Experimental study of an innovative glazed solar air collector tested in real conditions

Nowadays, the building sector has a great impact on the CO2 emissions worldwide being responsible for more than a third of energy consumptions. In order to reduce their impact on the environment it is mandatory to implement renewable energy sources (RES) to produce the so called “green energy”. One of the main disadvantages of the systems using RES is the discontinuity in operation and one of the most used RES is the solar radiation which is implemented worldwide and has a great potential to be successfully used. Among the solar systems, solar air collectors (SAC) are systems easy to implement and with low operating costs. For enhancing the overall efficiency of a SAC and to increase the number of hours of operation it is imperative to use thermal energy storage materials (TES). The aim of this paper is to experimentally analyse the implementation of latent heat storage materials (phase changing materials – PCM) in glazed solar air collectors and for this purpose two similar collectors were studied in real conditions. After several experimental analysis conducted we have observed that during the night the PCM slowly releases the energy embodied during the daytime and the rise in temperature is higher in 57% of the time in this case. Moreover the amplitude of outlet temperature variation is lower with 34% in case of using PCMs

Preliminary numerical studies conducted for the numerical model of a real transpired solar collector with integrated phase changing materials

Solar energy has a great potential to reduce the worldwide energy consumptions thus mitigating the impact of building systems on the global warming. Transpired solar collectors (TSC) are cost-effective solutions and phase changing materials (PCM) implemented within them could store the energy during the periods when solar radiation is available. The current paper is part of comprehensive numerical studies and analyses the mesh independency studies conducted in ANSYS Fluent with SST k-Ω viscous model and the numerical model preliminary results (3.3ºC rise in temperature). The results emphasise that the 5 million cells mesh is the feasible option for the studied case

Mesh independency study for an elementary perforated panel part of an air solar collector

In order to achieve the numerical model of a transpired solar collector (TSC) with integrated phase changing materials (PCM) it is mandatory to study the impact of the orifice geometry on the entire system. The numerical simulation of the entire solar collector absorber metal plate (1000x2000mm and 5000 orifices) is not feasible thus resulting a huge number of cells for the numerical grid for which we will need very high computational resources and a very large amount of time to be solved. By taking these aspects into account we decided to simulate only four equivalent orifices and then to transpose the results to the actual case for further studies. The present paper aims to analyse the mesh independency study for an elementary perforated panel with four equivalent lobed orifices which is part of a real case TSC. This analysis represents one of the most important stages within the construction of the TSC numerical model and doesn't need an experimental validation. The study was conducted in Ansys Fluent CFD software and the results were processed directly by using Tecplot software. Six different meshes were analysed (from 0.2 to 7.3 million cells), boundary conditions were imposed, and k-ε RNG turbulence model was used according to the literature. After comparing velocity and temperature fields in longitudinal and transverse planes we concluded that from 5.3 million cells the solution is independent of the meshing quality

Air solar collectors in building use - A review

In the current energy and environmental context it is imperative to implement systems based on renewable energy sources in order to reduce energy consumptions worldwide. Solar collectors are studied by many years and many researchers are focusing their attention in order to increase their efficiency and cost-effectiveness. Water solar collectors are often implemented for domestic hot water, heating or industrial processes and already have a place on the market. A promising system which is not yet widely known is represented by air solar collectors that could represent an efficient way to use the solar energy with a lower investment cost, a system that can be used in order to preheat the fresh air required for heating, drying, or to maintain a minimum temperature during winter. This paper presents a comprehensive literature review on air solar collectors used mainly in buildings, acting as a solar wall. Air solar collectors are roughly classified into two types: glazed and opaque. The present study comprises the solar collector classification, applications and their main parameters with a special focus on opaque solar collectors

Air solar collectors in building use - A review

In the current energy and environmental context it is imperative to implement systems based on renewable energy sources in order to reduce energy consumptions worldwide. Solar collectors are studied by many years and many researchers are focusing their attention in order to increase their efficiency and cost-effectiveness. Water solar collectors are often implemented for domestic hot water, heating or industrial processes and already have a place on the market. A promising system which is not yet widely known is represented by air solar collectors that could represent an efficient way to use the solar energy with a lower investment cost, a system that can be used in order to preheat the fresh air required for heating, drying, or to maintain a minimum temperature during winter. This paper presents a comprehensive literature review on air solar collectors used mainly in buildings, acting as a solar wall. Air solar collectors are roughly classified into two types: glazed and opaque. The present study comprises the solar collector classification, applications and their main parameters with a special focus on opaque solar collectors

Experimental study of an innovative glazed solar air collector tested in real conditions

Nowadays, the building sector has a great impact on the CO2 emissions worldwide being responsible for more than a third of energy consumptions. In order to reduce their impact on the environment it is mandatory to implement renewable energy sources (RES) to produce the so called “green energy”. One of the main disadvantages of the systems using RES is the discontinuity in operation and one of the most used RES is the solar radiation which is implemented worldwide and has a great potential to be successfully used. Among the solar systems, solar air collectors (SAC) are systems easy to implement and with low operating costs. For enhancing the overall efficiency of a SAC and to increase the number of hours of operation it is imperative to use thermal energy storage materials (TES). The aim of this paper is to experimentally analyse the implementation of latent heat storage materials (phase changing materials – PCM) in glazed solar air collectors and for this purpose two similar collectors were studied in real conditions. After several experimental analysis conducted we have observed that during the night the PCM slowly releases the energy embodied during the daytime and the rise in temperature is higher in 57% of the time in this case. Moreover the amplitude of outlet temperature variation is lower with 34% in case of using PCMs

Impact evaluation of EUR-ACE programme accreditation at Jyväskylä University of Applied Sciences (Finland)

The article reports on a case study of impact evaluation of external quality assurance, i.e. EUR-ACE programme accreditation, which was carried out by the Finnish Education Evaluation Centre at Jyväskylä University of Applied Sciences in the form of a methodological before-after comparison. The results show mainly positive and stable attitudes of teachers and students towards quality assurance during the accreditation process and indicate that the university has managed to find a balanced expenditure/benefit ratio with respect to its quality assurance procedures. Another finding is that the involvement of the students in quality assurance as well as to make quality assurance work more relevant for them seems to be one challenge. Particularly, the difference in awareness of the development of the programme between average students and student representatives seems to be substantial. In addition, the data suggests that individual teachers could be more involved in quality assurance

Numerical model of a solar ventilated facade element: experimental validation, final parameters and results

The present paper analyses the airflow through the lobed orifices of a transpired solar collector which acts as a solar ventilated facade element through numerical simulation. This study is part of a complex research project which analyses the implementation of phase changing materials within air solar collectors. We decided to study an elementary part of the collectors' absorbent plate with four equivalent orifices in order to obtain the velocity and temperature field at the outlet of the computing domain since the numerical simulation of the entire solar collector (more than 5000 orifices) is not feasible due to the big amount of computational resources and time needed. This paper presents the experimental validation of the numerical model, its final parameters and preliminary results. The numerical simulation was conducted using Ansys Fluent CFD software and the results were processed via Tecplot. The boundary conditions imposed were emphasised and k-ε RNG turbulence model was used according to the literature. After comparing the velocity profiles and temperature fields obtained with both experimental and numerical approaches we concluded that the numerical model reproduces real flow phenomena within acceptable limits. The numerical model thus obtained will be used in further studies in order to optimise the collectors' geometry and characteristics by means of parametrical analyses