Experimental study of latent heat storage using paraffin E46 A. Georgiev, R. Popov, A. Stoyanov Technical University of Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria

INTRODUCTION There are some opportunities to store the gained thermal energy – it could be done in the form of sensible or latent heat. There are some opportunities to store the gained thermal energy – it could be done in the form of sensible or latent heat. Most promising technologies for the accumulation of heat is to use the phase change materials (PCMs). They are products that store and release thermal energy during the processes of melting and freezing, evaporation and condensing. PCMs release large amounts of energy upon freezing in the form of latent heat but absorb equal amounts of energy from the immediate environment upon melting. Most promising technologies for the accumulation of heat is to use the phase change materials (PCMs). They are products that store and release thermal energy during the processes of melting and freezing, evaporation and condensing. PCMs release large amounts of energy upon freezing in the form of latent heat but absorb equal amounts of energy from the immediate environment upon melting. There remain three major trends in the solar systems using PCMs: There remain three major trends in the solar systems using PCMs:  development and selection of appropriate materials;  development of latent heat accumulators suitable construction;  to develop source-storage-load control strategies. Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria

A large number of phase change materials (organic, inorganic and eutectic) are available in any required temperature range. A classification of PCMs is given in Fig. 1. Fig. 1. Classification of PCMs Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria Different types of PCMs

Fig.2. Performance comparison of PCM, water and rock storage system Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria The concrete choice depends mainly on the following basic properties: - density, kg/m³; - melting point, °C; - specific heat capacity, J/kgK; - latent heat of fusion, kJ/kg; - thermal conductivity, W/mK; - volume change, %. A comprison between 3 types of PCM storages is done (Fig.2). CaCl 2.6H 2 O is used as a PCM. Performance comparison

Fig.3. Temperature change (paraffin Е53) A storage with paraffin as a phase change materials was constructed recently at the TU Sofia, branch Plovdiv. There was a choice between 8 types of paraffin. They have been studies at the same university. The tests have been done as follows – the same quantity of all the paraffin types was put in small plastic bottles. The paraffins are heated (the bottles are at that time in a thermostat). After reaching the melting point the samples are put in well insulated vessels with water. The temperature raise of the water is noted by means of temperature sensors. Fig.3 shows the temperature change of one of the mesured paraffins. Paraffin‘s investigation at the TU Sofia, branch Plovdiv Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria

est installation for study of PCM storage Test installation for study of PCM storage In 2013 year a test installation for study of PCM storage was developed at the Technical University of Sofia, branch Plovdiv. In 2013 year a test installation for study of PCM storage was developed at the Technical University of Sofia, branch Plovdiv. It contains the following main parts: It contains the following main parts: - selective solar collectors; - selective solar collectors; - phase change material (PCM) storage; - phase change material (PCM) storage; - water storage; - water storage; - some circulating pumps. - some circulating pumps. Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria

Fig.4. Set up of the test installation for study of latent heat storages Test installation Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria

Some components of the test installation Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria Fig.5. Selective solar collectorsFig.6. Pyranometer of the type Kipp& Zonen

Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria View of the test installation

Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria Some components of the test installation

Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria

Some components of the test installation Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria

Semiconductor Temperature Sensors DS1820 Some components of the test installation Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria

The paraffin E46 was thermophysically investigated. Raman investigation of the material revealed structural resemblance of the E46 sample. Here are some data: - the latent heat is to be measured as 176,77 J/g; - the thermal conductivity is 0,33 W/mK; - melting point – 56,5 °C; - volume change 12,4 %. Paraffin‘s properties Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria

It was decided to test the installation using a planning experiment. Three parameters were chosen as experiment factors: volumetric flow rate,m³/h; number of containers; power of the electrical heater, W. The experiment is conducted at three factor levels (lower, basic and upper): - volumetric flow rate - 0,675; 0,824; 0,973 m³/h; - number of containers – 13; 26; 39; - power of the electrical heater – 2400; 2800; 3200 W. They respond to the following basic conditions: - The measurement of the factors is of high enough precision; - The factors are essential; - All factors can be regulated directly during the experiment; - Every factor has quantitative value and can be controlled in its whole change interval; - The realization of all possible combinations of the factor values in their variation region limits is possible. Choice of experimental design Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria

Our Green Energy Team Here are the members of our scientific team: - Prof. A. Georgiev; Assoc. Prof. R. Popov; Assoc. Prof. D. Dzhonova; - Prof. A. Georgiev; Assoc. Prof. R. Popov; Assoc. Prof. D. Dzhonova; - PhD students: E. Toshkov; A. Stoyanov; S. Lishev; N. Vassileva. - PhD students: E. Toshkov; A. Stoyanov; S. Lishev; N. Vassileva. Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria

Some author’s articles [1] M. Bottarelli, M. Bortoloni, Y. Su, C. Yousif, A. A. Aydin, A. Georgiev. Numerical Analysis of a Novel Ground Heat Exchanger Coupled with Phase Change Materials. “Applied Thermal Engineering”, accepted for print. [2] E. M. Anghel, A. Georgiev, S. Petrescu, R. Popov, M. Constantinescu. Thermo- physical characterization of some paraffins used as phase change materials for thermal energy storage. J. of Thermal Analysis and Calorimetry, Springer, Vol. 117 (2), 2014, pp [3] A. Georgiev. Testing solar collectors as an energy source for a heat pump. "Renewable Energy", 2008, V. 33 (4) p [4] A. Georgiev. Simulation and experimental results of a vacuum solar collector system with storage. "Energy Conv. & Manag.", 2005, V. 46 (9-10) p [5] Roth, P., Georgiev, A., Boudinov, H. Cheap two-axis sun-following device. "Energy Conversion & Management", 2005, V. 46 (7-8) p [6] Georgiev, A., Roth, P., Olivares, A. Sun Following System Adjustment in UTFSM. "Energy Conversion & Management", 2004, V. 45 (11-12) p [7] Roth, P., Georgiev, A., Boudinov, H. Design and construction of a system for sun- tracking. "Renewable Energy", 2004, V. 29 (3) p [8] Georgiev, A. Mathematisches Modell eines Vakuumsolarkollektors mit Wärmerohr und Flachabsorber. Brenstoff, Wärme, Kraft, 1993, N° 12, p Experimental study of latent heat storage with paraffin A. Georgiev, R. Popov, A. Stoyanov TU Sofia, branch Plovdiv, Bulgaria COST Action MP1305 workshop "Applications, Dissemination and Outreach" April 2015, Sofia, Bulgaria