Hydrogen technologies are increasingly important for a number of future aerospace and terrestrial applications. The Austrian Research Centers (ARC) are presently developing an innovative hydrogen tank system based on a combination of hollow microspheres and chemical hydrides, promising very high storage densities up to 10 weight % (wt%) at ambient pressures and temperatures. ARC is also active in developing micro energy converters based on micro turbines and Stirling engines to use waste heat and exhaust for improving the overall efficiency for a number of applications. Furthermore the present paper discusses a concept that utilizes a micro energy converter together with a micro combustion module that enables a micro power generator with very high power-to-weight ratios. In addition an overview of energy-related developments is presented that is specifically suitable for aerospace and demanding terrestrial applications.

https://people.fh-burgenland.at/jspui/bitstream/20.500.11790/320/1/2008%20-%20IECEC.pdf

Development of Innovative Hydrogen and Micro Energy Solutions at the Austrian Research Centers

As in the development of the transistor and integrated circuit, scale reduction combined with mass production can bring unprecedented affordability to space propulsion systems. Clusters of chemical micro-rocket engines, developed using MEMS process technology, can offer affordable, highly reliable, very precise, high power density propulsion for in-space and planetary surface systems. They provide a significant alternative to conventional rocket propulsion approaches. In addition to much lower production costs, the cluster concept offers improved mission reliability, lower weight, and increased spacecraft design flexibility such as distributed propulsion concepts which can reduce spacecraft weight. A single liquid bipropellant rocket engine-on-a-chip, approximately 20 mm square by 5 mm, can provide 310 lbs of thrust at a thrust-to-weight ratio of about 1000:1. The specific impulse will approach the theoretical value achievable for the propellants. Each engine chip includes a thrust chamber, nozzle, turbopumps, valves, and sensors, all made in a MEMS foundry from wafers of silicon and similar materials. The wafers are batch-processed with multiple engines produced on each wafer set. This can result in high uniformity among engines and low unit cost, given sufficient levels of production. Since “one engine suits all”, full-scale production qualities would be high even with modest numbers of spacecraft so equipped. Quality would be ensured as it is in the semiconductor industry through rigorous process control and inspection. In this sense, thrust becomes a true commodity for the spacecraft designer and operator. Such small, standard propulsion modules can rapidly be adapted to new missions’ needs by changing cluster sizes and arrangements Thus, once developed for and proven in one application, MEMS micro-rocket engines will quickly migrate to new applications since most of the development investment will have been made.

The Commoditization of Space Propulsion: Modular Propulsion Based on MEMS Technology

Waste heat is a primary source of energy loss in many applications. A number of developments around a micro rocket engine at the Austrian Research Centers (ARC) promise innovative energy recovery and micro power generation solutions. Here we focus on the investigation of micro technologies for application in HVAC (heating, ventilating, and air conditioning) systems. The use of μ-scale turbine expanders for work recovery in transcritical CO2 heat pump processes has been identified as most interesting and promising for the application in HVAC cases. One of the main drawbacks of transcritical CO2 heat pumps is the lower COP (coefficient of performance) compared to conventional heat pump systems which originates from the non isothermal heat rejection in the gas cooler. This drawback can be compensated by utilizing the pressure difference between the high pressure and low pressure part of the heat pump for work recovery. This is feasible as the pressure difference is considerably larger in case of CO2 heat pumps compared to conventional systems. Work recovery can be realized by substituting the expansion valve between the high and low pressure side by an expansion machine. Due to the low flow rate of the working fluid, the turbine type is based on the Pelton turbine with specific two phase flow turbine blades. In addition to the turbine part a magnetic coupling, miniature bearings and a small scale generator are important parts of the system. Thermodynamic simulations showed an absolute microturbine power yield between 60 W and 150 W for a 2 kW heating system.Copyright © 2009 by ASME

Development of a µ-Scale Turbine Expander for Energy Recovery

X-ray Lithography: fundamentals and applications

Micro power converters for energy recovery are increasingly important for a number of future applications. The Austrian Institute of Technology (AIT) is presently developing an innovative μ-scale turbine expander for work recovery in transcritical CO2 heat pumps. The main drawback of a lower COP (coefficient of performance) of transcritical CO2 heat pumps compared to conventional heat pump systems can be compensated by utilizing the pressure difference between the high pressure and low pressure part of the pump for work recovery. Work recovery can be realized by substituting the expansion valve between the high and low pressure side by a Pelton turbine with specific two phase flow turbine blades. In order to increase the power output, the generator was integrated into the turbine to reduce the friction losses and hence increase the overall efficiency. An important aspect is that the generator is directly connected with the high pressure part of the turbine. One part of the project is the optimization of the turbine geometry via simulation tools. The paper will give an overview about our microturbine development as well as a comparison of the power output of each turbine generation. Furthermore the present paper discusses a concept that utilizes our microturbine together with a micro combustion module that enables a micro power generator with very high power-to-weight ratios based on green fuels.Copyright © 2010 by ASME

IMPROVED µ-SCALE TURBINE EXPANDER FOR ENERGY RECOVERY

TASC/INFM, Sincrotrone Trieste (ELETTRA), and Mechatronic GmbH have started the design of a microturbine powered with compressed gas to be used as an electrical generator in a micro/nanosatellite. The research is funded by ESA for the realization of a liquid bipropellant micro-rocket engine that uses a micro-turbine and micro-pumps in order to pressurize the propellants. The turbine rotors have been fabricated with LIGA technology and die sinking Electro Discharge Machining. LIGA is well adapted to the production of high aspect ratio microstructures with very steep and well polished side walls and it does not limit the choice of material to silicon and derivative but offers the possibility to fabricate the turbine in metallic compounds. Moreover it has been found that LIGA, when coupled with EDM, is an optimum technique to obtain enbloc rotors with small diameter and high aspect ratio blades. The first step of the process is the fabrication of an X-ray mask containing a set of turbine rotors. The mask has been used on the ELETTRA deep X-ray lithography beamline to expose millimeter thick PMMA sheets glued on metallic substrates. After development the substrate is selectively electroplated with copper. The negative tone structures are then used as microelectrodes in a following EDM process. This further step allows obtaining turbines made of every conductive material. In particular we machined

http://www.researchgate.net/profile/Martin_Tajmar/publication/269224662_Design_and_Fabrication_of_Microturbine_Rotors_for_Small_Power_Generation/links/55d2090708aec1b0429dcd0e.pdf

Design and Fabrication of Microturbine Rotors for Small Power Generation

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Design and Fabrication of Microturbine Rotors for Small Power Generation