beginner

Hydro Power Plant

See how we use water to convert potential energy into electricity.

fluidshydropowerenergy

Generator style

River diversion or low weir — trade height for flow

Site

Serbia/Romania — low head, huge Danube flow (~2.2 GW)

Volume flow Q through turbines (m³/s)

7,200 m³/s

Weir to major river diversion: roughly 10–7,000 m³/s — slide to 0 for drought or blockage

Gross head H_gross (m)

34 m

Total head loss ΣhL (m)

2 m (6 % of gross)

Overall efficiency η

Typical modern utility operation — ~87%

From river to grid

A portion of river flow is diverted through an inlet and forebay, down a penstock to a powerhouse that connects to the grid.

Net head

32 m

Hydraulic power

2,255 MW

Electrical power

1,962 MW

Put it in perspective

How much power is the simulator configured to generate?

Homes

1.6 million

Typical U.S. households
(29 kWh each)

50″ TVs

19.6 million

Sets running at once
(100 W each)

Tesla miles

181.1 million

Model 3 Long Range driving
(0.26 kWh/mi)

How hydro power works

Every hydro plant does the same basic thing: move water from a higher elevation to a lower one. Water at height has gravitational potential energy. As it falls or flows downhill through a pipe or channel, that potential energy becomes kinetic energy — the water moves faster and pushes harder on whatever is in its path.

At the bottom of the drop, the moving water spins the blades of a turbine. The turbine shaft turns a generator, and the generator pushes electrons through the grid. After the turbine, the water exits through a tailrace and rejoins the river or stream at lower elevation. No water is consumed; it is borrowed, briefly, for its energy.

The physics is the same whether the “height” is a 300 m dam or a 5 m backyard penstock. What changes is how much water you can route through the system and how far it falls.

The power formula

Hydraulic power — the rate at which flowing water delivers energy — depends on three things: how much water flows per second, how far vertically it falls, and how dense the water is.

While our simulator assumes water, the formula works for other liquids, too. Adjust accordingly in the land of milk and honey.

Gross head could be something you see in a horror movie. When it comes to hydro power, the gross head ( $H_\text{gross}$ ) is the total vertical drop from the intake, where water enters the system, down to the turbine. It is the full height difference that a dam or nature provides.

Not all of that drop reaches the turbine. Friction in the penstock, clogged screens, bends, and air in the line have the effective of reducing the head. Net head ( $H_\text{net}$ ) is what remains after losses:

H_\text{net} = H_\text{gross} - \sum h_L

where $\sum h_L$ is the total head loss along the path.

Hydraulic power (watts):

P_\text{hyd} = \rho \, g \, Q \, H_\text{net}

Electrical power is hydraulic power times overall efficiency $\eta$ (turbine, generator, gearbox, and wiring losses combined):

P_\text{elec} = \eta \, P_\text{hyd}

Symbol	Meaning	Typical units
$\rho$	Density of water	~1000 kg/m³
$g$	Gravitational acceleration	9.8 m/s²
$Q$	Volume flow through the turbine	m³/s
$H_\text{gross}$	Vertical drop from intake to turbine	m
$\sum h_L$	Head lost to friction, screens, bends, etc.	m
$H_\text{net}$	Head left for the turbine	m
$\eta$	Overall efficiency (flow → wires)	0–1

Notice that power scales linearly with both $Q$ and $H_\text{net}$ . Double the flow or double the drop, and you double the power — if everything else stays the same. There is no separate “dam formula” or “stream formula”; dams and creeks differ in geometry and operating conditions, not in the underlying equation.

Storage dams

Most people picture hydro power as a dam: a wall across a river that backs water into a reservoir. The dam does not create energy; it stores it. Water piled up behind the dam sits higher than the river downstream, so it has potential energy waiting to be used.

A dam plant typically has:

Large gross head — tens to hundreds of meters from reservoir surface to the powerhouse.
Controlled flow — operators open intake gates and release water through penstocks (large pipes or tunnels) when electricity is needed.
Seasonal flexibility — snowmelt and spring rains fill the reservoir; the plant can run through dry months by drawing down stored water.

For a dam, the same formula applies. What makes dams distinctive is not a different equation but a different balance of $Q$ and $H$ : enormous head, with flow chosen by how fast the reservoir is drawn down. Hoover Dam and Jinping-I are extreme examples — hundreds of meters of head — while Grand Ethiopian Renaissance Dam (GERD) shows how a big reservoir on a major river can sustain gigawatts for a region.

In the simulator, pick Storage dam or Grand dam to see the reservoir-and-penstock schematic and explore sites from Kariba to Jinping-I.

Rivers and streams

Not every hydro plant needs a dam. Run-of-river plants divert part of a river through a canal or low weir. Micro hydro systems tap a mountain stream with an intake box and penstock (pipeline) on a hillside. Here the emphasis shifts from stored height to natural flow:

Flow varies with the season — Spring snowmelt can be many times winter flow. A drought can reduce output to near zero.
Head is modest — A weir might raise the water only a few meters. A home creek might drop 5–50 m through a pipe.
Losses matter more — Long penstocks lose head to pipe friction. Intake screens clog with leaves and debris. Air in the line steals effective head. A partially full pipe moves less water than the intake suggests.

Pick Run-of-river for plants like Niagara Falls and Itaipu. These have a modest head and enormous natural flow.

Pick Micro hydro to try the scale of mountain streams and creeks.

Terms worth knowing

Term	What it means
Head	Vertical distance water falls, in meters — not the body part. “100 m of head” means the water surface is 100 m above the turbine. More head → more potential energy per liter.
Gross head	Total drop from intake (where water enters the system) to the turbine.
Net head	Gross head minus losses — what the turbine actually sees.
Intake	Structure where water enters the plant — a gate in a dam face, a screened box in a stream, or a forebay fed by a creek.
Penstock	Pipe or tunnel carrying water from intake down to the powerhouse. Pressure and velocity build as the water descends.
Powerhouse	Building (or shed) housing the turbine and generator.
Tailrace	Channel where water exits after passing through the turbine, returning to the river at lower elevation.
Weir	Low dam or barrier that raises the upstream water level a few meters — common in run-of-river plants.
Forebay	Small settling pool between a stream and the penstock; helps strain debris and smooth flow before the pipe.