Thermal management of silicon photovoltaic panels: a review

Photovoltaic (PV) technologies represent a key role in the ongoing energy transition towards the decarbonisation of convectional power systems and to reduce the harmful population impact to environment. Nowadays, the majority of market available photovoltaic PV technologies are silicon based with a usual energy conversion efficiency of less than 20 %. The major drawbacks of the widely used silicon PV technologies are related to performance degradation due to aging as well as performance drops that occur during periods of elevated operating temperatures. In order to improve performance, as well as the lifetime of the PV systems, various cooling techniques have been investigated in the last two decades. The main goal of the specific cooling approaches for PV panels is to ensure efficient thermal management, as well as economic suitability. In this review paper, different cooling strategies are categorized, discussed and thoroughly elaborated in order to provide deep insight related to an expected performance improvement and economic viability. The main results of this review indicate that the cooling approaches for PVs can ensure a performance improvement ranging from about 3 up to 30 %, depending if passive or active cooling approaches are applied. The main results also indicate that the economic viability as well as environmental suitability of the specific cooling approaches is not sufficiently discussed in the existing research literature

Atmosferski gravitacijski vrtložni stup kao protočni objekt: poboljšanje troslojnog modela

An improved physical and analytical three-layer model of gravitational vortex columns (GVCs) for solar chimney power plants is developed in this paper. In essence, this model represents a further improvement and upgrade of the three-layer model proposed in Ninić et al. (2009). The improvements of the three-layer model deal with internal friction, variable vertical velocity (by height) in the central GVC spiraling upward flow, and variable angular momentum of the downdraft shell. A numerical solution of the improved model is given as a characteristic case and is compared to the elementary GVC model. The results show that the introduced improvements are important parameters for further analysis of gravitational vortex columns.U ovom radu razvijen je poboljšani troslojni analitički model gravitacijskog vrtložnog stupa (GVS) za solarne termoelektrane. U suštini, razvijeni model predstavlja daljnje poboljšanje troslojnog modela predloženog u Ninić i ostali (2009). Uvedena poboljšanja u troslojni model odnose se na uvođenje utjecaja rada unutarnjeg trenja, promjenjive vertikalne brzine (s visinom) u centralnom dijelu GVS-a te na utjecaj promjenjivog momenta količine gibanja u spusnoj ljusci. Prikazano je karakteristično numeričko rješenje poboljšanoga modela i uspoređeno je s rješenjem dobivenim osnovnim modelom. Numerički rezultati pokazuju da uvedena poboljšanja predstavljaju važne parametre za daljnju analizu gravitacijskih vrtložnih stupova

Osnovna unapređenja solarne dimnjačne elektrane

This paper deals with the numerical analysis procedure and results of flow simulation through solar chimney. Because of relatively low Reynolds numbers, some aerodynamic improvements could be obtained. The paper links input heat energy with geometry or air flow parameters. Basic solar chimney geometry is carried out and analyzed with CFD application in three dimensional domain. The main assumption is to reach the optimal fractional pressure drop across turbines and maximal electric energy production by solar chimney geometry adaptation. Results are numerically tested by known parameters and improvements are applied and tested. Various shapes of internal solar chimney geometry are applied and the best for given input parameters are extracted. Also, some external geometry shape solutions are investigated. Test includes comparison with the known measured air flow results in similar solar chimney (Manzanares, Spain). Results provided validate the assumptions and could be a base for further experimental investigations.U radu se opisuju numerički postupci i rezultati simulacije strujanja kroz solarnu dimnjačnu elektranu. Zbog relativno malih Reynoldsovih brojeva moguće je izvesti određena aerodinamička unapređenja. Rad povezuje vanjsku dovedenu toplinu s parametrima unutarnjeg strujanja. Osnovna geometrija solarnog dimnjaka izvedena je i analizirana pomoću CFD aplikacije u trodimenzijskoj domeni. Osnovna pretpostavka rada je povećanje efikasnosti postizanjem optimalnog pada tlaka kroz turbinu i najveće produkcije električne energije promjenom geometrije. Rezultati su numerički testirani i uspoređeni s poznatim parametrima uz primjenjena unapređenja. Izdvojeno je i analizirano više geometrijskih oblika unutrašnjosti solarnog dimnjaka. Isto tako mijenjani su i neki vanjski oblici. Testiranje dobivenog obavljeno je usporedbom s poznatim mjerenim vrijednostima sličnog izvedenog postrojenja (Manzanares, Španjolska). Usporedbe ukazuju na ostvarenje predviđenog poboljšanja efikasnosti i mogu biti baza za daljni eksperimentalni rad

Termodinamički aspekt definicija »CAPE« i »TCAPE«

The paper analyses the thermodynamical aspect of the terms CAPE and TCAPE, defined in the standard way according to Brunt (1941) and in another way in Renno and Ingersol’s paper (1996). Based on this, in this paper it is pointed out that the thermodynamical foundations for the difference existing between the two definitions. The analyses itself is based on the presentation of all the relevant terms in thermodynamics diagrams and relations for in­ter­nal-equilibrium processes and processes with internal friction. The paper shows the internal friction which Renno and Ingersol take into consideration and make their definition of CAPE and TCAPE different from the standard one and not equivalent to it. In this connection, only ac­cording to the standard definition CAPE and TCAPE represent the maxi­mum work which is real in advance calculable measure of convective circulation intensity.U radu se analizira termodinamički aspekt pojmova CAPE i TCAPE, definiranih na standardni način i na način u radu Rennoa i Ingersola (1996). Svi procesi koji su po- služili za definiranje tih pojmova ilustriraju se u termodinamičkim dijagramima i opi- suju se točnim termodinamičkim relacijama. U prvom slučaju oni su po definiciji potpu- no ravnotežni tj. reverzibilni. Nadalje, u radu se pokazuje da unutarnje trenje, koje Renno i Ingersol uzimaju u obzir, čini njihovu definiciju CAPE i TCAPE različitom od standardne. Naime, CAPE i TCAPE po njihovoj definiciji predstavljaju rad disipacije pri konvekciji, a ne njen radni potencijal

Photovoltaic Panels: A Review of the Cooling Techniques

In this paper, current advances in cooling techniques and temperature control of photovoltaic (PV) panels in general, are analyzed and discussed. Namely, it is well known that a decrease in the panel temperature will lead to an increase in electrical efficiency, so in recent years different cooling techniques have been proposed and tested experimentally. The efficiency drops with the rise in temperature, with a magnitude of approximately 0.5 %/°C. Several cooling techniques have been tried, mostly based on active water and air cooling, as these are the simplest techniques. Other cooling techniques include conductive cooling, phase-change material cooling, etc. Increase in electrical efficiency depends on cooling techniques, type and size of the module, geographical position and the season of the year, and usually corresponds with a rise of 3-5 % in overall efficiency. Finally, a perspective on the other cooling techniques for PV panels will be also elaborated on and discussed in this paper

An assessment study of evaporation rate models on a water basin with floating photovoltaic plants

Under the general topic of the impact of floating PV systems (FPVs) on water basins, the present study aims to model and analyze the effect of FPVs on the evaporation rate of water surfaces. The estimation of the evaporation of the water surface of a basin is usually calculated using mathematical evaporation models that require knowledge of some parameters (i.e. solar radiation, humidity, air temperature, water temperature, wind velocity). Thus, in the first section of this study some evaporative models (EVM) for free water basin have been examined to evaluate which are the environmental variables used. On the basis of this analysis, new numerical models for the calculation of the daily evaporation rate have been developed using the DoE method (3 models) and the linear regression method (2 models). The results of the developed models have been compared with the experimental measurements carried out by an evaporimeter, such comparison has highlighted the robustness of the proposed numerical models. Moreover, for estimating the evaporation rate in water basins partially covered by FPVs further three numerical methods are proposed. Finally, the evaporation rates, arising by the installation of different typology of FPVs on water basins, have been evaluated as function of the energy balance on the water surface. It is possible to highlight that the amount of evaporated water depends not only on the percentage of surface covered but also on the characteristics of floating systems. Covering only 30% of the surface of a basin, it is possible to obtain up to 49% reduction in evaporation

Influence of Electrical Yield on Temperature Drop of the PhotovoltaicPanel: Numerical and Experimental Findings

This manuscript deals in confirmation of drop in photovoltaic panel temperature under load. Two panels are compared, one with the load and other without the load. The panel under load should have larger heat dissipation (i.e. be cooler), when electrical yield is taken as an outgoing heat flow. During the experiment, a thermovision of the panels under solar irradiance was made with the thermal camera. Results of the first case show only minor change in panel temperature. Results of the second case, where one panel is under load, show reduced temperature of loaded panel, by up to 4 °C. Previously developed numerical model is updated with the measured data in the experiment. A measured electrical yield is taken into the account when the solar irradiance was modelled. Numerical model confirms the temperature drop and corresponds with infrared thermography data. Gained results can help in design of the photovoltaic systems, where more variants of operating conditions can be used in order to keep the panel on desired operating temperature

Termodinamički aspekt definicija »CAPE« i »TCAPE«

The paper analyses the thermodynamical aspect of the terms CAPE and TCAPE, defined in the standard way according to Brunt (1941) and in another way in Renno and Ingersol’s paper (1996). Based on this, in this paper it is pointed out that the thermodynamical foundations for the difference existing between the two definitions. The analyses itself is based on the presentation of all the relevant terms in thermodynamics diagrams and relations for in­ter­nal-equilibrium processes and processes with internal friction. The paper shows the internal friction which Renno and Ingersol take into consideration and make their definition of CAPE and TCAPE different from the standard one and not equivalent to it. In this connection, only ac­cording to the standard definition CAPE and TCAPE represent the maxi­mum work which is real in advance calculable measure of convective circulation intensity.U radu se analizira termodinamički aspekt pojmova CAPE i TCAPE, definiranih na standardni način i na način u radu Rennoa i Ingersola (1996). Svi procesi koji su po- služili za definiranje tih pojmova ilustriraju se u termodinamičkim dijagramima i opi- suju se točnim termodinamičkim relacijama. U prvom slučaju oni su po definiciji potpu- no ravnotežni tj. reverzibilni. Nadalje, u radu se pokazuje da unutarnje trenje, koje Renno i Ingersol uzimaju u obzir, čini njihovu definiciju CAPE i TCAPE različitom od standardne. Naime, CAPE i TCAPE po njihovoj definiciji predstavljaju rad disipacije pri konvekciji, a ne njen radni potencijal

Photovoltaic Panels: A Review of the Cooling Techniques

In this paper, current advances in cooling techniques and temperature control of photovoltaic (PV) panels in general, are analyzed and discussed. Namely, it is well known that a decrease in the panel temperature will lead to an increase in electrical efficiency, so in recent years different cooling techniques have been proposed and tested experimentally. The efficiency drops with the rise in temperature, with a magnitude of approximately 0.5 %/°C. Several cooling techniques have been tried, mostly based on active water and air cooling, as these are the simplest techniques. Other cooling techniques include conductive cooling, phase-change material cooling, etc. Increase in electrical efficiency depends on cooling techniques, type and size of the module, geographical position and the season of the year, and usually corresponds with a rise of 3-5 % in overall efficiency. Finally, a perspective on the other cooling techniques for PV panels will be also elaborated on and discussed in this paper

THE USE OF THE WEARABLE SENSORY DEVICES FOR METABOLIC RATE ESTIMATION

The human metabolic rate has been widely noted as the least accurately assessed parameter in the research of thermal comfort. Since it is difficult to measure, it is often reduced on simple diary methods which do not take into account the influence of age, gender, and daily dynamics of a building occupant. In this study wearable sensory device were used to track user activities inside the building to estimate the metabolic rate. Eight participants were chosen for the 7-days monitoring, four times during the year. The study aimed to examine whether the user age, gender, and season of the year influence the change in user metabolic rate to improve the thermal environment of the HVAC system building. The results showed the difference between groups of building occupants that could serve as a reference to assess personal thermal comfort in future research