Hydro Power 102

Hydroelectric Models in the Northwest

Three Regional Models l Hydro Simulator Program (HYDROSIM) –Bonneville Power Administration l Hydro System Seasonal Regulation (HYSSR) –Corps of Engineers l PNCA Seasonal Regulation (HYDREG) –Northwest Power Pool

Common Elements l Simulate the hydroelectric operation over 14 periods per year (split April and August) l Share hydroelectric project data l Share historical stream flow/irrigation data l Share flood control data

HYDROSIM - BPA l Columbia River Treaty (Coordination with the Canadian Operation) l White Book (NW Loads and Resources) l EIS (Environmental Impact Statement) l Biological Opinion (Endangered Species) l Long-term planning

HYSSR - Corps l Columbia River Treaty (Coordination with the Canadian Operation) l Flood Control Development l EIS (Environmental Impact Statement) l Biological Opinion (Endangered Species) l Evaluation of System Changes (new storage, revised irrigation withdrawals, etc.)

HYDREG - PNCA l Power Pool Operating Program l Critical Period Evaluation l FELCC (Firm Energy Load Carrying Capability) l Headwater Benefits l Each Party’s Rights and Obligations

Modeling the Hydroelectric System

Tapping the Power of the River A Few Definitions l Potential Energy = stored energy proportional to the height above ground l Kinetic Energy = energy of motion proportional to the velocity

Tapping the Power of the River l A ball resting at the top of an incline has no motion and thus no kinetic energy. l With a little push, the ball rolls down the incline, picking up speed as it rolls. l At the bottom, the ball has its highest speed but can fall no further. l This is an example of converting potential energy to kinetic energy.

Tapping the Power of the River l Water in the forebay is passed through a turbine. l As the water falls, it forces the turbine blades to turn. l As the turbine rotates, it converts the mechanical energy of rotation into electricity. l Thus, we can capture some of the water’s potential energy.

Tapping the Power of the River l Power = Flow x Head x Constant Power is measured in megawatts (million watts) Flow is measured in cubic feet per second Head is measured in feet Constant is a function of the turbine’s efficiency l Example at Grand Coulee Dam Flow is 100,000 cubic feet per second Head is 328 feet Constant is.075 Power = 100,000 x 328 x.075 = 2,460 megawatts

A Simple Example One River, One Dam No Storage, No Constraints

Developing a Plan for Our Simple System l What is the range of generation? l What is the average generation? l How much generation can we guarantee (year after year)? l What can we do to increase the amount of guaranteed generation?

Statistics for Our System Minimum Runoff Volume 20 Maf Minimum Generation 2,000 aMW Maximum Runoff Volume 100 Maf Maximum Generation 10,000 aMW Average Runoff Volume 60 Maf Average Generation 6,000 aMW Guaranteed Energy 2,000 aMW

Improving Our Simple System by adding 20 Maf of Storage l What is the range of generation? l What is the average generation? l How much generation can we guarantee (year after year)?

Our Modified System When storage is full: minimum generation 4,000 aMW average generation 8,000 maximum generation12,000 When storage is half full: minimum generation 3,000 aMW average generation 7,000 maximum generation11,000

Guaranteed generation depends on how much water is in the reservoir Guaranteed Generation: Condition 1 (full)4,000 aMW Condition 2 (half full)3,000 aMW Condition 3 (empty)2,000 aMW

Improving Our System by Taking Some Chances

Guaranteed Generation can be Increased if Contingency Actions are in Place l 95 % of the time the runoff volume is at least 30 Maf l Contract with a customer to drop load in case of low water in return for better price l This action effectively increases the guaranteed generation by 1,000 aMW

Monthly Distribution of Demand and Generation

Generation from Flow

Shape of Demand

Critical Period Planning l Required by the Pacific NW Coordination Agreement l Portion of the historical water record that produces the least amount of energy (namely the driest conditions) l Reservoirs are drafted from full to empty l Stored water is used to maximize the generation while matching the monthly shape of demand l Results in the Firm Energy Load Carrying Capability (FELCC)

Guaranteed Generation No Storage Surplus

Guaranteed Generation With Storage

Shape of Electricity Prices Compared to the Shape of NW Demand

Developing Operating Guidelines for the Hydroelectric System

Rule Curves l Rule curves are simply elevations at each reservoir that help guide the operation (i.e. drafting or filling) l Rule curves specify the highest and the lowest elevation that a reservoir should be operated to in order to stay within the planning objective l Intermediate rule curves help determine which projects release water first when energy is needed

Rule Curves l Flood Control – defines the drawdown required to assure adequate space to store the anticipated runoff without causing downstream flooding (Maximum Elevation). l Critical Rule Curve – defines how deep a reservoir can be drafted in order to meet the firm energy requirements during the poorest water conditions on record (Minimum Elevation).

Rule Curves l Assured Refill Curve – represents the elevation from which the reservoir could refill given the water conditions that occurred in l Variable Refill Curve (Energy Content Curve) – represents the elevation from which the reservoir could refill given current water conditions.

Rule Curves l Actual Energy Regulation (AER) – defines how deep a reservoir can be drafted in order to meet the firm energy requirements during the current water conditions. l Proportional Draft Point (PDP) – same as the AER above.

Rule Curves Minimum Content Maximum Content

Value of Water in Storage

How the Model Works

General Methodology l Starting with the most upstream reservoir, draft (or fill) each dam to its Variable Refill Curve l Check for constraint violations l Calculate total generation l If generation equals desired amount, we’re done l If generation is less than desired, proportionally draft l If generation is greater than desired, proportionally fill

Calculating the Desired Amount of Hydro Energy l Start with NW firm demand l Subtract (or add) firm contracts (i.e. exports and imports) l Subtract the expected thermal operation l Subtract generation from miscellaneous resources and small hydro l Yields a residual demand that must be served by the hydro system

Non-Power Constraints l Physical limits (i.e. top & bottom of dam) l Maximum flow due to channel restriction l Maximum elevation for flood control l Maximum flow due to rate of draft limit l Operational minimum & maximum flow rate l Operational minimum elevation l Water budget flow target l Spill level

GENESYS Northwest l A PC based program, incorporating the HYDROSIM algorithms l Performs stochastic (probabilistic) studies l Dynamically simulates the interaction of hydro, thermal and out-of-region resources l Identifies potential reliability shortfalls, both long-term (energy deficiencies) and short- term (peaking or capacity problems) l Assesses changes in the physical operation of the hydro system