Water Use in Concentrating Solar Power (CSP)

Transcription

1 Water Use in Concentrating Solar Power (CSP) Craig Turchi and Chuck Kutscher National Renewable Energy Laboratory Golden, Colorado, USA

2 Outline Solar Resource Potential CSP Technology Overview - Parabolic Troughs - Power Towers - Dish / Engine Systems - Comparison with Photovoltaics (PV) Announced Projects Water Consumption - Wet vs. dry cooling

3 Solar Resource Screening All Solar Resources 1. Start with direct normal irradiance (DNI) estimates derived from satellite data. 2. Exclude locations with less than minimum DNI threshold. 3. Exclude culturally and environmentally sensitive lands, urban areas, lakes and rivers. 4. Exclude land with greater than 1% to 3% average land slope. Locations best for Development 5. Exclude areas of less than 1 km 2 6. Locate near load centers and transmission corridors

4 Site filtering example - USA olar > 6.75 kwh/m 2 /day Land Exclusions Slope & Area Exclusions

5 CSP Resource Potential - USA Assumptions : Solar Resource 6.75kWh/m2/day Land use 5 acre/mw Land slope < 1% Capacity factor 27% Water, urban areas, and environmentally sensitive lands excluded USA Total Land (thousand km2) CSP Potential Capacity (GW) Energy (TWh)

6 CSP Technologies and Market Sectors SP w/ Storage (Dispatchable) Parabolic Trough Power Tower Linear Fresnel SP w/o Storage (Non-Dispatchable) Dish/Engine

7 Parabolic Trough

8 Parabolic Trough Power Plant w/ 2-Tank Indirect Molten Salt Thermal Storage Trough Field 390 C Salt Storage Tanks

9 54 MW Luz Solar Electric Generating Systems ine SEGS Plants built (California, USA)

10 4 MW Acciona Nevada Solar One evada, USA

11 50 MW Andasol 1 with 7-hr Storage Andalucía, Spain

12 Power Tower (Central Receiver) Different design approaches: Direct Steam Generation Abengoa PS10 (Spain) Abengoa PS20 (Spain) BrightSource (USA/Israel) esolar (USA) Molten Salt Solar Two (USA demo) SolarReserve (USA) Air Receiver Jülich (Germany)

13 Molten Salt Power Towers Ability to store hot salt allows molten salt Towers to run at high capacity factors. Hot Salt 565 C Cold Salt 288 C Conventional steam turbine & generator Steam Generator Condenser Heliostat Field

14 Power Tower Pilot Plants 5 MWe esolar California, USA 6 MW thermal BrightSource Negev Desert, Israel

15 Dish Systems Dish/Stirling: Pre-commercial, pilot-scale deployments Concentrating PV: Commercial and precommercial pilot-scale deployments Modular (3-25kW) High solar-to-electric efficiency Capacity factors limited to <25% due to lack of storage capability

16 Tessera 25kW Dish/Stirling 1.5 MW demo in Phoenix under construction

17 Technology Comparison Trough Power Tower Dish / Engine Utility scale (>50 MW) x x x x Distributed (<10MW) x x Energy Storage (dispatchable) x Water use for cleaning x x x x Water use for cooling preferred preferred Technical maturity medium low low low to high Cost (nominal, with 30% ITC) /kwh x PV?? /kwh* * Utility scale only, rooftop PV higher.

18 Outline Solar Resource Potential CSP Technology Overview - Parabolic Troughs - Power Towers - Dish / Engine Systems - Comparison with Photovoltaics (PV) Announced Projects Water Consumption - Wet vs. dry cooling

19 Solar Plants and announced Projects Plant or State Capacity (MW) Technologies SEGS I thru IX 354 Trough Nevada Solar One 64 Trough Kimberlina pilot 5 Linear Fresnel (Ausra) Sierra pilot 5 Power Tower (esolar) Utility-scale PV 32 Three sites in CO and NV Utility-scale PV 3500 Sites in CA, NM, NV, TX, CO, others California 6390 Trough, Tower, Fresnel, Dish/Stirling Nevada 484 Trough Arizona 1147 Trough, Dish/Stirling New Mexico 92 Tower Texas 27 Dish/Stirling Florida 75 Trough/NGCC Total ~ 12,000 See

20 Outline Solar Resource Potential CSP Technology Overview - Parabolic Troughs - Power Towers - Dish / Engine Systems - Comparison with Photovoltaics (PV) Announced Projects Water Consumption - Wet vs. dry cooling

21 Water Use per Land Area 3.5 Acre-ft / acre per year CSP (wetcooled) CSP (drycooled) Alfalfa Cotton Fruit Trees Golf Courses Sources: CSP: Reducing Water Consumption of CSP Electricity Generation, Report to Congress Crops: Blaney, Monthly Consumptive use of Water by Irrigated Crops & Natural Vegetation, Golf : Watson et al., The Economic Contributions of Colorado s Golf Industry: Environmental Aspects.

22 Water Usage of Solar Technologies Gal / MWh Trough (wet cooled) Trough (dry-cooled) Dish/Stirling PV Collector Cleaning Boiler Makeup Cooling Total Reference: Concentrating Solar Power Commercial Application Study: Reducing Water Consumption of CSP Electricity Generation, Report to Congress, U.S. DOE, 2009 Values representative; specific usage varies by plant.

23 Steam Rankine Power Cycle Trough Field Salt Storage Tanks Thermal cycle efficiency is proportional to 1 T low T high

24 Wet- and Dry-cooled Condensers

25 Dry-cooled systems are inherently less efficient Wet-cooled systems are limited by wet-bulb temperature: T condensate = T wet-bulb + (~25 F) Dry-cooled systems are limited by dry-bulb temp: T condensate = T dry-bulb + (~40 F) Condensate temperature can be ~35 F higher with a dry-cooled system.

26 Optimum turbine design depends on anticipated condensing temperature(s) Reference: Concentrating Solar Power Commercial Application Study: Reducing Water Consumption of CSP Electricity Generation, Report to Congress, U.S. DOE, 2009

27 Hybrid Cooling Hybrid systems have wet- and air-cooled condensers (ACC) installed in parallel. Wet system used to reduce load to ACC on hottest days.

28 Hybrid Designs look appealing Hybrid estimated to use 85% less water with only 2% drop in energy output (but capital cost is higher too). Reference: Concentrating Solar Power Commercial Application Study: Reducing Water Consumption of CSP Electricity Generation, Report to Congress, U.S. DOE, 2009

29 Solar plants may optimize to a larger ACC than coal plants 1. Switching to an ACC (dry-cooling) requires a larger solar field and turbine to achieve same MWe output 2. Solar field is expensive relative to the ACC; therefore investing in a bigger ACC may be more effective than building lots more solar field. 3. Big ACC and extra solar field yields more power during off-peak (vs. wet-cooled system). This helps offset lower efficiency.

30 A large ACC can reduce the cost of dry-cooling Design parameter Wet-cooled baseline Dry-cooled with large ACC Design point net power output 1 1 Design point steam turbine efficiency 1-5% Turbine size (gross output) 1 +2% Solar field size 1 +8% Design point parasitic loads 1 +17% Total installed cost 1 +8% O&M cost 1-3% Annual net energy output 1 +3% Annual Revenue 1 +3%? Levelized Cost of Energy (LCOE) 1 +3% to +10% Dry-cooled plant annual energy output increases because parasitic loads fall quickly at offdesign conditions, allowing the larger solar field/turbine to generate more power. Reference: WorleyParsons, Analysis of Wet and Dry Condensing 125 MW Parabolic Trough Power Plants, Sept. 2009

31 Cooling Comparison Summary Type Advantages Disadvantages Wet Dry (ACC) Hybrid Lowest cost Low parasitic loads Small footprint Best cooling, especially in arid climates No water consumption No water treatment required Lower O&M costs Less water consumption Potentially less expensive than dry-cooling Maintain good performance during hot weather High water consumption Water treatment and blowdown disposal required Plume can cause problems More expensive equipment Higher parasitic loads Larger footprint Poorer cooling at high dry-bulb temps (turbine derate) Complicated system involving wet and dry cooling Same disadvantages of wet system, but to lesser degree

32 Conclusions Parabolic Trough and Power Tower technologies prefer to use wet cooling (lower cost, higher efficiency). Cooling accounts for over 90% of water consumption at a wet-cooled plant. Dish/Engine and PV systems use water only for collector cleaning. Dry-cooling can reduce water consumption by 90%, but increases capital cost and decreases plant efficiency, especially on hot days. The penalty for switching to dry cooling can be minimized by optimizing the turbine and size of the air-cooled condenser (ACC). Hybrid wet/dry systems can reduce water consumption by 50% to 80% while maintaining plant efficiency on hot days. Cost impact of switching to dry or hybrid cooling will be site specific, depending on solar technology, water availability, climate, and market economics. Likely to raise LCOE by 3% to 10%

33 Thank you! Craig Turchi Concentrating Solar Power Program