View
220
Download
0
Category
Preview:
Citation preview
8/3/2019 Dersch Dry Cooling
http://slidepdf.com/reader/full/dersch-dry-cooling 1/15
solar thermal power plants
Water saving heat rejection for
Jürgen Dersch, Christoph Richter
Institute of Technical Thermodynamics
8/3/2019 Dersch Dry Cooling
http://slidepdf.com/reader/full/dersch-dry-cooling 2/15
Overview
Overview
Project goals
Simulation tool
First results
Outlook
Slide 2 > NREL Trough Meeting 2007 > Dersch
Heat rejection technologies
8/3/2019 Dersch Dry Cooling
http://slidepdf.com/reader/full/dersch-dry-cooling 3/15
Slide 3 > NREL Trough Meeting 2007 > Dersch
Research Project „EFCOOL“
Research Project „EFCOOL“
Title: “Water efficient cooling of solar thermal power plants”
Solar Paces Task III Activity „Efficient Cooling Strategiesfor Solar Thermal Power Plants“
Motivation: Solar thermal power plants with Rankine cyclesneed heat rejection for condensation of the turbine exhauststeam in order to reach low exhaust pressures and torecycle the working fluid
Typically ambient temperatures are high and water is rareat sites showing attractive annual DNI values
8/3/2019 Dersch Dry Cooling
http://slidepdf.com/reader/full/dersch-dry-cooling 4/15
EFCOOL TasksEFCOOL Tasks
Investigation of different heat rejection technologies for
STPP
Developing of a simulation tool for annual calculations atdifferent sites
Identification of potential enhancements for existing coolingtechnologies
Investigation of new operation strategies for STPP with
l
Slide 4 > NREL Trough Meeting 2007 > Dersch
respect to cooling (e.g. the usage of thermal storage to shiftthe cooling oad to night hours)
8/3/2019 Dersch Dry Cooling
http://slidepdf.com/reader/full/dersch-dry-cooling 5/15
Cooling technologies
(Heller System)
Air cooled condenser (ACC)
Hybrid cooling
temperatures.
Slide 5 > NREL Trough Meeting 2007 > Dersch
Cooling technologies
Once through cooling
Most efficient and cheapest technolgy but rarely applicable for STPP
Wet cooling tower
Efficient at moderate investment costs but high water consumption
Indirect dry cooling
Less efficient and more expensive than wet cooling but almost no water
consumption for cooling.
Less efficient and more expensive than wet cooling but almost no waterconsumption for cooling.
Combination of wet and dry cooling technologies.
Dry cooling with water usage during time periods with peak ambient
8/3/2019 Dersch Dry Cooling
http://slidepdf.com/reader/full/dersch-dry-cooling 6/15
Wet Cooling Tower
Ambient wet bulb temperature defines
the condenser pressure
temperature)
Surface condenser (TTD~3K)
Cooling water and boiler feed waterare separated
Natural draft or cooling towers with
fans are possible
Source: SPX
Slide 6 > NREL Trough Meeting 2007 > Dersch
Wet Cooling Tower
(less fluctuations than dry bulb
8/3/2019 Dersch Dry Cooling
http://slidepdf.com/reader/full/dersch-dry-cooling 7/15
Heller SystemHeller System
j(TTD~0.5K)
mixed
Source: EGI
Slide 7 > NREL Trough Meeting 2007 > Dersch
Dry bulb temperature defines thecondenser pressure
Direct contact et condenser
Cooling water and boiler feed water are
Large underground storage tanks areused to drain the system
Ratio cooling water flow / boiler feedwater appr. 50
Natural draft or cooling towers with fans
are possible
8/3/2019 Dersch Dry Cooling
http://slidepdf.com/reader/full/dersch-dry-cooling 8/15
Air Cooled Condenser
necessary
l
configurations
Slide 8 > NREL Trough Meeting 2007 > Dersch
Air Cooled Condenser
Dry bulb temperature controls thecondenser pressure
Steam is condensed without theusage of an intermediate medium
Large cooling surfaces are
The ACC should be ocated closeto the turbine
Typically forced draft A-frame
8/3/2019 Dersch Dry Cooling
http://slidepdf.com/reader/full/dersch-dry-cooling 9/15
The Annual Simulation ToolThe Annual Simulation Tool
Steady state models in MS Excel
Based on empirical equations or performance mapsgenerated by other more sophisticated tools or delivered bysuppliers
Part load characteristics are considered
simplified IEA method
Slide 9 > NREL Trough Meeting 2007 > Dersch
Levelized electricity cost (LEC) calculation using the
Hour by hour calculation with meteo data for different sites
8/3/2019 Dersch Dry Cooling
http://slidepdf.com/reader/full/dersch-dry-cooling 10/15
0.20
0.25
0.30
0.35
0.40
5 10 15 20 25 30 35 40 45
t dry bulb in °C
g r o s s
e f f i c i e n c y
Wet Cooling 60% Load
Wet Cooling 100% Load
Heller Cooling 60% Load
Heller Cooling 100% Load rel. humidity: 40%
0.6
0.7
0.8
0.9
1.0
1.1
1.2
5 10 15 20 25 30 35 40 45
t dry bulb in °C
r e a v e
c e n c y
0.2
0.4
0.6
0.8
1.0
cooling load
Examples of the Performance Maps
l t i e
f f i i
y
i
Turbine
Slide 10 > NREL Trough Meeting 2007 > Dersch
Examples of the Performance Maps
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0.00 0.20 0.40 0.60 0.80 1.00 1.20
load
r e l a t i v e e f f i c i e n c
operat ng range
Heller Cooling SystemWhole Plant
8/3/2019 Dersch Dry Cooling
http://slidepdf.com/reader/full/dersch-dry-cooling 11/15
Condenser Temperatures and Ambient Conditions
0
10
20
30
40
50
60
70
80
90
Wet cooling, phi 40%
Wet cooling, phi 100%
Wet cooling, phi 0%
Condenser Temperatures and Ambient Conditions
c o n d e n s e r t e m p e r a t u r e i n ° C
Heller System
10 15 20 25 30 35 40 45 50
ambient dry bulb temperature in °C
Slide 11 > NREL Trough Meeting 2007 > Dersch
5
8/3/2019 Dersch Dry Cooling
http://slidepdf.com/reader/full/dersch-dry-cooling 12/15
Slide 12 > NREL Trough Meeting 2007 > Dersch
Meteo Data of Different Sites (DNI > 250W/m²)Meteo Data of Different Sites (DNI > 250W/m²)
0
200
400
600
800
1000
-10 0 10 20 30 40 50
Temperature in °C
D N I i n W / m 2
0
0.2
0.4
0.6
0.8
1
-10 0 10 20 30 40 50
Temperature in °C
r e
l . H u m i d i t y
0
200
400
600
800
1000
-10 0 10 20 30 40 50
Temperature in °C
D N I i n W
/ m 2
0.00
0.20
0.40
0.60
0.80
1.00
-10 0 10 20 30 40 50
Temperature in °C
r e l . H u m i d i t y
Spain
California
8/3/2019 Dersch Dry Cooling
http://slidepdf.com/reader/full/dersch-dry-cooling 13/15
Results of Annual Calculation (Heller Systemcompared to Wet Cooling)
Slide 13 > NREL Trough Meeting 2007 > Dersch
Results of Annual Calculation (Heller Systemcompared to Wet Cooling)
1 . 0
5
0 . 9
5 0 . 9
9 1 . 0
4
0 . 0
4
1 . 0
6
0 . 9
5 1 . 0
5
0 . 9
4 0 . 9
9 1 . 0
1
0 . 0
3
1 . 0
6
0 . 9
1
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
s o l a r f
i e l d
s i z e
a n n u
a l n e t e
f f i c i e
n c y
a n n u
a l n e t e
l e c t r i
c o u t p
u t L E
C
a n n u
a l w a t e
r c o n
s u m p t i o n
t o t a l i n
v e s t c
o s t s
a n n u
a l O & M
c o s t s
Spain California
Reference is the sameplant at the same sitewith wet cooling tower
Gross output 55 MW
Water costs 1.0 €/m3
8/3/2019 Dersch Dry Cooling
http://slidepdf.com/reader/full/dersch-dry-cooling 14/15
of LEC on Water CostsSensitivitySensitivity of LEC on Water Costs
L E C i n € / k W h
0.24
0.22
0.20
0.18
0.16
0.14
0.12
wet cooling Spain
Heller cooling Spainwet cooling Cal.
Heller cooling Cal.
0 2 4 6 8 10 12 14 16
water costs in €/m³
Slide 14 > NREL Trough Meeting 2007 > Dersch
8/3/2019 Dersch Dry Cooling
http://slidepdf.com/reader/full/dersch-dry-cooling 15/15
Conclusions and Next Steps
Change-over to dry cooling for STPP would reduce the water demand
significantly (>95% reduction) The electricity generation costs will increase by up to 5% (depending on
water cost) compared to evaporative cooling
Hybrid cooling technologies to enhance the cooling at high dry bulbtemperatures
Usage of storage technologies to shift the cooling loads partly to times with
lower ambient temperatures
Slide 15 > NREL Trough Meeting 2007 > Dersch
Conclusions and Next Steps
Financing of the EFCOOL project by the German Federal Ministry for the Environment, NatureConservation and Nuclear Safety is gratefully acknowledged
Recommended