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Hydropower modelling
Vientiane January 24. 2018
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Energy from hydropowerH
ead
, dH
Hydropower plants transforms the potential energy in water to electricity. Energy is calculated by the following equation:
𝐸 = η ∙ 𝜌 ∙ 𝑔 ∙ 𝑄 ∙ 𝑑𝐻
When η (efficiency), ρ (=1000 kg/m³) and g (=9,81 m/s²) are constant, generated poweronly depends on head (dH) and turbine flow (Q).
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How does mitigation measures affect hydropowergeneration and revenue?
• Reduced flow through the turbines- Loss of water due to minimum flow, sediment flushing etc.- Loss of water due to reservoir operations that increase the
flood loss- Reduced generation and revenue
• Reduced head (lower head water level and/or higher tail water level)- Reduced head due to flushing/slucing or other environmental
concerns- Reduced generation and revenue
• Generation at times when the power price is low- Reduced revenue
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Types of hydropower plants
• Reservoir- No active reservoir: Run-of-river
hydropower▪ Outflow = inflow▪ Water is lost during floods
- Reservoir: Daily, weekly, monthly, seasonal or annual storage▪ Water is saved to be used when needed
• Head- Low head <30 m- Medium 30 – 200 m- High head >200 m
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Types of models• Many different models can be used for hydropower modelling. Choice of model
depends on types of hydropower plant, and what output is needed.• Types of models:- Hydraulic models
▪ ISIS, HEC-Ras, MIKE11▪ Good for: Low-head schemes, hydropower plants with challenging hydraulics▪ Disadvantages: Large and complicated models, (often) no in-model hydropower calculation
- Water balance models▪ IQQM, HEC-ResSim, MIKE Basin▪ Good for: Multi-purpose projects, larger river basins▪ Disadvantages: No hydraulics in the model, some models not suited for all hydropower
operation
- Hydropower production models▪ MaxHydro, Optipower, Powel Optimal Hydropower▪ Good for: Production planning and forecasting, optimizing revenue▪ Disadvantages: No hydraulics in the model, models often do not take into account other
water uses
- Spreadsheet models▪ Good for: Simple systems▪ Disadvantages: Not suited for complex systems
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Hydraulic model example: MIKE 11
• Hydraulic model- Based on Navier-Stokes
equations- Fully dynamic model
• River is defined by cross-section profiles- From terrain model- Calibrated to observed data
• Operation rules defined in structures (dams) in the river network- Flexible, but may require (a
lot) of programming• Output: Flow and water levels- Power generation calculated
separately
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Water balance model example: HEC-ResSim
• The reservoir system is built using a network of elements (junctions, routingreaches, diversion, reservoirs)
• Based on water balance equations- Level pool assumption
• Goals and restrictions can be added to the different elements
• Not a hydraulic model- Capacity curves, tailwater curves,
travel time etc. must be specified in the model
- Input from a hydraulic model willimprove the results
• Output: Flow and water levels- Power generation calculated
separately or- Power generation calculated in the
model
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Hydropower production models
• Different types ofmodels:
- Hydropower planning models▪ Water balance models,
more focused on HPP
- Hydropower operationmodels▪ Long term or short-term
▪ Usually includesforecasting (hydrologicalmodel)
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Spreadsheet models: Excel
• Sometimes, complicated models are not needed
• Spread sheet models may be a good alternative if
- Limited number of HPP
- Only concerned about power generation
- No optimization of water uses
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Which model to choose?
• Several existing power plants in the same river basin. Severalreservoirs
- Power planning model if hydropower is the only consideration
- Otherwise: water balance model
• Two high-head run-of-river HPPs
- Spreadsheet model
• Cascade of low-head run-of-river HPPs
- Hydraulic model
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Hydropower modelling. What data is needed?
1. Data series for inflow Q- Usually daily data for 30 years- For large reservoir schemes, or when the variation in flow is small, weekly or
monthly data may be ok- For very small (<5 MW) run-off-river plants, hourly data is better
2. Efficency curves for electro-mechanical equipment η- Turbines, generators, transformers
3. Reservoir volume curves (if reservoir scheme) dH, Q4. Tailwater curve (if large variation in tail water level) dH- In the Mekong, the variation in TWL can be more than 10 meters, which may
be 50% of the head!5. Hydropower key data dH, Q- Max and minimum turbine flow- Design of waterways
6. Information about other water uses and mitigation measures dH, Q7. Power tariffs
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Modelling of run-of-river HPPs
(from case study)
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Modelling of reservoir schemes
(example reservoir modelling)