Development of a Model Wind and Solar Power Installation Comprising High Tempera
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Abstract
The investigation of main performance properties of the hybrid wind and solar power installation with application superconductive elements was carried out. In the frames of the study， both mathematical simulations and experimental testing were performed. The study shows some difficulties to be solved during mutual operation of the various high-temperature superconductivity （HTSC） devices， especially if they operate with semi-conductive systems.
Key words： Hybrid wind； Solar power installation； High-temperature superconductivity （HTSC）； Renewable energy； Simulation； SMES； Fault current limiter； Physical modeling
L. I. Chubraeva， V. F. Shyshlakov， M. A. Turubanov， S. S. Tymofeyev， D. A. Volkov （2013）. development of a model wind and solar power installation comprising high-temperature Superconductors. Energy Science and Technology， 6（2）， 64-70. Available from： URL： http：///index. php/est/article/view/10.3968/j.est.1923847920130602.2374 DOI： http：///10.3968/j.est.1923847920130602.2374
INTRODUCTION
Hybrid wind and solar power installations are drawing increasing attention due to high prices of conventional fossil resources and ecological problems of different regions of the world. The main aim of the researches in this field is focused on the improving of the overall efficiency of such installations. The objective can be obtained by： improvement of the solar panels power output， improvement of wind generator efficiency and improvement of control methods and algorithms for entire installation.
Solar and wind are intermittent energy sources as they vary over time and do not usually meet load demands at all periods. Among these two types of renewable energy， wind is a more affective source compared to photovoltaic due to its variability. Similarly， the photovoltaic system also depends on the weather conditions and can operate only at day-time. These two unpredictable energy sources standalone system will produce fluctuated output energy and thus cannot ensure the minimum level of power continuity required by the load.
There exist numerous combined wind and solar power installation developed by different companies， but most of them are based of application of conventional materials. Until the present moment superconductors find only limited application in such types of power installations， for example， American Superconductors （AMSC） offers a design of a similar combined system involving wind generator with HTSC. 1
The electrical scheme of the installation is presented in Figure 1.
Presented below are results of experimental and theoretical investigations of two HTSC elements： synchronous alternator with permanent magnets on the rotor and HTSC armature winding and SMES with HTSC winding and magnetic cores of amorphous alloy.
2. HTSC MODEL SYNCHRONOUS ALTERNATOR
The wind turbines are generally manufactured in a wide range of vertical and horizontal axis types. Vertical axis turbines have several advantages over the typical horizontal axis turbines， namely：
？ They can accept changes of wind direction with no problem；
？ The alternator can be fixed on the ground for easier access， rather than up in the air；
？ Generally they start rotation at lower velocity；
？ They produce less noise.
The general view of HTSC electrical generator with a wind turbine is shown in Figure 2.
Synchronous machines with axial magnetic flux and permanent magnets excitation possess the increased performance characteristics and the lower overall dimensions in comparison with conventional electric machines （Yi， Agelidis， & Shrivastava， 2009）. Application of the rare-earth permanent magnets as an excitation element of electric machines allows canceling the excitation losses and permits to exclude the exciter. Axial magnetic flux is perpendicular to narrow edge of HTSC tape， resulting in reduction of losses. Moreover armature coils of a simple circular form may be used. This fact is substantial for HTSC. The coils form one or two layers， providing a reliable， simple and more cost-effective winding （Ahmed， & Miyatake， 2006）. The rotor has 8 magnetic poles， each pole comprises two magnets on both rotor sides （Figure 3， b）. The magnets are rare-earth NdFe-B. The rotor body is made of aluminum. The alternator rating is 5kW.
The armature of the generator is of a slotless design with a stator core made of amorphous alloy tape. The stator winding consist of 12 pancake single-layer HTSC coils divided into two layers （upper and lower）， each stator layer is mounted on a separate stator disk （Figure 3， a）. It is worth nothing that the alternator may be of a multi-disc design with a multiphase armature winding. The entire alternator is emerged in liquid nitrogen.
The armature and the rotor are mounted in a hermetically sealed vessel， which acts as a cryostat （Figure 3， c）， the outer surface of the vessel is covered with a layer of a thermal insulation made of cellular rubber substance （Figure 3， d）. The generator was tested at liquid nitrogen temperature， it took 2 hours to cool down the generator to the temperature of 77K. The cooling process was controlled manually and the dynamics of the process is shown in Figure 4.
c. Control circuit for the hybrid system operation is a complicated one and is to be responsible for both electrical and cryogenic equipment reliable functioning.
REFERENCES
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