International News
RESEARCH ON THERMAL
STORAGE UNITS AND CANDLE WAX
In future , paraffin wax could help to make underground thermal storage units more durable . Such systems are used , for example , to store solar energy over a longer period of time . In a new study , geologists from Martin Luther University Halle-Wittenberg ( MLU ), investigated the extent to which paraffin wax can be incorporated into the shell of the storage tanks and whether this can prevent heat loss and close fissures . The research team reports on its findings in the journal " Plos One ".
A major challenge for renewable energies is finding a way to store them in the medium term . Simple , cost-effective solutions are needed , so that for example , solar energy that is produced in the summer can be used in winter .
To do this , water is often heated using solar thermal energy systems and then stored in large underground basins . Ideally , the stored thermal energy lasts into the winter . The basins are lined with a foil to insulate them and prevent water loss . " When you look at the projects implemented so far , you see the same weaknesses again and again ," says Professor Peter Bayer from the Institute of Geosciences and Geography at MLU . Water and , hence the heat often escapes through the areas that are damaged .
Bayer has brought his research on seasonal thermal storage systems with him to Halle from the Institute of New Energy Systems at the Ingolstadt University of Applied Sciences . As part of a project sponsored by the Volkswagen Foundation , his team investigated whether these shortcomings could be offset by an additional component in the outer shell of the thermal storage unit : paraffin wax .
Better known as candle wax , it is already being used as a latent heat storage material . Paraffin wax melts at relatively low temperatures , absorbing heat , which is re-released on solidification . It is also highly hydrophobic , which means that it repels water . " The idea was to take advantage of both of these material properties ," explains Bayer . When integrated into the outer shell of a thermal storage unit , paraffin wax could help reduce heat loss . At the same time , it could bring about a self-healing effect . " When a crack develops in the shell , the wax liquefies and closes this gap ."
Paraffin wax is also environmentally friendly . If it were to leak out of the storage basin , there would be no toxic impact . And , according to Bayer , it is more cost-effective than other latent heat storage materials . In two laboratory experiments , his colleague Christoph Bott tested the extent to which paraffin wax reduced heat loss and whether the outer paraffin wax shell would really heal itself . " At first glance , the mechanisms we expected worked very well ," says Bott . When the outer shell was damaged , the liquefied wax filled in the damaged spot .
There was also an improvement in the heat storage capacity . " However , it is difficult to upscale this to an industrial level ," says Bayer . The larger the basin , the more the paraffin wax in the outer shell is displaced by the weight of the water . Additional structures would be needed to keep it in place . And if the shell were to incur major damage , the self-healing effect would no longer work . " At high pressure , the water just ignores the paraffin wax ," says Bayer . It just flows right past it .
But Bayer is convinced that even if the idea cannot be immediately put into practice , it still has potential . " Right from the start we knew that it would be difficult to implement ," he remarks . " We were using paraffin wax for the first time in an entirely new setting ." However , the research is a further step towards improving seasonal storage and thus creating more efficient storage capabilities for renewable energies . The project was funded by the Volkswagen Foundation as part of its ‘ Experiment !’ programme , which backs innovative but risky projects . RACA
Paraffin wax , or commonly know as candle wax is environmentallyfriendly and further has no toxic properties .
Creative Commons www . hvacronline . co . za RACA Journal I January 2021
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