Polesio plant

is an indicator of an environmental "saving": the energy produced by a hydroelectric plant results in a saving in the collective consumption of oil. Each barrel is equivalent to 679 kWh. Related entry: CO2 Emissions Avoided.

the bypass system allows the flow to be automatically switched, in about 8 seconds, from the turbine to the existing pressure reduction valve, and prevents the water flow being interrupted even when the plant is not working efficiently. In addition, it avoids any dangerous build up of pressure in the pipeline resulting from the plant being out of order.

Minimum Vital Flow: refers to the minimum quantity of water required, after the uptake for the plant, to ensure that the natural ecological integrity is maintained, with particular reference to the protection of aquatic life. Thus the Minimum Vital Flow should be seen as the residual flow that is capable of guaranteeing, in the short and long term, the protection of the watercourse's natural state.

is an indicator of an environmental "saving": the energy produced by a hydroelectric plant results in a saving in the collective consumption of oil and therefore in CO2 emissions. Each barrel saved is equivalent to 360 kg of CO2 emissions avoided. Related entry: Barrels of Oils Saved.

 

The Francis water turbine is the most commonly used type of turbine. The runner is used on watercourses with differences in height ranging from 10 m to 300-400 m and with flow rates from 2-3 m³/s through to 40-50 m³/s. The turbine allows the water to be returned with back-pressure and avoids the entry of any possible foreign matter (further ensuring hygienic conditions). The installation of these turbines allows the use of only excess pressure, returning the water with the right back-pressure required to comfortably reach the supply points without the need for potentially expensive interventions to raise the water.

means the impact the structure and its construction has on the environment: it could be none when the plant is placed within a pre-existing aqueduct structure. It is minimized when a structure is built from concrete.

Is a hydraulic reaction turbine that is used to exploit watercourses with small differences in height, up to 20-30 m, but with high flow rates, of 20-30 m³/s and up. It is essentially a propeller, with runner blades that can be adjusted depending on the water flow, thus allowing efficiency to stay high even with only 20-30% of the nominal water flow. Upon discharge, as with the Francis turbine, it is possible to recover energy thanks to a diffuser.

is a indicator of hypothetical environmental impact: if the energy produced by a plant went directly to domestic use by the general public, there would be a number of families consuming "green" energy. The number is calculated on the basis of the average consumption of an Italian nuclear family, ie 2,000 kWh/year.

The measurement of the average number of hours the plant is actually operational (considering that in a year there are 365 x 24 hours, ie 8760 hours) is an indicator of the plants efficiency: in plants on aqueducts it depends on endogenous factors (interruptions for maintenance) and exogenous factors (availability of water resources and the particular needs of the water operator).

Pelton turbines are currently the most efficient turbines. They are used for large heads (more than 15 m, usually 300-1,400 m) with low flow rates (less than 50 m m³/s)

The flow rate is the quantity of fluid (water) that passes a section of pipeline or watercourse within a certain unit of time. It is measured as the volume or mass divided by the unit of time. Flow rate varies considerably with the seasons, and the average annual figure is usually used. It is a key factor in determining which type of turbine to use.

or nominal capacity. Indicates the maximum electrical output that could be produced by transforming hydraulic energy to electrical energy. It is expressed in kilowatts or kilovolt-amperes (kVA)

Indicates the annual electricity actually produced, based on the annual average of recent years. It is measured in kWh (or GWh, 1 GWh = 1,000 kWh) per year.

The relationship between the mechanical energy used and the electrical energy produced is called hydraulic efficiency, in water turbines it can reach over 85%.

The hydraulic head is the vertical difference between levels, which determines the velocity of the water and translates into hydrodynamic pressure at the level where the turbine is placed. It is a key factor in determining which type of turbine to use.

By remote control, we mean a supervisory system that, via an appropriate communications network, manages and controls automatic remote systems. In Hydrowatt's case, the remote control consists of monitoring the hydroelectric plants (and all the hydraulic parameters) using a SCADA system (Supervisory Control And Data Acquisition) that communicates with the equipment in the plant (PLC, PC, electricity meters, anti-intruder systems, CCTV, process and electrical network scanners, etc) via a satellite system based communications network. This ensures continuous control of the plants and high levels of reliability and service continuity, as well as high levels of safety.

is a machine that converts mechanical energy into electrical energy. The simplest type of turbine essentially consists of two parts: the stator, the stationary part (that generates electricity); and the rotor or runner. If the turbine converts mechanical energy from a fluid you have a fluid turbine. The moving fluid acts on the blades of the runner, causing it to rotate and thereby transferring mechanical energy to the runner. The first examples of fluid turbines were windmills and waterwheels.

indicates how the hydroelectric plant "returns" the water used: at atmospheric pressure when the pressure of the outflow is the same as atmospheric pressure and is near storage tanks; with back-pressure, when it is necessary to restore some bars of pressure in order to be able to supply some uses at a level above the level of the plant site.