Hydropower scheme to strengthen CES of Mongolia
Энэхүү өгүүлэл нь Төвийн эрчим хүчний системийг Энерги хуримтлуулах усан станц (ЭХУС) байгуулсанаар хэрхэн тогтвортой найдвартай болгох талаарх шийдлийг дэвшүүлсэн төслийн санал юм.Хуулбарлахыг хориглоно. Иш татахыг зөвшөөрнө.
PROJECT TITLE
Hydropower
scheme to strengthen Central Energy System of Mongolia [abbreviation is HPSCES]
OBJECTIVE OF PROJECT
Outcomes
of this project will introduce solution with strategy of new hydropower
scheme which would make stable electricity grid system to strengthen Central
Energy System. Operation concept of proposed pumped storage power plant is to
store excess electricity from CES produced by various power sources such as
intermittent renewable source and to produce electricity to CES when it has peak
load, therefor system will become more flexible than current condition.
Moreover, proposed pumped storage facility will response of safety guarantee
for CES.
Background
Introduction to Central energy system and problems
Mongolian
energy system has split into three parts namely West Energy System (WES),
Central Energy System (CES), and East Energy system (EES) as shown in figure 1.
Government has been proved many acts such as “Energy Sector Development
strategy” in 2002 and “Program on Integrated Energy System of Mongolia” in 2002
to unify those energy systems and to increase source of electricity especially
in CES, which is 80 percent of all Mongolian Energy sector and consumption
increasing dramatically. Many problems such as power shortage, unstable system,
and inefficiency production are related to CES for last two decade and maybe in
the further.
Figure 1. Colored
are Central energy system and its subdivisions. Dashed lines are proposed to
build by Program on Integrated Energy System of Mongolia, 2002.
Power sources of CES are becoming
slightly alternative but mainly dependent with coal-fired thermal power plant (TPP
or CHP – combined heat and power plant) which produces electricity and heat. Reason
of Mongolia not directly going to have alternative energy source, say renewable
energy, and to build new sources is aged coal power plants need to be replaced
with new or so called base load power plants. Single type coal power plant
source makes unstable and unsafe system (energy system security), since steam turbines
can’t be manipulated by consumption. Besides, some drawbacks, which can be
improved easily, appear from badly features of central energy system, listed in
following.
- Difference between daily max and min consumption is around 240-330MW; energy system must be fully supplied by this amount of electricity.
- Electricity demand increased with 40-60MW by year mostly depends on the Mining and Industry.
- During off-peak time 200-250MWh exceeded electricity exported to Russia with cheap cost (46MNT[1])
- During peak time 255-350MWh electricity imported from Russia and China with high cost (145MNT)
- Under current condition, forecast of 2020, new source with 500-600NW is needed in only CES
To
supply peak load around 900MW in the 18pm to 22pm, Coal power plant should work
as maximum load to try to meet demand, after sharply decrease consumption (blue
line in fig 2) by 330MW, loaded plant still working (purple line in fig 2) to
produce electricity like during peak load as shown in figure 2 that shows daily
load curves. This excess electricity exports to Russia with low cost around 46MNT[2]
under condition to get back during peak load. However, during the peak load (CES has two
peak load morning and night) imported electricity is more expensive (145MNT)
than exported before and max of additional imported electricity from Russia is
around 180MW. It is obvious that importing cost is higher than export in the Central
Energy System. This kind of unbalanced market mechanism and inefficiency management
leads to “budget deficit” of system which is one of basic problem cannot extend
to strengthen Energy system, itself.
Figure
2.
This is daily load curve of CES. Consumption and CES operation curve is drawn
based on mainly winter average daily load curves. Data source:
Furthermore,
finance statement is unstable, losses are charged by Government, and this
energy system is technically unsafe. This appraisal is arisen by slight
analysis of daily load curves and aging of available sources. Concerning of component of source type in
CES, coal fired heat combined power plant is monopoly dominated 95 percent and
rest of percent is renewable energy but not contain hydro sources.
Table 1.
Power sources in Central Energy System and its aging
Power plant
|
Installed capacity, MW
|
Current statement, max MW
|
Age, type
|
Thermal Power Plant IV[3]
|
580
|
580
|
31
|
Thermal Power Plant III
|
186
|
136
|
46
|
Thermal Power Plant II
|
24
|
21.5
|
53
|
Darkhan Thermal PP
|
48
|
48
|
49
|
Erdenet Thermal PP
|
36
|
28.8
|
24
|
Salkhit Wind Farm
|
50
|
18
|
5
|
UkhaaKhudag TPP
|
18
|
18
|
4
|
Import from Russia
|
-
|
180
|
-
|
Confirmed potential production from power sources can supply
barely base load amount of energy system and available range can be supplied
from source is ranged between 600-810MW depends on TPP operation and wind farm
in winter time. Generally harsh operation period is occurred in winter time
since power plants must supply heat to regarded cities. Maximum amount of
annual imported electricity is 330mln kWh in last year and peak was around
180MW which is increased at 6 percent from previous year and it will
progressively keep in the long run. To view aspect of safety for CES, there is
no power to accommodate any exceeded shortage outrange of importing agreement
with Russia and no source for failure of system component, such as spinning
reserve or other operation reserve. Therefore, some prevention and guarantees
related to system stability and safety are certified by additional term of
contract with Russia.
Government perspective to CES
Current
sources such as coal fired plant and wind farm is devoted base load plants,
which means that there must be safety reserve and peak loaded power plants
urgently. Licensed and to be commissioned by 2020 renewable projects with capacity
of 542.4MW (Sainbayar, 2015) are mainly focused
on solar and wind resources in south region of CES, likewise two hydropower plants
are proposed in northern part of system up to 400-542MW and one, namely Egiin
HPP, is persistently supported by Governments of Mongolia.
Table 2. All Proposed and licensed on grid power
sources for CES by Ministry of Energy
Licenses
|
Capacity, MW
|
Type
|
Licenses
|
Capacity
|
Type
|
Extension of existing TPP
|
70
|
Coal fired
|
Chandgana tal
|
600
|
Coal fired
|
Tsaidam nuur
|
600
|
Coal fired
|
Erdenetsogt
|
600
|
Coal fired
|
Buuruljuut
|
600
|
Coal fired
|
Tegshiin gobi
|
600
|
Coal fired
|
Shivee-ovoo
|
270
|
Coal fired
|
Baganuur
|
700
|
Coal fired
|
Cleantech
|
250-148(export)
|
Wind
|
Sainshand
|
52
|
Wind
|
AB solar wind
|
100
|
Wind (expired)
|
Cleanenergy Asia
|
50
|
Wind
|
Desert solar
|
30
|
Solar
|
Aydiner global
|
50.4
|
Wind (expired)
|
UB pumped storage
|
100
|
hydro
|
Egiin HPP
|
315
|
Hydro
|
TOTAL:
|
4839.4MW
|
||||
Above
mentioned projects are not ongoing projects, many of them being proposed and
studied for TOR stage. All licensed renewable energy capacity, supported to
build including wind and solar, is 542.4MW and they have planned to deliver
electricity to CES start around 2020.
National
renewable energy program, NREP, is main action plan on CES until 2020 and
approved with two implementation stage which are near term development goal
2005-2010 and midterm development goal 2011-2020. In this NREP, considered
hydropower plants, they should be implemented in near term stage according to
NREP, are left behind without studied in midterm term goal too. Abandon reason
might be regards its initial high investment comparing with wind and solar
system. But energy sources should be alternative and system should be safety
and security, they must be protected by itself are important issue in CES
development program. At least in order to improve operation of being proposed
renewable energy sources, there is needed specified amount of energy storage
facilities. UB pumped storage plant (commissioned by 2017, slacken now) can responsible for those
operations but its capacity small than import peak. Regional water scarcity
problem or capability of river does not effect on pumped storage hydro power potential.
Market survey of CES
The central
energy system consists of five co-generators (thermal power plants as shown in
table 1), the wind farm, one electricity transmission (CRETN) and 12
electricity distribution companies. Except three electricity distribution
companies they are all state owned joint stock company. Energy regulatory
Authority (ERA), established by 2001 Energy Law of Mongolia, introduced the
Single Buyer Model (SBM) as a market model since Sep 2002 for CES. Singly buyer
is Central Regional Electricity Transmission Network (CRETN) state owned
company, purchases electricity from five sources with addition import and sell
it to the 11 electricity distribution companies. In 2001, before
the inception of the Single Buyer Model, the rate of sales revenue collection
was only about 76.5%. This rate has increased every year and reached 101.8% in
2011 and collected additional MNT 4.3 billion more than planned (MNT 231.7
billion) in 2011 and accumulated debts of previous years were reduced
accordingly (Mongolia, 2011) .
Being tested in 2005, the spot has been effective since 2006, therefore the
National Dispatching Center was selected to act as a Spot market operator with
suppliers five co-generators based on the real consumption and scheduled
electricity rate difference. In
2011, about 3.9 million kWh of electricity or MNT 195.7 million was traded in
the spot market. The amount of traded electricity reduced by 20.6% from 2010,
which shows that generators’ imperfection had been reduced. TPP4 gained revenue
of MNT 123.2 million from the spot market trade in 2011. However, other power
plants had carried responsibility of paying amount MNT 123.2 million traded in
2011. Also ERA has started the auction market since Aug 2007, where an
incremental electricity demand is auctioned among generation licensees for the
best reduced tariff percentage. The National Dispatching Center operates the
auction market and in 2013 only 0.2mln kWh power were sold on the market due to
insufficient capacity reserve (Mongolia, 2013) . Conclusion of this survey lies market
is reforming and stable but connected new sources will be paid debts of aged
co-generations except TPP4. According to approved Renewable energy law in 2007,
following tariff range should be used for CES by Energy Regulatory Authority.
Table 3. Feed in tariff for renewable sources in
energy system of Mongolia
Source type
|
Hydro
|
Wind
|
Solar
|
|||
Capacity
|
Up to 0.5MW
|
From 0.5 to 2MW
|
From 2 to 5MW
|
Up to 5MW
|
||
On grid
|
0.045-0.06[4]
|
0.045-0.06
|
0.045-0.06
|
0.045-0.06
|
0.08-0.095
|
0.15-0.18
|
Off grid
|
0.08-0.10
|
0.05-0.06
|
0.045-0.05
|
0.045-0.06
|
0.10-0.15
|
0.2-0.3
|
Eventually on grid new power
sources will work financially dependent with others due to single buyer model,
which proposed to even incomes and expenses, to decrease accumulated debts. We need
to concern large scale hydropower scheme with installed capacity can evaluated
from further development consumption and excess electricity over 2030 and
operating marked can be studied and assessed over current markets. Possibility
and advantages of proposed
facility can competently run on auction and
spot market in CES.
Comparison of energy storage technologies
Currently,
there are six categories energy storage technologies have been applied
for power supply system. Pumped storage hydro power plant is widely used simple
proven technology comparing with other five technologies. Principle of storage technology is to store
energy of excess electricity in energy system during off-peak load and release
energy back to energy system during peak load, all have same tasks. Also some
largest facility such as pumped storage and thermal storage are response of
operation reserve for emergency or unexpected failure in energy system.
Figure
3.
Globally installed energy storage facilities are presented by categories since
2000 to 2015. Source: Global Energy Storage Database. In statistic of 2014, total grid connected PHS capacity was 138GW (International_Energy_Agency,
2015) .
Intermitted sources such as solar and wind farm
have to work with storage facilities to eliminate their disadvantage. Also many
countries have been converting to green energy due to their limited coal and
oil sources and renewable energy is becoming dominant sources. Therefore
storage technology will develop together. All of storage technologies are under
consideration and still developing.
Table 4.
Comparison of main properties of energy storage technologies (Karl Zach, 2012) (Xing Luo, 2014)
Technology
|
Typical
capacity
|
Power capital
cost, USD/MW
|
Discharge time
|
Efficiency
|
Life time
|
Development
stage
|
Application
|
Pumped storage
hydro power (PSH)
|
5MW-2GW
|
500-4000
|
4-100h
|
65-85%
|
+50 yrs.
|
Mature
|
Primary/secondary/tertiary
control, energy arbitrage
|
Compressed Air
energy storage (CAES)
|
25MW-2.5GW
|
400-1550
|
2-24h
|
40-70%
|
15-40 yrs.
|
Mature/premature
(AA-CAES[5])
|
Tertiary
control, energy arbitrage
|
Batteries
|
1kW-50MW
|
300-4000
|
1min-3h
|
65-75%
|
2-10 yrs.
|
Premature
|
Uninterruptible
power supply, primary/secondary control
|
Flywheels
|
5kW-20MW
|
250-350
|
4sec-15min
|
90-95%
|
20 yrs.
|
Mature
|
Primary
control, power quality
|
Hydrogen fuel
Cell storage system (HFCSS)
|
1kW-10GW
|
500-3000
|
0.01sec days
|
20-40%
|
5-10 yrs.
|
Prototype
|
RES-E[6]
fluctuation reduction, tertiary reserve
|
Super magnetic
Energy storage (SMES)
|
10kW-1MW
|
200-500
|
5sec-5min
|
95%
|
-30 yrs.
|
Premature
|
Uninterruptible
power supply, power quality
|
Super
capacitors
|
150kW
|
100-450
|
1sec-1min
|
85-95%
|
-10 yrs.
|
Premature
|
Uninterruptible
power supply, power quality
|
Since 2000, there are
commissioned 652 energy storage projects with total capacity of 45.77GW in
world wide. Hence 82 projects with capacity of 42.96GW are pumped storage
hydropower plant, 157 projects with 1.7GW are thermal energy storage, which is
not included in comparison table and many different thermal storage technology
can store energy from 0.1-100MW with capital cost 1000-15000USD/MW up to 20
years life time. For 2015, all up 21 pumped storage projects with capacity of
16.68GW are under construction in various countries such as China, Japan,
Russia, India and France etc.
PLAN
Unsafety
energy system with aged sources is receiving dramatically emerged consumption
year by year. Aforementioned financial and technical problems and proposed
renewable energy sources such as wind and solar in CES brings to purpose
project of energy storage technology during expected hours, which can be pumped
storage hydropower plant (PSHP) on grid. Proposed PSH plant not only store
energy produced from other sources such as excess electricity, solar and wind, but
also make more flexible manipulation
to CES, which will be managed easily and production will meet quickly to
consumption. Also to be flexible energy system, there must be peak load power
plant or spinning reserve and consisted to renewable energy sources.
In
the condition that will be occurred in 2020 case with total piloted projects
(capacity of 542.4MW) being on grid, the problem might arise like as: how can
improve effective of operation for those renewable sources, how to decrease
curtailment of wind farm or how to store electricity from those renewable
sources, how could be readiness of spinning reserve for main sources. Spinning
reserve is additional premier supply source when failure of power generation or
other shortage emergency case in energy system. At least one spinning reserve
source should be designed with capacity of biggest generator in energy system. This
project will be next generation
after 2020.
Capacity of purposed PSH
According
to NPRE until 2020, capacity of being commissioned plants including extension
of existing power plants is around 642.4MW. By approximate prediction, there
need to be storage of 400MW in CES, even UB pumped storage hydro power plant is
built (see table 2). And there is biggest generator of CES is 100MW, which can
be added capacity of new pumped storage hydro power plant for response of
spinning reserve. Hence capacity of new purposed pumped storage hydropower
plant is calculated as around:
Where
Pre is amount of storable renewable energy output including excess
electricity of base load sources and Pspinning is capacity of energy
system security source.
Figure
4.
Conceptual operation plan for pumping and turbine mode of proposed Shurgait PSHP assumption on after 2020.
Off
peak excess electricity arises from daily consumption curve, amount will
continuously increase, is not included to this calculation. This means proposed
facility will mainly use power produced from intermittent source such as solar
and wind to balance and to maintain their efficiency in CES. Facility operation
procedure is illustrated in figure 4.
Approximated technical design
Consumption
of CES is centralized in main three cities, Erdenet, Darkhan and Ulaanbaatar. It
implies that energy storage should be close costumers and placed in appropriate
site for selling electricity or water sources. Therefore site of PSH is
selected on the Shurgait river located 43km north of Ulaanbaatar city.
Figure
5.
Location of Proposed Shurgait PSHP
Lower
reservoir will created by concrete dam on the Shurgait river and upper
reservoir will built on top of right side of Mountain hollow. This site is
topologically suitable to create high head for hydropower. Assume the upper
reservoir minimum level can be EL1580.0m while lower reservoir maximum level
will be EL1400.0m. Difference between those levels gives minimum head for
operation of PSHP as,
Assuming local friction loss and efficiency of facility is 85 percent, we can calculate discharge needed to produce electricity amount of 500MW with four
unit that each with capacity of 125MW.
If supposing operation time is T=6 hours (on the current
statement hours of day: 9, 10, night: 18, 19, 20, 21, see figure 2), available energy is
And total discharge volume with n=4 turbine pump unit will
be
This
amount of water is needed to achieve purpose of the project and should be
contained upper and lower reservoir. Project side is chosen only on decision of
online survey study. Therefore volumes of purposed reservoirs are roughly
estimated in following chart. But it can give orientation to analysis of
reservoirs.
Table 5.
The Upper and lower reservoir volume calculation for Shurgait pumped storage
hydropower.
Upper reservoir
|
|||||||
Elevation, m
|
Surface area, m2
|
Interval, m
|
Volume, m3
|
Accumulated volume, m3
|
Lateral
|
Drawdown or level
variance for full operation stage in upper reservoir
|
|
1520
|
7246.852
|
0
|
0
|
0
|
|||
1540
|
69357.2
|
20
|
766040.55
|
766040.55
|
0.895514
|
||
1560
|
245143.9
|
20
|
3145010.72
|
3911051.267
|
0.717076
|
||
1580
|
448700.4
|
20
|
6938442.83
|
10849494.1
|
0.453658
|
||
1600
|
685594.8
|
20
|
11342952.1
|
22192446.23
|
0.345531
|
Area
|
567147.6
|
Total volume
|
22192446.2
|
22.2mln m3
|
h
|
12.68724
|
|||
Lower reservoir on
Shurgait river
|
|||||||
Elevation, m
|
Surface area, m2
|
Interval, m
|
Volume, m3
|
Accumulated volume, m3
|
Lateral
|
Drawdown or level
variance for full operation stage in lower reservoir
|
|
1349
|
136678.5
|
0
|
0
|
0
|
|||
1360
|
243240.4
|
11
|
2089554.06
|
2089554.064
|
0.438093
|
||
1380
|
860929.1
|
20
|
11041694.5
|
13131248.6
|
0.717468
|
||
1400
|
1711799
|
20
|
25727279.4
|
38858528.02
|
0.497062
|
Area
|
1286364
|
Total volume
|
38858528
|
38.8mln m3
|
h
|
5.593704
|
|||
From
the calculation, upper reservoir volume is 22.2mln m3 while lower
reservoir volume is 38.3mln m3. Careful design is needed to
determine volume of both reservoirs. During 6 hours operation time with turbine mode, upper reservoir
level would be changed 12.6m, while lower reservoir level will be changed
5.59m. Hence hydropower operation heads are calculated in following table.
Table 6.
Maximum and Normal/minimum operation head for Shurgait pumped storage
hydropower.
Upper reservoir
|
Lower reservoir
|
Max head
|
Min head
|
||
Head
|
Value
|
Head
|
Value
|
||
Maximum operation level
|
1592.69
|
Maximum operation level
|
1400.00
|
198.28
|
180.00
|
Normal operation level
|
1580.00
|
Normal operation level
|
1394.41
|
||
Drawdown, m
|
12.68
|
Drawdown, m
|
5.59
|
Average head
|
189.14
|
Now it is possible to calculate average energy using average
head.
Both
reservoirs are created by dam and dam heights are around 40m and 51m at upper
and lower reservoir, respectively. Dam heights are can be decreased by detailed
design. Various materials can be used for dam construction such as earth and
concrete on sound rocky basement. I hope geological condition and foundation of
dam is good in selected site, since the site is mountainside of the Chingiltei
mountain, which has metamorphic rock like granite and this kind of basement can
be stable base for concrete dam (Urban_planning_institude_of_Ulaanbaatar,
2013) .
Upper reservoir should be protected seepage under reservoir and trough a dam.
Most advanced technology in dam material is Rolled Compacted Concrete, RCC,
which is low cost concrete with less cement consumption, use to fly ash and dry than conventional concrete.
Figure 6. General
plan for proposed Shurgait pumped storage hydro
power.
Figure 7. Longitudinal
cross section through headrace (pressure tunnel) including pump/turbine house,
upper and lower reservoir
Technical aspects
Water resource for Shurgait PSH
Liquidated
organization, named Water Strategy Institute of Ministry of Nature and
Environment was studied hydro power potential resources on river with annual
mean discharge up to 1 cps throughout the northern and western part of
Mongolia, and concerned around 3800 small and large rivers has the power of
6400MW, with possible energy output of 56200MWh. Very earlier study was carried
out by cooperation between Hydro research and project implementation institute
with Hungarian Water Resources Authorities and result and possible strategy was
considered in Integrated water resource utilization and conservation scheme of
Mongolia in 1976. Those general studies have not involved possibilities of
pumped storage facilities. Thus, liable capacity of pumped storage should study
and evaluate by region in Mongolian territory.
Proposed
facility will build on upper stream of Shurgait river which has no hydrological
observation station or accumulated data. But Shurgait river is not temporary
river, that has minimum flow around 0.5m3/s which are noted during
in situ observations in 2011. To argue water availability for proposed facility,
let’s perform little analysis. Total required water volume to produce designed
energy is V=7196040 m3. Time to refill this amount of water into
reservoir would be
After
the filled, river flow should be released to downstream in river stream, stored
water will be recycled between two reservoirs to generate or store power. If
assuming rainfall and floods in Shurgait river, time to collecting water will
decrease. Whatever rainy or dry season, evaporation and filtration/percolation
will be main problem for water resources. Such possible water losses should be added
in effective reservoir volume range. Percolation losses would be less than
evaporation and it will decrease progressively.
Current technology for PSH
There are several proven and widely researched technology to
generate hydroelectricity namely conventional, run-of-river, and pumped storage
including small to large facilities. Small and run-of-river technology
will be harsh for Mongolian climate condition in winter time.
Figure 8. Power unit of hydropower plant with Kaplan
turbine and Electricity generator.
Source: Wikipedia
Main equipment to produce electricity is water turbine and
generator and named “unit” in power technology since they installed. Flowing
water is directed on to blade of turbine runner, creating a force on the
blades. Since the runner is spinning, the force acts through a distance (force
acting through a distance is the definition of work). In this way, energy is
transferred from water flow to turbine
and mechanical energy of spinning
turbine switched to generator. Water
turbine are divided into two groups namely reaction and impulse turbines and they
also split into four types called
Pelton, Francis and two types Kaplan, respectively. They are used for aforesaid
hydro power technology.
Reaction turbines are acted on by water, which changes
pressure as it moves through the turbine and gives up its energy. Newton’s
third law describes the transfer of energy for reaction turbines. Francis
(stationary blades) and Kaplan turbines (movable blades) are reaction turbine. Impulse
turbines change the velocity of water jet. The jet pushes on turbine’s curved
blades which changes the direction of the flow. The resulting change in
momentum causes a force on the turbine blades. Since turbine is spinning, the
force acts through a distance and the diverted water flow is left with diminished
energy. Pelton wheel is impulse turbine. Prior to hitting the turbine blades,
water pressure is converted to kinetic energy by nozzle and focused on the
turbine blades. This type of turbine is convention for small reservoir capacity
with large potential energy (difference pressure of input and output of
turbine).
Special reaction type turbine often preferred pump-turbine,
usually Francis turbine, is designed for pumped storage hydropower plant. They
can reserve flow and operate as a pump to fill upper reservoir during off-peak
hours, and then revert to turbine mode for power generation during peak demand.
It is important that pumped storage is not energy source but can be small
amount of producer in energy system, which has been proven on various researches.
Historically, in future there are several type of pumped storage technology
will be used (Giovanna Cavazzini, 2014) . Type of pumped
storage is characterized by set of hydraulic and electrical machines such as
turbine/pump or generator/motor as follow.
- Binary set: one pump-turbine (Francis) and one electrical machine (motor/generator) including single or multistage
- Ternary set: one turbine (mainly Pelton), one pump and one electrical machine (motor/generator)
- Quaternary set: turbine and pump drives generator and motor, respectively.
Advanced technology on PSH
There
are not special advanced technology in convention hydropower and used water
turbines, but some of afford has been done for Pumped storage technology. In the
advanced pumped storage technology, researchers have been study on following
three categories:
- Effective site and method surveying which include underground reservoir and coupled with compressed air storage etc. – not related this project.
- Adjustable speed pump-turbine including advanced runner like splitter runner
- Ternary unit, which employ a separate turbine and pump on a single shaft with the generator/motor.
Figure 9. Ternary
Unit with a Vertical arrangement and motor-generator above the turbine and
pump. Source: http://ceeesa.es.anl.gov/
Ternary
unit is most advanced technology innovated recently by Argonne National
Laboratory. The main difference between ternary unit and standard pump/turbine
(binary set) unit is that the ternary unit can simultaneously operate both the
pump and turbine mode. Three components – turbine, pump and generator – can
have two vertical configurations. Figure 10 shows vertical arrangement of generator
located above the turbine and pump (Koritarov, 2013) . Another
configuration is generator can be located between pump and turbine, turbine is
above the generator. This configuration is successfully applied Kopswork II PSH
in Austria and they use to Pelton turbine with 6 nozzles. Turbine output is
180MW, while pump input is 155MW (Hirtenlehner, 2006) . This means that using
this ternary unit they have able to produce more than 25MW power from absorbed
electricity from energy system.
Like
above, every project has its own unique properties and contains some innovation
of technology. For example Kannagawa pumped storage hydropower plant in Japan
introduced splitter runner for turbine/pump and full faced boring TBM machine
which can excavate steep angle of 48 degrees.
Figure 10.
Splitter Runner for Pump/turbine unit installed in Kannagawa PSH plants.
Splitter
runner is multi-blade pump/turbine runner that was jointly developed by TEPCO
and Toshiba Corporation. With the introduction of this runner, ten blades shown
in Figure 11, Kannagawa Hydropower plant increased its power generation and
pumping operation efficiency by about 4 percent. There are also implemented and
tested double and multi stage pump/turbine for high head which would increase
efficiency for both of turbine and pump mode. This project will include
innovation to improve efficiency or to decrease
cost like above mentioned advances.
Prospective to pump turbines of Shurgait PSH
Except
in terms of hydraulics and electrical machine, there are number of notable
things such as controls, distributions and automations and they are carried out
cooperation between cross disciplinary companies. We will discuss about possible
innovation or design criteria for “unit”
related to proposed facility based one technological advance. Generally reversible
machine unit consist of a
motor-generator (M/G) and a reversible pump turbine (P/T) that works either
pump or turbine depending on the direction of rotation. For motor-generator to
exploit its capacity to have variable speed for pump and turbine, possible
solution is tied with synchronous and asynchronous whose difference is a rotor.
Both solutions have its merit and demerit related their start up times, energized current (direct or
alternative current), and
ancillary equipment (frequency convertor) (Beyer, 2007) . If we use
asynchronous motor-generators in proposed facility, we have possibility to earn
following advantages, including:
- More flexible in unit operation
- Higher efficiency over a wide range of operations at partial load conditions
- A wide range of controllable and optimized power consumption in pump operation
- Additional and faster features for grid control, such as fast power outlet regulation
- Better use of the reservoir because higher water level variations can be allowed
- Better contribution to grid stability because of the high moment of inertia of rotating masses
- Regulate power both mode pump and turbine mode.
To
have successfully variable/adjustable speed for pump or turbine, we need to use
asynchronous motor-generator. But it would be costly than synchronous one. In
case of low head and speed, it would be gain efficiency turbine and pump mode
using synchronous motor-generator for variable speed, but not sufficient to
offset the substantial cost of power electronics convertor (Gish, et al.,
1981) .
Hence appropriate model should be carried out to determine optimization of
operation in both cases in order to have right solutions on it.
One
of important thing should be embedded in this project is able to work
simultaneously in pumping and generating mode. In fig 4, we can see that during
the pumping water to upper reservoir facility need to produce electricity to energy system. But most
case of operation except of ternary facility, modes are transposed like one by
one for whole facility whatever it has many units. It can be possible in our
project since facility have four units, two units can work pumping mode while remaining two can work turbine mode. In
this case main problem will be headrace for each unit (it will be costly) and
electricity regulation problems.
Final
abstract idea is that coupling with variable speed technology into ternary unit
can be innovation in this project. To become technically feasible this idea, many researches and modeling should be done as well as possible experiments. Ternary unit has numerous advantages
such as hydraulic circuit for load frequency control. Also if we set ternary
unit in facility, pump and turbine mode can be work on single unit to use
single headrace. Using this so called “hydraulic short-circuit operation”,
facility can goes on balancing of CES during its unrequired time.
Benefits
This
project will contain number of benefits related to economic and social and also
may influence negative result to environmental. Negative result can be specific
amount of area will be submerged by reservoir, which cannot be used other
purpose anymore. Here we will explain some important explicit benefits which
can be seen directly from output of this project.
Economic benefits
New
facility will offer employment to various fields of workers and engineers
during all stage from starting of the project. After commissioned, there still
will be position for engineers and workers. We will later discuss about
capacity of work force during the project detailed research and designing
stage. Next processing stages are unclear, we can’t specify proper status about employment for it and they are
determined sequentially in previous stage of implementation.
Basic
idea of this project is emerge from figure 2, to use excess electricity for
pumping water to upper reservoir and to response peak load using electricity
production of turbine mode. Excess electricity and demand are not equal means
there needs extra source to pumping water to upper reservoir to prepare
expected peak time in current condition of CES. On the other hand if the peak
is 180MW according to figure 2, proposed facility requires this amount of
electricity which can be used to pump up water to upper reservoir. In this
case, other intermittent source can be used to pumping like following
conceptual.
Figure
11.
Conceptual operation plan for current situation of CES that maximum peak load
of 180MW is imported from Russia.
Day
time, 8am to 18pm, proposed power plant will buy electricity from intermittent
renewable sources with cost of storing agreement, let’s assume current market
cost of 0.04USD/kWh which is equal to 78MNT rather than current exporting rate
to Russia, and purchased electricity will spend to pump up water from lower
reservoir to upper reservoir. During peak time or power shortage time, pumping
mode will switch to turbine mode to generate electricity with cost equally to
solar or wind selling price, say 0.08USD/kWh see table 3. Considering
efficiency, it is possible that totally Ebuy=600MWh electricity
would be stored and produced in proposed facility under current condition.
Let’s calculate one day revenue of this facility using total selling and buying
electricity.
Condition
without proposed facility and with same peak load (condition fig 2), the CES
lost 30000USD every day in export and import electricity. Hence, if purposed
facility is private, the intermittent sources lost 6000USD every day but they
can find more nonmonetary profit with
storage facility i.e. for wind farm, they are balanced and for solar, they
would be able to use full capacity of them on every sunny day.
Now
we can estimate how much revenue will receive when facility works with full
capacity, Eav= 1150.68MWh/year,
If
consider selling cost is 0.1USD per kWh, revenue would be 69.04mln USD. Those
calculation and cost stands on Feed in tariff for in Mongolian Renewable energy
law, see table 3. We need to check out and evaluate electricity price based on
facility investment cost.
Table 7.
Conceptual cost estimates and bill of quantities of proposed Shurgait PSHP
Items
|
Size
|
Quantity
|
Rate
|
Amount cost
|
Description
|
Upper dam
|
40m/932m
|
236106m3
|
140
|
33054840
|
Volume is approximated. Reference cost is used[7]
|
Lower dam
|
51m/470m
|
151810m3
|
140
|
21253400
|
Volume is approximated. Reference cost is used
|
Instrumentation
|
1
|
2744000
|
2744000
|
Construction equipment for RCC dam building
|
|
Access roads
|
15km
|
1
|
262000
|
262000
|
Global reference cost compared with Mongolian reference cost
|
Tunnel
|
Ф8.78m/1431m
|
86596m3
|
0.29
|
25112.84
|
Based on cost analysis result of
|
Surge shaft
|
25m
|
1
|
9419800
|
9419800
|
Reference cost is used
|
Steel tunnel line
|
Ф8.78m/200m
|
1
|
9014492
|
9014492
|
Inflation added research of
|
Underground power house
|
20/120/45
|
1
|
64537979
|
64537979
|
Reference cost is used
|
Generators
|
125MW
|
4
|
2954307
|
11817228
|
Same as turbine
|
Turbine/pumps
|
125MW
|
4
|
2954307
|
11817228
|
Cost evaluation formula for Francis turbine
|
Transformers
|
220kV
|
1
|
36648262
|
36648262
|
Reference cost is used
|
Transmission line
|
220kV*10km
|
4
|
264807
|
1059228
|
Based on research work of
|
Total, USD
|
201653570
|
||||
Allowance for other[8]
(10%)
|
40330713.97
|
Approximated
|
|||
Project management (10%)
|
20165356.98
|
||||
Total contingency (20%)
|
40330713.97
|
||||
Total estimated cost USD
|
302480354.8
|
Cinv
|
|||
From
this conceptual cost estimates, capital cost of proposed facility would be
604.96USD/kW, if the estimate is proper. Total cost of UB pumped storage
project in listed table 2 is 285mln USD, which gives capital cost of
2850USD/kW. Capital cost of our proposed facility is grounded nearest in lower range of global cost, which implies this
project is economically feasible, while UB pumped storage project is stood in
middle of global cost, see global cost range from table 4. Our conceptual cost
estimate may be seen abstract and missed some important activity cost related
construction and implementation. One of great example existing facility with
same capacity and near in cost, La Ta Khong Pumped storage hydropower in Thailand,
is built in 1994 with total cost of 18242mln JPY, which gives today’s capital
cost of 517USD/kW concerning inflation between 1994 and 2014. This is one of verification
that conceptual cost estimates is proper. Very similar project is Alqueva
pumped storage power plant (130MWx4=520MW) in Portugal, which has been
commissioned within two stages. Overall cost including both stages (2004, 2013)
is 1.7billion USD, which gives us 3269USD/kW of capital cost investment.
Comparing to Alquenve PSH, our proposed capital cost is quite small but dams
specifications or civil works are also small than Alquenve PSH dams.
One of other important term of economy is
payback period, which can be found for proposed facility like:
Here we use annual revenue instead of net
annual revenue because of undefinable cost of operation. According to this
analysis, payback period of 6.57 year is acceptable and again we can conclude
that proposed project is economically feasible and cost of selling electricity
can be decrease.
On the other hands, feasible capital cost make possibility
to use above concerned buying and selling price within Feed in tariff
for in Mongolian Renewable energy law,
table 3. Consequently, to be paid money for importing is circulating in own
(Mongolian market) market and economic deficit of state owned company will
decrease gradually and those changes let to offer cheap electricity tariff to
costumers.
Other benefits
This proposed project will bring us numerous
positive benefits after its completion. Here some non-monetary like technical
benefits are listed.
·
Firstly,
Central energy system would become flexible due to operation of storage
facility and general operation process will be suitable for implementing market
in CES such as spot and auction market, they are required more flexible, stable
energy grid.
- Proposed storage facility will response operation reserve for emergency or any failure related electricity distribution and all existing CHP steam turbines will have been guaranteed by Shurgait hydropower. Consequently, CES will become security and safety. Everyday electricity restriction by region in summer time will be decreased tangible (main costumer complaint is restriction now).
- Existing and coming to be commission energy sources, especially for renewable energy source, will be operated properly and fully by their capacity in on grid. Nowadays, main problem of existing wind farm, Salkhit with capacity of 50MW, is curtailment of power production because of balancing. Pumped storage is good balancer for wind farm, for solar too. Even without storage, if there is no demand, solar facility cannot work properly sunny day.
- It will be possible and open to create new renewable sources in CES, particularly wind farm nearest proposed facility where wind is rich, to transit gradually coal to renewable sources. In this case we need more storage facility. Launched project, UB pumped storage hydropower, is not enough for increasing demand in 5 years later in CES from now. Decision makers or experts should always think about next generation of current plan.
- This project will provide much experience to regarded facility or educate engineers to experts for this field. This also can be one of good prototype or model for building next pumped storage hydropower in western energy system where many suitable sites are existed.
- Most important thing is that proposed storage facility will provide independent energy system to neighbor country and furthermore it is also offer easy implementation of Unified smart grid which is essential strategy of Ministry of Energy referred in Program on Integrated Energy System of Mongolia 2007.
- It also will reduce CO2 emission for generating power. CO2 emissions per kWh from produced electricity are around 1091.44 ton in annual.
Conclusion
Based
on current condition and forecast of the Central Energy system of Mongolia, new
pumped storage hydro power plant named Shurgait PSH is proposed to build on
Shurgait river in northern side of Ulaanbaatar city to stabilize and maintain
operation of energy system. Purpose of this facility is to equalize power
balance for between costumer and sources, to response to operational reserve
(spinning) for any failure which can encounter in energy sources. This project
will serve its function after 2020 and many reasonable technical benefits will
be offered to CES such as flexible and security energy grid. Generally it will
be used to store electricity from intermittent sources like wind and solar
which are depended from more nature.
Shurgait
PSH plant has two reservoirs and one underground cavern had four units with
installed capacity of 500MW. Each unit has capacity of 125MW and planned to be built
couple headrace (head tunnel) connected to upper reservoir whereas each unit
has four tailraces to lower reservoir. Two reservoirs will be created by new
RCC dams, one in cross the river while another one is top of the mountain side.
Variable speed technology and ternary set technology have been considered for
hydro power units to meet and exploit current development on pumped storage
technology. Initial and crucial technological aspects are discussed and
evaluated in Technical aspect section.
For
energy system, which is base loaded and also slightly alternated by
intermittent sources, pumped storage hydropower plant will offer many advantage
in terms of economy and society. It is notable reason to propose this project
that to be independent, certified to costumer, technically stable, security and
flexible energy system must have energy storage and reserve facility. This
proposed facility will responsible both function to energy system during more
long time than its payback period. Some economic and social observable benefits
are discussed in the Benefit section. From the calculation, Conceptual capital
investment/cost and economic terms of proposed facility is reasonable to
evaluate that project is economically feasible. To comparing capital cost of
commissioned facility which has same capacity, total cost is possible that
conceptual cost estimation is closer to correct. In literature, European
weighted cost of pumped storage plant through ongoing projects is estimated as cost
of 980-1150USD/kW (Steffen, 2012) and cheapest capital
cost of 275USD/kW (Beyer, 2007)
is experienced in Avce PSH in Slovenia. Proposed facility has capital cost of 604.96USD/kW
and it may be decreased by detailed design.
Project
will be challenged for Mongolian, because of no experience to pumped storage.
But in future development, it is true for them that they will face pumped
storage hydropower plant in several sites in Mongolia. No reason to avoid it,
because of resource of the nature is limited.
REFERENCES
Beyer Thomas Goldisthal Pumped-Storage Plant: More than Power Production
[Online] // Hydro review worldwide. - Hydro world, 03 01,
2007. - 1. -
http://www.hydroworld.com/articles/print/volume-15/issue-1/articles/goldisthal-pumped-storage-plant-more-than-power-production.html.
Burentsagaan
Boldbaatar Assessment of Future
Hydropower plant investment in Mongolia [Thesis]. - Seoul : Seoul
National University, 2013. - Vol. master thesis.
Giovanna Cavazzini
Juan Ignacio Perez-Diaz
Technological development for pumped hydro energy storage [Report]. -
Madrid : European Energy Research Alliance, 2014.
Gish W.B. [et al.] An Adjustable Speed Synchronous Machine for
Hydroelectric Power Applications [Journal]. - [s.l.] : IEEE,
1981. - 5 : Vols. PAS-100.
Hirtenlehner Klaus Real efficiency of Pelton Turbine in Back Pressure
Operation [Journal]. - Steyr-Gleink : [s.n.], 2006.
International
Energy Agency Energy Technology
Perspectives 2015 [Report]. - Paris : International Energy Agency,
2015.
Karl Zach Hans
Auer et al Facilitating energy
storage to allow penetration of intermittent renewable energy
[Report]. - Munich : Intelligent Energy Europe, 2012.
Koritarov Vladimir Modeling Ternary Pumped Storage Units
[Report]. - Oak Ridge : Argonne National Laboratory, 2013.
Mongolia Energy
Regulation Commision Annual report
2011 [Report]. - Ulaanbaatar : Energy Regulation Autority, 2011.
Mongolia Energy
Regulatory Commition of Annual
report 2013 [Report]. - Ulaanbaatar : Energy Regulatory Commition
of Mongolia, 2013.
Nathaniel Efron
Megan Read Analysing International
Tunnel Costs [Report]. - Worcester : AECOM, 2012.
Sainbayar
Otgonbayar Renewable Energy
Regulation Policy [Conference] // ASEM: Mongolia-Country of Renewable
Energy. - Ulaanbaatar : [s.n.], 2015. - pp. 6-7.
Steffen Bjarne Prospects for pumped hydro storage in Germany
[Journal]. - Essen : Elsevier, 2012. - 2012 : Vol. 45.
Urban planning
institude of Ulaanbaatar
Environmental research and current statement of Ulaanbaatar city for General
development planning of UB to 2020 [Report]. - Ulaanbaatar :
Ministry of Construction and Urban development, 2013.
Waal Roland Dee Steel fible reinforced tunnel segments [Book]. -
Delft : Delft, 2000. - Vol. 1.
Xing Luo Jihong
Wang et al Overview of current
development in electrical energy storage technologies and appliaction in
power system operation [Journal]. - [s.l.] : Elsevier, 2014. -
Applied science : Vol. 137.
Yli-Hannuksela
Juho The transmission line cost
[Report]. - Vaasa : Technology and communication, 2011.
Reviewer’s comment and advices
I am
very appreciate to Prof. Mikami Yoshiki, Prof. Aruna Rohra Suda for their worth
advice and guidance and also to students of Interdisciplinary Joint project
seminar for their discussion.
Following
comments and corrections from reviewers are included in final version of
project proposal. Clarification of reviewer’s are responded with blue italic
form after their paragraph respectively.
Prof.
Aruna Rohra Suda [email of Jul 29]
Here are my comments regarding your project report:
- Overall, the report is much more detailed and clear now. You have included many calculations and verifications, which is good.
- Two clarifications:
a. In
Fig 8 (fig 11) you have shown buying of electricity, even during midnight hours
(1-6am). I understand that this is buying from the power generating plants. Are
you expecting plants to be generating electricity during that time? No, I not expect
that proposed plant to be work in midnight (off-peak time) time. Regarding to
question, at that time existing base load power plants will be produce excess
electricity independently with demand, whereas proposed plant will use to store
this generated electricity. Fig 11 represents conceptual operation of proposed
plant to current condition of CES (between periods of 2015-2020, this condition
which had excess electricity in night will be dominant in CES). Does that part of buying affect
your calculations of daily cost? Yes, it affects to daily revenue of proposed plants. But
considered costs or prices of selling and buying electricity between sources
and storages should be detailed by agreements in its implementing stage. I
think those cost are suitable and addable cost in current or future condition.
b. In
the Technical aspects section, the calculation for filling the reservoir, is
related to this project, it is good. But regarding turbines and pumps, you have
describes the general principles, but have not described what this project will
use. If you have not decided yet, you can make some comment about how (on what
factors) will it be decided. I slightly discussed about turbine pump for proposed
facility in Prospective to pump turbines of Shurgait PSH section. Technically
it is cumbersome for me to sort out what factor is critical for turbine pump.
- I have not verified your calculations, please make sure that they are correct. There are many projects of commissioned and ongoing now and their capital costs are evaluated to determine range of tentative investment (500-4000USD/kW) for pumped storage. Proposed project has capital cost of 604.96USD/kW which is verified by range of tentative cost and cost of some other similar projects such as La Ta Lhong (517USD/kW) and Alqueva I&II (3269USD/kW).
- Structurally, I think you can put the Technical Aspects section as Appendix or bring it before the Section on Benefits. Secondly, you should have a Conclusion section after Benefits, which summarizes the Plan and the Benefits. One large paragraph to one page, should be good. Thirdly, you need a References section. In various places, you have mentioned your references, but it is better to put them in one section and include ones, which you currently don’t have, but which are relevant, especially, ones which have similar calculations about other installed HP Storages.
That is all.
Overall, it has turned out to be a good Project Plan, I
think.
[1]
MNT is Mongolian currency tugrik. 1USD=1974MNT, 1JPY=16.04MNT on July 1, 2015
[2]
Exporting rate to Russia 46MNT/kW = 0.02USD/kW and importing rate from Russia
145MNT/kW=0.07USD/kW.
[3]
TPP IV is the main work horse in central energy system. Table data source:
Energy Regulation Committee of Mongolia.
[4]
Prices are given USD per kWh. Source: http://en.energy.gov.mn/laws/show/id/2
[5]
(Advance-) Adiabatic Compressed Air Energy Storage
[6]
Renewable Energy Source for Electricity Generation
[7]
In the most estimated cost has been used reference cost introduced by
consulting service company, called Hewitt Estimating. http://www.infrastructurecost.com/
[8]
Other includes some wages, intake,
tailrace structures, transportation and construction equipment cost.
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