Modeling Performance of WECS Installed in Residential Towers

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Modeling Performance of WECS Installed in
Residential Towers

• M.A. Serag-Eldin
• American University in Cairo

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INTRODUCTION-I

• It has been
• proposed to
• exploit high
• building
• structures in
• windy areas to
• install WECS

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INTRODUCTION-II

• Advantages
• Saving in WECS tower cost
• Saving of land required for wind-farms
• Saving of energy transmission costs
• Possibility of increasing wind speed due to
  funneling effect

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OBJECTIVES

• Present a computer model for WECS confined amidst
  building blocks.
• Reveal how the model is implemented in PHOENICS
• Demonstrate the application of the model , and
  reveal its use as a design tool

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Modeling Wind Flow

• Domain assumed entirely in constant stress layer,
  with neutral stability
• k-? model of turbulence
• governing equations expressing mass conservation,
  momentum balance in 3D, transport of k and ?
• eqns of form ? . ( ? V ? ) ? . ( ?? ?? )
  S?
• where ? any dependent variable , V u i v j
  w k
• ?? and S? are the diffusion coefficient and
  source term, respectively , for ?

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Source term expressions

• ? S?
• u - ?p/?x?(?e?u/?x)/?x?(?e?v/?x)/?y?(?e?w/?x)/?
  z
• v - ?p/?y?(?e?u/?y)/?x?(?e?v/?y)/?y?(?e?w/?y)/?
  z
• w - ?p/?z?(?e?u/?z)/?x?(?e?v/?z)/?y?(?e?w/?z)/?
  z
• k Gk - ? ?
• ? C1 ?/k.Gk - C2 ? ?2/k
• Gk ?t 2(?u/?x)2 (?v/?y)2 (?w/?z)2
  (?u/?y?v/?x)2
• ( ?u/?z?w/?x)2 (?v/?z?w/?y)2 ,
  ?t ? ? C? k2 /?
• standard (k-?) model coefficients

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WECS model BCs

• WECS characteristics displayed as power/thrust
  .vs.w
• thrust effect introduced implicitly through w
  source-term
• Inflow B.C.s
• Undisturbed Atmospheric Flow, i.e.
• u v 0
• w 1 / ?. (?s/?)1/2 ln(y/yo)
• k ?s/(? C?1/2 )
• ?(?s/?)3/2/?y
  

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Boundary-Conditions-II

• Top boundary undisturbed atmospheric flow.
• Outflow boundary constant press, zero gradients
• Ground boundary
• us vs ws 0
• ?s ? ?/ln(y/yo)2 (w2 u2)
• k ?s/(?C?1/2)
• ? (?s/?)3/2 / ?y
• Side boundaries symmetry boundary and
  undisturbed atmospheric flow

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CASE I Rectangular Blocks w/o Bottom Pass
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TOP VIEW OF BUILDING
Wind direction
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Cross-sectional elevation
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Grid at WECS k-plane
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Grid Enlargement
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Grid at Cowl Entrance
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Grid in Hub j-plane
Wind
direction
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Grid in Symmetry Plane
Wind
direction
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Flow in Symmetry Plane
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Enlargement of Flow
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Pressure in symmetry plane
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Flow in Hub1 j-plane
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Pressure in Hub Plane
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Case II Open Pass
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Flow in Symmetry Plane
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Pressure in symmetry plane
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Case III convergent-divergent blocks
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Flow in Hub 1 j-plane
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Flow in Hub 3 j-plane
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Flow in symmetry plane
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Pressure in Hub1 j-plane
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Case IV Turbine 2 out of service
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Pressure distribution
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Case V Roof Turbine
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Flow in symmetry plane
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Pressure in symmetry plane
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Pressure in Turbines plane
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Summary of Results for 5 Cases
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Summary Conclusion

• The predictions revealed that there is a gain in
  speed for all cases which varied from case to
  case, albeit not very spectacular best results
  require careful design of building shape,
  however this must be developed in conjunction
  with architectural requirements
• the number of variables that need to be
  investigated are enormous, including various
  building shapes and dimensions, HAWT
  character-istics and location, wind speed and
  direction, upstream wind profile and presence of
  nearby flow obstacles all of which may be
  readily investigated with the aid of the present
  model .