Innovation in Global Power - Parsons Brinckerhoff

Hydropower – New Technologies, New Considerations
access way into the turbine pit, with an unsymmetrical load
distribution. The integral design of the generator support
bracket foundation with the turbine pit wall was complex
and fraught with constructability issues to ensure that the
machine alignment during a worst case operating scenario
would not exceed generator design tolerances. The alternative
of supporting the generator thrust bearing directly
off the pump-turbine head cover would have negatively
impacted on the access to the pump-turbine for routine
maintenance and deemed no overall reduction in the total
unit outage for major pump-turbine overhauls. A partial
compromise was reached by ensuring there was enough
height in the turbine pit to temporarily lift and suspend
the headcover to work on the turbine.
• Pump starting system. The client specified originally
a dual static frequency converter system (SFC). These
devices act like a variable speed drive to start the unit in
pumping mode. In conducting a reliability cost benefit study
for the forecasted pump duty, we verified that a single SFC
system with 50 percent redundancy resulted in considerably
lower plant and powerhouse construction costs.
Pre-Feasibility Design for Asia Project. This project,
which is for an independent power producer (IPP) and is
confidential, is a 300 MW two-unit pumped storage scheme.
We recently completed the pre-feasibility conceptual design
stage, for which we developed two interesting solutions:
• Ring dyke embankment. We located a suitable location
for the lower reservoir, which fit in well with other desirable
features at the selected location. There was no natural
depression for the upper reservoir, however, particularly
at a high enough elevation to offer an attractive economic
solution. We investigated placing a ring dyke embankment
on top of the hill to create the upper reservoir. This
option gave a more attractive ratio of head to horizontal
distance between reservoirs, a key survey requirement for
identifying potentially economic reservoir locations.
• Deep silo powerhouse. Instead of the conventional
underground scheme, we proposed a deep silo powerhouse
approximately 130 m (427 feet) deep (Figure 1). Silo
powerhouses have been used on other projects, but we
could not find any example of one as deep as this one.
The silo powerhouse eliminates many of the tunnels
required for an underground powerhouse such as those
for vehicle access and ventilation, and hence was intuitively
cheaper when considering the local topography.This concept
was adopted for the purposes of costing the scheme in parallel
with a market and economic study to verify in principle
that there was a potential commercially viable project.
Both of these solutions will be tested at the feasibility stage
when geological drilling is performed to better understand
the site conditions and an alternative underground scheme
will be studied and priced to verify the better option.
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The Future of Pumped Storage
The advances mentioned above and others in pumped storage
technology, plus the fact that underground schemes are often
desirable because they minimise visual impacts, will continue to
make pumped storage an important part of power generation
schemes in the future. For example, a scheme with the sea as
the lower reservoir (i.e., pumping sea water) is in operation in
Japan. This type of scheme may be suitable in other locations
around the world. In addition, variable speed generators
have been installed in some pumped storage plants to obtain
the best turbine efficiency in generating and pumping modes.
Traditional large pump storage will benefit from the renewed
interest in nuclear power generation expansion, as such plants
operate at a constant load and need to be complemented
with other more dynamic and flexible generators to suit the
varying power system load demand. Finally, pumped storage
will play a key role also in “alternative” power generation
schemes. For example:
• Pumped storage has significant advantages in networks
with a high proportion of wind power.
• Disused deep open cast and underground mines could be
adapted for pump storage.
• There are benefits to be gained from combining tidal
generation with pumped storage to optimise power
delivery when the tidal pattern is out of phase with
the power demand.
Acknowledgements. The authors wish to thank Mr. F. Louwinger of Eskom Holdings
Ltd for his consent to the publication of this article and for his useful comments.
Ian McClymont is an electrical engineer with more than 30 years experience on
hydro-electric power development and refurbishment projects. He has considerable
experience with pre-feasibility and tender designs of pumped storage schemes.
Paul Reilly, a mechanical engineer, heads the hydro group in Christchurch, which
provides a range of services including new development design, refurbishment/
enhancement, owner’s engineer, and due diligence. He has worked for more than
14 years on numerous international and New Zealand hydro projects.
Figure 1: Conceptual design of a deep silo powerhouse.
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