Hydro Power 102

1. Hydro Power 102 The Columbia River is a great natural resource for the Pacific Northwest, providing transportation, recreation, water for irrigation, power generation and protection against flooding. It also contains one of the world’s largest salmon populations. Over the years, however, the number of salmon and steelhead has decreased due to changes in the environment. The region is aggressively trying to restore salmon and steelhead populations. The NW Power Planning Council, the National Marine Fisheries Service in conjunction with federal agencies and the Indian tribes and states have all developed comprehensive recovery plans. This course presents an explanation of the planning for and operation of the multiple-use dams of the Columbia River. The first part of the course provided a basic background for the hydroelectric system. This second part discusses in more detail how the operation of the hydro system is planned for. It identifies the computer models that are used in the planning process and describes how they work. The Columbia River is a great natural resource for the Pacific Northwest, providing transportation, recreation, water for irrigation, power generation and protection against flooding. It also contains one of the world’s largest salmon populations. Over the years, however, the number of salmon and steelhead has decreased due to changes in the environment. The region is aggressively trying to restore salmon and steelhead populations. The NW Power Planning Council, the National Marine Fisheries Service in conjunction with federal agencies and the Indian tribes and states have all developed comprehensive recovery plans. This course presents an explanation of the planning for and operation of the multiple-use dams of the Columbia River. The first part of the course provided a basic background for the hydroelectric system. This second part discusses in more detail how the operation of the hydro system is planned for. It identifies the computer models that are used in the planning process and describes how they work.

2. Hydroelectric Modelsin theNorthwest

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

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

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

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

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

8. Modeling the Hydroelectric System

9. Tapping the Power of the RiverA Few Definitions Potential Energy = stored energy proportional to the height above ground Kinetic Energy = energy of motion proportional to the velocity Gravitational potential energy is stored energy, like energy in a battery. In this case, an object with mass, at a certain height above the ground, has potential energy equal to its mass times the height times the gravitational acceleration. The potential energy of the object is converted to kinetic energy (or the energy of motion) by dropping it. The kinetic energy is equal to one-half the mass times the velocity squared. Gravitational potential energy is stored energy, like energy in a battery. In this case, an object with mass, at a certain height above the ground, has potential energy equal to its mass times the height times the gravitational acceleration. The potential energy of the object is converted to kinetic energy (or the energy of motion) by dropping it. The kinetic energy is equal to one-half the mass times the velocity squared.

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

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

12. Tapping the Power of the River 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 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

13. A Simple Example One River, One DamNo Storage, No Constraints Let’s try a simple example. We have one river, one dam and no storage. Generation from our turbine is a linear function of the runoff volume as illustrated in the chart above. In a dry year, when the runoff is only 20 maf, the generation is 2,000 average megawatts. In a wet year, when the runoff is 100 maf, the generation is 10,000 average megawatts. Let’s try a simple example. We have one river, one dam and no storage. Generation from our turbine is a linear function of the runoff volume as illustrated in the chart above. In a dry year, when the runoff is only 20 maf, the generation is 2,000 average megawatts. In a wet year, when the runoff is 100 maf, the generation is 10,000 average megawatts.

14. A Simple Example One River, One DamNo Storage, No Constraints It is also important to know the distribution of runoff. In our simple example, we will assume a normal distribution as illustrated above. Average runoff volume is 60 maf.It is also important to know the distribution of runoff. In our simple example, we will assume a normal distribution as illustrated above. Average runoff volume is 60 maf.

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

16. 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

17. Improving Our Simple Systemby adding 20 Maf of Storage What is the range of generation? What is the average generation? How much generation can we guarantee (year after year)? By adding storage capability, we can increase our amount of guaranteed energy. Let’s go through a simple example.By adding storage capability, we can increase our amount of guaranteed energy. Let’s go through a simple example.

18. Our Modified System When storage is full: minimum generation 4,000 aMW average generation 8,000 maximum generation 12,000 When storage is half full: minimum generation 3,000 aMW average generation 7,000 maximum generation 11,000 When the storage is full, the minimum generation is 4,000 aMW. When the storage is half full, the minimum generation is 3,000 aMW. And, when the storage is empty, like before, the minimum generation is only 2,000 aMW. So, the amount of minimum generation (or guaranteed generation) is dependent on the contents of our storage at the beginning of each year. When the storage is full, the minimum generation is 4,000 aMW. When the storage is half full, the minimum generation is 3,000 aMW. And, when the storage is empty, like before, the minimum generation is only 2,000 aMW. So, the amount of minimum generation (or guaranteed generation) is dependent on the contents of our storage at the beginning of each year.

19. 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 This is a summary of the guaranteed generation for our simple model. Just as in real life, the guaranteed generation (or FELCC in real life) depends on how full the reservoirs are at the beginning of the drafting season (usually September).This is a summary of the guaranteed generation for our simple model. Just as in real life, the guaranteed generation (or FELCC in real life) depends on how full the reservoirs are at the beginning of the drafting season (usually September).

20. Improving Our Systemby Taking Some Chances In our simple example, runoff volumes of 30 maf or less occur approximately 5 percent of the time. Conversely, we can expect to get 30 maf 95 percent of the time.In our simple example, runoff volumes of 30 maf or less occur approximately 5 percent of the time. Conversely, we can expect to get 30 maf 95 percent of the time.

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

22. Monthly DistributionofDemand and Generation

23. Generation from Flow This chart illustrates the monthly distribution of flows in our simple system. Flows are very low during winter, when part of the precipitation falls as snow. Flows are very high in spring when warm weather melts the snow and adds to river flows. With no storage capability, we have no mechanism to change the shape of this pattern.This chart illustrates the monthly distribution of flows in our simple system. Flows are very low during winter, when part of the precipitation falls as snow. Flows are very high in spring when warm weather melts the snow and adds to river flows. With no storage capability, we have no mechanism to change the shape of this pattern.

24. Shape of Demand This chart illustrates a simple demand pattern for our example. It somewhat mimics the Northwest in that the peak demand is in the winter and the lowest demand is in spring. Let’s assume, for this example, that we cannot alter the shape of demand. (Of course, conservation and other demand-side programs are very important, but for this example we will temporarily ignore them.)This chart illustrates a simple demand pattern for our example. It somewhat mimics the Northwest in that the peak demand is in the winter and the lowest demand is in spring. Let’s assume, for this example, that we cannot alter the shape of demand. (Of course, conservation and other demand-side programs are very important, but for this example we will temporarily ignore them.)

25. Critical Period Planning Required by the Pacific NW Coordination Agreement Portion of the historical water record that produces the least amount of energy (namely the driest conditions) Reservoirs are drafted from full to empty Stored water is used to maximize the generation while matching the monthly shape of demand Results in the Firm Energy Load Carrying Capability (FELCC) Because we have no storage, we are bound to plan the operation of our hydro system using critical water. In other words, how much “firm” energy can we provide, given that we have no storage?Because we have no storage, we are bound to plan the operation of our hydro system using critical water. In other words, how much “firm” energy can we provide, given that we have no storage?

26. Guaranteed GenerationNo Storage The green line in this chart represents the generation available from the river. Remember that we cannot change its shape or move it up or down. The red line reflects the monthly shape of demand. We have assumed that we cannot change its shape. To determine the minimum amount of energy that we can guarantee, we can slide the red line up and down vertically until each part of the red line is either at or below the green line. At this point, this determines the amount of “firm” energy that we can produce. Notice that in the fall and spring, large amounts of “nonfirm” energy are available. The green line in this chart represents the generation available from the river. Remember that we cannot change its shape or move it up or down. The red line reflects the monthly shape of demand. We have assumed that we cannot change its shape. To determine the minimum amount of energy that we can guarantee, we can slide the red line up and down vertically until each part of the red line is either at or below the green line. At this point, this determines the amount of “firm” energy that we can produce. Notice that in the fall and spring, large amounts of “nonfirm” energy are available.

27. Guaranteed GenerationWith Storage By adding storage, we can reshape the green line. We can store some of the spring runoff in our reservoir and hold it until winter, when we release it to generate more power. The original flow curve (dashed green line) has been “flattened” somewhat, and its lowest point (winter) has gone up from 8,000 to 9,000 average megawatts. In terms of firm energy, we can now slide the red line up to touch the new green line, which gives us an additional 1,000 average megawatts. By adding enough storage to change the flows we have gained 1,000 average megawatts of firm energy and we have lost 1,000 average megawatts of nonfirm energy. In our simple example, we have no spill or efficiency losses.By adding storage, we can reshape the green line. We can store some of the spring runoff in our reservoir and hold it until winter, when we release it to generate more power. The original flow curve (dashed green line) has been “flattened” somewhat, and its lowest point (winter) has gone up from 8,000 to 9,000 average megawatts. In terms of firm energy, we can now slide the red line up to touch the new green line, which gives us an additional 1,000 average megawatts. By adding enough storage to change the flows we have gained 1,000 average megawatts of firm energy and we have lost 1,000 average megawatts of nonfirm energy. In our simple example, we have no spill or efficiency losses.

28. Shape of Electricity PricesCompared to the Shape of NW Demand The “real” shape of Northwest demand looks more like the red curve in this chart. It does peak in winter and dips in the spring like in our example. Hydro planning is designed to maximize the power production while conforming to all non-power constraints and maintaining the “shape” of demand in the northwest. Overlaid on the demand curve is the shape of west-coast electricity prices. We observe a peak in prices in winter that coincides with our demand peak but we also observe a higher peak in prices in July and August when northwest demand is relatively low. The summer peak in price reflects the large summer demand of the southwest. The “real” shape of Northwest demand looks more like the red curve in this chart. It does peak in winter and dips in the spring like in our example. Hydro planning is designed to maximize the power production while conforming to all non-power constraints and maintaining the “shape” of demand in the northwest. Overlaid on the demand curve is the shape of west-coast electricity prices. We observe a peak in prices in winter that coincides with our demand peak but we also observe a higher peak in prices in July and August when northwest demand is relatively low. The summer peak in price reflects the large summer demand of the southwest.

29. Developing Operating Guidelinesfor theHydroelectric System

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

31. Rule Curves Flood Control defines the drawdown required to assure adequate space to store the anticipated runoff without causing downstream flooding (Maximum Elevation). 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).

32. Rule Curves Assured Refill Curve represents the elevation from which the reservoir could refill given the water conditions that occurred in 1931. Variable Refill Curve (Energy Content Curve) represents the elevation from which the reservoir could refill given current water conditions.

33. Rule Curves 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. Proportional Draft Point (PDP) same as the AER above.

34. Rule Curves This particular graph reflects the rule curves for Libby Dam for water year 1945. Libby has a fixed December flood control elevation of 2,411 feet for all years and all water conditions. In a very wet year, the flood control curve (red line) would dip below the December limit of 2,411 to nearly empty by April. The yellow dashed line represents the actual energy regulation. It differs from the refill curve because it contains some of the fish constraints. One constraint attempts to have Libby as full as possible by the end of June so that more water will be available for summer flow augmentation. A second constraint allows Libby to be drafted as much as 20 feet down from full by the end of August to help achieve river flow targets in the summer. This particular graph reflects the rule curves for Libby Dam for water year 1945. Libby has a fixed December flood control elevation of 2,411 feet for all years and all water conditions. In a very wet year, the flood control curve (red line) would dip below the December limit of 2,411 to nearly empty by April. The yellow dashed line represents the actual energy regulation. It differs from the refill curve because it contains some of the fish constraints. One constraint attempts to have Libby as full as possible by the end of June so that more water will be available for summer flow augmentation. A second constraint allows Libby to be drafted as much as 20 feet down from full by the end of August to help achieve river flow targets in the summer.

35. Value of Water in Storage This chart illustrates the use of rule curves to guide the operation of the hydroelectric projects more graphically. For any given month, the rule curve elevations can be “painted” onto the dam itself. The water behind the dam can then be separated into volumes or “blocks.” Water above the flood control curve is very cheap because it would have to be evacuated even in the absence of a market for that electricity. Water below the critical rule curve is very, very expensive and can only be used in emergency situations and only for a short time. The water must then be replaced as soon as possible. Water in the intermediate blocks becomes more valuable the deeper the project is drafted. Each month, every dam is drafted to its refill curve and the corresponding generation is calculated. If more generation from the hydroelectric system is desired, every dam is further drafted to its actual energy regulation curve. If this is still insufficient then all projects are again further drafted to their respective critical rule curves. To “zero in” on the desired amount of hydroelectric energy, the system is drafted “proportionally” between rule curves. This chart illustrates the use of rule curves to guide the operation of the hydroelectric projects more graphically. For any given month, the rule curve elevations can be “painted” onto the dam itself. The water behind the dam can then be separated into volumes or “blocks.” Water above the flood control curve is very cheap because it would have to be evacuated even in the absence of a market for that electricity. Water below the critical rule curve is very, very expensive and can only be used in emergency situations and only for a short time. The water must then be replaced as soon as possible. Water in the intermediate blocks becomes more valuable the deeper the project is drafted. Each month, every dam is drafted to its refill curve and the corresponding generation is calculated. If more generation from the hydroelectric system is desired, every dam is further drafted to its actual energy regulation curve. If this is still insufficient then all projects are again further drafted to their respective critical rule curves. To “zero in” on the desired amount of hydroelectric energy, the system is drafted “proportionally” between rule curves.

36. How the Model Works

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

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

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

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