Ideas 2 (USE OF PHASE CHANGE MATERIALS IN SOLAR PANELS (They absorb or…
USE OF PHASE CHANGE MATERIALS IN SOLAR PANELS
PCM Materials that were mostly investigated were paraffins and fatty acids. Paraffins were mostly used as a PCM material because they have a high latent heat of fusion which gives them high heat capacities (Fortuniak et al. 2013).
Ideal PCM for cooling PV panel must have large latent heat of fusion, high thermal conductivity, be chemically stable, non-corrosive, non-toxic, melt, temperature lying in the operating temperature of the PV panel and minimum sub cooling.
For a material to be classify as a PCM material, it needs to be in a small volume changes on phase transformation and small vapor pressure at operating temperatures to reduce the containment problem, high specific heat, high density, high thermal conductivity and melting temperature must in the desired operating temperature range (Rastogi et al. 2015).
The significant impact of lowering surface temperature is shown during PCM cooling, where maximum temperature was only at 60.4oC. As a comparison, PV panel without PCM recorded that during 09:00 am to 02:00 pm, the temperature rose up to 28oC, while PV panels with PCM only 11oC. Beeswax has a better ability to absorb heat compared to the paraffin wax
Thaib et al 2018
When the temperature is lower, the SP/PCM had a higher temperature compared to an unmodified solar panel, as the PCM’s absorbed heat was released at the low temperature (Cellura et al. 2014)
It has three types: organic, inorganic and eutectics. Organic PCM differs in inorganic PCM as it is non-corrosive but not suitable in plastic containers.
Socaciu et al. 2014
When PCM material melts(solid-liquid phase), it absorbs a large amount of heat from the environment. When a PCM freezes (liquid-solid phase), it releases a large amount of energy in the form of latent heat at a relatively constant temperature.
A PCM is a substance which can store and release large amounts of energy, typically in the form of heat
Biwole et al. 2011
Biwole et al. 2011 observed that an attached PCM maintained the panel’s temperature below 40 degrees Celsius after 80 minutes of exposure to radiation, which was reached after five minutes by the panel without PCM
A research done by Cellura et al. 2008 showed that the peak temperature of a SP/PCM was lower than a solar panel, at around 66° Celsius and 83° Celsius, respectively, displaying its ability to lower the temperature of the panel by absorbing its heat energy as it melts
They absorb or reject heat in the process. Compared to other methods of temperature regulation, the use of PCM has the added advantage of storing heat energy that can be used asynchronously (Browne et al. 2015).
Organic phase change materials become the research focus because in its phase change
process the parvafacise phenomenon is hard to happen, and it is easy to be overcooled
Wang et al. 2011
PCM with a melting point of between 28° Celsius and 32° Celsius would be the most efficient in maintaining the temperature on a summer, which is on average, around 29° Celsius.
Thaib et al 2018 developed a SP/PCM system using beeswax and paraffin wax as PCM to SP/PCM systems installed outdoors. They concluded that, when compared to paraffin wax, beeswax was better at lowering the temperature of the panel.
The process of the phase change of a binary mixture takes place over a temperature range and the temperature range depends on both the heating rate and the mixture composition (Kousksou et al. 2010)
A PCM with an easily adjustable melting point would be a necessity as the melting point is the most important criterion for selecting a PCM for passive solar applications (Farid et al. 2004).
The efficiency of PCM is dependent on the encapsulated quantity and energy storage capacity per unit mass during its melting and solidifying. (Chemil 2006)
The melting time depends on the rate of natural convection which in turn depends on the Rayleigh number. The higher the value of the Rayleigh number, the higher the rate of natural convection, the lesser the time of melting (Soma and Topas 1993).
The law of thermodynamics tells that with increased heat comes decreased power output, and this applies Ito solar panels. Thus, warmer temperatures will always means less output for PV cells (Dincer and Rosen 2007)
Melting of PCM occurs during the day when the indoor temperature increases above the comfort range. Hot air of the room passes through the panel and the heat is absorbed by the solid PCM which leads to the beginning of the melting process
*knowledge established by previous research