FAQs

To determine the potential of your water mill, you must evaluate several key parameters that influence hydraulic power production:

1. Stream flow (Q)

Flow rate is the amount of water that passes through a cross section of the stream per unit time. It is usually measured in cubic meters per second (m³/s).

2. Drop height (H)

The head is the difference in height between the water level at the entrance to the mill and the level at the outlet. It is generally measured in meters (m).

3. System efficiency (η)

The overall efficiency takes into account mechanical, hydraulic and electrical losses in the system. This factor depends on the efficiency of the different components of the mill and is typically between 0.5 and 0.9 for small installations.

In order to know the flow rate at a given time on your mill, you can measure the flow rate in several ways:

• Flotation method : Measure the time it takes a floating object to travel a known distance and estimate the cross-sectional area.

• Speed and section measurement : Measure the flow speed and surface area, using a current meter for example.

• Weir or spillway : Use a calibrated structure to measure flow.

Generally speaking, it is preferable to use a measuring station if available on your watercourse by going to the site: https://www.hydro.eaufrance.fr/rechercher/entites-hydrometriques

A complete hydrological study will be necessary to refine the flow available at each time of the year at your water mill.

The gross head is the difference in height between the water level at the entrance to the mill and the level at the outlet. It is generally measured in meters (m).

In order to know the net head of fall, it is necessary to model the pressure losses in the different hydraulic components of the system.

Electric power (Pelec) can be calculated using the following formula: Pelec = η × ρ × g × Q × H where:

• P is the power in watts (W),

• η is the overall efficiency of the system (hydraulic, mechanical and electrical) which depends on the efficiency of the different components of the mill and is typically between 0.5 and 0.9 for small installations.

• ρ is the density of water (approximately 1000 kg/m³),

• g is the acceleration due to gravity (9.81 m/s²),

• Q is the flow rate of the watercourse in m³/s,

• H is the net fall height in meters (m).

The average production of a water mill can vary considerably depending on several factors, such as stream flow, head, mill efficiency and the technology used.

To give an order of magnitude, a water mill producing 20 kW can supply around 18 homes with electricity. This estimate obviously varies depending on local conditions, mill output and household consumption.

For a more precise assessment, it is advisable to carry out a feasibility study to take into account the specific parameters of your site and the technological solutions that could correspond.

Moulins Demain is not an equipment manufacturer. Thus, depending on the situation of your site and its characteristics, we determine which existing technological solutions on the market could be suitable, and what this implies in terms of developments to be carried out, costs and associated income.

We then support you until the implementation of your project.