Applications 18 WORLD PUMPS October 2013 www.worldpumps.com Advantages of using pumps as turbines Water & wastewater T he principle of a pump as a turbine is to pass water the wrong way through a pump, allowing the head (pressure) in the flow to act on the impeller blades, running it in reverse and providing a torque on the output shaft which can be used to drive something. Most commonly, that something is an asynchronous generator (a standard induction motor driven in reverse) converting the mechanical energy to elec- tricity, which can be consumed on site and/ or fed into the local grid (sold to the local power supply company). But that something could equally be another piece of machinery, even a pump. KSB PaTs perform best where there is a rela- tively constant water supply with suitable available head (typically greater than 10 m) but where the local electricity supplies are inadequate or unreliable. An example of this is Brazil, where it is almost impossible to find a location that does not feature a small waterway or rapids. At the same time, the country’s geography makes it difficult to supply remote settlements with electricity. It therefore makes sense to use these widely available hydropower sources to produce electricity locally rather than relying on diesel generators for which fuel has to be purchased. PaTs also have their role in locations where power is both available and reliable. The need for cleaner, renewable energy that is cost effective means that PaTs open up the oppor- tunity for water utility companies to look at exploiting smaller flows, previously consid- ered uneconomical, as well as replacing existing conventional hydro turbines. Typical Rising energy prices and limited energy resources call for alternative solutions that save money and are environmentally friendly. KSB has supplied pumps as turbines (PaTs) for many years. It offers huge advantages such as low investment, service and maintenance costs, with the added benefit of being more straightforward to operate and maintain than conventional turbines. This article explores some uses and locations of PaTs. End suction pump run in reverse mode.
Transcript
Applications18
WORLD PUMPS October 2013
www.worldpumps.com
Naamloos-4 3
Advantages of using
pumps as turbines
Water & wastewater
The principle of a pump as a turbine is
to pass water the wrong way through
a pump, allowing the head (pressure)
in the fl ow to act on the impeller blades,
running it in reverse and providing a torque
on the output shaft which can be used to
drive something. Most commonly, that
something is an asynchronous generator (a
standard induction motor driven in reverse)
converting the mechanical energy to elec-
tricity, which can be consumed on site and/
or fed into the local grid (sold to the local
power supply company). But that something
could equally be another piece of machinery,
even a pump.
KSB PaTs perform best where there is a rela-
tively constant water supply with suitable
available head (typically greater than 10 m)
but where the local electricity supplies are
inadequate or unreliable. An example of this
is Brazil, where it is almost impossible to fi nd
a location that does not feature a small
waterway or rapids. At the same time, the
country’s geography makes it diffi cult to
supply remote settlements with electricity. It
therefore makes sense to use these widely
available hydropower sources to produce
electricity locally rather than relying on diesel
generators for which fuel has to be
purchased.
PaTs also have their role in locations where
power is both available and reliable. The need
for cleaner, renewable energy that is cost
eff ective means that PaTs open up the oppor-
tunity for water utility companies to look at
exploiting smaller fl ows, previously consid-
ered uneconomical, as well as replacing
existing conventional hydro turbines. Typical
Rising energy prices and limited energy resources call for alternative solutions that save money
and are environmentally friendly. KSB has supplied pumps as turbines (PaTs) for many years. It
off ers huge advantages such as low investment, service and maintenance costs, with the added
benefi t of being more straightforward to operate and maintain than conventional turbines. This
article explores some uses and locations of PaTs.
End suction pump run in reverse mode.
Applications20
WORLD PUMPS October 2013
www.worldpumps.com
costs are becoming a top priority. The fact
that the turbine and the generator are both
widely used pieces of equipment, so can be
operated and maintained by existing staff
without the need for any specialist training,
adds to their attraction.
Many types of pumps - end suction, axially
split case and multistage ring section, for
example - can be used as PaTs, both in hori-
zontal and vertical confi gurations, so there is
fl exibility in adapting this technology to suit
specifi c fl ows, heads, site conditions and
space constraints. Couple this to that fact
that PaTs can be used to generate from as
little as 1 kW up to hundreds of kilowatts,
examples of this are compensation fl ows and
spill fl ows from dams, but other fl ows such
as fi nal effl uent from sewage treatment works
can be considered. The lower procurement
costs of PaTs coupled with high (and
increasing) energy prices means that the
payback period of KSB PaT systems are usually
between three and fi ve years. The power
generated by these PaTs off sets the overall
costs of the infrastructure and puts power
back into the grid.
KSB’s PaTs have been successfully installed in
the UK in a number of projects, including
Meldon Dam, Morwellham Quay and Avon
Dam near Buckfastleigh in Devon. In this case,
KSB supplied two PaTs, one for generating
power 24/7 from the compensation fl ow and
a larger unit for generating from the spill fl ow,
mainly in the winter months. This KSB PaT
off ered 80% effi ciency and compared excep-
tionally well against other turbine suppliers,
exceeding expectations in power generation
versus asset cost. KSB worked alongside May
Gurney to put forward the most cost eff ec-
tive solution whilst ensuring maximum
power generation and revenue for the end
user, South West Water.
PaTs can also be used with fl uctuating water
fl ows by using several diff erent sized units,
bringing them into and out of service
according to changing demand. This requires
only minimal control, so PaTs are starting to
create signifi cant interest in the current
economic climate, where reducing energy
Avon Dam energy recovery system successfully uses the pumps as turbines solution.
