Delivering Energy From The Best Source
Delivering Energy From The Best Source

Our Team

SEG offers competitive renewable baseline energy generation with significant fuel hedging benefits by identifying, designing, implementing and managing comprehensive sustainable energy programs. SEG was cofounded by Garen Ewbank, Duane Harman, Garry Sexton, Justin Stonehocker, Andrew Frenier and David Thomison with the intention of providing Utilities, Investors, and Energy Managers with energy management solutions using the best available expertise, technology, products and services wrapped around the always on premier renewable energy, Ground Source Geothermal. 

David Thomison, Managing Director Utilities


As the former treasurer of AEP-PSO, David brings extensive Utility experience to SEG. In addition to his vast Utility experience David has excelled at providing direction for a corporate venture firm, and has led the financial and/or M&A function for several high growth companies. David Thomison has served on the Board of Directors of several high growth companies during which time one of these companies grew from approximately $35 million to over $100 million in revenues in just 24 months. His in-depth industry expertise includes energy, software, informational services, and financial. 


David has a B.S. in Industrial Engineering & Management from Oklahoma State University, where he was honored as a Top Ten Senior, and a Master of Business Administration from Harvard University. 

Garry Sexton, Managing Director, International


Garry Sexton has worked internationally in the HVAC-R/Geothermal industry for the past forty years. Prior to joining SEG LLC, he served as the CEO of Innergie Technologies Incorporated, with offices located in Seoul, South Korea and Shanghai, China. Garry has participated in the development of multiple renewable and sustainable energy projects utilizing innovative technologies and has extensive experience with conceptual engineering design, project management and installation execution for projects throughout the USA, Canada, China and South Korea. His projects have ranged from industrial, agricultural and residential to large skyscrapers and include both private industry and US Department of Defense installations including more than 200 geothermal projects of 500 ton or more and 4 of the world’s largest geothermal installations.  


During his career Garry’s responsibilities have included management of US and international sales and engineering teams, training and certification of system designers and mechanical engineers. His career includes working with WaterFurnace International and ClimateMaster International in both domestic and international sales engineering, training director, international sales director and most recently CEO of Innergie Technologies.


Garry is actively involved in SAME (Society of American Military Engineers) and served five years as the Post Chapter Vice President for South Korea. He is also actively involved with several charitable organizations, including HOPE Schools China, a group dedicated to the development and construction of primary and secondary schools in rural regions of China, and GSI – Good Shepherd International a group that assists North Korean refugees by providing long term living facilities and educational opportunities.

Duane Harman PE, CGD, Managing Director, Engineering


Duane has extensive experience in HVAC, Geothermal and Plumbing Design.  He has worked on a wide variety of project types, including commercial, industrial, residential, medical, and educational facilities. Duane is responsible for all aspects of mechanical and plumbing design for projects from schematic design to completion and has successfully completed projects up to $160 million in total construction costs.  Duane also has extensive energy modeling and analysis experience and is an expert in ground source heat pumps and exchangers.


Professional Engineer, OK; Mechanical, 20875, 2002
Certified GeoExchange Designer, CGD, 2005


Master of Business Administration, Oklahoma City University, 2001
Bachelor of Science, Mechanical Engineering, Oklahoma State University, 1997

Garen Ewbank, Managing Director, Strategic Vision


Garen is a Lifetime Member of the Association of Energy Engineers (AEE) and is a Certified Energy Manager (CEM), Certified GeoExchange Designer (CGD), Certified Carbon Reduction Manager (CRM), Certified Energy Auditor (CEA), Certified Business Energy Professional, (CBEP), and a Certified Sustainable Development Professional (CSDP) with the AEE. Garen is also a full Member of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). 


Licensed to drill water wells and ground source borehole, Garen has extensive HVAC/R, ground source drilling and installation, wireless systems and project management experience. Garen is an accredited installer and a Trainer (in all disciplines) with the International Ground Source Heat Pump Association (IGSHPA). Garen is a member of the IGSHPA Training and Marketing/Membership committees and past advisory council and current board member. He is active on the Training and Marketing/Membership committees; and sub-committees of the Certified GeoExchange Designer, (CDG) and Vertical Loop Installers (Drillers). Garen is a Trainer for IGSHPA with the Vertical Drillers, Installers, and Certified GeoExchange Designer programs. 


Garen graduated with a B.S. in Industrial Engineering and Management from Oklahoma State University.

Justin Stonehocker, Managing Director, Technology


During his career with ES2-Tulsa, Justin has managed all aspects of building automation controls and energy solutions.  Justin has spent the past 15 years in the Building Automation and Energy Management industry, and has lobbied for energy efficiency and sustainability since early 2000.  


His experience covers the HVAC, geothermal, and building automation industries. Justin has been responsible for the successful completion of over 450 projects in the HVAC Energy Management Systems market. Justin holds a B.A. in Graphics Design/Marketing from the University of Central Oklahoma. He currently serves as Web Director for the Northeast Oklahoma chapter of ASHRAE and is the former Co-Chair of the Green Schools Challenge for USGBC Oklahoma.

Andrew Freiner Managing Director, Special Projects.


Andrew brings significant industry experience in product development and installation of proprietary ground source heat exchangers. He has applicable experience in structural engineering, maintenance programs, field maintenance, and heavy maintenance for Boeing 757 wings, Airbus A300 pylons, and Douglas DC10 horizontal stabilizers. Andrew has worked on implementing composite connecting systems for floorboards on the A300, Component testing, including design of testing fixtures, operation of thermal chamber, MTS tensile and fatigue testing, analysis, and final test reports publications. He has worked with consolidation of engine operation specific trial testing procedures, across multiple engineering and technical groups to create a single unified testing process.


During his tenure with Kelix Heat Transfer System, LLC. Andrew serves as the V.P. and C.T.O. and helped to develop Thermacouple(R) GLE products and technologies, which allow engineers to economically construct small, medium and large scale ground loop heat exchanging (GLHE) systems having the highest performance characteristics possible in any given deep Earth environment, while meeting the heat transfer rate (HTR) requirements of high-performance buildings served by geothermal heat pumps, chillers and HVAC systems of any size thermal load.


Andrew is a graduate of the Oklahoma State university, where he received his B.S. with a major in Mechanical Engineering. Andrew is a Certified Energy Manager (CEM) with the AEE.

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