Use of phase change materials (PCM) for the improvement of energy storage in solar water heating systems
Date Issued
May 2012
Abstract
In this paper the use of Phase Change Materials (PCM) in solar storage tanks is considered in an
attempt to improve the solar system operation without changing the production line of solar water
heater manufacturers. Hot water storage tank is one of the main components of any solar water heating
system. It is important to increase the storage capacity and to keep the stratification in these systems,
as this affects the effectiveness of the solar system operation. In general, PCMs present high latent
heat of evaporation and they offer more storage capacity than water. The experimental investigations
of the operation of the storage tank were carried out both during heating up and draw off. In all
experiments carried at different initial storage temperatures, number of PCM canisters (1-3) and drawoff
rates (1, 3 and 6 l/min), the tanks with PCM show superior performance than the same tank
operating in similar conditions without PCM. For the 50 l tank used, two PCM canisters showed the
best performance and a draw off profile up to 3 l/min. The flow of 6 l/min seems to be excessive for
small storage volume as the high flow rate does not allow the PCM to give its heat to the flowing
water. Another experiment performed is the intermitted withdrawal of water from the storage tank so
as to simulate the actual use. The results were also positive. Therefore, from this work it is concluded
that the use of PCM gives improved storage capacity of the system and improved system behavior
during draw-off.
attempt to improve the solar system operation without changing the production line of solar water
heater manufacturers. Hot water storage tank is one of the main components of any solar water heating
system. It is important to increase the storage capacity and to keep the stratification in these systems,
as this affects the effectiveness of the solar system operation. In general, PCMs present high latent
heat of evaporation and they offer more storage capacity than water. The experimental investigations
of the operation of the storage tank were carried out both during heating up and draw off. In all
experiments carried at different initial storage temperatures, number of PCM canisters (1-3) and drawoff
rates (1, 3 and 6 l/min), the tanks with PCM show superior performance than the same tank
operating in similar conditions without PCM. For the 50 l tank used, two PCM canisters showed the
best performance and a draw off profile up to 3 l/min. The flow of 6 l/min seems to be excessive for
small storage volume as the high flow rate does not allow the PCM to give its heat to the flowing
water. Another experiment performed is the intermitted withdrawal of water from the storage tank so
as to simulate the actual use. The results were also positive. Therefore, from this work it is concluded
that the use of PCM gives improved storage capacity of the system and improved system behavior
during draw-off.
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