CSP Training series : solar desalination (2/2)

Dr. Julián Blanco Plataforma Solar de Almeria [email_address] CONCENTRATING SOLAR POWER AND DESALINATION Solar Desalination Webinar #2 21 October 2010

CSP+D JUSTIFICATION
DUAL POWER AND WATER SUITABLE CONFIGURATIONS
CSP+D POTENTIAL BENEFITS
CSP+D EFFICIENCIES ESTIMATION. MED-RO COMPARISON
CSP+D ONGOING RESEARCH
PRESENTATION PROGRESS

Clear coincidence in the existence of water problems (arid and semi-arid zones) and the availability of abundant solar radiation SOLAR ENERGY & ARID ZONES The binomy WATER / ENERGY is always present  Water problems can be significantly reduced if energy is easily available. However if the energy is also a problem, the situation becomes much more complicated

CSP+D: ADVANTAGES & DRAWBACKS
Combining CSP and Desalination facilities (CSP+D) could be a very attractive solution as:
At many location with high solar potential, projects can be more attractive to local stakeholders than just power production ones.
Technological synergies can be identified to potentially reduce the cost of combined power and water production against the independent production of the same products.
Financial schemes could also benefit, as water and power cost can be better adapted to the specific local conditions of the facility.
However, the concept has also some drawbacks:
CSP+D concept needs, obviously, facilities to be located near the sea, where land cost and availability could be a significant problem.
DNI is normally lower at the areas close to the sea.
Some / many technological aspects are not yet solved

WORDWIDE WATER STRESS Over-exploitation of fresh and groundwater resources Human Development Report 2006 (UNDP)
There are serious water deficits in many world areas
In most of these areas, CSP has a very high potential
MENA region is clearly one of this areas

Population size and renewable freshwater availability in MENA countries (1995 data and 2025 estimations) Water Status MENA Countries. Arab Water Council. 5th World Water Forum. Istanbul (2009) MENA FRESHWATER DEFICIT

Water Status MENA Countries. Arab Water Council. 5th World Water Forum. Istanbul (2009) Total water withdrawals from surface water and groundwater sources in several Arab countries (total consumption ≈ 220 billion m 3 /year) MENA FRESHWATER DEFICIT Current water deficit in the MENA region is estimated to exceed ONE NILE amount (about 60 billion m 3 /year) By the year 2050, it is estimated that this deficit will rise to 2.5 NILES

CSP+D JUSTIFICATION
CSP+D EFFICIENCIES ESTIMATION. MED-RO COMPARISON

Water to power ratio
Optimising a combined cycle from 1.2 to 1.5 tons/hr of steam per each MW installed can be achieved for desalination
Approximately 21,000 m 3 /d every 100 MW installed can be produced
DUAL POWER & WATER PLANT
Most of large thermal desalination units are combined with power plants
Reduction in the overall efficiency in the electricity production but part of the energy discharged to the ambient in the cooling system can be used to desalination
Multi-Effect Distillation (MED) has a good matching with power plants when energy is supplied at low pressure (about 0.4 bar)
Rankine power cycle should be designed to achieve exhaust steam from the turbine at 70ºC (instead of the conventional 35-40 ºC)
Fujeirah (United Arab Emirates) hybrid power and desalination plant (MSF – RO: 378,500 m 3 /d)

Conventional Rankine Cycle Power Plant STEAM POWER PLANT Degasifier Condenser Water at 36ºC Water at 31ºC Thermal Energy Generator Vapor at 70 mbar/40 ºC G Electricity Steam turbine Vapor at 100 bar/450 ºC Electric Energy Boiler Thermal Energy Vapor at 17 bar/225 ºC

0,22 bar 62ºC MED Plant PR : 10 Distilled: 0,25 hm 3 /day Number of effects: 12 260 t/h of coal 633 MW Boiler Generator Degasifier Steam turbine Vapor at 100 bar/450 ºC Vapor at 17 bar/225 ºC G Electricity 50 mbar 35ºC Distilled Sea water Brine Thermal Energy Electric Energy DUAL POWER & DESALINATION Vapor at 63ºC

Typical power/water production ratio: 4:1 (MW e /hm 3 year ) . With this configuration a 250 MW gas turbine can deliver energy to produce about 66 hm 3 /year (180.000 m 3 /day) of desalinated water in a TVC-MED desalination plant DUAL CONFIGURATIONS Combination of desalination plant with gas turbine and heat recovery boiler

TVC-MED coupled with a gas power cycle ( 256 MWe ). If combined cycle -> additional 193.6 MWe would be produced Steam at 330ºC is produced from the waste heat recovery boiler, and used as live steam in the thermo-compressor. Saturated steam is extracted at 50ºC from an intermediate point of the desalination plant. Exhaust steam is obtained at 50ºC Combination of desalination plant with gas turbine and heat recovery boiler Total desalinated water energy cost = 27.15 kWh/m 3 Energy lost method: DUAL CONFIGURATIONS

Typical power/water production ratio: 3:1 (MW nominal power /hm 3 year ) . With this configuration a 100 MW steam turbine can deliver energy to produce about 33 hm 3 /year (90.000 m 3 /day) of desalinated water in a MED desalination plant Combination of desalination plant with high pressure boiler and steam turbine DUAL CONFIGURATIONS

Combination of desalination plant with gas turbine, heat recovery boiler and steam turbine Typical power/water production ratio: 9:1 (MW nominal power /hm 3 year ) . With this configuration a 1000 MW combined cycle can deliver energy to produce about 110 hm 3 /year (300.000 m 3 /day) of desalinated water in a MED desalination plant DUAL CONFIGURATIONS

Total desalinated water energy cost = 19.6 kWh/m 3 Saturated steam is extracted at 50ºC from an intermediate point of the desalination plant. Exhaust turbine steam is obtained at 50ºC TVC-MED coupled with a conventional 50 MWe steam cycle. Intermediate extraction is done at 204.3ºC (HP), to be used as live steam in thermocompressor DUAL CONFIGURATIONS

Exhaust steam at 70 ºC is used as thermal energy source for the desalination plant Total desalinated water energy cost = 4.5 kWh/m 3 LT-MED coupled with a conventional 50 MWe steam cycle DUAL CONFIGURATIONS

When water demand is stable all over the year but power demand substantially varies from summer to winter, the optimised desalination scenario involves hybrid configurations including reverse osmosis technology. Additional advantages of RO: reduced product water temperature and boron removal. Hybrid configurations DUAL CONFIGURATIONS

CSP+D JUSTIFICATION
CSP+D EFFICIENCIES ESTIMATION & MED-RO COMPARISON

CSP-MED / CSP–RO COMPARISON
Considered data
Investment cost of MED: about 1050 € per installed m 3 /day
Average electricity consume of MED: 1.5 kWh/m 3
Thermal energy average consume of MED: 65 kWh/m 3
Investment cost of RO: about 850 € per installed m 3 /day
Average electricity consume of RO: 3.5 kWh/m 3
Thermal energy average consume of RO: 0 kWh/m 3
Life plant (amortisation): 20 years
Hypothesis
50 MW power plant working 24 hours/day
Efficiency: 38% -> needed thermal power input: 131,6 MW
Energy to cooling process: 100 – 38 – 5 ≈ 57%
57% of 131,6 MW = 75 MW
All this energy can be used to desalination without any penalty to power generation (at turbine)
Max. amount of water to be produced by MED: 28.000 m 3 /day

CSP-MED / CSP–RO COMPARISON
Considered data
Desalination plant of 28.000 m 3 /day
Yearly water production: 10.22 Hm 3
Investment cost of MED: 29.4 M€
Investment cost of RO: 23.8 M€
Electricity cost: X €/kWh
* No operation and maintenance cost are considered Cost calculation*

CSP-MED / CSP–RO COMPARISON Simplified yearly cost of MED: Simplified yearly cost of RO: Electricity cost to break-even (MED cost = RO cost)
If electricity cost < 1.4 € cents/kWh -> RO cost < MED cost
If electricity cost > 1.4 € cents/kWh -> RO cost > MED cost

CSP COOLING REQUIREMENTS 530ºC WATER T-S DIAGRAM W Q* Q W* > W Q* ≈ Q Relative requirements of cooling water (m 3 /MWh produced) are higher at a solar power plant 1* 2* W* 450ºC CSP POWER PLANT
Work at turbine:
W = h 1 –h 2
T 1 = 450ºC (limited by the parabolic trough solar collector)
Cooling energy:
Q 1 = h 2 -h 3
CONVENTIONAL PLANT
Work at turbine:
W* = h 1 –h 2
T 1* = 450ºC (limited by the parabolic trough solar collector )
Cooling energy:
Q* = h 2 -h 3

Conventional cooling systems at CSP plants are also very intensive in energy consume. A 50 MWe Solar Power Plant require 6 m 3 /MWh to cooling about 1600 m 3 /day , energy equivalent to a 25.000 inhabitants city When dry cooling is applied it is required ~3% higher investment and causes ~3% lower overall efficiency WET/DRY COOLING AT CSP Wet cooling tower Indirect dry cooling

CSP+D JUSTIFICATION

Design point :
12 th September
Location: Palomares (Almeria, Spain)
DNI: 1990 kWh/m 2 year
24 hr operation at the design day
Radiation at solar noon of design day = 915,9 W/m 2
In all cases , net power and water production are the same: 50 MW and 46,615 m3/day
Net power cycle :
Net combined power + water efficiency was calculated as the ratio between net produced power and total solar power input (preheater, evaporator and superheater):
Normal direct radiation at design day in Palomares (Almería, Spain) CONSIDERED HYPOTHESIS

SOLAR STEAM CYCLE + RO
Solar (Euro)trough field:
Collectors per row = 2
Number of rows = 685
Total aperture area = 746,650 m 2
Considered hypothesis :
Net power production: 50 MW
Water production: 46,615 m 3 /day
24 h plant operation
Exhaust steam @ 42ºC
Net combined Power + Water efficiency: 29.2% Power plant cooling requirements: 100 %

Total aperture area = 1,000,620 m 2
STEAM CYCLE + TVC-MED (#1)
24 h plant
operation
Motive flow @ 17 bar
Net combined Power + Water efficiency: 21,7% Power plant cooling requirements: 52,5 %

Net combined Power + Water efficiency: 26,2% STEAM CYCLE + TVC-MED (#2)
24 h plant
operation
Motive flow @ 4 bar
Power plant cooling requirements: 45,3 %

SOLAR STEAM CYCLE + LT-MED
24 h plant
operation
Net combined Power + Water efficiency: 27,7% Power plant cooling requirements: 0 %

CSP+TVC-MED ANALYSIS Overall CSP+D efficiency (%) Thermal Power to the cooling system (power block, MW th ) Suction flow of exhaust turbine steam at 42ºC (0.082 bar)

FINANCIAL STRATEGIES Electricity cost would be a function of the water cost: the reduced efficiency of the power cycle should be compensated by the water production but the electricity can be subsidized by water cost or vice versa Power Cost LEC (€/kWh) Water Cost LWC (€/m 3 ) Water is subsidized by power cost Intermediate strategy Power is subsidized by water cost

WATER & ELECTRICITY COSTS Analysis realized over ANDASOL 1 plant (50 MW PTC Solar Power Plant, Spain) FLAGSOL GmbH

CSP+D JUSTIFICATION

PLATAFORMA SOLAR DE ALMERIA PSA is the biggest and most complete existing facilities to the research, testing and development of solar technologies and applications PSA is a Large European Research Installation of Scientific Excellence. PSA is a public research center belonging to the CIEMAT focused on concentrated solar processes and technologies CIEMAT is the Spanish scientific institution devoted to energy and environment

PLATAFORMA SOLAR DE ALMERIA

CSP+D TEST BED AT PSA 14-effects MED Plant Double Effect Absorption Heat Pump Rankine power cycle simulator

14-effects MED Plant Steam cycle simulator CSP+D TEST BED AT PSA

CSP+D experimental facility at Plataforma Solar de Almeria:
Max. power: 500 kW
Max. temperature: 550ºC
Max. pressure: 100 bar
Number of ejectors: 4
CSP+D TEST BED AT PSA

CONCLUSIONS
Seawater desalination by means of solar energy is a very promising applications due to the usual coincidence, seasonal and geographical, of water availability limitations and high solar irradiation.
It is essential to achieve an energy and water efficiency optimization to reduce as much as possible investment costs.
Besides Reverse Osmosis is today the leading desalination technology, there is room to the use of thermal desalination technologies integrated into solar steam power cycles.
The optimization of this integration is not yet defined, as specific ideas and concepts must still be developed.
Multi-Effect Distillation is a mature & reliable technology and constitute, today, the best option to the integration of solar thermal desalination processes in dual (water & power) plants.

Thank you very much for your attention

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CSP Training series : solar desalination (2/2)

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