This Small Business Innovation Research (SBIR) Phase I project proposes to create a novel low-cost micro-turbine engine that will revolutionize small-scale distributed power generation. The end goal is to install the generator onto residential HVAC systems to provide combined heat and power (CHP) for single-family homes. The engine will generate 1kW of electricity and the excess heat will be used for space heating and water heating, resulting in more efficient use of thermal energy. Currently there are no commercially available low-cost micro-turbine CHP systems that operate in this power range. The objective of this Phase I work is to demonstrate the feasibility of building a low-cost yet efficient micro-turbine by combining innovative morphologies with conventional materials and manufacturing technologies. The broader/commercial impacts of this research is to enable distributed generation at unprecedented power density and cost effectiveness, making it accessible for residential consumers. Customer adoption of combined heat and power (CHP) technologies is very low due to the lack of systems with a reasonable payback period. CHP systems powered by the proposed micro-turbine have a 75% reduction in upfront cost and 90% reduction in volume compared to existing systems. A small, cost effective and efficient CHP system will help families reduce monthly utility bills, provide peak hour load-leveling for power grid utilities, and reduce annual CO2 emissions by 1 ton per household. The proposed technology has significant market potential; beyond a multi-billion dollar residential CHP market with an enormous customer base are other applications in distributed generation.
The major results of this NSF SBIR Phase I project include the creation of a robust and efficient software tool for designing the basic geometries and blades for a micro-turbine, validation of the design tool against published numerical results, and the demonstration of compression and power extraction by turbomachinery components that are designed using the in-house software. The design tool is able to accept user inputs for the desired power output, rotation rate, and overall size for the micro-turbine, and return a set of geometries with estimated performance characteristics. In terms of geometry, the software gives back the blade angles and blade lengths for the compressor and turbine. In terms of performance, the software estimates the total fuel usage, the engine component efficiencies, and sources of power loss due to viscous and heat leakage effects. Unlike complicated numerical simulations, this software tool gives back a viable design within seconds and can be used to rapidly iterate on potential geometries. Nevertheless, numerical simulations are still required. A portion of this project was spent on validating the design tool using published numerical results for similar micro-turbines as well as in-house computational fluid dynamics (CFD) simulations. Good agreement was obtained when comparing these sets of data. Furthermore, CFD results were then used to fine tune compressor and turbine blade shapes to achieve the desired flow properties. The rest of the Phase I effort was dedicated to experimental validation of the proposed micro-turbine architecture and the design software. A compressor test rig and a turbine test rig were constructed, and the performance characteristics for the compressor and turbine prototypes were benchmarked in the test rigs. Good agreement was obtained for the turbine tests with some observed discrepancy between theory and experiment, but CFD was used to identify the cause of the discrepancy, which was related to the radial flow geometry and the need to fine tune blade geometries. This is now done for all future blade designs. The compressor tests were very successful, with theoretical and experimental results that were in excellent agreement. The major broader impact of this research and development project is in demonstrating the feasibility of designing and manufacturing commercially viable micro-turbines for power generation. The proposed engine architecture allows micro-turbines to be mass-manufactured using assembly-line infrastructure, which is unprecedented in the industry today. This will bring down the cost of micro-turbines, and bring micro-turbine products as well as their advantages – portability, reduced maintenance, fuel flexibility – to the market. Cost-effective micro-turbines have a variety of applications, including remote power generation for industrial purposes, portable power generation for consumers, and ultimately combined heat and power (CHP) for residential applications. The advantage of portability will allow faster deployment of emergency power generators for first responders and disaster relief. A CHP system uses fuel, such as natural gas, to generate electricity, but the waste heat is also utilized in space and water heating. The eventual CHP product will enable consumers to be more independent from the power grid and reduce the carbon footprint of homes by increasing their overall energy usage efficiency.
