Potential for Mitigation of Solar Collector Overheating Through Application of Phase Change Materials – A Review

Demand for domestic hot water and heating is rarely perfectly concurrent with solar irradiation, which means that collectors can overheat in periods of high incident radiation and low demand. Phase change materials have been used as energy storage in space heating applications to absorbs excess heat during low demand periods for use in peak demand periods. This paper reviews the current state of research on the possibility of application of such materials as energy storage for solar collectors, in order to avoid collector overheating. Finally, various materials were evaluated and ranked for this application based on required properties and price. An example model of such materials being applied in a typical family house domestic hot water solar system is also provided

Solarna dizalica topline

Ovaj rad opisuje proces tehničke konstrukcije i proračuna solarne dizalice topline za pripremu potrošne tople vode (PTV) u akumulacijskom spremniku. U sklopu rada su opisani princip rada i trenutna područja primjene u praksi solarnih dizalica topline. Zatim je napravljen termodinamički proračun lijevokretnog procesa za solarnu dizalicu topline koja može pripremati potrošnu toplu vodu u spremniku od 800 litara. Uz to je napravljen i termodinamički proračun izmjene topline u kondenzatoru, a koji je cijevna spirala unutar akumulacijskog spremnika potrošne tople vode. Usporedno s proračunom procesa solarne dizalice topline napravljen je i odabir potrebnih komponenti. Za navedenu dizalicu topline napravljen je simulacijski model pomoću kojega se može simulirati njen rad u različitim pogonskim uvjetima. Pri tome su za provedene simulacije korišteni podatci za referentnu godinu

Primjena infracrvene termografije u određivanju vodnog stresa povrća

U ovome radu provedeno je istraživanje na uzorcima presadnica industrijske rajčice (Lycopersicon ecvulentum Mill.) i paprike (Capiscum annuum L.). Mjerenja temperature su provedena termoparovima i infracrvenom termografskom kamerom. Na uzorku rajčice su provedena i mjerenja bioloških svojstava biljke poput vodnog potencijala lista (LWP). Analizirana je promjena temperature i indeksa vodnog stresa usjeva (CWSI) tijekom dana. Na osnovu vrijednosti CWSIa dobivenih pomoću više modela analize i mjerenih vrijednosti LWPa napravljeno je više modela koji opisuju vezu tih dviju vrijednosti. Dobiveni modeli su pokazali statistički značajan stupanj korelacije između tih vrijednosti. Vrijednosti CWSIa dobivene ručnom obradom termograma su se dale najveći stupanj korelacije, no i neke automatske metode obrade su pokazale usporedive rezultate s ručnima. Zaključeno je da je uz korištenje metode automatskog termografskog snimanja koja proizvodi termograme dovoljno visoke kvalitete automatska obrada termograma za izračun CWSI pouzdano primjenjiva

Numerical Investigation of Cover Plate Configurations Effect on Thermal Characteristics of a Polymer Solar Collector

This paper presents numerical analysis on influence of different configurations on thermal performances of a polymer solar collector. In the first step two configurations including single cover plate and honeycomb cover plate are investigated. Results showed that collector with single cover plate is more efficient than collector with honeycomb cover plate at lower reduced temperature values. Honeycomb cover plate behaves like insulator, increasing overall collector top resistance to heat loss which results in higher thermal efficiency at higher reduced temperature values. This also leads to higher temperatures at stagnation regimes. Also, in this paper two passive overheating protection based on natural convection are examined. Channels inside honeycomb cover plate can be connected to channels inside absorber plate allowing for air to flow inside collector. Three different channel widths are considered 4.25, 10, and 20 mm. With such passive method, it is possible to reduce average absorber temperature up to ~20°C. Second overheating protection uses additional channel below the absorber plate allowing the flow of ambient air. With this method it is possible to reduce temperatures up to ~50°C but it also causes high temperature gradient, 50°C/m of collector length which can potentially result in deformation of polymer solar collector. Present work is a part of the research focused at development of a low-cost polymer solar collector that operates in a drain back system

Solar assisted heat pump

Ovaj rad opisuje proces tehničke konstrukcije i proračuna solarne dizalice topline za pripremu potrošne tople vode (PTV) u akumulacijskom spremniku. U sklopu rada su opisani princip rada i trenutna područja primjene u praksi solarnih dizalica topline. Zatim je napravljen termodinamički proračun lijevokretnog procesa za solarnu dizalicu topline koja može pripremati potrošnu toplu vodu u spremniku od 800 litara. Uz to je napravljen i termodinamički proračun izmjene topline u kondenzatoru, a koji je cijevna spirala unutar akumulacijskog spremnika potrošne tople vode. Usporedno s proračunom procesa solarne dizalice topline napravljen je i odabir potrebnih komponenti. Za navedenu dizalicu topline napravljen je simulacijski model pomoću kojega se može simulirati njen rad u različitim pogonskim uvjetima. Pri tome su za provedene simulacije korišteni podatci za referentnu godinu.This paper presents the design and analysis of a solar-assisted heat pump with direct expansion for heating of domestic hot water (DHW) in an accumulation tank. Within this paper the basic principles and the current applications of this technology are described. A solar-assited heat pump was then designed, complete with a calculation of its basic thermodynamic process (taking into account the required heating capacity and operating conditions) and a calculation of the heat exchange process in the spiral pipe (within the accumulation tank) which serves as the heat pump's condenser. Alongside the calculations the selection of appropriate parts was made. A simulation model was then developed in order to analyze the operation of such a system in various conditons. The simulation was conducted for a number of chosen dates within a reference year

Solar assisted heat pump

Ovaj rad opisuje proces tehničke konstrukcije i proračuna solarne dizalice topline za pripremu potrošne tople vode (PTV) u akumulacijskom spremniku. U sklopu rada su opisani princip rada i trenutna područja primjene u praksi solarnih dizalica topline. Zatim je napravljen termodinamički proračun lijevokretnog procesa za solarnu dizalicu topline koja može pripremati potrošnu toplu vodu u spremniku od 800 litara. Uz to je napravljen i termodinamički proračun izmjene topline u kondenzatoru, a koji je cijevna spirala unutar akumulacijskog spremnika potrošne tople vode. Usporedno s proračunom procesa solarne dizalice topline napravljen je i odabir potrebnih komponenti. Za navedenu dizalicu topline napravljen je simulacijski model pomoću kojega se može simulirati njen rad u različitim pogonskim uvjetima. Pri tome su za provedene simulacije korišteni podatci za referentnu godinu.This paper presents the design and analysis of a solar-assisted heat pump with direct expansion for heating of domestic hot water (DHW) in an accumulation tank. Within this paper the basic principles and the current applications of this technology are described. A solar-assited heat pump was then designed, complete with a calculation of its basic thermodynamic process (taking into account the required heating capacity and operating conditions) and a calculation of the heat exchange process in the spiral pipe (within the accumulation tank) which serves as the heat pump's condenser. Alongside the calculations the selection of appropriate parts was made. A simulation model was then developed in order to analyze the operation of such a system in various conditons. The simulation was conducted for a number of chosen dates within a reference year