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Why go Solar PV?. Integrating a large solar array to enhance the performance of a low energy building. - A Case Study. Building Research Establishment 20 th June 2007. Keith Tovey ( 杜伟贤 ) M.A., PhD, CEng, MICE, CEnv HSBC Director of Low Carbon Innovation: - PowerPoint PPT Presentation
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Building Research Establishment 20th June 2007
Integrating a large solar array to enhance the performance of a low energy building.
- A Case Study
Keith Tovey ( 杜伟贤 ) M.A., PhD, CEng, MICE, CEnvHSBC Director of Low Carbon Innovation: and Charlotte Turner: School of Environmental SciencesCRed
Why go Solar PV?
Original buildings
Teaching wall
Library
Student residences
Nelson Court
Constable Terrace
Low Energy Educational Buildings
Elizabeth Fry Building
ZICER
Nursing and Midwifery
School
Medical School
Medical School Phase 2
• The ZICER Building
• The Solar Arrays
• Performance of PV
• Issues of Shadowing
• Electrical Integration
• Economic Issues
• Life Cycle Issues
Integrating a large solar array to enhance the performance of a low energy building.
ZICER Building
Heating Energy consumption as new in 2003 was reduced by further 50% by careful record keeping, management techniques and an adaptive approach to control.Incorporates 34 kW of Solar Panels on top floor
Low Energy Building of the Year Award 2005 awarded by the Carbon Trust.
Two large open plan offices: Note: extensive use of computers
• Top floor is an exhibition area – also to promote PV
• Windows are semi transparent
• Mono-crystalline PV on roof ~ 17 kW in 10 arrays
• Poly- crystalline on façade ~ 6/7 kW in 3 arrays
ZICER Building
0
500
1000
1500
2000
2500
3000
3500
Jan Apr Jul Oct Jan Apr Jul Oct
2004 2005
kWh
Façade Roof
ZICER Building PV performance
Façade (kWh) Roof (kWh) Total (kWh)
2004 2650 19401 22051
2005 2840 19809 22649
Summer day (27th June 2005)
0
5
10
15
20
25
05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20
Time of Day (starting time)
PV
(A
C)
ou
tpu
t (k
Wh
)
0100
200300
400500600
700800
9001000
Mea
n R
adia
tio
n (
W/m
2 )PV Output Solar Radiation
Cloudy Summer day (04/05/2005)
0.0
0.5
1.0
1.5
2.0
2.5
05 07 09 11 13 15 17 19
Time of Day (starting time)
PV
AC
ou
tpu
t (k
Wh
)
0
20
40
60
80
100M
ea
n r
ad
iati
on
(W/m
2 )PV OutputSolar Radiation
Winter Sunny Day (19th Jan 2005)
0
2
4
6
8
10
12
14
08 09 10 11 12 13 14 15 16
Time of Day (starting time)
PV
(A
C)
ou
tpu
t (k
Wh
)
0
200
400
600
800
1000
1200
1400
Mea
n R
adia
tio
n (
W/m
2)
PV output
Solar Radiation
Performance of PV cells on ZICER
0%
2%
4%
6%
8%
10%
12%
14%
16%
Jan Mar May Jul Sep Nov Jan Mar May Jul Sep Nov
2004 2005
Lo
ad
Fa
cto
rfaçade roof average
0
2
4
6
8
10
12
14
16
18
Jan Mar May Jul Sep Nov Jan Mar May Jul Sep Nov
2004 2005
kWh
/ m
2
Façade Roof
Load factors
Façade:
2% in winter
~8% in summer
Roof
2% in winter
15% in summer
Output per unit area
Little difference between orientations in winter months
Performance of PV cells on ZICER
0
2040
6080
100120140
160180200
9 10 11 12 13 14 15Time of Day
Wh
01020
3040506070
8090100
%
Top Row
Middle Row
Bottom Row
radiation
0
10
20
30
40
50
60
70
80
90
100
9 10 11 12 13 14 15Time of day
Wh
0
10
20
30
40
50
60
70
80
90
100
%
Block1
Block 2
Block 3
Block 4
Block 5
Block 6
Block 7
Block 8
Block 9
Block 10
radiation
All arrays of cells on roof have similar performance respond to actual solar radiation
The three arrays on the façade respond differently
Performance of PV cells on ZICER
0
2
4
6
8
10
12
14
16
18
20
8.00 9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00
Elev
ation
in th
e sky
(deg
rees)
120 150 180 210 240Orientation relative to True North
0
5
10
15
20
25
6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00Time (hours)
Elev
ation
in th
e sky
(deg
rees)
January February March AprilMay June July AugustSeptember October November DecemberP1 - bottom PV row P2 - middle PV row P3 - top PV row
0
5
10
15
20
25
8.00 9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00
Time (hours)
Elev
ation
in th
e sky
(deg
rees)
January February November DecemberP1 - bottom PV row P2 - middle PV row P3 - top PV row
Arrangement of Cells on Facade
Individual cells are connected horizontally
As shadow covers one column all cells are inactive
If individual cells are connected vertically, only those cells actually in shadow are affected.
0
1000
2000
3000
4000
5000
6000
7000
(Jan ) 1 (Mar) 11 (May) 21 (Aug) 31 (Oct) 41 (Dec) 51
Time (week number)
Ele
ctri
city
use
d/ge
nera
ted
(kW
h)
0
10
20
30
40
50
60
70
PV
per
cent
age
of th
e to
tal e
lect
rici
ty u
sage
Electricity from conventional sources PV electricity PV % of total
Performance of PV cells on ZICER
0
1
2
3
4
400 600 800 1000 1200 1400
Annual Average Solar Radiation (kWhm-2yr-1)
PC
cos
t (£
/kW
h) A
B
C
D
E
F
• (A) Actual ZICER costs – no grant• (B) Actual ZICER costs – with grant of £172 000• (C) Avoided costs (ZICER) – no grant• (D) Avoided costs (ZICER) with grant of £172 000• (E) Average EU costs in 2006• (F) as E with 50% capital grant
Performance of PV cells on ZICERCost of Generated Electricity
Actual Situation excluding Grant
Actual Situation with Grant
Discount rate 3% 5% 7% 3% 5% 7%
Unit energy cost per kWh (£) 1.29 1.58 1.88 0.84 1.02 1.22
Avoided cost exc. the Grant
Avoided Costs with Grant
Discount rate 3% 5% 7% 3% 5% 7%
Unit energy cost per kWh (£) 0.57 0.70 0.83 0.12 0.14 0.16
Grant was ~ £172 000 out of a total of ~ £480 000
Performance of PV cells on ZICERCost of Generated Electricity
• Peak Cell efficiency is ~ 9.5%.
• Average efficiency over year is 7.5%
Mono-crystalline Cell Efficiency Poly-crystalline Cell Efficiency
Efficiency of PV Cells
• Peak Cell efficiency is ~ 14% and close to standard test bed efficiency.
• Most projections of performance use this efficiency
• Average efficiency over year is 11.1%
Inverter Efficiencies reduce overall system efficiencies to 10.1% and 6.73% respectively
Comparison of other PV Systems
LocationMonitoring
Period
System Efficiency
(%)Source
Northumberland Building, University of Northumbria.
1995-1997 8.1 Pearsall
Solar Office Doxford International, Sunderland, UK
Mar 1998-May 2000
7.5-8 Jones
Jubilee Campus, Nottingham University, Nottingham, UK
Sept 2000-Aug 2001
8Riffat and
Gan
Eco Energy House, Nottingham University, Nottingham, UK
Sept 2000-May 2002
3.6 Omer et al.
Gaia Energy Centre, Delabole, Cornwall, UK
Jan 2003-June 2003
9-10 DTI
PV Domestic Installations, UK (Average of six systems)
12 – 25 months8.2 (range
6.5-10.4)Pearsall and
Hynes
ECOS Millennium Environmental Centre, Ballymena, Northern Ireland
Dec 2000-Dec 2003
7.7Smyth and
Mondol
Performance of Photo Voltaic Array
Inverters are only 91% efficient
Most use is for computers
DC power packs are inefficient typically less than 60% efficient
Need an integrated approach
Life Cycle Issues
Embodied Energy in PV Cells (most arising from Electricity use in manufacture) 3230 2750
Array supports and system connections 285 285
On site Installation energy 131.4 131.4
Transportation Spain > Germany > UK11250 vehicle-kilometres
453.2 453.2
Total MWh/kWp 4.1 3.4
Mono-crystalline
(kWh/kWp)
Poly-crystalline
(kWh/kWp)
Energy Yield Ratios
Mono-crystalline Cells 20 25 30
As add on features 3.2 3.8 4.6
Integrated into design 3.5 4.2 5.4
Life Time of cells (years)
Conclusions
• Economics of PV was only viable on ZICER because of Grant• Shading has some effect on façade, but improvements could be
made by different method of wiring cells• Overall Load Factor is 7.6% with 8.3% on roof and 4.7% on
façade. In summer Load Factor can reach 15%.• 9% of electricity is lost in inverters, and a further 50 – 60% is
lost in IT equipment.• Need to consider an integrated approach – possibly with DC
networks in similar buildings.• Important to use actual rather than test bed efficiencies in
design appraisal• Energy Yield Ratios are lower than many other forms of
generation. Long transportation distances associated with PVs do not necessarily lead to a low embodied carbon requirement.
Keith Tovey ( 杜伟贤 ) M.A., PhD, CEng, MICE, CEnvHSBC Director of Low Carbon Innovation: and Charlotte Turner: School of Environmental SciencesCRed
Building Research Establishment 20th June 2007
Integrating a large solar array to enhance the performance of a low energy building.
- A Case Study
Keith Tovey ( 杜伟贤 ) M.A., PhD, CEng, MICE, CEnvHSBC Director of Low Carbon Innovation: and Charlotte Turner: School of Environmental SciencesCRed
Why go Solar PV?
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