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Optimization studies on integrated wind energy systems
Renewable Energy 16 (1999) 940-943
OPTIMIZATION
STUDIES ON INTEGRATED WIND ENERGY SYSTEMS
COPALAKRISHNAN
NAIR. K AND THYAGAWAN.
K
Department of Mechanical Engineering. College of Engineering. Trivandrum. 695 016. India. GEETHA KUMARI. B
Department of Civil Engineering. SCT College of Engineering. Trivandnun. 695 018. India.
ABSTRACT The results of optimization studies made on a 2 KW. 3 bladed propeller type stand - alone windmill integrated with a diesel generator and battery bank with inverter are presented in this paper. The studies were conducted at Trivandrum and Nagercoil (South India) adjoining Arabian sea. Based on least-cost energy analysis. the design ofa 27MW wind farm is also optimised and presented. $2 1998 Published by Elsevier Science Ltd. All rights reserved. KEYWORDS Integrated Energy. Systems
Wii~dfarms
Stand-alone windmills Optimization studies
1. Introduction Wind energy is one of the most promising and potential sources of energy. Eventhough its availability varies nom place to place. it is an environmentally friendly and clean source of power. However. the main limitation is in obtaining unintenupted power supply. Wind turbine technology has undergone a dramatic transformation during the last two decades. starting from a fringe science in 1970s to the sophisticated wind turbines of the late ’90s. utilising the latest in power electronics. aerodynamics and mechanical drive train design. But for the small disadvantage of noise pollution (definitely much less than many other types ofpower plants). the wind farms are emerging as the most promising and clean source ofenergy. Though options for storage ofthis interrupted source of energy by pumped water. battery bank etc are available. the research on optimising it by integrating with a conventional source and battery / inverter power electronic system are scanty. 2. Wind Data Wind data for the sites have been collected for a period of more than five years and the wind roses were prepared. The usem wind speed was found to be between 6- 12 meters/second. with power generating w-ind available for 113of the time. as illustrated in figure 1. The peak wind speed occurred during 1 I .OOhrs to 18.00 hrs with the most probable direction being 20”N-E. 0960-1481/99/$-see front matter 0 1998 Published by Elsevier Science Ltd. PII: SO960-1481(98)00333-4
All
rights reserved.
WREC 1998
941
3. Integrated Wind Enerev Svstems. The three options ofintegrated wind energy system configurationsare series. switchedand parallel connected These are sho\\n in figure 2.3 and 4. The parallel connected system is found more universalI> acceptable and refined in functioning compared to the first two. which are suitable for some specific applications. In the series configuration. either the renewable source or the DG set will charge the battery depending on the batter! condition. and maintains the charge level. This is decided b!, the availabiliv ofrenenable source and the energ! demand The limitations ofthis system are lower efficient! requirement ofhigher bane]? size and limited diesel control. In the su itched s!-stem mode. DG set meets the load during the peal; period (day time) and the stored energ! from rene\\ able source meets the load during the low-demand period (night). Though the system is simple and quite in operation. it suffers from disadvantages like larger DG set capacit!- to suit the peak load and limited scope ofoptimization. The parallel connected system avoids the limitation ofthe first two systems. The renewable source @\ind mill) and the DG set supply a part of the demand directly. The DG set and inverter run in parallel. The wind battep - im.erter s!.stem supply the power for low load operation : while the DG set and inverter suppI!. fog high load period. Power from DG set is distributed in parallel to load and charges the battery during medium load period. The ~11itching over and control is accomplished by micro -processor based electronic circuit. Phr electronic controller interfaces with the monitors and controls the DG set. wind generator and batter! bank. 4. Ontimization. The integrated energ! s\‘stem should meet the daily and annual energy demand as well as the peak demand at any time. The rene\\ able power supply through the battery and DG set together should be able to meet the peak load ofthe system at any time. The above parameters will decide the size ofthe DG set. wind generatot and the batter)- bank. The DG set capacity is fixed depending on the maximum power that can be drawn fkom bvind generator through batter? - inverter system and duration pattern. 5. Mathematical Model. The power balance equation is given by :
P LD- (P,,,,- P,,)
P,,
. . .. .. .. .. .. ... .. .. ..
(1)
Where P is the po\\er in KW .and suffixes L, W, G, B. and D denotes load. W-G output. D - G output. battery output and dail!, load. Energ\. balance equation is given by :
E
I
E
+EcD+E,,
. .. .
.
(2)
Where E F:the enerl!. in KWH Annual energ! balance equation is : . .. (3) EL.4S EL, + EN \ Where A is annual figure. Using equation ( I ) and (3). for various input values. the output values are obtained and a sensitivity analysis is conducted. assuming different source mix valuesand sizes ofthe components. The corresponding energ! costs for the specific economic scenario are estimated using a software developed for optimization with a wide spectrum of results corresponding to suitable range of input values.
WREC 1998
942
Fig.
HOURS OFTHE 1,
Voriotinn
of
wind
DAY
r.pccd
in
o dqv
Fig
2.
SERIES
CONNECKD
INlEGRAlEU
SYSTEM
6. Outnut characteristics ofthe Commnents. The system is optimized such that the DG set will operate above a certain minimum Diesel Generator Set value ofthe load \iz. 60 % full load to maintain high effkiency as it is clear from Fig.5 The life of batter>- bank is proportional of the depth of discharge Battery Bank (Fig.6). It is clear that shallo\+ discharge depth enables to have increased life. Automatic charge controller enhances the life ofthe batter) InverterA high efficiency MOSFET based inverter witha conversion effkiency of 80 - 90 % is used to realize increased utility ofthe available power. It is reported that the use of high effkiency inverter leads to as much as 50 % sa\ing in the capital cost Wind Generator A typical pattern ofvariation ofthe power and energ! density with wind speed is gken in iigures la and 1b. A 3 bladed propeller type windmill with increasing gear ratio of 120 is used. The output from the Lvind generator set in association with D&et output and batten, ’inverter system is regulated b\ the electronic control delice.
Fig 3.
SWITCHED
IWEGRATED
ENRGY
SYSIEM
WREC
943
1998
10000.0
m 0, -g
0000.0
0’
0.0 LGAD FACTOP
Fig 5.
Load
(uj
for oc
v’s Efficiency
set
Fig. 6
of
I.
I
80.0
(4)
ticltt:wj. lite ~3 dtocborqe
._ . .._.-..
3 “05
I -
5 km
00.0
$schurgP
I IkV tranmIssIw~ Urn runl~ th-ough Wlrd fsnl
<
3
40.0
20.0
b?pth
double clrcult trlln~1.591on
6OkV une
III ml
Fii
slmwm
7. SchematIc fmn
arId
of
-
664v/12@kv
electrical
Interface
between wlnc
grid
7. Results and Discussion.
From the data obtained for various loads the economic analysis for different DG I’WG mix ratios have been done. Diesel /wind capacity calculations of20 : 80. 50 : 50. 80 : 20 have been analyzed. The corresponding sizes ofother components. while meeting the power and energy demand are calculated. Diesel /wind capacity- mix of20 : 80 yields energy at a cost of Rs 2.30 1KWH where diesel/wind mix of 50 : 50 gives a cost of Rs 2.58 / KWH. Studies by varying the system size also revealed that the wind ! diesel mix ratio of80 : 20 was good enough for various capacities of 2 KW. 5 KW. 10 KW and 20 KN:. Based on the Hind data analysis. design of a wind farm of27 MW capacity with 120 wind generators in the range of 200 - 300 KU: was done by finding the distance of rows and columns. The schematic diagram ofthe configuration is given in Fig. 7. A feedback study conducted by a group of research scholars from College ot Engineering. Trioandrum found that the wind farm is functioning satisfactorily,. feeding to the main grid.
LOO.0
OPTIMIZATION
STUDIES ON INTEGRATED WIND ENERGY SYSTEMS
COPALAKRISHNAN
NAIR. K AND THYAGAWAN.
K
Department of Mechanical Engineering. College of Engineering. Trivandrum. 695 016. India. GEETHA KUMARI. B
Department of Civil Engineering. SCT College of Engineering. Trivandnun. 695 018. India.
ABSTRACT The results of optimization studies made on a 2 KW. 3 bladed propeller type stand - alone windmill integrated with a diesel generator and battery bank with inverter are presented in this paper. The studies were conducted at Trivandrum and Nagercoil (South India) adjoining Arabian sea. Based on least-cost energy analysis. the design ofa 27MW wind farm is also optimised and presented. $2 1998 Published by Elsevier Science Ltd. All rights reserved. KEYWORDS Integrated Energy. Systems
Wii~dfarms
Stand-alone windmills Optimization studies
1. Introduction Wind energy is one of the most promising and potential sources of energy. Eventhough its availability varies nom place to place. it is an environmentally friendly and clean source of power. However. the main limitation is in obtaining unintenupted power supply. Wind turbine technology has undergone a dramatic transformation during the last two decades. starting from a fringe science in 1970s to the sophisticated wind turbines of the late ’90s. utilising the latest in power electronics. aerodynamics and mechanical drive train design. But for the small disadvantage of noise pollution (definitely much less than many other types ofpower plants). the wind farms are emerging as the most promising and clean source ofenergy. Though options for storage ofthis interrupted source of energy by pumped water. battery bank etc are available. the research on optimising it by integrating with a conventional source and battery / inverter power electronic system are scanty. 2. Wind Data Wind data for the sites have been collected for a period of more than five years and the wind roses were prepared. The usem wind speed was found to be between 6- 12 meters/second. with power generating w-ind available for 113of the time. as illustrated in figure 1. The peak wind speed occurred during 1 I .OOhrs to 18.00 hrs with the most probable direction being 20”N-E. 0960-1481/99/$-see front matter 0 1998 Published by Elsevier Science Ltd. PII: SO960-1481(98)00333-4
All
rights reserved.
WREC 1998
941
3. Integrated Wind Enerev Svstems. The three options ofintegrated wind energy system configurationsare series. switchedand parallel connected These are sho\\n in figure 2.3 and 4. The parallel connected system is found more universalI> acceptable and refined in functioning compared to the first two. which are suitable for some specific applications. In the series configuration. either the renewable source or the DG set will charge the battery depending on the batter! condition. and maintains the charge level. This is decided b!, the availabiliv ofrenenable source and the energ! demand The limitations ofthis system are lower efficient! requirement ofhigher bane]? size and limited diesel control. In the su itched s!-stem mode. DG set meets the load during the peal; period (day time) and the stored energ! from rene\\ able source meets the load during the low-demand period (night). Though the system is simple and quite in operation. it suffers from disadvantages like larger DG set capacit!- to suit the peak load and limited scope ofoptimization. The parallel connected system avoids the limitation ofthe first two systems. The renewable source @\ind mill) and the DG set supply a part of the demand directly. The DG set and inverter run in parallel. The wind battep - im.erter s!.stem supply the power for low load operation : while the DG set and inverter suppI!. fog high load period. Power from DG set is distributed in parallel to load and charges the battery during medium load period. The ~11itching over and control is accomplished by micro -processor based electronic circuit. Phr electronic controller interfaces with the monitors and controls the DG set. wind generator and batter! bank. 4. Ontimization. The integrated energ! s\‘stem should meet the daily and annual energy demand as well as the peak demand at any time. The rene\\ able power supply through the battery and DG set together should be able to meet the peak load ofthe system at any time. The above parameters will decide the size ofthe DG set. wind generatot and the batter)- bank. The DG set capacity is fixed depending on the maximum power that can be drawn fkom bvind generator through batter? - inverter system and duration pattern. 5. Mathematical Model. The power balance equation is given by :
P LD- (P,,,,- P,,)
P,,
. . .. .. .. .. .. ... .. .. ..
(1)
Where P is the po\\er in KW .and suffixes L, W, G, B. and D denotes load. W-G output. D - G output. battery output and dail!, load. Energ\. balance equation is given by :
E
I
E
+EcD+E,,
. .. .
.
(2)
Where E F:the enerl!. in KWH Annual energ! balance equation is : . .. (3) EL.4S EL, + EN \ Where A is annual figure. Using equation ( I ) and (3). for various input values. the output values are obtained and a sensitivity analysis is conducted. assuming different source mix valuesand sizes ofthe components. The corresponding energ! costs for the specific economic scenario are estimated using a software developed for optimization with a wide spectrum of results corresponding to suitable range of input values.
WREC 1998
942
Fig.
HOURS OFTHE 1,
Voriotinn
of
wind
DAY
r.pccd
in
o dqv
Fig
2.
SERIES
CONNECKD
INlEGRAlEU
SYSTEM
6. Outnut characteristics ofthe Commnents. The system is optimized such that the DG set will operate above a certain minimum Diesel Generator Set value ofthe load \iz. 60 % full load to maintain high effkiency as it is clear from Fig.5 The life of batter>- bank is proportional of the depth of discharge Battery Bank (Fig.6). It is clear that shallo\+ discharge depth enables to have increased life. Automatic charge controller enhances the life ofthe batter) InverterA high efficiency MOSFET based inverter witha conversion effkiency of 80 - 90 % is used to realize increased utility ofthe available power. It is reported that the use of high effkiency inverter leads to as much as 50 % sa\ing in the capital cost Wind Generator A typical pattern ofvariation ofthe power and energ! density with wind speed is gken in iigures la and 1b. A 3 bladed propeller type windmill with increasing gear ratio of 120 is used. The output from the Lvind generator set in association with D&et output and batten, ’inverter system is regulated b\ the electronic control delice.
Fig 3.
SWITCHED
IWEGRATED
ENRGY
SYSIEM
WREC
943
1998
10000.0
m 0, -g
0000.0
0’
0.0 LGAD FACTOP
Fig 5.
Load
(uj
for oc
v’s Efficiency
set
Fig. 6
of
I.
I
80.0
(4)
ticltt:wj. lite ~3 dtocborqe
._ . .._.-..
3 “05
I -
5 km
00.0
$schurgP
I IkV tranmIssIw~ Urn runl~ th-ough Wlrd fsnl
<
3
40.0
20.0
b?pth
double clrcult trlln~1.591on
6OkV une
III ml
Fii
slmwm
7. SchematIc fmn
arId
of
-
664v/12@kv
electrical
Interface
between wlnc
grid
7. Results and Discussion.
From the data obtained for various loads the economic analysis for different DG I’WG mix ratios have been done. Diesel /wind capacity calculations of20 : 80. 50 : 50. 80 : 20 have been analyzed. The corresponding sizes ofother components. while meeting the power and energy demand are calculated. Diesel /wind capacity- mix of20 : 80 yields energy at a cost of Rs 2.30 1KWH where diesel/wind mix of 50 : 50 gives a cost of Rs 2.58 / KWH. Studies by varying the system size also revealed that the wind ! diesel mix ratio of80 : 20 was good enough for various capacities of 2 KW. 5 KW. 10 KW and 20 KN:. Based on the Hind data analysis. design of a wind farm of27 MW capacity with 120 wind generators in the range of 200 - 300 KU: was done by finding the distance of rows and columns. The schematic diagram ofthe configuration is given in Fig. 7. A feedback study conducted by a group of research scholars from College ot Engineering. Trioandrum found that the wind farm is functioning satisfactorily,. feeding to the main grid.
LOO.0