Title:
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Solar thermal storage using phase change material for space heating in residential buildings
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In 2007 the domestic sector was responsible for 27% of all energy consumed by
final users in the UK, yet only 1.5% of this energy was met by renewables. The
utilisation of renewable energy systems such as active solar water heating with
Phase Change Material (PCM) thermal storage, offers vast potential for reducing
energy use and CO2 emissions in the domestic energy sector in the UK.
Previous research indicated that the incorporation of PCMs in underfloor heating
had the potential to make energy savings, but their use in combination with
renewable energy had not been explored in the UK. Consequently this was
identified as a gap in the current knowledge that the current research would fill. A
shortage was also identified in real life performance data on PCM space heating
system performance in the UK. The current work successfully addresses this
shortfall in data and in doing so provides a significant contribution to knowledge in
the area of using solar thermal storage for space heating of residential buildings.
An in depth literature review was undertaken as part of the research programme,
which identified the key shortcomings in existing PCM based thermal storage
systems for space heating. An underfloor space heating system for residential
buildings was therefore developed that addresses the weaknesses of the existing
systems highlighted in the literature review. The system stores solar thermal
energy during the day and then uses this to provide space heating in the evening,
thus addressing the problem of matching solar availability to demand.
An experimental approach was adopted for the study as numerous researchers
(Kauranen et al., 1991, Hasnian, 1998, Kenisarin and Mahkamov, 2007), have
demonstrated the unreliability of manufacturer's published thermophysical
properties of PCM. Therefore, this research chose to adopt an experimental
model approach instead of a mathematical modelling approach.
A model consisting of a full size solar collector 4m2 in area and a PCM filled
underfloor heating panel was constructed in the laboratory. A methodology was
developed to measure the performance of the key modules which allowed the
performance of the system to be evaluated.
The experimental data indicated that it was possible to use a low flow rate of
2.52 litres per minute, without a detrimental effect on the performance of the PCM
panel. The use of a low flow rate minimises parasitic losses and produces
significant energy savings in comparison to the use of higher flow rates. The
experimental results indicated that the system was able to provide adequate
thermal comfort with a maximum floor heat emission of 158 W/m using a flow rate
temperature of 50°C.
Comparisons of the annual space heating energy of the developed integrated
system versus a wet central heating system in the UK revealed a significant
reduction of energy use and associated CO2 emissions by as much as 52%.
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