River Current Resource Assessment and Characterization Considering Ice Conditions 1 Gilles Boesch, Eng, M.Eng Marie-Hélène Briand, Eng, PhD Vadim Belotserkovsky International Conference on Ocean Energy, Halifax, Nova Scotia November 06, 2014
2 Overview Background Part 1: Ice-free aspects Reconnaissance Study (Stage 1) Pre and Full Feasibility Study (Stage 2A and 2B) Layout Design (Stage 3) Part 2: Ice Processes and Impacts on Resource Assessment Ice characteristics (frazil, ice cover, ice jam ) Impacts on the Resource for all Stages
3 Background 120 TWh/yr of technically recoverable energy in the continental US 1 750 GW of total hydrokinetic power in Canada 2 No standards currently exist for River Current Resource Assessments Accelerate the development of technical guidelines Present guidelines using the terminology from IEC62600-201 ( Tidal Energy Resource Assessment and Characterization ) Integrate aspects related to ice impacts for Northern climate applications 1 EPRI, Assessment and Mapping of the Riverine Hydrokinetic Resource in the Continental United States 2 NRC, Assessment of Canada s Hydrokinetic Power Potential
4 Background IEC62600-201 phased approach: Stage 1 (Reconnaissance Study) Large scale (River) Stage 2A and 2B (Feasibility Study) Medium scale (River section) Stage 3 (Layout Design Study) Small scale (Device location)
PART 1: Ice-free aspects 5 Phase 1: Reconnaissance study Assume a cross-sectional shape (trapezoidal) Continuity and Manning equation Input: Discharge, slope, river width Output: Velocity and depth for each section Available Theoretical Power: Selection of Potential Sections for further development: Technology specific Generally V > 1.5m/s and Depth > 4m Other constrains (transmission lines, environmental, constructability etc.) Impact of ice
6 Phase 1: Reconnaissance study (Validation) Validation of the simplified methodology based on: HEC-Ras (1-D) calibrated model for a major Canadian river Bathymetry data Surveyed Manning coefficient Source of error from the topographical data and Manning coefficient Selection of the best River Sections (Proposed method VS HEC-Ras model with detailed bathymetry) 50% confirmed by the HEC-Ras model
7 Stage 2: Pre- and Full Feasibility Study When reaches are selected based on Stage 1 results Field Surveys (for model calibration) : Bathymetry Hydraulic Surveys (Velocity profile, discharge seasonal/yearly variability, depth etc.) Ice (frazil, open water, ice cover etc.) Sediment Debris (wood, aquatic plants...) Numerical models 2-D: Depth-averaged models (Stage 2A) 3-D (Stage 2B) Stone et al, 2007
8 Stage 3: Layout Design Project optimization (type/number of devices, location) Turbulence considerations (loads on turbines, energy extraction) Net Energy Predictions Turbine Power Curve Losses Assessment (wake effects, unavailability, electrical losses etc.) Uncertainty Analysis and probability of exceedence (P50, P90, P99)
PART 2: Ice processes and impacts on resource assessment 9 Ice Processes Review Frazil Ice Supercooled water, very sticky Anchor Ice Frazil sticking to river bed Ice Floes Frazil that becomes buoyant Ice Cover Dynamic (Ice floes jam) or static (low velocity) Hanging Dam Ice Jam Ice cover Hanging Dam
10 Stage 1: Reconnaissance Study Frazil In turbulent supercooled water (-0.01degC) Very sticky in active mode Visual Approach (detection of rapids) High Froude number (high turbulence) Rapids
11 Stage 1: Reconnaissance Study Ice cover: Progression Critical Froude number = 0.154(1-p j ) (Prowse, 1996) Fr < Fr c Ice cover progression Fr > Fr c Underturning of drifting floes Can create Hanging Dams Open Water with high Froude number upstream Frazil Ice Hydraulic Impact: Additional roughness Composite Manning coefficient
12 Stage 1: Reconnaissance Study Hanging Dams Slow velocity section downstream of Frazil producing area Leading edge of an ice cover Preliminary findings: Froude gradient along the river Ice Jam In areas where the ice transport capacity is exceeded Visual approach (confluence, bending, narrowing, islands ) Change in slope (from open water reconnaissance study) Hanging Dams
13 Stage 2: Pre- and Full Feasibility Study Field Surveys Ice Observations Cover progression upstream Aerial survey, Satellite Imagery Ice thickness Ice jam observations Aerial survey, Satellite Imagery Frazil ice (underwater rods) Ice Floe concentration Aerial survey, Satellite Imagery Temperature Measurements: Air Temperature (local weather stations) Water Temperature (Frazil onset detection) Degree Day of Freezing (DDF), severity of winter Stage and Velocity Garver, 2007
14 Stage 2: Pre- and Full Feasibility Study Modeling Only 2D for ice processes Hydrodynamic Models in Ice Conditions (flow characteristics) Ice Dynamic Models Malenchak, 2011
15 Stage 3: Layout Design Avoid areas with frazil, ice jam or hanging dams Support the additional loads due to ice impacts Lower availability in ice conditions Collaborative effort with turbine manufacturer
16 Conclusion Resource Assessment process Complex in Ice Conditions Phased approach: Early detection of fatal flaws Easier monitoring planning Further Developments: Validation of Froude number to detect frazil, ice floes or hanging dams Numerical model validation (ice) Field surveys Energy losses due to ice Ice Mitigation means
17 Thank you Gilles Boesch, Eng, M.Eng gboesch@hatch.ca Hatch, Renewable Power