Sodium Thermal Electrochemical Converter (Na-TEC) Power Block for Distributed CSP

SETO CSP Program Summit 2019 Sodium Thermal Electrochemical Converter (Na-TEC) Power Block for Distributed CSP

Shannon K. Yee, Assistant Professor energy.gov/solar-office Georgia Institute of Technology SETO CSP Program Summit 2019 Project Summary Goal: Develop a dual-stage modular sodium thermal electrochemical converter (Na-TEC) heat engine power block with an estimated efficiency (ηT) of 51.3%, which can be potentially integrated with either a small- scale dish solar or large-scale heliostats and parabolic trough CSP. Key Advantages 1. High second law efficiency (>90% of the Carnot limit) 2. High specific power (up to 0.2 kW/kg) 3. Closed system operation with no moving parts 4. Scalable to multiple power levels (100 W -10 kW) 5. Amenable to cogeneration using rejected heat

Year 1 Year 2 Year 3 SETO CSP Program Summit 2019 2 Operation of Na-TEC: Single- vs. Dual-stage

Tint Na e- Vapor Pressure (~5 kPa) Na

Na+ e- e- e- Na+ 4 5 stage stage - - Electrolyte (A1) Cathode, 1 Electrolyte (A2)

3 Anode, 2 6 HeatIn - + + - Dual e Na Na e Single

Na Cathode, 2 Na Th Tc Vapor Pressure Anode, 1 Vapor Pressure (~95 kPa) 2 (~0.1 Pa) 7 8 Single-stage Heat Engine 1 Heat In Heat Out

The performance of the dual- stage device will be compared Limia et al., J. Power Sources (2017) against a single-stage Na-TEC

SETO CSP Program Summit 2019 3 Key Technical Challenges and Solutions

SS 253 MA Alpha-Alumina 1. Beta’’-Alumina Solid Electrolyte (BASE) fabrication

2. Metal to Ceramic joint

BASE

Partnered with Ionotec, Ltd. (United Kingdom) They have expertise in BASE fabrication and metal to Ceramic join using thermocompression bonding process.

SETO CSP Program Summit 2019 4 Key Technical Challenges and Solutions (cont’d) 3. Passive pumping demonstration

Test rig for demonstration

Experiments are currently in progress to demonstrate passive pumping concept

SETO CSP Program Summit 2019 5 Four Potential Impacts

• This power block can be deployed for both: • Lower costs (6 cents/kWh-target ü Small-scale dish solar (displacing dish Stirling) depending on the region, at an ü Large-scale heliostats and parabolic trough estimated cost of < $900 for kWe CSP unit

7.5 ¢/kWhe

6.4 ¢/kWhe

• Cogeneration of heat and power: Suitable for • This technology is well suited for CHP applications dry air-cooling

SETO CSP Program Summit 2019 6 Project Team & Facilities

• Alexander Limia (Grad student) • Jong Ha (Grad student) • Abhishek K. Singh (Postdoctoral Fellow) • Peter A. Kottke (Sr. Research Engineer) • Andrey Gunawan (Research Engineer II) • Andrei G. Fedorov (Co-PI) • Seung Woo Lee (Co-PI) • Shannon K. Yee (PI) • Scalable Thermal Energy Engineering Laboratory • Heat Lab (heat.gatech.edu)

SETO CSP Program Summit 2019 7 SETO CSP Program Summit 2019

Additional slides

energy.gov/solar-office SETO CSP Program Summit 2019 Scenario 1: CSP + Na-TEC + Fuel

! ~ 34 %

On Sun

Off Sun

SETO CSP Program Summit 2019 9 Scenario 2: CSP + Na-TEC + Batteries

! ~ 25 %

On Sun

Off Sun

SETO CSP Program Summit 2019 10 Scenario 3: CSP + Na-TEC + Direct Heat Storage

! ~ 43 %

On Sun

Off Sun

SETO CSP Program Summit 2019 11 Scenario 4: CSP + Na-TEC + Hybrid Storages

! ~ 29 %

On Sun

Off Sun

SETO CSP Program Summit 2019 12 Capital Cost of CSP–Na-TEC Systems in Four Scenarios

Batteries are expensive 16.00 15.00

14.00 13.00 12.00 11.00 10.00 KPBNa- TEC(USD/Watt) power block cost 9.00 ReceiverKREC (USD/Watt) cost 8.00 Lowest KEESBattery (USD/Watt) cost 7.00 ThermalKTES (USD/Watt) energy storage cost 6.00 KDISHSolar (USD/Watt)dish cost

Capital cost ($/Watt) Capital cost 5.00 KSPSite (USD/Watt) preparation cost 4.00

3.00 2.00 1.00 - Direct heat CSP + Fuel (no CSP + Batteries CSP + Thermal CSP + Batteries + storage) Energy Storage Thermal Energy Storage storage can be SETO CSP Program Summit 2019 competitive 13 LCOE Comparison

• LCOE comparison of 4 considered scenarios 7.5 • Current fuel price – 1 cents/kWh 6.4 cents/kWhe cents/kWhe • Discount rate variability – 3 to 10%

• Fuel is having lowest LCOE but direct heat storage is also prices competitive

SETO CSP Program Summit 2019 14 LCOE Comparison – including future fuel price

• LCOE comparison of 4 considered scenarios

• Current fuel price – 1 cents/kWh

• Discount rate variability – 3 to 10%

• Fuel is having lowest LCOE but direct heat storage is also prices competitive

For future fuel prices – similar LCOE between the SETO CSP Program Summit 2019 scenarios of using fuel and direct heat storage 15