September, 2002 PHOENICS Conf Moscow1 Modeling Performance of WECS Installed in Residential Towers M.A. Serag-Eldin American University in Cairo

September, 2002 PHOENICS Conf Moscow 1

Modeling Performance of WECS Installed in Residential Towers

M.A. Serag-EldinAmerican University in Cairo


INTRODUCTION-I

It has beenproposed toexploit highbuilding structures in windy areas toinstall WECS


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


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


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


Source term expressions

S

u - p/x+(eu/x)/x+(ev/x)/y+(ew/x)/z

v - p/y+(eu/y)/x+(ev/y)/y+(ew/y)/z

w - p/z+(eu/z)/x+(ev/z)/y+(ew/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


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/( C1/2 )

• =(s/)3/2/y


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/(C1/2)

= (s/)3/2 / y Side boundaries: symmetry boundary and undisturbed

atmospheric flow


CASE I : Rectangular Blocks w/o Bottom Pass


TOP VIEW OF BUILDING

Wind direction


Cross-sectional elevation


Grid at WECS k-plane


Grid Enlargement


Grid at Cowl Entrance


Grid in Hub j-plane

Wind

direction


Grid in Symmetry Plane

Wind

direction


Flow in Symmetry Plane


Enlargement of Flow


Pressure in symmetry plane


Flow in Hub1 j-plane


Pressure in Hub Plane


Case II: Open Pass


Flow in Symmetry Plane




Case III: convergent-divergent blocks


Flow in Hub 1 j-plane


Flow in Hub 3 j-plane


Flow in symmetry plane


Pressure in Hub1 j-plane


Case IV: Turbine 2 out of service


Pressure distribution


Case V: Roof Turbine


Flow in symmetry plane




Pressure in Turbines’ plane


Summary of Results for 5 Cases

Wind Turbine 1 Wind Turbine 2 Wind Turbine 3Case No. &Description V(m/s) P (KW) V(m/s) P (KW) V(m/s) P (KW)

TotalPower

I (R,NP) 6.179 45.291 6.654 50.409 6.881 52.856 148.556II(R,P) 6.442 48.125 6.615 49.989 6.819 52.188 150.302III(C/D,P) 6.298 46.573 6.977 53.890 7.653 60.628 161.091IV( III,N2T) 6.407 47.748 - - 8.002 64.055 111.803V (III,RT) 5.8 41.290 6.583 49.644 6.071 44.127 135.061

Wind Turbine 1 Wind Turbine 2 Wind Turbine 3Case No. &

Description V(m/s) P (KW) V(m/s) P (KW) V(m/s) P (KW)

Total

Power

I (R,NP) 6.179 45.291 6.654 50.409 6.881 52.856 148.556

II(R,P) 6.442 48.125 6.615 49.989 6.819 52.188 150.302

III(C/D,P) 6.298 46.573 6.977 53.890 7.653 60.628 161.091

IV( III,N2T) 6.407 47.748 - - 8.002 64.055 111.803

V (III,RT) 5.8 41.290 6.583 49.644 6.071 44.127 135.061


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 .

Documents

September, 2002 PHOENICS Conf Moscow1 Modeling Performance of WECS Installed in Residential Towers M.A. Serag-Eldin American University in Cairo