How Utilities Can Benefit from Cogeneration

Hippo Valley Estates Case Study

AFREPREN/FWD Cogen CentreTraining Workshop on Cogeneration in Africa

10-11 January 2009, Sotik, Kenya

CONTENTS OF

PRESENTATION

• Cogeneration at Hippo Valley Estates

• Perfomance of Chiredzi distribution network

• Technical benefits of embedded cogeneration

• Economic benefits of embedded cogeneration

Context of Case Study

• Case study undertaken under “Cogeneration in Zimbabwe: a utility perspective” by Bothwell Batidzirai

• Worked for the electricity utlity ZESA as customer services engineer for 3 years

• Portfolio included agroindustries, farmers and rural communities

• Specific functions included monitoring quality of supply, energy services and customer liaison

Cogeneration at Hippo Valley Estates (HVE)Key operational parameters

• Sugar cane milling period: 9 - 10 months

• Annual tonnage of crushed cane: 2.3 million tonnes

• Boiler characteristics: • 6 boilers total rating of 371 TSH @ 31bars and 400oC

• Turbo Alternators• 46 MW but fully function estimated 30 MW

Cogeneration of electricity and process heat at Hippo Valley Estates (HVE)

• Average HVE estate demand is about 14.5MW

• Up to 11MW excess capacity can be exported the grid (30 GWh – 66GWh p.a.)

• Power Purchase Agreement with ZESA concluded in 2001 to export excess power

• Improvement of Chiredzi network wrt quality of supply, reliability and reduction of losses

Technical benefits - reliability

• Demand in Chiredzi area is 25 MVA

• Up to 11MW available for export to local grid via L1 substation

• HVE feeding L1 in an island mode configuration

Location of power plants and Chiredzi area

• Power production centres distant from Chiredzi area

• Long distance transmission of power

• transmission losses and voltage regulation problems

• Need for boosting supplies in Chiredzi area

Chiredzi distribution network

CHISUMBANJE FDR.

MKWASINE FDR.

RENCO 2 FDR.

RENCO 1 FDR.

CHIREDZI 2 FDR.

CHIREDZI 1 FDR.

33kV BUSBAR

132 kV BUSBAR

N/O

132 kV LINE FROM MIDDLE SABI

PROPOSED 11/33kV INTERCONNECTOR SUBSTATION

FROM HVE POWER STATION

11kV

33kV

CHIREDZI (L1) 15MVA, 33/11KV SUBSTATION

HIPPO VALLEY PUMPS (L16) 5MVA, 33/11KV SUBSTATION

2.4MVAr CAPACITOR BANK AT BUFFALO RANGE

CHIREDZI EAST (L18) 10MVA, 33/11KV SUBSTATION

CHIREDZI RIVER PUMPS SUBSTATIONS 1 & 2, 33/0.38Kv, TOTAL INSTALLED CAPACITY 1.5MVA

MKWASINE 132 KV SUBSTATION

132 kV LINE FROM TRIANGLE

•2 long feeders tied in ring network

• Chiredzi town feeders carry 33% of parent s/s load

• short and long feeders gives voltage regulation problems

Chiredzi network performance analysis• Load flow analysis

• Substation voltage with different loading conditions

• Quality of supply• Maintenance of voltage, frequency within statutory

limits• Voltage and Load profile analysis

• Reliability assessment• Provision of uninterrupted service

Impact of Cogen on Voltage Stability:Load flow analysis

Substation Light load without cogen

Peak load without cogen

Light load with cogen

Peak load with cogen

Chiredzi Town T1

32.7 29.5 34.6 33.6

T2 32.7 29.5 34.6 33.6

Chiredzi East 32.5 29.0 33.7 31.6

Hippo Valley 32.6 29.3 34.9 33.8

HVE Pumps 32.7 29.3 34.7 33.5

Statutory limits:

Voltage: ±10% Range ~ 29.7kV to 36.3 (33kV nominal)

Load profile for Chiredzi Town (L1)

20

30

40

50

60

70

80

90

100

110

26/09/01

27/09/01

28/09/01

29/09/01

30/09/01

01/10/01

02/10/01

03/10/01

04/10/01

05/10/01

06/10/01

07/10/01

08/10/01

09/10/01

10/10/01

11/10/01

Current/A

Impact of HVE demand

Technical benefits – quality of supply • Cogen stabilizes voltage hence improves quality of power

supply

• With cogen the utilitiy does not have to resort to On Load Tap Changing to regulate voltage which can lead to system instability

• With cogen the utility can avoid using line drop compensation which is not effective with long and short feeders from one substation

• Because cogen improves voltage control, it:• Allows increased line loading• Allows extension of line length

Technical benefits - reliability • Cogen ensures:

• Improvement in reliability of supply from local substation

• If national grid collapses, local network not affected and total black out of Chiredzi is avoided

Economic benefits

• Avoided Investment Costs• New generation capacity• 26MW coal thermal costs – USD 31.2 million• Hydro costs – USD 52 million

• Network reinforcement• Uprating feeders to carry higher loads• Substation uprating:• Uprating 15 - 30MVA 33/11kV ss costs ~USD 1 million• Constructing 330/132 kV ss – USD 8.3 million

• Avoided Imports• Interconnectors costly – 330kV costs ~ USD 480,000/km

construction cost & USD 9,600/km maintenance pa• HVE can save USD 1.32 million pa imports

Economic benefits

• Costs Of Meeting Peak Demand• Savings of up to USD 3.5 million for peak demand dispatch

• Reduces cost Of Outages And Unmet Demand  • Reduction In Losses

• load flow shows peak power losses reduced from 16.1% (2,963 kW absolute) without cogeneration to 8.3 % (1,061 kW absolute) with cogeneration

• Voltage Control leads to reduced liability claims

Lessons for Cogen Project Developers

• Similar technical and economic benefits can be demonstrated in other African countries

• Cogen for Africa Project can assist in analyzing and quantifying these benefits and presenting them to utilities and policy makers

THANK YOU