Power cycle development

• Steam cycles dominant for

>300 yrs, mostly Rankine

• Gas Brayton cycles –

catching up last 50 years

• Organic Rankine Cycles

(ORC) relatively recent

2

Why a new power cycle?

• Steam

– Good efficiency at lower turbine inlet

temperature

• Low compression work (pumping incompressible liquid)

• High expansion ratio (large work extraction / unit mass

of fluid)

– 2-phase heat addition limits turbine inlet

temperature

– Expansion into 2-phase region = blade erosion

– Corrosion, water treatment issues3

Why a new power cycle?

• Gas Brayton cycles

– Good fuel-power conversion efficiency

– Require high (combustion) turbine inlet temperatures for efficient operation

– Compression work large fraction of developed power

• ORC

– Best solution at low temperatures, dry expansion

– Working fluids are more difficult to handle – generally require secondary transfer loop, limits turbine inlet temperature

4

Characteristics of an ideal power cycle

• Good utilization of available heat

– High expansion, low compression work

– Direct coupling to heat source

• Benign working fluid

– Non-corrosive, non-toxic, thermally stable

– Dry expansion to avoid erosion

• Low capital cost

• Low operation & maintenance (O&M) costs

5

Supercritical CO2 meets these characteristics

sCO2 cycle history

• 1960’s – Feher proposes use of a recuperated closed-loop sCO2 based power cycle– Recognized that CO2 properties allow for Brayton-style cycle,

but with Rankine-like compression work

• 2000’s – MIT, Sandia, others consider sCO2 nuclear power cycle– Three “Supercritical CO2 Power Cycle” Symposia

– 2008, Sandia builds small sCO2 test loop for turbomachinery (simple and recompression cycles)

• 2007 – Echogen founded with vision of commercializing a sCO2 waste heat recovery heat engine– 2009, builds ~ 250kWe demonstration simple cycle system

– 2011, begins construction of 7.5MWe commercial system

6

sCO2 cycles – Simple recuperated cycle

Good heat utilization at low heat source

temperature

Compact equipment set

2-phase

Supercritical fluid

Superheated

vapor

Subcooled

liquid

7

High density fluid = compact equipment:

Heat exchangers

8

>15MW

>300m² heat transfer area

~13000kg

Core ~ 1.5 x 1.5 x 0.5 m

Comparable S&T:

>850m²

~50000kg

Shell ~ 1.2m diameter x 12m length

High density fluid = compact equipment:

Turbomachinery

9

10MW sCO2 turbine

10MW steam turbine

Non-condensing expansion

Condensing expansion

Simple single-phase exhaust heat exchangers

• Boiling process in steam systems limits maximum fluid temperature, requires

multiple pressures to achieve close approach to exhaust temperature

• ORC systems require intermediate heat transfer loop, plus boiling heat transfer

Constant temperature

boiling process

Continuous

temperature increase

10

CO2 cycles – The challenge with a simple

recuperated architecture

11

Heat addition

Expansion workCompression work

Low pressure ratio cycle => recuperation => can limit ∆T of heat addition

CO2 cycles – Simple cycle limitations

Highly recuperated cycle limits performance

at higher heat source temperature12

Heat addition

CO2 cycles – Cascading can increase

available ∆T

Heat extraction limitations of simple

recuperated cycle mitigated

13

Heat addition

CO2 cycles – recompression yields high heat

to power efficiency, but very low ∆T

14

Heat addition

Recompression cycle specifically designed

for low ∆T applications (nuclear, CSP)

Applications of the sCO2 cycle

Geothermal (Low T, thermosiphon)

Concentrated Solar Thermal (CSP)

(High T, low DT)

Exhaust & waste heat recovery (Moderate T, high DT)

Topping cycle (High T, low DT)

250 kW demonstration system: initial field tests

completed at American Electric Power (AEP)

16

Designed for full access

and ease of maintenance

Shop packaged / modular design

for ease of installation

Commercial size demonstration

unit at AEP’s test facility

Measured performance in line with cycle model

predictions – 140 hours, 93 turbine starts

250 kW demonstration system: long-term tests

at Akron Energy Systems (AES) during 2012

17

Hardware transferred and delivered by truck Cooling tower installation

Heat engine delivery and placement System installation now underway

First “commercial-scale” system at

~7.5MW, utilizes commercial technology

18

From Sandia National Laboratory report

First 7.5MW system is currently in fabrication

19

Subsystem and component testing planned for 3Q through 4Q 2012

Full system installation and testing in early 2013

System installation comparison:

7.5MW steam vs. sCO2

20

Smaller installation footprint compared to a HRSG/steam system for

gas turbine bottom cycling

Gas turbine Steam sCO2

sCO2 = Higher power at lower CAPEX for

CCGT applications

21

• High output power + low cost + low O&M = low LCOE

• sCO2 the clear solution for gas turbine heat recovery

DP HRSG sCO2

sCO2 + LM2500

DP-HRSG + LM2500

LM2500 Simple Cycle

SP-HRSG + LM2500

Inst

all

ed

co

st

Ne

t p

ow

er

(kW

e)

Ambient temperature (°C)

Levelized Cost of Electricity (LCOE) ─

The Key Performance Metric

• Lower capex of sCO2 system provides major advantage

• Faster startup times (~20min vs 45-90 min for steam) = higher average output in peaking applications

• Lower footprint, zero water usage in dry-cooled applications

22

Summary

• sCO2 cycles have significant advantages in several

applications over steam

– Good thermodynamic performance

– Low installed capex

– Favorable LCOE

• Broad range of applications under consideration

• Waste heat recovery first commercial application

– Demonstration system proved feasibility

– First full-scale application in 2013

23