Spark-Assisted HCCI Residential CHP

Achieve 40% electrical efficiency at 1 kWe by

transforming small internal combustion (IC) engine

efficiency through a systematic reduction of losses

Project Goal

Fed. funding: $2.6M

Length 36 mo.

Demonstrated over 34% brake thermal efficiency at 1 KW with

concept 1 configuration surpassing year 2 target of 33%

Current Technical Status

Dr. Rolf Reitz, Dr. David

Wickman, and Chris Wright

Wisconsin Engine Research Consultants (WERC)

(Lead and Engine Modeling)

Dr. Sage Kokjohn and Mike

Andrie

University of Wisconsin – Madison Engine Research

Center (Performance Testing and Air Handling)

Doug Shears and David

Procknow

Briggs & Stratton (Manufacturing and

Tech-to-Market)

Lloyd Kamo Adiabatics, Inc. (Coatings)

Technical Details and Data Approach

Key Technology Role in Reducing Losses

Compact combustion chamber with

high compression ratio

Improved expansion stroke energy

extraction

Long stroke and small bore Reduced heat transfer losses

Cooled EGR Reduced heat transfer and NOx

Advanced boosting Increased load to decrease role of friction

Advanced thermal barrier coatings Reduced heat transfer

Stoichiometric operation Enables low cost aftertreatment

Technology combination results in reductions in all major loss categories!

1

Technical Details and Data

• Analysis driven development approach (validated 1-D and 3-D

simulation) used to identify optimal design configurations

• Initial engine concepts designed • Concept 1 uses many production engine components to accelerate

engine testing with an engine close to the design study specifications

• Concept 3 is a clean sheet engine design based on the design study

• Both engines have optimized bore/stroke (<<1) and high compression ratio

• Concept 3 features increased tumble and optimized piston design to

reduce incomplete combustion

• Stoichiometric operation to enable use of three way catalyst

Concept 1 Concept 3

Displacement (cc) 71 70

Bore (mm) 39.5 40

Stroke (mm) 57.9 56

Bore/Stroke Ratio (-) 0.68 0.71

CR 17 18

Testing Status Complete Future

System Level

Developments

2

Technical Details and Data

• Engine testing of concept 1 configuration at 1 kW demonstrated

34% brake thermal efficiency

• 𝜆 = 1 operation (closed loop) with TWC installed

System Level

Developments

Concept 1 Engine

2400 rev/min

𝜆 = 1

MBT Spark Timing

3

Technical Details and Data

• Validated simulations show pathway to reach program targets

continue targeted loss reduction with concept 3 engine

System Level

Developments

Validation

Concept 3 Configuration

4

Technical Details and Data

• Operation at peak efficiency (maximum brake torque (MBT)) spark

timing possible over methane numbers from 65 to 100

System Level

Developments

Spark Timing

Margin

5

Technical Details and Data Concept 3 Engine

Development

6

Technical Details and Data

Engine Control Unit (ECU)

Low flow rate boosting system to

enable increased EGR

• Developed and tested pressure wave

supercharger (PWS) shows ability to achieve

over 1.3 bar abs. intake pressure at target

conditions

• Current engine testing shows

potential for minimal boost

requirement <1.15 bar abs.

passive devices may be possible

• Currently developing membrane

based charger

• Custom engine control unit developed by Woodward®

• Closed loop combustion phasing and AFR control

• EGR feedback based on intake/exhaust O2 sensors

Component Level

Developments

7

Technical Details and Data

Improved Thermal Barrier Coatings with Very Low Thermal Conductivity and

Heat Capacitance with Minimum Porosity

0.94

0.67

0.28

0

0.2

0.4

0.6

0.8

1

Plasma20YSZ

ToyotaSiRPA

RCCoating

Thermal Cond (W/m-K)

2630

1540

500

0

500

1000

1500

2000

2500

3000

Plasma20YSZ

ToyotaSiRPA

RCCoating

Heat Capacity (kJ/m3-K) @ 300°C

Coating after 476 hrs

of Engine Testing

Exhaust Valve Cylinder Head Piston

Component Level

Developments

• Compared to Yttria-stabilized zirconia

current coating has

‒ a factor of 5 reduction in heat

capacity

‒ a factor of 3 reduction in thermal

conductivity

• On engine durability testing has

completed over 400 hours with no

noticeable degradation

8

Tech-to-Market Strategy

mCHP Prime Mover PoC

GENSETS Project

Demonstrated 𝜂𝑒 ≥ 32%

Projected Cost ≤ $1000@10k/y

Projected Life ≥ 40,000 hrs

Yes

No

Exploit

component

technologies in

collateral markets

Continue

Development

for Production

Intent Design

Design,

Construct, and

Test

Proof-of-

Concept mCHP

Appliance

Dissolve

Project

Team

Pitch Concept

to potential

OEM partners. B&S activities

Evaluate

B&S as OEM

Lab

Reliability

Testing

Phase 2

mCHP

Development

Phase

3 Proto

Build

Pilot

Field

Deploy

Seek

Funding

Limited

Market

Intro

2018 2019 2020 2022

• Q8-Q12 testing supporting cost and efficiency tradeoff analysis

• Proceed to development of resCHP appliance with favorable results

Current program results have been favorable enough to ensure efforts

will continue to develop and exploit component technologies. 9

Details on Envisioned Product Offering

*Assumes 96% efficient generator and 3% thermoelectric recovery

per project FOA

Metric Program Target Current Status

(Prime Mover)

Target Product

(resCHP Appliance)

Power (kWe) 1 1 1

Fuel-to-Elec Eff. (%) 40 35.7* >33

Thermal (kWt/kWe) >1 TBD >1.25

Capacity factor (%) 99.9 TBD 99.9

System Cost ($) 3,000 CBI <1,000

System Life (years) ≥10 by design 10

Exhaust Emissions CARB Std TBD CARB Std

Sound (dB(A) @ 3 ft) ≤55 TBD ≤55

Methane Number Tol. >70 demonstrated ≤70

Maint. Interval (#/yr) ≤1 by design ≤1

O&M cost ($/kWh) ≤0.005 TBD ≤0.015

Maint. Labor (hr) ≤1 by design ≤1

System Mass (kg) ≤150 <50 ≤100

10

Current Challenges / Focus Areas

Key Focus Areas for 2018 Emissions Control (methane, CO, and NOx targets are very low)

Approach: Overall program has focused on stoichiometric operation to

enable use of a three-way catalyst. After treatment effort is evaluating catalyst

formulations for methane reduction. Control strategy will require dithering to

enable simultaneous reduction of methane, NOx (𝜆 < 1), and CO (𝜆 > 1)

Efficiency - Cost Tradeoff

Approach: Systematic quantification of efficiency cost tradeoff of individual

components (boost system, EGR, ultra-high CR, feedback control, etc…) to

enable detailed techno-economic analysis

System Integration and Endurance

Approach:

• Integration of thermal barrier coatings and passive boosting concept

• Endurance testing of concept 3 engine

Future: Technology extension to plug-in hybrid electric vehicles (range

extender) appears to be a natural transition

11