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TURBINE SELECTION
On 17th August 1856 we received our first order for a water turbine. It produced mechanical power to drive agricultural
equipment. Farmers at the time required power – power which they used to cut wood and thresh corn. Advancements in
technology reduced the demand for water turbines to provide this power but today we still find ourselves supplying water
turbines all over the world.
Our role as a designer and supplier has, by consequence, changed. Where we were once commissioned to supply equipment
to meet power and torque demands of mechanically driven equipment we are now challenged with supplying hydro
equipment to produce optimum annual energy production and return on investment.
Traditionally equipment was selected based on the power requirement and a site assessment. Due to the power demands
being relatively small the volume of water required was typically obtainable using the available head at site. Reaction turbines
were often selected as the heads were low and the efficiencies were high and, with earlier projects, impulse turbines
had not been invented.
Choosing the most suitable technology and size of turbine today requires a different approach; more technologies are available,
the environment is better protected, and energy production, rather than power requirement, is the main focus.
This transition of focus from power to energy means operating time has to be considered in the turbine selection process.
We continue to select turbines based on peak power performance for storage schemes. For Run‐of‐River projects we
consider average annual flow data relative to the turbine performance across all possible technologies. If the head of the
scheme is greater than 300m then only the Pelton design is feasible. For schemes with a head less than 50m then only a
Francis can be considered from our range of technologies. However for all schemes with the 50m to 300m head range we
consider Francis, Turgo and Pelton options.
1000 schemes, across 62 countries, have chosen the Gilkes Turgo as the optimum solution for their hydro scheme. There
are a number of reasons why so many have chosen to install a Turgo turbine and we would like to share some of their reasons
with you.
ENERGY EFFICIENCY
Energy is what dictates the income from a hydroelectric scheme. Power is the rating of the equipment. Time links power and
energy and the Turgo design is particularly good at operating over a wide range of flows. The Turgo’s ability to operate in
low flow conditions makes the Turgo particularly well suited to Run‐Of‐River hydro schemes.
During periods of high flows, i.e. when the design flow of the turbine is available to use, a well constructed Francis turbine
will always produce more power (primary ‘y’ axis and solid line) and, consequently, more energy (secondary ‘Y’ axis and
dashed line). As the volume of water in the river decreases the efficiency of the Turgo starts to exceed the efficiency of the
Francis – the result of course being the Turgo starts to generate more power and, more importantly, more energy. Only the
Turgo is running during the final stage of energy production ‐ which equates to more than 100 days.
RELIABILITY
Being of a simple construction the Turgo design requires
minimal maintenance. Our bearings are selected to absorb
worst case scenario loads, and run at runaway speed for
a designed period of time, – even though the Turgo is designed
to protect itself from an overspeed condition. Being
an impulse technology and having deflectors installed,
the Turgo can instantly protect the penstock from surge
pressures during a loss of load condition. Francis turbines,
even when fitted with a flywheel, can accelerate to runaway
speed in less than one second. It is not possible for
the Francis runner to pass these increased volumes of
water and, consequently, any unwanted transient pressure
(surge) is introduced to the system. Turgo’s are particularly
well suited, and popular, for energy recovery in water treatment
plants and we have options available for use with
potable water to specifically suit that application. 12 Inch mean diameter singlet jet Gilkes Turgo installed at Draper
Irrigation Company, UT, USA. Net Head 633ft, Rated Flow 11.7cfs,
Speed 1800rpm, Power 511kW, Year 2004
When operating on aggressive water, whether that is sand, silt or glacial matter the effects of the abrasion are significantly
less on the Turgo design. The jet of water and the profile of the runner are critical when maintaining high efficiencies.
Wear does, of course, occur but the removal of metal is small and uniform across the profile of the runner – thus having
minimal negative effect on turbine performance.
The wear on Pelton turbines has more of a negative effect as the splitting edge starts to deflect the jet. Wear on Francis
turbines increases the critical clearances within the turbine which, in turn, has a negative effect on turbine performance. The
maintenance for the Turgo can be planned and it would be very unusual for any unexpected turbine costs to be incurred.
The reliability of the Turgo design, and its receptiveness of poorer grid systems, makes them popular with remote energy
generation schemes.
Gilkes Turgo installed.
Grytviken, on South Georgia Island in
Antarctica is an example of a remote Turgo
operation – 12,000 miles (south) from Denver,
CO, USA.
• Net Head 213ft
• Rated Flow 15.36cfs
• Speed 1000rpm
• Power 250kW
• Year 2007
THE ORIGINAL MANUFACTURER
The Turgo impulse turbine was invented and patented by Mr. Eric Crewdson, the grandfather of our current Chairman Mr.
Charles Crewdson, in 1919. Further improvements in 1936 and 1962, complete with patents, enabled the runner to operate
faster and with a higher effi ciency across a broad fl ow range. Until the 1970’s Gilkes was the only manufacturer of Turgo
turbines but, as with all excellent designs, others do follow. In recent years, Gilkes, as the original designer of the Turgo, has
successfully improved the performance of schemes which originally opted for a Turgo manufactured by a
different supplier.
The Turgo impulse design is a high capacity, medium head, free jet impulse turbine. Instead of the jet striking the centre the
bucket at a right angle and splitting into two the jet on the Turgo enters the runner at an acute angle, passes through the
wheel, and discharges from the other side. The runner is designed to pass a large diameter jet of water relative to the mean
diameter, thus giving the turbine a high specifi c speed for an impulse design. For a given head and output the Turgo design
will run advantageously faster than the Pelton impulse design.
The illustration below shows the simplicity, and provides an insight into the robustness of, a typical twin Jet Turgo. The inlet
pipework is often located under the powerhouse fl oor. The turbine can be fully automated electrically or hydraulically. Water
simply discharges through the bottom of the turbine case. The runner can be mounted on a Gilkes bearing design or, for
larger units; the runner can be mounted directly onto an overhung generator shaft. The Turgo is available in both a single
and twin jet arrangement. The diagram shows a typical twin jet confi guartion.