Armin Buchroithner

Improving kinetic energy storage for vehicles through the combination of rolling element and active magnetic bearings

The demand for short term energy storage providing high power for electric and hybrid-electric vehicles is increasing dramatically. Stationary flywheel energy storage systems (FESS) are established as uninterruptible power supply (UPS) and represent an emerging market. In contrast, mobile FESS are currently only used in few applications such as motor sports. To enable a wider use in personal and public transportation the lifespan of the flywheels bearings needs to be increased significantly. This paper presents an alternative approach to extend the lifespan of the flywheels bearings by using a combination of rolling element and active magnetic bearings (CREAMB).

Development and Prototype Testing of Low-Cost Lightweight Thin Film Solar Concentrator

A low-cost rigid foam-based concentrator technology development program was funded by the DOE SunShot Initiative to meet installed cost goals of

Mobile Flywheel Energy Storage Systems: Determining Rolling Element Bearing Loads to Expand Possibilities

75/m^2 vs. current costs of ∼

Decentralized low-cost flywheel energy storage for photovoltaic systems

200–250/m^2. Phase 1 of the project focused on design trades and cost analyses leading to a cost-optimized self-powered autonomous tracking heliostat concept with a mirror surface area in the 100m^2 range. In Phase 2 30-year accelerated testing of the mirror modules based on ReflecTec film with 94% specular reflectivity bonded on composite foam substrate were initiated and completed in Phase 3. The tests with 15 coupons showed optical performance degradation of less than 5% in specular reflectance following 30-year equivalent UV testing and other abuse testing such as acid rain, bird dropping, thermal cycling, etc. A small scale prototype (3m×2m) heliostat design based on modular truss elements with removable mirror modules was developed in detail. In this phase components such as the dual-axis actuators were sized and selected based on wind load requirements and pointing accuracy demands were completed. Finite Element analyses for the mechanical structure with mirror modules were performed using three separate commercial codes — ANSYS, COMSOL and SolidWorks to validate the optical errors induced by wind loads on the structure up to 35 mph. Results indicated that the RMS deflections contributed to less than 0.4 mrad pointing error. Dynamic response of the heliostat indicated that the first 5 eigenmodes were in the 17–20 Hz range. The individual structure elements such as the trusses and c-rails were fabricated locally and assembled with the mirror facets in the lab for initial fit check and testing. The nine mirror facet surface errors were characterized using photogrammetry and verified using Reverse Hartmann techniques and showed to be in the order of 1 mrad or less. A three-level controller (main, gateway and heliostat) was architected and built. Tracking of the sun is done using NREL’s Sun Tracking Algorithm implemented in the gateway controller. Target-pointing vectors are calculated for each heliostat and conveyed wirelessly to the individual heliostat controllers for actuating the azimuth and elevation motors. The power subsystem consisting of solar panels and a battery provide 24V for the actuators and controller boards. The system was sized to provide adequate power for a period of 5hrs of operation when power is not available. Initial calibration will be performed with on-site camera tracking the sun’s image on a target located approximately 52m from the heliostat. Testing of the heliostat pointing under calm and windy conditions will be done to demonstrate overall performance that meet DOE targets of 4 mrad under 27 mph winds. Commercialization efforts are underway to transition the design to the commercial sector. The project is well on its way to approaching overall cost targets and current estimates are approximately S90–110/m^2 and lower costs can be achieved with alternates to the film we have identified.

Estimating costs of heliostat production at high volumes based on a small-scale prototype

Efficient energy storage is the key to modern hybrid or zero emission vehicles and low carbon mobility in general. Compared to conventional storage technologies like batteries, flywheel energy storage systems (FESSs) offer various theoretical advantages, such as high cycle life, no capacity fade over time, temperature independence, easy determination of state of charge, and complete recyclability. However, the special operating conditions of FESSs-such as vacuum, high rotational speeds, and high gyroscopic reactions, etc.-make bearing design a complex and crucial endeavor. This article describes methods of determining loads for rolling element bearings in automotive FESSs. An overview of FESS technology is given, followed by the discussion of an analytic, numeric, and empiric approach, including a detailed comparison of the different methods. Furthermore, the concept of a test bench investigating flywheel behavior in a resilient mount is described, and its results regarding the design of an FESS-tovehicle mount are discussed in depth.

Designing an autonomous power system for a stand-alone heliostat

This publication demonstrates that flywheel energy storage systems (FESS) are a valid alternative to batteries for storing energy generated by decentralized rooftop photovoltaic systems. The increasing number of private PV arrays calls out for high energy storage capacities in order not to overload the grid. Despite being the current storage technology of choice, chemical batteries are still too expensive and have certain disadvantages compared to FESS, such as capacity fade over time and currently still difficult recycling. Within a research project at the Graz University of Technology a feasibility study for a low-cost, low-loss FESS was conducted. Energetic dimensioning was performed using actual PV power and electric load data recorded at a building in Austria with 6 apartment units. A low-cost flywheel system with an energy content of 5.0 kWh and 2.2 kW maximum rated power using a steel rotor and economic off-the shelf components was designed and investigated. Self-discharge of the proposed FESS design was significantly reduced using a cast silicone bearing seat, which allows supercritical rotor operation. Axial bearing loads were compensated by nearly 100% via repelling permanent magnets allowing drastic down-sizing of the bearings and further reduction of torque loss. The concept was validated by a small-scale test setup, which showed promising results. Finally, an improved design option is compared to the initially proposed FESS in terms of costs and self-discharge.

Optimal system design and ideal application of flywheel energy storage systems for vehicles

Reducing the costs of heliostats is crucial for the worldwide deployment of Concentrated Solar Power (CSP). CSP offers a number of advantages over photovoltaic at large scale power generation, such as lower cost and the option of thermal energy storage. However, the costs of a power tower plant are dominated by heliostats, which are usually 50% of the entire facility. NASA5s Jet Propulsion Laboratory was awarded funding by the DOE SunShot Initiative to develop a low-cost, rigid foam-based solar concentrator to meet installed cost goals of S75/m2 vs. current costs of -

History and development trends of flywheel-powered vehicles as part of a systematic concept analysis

200-250/m2. The design approach was validated by building and testing of a small-scale (6m2) heliostat prototype. Based on the findings of this prototype costs estimates for high production volume using industrial manufacturing technologies were conducted. The findings of these studies as well as lessons learned from manufacturing of the prototype are presented in this paper.

Improving Kinetic Energy Storage for Vehicles through the Combination of Rolling Element and Active Magnetic Bearing

Concentrated Solar Power (CSP) offers a number of advantages over photovoltaic at large scale power generation, such as lower cost and the option of thermal energy storage. However, the costs of a power tower plant are dominated by heliostats, which are usually 50% of the entire facility. NASA5s Jet Propulsion Laboratory was awarded funding by the DOE SunShot Initiative to develop a low-cost, rigid foam-based solar concentrator to meet installed cost goals of S75/m2 versus current costs of

Systematische Analyse von Hybridfahrzeugen mit Schwungradspeicher unter Erfassung von Entwicklungstendenzen

200-250/m2. One of the key features of the newly developed design is the stand-alone power system based on PV-panels and a Li-Fe-battery, which reduces operation and installation costs. The approach was validated by building and testing of a small-scale (6m2) heliostat prototype. The design process and findings are described in detail.