Water-Energy Nexus: Impact on Electrical Energy Conversion and … · 2019. 11. 27. · Water-energy nexus Water is used in all stages of electrical energy generation Electrical power

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Blaže Gjorgiev and Giovanni Sansavini

Reliability and Risk Engineering Laboratory

Institute of Energy Technology - Department of Mechanical and Process Engineering

ETH Zurich

01.06.2018 1

Water-Energy Nexus: Impact on Electrical Energy Conversion

and Mitigation by Smart Water Resources Management

G. Sansavini

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Water-energy nexus

Water is used in all stages of electrical

energy generation

Electrical power is used for pumping,

reprocessing and disposing of water

Water scarcity and impact on power

generation

Large loss of generation: USA (2007,

2008, 2012), France (2003, 2006, 2009),

Germany (2003), Switzerland (2015)

Economic consequences

Reduced security of supply01.06.2018 2

Water-Energy Nexus: Impact of Water Scarcity

G. Sansavini

|| 8/24/2015Prof. Dr. Giovanni Sansavini 3

Water-Energy Challenge – Policy Interdependency

Electric Vehicles Require as much as Three

Times the Water per Mile as Gasoline

Bioethanol Productions Causing Local Droughts

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Water-Energy Nexus: impact of water scarcity

Technologies and policies for thermal power plant cooling

Smart management of water resources

Interplay between policy constraints and cooling technologies

Conclusions and future work

01.06.2018 4

Outline

G. Sansavini

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Once-through cooling

Efficient, simple, lower costs

Large withdrawals, effecting river water thermal

regimes

Wet-type cooling towers

Does not requires large withdrawals

Consumes the withdrawn water

Dry cooling towers

Does not require water for cooling

Higher costs, large space, lower efficiency

01.06.2018G. Sansavini 5

Cooling technologies for thermal power plants

https://www.quora.com/What-are-the-principles-of-cooling-tower

https://www.pi-hun.hu/angol-hutotornyokhttps://www.pi-hun.hu/angol-hutotornyok

http://www.crystal-lagoons.com/industrial-applications/

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River wildlife protection

Release of thermal load

River temperature constraints

Salmonid waters

Tmax ≤ 21.5 ⁰C

𝛥𝑇 ≤ 1.5 ⁰C

Water withdrawal and consumption

Based on local river concessioners

Consumption constraint to: 1% of

current flow


Policies for thermal power plant cooling

03

69 12

1518

2124

2730

33

10000

12000

14000

16000

18000

20000

22000

24000

0

0.1

0.2

0.3

0.4

0.5Flow decrement (%)

TP

P o

utp

ut (M

Wh

)

Temperature increment (⁰C)

1000MW TPP with once-trough cooling

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Can we influence river water temperature and

flow?

Yes!

How?

By manipulating reservoir releases

A model for smart scheduling of water resources

Hydro generation model

Thermal generation model

River water temperature prediction

Mixing of river flows

01.06.2018 7

Mitigating the vulnerabilities of water-energy

nexus for thermal power plant cooling

G. Sansavini

Sto

rage

Riv

er w

arm

ing

Pla

nt

coo

ling

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A model for smart scheduling of water resources

Hydro generation model

𝑃𝐻𝑗,𝑡 = 𝐶1,𝑗 ∗ 𝑉𝑗,𝑡2 +𝐶2,𝑗 ∗ 𝑋𝑗,𝑡

2 + 𝐶3,𝑗 ∗ 𝑉𝑗,𝑡 ∗ 𝑋𝑗,𝑡 +𝐶4,𝑗 ∗ 𝑉𝑗,𝑡 + 𝐶5,𝑗 ∗ 𝑋𝑗,𝑡 + 𝐶6,𝑖

Mixing of river flows

𝑇𝑟𝑖𝑣𝑒𝑟𝑚𝑖𝑥 =

𝑇𝑠𝑡𝑟1∗𝑄𝑠𝑡𝑟1 +(𝑇𝑠𝑡𝑟2∗𝑄𝑠𝑡𝑟2)

𝑄𝑠𝑡𝑟1+𝑄𝑠𝑡𝑟2

River water temperature prediction

𝜕𝑇

𝜕𝑡+ 𝑣 ∗

𝜕𝑇

𝜕𝑥=

1

𝐴∗𝜕

𝜕𝑡𝐴 ∗ 𝐷𝐿 ∗

𝜕𝑇

𝜕𝑥+

𝑅𝑊

𝜌∗𝑐𝑝∗𝐴∗ 𝑆

Thermal generation model

𝑇𝑜𝑢𝑡𝑟𝑖𝑣𝑒𝑟 =

𝑃𝑡ℎ𝑒𝑟𝑚𝑎𝑙𝑇𝑃𝑃

𝑄∗𝜌∗𝑐𝑝+ 𝑇𝑖𝑛

𝑟𝑖𝑣𝑒𝑟


Smart scheduling of water resources

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Test system with a hydro cascade

A cascade of four HPPs

Thermal power plant

1000 MW

Minimum output of 30%

Once-trough cooling

Data based on Switzerland

Aar rive basin hydrology/meteorology

Swiss electricity prices


Hydraulically coupled power plants

TPP

Hea

t b

ud

get

Mai

n s

trea

m

Secondary stream

R1 R2

R3

R4

N1 N2N3

N4

R – Reservoir N – Natural inflow G – Generator(s) In – TPP inlet Out – TPP outlet

G

GG

G

GG

In

OutMea

sure

d

Tem

per

atu

re

Known temperatures

Mixing of flows

Gjorgiev and Sansavini, Energy Conversion and Management, 2017

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Apply the model for smart scheduling

Results: Energy maximization

Energy increase

2.75 % to 6.37 %

Results: Revenue maximization

Revenues increase

3.60 % to 7.41 %

Strong interdependence

1.5 ⁰C increase in water temperature (when near allowed water temperature constraints)

can result in ~ 50% power output reduction, and in extreme cases, in plant shut down01.06.2018G. Sansavini 10

Smart management of water resources for improved power

generation

Electric power outputs of the TPP

500

600

700

800

900

1000

1100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Po

we

r (M

W)

Time (hour)

No smart scheduling

Hydro cascade scheduling

Smart scheduling / Entire system

|| 01.06.2018G. Sansavini 11

Water policy constraints and

cooling technologies

TPP

Hea

t ex

chan

ge w

ith

en

viro

nem

ent

Pri

mar

y st

ream

Secondary stream

R

R – Reservoir N – Natural inflow G – Generator(s) Pc – Condensate pump Pci – Circulation pump Pmu – Makeup water pump C – TPP condenser In – River water inlet Out – River water outlet

GG

In

OutMea

sure

d

Tem

per

atu

re

Known temperatures

Mixing of flows

N

TPP

Pc

PciPmu

C

C

Alternative

Pc

Once-trough cooling

Wet tower cooling

Mai

n s

trea

m

Assess how plant output is effected by the

flexibility of the water temperature constraints

Simulation of drought conditions

Allow constrained relaxations

Smart management

Different cooling technologies

Once-trough cooling

Wet type cooling tower

Considered water policy constraints

Water temperature

Water withdrawal and consumption

Gjorgiev and Sansavini, Applied Energy, 2018

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Once-trough cooling

No smart water management

Water temperature constraint

relaxations

Relaxation of 1.5 °C in the

water policy constraints

prevents the curtailment of

42%


Relaxation of water policies:

impact on power generation

0 0.2

0.4

0.6

0.8

10

2000

4000

6000

8000

10000

12000

14000

0 4 8 12 16 20 24 28 32 36 40 44 48

Temperature increment (⁰C)A

vaila

ble

en

ergy

(MW

h)

Flow decrement (%)a)

0 0.2

0.4

0.6

0.8

10.6

0.8

1

1.2

1.4

1.6

0 4 8 12 16 20 24 28 32 36 40 44 48


increm

ent (⁰C)

Flow decrement (%)b)

0 0.2

0.4

0.6

0.8

10

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

04812162024283236404448


incr

emen

t(⁰C)

Flow decrement (%)c)

||

Once-trough cooling

Smart water management

Water temperature constraint

relaxations

Compared to the un-optimized

case

At least 7% increase in the converted

energy

For most drought scenarios much less

relaxation than maximum allowed 1.5

°C is needed

Stable thermal power plant outputs01.06.2018G. Sansavini 13

Relaxation of water policies:

impact on power generation

0

0.2

0.4

0.6

0.81

0

2000

4000

6000

8000

10000

12000

14000

0 5 10 15 20 25 30 35 40 45

Temperature increment

(⁰C)

Av

aila

ble

en

erg

y (

MW

h)

Flow decrement (%)a)

00.2

0.40.6

0.8

10

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 510 15 20 25 30 35 40

4550


increment (⁰C)

Flow decrement (%)b)

00.2

0.40.6

0.8

10

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

05101520253035404550


increment (⁰C)

Flow decrement (%)c)

||

Wet type cooling tower

No power generation reduction required

Recommendations

Use location specific characteristics for drought

scenarios

River specifics

Long-term climate change prognosis

River water temperature and flow

Air temperature


Water policy constraints relaxation

effect on power generation

0

0.1

5 0.3

0.45 0.

6

0.7

5 0.9

12000

14000

16000

18000

20000

22000

24000

06

1218

2430

3642

48


TPP

en

ergy

(MW

h)

Flow decrement (%)

Electrical energy conversion under different drought

scenarios

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Wet cooling tower model

Input

Air temperature

Air moisture

Water temperature

Output

Tower efficiency

Power plant output

Climate change

Long-term effect

Optimal tower height


Wet tower cooling and

climate change

Ayoub, Gjorgiev and Sansavini, Energy, under review

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Smart water management via co-optimization of energy and water resources

can improve generation during droughts

Constraint relaxation can significantly improve power generation but other

constraints need to be considered also, i.e., ecology, hydro- and thermo-

peaking, hydropower market

Once-trough cooling highly sensitive to water temperature changes

Wet-cooling towers more resilient to water temperature changes

Need for systemic power system reliability analyses with droughts

Generation availability

Security of supply01.06.2018G. Sansavini 16

Conclusion and Future work

Thank you!

Questions?

Documents

Water-Energy Nexus: Impact on Electrical Energy Conversion and … · 2019. 11. 27. · Water-energy nexus Water is used in all stages of electrical energy generation Electrical power