Hydroelectric Power Plant Simulator
Dam, penstock, surge tank, turbine & generator — animated in 2D & 3D • Explore • Practice • Quiz
Display Controls
Simulated time: —
Control room log
Hydropower problems
Answers within 1 % are marked correct (0.5 % where the arithmetic is exact). Every number you need is in the question; use g = 9.81 m/s² and ρ = 1000 kg/m³.
1 Overview
The simulator shows how a hydroelectric power plant works, part by part, rather than only how to calculate it. It contains five plants in teaching order: a simple plant that shows the energy chain; three plants classified by head — a low-head run-of-river barrage with a Kaplan turbine, a medium-head dam-toe storage plant with a Francis turbine and a high-head diversion plant with a tunnel, surge tank and Pelton wheel; and a pumped-storage plant with a reversible pump-turbine.
Every plant is drawn three ways from one geometry: the plant section, a unit close-up of the turbine and generator, and an operable 3D model. A live model runs underneath: reservoir and tailwater levels, flow in the tunnel and penstock, the surge tank, water hammer, the governor, the generator speed, synchronising and the spillway.
2 Choosing a plant
Above the canvas, the three numbered buttons are the families. 1 — Start here shows the whole energy chain on a small plant. 2 — Plants by head opens a row with the low-, medium- and high-head plants. 3 — Energy storage is the pumped-storage plant. The page address remembers the plant (for example #highhead), so a link opens straight to it.
3 The plant section
The section is drawn with the vertical scale true and the horizontal lengths shortened (the real tunnel and penstock lengths are printed under the title). Water moves through the intake, tunnel, surge tank, penstock, turbine and draft tube as particles whose speed follows the flow. The orange dashed line is the energy line and the green dashed line the hydraulic grade line: they fall with friction along the conduit, swing with the surge tank, and jump up at the turbine during water hammer. Yellow arrows mark the gross head; triangles mark the reservoir and tailwater levels against FRL and MDDL.
Under the section, Detail A shows the turbine from above (spiral casing, stay vanes, wicket gates opening and closing, the runner turning; for the Pelton, the nozzles, spears, jets and deflectors). The trend plots power, speed, gate opening, turbine head and the surge-tank level; the energy flow bar shows where the water power goes. Click Detail A to open the unit close-up. Click any label for a description of the part.
4 The unit close-up
A vertical section through the generating unit: spiral casing (with the flow into and out of the page marked ⊗ and ⊙), stay vanes, wicket gates, servomotor and regulating ring, head cover, runner, draft tube cone and elbow, turbine guide bearing, shaft, generator stator and rotor poles, thrust bearing, exciter and brakes — or, for the Pelton, the housing, distributor, nozzles, spears and deflectors. The scale bar is one runner diameter.
5 The 3D model
On a computer or tablet the plant opens in 3D; on a phone it opens in 2D, and the view switch changes it at any time (the page remembers your choice). Drag to turn, pinch or Ctrl + scroll to zoom, right-drag or two-finger drag to pan. Cutaway removes the near half of the dam, conduits and powerhouse so you can see the water and the machine inside; Powerhouse flies the camera to the unit. Click any part for its card.
6 How it works — the guided tour
Press 🎓 How it works for a step-by-step walk through the plant. Each step lights up the parts it describes and dims the rest. It plays by itself; use ⏮ ⏭ (or the arrow keys) to step, ❙❙ to pause and ✕ or Esc to close. It works in 2D and 3D.
7 Running the plant
Start unit runs the real start-up sequence: open the inlet valve, crack the gates, run up, excite, synchronise (watch the synchroscope) and close the breaker. Stop unit unloads, opens the breaker, closes the gates and brakes the unit. Trip breaker throws off the load: the unit overspeeds, the governor shuts the gates and the penstock pressure rises.
On the Grid the power setpoint sets the output; on an Island the unit alone feeds a town and its governor holds the frequency. River inflow fills or drains the reservoir, and the spillway gates pass the surplus. The scenarios set up classic lessons; each picks a sensible time speed (governing happens in seconds, a reservoir changes over days).
8 Readouts and the specification card
Twelve tiles show electrical output, net head, turbine flow, turbine (or pump) efficiency, gate opening, speed and frequency, turbine inlet pressure, reservoir level, surge-tank or tailwater level, water-to-wire efficiency, energy generated and spillway flow. The specification card computes the synchronous speed from the poles and frequency, the specific speed, the penstock water starting time and the surge-tank period for the plant on screen.
9 Explore, Practice and Quiz
Explore has seven topic tabs: Basics, Plant layout & parts, Classification, Turbines, Water hammer & surge, Operation & control, and Pumped storage & economics, with worked examples. Practice gives endless problems of fourteen kinds — power, flow, net head, synchronous speed, poles, specific speed, Joukowsky and gradual water hammer, surge-tank period, Pelton wheel diameter, annual energy, stored energy, cavitation setting and water starting time. Quiz asks five questions drawn from a pool of thirty, with the options shuffled.
10 SI and Imperial
The Units switch changes levels and heads (m ↔ ft), flows (m³/s ↔ cfs) and pressure (bar ↔ psi). Power stays in MW and energy in MWh in both, as the industry quotes them. Your choice is remembered across the site. The 50 Hz | 60 Hz switch changes the grid frequency and so the synchronous speed of every machine.
11 Tips
Run Load rejection on the dam-toe plant and then on the high-head plant: the Francis unit overspeeds by about 40 % while the Pelton barely moves, because its deflectors cut the jets in two seconds while the needles close slowly. On the high-head plant, watch the surge tank keep oscillating for several minutes after a trip (set the time speed to ×10). Try Flood on the run-of-river plant: the river brings more water than ever, yet the output falls as the tailwater rises.
How a Hydroelectric Power Plant Works — Interactive Simulation
A hydroelectric power plant turns the potential energy of water stored at a height into electricity. A dam holds the water in a reservoir; the water enters an intake, falls through a penstock and reaches the turbine under pressure; in the turbine it speeds up and drives the runner, which turns the generator; and it leaves through the draft tube and tailrace back to the river. This simulator shows all of it moving, for the four kinds of plant every power-plant course teaches, in a section, a close-up of the generating unit and a 3D model you can turn and cut open.
The Hydropower Formula
The electrical output of a hydro plant is P = ρ·g·Q·Hn·η: the density of water (1000 kg/m³), gravity (9.81 m/s²), the discharge Q, the net head Hn and the overall efficiency η (turbine × generator). The dam-toe plant in the simulator uses 120 m³/s under a net head of 95 m with a turbine efficiency of 91.5 % and a generator efficiency of 98 %: P = 1000 × 9.81 × 120 × 95 × 0.915 × 0.98 = 100.3 MW. The net head is the gross head — headwater level minus tailwater level — less the friction losses in the intake, tunnel and penstock, hf = f·(L/D)·V²/2g.
Parts of a Hydroelectric Power Plant
| Part | Function |
|---|---|
| Reservoir | Stores water and therefore energy, E = ρgVH |
| Dam | Raises the water level and holds it back |
| Spillway | Passes flood water safely, Q = C·L·h1.5 |
| Intake, trash rack & gate | Admits clean water below the minimum drawdown level |
| Headrace tunnel | Carries water through the hill to the surge tank |
| Surge tank | Absorbs flow changes; protects the tunnel from water hammer |
| Penstock | Steel pressure pipe down to the turbine |
| Spiral casing & wicket gates | Distribute the water round the runner and control the flow |
| Turbine runner | Converts the water energy into shaft power |
| Generator | Converts shaft power into electricity, f = p·N/120 |
| Draft tube & tailrace | Recover the exit velocity and return the water to the river |
| Transformer & switchyard | Raise the voltage and connect to the grid |
Classification by Head — and Which Turbine to Use
The head decides the flow needed for a given power, and so the shape of the turbine. Engineers sum this up in the specific speed, Ns = N·√P / H5/4 (N in rpm, P in kW, H in m). The four plants in the simulator are designed in the ranges below, and their specification cards compute Ns live.
| Plant in the simulator | Head | Turbine | Speed | Specific speed Ns |
|---|---|---|---|---|
| Run-of-river barrage | Low, 12 m | Kaplan (axial reaction) | 83.3 rpm, 72 poles | 646 |
| Dam-toe storage plant | Medium, 95 m | Francis (mixed-flow reaction) | 166.7 rpm, 36 poles | 178 |
| High-head diversion plant | High, 430 m | Pelton, 6 jets (impulse) | 375 rpm, 16 poles | 25 per jet |
| Pumped-storage plant | High, 315 m | Francis pump-turbine | 333.3 rpm, 18 poles | 126 |
Speeds are at 50 Hz; at 60 Hz each machine runs 20 % faster. As a rule of thumb, Pelton wheels have Ns of about 10–35 per jet, Francis turbines about 60–300 and Kaplan turbines about 300–1000.
Run-of-River, Storage, Diversion and Pumped-Storage Plants
A run-of-river plant has little storage and uses the river as it comes; its powerhouse is often built into a low barrage. A storage (impoundment) plant carries water from the wet season to the dry one and can run hard at the evening peak. A diversion plant takes the water from a low weir through a long tunnel and drops it to a powerhouse far below. A pumped-storage plant pumps water up to an upper reservoir when power is plentiful and generates with it at the peak, returning about 75–80 % of the energy — it is an energy store, not an energy source.
Water Hammer and the Surge Tank
Water in a long pipe is heavy and cannot be stopped at once. Closing the turbine gates instantly would raise the pressure by the Joukowsky head Δh = a·ΔV/g: with a wave speed of 1100 m/s and a velocity of 5 m/s that is 561 m, six times the static head of the dam-toe plant. Governors therefore close slowly; closed over 8 seconds, the 180 m penstock sees only about ρLV/t = 1.125 bar (11.5 m). A long headrace tunnel needs a surge tank: on the high-head plant the tunnel water surges up the shaft after a trip and oscillates with a period T = 2π√(L·As/g·At) = 423 s and an amplitude of up to about 11.6 m. The simulator draws the energy and hydraulic grade lines so you can see both effects.
Governor, Synchronising and Load Rejection
A hydro unit starts in a few minutes: the inlet valve opens, the wicket gates crack open, the unit runs up, the excitation is switched on and the unit is synchronised — voltage, frequency and phase matched to the grid — before the breaker closes. On the grid the governor sets the gate opening for the power wanted; on an island it holds the frequency. If the breaker trips at full load the unit overspeeds until the gates close; a Pelton wheel avoids this with jet deflectors that cut the jets in about two seconds while the needles close slowly.
Frequently Asked Questions
How does a hydroelectric power plant work?
A dam stores water in a reservoir at a height. The water flows through an intake and down a penstock, where its potential energy becomes pressure. In the turbine the water speeds up and turns the runner, and the shaft turns the generator, which produces electricity. The water then returns to the river through the draft tube and tailrace. The output is P = ρgQHη: water density times gravity times flow times net head times efficiency.
What are the main parts of a hydroelectric power plant?
The main parts are the reservoir, the dam, the spillway, the intake with its trash rack and gate, the headrace tunnel or canal, the surge tank or forebay, the penstock, the main inlet valve, the turbine with its spiral casing, wicket gates and runner, the generator, the draft tube and tailrace, and the transformer and switchyard that connect the plant to the grid.
What is the function of a surge tank in a hydro plant?
A surge tank is an open shaft between a long headrace tunnel and the penstock. When the turbine gates close, the water in the tunnel runs on into the tank and its level rises, instead of causing water hammer in the tunnel. When the gates open, the tank supplies water while the tunnel flow speeds up. The level then oscillates slowly with a period T = 2π√(L·As / g·At).
Which turbine is used for high, medium and low head?
Pelton wheels (impulse turbines) are used for high heads, above about 300 m. Francis turbines (mixed-flow reaction turbines) are used for medium heads of about 30 to 300 m, and up to about 700 m. Kaplan and propeller turbines (axial-flow reaction turbines) are used for low heads below about 30 m with large flows. The choice is made by the specific speed Ns = N√P / H^1.25.
How does a pumped storage plant work?
A pumped storage plant has an upper and a lower reservoir. When electricity is plentiful and cheap, a reversible pump-turbine driven by its motor-generator pumps water up to the upper reservoir. When electricity is needed, the water flows back down through the same machine running as a turbine. About 75 to 80 percent of the energy used for pumping is returned, so it is an energy store rather than a source of energy.
Who Uses This Simulator?
Mechanical, civil and electrical engineering students in power-plant engineering, fluid machinery and renewable-energy courses; diploma and vocational learners; school students meeting renewable energy for the first time; teachers who need an animated plant for the classroom; and anyone who has wondered what happens inside a dam.
Selected References
P. K. Nag, Power Plant Engineering; R. K. Rajput, Fluid Mechanics and Hydraulic Machines; M. M. Dandekar and K. N. Sharma, Water Power Engineering; C. C. Warnick, Hydropower Engineering; IEEE Std 1207, Guide for the Application of Turbine Governing Systems for Hydroelectric Generating Units; US Bureau of Reclamation, Selecting Hydraulic Reaction Turbines (Engineering Monograph 20).
Explore Related Simulators
Test Pelton, Francis and Kaplan runners on a test rig in the Hydraulic Turbine simulator, work out penstock friction in the Pipe Flow simulator and the energy equation in Bernoulli’s Principle. See how the generator makes its voltage in the AC Generator simulator and how the step-up transformer works in the Transformer simulator. For the pumping side of pumped storage, try the Centrifugal Pump simulator, and compare with a thermal station in the Steam Boiler and Rankine Cycle simulators.
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