Indirect Dry Cooling using Recirculating Encapsulated Phase Change Materials

Introduction Transformative Technology Design Technical Risks

Team Organization and Members

ParameterNETL

Case 13 (wet)

ARPA-E Dry

Cooling

Proposed Dry

Cooling

Cooling water in temp,

°C15.6 29 22.6

Steam condensation

temp, °C38.4 51.7 38.4

Ambient wet bulb, °C 10.8 10.8 10.8

Ambient dry bulb, °C 15 15 15

Dry cooling ITD, °C - 36.7 23.4

PCM melting temp, °C - -21.6 &

35.6

• Rotary EPCM Heat Exchanger

- Innovative Category 1B technology that integrates encapsulated

phase change materials (EPCMs) with a high-surface-area mesh

rotary heat exchanger (HX).

- Novel rotary EPCM HX with separate regions of heat absorption

(from condenser hot water), water drainage, and heat rejection (to air)

for desired thermo-fluidic performance.

- Reduced ITD, lower pressure drop with nearly 4 times increase in air-

side heat transfer coefficient compared to ACC.

- Indirect air-cooling heat exchanger downstream from a surface

condenser for effective heat dissipation.

- Lab-scale tests, simulation, 50 kWth prototype demonstration at

Evapco’s weather chamber & techno-economic feasibility w/ industrial

partners (e.g. Evapco, WorleyParsons, Southern, Duke).

Strategy:

- Passive Water Recapture

Strategies: hydrophobicity &

surface structures;

- Active Water Removal

Strategies: shear-driven “air-

knife” & induced vibrations.

Strategy:

- High conductivity & low thickness polymer;

- Nano-additives for enhanced conductivity;

- Numerical & experimental optimization of

porous geometry.

• Scalable manufacturing for long lifetime

• Key Potential Benefits

- Reduced initial temperature difference (ITD) to as low as 20°C;

- Increased air-side heat transfer coefficient by up to 4 times;

- Reduced pressure drop and operational cost of primary steam;

- Reduced capital cost and footprint by up to 30%, reduced

subfreezing concerns.

Recirculating EPCM for low-cost, compact, indirect dry cooling tower

CHANGING WHAT’S POSSIBLE

• Performance and Cost Targets

- Air-side heat transfer coefficient hair >120 W/m2K, pressure drop

ΔPair /L < 120 Pa/m, and COP >100;

- Negligible water loss (water loss rate < 1%);

- Manufacturing cost < $75/kWth. LCOE increase relative to wet

cooling ≤ 5%.

PI: Jessica Shi, Electric Power Research Institute

• Transformative Technology

- Highly porous EPCM structure for effective heat

transfer at low pressure drops;

- Cost-effective manufacturing of EPCM modules

with long lifetimes (>30 years);

- Disruptive rotary EPCM HX design adapted from

existing rotary systems for 24-7-365.

Polymer shell

PCM core

EPCM rejects

heat to the air

during freezing

• Elimination of water loss

• Research Approaches

• The EPRI Team: Dr. Jessica Shi, Dr. Mukesh Khattar, Mr. Ram

Narayanamurthy, Dr. Sean Bushart, Mr. Kent Zammit, Mr. Richard

Breckenridge

• The Drexel Team: Dr. Ying Sun, Dr. Matthew McCarthy, Dr. Grace Hsuan

• University of Memphis: Dr. Sumanta Acharya

• The EVAPCO Team: Mr. Jean-Pierre Libert, Mr. Joe Vadder, Mr. Mark Huber

• The WorleyParsons Team: Mr. Qinghua (Tim) Xie, Mr. David Brubaker, Dr.

James Simpson

• Maulbetsch Consulting: Dr. John Maulbetsch

• Advisors: from Southern Company, Duke Energy, ARVOS, Inc., Intralox.

Strategy:

- Thin-wall high-density polyethylene

(HDPE) tubes for EPCM mesh;

- 3D printing, injection molding for highly

porous meshes manufacturing;

- Finite Element Method and experiments

for cycling analysis.

),,(Re/Nu 2 airPCMairair fkdh

),,(Re/2 1

2

, airairairairp fUpC

T

C

T

BAt

loglog

Comparison with wet cooling & ARPA-E indirect dry cooling

Cooling mechanism: Heat is transferred from condenser water to the

air using short-term thermal energy storage in a rotating EPCM HX.

Log

Stress

(MPa)

II

III

Log – Failure Time (hr)

III

Poorly

stabilized

I – Creep rupture (ductile failure)

II – Slow crack growth (brittle failure)

III – Oxidation Degradation

I

Figure x – Three failure stages in a logarithmic

plot of stress versus time

Lo

g S

tres

s (M

Pa)

• EPCM with low thermal and fluidic

resistances

0.0 0.5 1.0 1.5 2.0 2.50

1

2

3

4

5

6

k eff /

kb

ase

Nanoadditive volume fraction, (%)

Solid Eicosane/xGNP

Liquid Eicosane/xGNP

Nan's model, kGNP

=98W/mK

Warzoha & Fleischer 2014

(Solid IGI 1230A/xGNP)