Joint Demonstration and Verification of the Performance of Microturbine Power Generation Systems Utilizing Renewable Fuels with the U.S. EPA's Environmental Technology Verification Program
Tim Hansen | Southern Research Institute
Objectives of the Demonstration
The objective of this demonstration was to provide a credible, independent, third party evaluation of the performance, economics, and environmental impacts of the Ener-Core Powerstation™ (FP250) technology in a landfill gas (LFG) energy recovery application at a U.S. Department of Defense (DoD) site. Ener-Core Power, Inc. was formerly known as Flex Power Generation, Inc. The evaluation was designed to provide sufficient data to allow end-users, purchasers, and others to determine the feasibility of the technology at DoD sites and other applications. Success factors that were validated during this demonstration include energy production, emissions, and emission reductions compared to alternative systems, economics, and operability, including reliability and availability.
The FP250 is a unique power plant that is able to generate electric power using low energy content gas or vapor while emitting low levels of atmospheric pollutants. The FP250 integrates a modified conventional micro-turbine (Ingersoll Rand MT250, now manufactured by FlexEnergy Energy Systems) of proven design with a proprietary gradual thermal oxidizer in place of the conventional turbine’s combustor. Gradual oxidation is the 1- to 2-second conversion of a dilute fuel air mixture to heat energy, carbon dioxide (CO2), and water. Compared to traditional combustion processes, which occur in milliseconds, the Ener-Core oxidation process is more gradual. The FP250 is able to operate using low heating value fuel sources (theoretically as low as 15 British thermal units [BTU]/standard cubic feet [scf]) that would not support operation of conventional gas turbines or reciprocating engines, which require a minimum fuel heating value of 300-500 BTU/scf.
Key outcomes from the demonstration at Fort Benning, Georgia, include:
- The FP250 met or exceeded the objectives for energy production, low oxides of nitrogen (NOx) emissions, non-methane organic compound (NMOC) destruction efficiency, and greenhouse gas (GHG) reductions associated with its use. NOx emissions were much lower than the California Air Resource Board (CARB) 2013 standard for distributed generation.
- Exhaust carbon monoxide (CO) emissions were comparable to typical emissions from gas turbines and reciprocating engines in LFG service, but did not meet the demonstration plan objective. CO emissions at the oxidizer outlet do meet CARB 2013 standards, and a new system configuration currently offered by Ener-Core is designed to meet the CARB standard for CO.
- Based on a life cycle cost analysis for a typical FP250 installation, the economics for the FP250 are on par with competing distributed generation and LFG to energy technologies, but did not meet demonstration plan objectives at current electricity prices at Fort Benning.
- The system is capable of fully automated and unattended operation, but this capability was not fully demonstrated at Fort Benning.
- System availability and reliability did not meet the demonstration plan objectives during operations at Fort Benning. This was due, in part, to site-specific circumstances extraneous to the FP250, including insufficient LFG supply and unusually frequent grid outages. Ener-Core worked closely with Southern Research (Southern) throughout the demonstration to adapt the FP250 to overcome these difficulties, and these efforts led to a number of enhancements to the commercial FP250 including the capability for supplemental fuel blending and full island mode operability. Ener-Core maintains that, had these modifications been fully implemented at the start of the demonstration, system availability and reliability would have been within Ener-Core specifications (90-95%).
Installation managers should understand that the FP250, like other turbine-based technologies, requires a steady fuel supply with minimum total energy content of about 3.4 million (MM)BTU/hour (higher heating value). That is, the FP250 is only capable of operating near 100 percent of rated capacity and has little or no turn-down capability. In addition, the FP250 does not tolerate excessive thermal cycling. As with larger frame size industrial gas turbines, continuous 24/7 operation is recommended and the number of restarts over the system lifetime should be minimized to avoid excessive maintenance. It is important that a sufficient, continuous fuel supply be verified during site selection. It is also important to verify the reliability of the grid interconnect (if any) at candidate sites.
The FP250 is undergoing minor modifications to improve reliability and operability. These modifications include:
- Prevention of turbine wear due to particulate breakthrough from the gradual oxidizer.
- A new startup protocol utilizing the warmer only.
- Full automation of system startup.
- The capability to continue operation in ‘island mode’ to prevent unnecessary shut downs due to transient grid faults (applicable to sites where there may be frequent grid interruptions).
Ener-Core has conducted testing and/or engineering evaluations for each of these modifications at their engineering development facility and maintains that these modifications will allow the system to operate unattended with high reliability (>90%) and minimal unplanned downtime. The performance of these modifications was not verified during this demonstration.
Due to the system’s low emissions, minimal noise, and small footprint, Southern does not expect permitting or other site approvals to present a significant obstacle to implementation at most sites. For this demonstration, permitting and required approvals required minimal effort.
Points of Contact
Mr. Tim Hansen
Southern Research Institute
Energy and Water
SERDP and ESTCP