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Evaluation of seasonal storage for passive houses in Ireland
Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
2010 (English)Independent thesis Advanced level (degree of Master (Two Years))Student thesis
Abstract [en]

To be able cover most of the heating demand in buildings in northern Europe with solar energy it is necessary to store energy from summer to winter. Scandinavian Homes is an Irish construction company that has come up with an idea of a solar seasonal storage system for one of their passive houses. The system basically consists of 6 vacuum tube collectors (absorber area 10.8 m2), one large underground store with a low height-to-diameter ratio and one smaller DHW (domestic hot water) store placed inside the house. In the seasonal store there are three coils: one for the solar circuit, of for pre-heating the DHW and one for a floor heating circuit. The collectors will primarily heat the DWH store and secondly the seasonal store. The main aim of this study is to evaluate the system described above. The aims are also to examine the influence of different parameters on the system performance and to suggest an alternative design of a seasonal storage system and to compare this to Scandinavian Homes’ system. The performance of Scandinavian Homes’ system was examined using the simulation program Polysun 4.4. Parametric studies of the collector area, the flow rate in the collector circuit and the tank height were performed and the effects of lowering the settings of the thermostats in the system were examined. After a literature study focusing on solar seasonal storage systems for single family houses, two alternative system designs were chosen. The first system included one large tank used for both DWH and space heating and an external heat exchanger for the solar loop. The second system included one large tank with an internal tank for DHW heating. In this case two internal heat exchangers for the solar loop were used. The seasonal stores in these systems both had a high height-to-diameter ratio. The systems were simulated in Polysun with the same boundary conditions as Scandinavian Homes’ system. In order to compare the three systems to each other, the key figure fractional extended energy savings was used. The results were also compared to a simple solar DWH system with an array of 3 collectors. The results from the simulations of Scandinavian Homes’ system showed that variations in flow rate and tank height had little impact on the system performance. The total need of primary auxiliary energy was however decreased by 13% when the temperature required at tap was lowered from 55 to 50°C. When comparing the systems to each other it was found that the solar fractions for Scandinavian Homes’ system and the second alternative system were very similar. Six collectors (10.8 m2) resulted in fractional savings of nearly 60% and 20 collectors (36 m2) gave fractional savings of about 85%. The fractional savings never exceeded 90%, even though the collector area was increased to 70 m2. The simulation results of the first alternative system showed that it failed in delivering the requested DHW temperature at tap. This system could therefore not be compared to the other two. According to the simulations results achieved in this study Scandinavian Homes’ solar seasonal storage system works well in comparison to other seasonal storage system designs. A much larger collector array than the one originally intended by Scandinavian Homes’ would however be needed to cover most of the heating demand in their passive houses with solar energy. The solar fractional savings of the simulated DWH system consisting of 3 collectors turned out to be similar to the savings achieved when a seasonal storage system with 3 collectors was used.

Place, publisher, year, edition, pages
Borlänge, 2010. , 65 p.
Identifiers
URN: urn:nbn:se:du-4621OAI: oai:dalea.du.se:4621DiVA: diva2:518812
Uppsok
Technology
Supervisors
Available from: 2010-04-01 Created: 2010-04-01 Last updated: 2012-04-24Bibliographically approved

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Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • chicago-author-date
  • chicago-note-bibliography
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf