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Chapter 2
Pumped Hydroelectric Storage
Chi-Jen Yang
Duke University, Durham, North Carolina 27708, USA. Tel. +1 919 9459075. E-mail
address: [email protected]
Contents
Introduction
Pros and Cons
Historical Developments
Prospects
4.1 Revival of Conventional Pumped Hydroelectricity Storage
4.2 Alternative and Novel Pumped Hydroelectricity Storage designs
4.3 Retrofits of existing PHS and conventional hydropower stations
References
Abstract
Pumped hydroelectric storage (PHS) is the most established technology for utility-scale
electricity storage and has been commercially deployed since the 1890s. Since the 2000s,
there have been revived interests in developing PHS facilities worldwide. Because most
low-carbon electricity resources (for example, wind, solar, and nuclear) cannot flexibly
adjust their output to match fluctuating power demands, there is an increasing need for
bulk electricity storage due to increasing adoption of renewable energy. This chapter
introduces the PHS technology, the pros and cons, its historical developments, and the
prospect.
Key Words:
Pumped Hydroelectric Storage; Closed-loop; Pump-back; Peak Shaving
1. Introduction:
Pumped hydroelectric storage (PHS) is the most widely adopted utility-scale electricity
storage technology. Furthermore, PHS provides the most mature and commercially
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available solution to bulk electricity storage. It serves to stabilize the electricity grid
through peak shaving, load balancing, frequency regulation, and reserve generation.
Japan currently has the largest installed PHS capacity in the world [1], followed by China
[2] and the United States [3]. China currently has the most aggressive plan to expand
PHS installation, with 14 GW under construction and many more planned. China is
expected to surpass Japan in installed PHS capacity by 2018. Table 1 shows the installed
PHS capacities in major countries [2, 3, 4, 5].
Table 1. Installed PHS capacities.
Country
Installed PHS Capacity
/(MW)
Japan 27 438
China 21 545
USA 20 858
Italy 7 071
Spain 6 889
Germany 6 388
France 5 894
India 5072
Austria 4 808
Korea, South 4 700
United Kingdom 2 828
Switzerland 2 687
Taiwan 2 608
Australia 2 542
Poland 1 745
Portugal 1 592
South Africa 1 580
Thailand 1 391
Belgium 1 307
Russia 1 246
Czech Republic 1 145
Luxembourg 1 096
Bulgaria 1 052
Iran 1 040
Slovakia 1 017
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Argentina 974
Norway 967
Ukraine 905
Lithuania 900
Philippines 709
Greece 699
Serbia 614
Morocco 465
Ireland 292
Croatia 282
Slovenia 185
Canada 174
Romania 53
Chile 31
Brazil 20
A PHS facility is typically equipped with pumps and generators connecting an upper and
a lower reservoir (Figure 1). The pumps utilize relatively cheap electricity from the
power grid during off-peak hours to move water from the lower reservoir to the upper
one to store energy. During periods of high electricity demand (peak-hours), water is
released from the upper reservoir to generate power at a higher price.
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Figure 1. PHS Diagram.
There are two main types of PHS facilities: (1) pure or off-stream PHS, which rely
entirely on water that were previously pumped into an upper reservoir as the source of
energy; (2) combined, hybrid, or pump-back PHS, which use both pumped water and
natural stream flow water to generate power [4]. Off-stream PHS is sometimes also
referred to as closed-loop systems. However, some may define closed-loop systems more
strictly as being entirely isolated from natural ecosystems. The U.S. Federal Energy
Regulatory Commission defines closed-loop pumped storage as projects that are not
continuously connected to a naturally-flowing water feature [5].
The efficiency of PHS varies quite significantly due to the long history of the technology
and the long life of a facility. The round-trip efficiency (electricity generated divided by
the electricity used to pump water) of facilities with older designs may be lower than
60%, while a state-of-the-art PHS system may achieve over 80% efficiency.
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2. Pros and Cons
By storing electricity, PHS facilities can protect the power system from outages. Coupled
with advanced power electronics, PHS systems can also reduce harmonic distortions, and
eliminate voltage sags and surges. Among all kinds of power generators, those peak-load
generators typically produce electricity at much higher costs than the base-load ones.
PHS provides an alternative to peaking power by storing cheap base-load electricity and
releasing it during peak hours.
PHS facilities provide very large capacities of electricity, with low operation and
maintenance cost, and high reliability. The levelized storage cost for electricity using
PHS is usually much lower than other electricity storage technologies.
There are several drawbacks to PHS technology. The deployment of PHS requires
suitable terrains with significant elevation difference between the two reservoirs and
significant amount of water resource. The construction of a PHS station typically takes
many years, sometimes over a decade. Although the operation and maintenance cost is
very low, there is a high upfront capital investment in civil construction, which can only
be recouped over decades.
Environmental impacts are also serious concerns and have caused many cancellations of
proposed PHS projects. Conventional PHS construction sometimes involves damming a
river to create a reservoir. Blocking natural water flows disrupt the aquatic ecosystem and
the flooding of previously dry areas may destroy terrestrial wildlife habitats and
significantly change the landscape. Pumping may also increase the water temperature and
stir up sediments at the bottom of the reservoirs and deteriorate water quality. PHS
operation may also trap and kill fish. There are technologies to mitigate the ecological
impacts. Fish deterrent systems could be installed to minimize fish entrapment and
reduce fish kill. The water intake and outlet could be designed to minimize the turbulence.
An oxygen injection system could also compensate for the potential oxygen loss due to
warming of the water because of pumping. In some cases, the PHS system may serve to
stabilize water level and maintain water quality [6]. The potential impacts of PHS
projects are site-specific and must be evaluated on a case-by-case basis. Governments
usually require an environmental impact assessment before approving a PHS project.
Most PHS facilities have good safety records. Nevertheless, the upper reservoir failure of
Taum Sauk PHS station in the United States should be heeded as a reminder of its
potential danger. On December 14, 2005, the upper reservoir of Taum Suak was
overfilled, and the embankment was then overtopped and breached. The suddenly leased
water washed away over one square kilometer of forest, uprooted all the trees and
obliterated a house in its path. Although the Taum Sauk PHS station was later repaired
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and brought back to operation in 2010, the reservoir failure incident should provide
important lessons for future PHS design, construction and operation.
3. Historical Development
The earliest PHS in the world appeared in the Alpine regions of Switzerland, Austria, and
Italy in the 1890s. The earliest designs use separate pump impellers and turbine
generators. Since the 1950s, a single reversible pump-turbine has become the dominant
design for PHS [7]. The development of PHS remained relatively slow until the 1960s,
when utilities in many countries began to envision a dominant role for nuclear power.
Many PHS facilities were intended to complement nuclear power in providing peaking
power.
In the 1990s, the development of PHS significantly declined in many countries. Many
factors may have contributed to the decline. Low natural gas prices during this period
make gas turbines more competitive in providing peaking power than PHS.
The earliest PHS facilities were built in Italy and Switzerland in the 1890s [7]. Before the
1950s, most of the PHS facilities were located in Europe. The United States completed its
first PHS station in 1928. Japan built its first PHS in 1934 and China in 1968. Since the
1950s, the adoption of PHS has gradually spread all over the world. As of 2014, the U.S.
DOE Global Energy Storage Database recorded over three hundred operating PHS
stations with total capacity of 142 GW in 41 countries [8].
The design and site selection for PHS facilities are greatly influenced by national policies.
Japan, China, and the United States have the largest PHS capacities in the world. Table 2,
3, and 4 list the PHS facilities in Japan, China, and the United States. The distinctive
policies and regulatory regimes for PHS in Japan, China, and the United States offer
interesting contrasts and may reveal useful policy insights.
The buildup of PHS capacities in Japan has been relatively steady over several decades.
The Japanese power sector is mainly composed of vertically-integrated regional electric
power utilities, which build, own and operate the PHS facilities. The vertically integrated
power sector structure has provided a stable and predictable business environment that is
favorable to the investments in PHS. The path of PHS development PHS in Japan is an
epitome of PHS development worldwide. Before the early 1960s, PHS facilities were
rare and small, mostly of hybrid design. The deployment started to accelerate since the
1960s and continued throughout the 1990s. Since the 1970s, pure/off-stream PHS has
become the dominant design, which is likely a result of increased concerns for ecological
impacts of the hybrid systems. In addition to having the worlds largest PHS capacities, Japan is also the world leader in employing seawater PHS and variable-speed PHS.
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Table 2 PHS stations in Japan.
Plant Name
(Japanese)
Plant Name
(English) Location Type
Rating/
(MW)
Commission
Year
Ikejirigawa Nagano Prefecture Hybrid 2 1934 Omorikawa Kochi Prefecture Hybrid 12 1959 Morotsuka Miyazaki Prefecture Hybrid 50 1961 Hatakenagi No.1 Shizuoka Prefecture Hybrid 137 1962 Mio Nagano Prefecture Hybrid 36 1963 Ikehara Nara Prefecture Hybrid 350 1964 Ananaigawa Kochi Prefecture Hybrid 13 1964 Shiroyama Kanagawa Prefecture Pure 250 1965 Yagisawa Gunma Prefecture Hybrid 240 1965 Shinnaruhagawa Okayama Prefecture Hybrid 303 1968 Nagano Fukui Prefecture Hybrid 220 1968 Kagetaira Tokushima Prefecture Hybrid 47 1968 Azumi Nagano Prefecture Hybrid 623 1969 Takane No.1 Gifu Prefecture Hybrid 340 1969 Midono Nagano Prefecture Hybrid 245 1969 Kisen'yama Kyoto Pure 466 1970 Shintoyone Aichi Prefecture Hybrid 1 125 1972 Numappara Tochigi Prefecture Pure 675 1973 Okutataragi Hyogo Prefecture Pure 1 932 1974 Niikappu Hokkaido Hybrid 200 1974 Ohira Kumamoto Prefecture Pure 500 1975 Namwon Hiroshima Prefecture Pure 620 1976 Mazekawa No.1 Gifu Prefecture Hybrid 288 1976 Futai Dam Niigata Prefecture Pure 1 000 1978 Shin-Takasegawa Nagano Prefecture Hybrid 1 280 1979 Okuyoshino Nara Prefecture Pure 1 206 1980 Okuyahagi No.2 Aichi Prefecture Pure 780 1980 Okuyahagi No.1 Aichi Prefecture Pure 323 1980 Tamahara Gunma Prefecture Pure 1 200 1981 Motokawa Kochi Prefecture Pure 615 1982 Daini Numazawa Fukushima Prefecture Pure 460 1982 Takami Hokkaido Hybrid 200 1983
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Matanoagawa Tottori Prefecture Pure 1 200 1986 Tenzan Saga Prefecture Pure 600 1986 Imaichi Tochigi Prefecture Pure 1 050 1988 Shimogo Fukushima Prefecture Pure 1 000 1988 Okawachi Hyogo Prefecture Pure 1 280 1992 Okumino Gifu Prefecture Pure 1 500 1994 Shiobara Tochigi Prefecture Pure 900 1994 Futai Dam No.2 Niigata Prefecture Pure 600 1996 Kazunogawa Yamanashi Prefecture Pure 1 200 1999
Okinawa Seawater
Pumped Hydro Okinawa Prefecture Pure 30 1999
Kannagawa Gunma Prefecture Pure 940 2005 Omarugawa Miyazaki Prefecture Pure 1 200 2007 Shumarinai Hokkaido Hybrid 1 2013 Kyogoku Hokkaido Pure 200 2014
China is a latecomer in the worldwide PHS deployment, but it is catching up quickly.
With the largest PHS capacities planned and under construction, China will soon
overtake Japan as the host of the largest PHS capacities in the world. Most of the PHS
facilities in China are relative new, with large capacity and off-steam design.
Chinas regulatory regime for PHS has been through great changes in the past two decades. Before 2004, most of the PHS facilities in China were built by local
governments and local grid companies with diverse pricing models. In 2002, China
restructured its power sector by separating them into 2 state-owned grid companies and 5
power generation corporations. In 2004, the National Development and Reform
Commission promulgated a regulation which specified that PHS stations are transmission
facilities and should be constructed and managed by the grid companies, and that the
construction and operation costs of PHS should be incorporated into the operation costs
of the grid companies [9]. The decision to treat PHS as transmission facilities has
contributed to the rapid expansion of PHS in China.
Table 3 PHS stations in China.
Plant Name
(Chinese)
Plant Name
(English) Province Type
Rating/
(MW)
Commission
Year
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Gangnan Hebei Hybrid 11 1968
Miyun Beijing Hybrid 22 1975
Panjiakou Hebei Hybrid 270 1992
Cuntangkou Sichuan Pure 2 1992
Guangzhou Phase 1 Guangdong Pure 1,200 1994
Shisanling Beijing Pure 800 1997
Yangzhuoyong Tibet Pure 90 1997
Xikou Zhejiang Pure 80 1998
Tianhuangping Zhejiang Pure 1 800 2000
Guangzhou Phase 2 Guangdong Pure 1 200 2000
Xianghongdian Anhui Hybrid 80 2000
Tiantang Hubei Pure 70 2001
Shahe Jiangsu Pure 100 2002
Huilong Henan Pure 120 2005
TONGBAI Zhejiang Pure 1 200 2006
Hakusan Jilin Hybrid 300 2006
Taian Shandong Pure 1 000 2007
Langyashan Anhui Pure 600 2007
Xilongchi Shanxi Pure 1 200 2008
Yixing Jiangsu Pure 1 000 2008
Zhanghewan Hebei Pure 1 000 2008
Huizhou Guangdong Pure 2 400 2009
Heimifeng Phase 1 Hunan Pure 1 200 2009
Bailianhe Hubei Pure 1 200 2010
Baoquan Henan Pure 1 200 2011
Pushihe Liaoning Pure 1 200 2012
Xiangshuijian Anhui Pure 1 000 2012
Xianyou Fujian Pure 1 200 2013
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Most of the PHS facilities in the United States were built in the 1970s and 1980s. Since
the 1990s, the construction of PHS slowed down in the United States. Environmental
concerns caused the cancellation of several PHS projects and significantly prolonged the
permitting process. Power sector restructure also contributed to this slowdown. During
the 1990s, the United States started to restructure the power sector by separating
generation from transmission. The nature of energy storage falls into the gray area
between generation and transmission [10]. Because the net electricity output of PHS
operation is negative, a PHS facility usually cannot qualify as a power generator.
Although their crucial load-balancing and ancillary services to the grid and reduces the
needs for transmission upgrades, PHS facilities are not recognized as parts of the
transmission infrastructure [11]. This confusion in business models has deterred the
development of PHS in the United States.
Table 4 PHS stations in the United States.
Plant Name County State
Type
Rating/
(MW)
Commission
Year
Rocky River Litchfield CT Hybrid 31 1928
Flatiron Larimer CO Hybrid 9 1954
Hiwassee Dam Cherokee NC Hybrid 95 1956
Lewiston Niagara Niagara NY Hybrid 240 1962
Taum Sauk Reynolds MO Pure 408 1963
Yards Creek Warren NJ Pure 453 1965
Cabin Creek Clear Creek CO Pure 300 1967
W R Gianelli Merced CA Pure 424 1967
Muddy Run Lancaster PA Pure 1 072 1967
ONeill Merced CA Pure 25 1968
Thermalito Butte CA Hybrid 83 1968
Edward C Hyatt Butte CA Hybrid 293 1968
Salina Mayes OK Pure 288 1970
FirstEnergy Seneca Warren PA Pure 469 1970
Smith Mountain Franklin VA Hybrid 247 1970
Mormon Flat Maricopa AZ Hybrid 54 1971
Horse Mesa Maricopa AZ Hybrid 100 1972
Degray Clark AR Hybrid 28 1972
Northfield Mountain Franklin MA Pure 940 1973
Ludington Mason MI Pure 1 979 1973
Blenheim Gilboa Schoharie NY Pure 1 000 1973
Jocassee Pickens SC Pure 612 1974
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Bear Swamp Berkshire MA Pure 600 1974
Castaic Los Angeles CA Hybrid 1 275 1976
Carters Murray GA Hybrid 250 1977
Fairfield Pumped Storage Fairfield SC Pure 511 1978
Raccoon Mountain Hamilton TN Pure 1 714 1979
Wallace Dam Hancock GA Hybrid 209 1980
Grand Coulee Grant WA Hybrid 314 1980
Harry Truman Benton MO Pure 161 1981
Mount Elbert Lake CO Pure 200 1983
Helms Pumped Storage Fresno CA Pure 1 053 1984
Clarence Cannon Ralls MO Hybrid 31 1984
Bath County Bath VA Pure 2 862 1985
J S Eastwood Fresno CA Pure 200 1987
Bad Creek Oconee SC Pure 1 065 1991
Waddell Maricopa AZ Pure 40 1993
North Hollywood Los Angeles CA Hybrid 5 1993
Rocky Mountain Floyd GA Pure 848 1995
Richard B Russell Elbert GA Hybrid 328 2002
Lake Hodges San Diego CA Pure 42 2012
The diverged paths of PHS development in Japan, China, and the United States have
shown that the national regulatory and institutional environments have tremendous
impacts on the deployment of PHS. PHS facilities are large facilities that require huge
upfront capital investments, and the paybacks are spread over many decades. If a
government wishes to facilitate the development of PHS, it needs to provide a stable and
predictable regulatory environment, and a reasonable pricing scheme that allow the PHS
facilities to be compensated for their services to the transmission grid.
4. Prospects
In recent years, due to increasing concern for global warming and the call to de-carbonize
electricity, there has been increasing commercial interest in PHS [12]. Developers are
actively pursuing new PHS projects around the world.
4.1 Revival of conventional PHS
More than 100 new PHS plants with about 74 GW capacities worldwide are expected to
be in operation by 2020 [13]. China has the most aggressive plan. In 2014, the Chinese
government announced its plan to more than quadruple its current PHS installations to a
total capacity of 100 GW by 2025 [14]. Driven by the need to accommodating rapid
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growth of intermittent renewable electricity, Europe is also witnessing a renaissance of
PHS, particularly in Spain, Switzerland, and Austria, with 27 GW new PHS capacity
expected by 2020 [15]. Although Japan already has the highest density of PHS
installation in the world, Japanese power companies are continuing to develop more PHS
plants. The United States is also experiencing a revival of PHS development. In 2014, the
U.S. Federal Energy Regulatory Commission issued licenses to construct and operate two
new PHS facilities (1.3 GW Eagle Mountain PHS and 400MW Iowa River PHS).
Another application for construction and operation license (for the 1 GW Parker Noll
PHS) is currently under review. In addition, there are over 40 proposed PHS projects
currently conducting feasibility studies with issued preliminary permits. With the mature
technology and high volume of commercial development activities, PHS will certainly
remain the most dominant energy storage technology in the foreseeable future.
4.2 Alternative and novel PHS designs
Variable Speed PHS: Most existing PHS facilities are equipped with fixed-speed pump
turbine. While those fixed-speed PHS facilities may provide economical bulk electricity
storage, they can only provide frequency regulation during its generating mode, but not in
pumping mode. With the increasing adoption of variable power sources such as wind and
solar, there is an increasing demand for frequency regulation. New variable speed
technology allows PHS facilities to regulate frequency at both pumping and generating
modes. Japan has pioneered the variable-speed PHS technology and has successfully
operated such systems at the Okawachi PHS station for over twenty years [16, 17].
European countries are actively introducing variable speed PHS in recent years in order
to accommodate more variable renewable electricity in their power portfolios [18].
Seawater PHS: In addition to the worldwide revived interests in developing conventional
PHS projects, many developers are also proposing new approaches. Japan has pioneered
seawater PHS. The Okinawa seawater PHS station, which has commenced operation in
1999, is the worlds first seawater PHS system [19]. The Okinawa PHS station uses the open sea as the lower reservoir together with a constructed upper reservoir at 150 meters
above sea level. New seawater projects have been proposed in Ireland, Greece, Belgium,
and the Netherlands [20, 21, 22, 23]. The energy islands concept proposed by the Dutch
consulting company DNV KEMA has an unusual approach; they plan to use the open sea
as the upper reservoir, and construct the lower reservoir by dredging and building a ring
of dikes at a depth of 50 m below sea level.
Underground PHS: Researchers since the 1970s [24], have proposed the possibility of
utilizing underground caverns as lower reservoirs for PHS projects but so far none have
been built [25]. The commercial interests in developing underground PHS have
resurfaced in recent years in the United States. Several U.S. developers have received
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preliminary permits to study the feasibility of building underground PHS facilities at their
identified sites. A British company Quarry Battery is also working on developing
underground PHS facilities with abandoned quarries [26].
Compressed Air PHS: A promising innovative design (Figure 2) is to replace the upper
reservoir in PHS with a pressurized water container [27]. The air within the pressure
vessel becomes pressurized when water is pumped into the vessel. Instead of storing
potential energy in elevated water, the proposed compressed air pumped hydro system
stores the energy in compressed air. This innovative design could potentially free PHS
from the geographic requirements and make it feasible at almost any location with
flexible and scalable capacity. This concept is discussed in more detail in chapter 7.
Figure 2. Diagram of compressed air PHS
Undersea PHS: Another innovative concept (Figure 3) is to utilize the water pressure at
the bottom of the sea to store electricity from off-shore wind turbines [28]. The system
places submerged pressure vessels (hollow concrete tank) on the sea floor. It uses
electricity to pump water out of the tank to store energy, and generate electricity when
seawater is filling into the tank through the generator. This concept is further discussed in
chapter 6.
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Figure 3. Diagram of undersea PHS
4.3 Retrofits of existing PHS and conventional hydropower stations
Many existing PHS facilities were built many decades ago and therefore were equipped
with outdated and inefficient technology. There is a significant potential in increasing
PHS capacity simply by renovating and upgrading the existing PHS facilities. Upgrades
to old PHS facilities typically include replacing outdated pumps/turbines, impellers, and
control systems with new advanced equipment. Many existing PHS station may increase
the capacity by 15% to 20% and efficiency by 5% to 10% [7]. In addition, many existing
conventional hydropower stations could be re-engineered to add a lower reservoir and
pump-back units to pump the water back to the upper reservoir during off-peak hours,
and become combined PHS stations for use with intermittent energy from renewable
sources such as wind turbines and solar panels.
Although PHS may be an essential enabling technology for de-carbonizing electricity, the
political will to mitigate carbon dioxide and to remove regulatory barriers for PHS is far
from certain. The price of natural gas is also a key determinant in the future of PHS.
Because PHS is essentially a peak-load technology, which competes directly with gas-
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fired power, low natural gas price may render PHS uncompetitive. The vision of de-
carbonizing electricity and how PHS fits into it, will likely vary from country to country.
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