R E V I E W R E P O R T

Dr hab. inż. Dorota Chwieduk, prof. PW Politechnika Warszawska Warszawa, 30.05.2018 W y d z i a ł M e c h a n i c z n y E n e r g e t y k i i L o t n i c t w a I n s t y t u t T e c h n i k i C i e p l n e j 00-665 Warszawa, ul. Nowowiejska 21/25 R E V I E W R E P O R T PhD thesis Dynamics of thermal insulation modified by phase change material submitted by MSc. Eng. Anna Wieprzkiewicz 1. A base for elaboration of the Review Report The review report has been elaborated with regard to the letter dated on 11.04.2018 sent by the Dean of the Faculty of Process and Environmental Engineering of the Łódź University of Technology, Dr hab. Piotr Kazimierski, prof. PŁ. According to the decision of the Board of the Faculty made on 12.01.2018 I have been invited to prepare the Review Report of the PhD thesis Dynamics of thermal insulation modified by phase change material submitted by MSc. Eng. Anna Wieprzkiewicz. The review report has been elaborated on a base of the thesis submitted by MSc. Eng. Anna Wieprzkiewicz for the degree of PhD. 2. Characteristics of the research studies and evaluation of the thesis 2.1. The content of the thesis The thesis contains 196 pages of 8 Chapters, References and 2 Annexes. The thesis is well written. The structure is orderly, all chapters are connected in a logic way and the whole is concise. Much information and results of the research work are presented in graphical form or listed in tables. There are 74 figures and 15 tables in a main body of the text, and 8 figures and 1 table in two Annexes. They give very clear picture of the research work that was done by the candidate. References are put at the end of the thesis. The total number of publications to which the candidate refers to is 150. The candidate is a coauthor of four papers published in the international journals. Chapter 1 (6 pages) is an introduction to the thesis. It presents briefly the main aim and scope of research, the motivation for the thesis and the main hypotheses. Chapter 2 (29 pages) is based on a literature review on Phase Change Materials - PCM applications in buildings. The chapter is focused on description of the PCM properties, methods for examination of those properties, and integration of the PCM with building materials and components. The literature review presents also theoretical models of the latent heat storage and simulation tools of dynamics of buildings. Chapter 3 (12 pages) presents contribution of the candidate to the mathematical model calculating latent heat storage in the building wall in the ESP-r simulation software. Chapter 4 (39) describes some fundamentals of the latent heat storage with regard to the positioning of the PCM in the wall structure. Mathematical model of dynamics of the wall

with the PCM is formulated for given conditions. The boundary conditions are formulated. Methods of evaluation of the latent heat storage effect are described and analyzed. The chapter ends with recommendations for experimental analysis. Chapter 5 (31 pages) presents the experimental part of the research studies. Construction of the experimental façade is described with focus on preparation of the PCM components. Testing methods of the PCM main properties are presented. Monitoring systems with data acquisition system and weather sensors are described. In Chapter 6 (25 pages) some results of the long-term in situ measurements are presented, verified and analyzed. Different structures of the wall with different additives of the PCM panels are considered. The decrement factor and the time lag are analyzed in details. Chapter 7 (10 pages) presents the experimental validation of the proposed theoretical model described in chapter 3. Chapter 8 (4 pages) presents summary and conclusions of the research studies performed. It ends with the highlights of the work. Annex 1 presents calculation procedure implemented in ESP-r software (15 pages). Annex 2 presents results for RT8HC PCM material in figures and one table (8 pages). 2.2. Evaluation of the content of the thesis The thesis represents the candidate s own work with well thought out ideas for solving the problem under consideration in the thesis, and results of experimental and numerical studies. This thesis gives evident added value to research dealing with modern problems of energy efficient buildings, focusing on technologies based on latent heat storage, showing and documenting the possibility of improving the energy performance of buildings through the application of Phase Change Materials in a novel insulation component of the wall structure designed, constructed, modeled, investigated and validated by the candidate. The thesis makes an original contribution to knowledge concentrating on reduction of energy consumption in buildings and new effective storage methods based on application of the latent heat capacity materials in a structure of the envelope of buildings. In Chapter 1 the candidate in a clear way underlines the role of thermal capacity of building materials in creating the energy balance of a building. Development of a novel dynamic insulation component with latent heat capacity is presented as main aim of the studies. The chapter presents briefly the thesis outlines and main hypothesis, which have been proved thanks to research performed by the candidate. Chapter 2 based on a literature review shows good recognition of the state of the art in the scope of the subject of the thesis by the candidate. However, it would be good to explain some issues. 1. How does the candidate define the effectiveness of the PCM application (page 14)? In the thesis the effectiveness of the PCM and its application has been mentioned many times, so it is good to define it at the beginning of the dissertation. 2. There are different parameters in this chapter, page 34-36, but only few is defined, and none of them is presented with units. It makes sometimes difficult to understand what the author had in mind. It is pity, that the candidate did not put the list of symbols and abbreviations at the beginning of the thesis. It would make more clear understanding some sections of this and next chapters. 3. At the end of the page 34 it is written: Nevertheless, since PCM is incorporated in the building envelope (thus convective heat transfer can be neglected) However, it is not clear what convective heat transfer and where exactly: in the wall or outside it? And why?

4. There are many abbreviations in chapter 2.3.3, only few of them are described. When the author writes about the simulation tools it would be good to give a short description of all of them, and write something more about the ESP-r software, which is applied for calculations by the candidate, and not everybody of future readers must be aware of main features, benefits and limitations of this tool. Chapter 3 shows ability of the candidate to develop simulation studies and good knowledge of modeling in the ESP-r software. Procedure of calculating the latent heat storage in the building wall component is a modification of the mathematical model in the ESP-r. This procedure includes two new subroutines implemented in the model, what is the original part of the simulation study with regard to determination of the dynamic performance of thermal insulation enhanced by phase change materials. The important achievement of the candidate is described in the last paragraph of the section 3.1 and it should be underlined in this report: The newly developed subroutine SPMCMP57 was tested by ESP-r developers, accepted and included in the commercial release of the source code in July 2017.The enhancements of the PCM model is described in section 3.2 of the chapter. The chapter represents an interesting and original part of the study. It is necessary to underline that the candidate is capable of transforming the physical model of the investigated phenomena into a mathematical model and incorporating it into the numerical software. However, it is necessary to point out some issues. 1. The candidate underlines the special material properties, which are necessary for calculation of the latent heat storage (page 41 and 42). So, how are defined two coefficients of the linear function a (J/(kg K 2 )- and is it really linear? and b (J/(kg K), what is the physical meaning of both of them? 2. The numbers in equation (9) and (10) do they have units? (it looks they do), and how the equations were formulated? What was the base for such approximation? It can be read, that those equations are not the candidate s equations, but it is good to explain their physical meaning. 3. Page 42 last sentence how the latent heat accumulation is defined? (it is also mentioned in other parts of the text body e.g. page 45) 4. Page 43 why there are no symbols of the material properties? 5. Page 43, last sentence - Due to the fact that all materials tested experimentally could be characterized by the quadratic function of latent heat accumulation with good accuracy what does it mean? It will be good to explain that statement. 6. How L max can be defined? page 46, 50 (equation 16). Chapter 4 defines theoretical problem to be considered. The candidate presents the theoretical analyses of thermal properties and positioning of the PCM layer in the building wall component. A comprehensive simulation analysis of thermal performance of the lightweight wall enhanced with PCM has been presented. Methods for the assessment of the latent heat storage efficiency have been described. It is evident that the candidate has analyzed carefully the problem of research and has added the own input for solving the problem. Some remarks and questions are presented below. 1. It must be underlined that in our climate in a case of opaque walls the impact of solar energy is noticeable if these walls are not insulated. If insulation is applied the effect of solar radiation can be neglected. Solar radiation absorption is a surface phenomenon. The surface temperature can rise significantly and the heat transfer takes place between that surface and the ambient environment (mainly through forced convection). The heat transfer trough the wall is stopped by the insulation.

2. What does it mean: optimal transition temperature required to obtain the highest efficiency?- page 55. 3. Page 56 It is written: The thermo-physical properties, such as conductivity, density and specific heat, differed for layers A and B but were assumed constant. However, these parameters for the layer B are not constant. They are changing during the phase change. It is necessary to explain this assumption. 4. Page 58 - It is written: the heat exchange processes between the internal air and wall surface were described by convection and radiation boundary conditions. However, for such situation the properties and temperature of the laminar air layer at the wall surface not the wall surface should be taken into account. 5. Figure 15 is not true. Direct solar irradiance (W/m 2 ) (not radiation) can be never so high in any month of a year in any part of the Earth, especially in Poland high latitude country! In Poland in winter global (direct + diffuse) solar irradiance cannot be higher than 300 W/m 2, because of astronomical correlations of the Sun and the Earth position in the sky. It is necessary to explain data presented in Figure 15. 6. According to the equation (32) the LHSE should be defined as effectiveness not efficiency. What is a difference between effectiveness and efficiency? The title of the section 4.4.4 the same question can be put: effectiveness or efficiency? 7. Section 4.4.1, page 74 it is written Based on these results, it may be observed that only the external position of PCM (ξ = 0) enables a maximum use of the latent heat storage potential in a daily cycle. It is obvious without studies, because the melting point of the PCM is so low (annual average ambient air temperature), that the temperature like that one never happens in indoor conditions. It is always necessary to determine the melting point temperature of the PCM in heating (winter) and cooling (summer) seasons with regard to the required indoor air temperature in these seasons, which is not the same. Always the melting point temperature of the PCM required in summer is higher than the melting point temperature required for winter. And of course, the melting point temperature should be selected with regard to the position of the PCM in the wall, and it is different for external, internal and in-between positioning. 8. Page 88 it is written: The whole analysis was carried out taking into consideration a suitable transition temperature of the PCM according to its location in the wall. It is necessary to explain that, because the results presented in this Chapter show that only two cases of temperature were considered: 8.5 C and 25.8 C, and such temperatures are not suitable for all positioning of the PCM layer in an external wall. Chapter 5 presents the experimental set-up development with experimental façade construction. The candidate presents new methods of PCM integration with external envelope of the building. On the basis of theoretical considerations new methods of PCM applications were developed and tested. Perlite with different particle sizes was tested at the experimental stage and then specific fraction has been chosen to be applied in the façade construction. Then, another new approach using polyurethane (PU) foam has been investigated and applied in long-term measurements. The main concept of this idea was to add PCM to the twocompound PU mixture before its expansion. This allowed the material to be closed in air pores of the PU foam. It is necessary to underline that the candidate has observed that the addition of PCM resulted in lower volume expansion and lower temperature caused longer volume expansion of the foam. The methods described are novel and the whole process of preparing the material to apply in the façade is very innovative. It gives an added value to new construction of external walls of high thermal capacity and to research studies in this field. However, some questions should be answered. 1. The twin experimental facades west and east are in different environmental conditions, due to the wind impact and solar irradiation. How was it taken into account in simulation studies?

2. Due to the fact that the tested façade was divided into 12 sections, and only two sections were of the same structure (in result 6 different structures constituted the façade), the indoor climate was influenced by heat transfer through 6 different types of wall structure and a window. In addition every of the wall sections was affected not only by outdoor and indoor conditions, but also by the vicinity of another section of a different structure. Temperatures of the internal surface and inside of the each section were influenced by the heat transfer from the sections in such vicinity. How was it taken into account? How the boundary conditions for the edges of every section were formulated? 3. Page 93 it is written: From the outside the façade was covered with PV panels at a distance of 10 cm from the insulation panels, leaving a ventilated cavity. This means, that external conditions of the experimental set up (in result boundary conditions in the mathematical model) are different than the conditions simulated in the ESP-r software (chapter 3). It is necessary to explain this situation and discuss the problem. The external surface of the wall, i.e. the PCM external layer surface of the experimental set up is in different solar radiation and thermal conditions than it was described in Chapter 3. Solar radiation incidents on the PV panels and is absorbed there. The PV panels are opaque and there is no solar radiation incident on the external layer of the wall. Solar radiation causes the photovoltaic effect in the PV modules. Part of the energy of photons is used to create that effect, but the rest causes the increase of the internal energy of the material of the PV module. In result temperature of the PV module can rise very high to 60-80 0 C. In consequence the temperature in the air cavity is much higher than temperature of the ambient air. How this phenomenon is taken into account in simulation studies? 4. The next questions to the same sentence as in point 3 above (the façade was covered with PV panels at a distance of 10 cm from the insulation panels, leaving a ventilated cavity) are following: how the cavity is ventilated, what type of air movement is there, how the heat transfer and mass flow in the cavity can be compared with the air movement caused by the wind at external surface of the façade? How the boundary conditions should be changed because of different situation in the experimental set-up than in the simulation model described in Chapter 3? 5. It must be underlined that The façade covered with PV panels at a distance of 10 cm from the insulation panels, leaving a ventilated cavity, belongs to so called BIPVT Building Integrated Photovoltaic Thermal systems very innovative solutions of the energy upgraded solar façades, which serve not only as an energy saving envelope of the building, but as well as the energy generating system. Such BIPVT systems are under intensive theoretical and demonstration studies in Europe. It is pity that it has not been mentioned in the thesis. The experimental studies performed by the candidate give a high added value for development of this innovative BIPVT technology. 6. What has happened in Figure 44? 7. What type of paraffin is considered in Table 10 an 11? Why temperatures T 0 in Table 10 and 11 are so different? 8. Page 119 it is written: In order to comprehensively investigate the efficiency of the proposed solution. What does it mean the efficiency in this sentence? 9. Page 0 120 - In a description of weather parameters the candidate writes about measurements of direct solar radiation it is a mistake direct solar radiation can be measured directly. The global solar radiation is measured on horizontal surface (direct + diffuse) and the diffuse radiation (fig.54. b). It is also possible to measure so called hemispherical solar radiation (direct + diffuse + reflected) in case of the inclined surface. 10. According to the Fig. 54 b) pyranometer measures diffuse radiation on a horizontal surface and according to the Fig. 54 a) pyranometer measures hemispherical radiation on a vertical surface. Therefore the question are: What for the diffuse solar radiation on horizontal

surface is measured? Where the pyranometer presented in Fig. 54 a) is located?. Solar radiation incident on vertical surface depends strongly on the orientation of the surface and of course solar radiation incident on horizontal surface is different than on a vertical one. Chapter 6 presents results of the long-term in situ measurements made by the candidate. The experiments were conducted for two new wall structures, based on the new methods of integration of the PCM with the thermal insulation proposed by the candidate. It is necessary to underlined to hard work needed to make long term measurements. It is evident that the candidate is analyzing carefully results obtained. Some questions to this chapter are nearly the same as they were in other chapters, because they are consequences of previous presentation of the problem formulated, simulated and validated.. 1. How efficiency of the PCM application is defined by the candidate? (page 122). 2. Page 123 it is written: Temperatures measured in the ventilated cavity were taken for calculations as external temperatures. It was already mentioned, that temperature in the ventilated cavity is higher than the ambient air temperature, because of the photovoltaic effect, which takes place in the PV panel. Because of that the measured temperature in the ventilated cavity cannot be taken as external air temperature. In result something different is tested than it was simulated. Tests are made for BIPVT system with ventilated space between PV panels and external wall. 3. Page 124 it is written: ambient temperature fluctuations determine changes in the internal surface of building partitions. However, it is not really the case of the tested wall. In experimental tests the external wall does not have a contact with the ambient environment, but with the air cavity and the PV panel. In addition when an external layer of the wall is an insulation layer than the impact of the ambient environment is very much reduced and the solar energy impact can be neglected. 4. Page 127 128. The title of the subchapter is: 6.1.2. Verification of external boundary conditions. However, as it was already mentioned the external boundary conditions verified by measurements are not the same as the simulated ones. 5. Page 129 It should be mentioned that the RT8HC does not change the phase in time under consideration (June), it is liquid all the time, what can be seen in Fig. 59. 6. Results described in section 6.2.3 are not presented in a clear way. The results are caused by the very specific conditions in the cavity, and not in a direct way by the solar radiation and ambient air temperature. The author writes: During the first 120 days, the decrement factor rarely exceeds 0.2 (mainly for the reference panel) because of very large daily fluctuations in ambient temperature and the instantaneous effect of intense solar radiation. It must be underlined again, when there is high solar irradiation the temperature in the cavity can be high, even if the ambient air temperature is low. Tested conditions of the wall with the PCM are not really the same as they were simulated, so the results of measurements can be caused by different phenomena than the candidate pointed out. Further studies are needed. Chapter 7 presents experimental validation of the proposed theoretical model. The candidate describes the validation of the theoretical model of latent heat storage in the experimental façade set-up. She presents the compatibility of simulation results with measurements. Numerical analysis was performed for climatic data collected at the site of the experiment. Some questions to this chapter are nearly the same as they were in other chapters. 1. How the diffuse solar radiation on the inclined (vertical) surface was calculated? 2. What does it mean: direct normal solar radiation how it was calculated? 3. How the solar radiation impact on the external wall surface is reduced by the PV panel operation? How it is calculated?

4. How ventilation of the cavity is described in a mathematical model? 5. Figure 70b direct solar radiation cannot be so high. 6. Page 148 and Figure 71, it is written: Based on the results presented in Figure 71 it can be observed that changes in temperature and diffuse solar radiation can be approximated with hourly data with good precision. What does it mean? 7. Page 148 It is written: Moreover, it can be noted that wind parameters such as its speed and direction are very dynamic and poorly reflected by the hourly values. What does it mean? And it must be underlined, that there is no wind in the cavity. The candidate does not consider the external PV panel surface, which is under direct influence of the wind. The candidate analyses the external surface of the wall in the air cavity of the building envelope. So there is no influence of wind there, but there is a ventilated air flow. 8. Page 150 - Table 14. Why the correlation coefficients calculated for weather parameters (indicated in Table 14) are assumed to be constant? They should be calculated for every hour of a day, if a dynamic model is considered. 9. Page 153. It is written: It can be concluded that the major reason of such discrepancy between the results result from the instantaneous influence of solar radiation, which is a very dynamic weather parameter. How this statement can be explained, if we know (it is evident) that there is no direct influence of solar radiation on the external wall surface in the cavity? The problem is much more complex. Chapter 8 presents conclusions of the developed research studies. It is good comprehensive summary of the work that was done and contribution to knowledge of this thesis (presented in highlights). However, it is pity that no recommendations for the future studies and research have been formulated, because it is really a lot to be done in the scope of the problem undertaken in the thesis. For further research it would be good to take into account that construction of the façade being under measurements belongs to very innovative technology of BIPVT systems. The phenomena in the ventilated air cavity are much more complicated and complex than it is presented. It is necessary to underline again that the results of the experiments performed by the candidate can be very useful for improvement of the insulated energy upgraded envelope of the building representing an innovative BIPVT system. 3. Final recommendation At the end of my report I should state that the thesis shows evidence of rigour and discrimination and hard work that has been done by the candidate. Appreciation of the relationship of the subject undertaken by the candidate to a wider field of knowledge is evident. In many parts thesis show the novel character of research developed. The designed, constructed, experimentally tested, mathematically modeled, numerically simulated and then validated structure of external insulated wall enhanced by the PCM is a substantial novel research achievement of the candidate with an original contribution to knowledge in the scope of technical science. Summarizing I can state that the thesis Dynamics of thermal insulation modified by phase change material submitted by MSc. Eng. Anna Wieprzkiewicz fulfill the requirements of the Law on Scientific degrees and scientific titles, and degrees and titles in Art, dated on the 14 March 2003 with later amendments (Ustawy z 14 marca 2003 r. o Stopniach naukowych i tytule naukowym oraz o stopniach i tytule w zakresie sztuki (z późniejszymi zmianami, Dz. U. z 2017 r. poz. 1789) and has been elaborated in accordance with the art.13 ust.1 of the Law. I therefore propose to accept the thesis and I am asking for Anna's Wieprzkiewicz admission to the public defense of her doctorate.