MEASUREMENTS ON SOLAR EQUIPMENTS TO PRODUCE HOT WATER IN DIFFERENT CLIMATE SITUATION AND DETERMINATION. THE EQUIPMENTS EFFICACITY

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1 MEASUREMENTS ON SOLAR EQUIPMENTS TO PRODUCE HOT WATER IN DIFFERENT CLIMATE SITUATION AND DETERMINATION. THE EQUIPMENTS EFFICACITY CÎRSTOLOVEAN Ioan Lucian, University Transilvania Brasov, Faculty of Buildings Engineering, A B S T R A C T The paper represents a theoretical and experimental approach on solar equipment use to produce hot water. The capability is one of the fundamental criterion referring to the achievement of quality and performance of the system.wich produce thermal energy Before the introduction of the statistical control of thermal energy production, a compatibility analysis is done which is supposed to establish if the set tolerances by specifications are compatible with the installations capacity of satisfying these demands. We need to evaluate the performance of a thermal energy production system This is given by certain characteristics, especially important being those which represent exigencies of comfort, for example of the thermal one, and economic exigencies in exploitation, predominant being the fuel consumption and implicitly its cost.. Received: January 2012 Accepted: January 2012 Revised: March 2012 Available online: May 2012 Keywords: reliability, durability, solar equipment, capability, thermal energy INTRODUCTION The heat load is at the basis of the dimensioning of the solar panels of the application we want to integrate. We will determinate the monthly and annual values for heat load. The annual heat load of the energy necessary must be compared with the energy delivered by the sun. This rate rises in summer time and decreases in winter time. The annual evolution of solar energy is considerably influenced by the position of the panels field. MATERIALS AND METHODS 1. Designing the solar system in the laboratory In the laboratory of the faculty was designed a solar system for producing hot water for 3 persons. The geographical dates of the building where the solar panels were placed are: Latitude 45,66 grd; Longitude 25,61 grd. The necessary volume of hot water is determined with the relation: V ac = a * N u /1000 [m 3 /zi] (1) where: a specific necessary of hot water at 60 C/ person for a day; N u number of persons from the building. According to the standard EN (Heating Systems in buildings. Method of calculation of requirements and systems efficiencies) the values for a are informative. For a new building with reduced loss of hot water, it can be considered a= 60 l/ day* person. For the case under analysis, for 3 persons, the volume of hot water [9] at 60 C is:

2 V= 3*60/1000 (2) V= 0,18 [mc/zi] (3) The volume V 2 of the hot water tank at 45 0 C is: The volume of the tank that was chosen: 300 l The daily energy for preparing hot water is given by the relation: V 2 = V T 1 /T 2 [mc] (4) V 2 = 0,27 [mc] (5) Q= V**c*T [J] (6) Q= 0,18*992,2*4182*45 [J] (7) Q= 33,6* 10 6 [J] (8) The daily energy expressed in kwh/day is: Q=9,33 [kwh/zi] (9) Annual energy: Q= 3405 kwh/an (10) The surface of the collecting solar panels [9] is determined with the relation: (11) where: Acol solar panels surface; K orient the positioning factor; SD solar coverage degree SN usage degree; Q cons energy consumed for preparing hot water; Q rad solar radiation / m 2. (12) RESULTS AND DISCUSSIONS This experimental study about the heating process of the water with solar panels was made in the faculty s laboratory. The measurements were made and recorded in csv files with the help of the vdialog program. The program offers the possibility to visualize the temperatures in the areas where temperature sensors were placed and of the functioning pace of the pump. From the multitude of dates recorded, for the capability analysis, we analyzed the temperature of the hot water in the boiler by the SB1, SB2 sensors, the climate temperature and the water temperature from the solar panel measured by the KOL 1 sensor. The sensors position is presented in fig 1. The

3 solar radiation was measured with Voltcraft equipment. For this paper the measurements were determined between the 1st of March 2011 and 30th of April From the data recorded by the computer, 9 days were chosen which were significant for the process of heating home water. The major criteria for choosing them were the diversity of the weather values and the intensity of the solar radiation. In this paper we present the graph recorded by the program and the graph made by the interpretation of the files recorded by the computer on the 5th of March The capability of the process of heating home water by means of solar energy The capability of the thermal energy process [2] (to prepare hot water) represents one of the fundamental criterion referring to the meeting of quality and performance of the system. Before the introduction of the statistical control of the thermal energy production, a compatibility analysis is done which is supposed to establish if the set tolerances by specifications are compatible with the installations capacity of satisfying these demands. The performance of a solar system s equipments needs to be evaluated. This is given by certain characteristics. Fig.1. The schema of the system of producing home hot water with solar panels The statistic control [1], [2] of the process is meant to supervise the proceedings of the process, essentially, its capacity and if the normal proceeding of the process contains deviations from the specifications in order to interfere in the process to have it corrected. A process is under control if it satisfies the demands imposed by the statistics of the control which are: a) regulated process; b) precise process; The production and distribution process of the energy is considered dynamically stable if the position and diffusion indices maintain in time the grouping centre and the diffusion field, according to the specifications.

4 This paper presents a capability analysis of the process of heating the water from the solar boiler at a temperature between C. The schema of the system that helped with the measurements is presented below. With the results of measurements on the system the statistic calculus [2] was done. The steps were: - from the number of the temperature values obtained by measuring SB1 there were chosen only those which are between 30 and 60 C. For the analyzed days, the number of these temperatures is N; - we calculated the absolute and relative frequency with which identical values were recorded of the SB1 temperatures; - locating parameters were determined; - dispersion parameters were determined; The results obtained are presented in Table 1. Table 1. The results of the statistic calculation When analyzing the results we concluded: the arithmetical mean, median and the mode have near values which means that statistic distribution of the measurement values is normal and actually symmetrical. The higher value of the dispersion demonstrates that we have a large area for temperature values. It is normal to be like this because the variation of solar radiation produced high variation of the hot water in tank. In the interval (xm-; xm+) (32,41; 41,25) there are 168 values out of 287, namely 58% from all values. Minimal temperature: 1,5 C- 9 o clock Maximal temperature: 4.6 C- 15 o clock Fig 2. The variation of the hot water temperature in the solar tank for March 5 th 2011

5 Sunday, 5 March 2011 Temperature min: 1,5 C-ora 9 Temperature max: 4.6 C-ora 15 Fig 3. The graphic made by vdialog programme for March 5 th 2011 Sunday, 5 March 2011 Temperature min: 1,5 C-ora 9 Temperature max: 4.6 C-ora 15 Fig 4. The position of the sun in relation to the solar panels for March 5 th 2011

6 CONCLUSIONS The solar system for producing home hot water in the faculty s laboratory is similar to the solar system design for a residential house with a number of three or four inhabitants. For this reason the results from the experimental measurements made in the laboratory can be used to establish the energetic efficiency of buildings. The capability study concluded that the system has the capability of producing home hot water necessary for a residential building. The temperature of the hot water from the solar boiler reached different temperatures depending on the solar radiation, but it should be noticed the fact that the solar system equipment produced hot water with a temperature higher than 55 C. In this case, the contribution of thermal energy produced by a heating source with conventional fuel would be zero which would lead to a decrease of the yearly energy necessary and would thus increase the energetic performance to the building. REFERENCES 1. MOCANU, R., UNGUREANU, N. (1982); Strength of materials, Material tests; Cap. Statistic design to experimental results, Ed Tehnic, Bucharest. 2. CÎRSTOLOVEAN, L. (2009), Contribuii privind realizarea performanei prin calitate în concepia i realizarea instalaiilor pentru construcii (Contributions concerning the fulfilment of the performance by quality in the development and achievement of the installations for building). PhD Thesis,Universitatea Tehnic Ghe. Asachi Iai, Ph.D. Advisor Nicolae Ungureanu, Ph.D.Prof.eng. 3. *** accesed at March-April *** accesed at March-April *** accesed at March-April *** accesed at March-April *** accesed at March-April *** Oventrop Software. 9. *** Vaillant-Solar systems design.