Simple wind-diesel concept with high wind penetration in Cape Verde

1. Simple wind-diesel conceptwith high wind penetrationin Cape Verde Per Nørgård, Risø DTU, Denmark, pern@risoe.dtu.dk João Fonseca, Electra, Cabo Verde, j.fonseca@electra.cv

2. Cabo Verde • Independent (from Portugal) in 1955 • Population: 500 000 at 10 islands • Islands in study: • Santiago • São Vicente • Sal • (Boa Vista)

3. Cabo Verde Risø DTU as Technical Consultant • for InfraCo (international project developer) • in collaboration with Electra (local power utility company) Power generation based on diesel generation Excellent wind conditions • High average wind speeds most of the year • Very constant wind • Low extreme wind speed

4. Growing demand

5. IPSYSan energy system simulation tool Characteristics • Semi-static time series simulation (minutes time steps) • Includes storage and memory functionalities • Designed for mixed energy systems • Performs energy balances and load flow analysis (power systems) • Handles advanced and distributed control • Developed by Risø DTU

6. Simplified single line diagrams

7. Operation strategy Minimum continuous diesel load Minimum instantaneous diesel load Minimum spinning reserve diesel capacity Minimum diesel capacity Minimum number of diesel generator units Minimum diesel operation time • Minimum continuous load of the diesel engines: 30% (optional 50%). • To prevent the diesel engines from sooting up at low load. • The wind power generation may be limited to fulfil this condition.

8. Operation strategy Minimum continuous diesel load Minimum instantaneous diesel load Minimum spinning reserve diesel capacity Minimum diesel capacity Minimum number of diesel generator units Minimum diesel operation time • Minimum instantaneous load of the diesel engines: 10%. • To prevent for negative load of the diesel generators.

9. Operation strategy Minimum continuous diesel load Minimum instantaneous diesel load Minimum spinning reserve diesel capacity Minimum diesel capacity Minimum number of diesel generator units Minimum diesel operation time • Minimum spinning reserve diesel capacity connected to the grid: 200% of the observed fluctuation of the diesel load within the last hour and minimum 50% of the actual diesel load (if possible). • To be prepared for the fluctuations in the wind power and in the load.

10. Operation strategy Minimum continuous diesel load Minimum instantaneous diesel load Minimum spinning reserve diesel capacity Minimum diesel capacity Minimum number of diesel generator units Minimum diesel operation time • Minimum diesel capacity connected to the grid: 2 times the wind capacity connected to the grid. • To ensure dynamic stability of the system. • @ low load + high wind: wind turbines are shut down -> diesel generators shut down

11. Operation strategy Minimum continuous diesel load Minimum instantaneous diesel load Minimum spinning reserve diesel capacity Minimum diesel capacity Minimum number of diesel generator units Minimum diesel operation time • Minimum number of diesel generator units connected to the grid: 2 • Not to rely on a single diesel generator unit.

12. Operation strategy Minimum continuous diesel load Minimum instantaneous diesel load Minimum spinning reserve diesel capacity Minimum diesel capacity Minimum number of diesel generator units Minimum diesel operation time • Minimum operation time of a diesel engine: 4 hours. • To limit the number of start / stop of the diesel engines.

13. Load profiles(3x3 days)

14. Seasonal variation of wind

15. IPSYS results (Sao Vicente)

16. Summary of results

17. Not utilised wind energy 1 p.u.: 20% wind energy penetration

18. Avoided diesel fuel 1 p.u.: 20% wind energy penetration

19. Minimum diesel load (2012)

20. PPA – Power Purchase Agreement Minimum wind energy level’take & pay’ @ high tariff • Motivates wind power operatorto maximise production Additional wind energy@ low tariff • Motivates diesel operatorto optimise operation

21. Conclusions • The most critical operation parameter is the minimum diesel load. • Even at 40% wind energy penetration, the not utilised wind energy is ’only’ 10%. • 20% ’overinvestment’ in wind power capacity is proposed 22 MW -> 28 MW -> 0..10% not utilised wind energy. • This seems economically feasible at 5% reduced generation cost ($/kWh), with the expected demand growth.

22. Hall 2 Thanks!Seeing you atStand 2463 (Hall 2) Per Nørgård Risø DTU, Denmark pern@risoe.dtu.dk