1. How Utilities Can Benefit from Cogeneration Hippo Valley Estates Case Study
AFREPREN/FWD Cogen Centre
Training Workshop on Cogeneration in Africa
10-11 January 2009, Sotik, Kenya

2. CONTENTS OF
PRESENTATION
Cogeneration at Hippo Valley Estates
Perfomance of Chiredzi distribution network
Technical benefits of embedded cogeneration
Economic benefits of embedded cogeneration

3. 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

4. Cogeneration at Hippo Valley Estates (HVE) Key operational parameters
Sugar cane milling period: months
Annual tonnage of crushed cane: 2.3 million tonnes
Boiler characteristics:
6 boilers total rating of bars and 400oC
Turbo Alternators
46 MW but fully function estimated 30 MW
3 boilers have capacities of 40 tonnes/hr
1 boiler has capacity of 100 tonnes/hr
2 boilers have capacities of 68 tonnes/hr

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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
Chiredzi East
32.5
29.0
33.7
31.6
Hippo Valley
32.6
29.3
34.9
33.8
HVE Pumps
34.7
33.5
Statutory limits:
Voltage: ±10% Range ~ 29.7kV to 36.3 (33kV nominal)

11. Load profile for Chiredzi Town (L1)
Impact of HVE demand

12. 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

13. 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

14. 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 MVA 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

15. 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

16. 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