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Concentrating Solar Thermal Systems for Building
IntegrationHelena GajbertDivision of Energy
and Building DesignDept of Construction and
Architecture
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Concentrating Solar Thermal Systems for Building
Integration

• Masters thesis Concentrating PV-thermal systems
  for building integration.
• Building-integration of PV systems saves building
  material and work gives cost reductions
• Cheap, highly reflecting aluminium mirrors
  increase the irradiance on the modules and the
  energy output
• Static systems
• Northern locations
• A Problem with concentrators very high local
  concentration ratios on the absorber high
  temperatures on absorber decreasing the
  electrical properties of the PV-cell
• PVs more sensitive to higher temperature than
  thermal collectors

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Parabolic concentrators
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Solar walls in Sweden
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Original and optimised system design
Objective of this work Optimise n and b for
maximum annual electricity production in
southern Sweden
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Experimental set-up
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Solar simulator
?
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Measurements

• Short-circuit current was measured on PV cells in
  concentrating systems (geometries A and B) and
  for vertically mounted cells of the same size
• The solar altitude angle was varied between 0
  and 70
• Short-circuit current measurements on vertical
  cells and concentrating systems gave the optical
  efficiency

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Short-circuit current measurements
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Optical efficiency
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MINSUN simulations

• MINSUN calculates the annual irradiation on a
  south-facing vertical surface
• Originally developed for thermal collectors
• Optical eff. - irradiation on a module in a
  concentrator with a specified angular dependence,
  f(q)
• Knowing the efficiency of the photovoltaic
  modules, the annual electricity production can be
  calculated

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Simulated designs
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Simulated annual electricity production
148 kWh/m² cell area
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Results

• Annual yield per cell area increases with the
  tilt of the optical axis
• Calculated maximum annual electricity production
  of 148 kWh/m² cell area
• which is obtained for C3.36, ß-15?, and ?45
• Calculated annual production is 70 higher than
  for a vertical module
• With ? is 25, the annual yield is 124 kWh/m²
  cell area, 43 higher than for a vertical
  module

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• Mirrors with higher reflectance can increase
  system performance by almost 10 , but are more
  expensive
• The cost of glazing, insulation and wires should
  be covered by energy savings per glazed area
• Studies of cost-efficiency per glazed area are
  required before final recommendations are made
• The system geometry with n45 would maybe not be
  optional be used for building-integration in
  southern Sweden
• The annual electricity production per (expensive)
  glazed area is rather small
• The reflector would mainly be working during
  summer

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Ph.D. Concentrating Solar Thermal Systems for
Building Integration

• Only Thermal systems
• Different geometries MaReCo - roofs and walls
• Focus more on the building envelope

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My work

• Build up a system for trying different collectors
• Perform measurements of a collector prototype -
  sloping roof
• Optimize geometries for two other models, using
  simulation programs as TRNSYS, PolySun, Minsun
• Analyse how light falls on absorber at different
  incidence angles- ray tracing, measurements
• Build and test collectors. Thermal performance,
  solar fraction
• Study different reflector materials
• Test vacuum tube collectors for integration in
  roofs
• Study possibilities for building integration.
  Heat transfer, moisture, etc.
• Calculate cost efficiency.

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CPC- concentrating parabolic compound
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Stand-alone MaReCo
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Separata MaReCo-solfångare på tak
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Högst instrålning i Sverige vid 55
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Heat load - Solar fraction
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Tilted roof MaReCo - Spring/Fall-MaReCo
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East-west MaReCo
.
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Tak-MaReCo
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Wall MaReCo
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Rörsolfångare som takplåt - optimering
?30, d28 mm Principfigur hos form på takplåt
avsedd som reflektorplåt. Acceptansvinkeln hos
denna plåt är ?30 och den är utformat för ett
absorbatorrör med diametern d28mm. C
reflektorns öppning / rörets yttre omkrets.
C1/sin a
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Acceptansvinkeln hos denna plåt är ?90 och den
är utformat för ett absorbatorrör med diametern
d28mm.
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Acceptansvinkeln hos denna plåt är ?10 och den
är utformat för ett absorbatorrör med diametern
d28mm.
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Optimering
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Plans - Challenges

• Set up of system- tank needed? - Later a fixed
  system- heat transfer measurements
• Model type in TRNSYS - incidence angle dependence
  
• Ray tracing program
• Analysing data from Vattenfall
• Find manufacturers to create prototypes
• Study heat transfer characteristics - REBUS Oslo
• Vacuum collectors
• Energy efficient buildings - Polysun

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Thank you!