Innovative power engineering

Due to their difference in productive process, there are some differences in four PV modules' efficiency. Comparing with four PV modules' output, some corrections in efficiency must be done. The output power ration and scale factor of PV modules with respect to PV module 2 (towards the south with tilt angle of 35°). For offsetting the influence on efficiency difference, the actual output of PV modules must multiply by the scale factor before comparing with each other.

Based on Fig 6, it can be shown that the solar module oriented towards the east at an angle of 30° generates electrical energy of 267.93 Wh, which is maximal electrical energy for the East. In Fig. 7 Solar module oriented towards the South gives the greatest value for electrical energy for the angle of 40° of 346.77kWh, which is the maximum registered value for electrical energy. It is shown in Table 2 that for fixed angles of 30, 35, 40 and 90° solar module oriented towards the South gives the greatest values of electrical energy and for the angle of 40° the greatest value is given by a solar module oriented towards the South. Values of obtained electrical energy for the East, South and West positions for the angles 30, 35, 40 and 90°, are shown in figures 6

On the basis of the above mentioned without shadow, the conclusion can be shown as following:

1) Solar module oriented towards the East gives the maximum values of electrical energy in March and April. The minimum values of electrical energy in November and December .The angle of 90° generates the minimum value for electrical energy. The angle of 30°generates the maximum value for electrical energy.

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2)Solar module oriented towards the West gives the maximum values of electrical energy in March and April. The minimum values of electrical energy in November and December .The angle of 90°generates the minimum value for electrical energy. The angle of 30°generates the maximum value for electrical energy.

3)Comparing with oriented towards the West, PV module orented towards the East generates more electrical energy. It is the reason that the temperature is lower in the morning so that it makes PV module efficiency higher.

4)Solar module oriented towards the South gives the maximum values of electrical energy in January and December. The minimum

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values of electrical energy in July and June. The angle of 90°generates the minimum value for electrical energy. The angle of 40°generates the maximum value for electrical energy.

5) PV system is mainly influenced by the solar radiation and ambient temperature. In winter solar radiation is weak but the environment temperature is low, the PV module efficiency is higher. In summer solar radiation is intensive, but the environment temperature is high. The PV module efficiency is low. All in all, the power generation capacity is greater in winter than in summer. According to the climate in Yulin, the winter is sunny and summer is rainy. The experimental data conforms to this trend.

Conclusion

1)Solar module oriented towards the South gives the greatest values of electrical energy for all the chosen angles.

2)Considering the actual installation, when PV arrays must be installed towards the West or the East, generating capacity of 90° angle is lowest and its electrical energy is only 50 % of the maximum value. If it is only installed on the building of facing to east or west, PV system should be installed towards the east.

3)Because of influenced by solar radiation and ambient temperature, PV module's electrical energy is maximum in winter and minimum in summer throughout the year.

References

1.Ibrahim D. Optimum tilt angle for solar collectors used in Cyprus // Renewable Energy. – 1995. – No. 6, 7. – . 813 819.

2.Iqbal M. Optimum collector slope for residential heating in adverse climates // Solar Energy. – 1979. – No. 22. – P. 77 79.

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THE RESULTS OF OPERATION AND TESTING

OF VERTICAL AXIS WIND TURBINES

Solomin, Sirotkin, Solomin

The research in wind power area at South Ural State University have demonstrated a high indicators of electric energy generation by 0.1-30 kW power family vertical axis wind turbines. The methodology of rapid (clustering) R&D of experimental prototypes, developed at the University, is worth the systematic approach while design the electromechanical components, showing their advantages as well as the competiveness of components. The research showed both advantages and disadvantages of development process and the components design, which is normal under the R&D experimental prototyping stage. The main problems are the unbalance of vertical axis rotor, excessive mass of turbine operating part andnon-stable operation of software for power controller. The tasks of further research include the reduction of working components mass, rotor unbalance removal by dynamic balancing, and improvement of power takeoff control software. The significant areas of research should be a further development of air foil materials, efficient vibration dampers, aerodynamic and electromechanical control of rotation frequency.

Introduction

Wind power is one of the most rapidly developing branches of the World Power Industry [1]. China and USA have shown the extremely rapid growth [2]. Significant success during the last 5 years have India, Brazil, Romania and several African countries [3]. In Russia this industry segment is still not developed for several reasons (lots of hydrocarbon deposits, dominating development of heavy industries, etc.). Though the demand in the devices on the base of renewable energy sources (RES) is being felt in all industry areas. Even oil-gas companies are involved into the RES development – JSC “Gazprom” researches the ways of application of wind turbines (WT) in pumping equipment, JSC “Lukoil” is interested in the arrangement of gas stations with autonomous power supply on the base of wind-solar power plants. In progress there search in RES area by a members of Rocket-Space Corporation. In particular the Scientific Research Institution of Space Device Development made a deep research of wind turbine application in Arctic conditions for power supply of GLONASS and GPS apparatus [4].

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A very rapid development of wind power is traditionally concentrated on megawatt class with 1-10 MWatt unit power. However from the economic point of view this approach is not winning as it might first imagined [5]. Talking about the dependence of cost price on the power level or mass-dimensions parameters, it is necessary to note that the production of small wind turbines is much more efficient and profitable than of big ones. This comment is proved by the sample of comparison of Horizontal Axis Wind Turbines (HAWT). If we will take 100WTswiththediameter10meters, and compare them with 1 WT

with the diameter 100 meters, then their total swept areas will be equal (accordingly ( 100• •d2 = •D2or 100• •102 = •1002).

The mass of WT rotor is in cubic dependence on its diameter. Then the masses of rotors of all small WTs will be less than the mass of one big WT (100•m ~ 100•d3 = 105 – order of mass of all small WTs, and M ~ D3 = 106 – order of mass of big WT). It is obvious that the mass of one big WT is 10 times higher than of several small WTs with equivalent power generation, which determines its high cost price. However we should note that the specific operational costs of small WT will be higher than of the big megawatt class one. Though it is also obvious that it is impossible to “cover” all power demands by one type or size of WT, and therefore it is necessary to accept the existing variety of WTs similar to the analog in automobile industry.

Vertical Axis Wind Turbine operation is based on the effect of aerodynamic lifting force of the wing. This type of WT is one of the most prospective areas of wind industry because of their advantages – independence of operation on wind direction, low rotation speed, high wind power usage coefficient (power coefficient Cp), and low levels of mechanical and aerodynamic noise. However the lack of strong theories of component calculation, disadvantages in mass-dimensional characteristics and rotor unbalance, moderate the development of this relatively new area in wind power [6].

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During the R&D works we have obtained the following results in the form of experimental prototypes of vertical axis wind turbines (VAWT) and both autonomous and grid-tied hybrid wind-solar power plants (Fig. 1–4):

Fig. 1. 3 and 4bladeone-tier and two-tiermicro-WTsfor 0.1-0.5 kW power, and hybrid energy plants on 0.2–0.6 kW

Fig. 2. 3, 4and 9blade multi-tier micro-WTs on 1 kW power

Fig. 3. 4 and 6blade two-tier WTson3 kW power installed on parking pots, buildings, engineering constructions (sea buoy)

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Fig. 4. 6blade two-tier WTon30 kW power is included into 90 kW wind-diesel power plant

Brief characteristic of the developed turbines: vertical axis wind turbines:

Rotor of Darrieus type, one or multi-tier. Operation of rotor is based on the generation of rotating torque caused by aerodynamic (lifting) forces. The blades are made of reinforced fiber plastic with supporting flange and wing mechanization made at one forming. Limitation of rotation frequency on high level is controlled by aerodynamic centrifugal governors located on horizontal traverses. Alternatoris synchronous (valvular) on NeFeB permanent magnets, power takeoff is controlled by tip speed ratio control. Inverter is to be purchased. Hybrid wind-solar plants are equipped by solar panels on 100-300 W nominal power and hybrid energy flow control system.

Typical structure of the wind turbine in demand, two-tier 6-blade wind turbine, is shown in Fig. 5.

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Fig. 5. Typical basicstructureofthewind turbine

During the deep scientific and engineering research and design of experimental prototypes and their testing, some advantages and disadvantages were obtained.

Advantages:

Operation of WT doesn’t depend on wind direction;

Self start on low wind speed up to 2 m/s;

Power generation from 3 m/swind speed;

Low level of noise (comparing with analogs);

Aerodynamic stabilizing (limiting) of frequency rotation. Disadvantages:

Several resonances of self oscillation harmonics and rotor unbalance (possible reasons: poor production quality, non-oval supportrings construction, non-vertical blade orientation, nonhomogenous material structure of parts);

Blades may fail in the joints of connection to the support components because of sign-alternating oscillations;

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Aerodynamic governors operate not synchronically and cause the rotor unbalance;

Mechanical brake system is not efficient;

Mass of parts is higher than required as calculated for the cut off wind speed 60 m/s;

Cost of inverter is high due to the small consuming volume. During 2010–2014 we analyzed the cost price of components of

the experimental 3 kW power WT-3 as the most needed per market research (in prices of the same time period) including all services and works (basic typical set), Table 1.

Table 1

Cost price of components of the experimental 3 kW power WT-3

The main parameters of the most demanded WTs is shown in Table 2.

The result of R&D is 0.1-30 kW power family of vertical axis wind turbines. The result of research is the above mentioned advantages and disadvantages which reflect the new tasks indicated below.

The solving of designer problems is closely connected with the research of economic indicators. Below we have shown the tasks which are to be solved for each component taking into account the appropriate technical, economical and safety requirements.

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Component: Rotor (Fig. 6). The task is to reduce the mass of the component keeping or improving the same durability.

Possible ways and technologies to be used:

Hub mass reduction;

Aerodynamiccontrolofblades;

Support structure may be either the ring or the hexahedron;

Removal of all rods and guy wires to reduce air resistance (drug

force);

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