experimental results The results from the wind tunnel study are presented and discussed in the following sub-sections Wind turbine characteristics at free-running conditions A comparison of self-starting behavior for both configurations are summarized in Table 3. The bare VAWT started to rotate at 7.35 m/s. By using the same test conditions for the shrouded VAWT, the recorded wind speed was reduced to 4.00 m/s. This shows that the ODGV improves the self-starting characteristics of a VAWT, hence increases the operational hour of the wind energy device. At the fixed wind speed of 6 m/s, the maximum rotational speed for the shrouded VAWT increased by about 182% when compared to the maximum rotational speed of the bare VAWT Performance of VAWT At a fixed wind speed of 6 m/s, the data from the experiment for load assessment of the wind turbine for both configurations are tabulated in Table 4. The shrouded VAWT shows significant improvements over the bare VAWT where the maximum torque and steady rotational speed was recorded to achieve mn.m and rpm respectively. Further calculations show that the power generated by the shrouded VAWT increased by about 350% when compared to a bare VAWT, after calculating the losses due to bearing friction. 4.2 Estimation of wind-solar energy output and the effect of ODGV on the performance of the wind turbine Using the wind speed and solar radiation data shown in Figs. 7 and 8, and the Eqs. (2) and (3); the estimation of wind-solar energy output from the Eco-Greenergy TM hybrid wind-solar energy system can be carried out. Therefore, the calculated annual wind and solar energy generation in an urban area are kwh/year and 99.7 kwh/year, respectively. Table 5 shows the summary of the system s annual energy output. The total energy generated that can be expected from the system Table 4 VAWT performance at wind speed of 6 m/s with loading 13 Parameter after considering the energy used by the LEDs is kwh/year. This shows that the system can perform well as a standalone system that generates energy from renewable energy sources. The advantages of integrating ODGV into an existing wind-solar system are presented and compared with similar characteristics of the system without ODGV in Table 6. The extractable energy and operational hours of the wind turbine increase with the integration of the ODGV. Based on the original specifications of the selected wind turbine, the working wind speed is in the range of ms -1. The calculation on the performance of the wind turbine is therefore based on this range of wind speed. Any recorded wind speed that did not fall within this range is omitted from the analysis. On average, the number of operating hours increases by approximately 41% when ODGV is integrated with the system. Moreover, the energy output from the system increases by about 438%. 5. Conclusions Bare VAWT ODGV integrated VAWT Augmentation ratio Rotational speed (rpm) Maximum torque (mn.m) Power generated (W) Table 5 Calculation of the annual total energy generation Solar energy, (kwh/year) a Wind energy, (kwh/year) b Energy used by LEDs (2x15W)*, (kwh/year) c Total energy, (kwh/year) ((a+b)-c) *8 hours of lighting per day Table 6 The annual operating hours and energy generation of wind turbine in Sepang (Z r = 150 m) from 2007 to 2009 Number of Annual Operating Hours Annual Wind Energy Generated, kwh/year Without ODGV With ODGV Increment 41% 438% This paper introduces a novel renewable energy generation system designed to overcome the low wind speed conditions of urban areas through the use of the ODGV. The Eco-Greenergy TM system combines the hybrid wind-solar energy generation and energy-saving lighting features into one compact design. In this study, a VAWT is shrouded by an ODGV. The ODGV has a number of guide vane pairs to form channels in which wind is guided through, where its speed is multiplied (venturi effect) and finally interacts with the turbine blades at the exit. At a wind speed of 6 m/s in the wind tunnel, the rotor rotational speed recorded an increase of 182% at free-running condition. Furthermore, the power output at maximum torque for the ODGV integrated VAWT is 3.48 times higher than the bare VAWT. Assessment of both of these wind turbine configuration types (bare and integrated ODGV) with both having the same specifications (blade length, swept area and

6 1268 / JUNE 2015 INTERNATIONAL JOURNAL OF PRECISION ENGINEERING AND MANUFACTURING Vol. 16, No. 7 aerofoil profile) reveals that the ODGV integrated VAWT improves on the many disadvantages of a bare VAWT. Estimation on wind-solar energy output shows that the system can generate a total of kwh/ year. By comparison, the ODGV increases the annual wind energy output by 438%. This shows that the ODGV has great potential to be integrated into any existing wind turbine systems. Furthermore, the onsite energy generation capability of the Eco-Greenergy TM system eliminates the issues concerning conventional street lighting system such as trench wiring and landscape replacement after trenching. While the study has focused on the application of wind and solar energies to provide power for outdoor lighting, the system can also be used for other applications, i.e., to provide power for remote data gathering devices, flood monitoring system or emergency beacon for distress hikers. ACKNOWLEDGEMENT The authors would like to thank the University of Malaya for the research grants allocated (UMRG-RP015C-13AET and High Impact Research Grant, HIR-D ). Special appreciation is also credited to the Malaysian Ministry of Education, MOE for the Fundamental Research Grant Scheme (FP B). The authors would also like to thank the Centre for Research Grant Management Unit University of Malaya for the Postgraduate Research Grant (PG A). REFERENCES 1. Bhandari, B., Poudel, S. R., Lee, K. T., and Ahn, S. H., Mathematical Modeling of Hybrid Renewable Energy System: A Review on Small Hydro-Solar-Wind Power Generation, Int. J. Precis. Eng. Manuf.- Green Tech., Vol. 1, No. 2, pp , Bhandari, B., Lee, K. T., Lee, G. Y., Cho, Y. M., and Ahn, S. H., Optimization of Hybrid Renewable Energy Power Systems: A Review, Int. J. Precis. Eng. Manuf.-Green Tech., Vol. 2, No. 1, pp , Andrews, J. W., Energy-Storage Requirements Reduced in Coupled Wind-Solar Generating Systems, Solar Energy, Vol. 18, No. 1, pp , Precis. Eng. Manuf., Vol. 13, No. 7, pp , Hu, S. Y. and Cheng, J. H., Innovatory Designs for Ducted Wind Turbines, Renewable Energy, Vol. 33, No. 7, pp , Pope, K., Rodrigues, V., Doyle, R., Tsopelas, A., Gravelsins, R., et al., Effects of Stator Vanes on Power Coefficients of a Zephyr Vertical Axis Wind Turbine, Renewable Energy, Vol. 35, No. 5, pp , Yao, Y. X., Tang, Z. P., and Wang, X. W., Design based on a Parametric Analysis of a Drag Drive Vawt with a Tower Cowling, Journal of Wind Engineering and Industrial Aerodynamics, Vol. 116, No. pp , Knight, J., Breezing into Town, Nature, Vol. 430, No. 6995, pp , Oppenheim, D., Owen, C., and White, G., Outside the Square: Integrating Wind into Urban Environments, Refocus, Vol. 5, No. 3, pp , Chong, W. T., Fazlizan, A., Omar, W. Z., Mansor, S., Zain, Z. M., et al., Wind Tunnel Testing of 5-Bladed H-Rotor Wind Turbine with the Integration of the Omni-Direction-Guide-Vane, Proc. of 4th International Meeting of Advances in Thermofluids, pp , Chong, W. T., Fazlizan, A., Poh, S. C., Pan, K. C., Hew, W. P., et al., The Design, Simulation and Testing of an Urban Vertical Axis Wind Turbine with the Omni-Direction-Guide-Vane, Applied Energy, Vol. 112, pp , Chong, W. T., Poh, S. C., Fazlizan, A., and Pan, K. C., Vertical Axis Wind Turbine with Omni-Directional-Guide-Vane for Urban High-Rise Buildings, Journal of Central South University, Vol. 19, No. 3, pp , Chong, W. T. and Kong, Y. Y., Outdoor Light Harnessing Renewable Energy, MyIPO, PI , Patel, M., Wind and Solar Power Systems: Design, Analysis, and Operation, Taylor & Francis, pp , Saiam Power, 75W Mini VAWT, article_read_159.html (Accessed 19 DEC 2014) 4. Gabler, H. and Luther, J., Wind-Solar Hybrid Electrical Supply Systems-Results from a Simulation Model and Optimization with Respect to Energy Pay Back Time, Solar & Wind Technology, Vol. 5, pp , Ter Horst, E. W., Blok, K., Alsema, E. A., and Turkenburg, W. C., Optimization of Hybrid Autonomous Energy Systems, Proc. of 7th European Community Photovoltaic Solar Energy Conference, Vol., No. pp , Chilugodu, N., Yoon, Y. J., Chua, K. S., Datta, D., Baek, J. D., et al., Simulation of Train Induced Forced Wind Draft for Generating Electrical Power from Vertical Axis Wind Turbine (VAWT), Int. J.