Reversible Counter-Rotating Turbomachine to

Enable Brayton-Laughlin CycleJim Kesseli - Brayton Energy, LLC

Choon Tan - Massachusetts Institute of Technology

Develop a near perfect reversible gas turbine engine for a

pumped thermal storage cycle.

Total project cost: $2.78M

Length 30 mo.

Project Vision

Pumped Thermal-Electric Storage: Sensitive to Imperfections

A Brayton cycle generator (gas turbine) combined with a Brayton cycle heat pump

https://www.bloomberg.com/news/articles/2017-07-31/alphabet-

wants-to-fix-renewable-energy-s-storage-problem-with-salt

Pumped thermal storage combines a

Brayton cycle generator with a Brayton

cycle heat pump. The energy storage is

captured in the hot and cold fluid storage

tanks.

The Brayton team worked for 3 years

developing high efficiency, but separate

Brayton heat pump and generator

turbomachines for Google-X (2015-2018).

(illustration)

Brayton’s ARPAe Project strives to greatly

simplify the conventional two turbomachine

design, developing a single ultra-high

efficiency turbomachine.

The Team

Brayton Energy, Hampton, NH

▸Turbomachinery for Advanced Energy Systems

– High efficiency gas turbine design

– Low emission combustion

– Compact, high temp

heat exchangers

– Renewable Energy;

Concentrated Solar Power,

Next-Gen Nuclear

Role: Theoretical aerodynamics,

multi-parameter optimization.

Mechanical design and test.

Massachusetts Institute of Technology, Cambridge, MA

▸MIT Gas Turbine Lab

– Established in 1947,

focused on the

advancement of

propulsion systems and

turbomachinery.

– Advanced theoretical

and computational

research.

Role: Detailed treatment of

aerodynamic losses in the

turbomachine.

March 13, 2019 Insert Presentation Name2

Objectives: Improved Turbomachinery & Secondary Losses

‣ Two goals

– Round trip efficiency: Elevate from low 50%’s to over 63%

– Make economic gains: Pathway to cost of $500/kWe, $50/kWh

‣ Program Execution: Parallel development: Analysis & Test

3Insert Presentation NameMarch 13, 2019

Phase Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

Theoretical aerodynamics

Meanline modeling

CFD iterations

Test Rig Design

Fabrication Simulation Test Model validation

MIT Theoretical Loss models Simulation and CFD

Bench Test

(300 kW)

50 MW

design

Q10

Challenges and Potential Partnerships

‣ Biggest Challenges:

– An isentropic embodiment yields 100% RTE, but a conventional turbomachine

and heat exchanger package approaches 50%. Innovation is necessary

– Achieve ultra-high isentropic efficiency from a reversible turbomachine

– Thermal storage; solar salt is the best-known hot storage media, and hexane

is the best cold sink media (~200K) - Alternatives sought

‣ TEA Goals: Develop a partnership

– MALTA Inc. – a recently launched start-up. Well-financed by Google-X and

Breakthrough Energy Ventures

– Other emerging international developers of pumped thermal-electric storage