ABENER. Challenges in Thermal Energy Storage Systems. Abener Engineering and Construction Services. Presented by: Mark Cowell

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Cornelius Ferguson
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1 ABENER Abener Engineering and Construction Services Challenges in Thermal Energy Storage Systems Presented by: Mark Cowell Engineering and construction for sustainability

2 Challenges in thermal energy storage systems US Annual Average DNI 1

3 Challenges in thermal energy storage systems Concentrated solar power (CSP) DNI not available 24 hrs DNI not consistant throughout seasons Determine DNI on hourly basis for all seasons 2

4 Challenges in thermal energy storage systems CSP limitations Phoenix, AZ 3

5 Challenges in thermal energy storage systems CSP limitations Availability does not meet demand Phoenix, AZ 4

6 Challenges in thermal energy storage systems CSP limitations long warm up times to avoid thermal shock 5

7 Challenges in thermal energy storage systems CSP limitations Availability Demand Warm up <24hrs Changes hourly Changes seasonally Often does not match availability Possible DNI reject Not quick Thermal Energy Storage (TES) can overcome limitations 6

8 Challenges in thermal energy storage systems TES advantages Availability Demand Warm up Beyond daylight hours Any season Reduced Thermal Fatigue Higher value energy during peak demands Before daylight Maximum use of DNI for power production 7

9 TES model 8

10 Challenges in thermal energy storage systems TES design considerations System commissioning Nitrogen blanketing Materials of construction Tank and foundation design Heat exchanger design Molten salt pumps Heat loss 9

11 TES design considerations Logistics of salt delivery 126,000 mtons Single supplier production capacity Modes of transportation Manufacturing location Packaging materials Receiving deliveries Secured storage areas (on site vs off site) DHS theft risk 400 lbs STQ 10

12 TES design considerations Salt melting Storage to preprocessing transfer logistics Preprocessing Melting Transfer to permanent storage tanks Preheating to avoid thermal stress Bring up to melting temp 20% TES construction/commissioning schedule 11

TES design considerations N2 blanketing 60:40 sodium nitrate to potassium nitrate Impurities differ based on production process Chlorides, sulfates, nitrites, carbonates Exposure

13 TES design considerations N2 blanketing 60:40 sodium nitrate to potassium nitrate Impurities differ based on production process Chlorides, sulfates, nitrites, carbonates Exposure to air (moisture) leads to potential corrosion Slight positive pressure N2 blanket Wicking affect in vapor space salt blockage of PSV s, block valves, small nitrogen lines, etc. 12

14 TES design considerations MOC Many materials compatible with nitrate salts Level of impurities High operating temperatures Published mechanical properties Resulting thickness may require post weld heat treatment Cost of salt quality vs cost of tank material, treatments, schedule 13

15 TES design considerations Tanks and foundations No API-650 for operating temps No ASME for low pressure, flat bottom Analyze stresses Typical static and pressure loadings Typical seismic and wind loadings Temperature gradient stresses Tank sizing for storage capacity and no. of units Max tank height due to pump length limitations Heel of non-working salt and related cost Foundation considerations Structurally sound at elevated temps Sufficient anchorage to prevent tank uplift Good insulator Minimize heat loss from salt Minimize heat to soil 14

Number of units Hours of storage at specific capacity Solana 6 hrs at full capacity Type of unit (S&T vs P&F) Size

16 TES design considerations TES HEX Typical considerations of heat exchangers MOC based on salt quality MOC based on temperature Hot and cold end temperature approaches Total efficiency depends on charging and discharging performance Number of units Hours of storage at specific capacity Solana 6 hrs at full capacity Type of unit (S&T vs P&F) Size of HEX dictates special attention to thermal shock Large mass of metal retains heat Differential with incoming fluid 15

17 TES design considerations TES HEX Heat loss affects thermal efficiency Large surface area due to size Supports Avoidance of salt pluggage Drainability Piping design Operation decisions (drain vs isolate full) Size considerations Fabrication / testing Shipping Placement 16

18 TES design considerations Salt pumps Design considerations: Vertical turbine vs vertical centrifugal MOC of all wetted parts / high temps Sealing system / salt wicking and pluggage Bearing cooling systems / high temps Warm up and cool down To/from ambient temperature During drop in and pull out of hot system Removal of pumps with salt inside Minimum submergence requirements 17

19 TES design considerations Heat loss Affects overall power production and efficiency Potential for pluggage Tank walls, roof, bottom, foundations, hex, piping Heat tracing Insulation Installation 18

20 TES design considerations Seville test facility Sanlucar La Mayor, Spain Operating since 2009 Single unit encompassing tanks, heat exchanger, pumps, etc. Lessons learned where things went wrong Lessons learned on equipment selection where things went right 19

Contents EN 14015:2004 (E) page

Contents EN 14015:2004 (E) page Contents page Foreword... 11 1 Scope... 12 2 Normative references... 13 3 Terms, definitions, symbols and abbreviations... 15 3.1 Terms and definitions... 15 3.2 Symbols... 19 3.3 Abbreviations... 21 4