Evaluation of employment of solar and wind systems in domestic and agro-industrial use
André Friderichs, Weslei Ambrós, Uilian Pappis, Cicero Nogueira
Universidade Federal de Santa Maria, Chemical Engineering dept.
Polytechnic College of the Federal University of Santa Maria, CPolUFSM
Santa Maria, Brazil
Abstract —For being ideas divulged as solutions for the development of a clean energy matrix, it is right to select the renewable energies as a theme of study and demonstration. In this way, this paper aims at evaluating the employment of solar and eolic energies in domestic and agro-industrial use. It accompanies the operation of a solar heater, a photovoltaic panel and two eolic systems of direct and indirect generation. The heating systems were shown to be satisfactory, whilst the direct eolic system presented low performance due to the presence of wind-breakers. It is hoped that together with the application, the prototypes will be demonstrative and will help in the search for technical solutions for the actual energy panorama.
Keywords-component: renewable energies; solar heating; eolic energy; engineering education.
I. Introduction
Considering the great dependence of a non-renewable source of energy such as petroleum, and that the reserves of this will be exhausted within several decades, the best attitude to be adopted is the change in the world’s energy matrix. On this context, the use of renewable energy sources presents itself as a promising alternative to face the actual energy challenges and to minimize the environmental impact. The use of renewable energies consists basically in taking advantage of solar energy directly (photovoltaic and thermal solar energy) or in their indirect forms: biomass, eolic, hydraulic, etc.
The development of a cleaner energy matrix is selected as an object of study and demonstration because it is the most divulged ideas a solution for sustainable growth. One of the ways to promote this diffusion consists in approaching secondary school pupils through the direct transfer of knowledge by the inclusion of themes in the different subjects which form the timetable of education such as: physics, chemistry, mathematics and biology. As well as this, it is aimed to provoke the interest in the actual scenario of world energy, critical thinking about this theme and the search for renewable energies as a necessary alternative, especially in what refers to the generation of energy.
In this context, through experiments undertaken in the Polytechnic College of the Federal university of Santa Maria (CPolUFSM) aimed at evaluating the employment of solar and eolic renewable energies in activities such as irrigation, washing of birds, illumination and water heating for human bathing. In Figure 1 there is an outline of the arrangement of the experiments carried out at CPolUFSM, as well as their final uses.
Figure 1- Scheme of the utility of application of eolic and solar energy at CPoliUFSM
II. Materials and methods
All the equipment is located at CPolUFSM. The systems installed are the following:
- Solar heating collector;
- Eolic system consisting in windmills with multiple blades for direct bombardment;
- Indirect systems of electrical energy, composed of an wind turbine and a hybrid configuration between a second wind turbine and a photovoltaic.
The system of solar heating was installed on the roof of the hydroponic laboratory (Figure 2), totally positioned to the geographic north (horizontal inclination of 35º and azimuthal deviation of 10º), in order to guarantee a greater daily insolation. The assemblage installed is composed of a solar heating collector by water lamina, thermal reservoir (0,1m³), water tank (0,017m reservoir (0,1m³), water tank (0,017m³), hydraulic pump (560w) and polyvinyl chloride and polypropylene connections. The collector has an area of 1m² being made of two dark sheets of stainless steel, 304 trimmings welded together with approximately 0.003m free space between them, which is filled with water. – The function of the water tank consists of stopping the water flowing under pressure into the thermal reservoir.
Figure 2– Solar heating system installed for testing.
The tests consisted in measuring the temperature of the water leaving the collector in order to determine its potential of utility for use in showers and in the pre-heating of water for the boiler (Figure 5). The tests were undertaken in the period from 9 am until 5pm on June 6th and 7th which corresponds to the daily period of insolation over the collector at this time of the year. To verify the degree of influence of circulation in the behavior of the outgoing temperature, the first test on June 6th was undertaken with natural circulation, whilst the second test on June 7th was undertaken with the help of a hydraulic pump operating with a flow of 1.16 x 10-4 m³/s.
The eolic systems used are composed of a windmill with multiple blades manufactured by hand installed in the sector of fruit cultivation and a similar model of commercial manufacture, located near the sector (Figure 3). Both are installed at 10 meters high. Waterwas used from streams and rainfall. The evaluation of wind velocity was measured by an anemometer of the anemo type. To estimate the eolic potential data from the Air Base of Santa Maria (BASM) and the Agrometeorological station of UFSM was used. The volume pumped was measured by volumetric method.
Figure 3– Windmills with multiple blades: commercial (left), handmade (right).
The wind turbines of the indirect system have configuration of the horizontal axle (Figure 4), each with a nominal potential of 160W, and are installed on top of a water tank 35 meters high. The two models are connected individually to a group of batteries located in a room at the side of the water tank, where there is a control board which controls the charge of the transformer used to convert the current supplied (12V) into alternate current (110V).A photovoltaic plaque of 12V and 85W is connected to the same group of batteries of one of the wind turbines, characterizing a hybrid system, whilst the other wind turbine operates individually.
Figure 4– Photovoltaic plaque (left) and wind turbines (right) installed at the Polytechnic College.
III. RESULTS E DISCUSSIONS
A. Solar heating system istema de aquecimento solar
In the solar heating system, the temperature of the water consumed showed a gradual rise in the period between 9am and 2 pm. The variation of temperature was more accentuated when the system operated under pumping action, as shown in Figure 5. From 2pm, the temperature was maintained approximately constant when the system operated with natural convection whilst the system of forced convection continued to rise after this period. The final temperature for each test was 42.4°C for operation with free convection and 46.5°C for forced convection, indicating that the first could be used for heating showers and the second, due to the higher final temperature for pre-heating water for boilers.
Figure 5 – Temperature in utilities consumption.
B. Eolic system for direct pumping
In the direct system of pumping, the eolic collector of handmade manufacture presented a flow of pumping of 0,025m³/hour as an average wind velocity of 2,86m/s and 0,066m³/hour with the highest wind velocity of 4,66 m/s. In this band of flow, the pumping was considered to be too small to which needed an irrigation of 5.000m³/ha per year. We believe that the low yield in the pumping system was due to the existence of wind-breakers in the four quadrants of the region where they were installed. The pre-fabricated windmill installed in a locality free of wind-breakers, showed a flow of up to 1,8m³/hour for a wind velocity of 2m/s, more than sufficient to attend the needs of water for fruit trees.
C. Indirect systems
No rigorous testing was undertaken with the hybrid system, however, irrigation data in the green houses show flow of water pumped up to 0,36m³/hour, which attends the demand for water for irrigation sufficiently. Additionally, the wind turbine which operates in isolation attends in a satisfactory was the need for energy to illuminate the green houses.
IV. CONCLUSIONS
It can be concluded that the systems of generation of renewable energy implanted at CPolUFSM are in a general way, useful in the complementary supply of energy for the different utilities. The use of the solar heating systems was shown to be satisfactory, as the water presented a final temperature sufficient to be used at the points of consumption. Thus, it is noted that it is possible to substitute, in part the usual method of water heating in the agro-industry, as the water enters pre-heated into the boiler, in this way economizing wood and reducing pollution due to its burning. Analogously, in the heating of water for showers, we perceive that the system presents a nearly constant temperature after a certain period of insolation, in this way the consumer has hot water available for a longer period of time be able to irrigate the fruit trees.
In the same way, the photovoltaic and indirect eolic systems are demonstrated as being viable to complement the demand of energy in the pumping of water for irrigation for fruit trees. On the other hand, the direct eolic system located near to the fruit tree sector showed low efficiency because of the existence of natural barriers (wind breakers) in the vicinity, in contrast with the windmill installed at a greater distance.
Lastly, it is believed that the initiatives referring to the use of renewable energies in simple application, as well as being shown to be useful and efficient, awakens the interest of the secondary school pupils in the technological panorama and awakens their participation in the search for technical solutions for problems that affect society.
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