FLOWMini AC Hydro Generator
A mini hydro generator that turns household shower water into power for always-on apartment lights.
- Year
- 2022
- Reading
- 03 min
- Figures
- 06
FLOW is a small AC hydro generator that captures energy from household shower water, so Hong Kong apartment complexes can power their always-on lights with clean energy instead of coal and natural gas. A curved-blade waterwheel drives a V-belt and a piston that moves a coil of wire. A five-person team developed it for the Conrad Challenge 2022, in the Energy and Environment category.
- Team
- Jeff Ho
- Yiming “Danny” Huang
- Lucy Lai
- Julie Huang
- Hong Kiu Lui
- Disciplines
- Renewable Energy
- Mechanical Engineering
- Electromagnetism
- Prototyping
- Pitch
- Tools
- CAD / PLA 3D printing / V-belt drive / Copper coil and magnet / Bernoulli’s equation
In densely populated Hong Kong, residential buildings take up 7% of the city’s land — and their lights never go off. Constant illumination keeps residents with varied schedules safe and covers emergencies, but it consumes a great deal of energy, mostly generated from coal and natural gas, and it is a growing bill for property companies as electricity tariffs rise.
Our team’s answer is FLOW, a generator that captures energy from wastewater. Installed in residents’ homes, it uses the water from their showers to power a share of the complex’s lights: clean energy, and long-term savings.
Energy from the shower pipe
The generator converts mechanical energy — the water’s kinetic and gravitational potential energy — into electrical energy. Because its components are small, less energy is lost to gravity and friction, which makes for an efficient generator.
The calculations rest on two modules: the water source and pump, where water first meets the turbine, and the top of the elbow joint pipe, which feeds the showers in each bathroom. The pipes all run through the residential pipe room, which connects to the household’s power supply and switch room.
The magnet measures 6 × 2 × 2 cm; the coil is 4.5 cm across, with a cross-sectional area of 15.9 cm².
Fig. 01FLOW, in orange, mounted on the water pipe in a residential pipe room.
Fig. 02The two calculation modules, 203.2 cm apart.
Fig. 03Bernoulli’s equation, set up for a Hong Kong shower.
FLOW’s technology
- 01
Waterwheel
Captures the movement of the water. Inspired by traditional waterwheels, but with curved blades for higher efficiency.
- 02
V-belt drive
A belt connects two wheels of different sizes, allowing variable speed and power transmission.
- 03
Piston and coil
The piston converts the wheel’s high rotary speed into horizontal movement for the copper wire coil.
Small enough for every apartment
Large hydropower plants are impractical in Hong Kong: water sources are scarce and land is limited. FLOW is small enough to install in individual apartments, and needs no excavation at all.
Hong Kong’s 7 m LED street lamps draw 30 W each and run from dusk to dawn — about 8.5 hours in summer and 10 in winter, or 0.255 kWh and 0.3 kWh a night. Divide what one apartment’s generators produce by that, and each apartment can power 9 to 10 street lights every night. The whole 10-apartment community has only 40 street lights, so the surplus is kept in thermal energy storage beneath each apartment.
27.54 kWh
a day from a collective installation in one apartment complex
90
LED lights powered by that daily output
9–10
street lights each apartment can power every night
40
street lights in the entire 10-apartment community
