Download RETScreen Software Online User Manual

RETScreen® Software Online User Manual
A value of 95% represents the efficiency of most generators used for small hydro plants. This
value should be reduced to 93% for plants that require a gearbox (based on information provided
by a turbine manufacturer).
Transformer losses
The user enters a value corresponding to the estimated transformer losses (%) at plant capacity.
This value is used in combination with the gross head, design flow and the various
efficiencies/losses to calculate the plant capacity. Transformer losses are typically minor. A
value of 1% is appropriate as an estimate of transformer losses.
A transformer is generally required to match the voltage of the generator with that of the
transmission line or distribution system to which it is connected.
Parasitic electricity losses
The user enters a value which represents the estimated equivalent parasitic electricity losses (%)
of the system. This value is used in combination with the gross head, design flow and the various
efficiencies/losses to calculate the plant capacity.
Some of the energy generated by a small hydro plant is used by the plant itself for auxiliary
equipment (e.g. shut-off valves, by-pass gates, protection and control systems, etc.) lighting,
heating, etc. For small hydro, parasitic electricity losses are typically minimal. Parasitic
electricity losses can range from 1 to 3%. A value of 2% is appropriate for most small hydro
plants.
Annual downtime losses
The user enters a value to represent the estimated percentage of time that the small hydro plant
will have to be shut down in order to carry out routine and emergency maintenance. This value is
one of the factors used to calculate the available annual energy production of the small hydro
plant.
A value of 4% represents approximately 15 days of downtime (assuming 100% capacity factor)
and is an appropriate value for most small hydro plants. For small hydro plants located in regions
where increased maintenance requirements are anticipated (e.g. due to ice problems), more
downtime should be anticipated and a higher value (e.g. 6%) should be used.
Annual Energy Production
Items associated with calculating the annual energy production of a small hydro project are
detailed below.
HYDRO.14