ARPA-E held a workshop on the topic of power technologies on February 9, 2010 in Arlington, VA. The objectives of this workshop were to gain a deeper understanding of those areas and technologies that have the highest potential to meet DOE's goal of developing the technical foundations necessary to improve the utilization of energy in power technologies. This workshop served as an opportunity to bring together thought-leaders from diverse technical communities to collectively develop new directions in methods, components, and systems related to electrical energy conversion.

The meeting proceedings are summarized below. View the workshop agenda (pdf).

Speakers and Presentations:

1. Ward Bower, Sandia National Laboratory: "Photovoltaic Systems: Power Technology Status and Needs" (pdf) 2. Keith Evans, Kyma Technologies, Inc.: "Bulk GaN Materials for Next Generation Power Electronics" (pdf) 3. Mark Johnson, ARPA-E: "Semiconductor Materials and Structures for Power Electronics" (pdf) 4. Fred Lee, Virginia Tech: "Integrated Point-of-Load Converters" (pdf) 5. Dr. Arun Majumdar, Director, ARPA-E: "Advanced Buildings Workshop" (pdf) 6. John Palmour, Cree Inc.: "High Voltage Silicon Carbide Power Devices" (pdf) 7. David Perreault, MIT: "Research Needs and Opportunities in Power Electronics" (pdf) 8. Charles Sullivan, Dartmouth: "Power Magnetics: Emerging Technologies and Research Needs" (pdf) 9. Dr. Le Tang, Vice President & Head of Corporate Research Center, ABB Inc.: "High Voltage DC Technologies" (pdf)   Breakout Sessions:

During the workshop, participants broke into two sets of breakout sessions comprising of three topical group discussions per breakout session. The six topical areas were:

• Photovoltaic Technology: Power electronics requirements for emerging photovoltaic systems. The discussion included requirements for next-generation centralized inverters. The goal of the breakout was to generate component specifications that will facilitate large-scale deployment of photovoltaics. 
• Compact Power Conversion from PV to Solid State Lighting: Component requirements that support power conversion in a scalable, energy efficient technology platform. In particular the session sought to generate specifications for components that enable low-cost, efficient, highly functional LED drivers and compact module-integrated power converters. 
• Grid Scale High Voltage Transmission: The session explored the drivers for HV (>7.2kV) to UHV (>800 kV) transmission and the component technology required for dynamic connection in HV & UHV systems. 
• Power Converters Architectures: Circuit topologies for efficient DC/DC and DC/AC power conversion. Applications discussed included, but were not limited to, small-form factor converters for photovoltaics (e.g. module integrated converters) and solid-state lighting (advanced LED ballast). 
• Switch Technology: Materials and devices for efficient power conversion. The discussion included switch technologies that enable the above applications while retaining high efficiency and scalability for wide deployment. Switch materials considered included wide-bandgap semiconductors and novel Silicon based designs. 
• Magnetics Technology: Soft-magnetic materials and processes to support the applications above. Soft-magnetics considered included new alloys, thin-films, and nanoparticles for low-core losses at the relevant switching frequencies and form-factors for advanced power converters. 
• The goal was to gain a deeper understanding of those areas and technologies that have the highest potential to meet DOE’s goal of developing the technical foundations necessary to enable massive reductions in energy consumption in buildings. Each group responded to the respective breakout questions below with summary slides of their responses.

Questions or Discussion Topics:

Overarching Questions or Discussion Topics 1. What is the present state-of-art of these technologies and what is their performance and cost? 2. What are the technical challenges and barriers (circuit breakers, valves, switches, control)? 3. In each identified topical area, what are the critical technologies that are required? What are the unique/transformational approaches to overcome these barriers/challenges? 4. What are specific performance and cost metrics for solid-state technologies?      a. Power converters at the module level, residential scale, and commercial scale      b. Integrated power converters for at the module and sub-module level for PV      c. Integrated power converters for SSL (dimmable & non-dimmable)      d. Solid-states switches for grid-scale high and ultra-high voltage conversion 5. Which technologies need to be developed for the:       a. Near-term       b. Mid-term       c. Long-term 6. What is the strategy to move from one to the next? 7. What are the challenges and barriers for the adoption of these technologies? 8. What level of investment would be required to develop and deploy these technologies? What is the return on investment?   Photovoltaic Technology (pdf) Session Chair: Ward Bower, Sandia National Lab  1. What are the critical performance metrics for power converters at the module-scale, residential-scale, and commercial-scale?      a. Reliability (15, 20, 25 years, etc)      b. Power and voltage levels      c. Efficiency (90%, 95%, etc.)      d. Pluggability (5 minute, 20 minute replacement?)      e. Communication & Control (building integration, grid-tied, etc)      f.  Cost      g. Distortion      h. Operating temperature      i.  Surge protection 2. Which component technologies (solid-state switches, magnetics, electrostatics, thermal management) need to be developed for the:       a. Near-term       b. Mid-term       c. Long-term 3. What are the optimal locations for inverter integration?      a. Module integrated (module back, module frame, etc)      b. Residential      c. Small- and large-commercial 4. For small- and large-commercial PV, what are optimal approaches (siting, converter technology, etc) to MPPT? 5. Is there an opportunity for exploiting reactive power in the inverter? What time scale is desirable and feasible (ms)? At what power scale would have a direct impact? 6. Fire safety for PV systems is an emerging concern. What can be done within the PV installation & power converter to mitigate fire safety risks?   Compact Power Conversion: From PV to Solid State Lighting (pdf) Session Chair: Satish Prabhakaran, GE 1. For power converter technology (DC/DC), what are the drivers for integration?     a. Packaging costs     b. Footprint     c. Efficiency     d. Ease of use 2. For power converter technology (DC/DC) what are the barriers for integration?     a. Performance     b. Yield     c. Thermal management     d. Design complexity 3. For power converter technology for photovoltaic inverters (DC/AC), what are the potential drivers [1a-d), module mismatch/MPPT, pluggability] for integration? What are the barriers to integration? 4. What are the optimal sites for integration of converters with PV modules? Module back, frame, etc. 5. Which component technologies (solid-state switches, magnetics, electrostatics, thermal management/packaging technology) need to be developed for integrated power conversion:      a. 48V DC to 220 V AC      b. 600 V DC to 220 V AC 6. For power converter technology for SSL drivers (AC/DC), what are the potential drivers [1a-d, form-factor] for integration? What are the barriers to integration? 7. Which component technologies (solid-state switches, magnetics, electrostatics, thermal management/packaging technology) need to be developed for integrated power conversion:      a. Dimmable 10 W drivers     b. Dimmable 50 W drivers 8. What is the appropriate target for SSL driver integration?     a. Controller + power electronics     b. Power electronics + magnetics     c. Power electronics + electrostatics   Grid-Scale High Voltage Transmission (pdf) Session Chair: Mark Johnson, ARPA-E  1. What are the drivers (performance, cost, cooling, installation, etc) for higher voltage solid-state valves? 2. What are the critical performance metrics for power converters at the HV and UHV scale?     a. Reliability (years?)     b. Power and blocking voltage for switches     c. Power and blocking voltage for valve stack     d. Efficiency (percent, etc.)(on resistance) 3. What are the technical challenges for switched HVDC transmission and distribution?     a. HV sub-transmission (33kV-115kV)     b. HV transmission (115kV – 800kV)     c. UHV transmission (800 kV and beyond) 4. Which technologies need to be developed for the:      a. Near-term      b. Mid-term      c. Long-term 5. What are the challenges and barriers for the validation and adoption of these technologies? 6. What level of investment would be required to develop and deploy these technologies? What is the return on investment?   Power Converters Architectures (pdf) Session Chair: David Perreault, MIT  1. For integrated PV inverters (8V/40W & 48V/240 W), what are the critical performance metrics for components?     a. Switches     b. Electrolytic capacitors     c. Magnetics     d. Control electronics and power switches 2. Which component technologies (solid-state switches, magnetics, electrostatics, thermal management) need to be developed for the:      a. Near-term      b. Mid-term      c. Long-term 3. For integrated SSL AC/DC (10W & 50W), what are the critical performance metrics?     a. Switches     b. Electrolytic capacitors     c. Magnetics     d. Control electronics and power switches 4. Which component technologies (solid-state switches, magnetics, electrostatics, thermal management) need to be developed for the:      a. Near-term      b. Mid-term      c. Long-term 5. What is the application space for switched-capacitor (magnetics-free) converters? What are the technical barriers, performance trade-offs? 6. What is the performance impact of micro-inverters (40 - 240W/ 48V to 220VAC) and rectifiers (10-50W) of not using electrolytic capacitors? What are alternative circuit topologies (high frequency effective ripple), alternative capacitors (thin film, fast ultracaps), and magnetics? 7. What level of investment would be required to develop and deploy these technologies? What is the return on investment? 8. What is the appropriate target for integration (at 10W (rectifier), 50W (rectifier/inv), 240W (inv))?     a. Controller + power electronics     b. Power electronics + magnetics     c. Power electronics + electrostatics   Switch Technology (pdf) Session Chair: Mark Johnson, ARPA-E  1. What are the critical performance metrics for switch components to support high switching frequency (>10 MHz) converters at 10 W (SSL), 50 W (SSL/PV), 250 W (PV), 3kW (PV), 300 kW (PV)?     a. Blocking voltage     b. Switching frequency     c. On resistance     d. Heat transfer     e. Reliability      f. Integration (lateral vs. vertical)     g. Cost 2. What are the critical performance metrics for switch materials for high switching frequency (>10 MHz) converters at 10 W (SSL), 50 W (SSL/PV), 250 W (PV)?     a. Mobility     b. Bandgap     c. Permittivity     d. Material quality (defect) 3. What are the critical performance metrics for switch materials for high blocking voltage (1kV, 10kV, 100 kV)?     a. Mobility     b. Bandgap     c. Permittivity     d. Material quality (defect) 4. What level of investment would be required to develop and deploy these technologies? What is the return on investment? 5. For power converter technology (AC/DC & DC/AC), what are the drivers for integration?     a. Packaging costs     b. Footprint     c. Efficiency     d. Ease of use 6. For power converter technology (AC/DC & DC/AC), what are the barriers for integration?     a. Performance     b. Yield     c. Thermal management     d. Design complexity   Magnetics Technology (pdf) Session Chair: Charles Sullivan, Dartmouth  1. What are the critical performance metrics for magnetic components for high switching frequency (>10 MHz) converters at 10 W, 50 W, 250 W, 3kW, 300 kW?     a. Core loss (eddy & hysteresis), winding loss (skin, proximity, gap, end)     b. Inductance     c. Size     d. Heat transfer     e. Cost 2. What are the critical performance metrics for magnetic materials for high switching frequency (>10 MHz) converters at 10 W, 50 W, 250 W, 3kW, 300 kW?     a. Conductivity     b. Coercive field/Hysteresis     c. Permeability     d. Saturation flux density 3. What are the unique critical performance metrics for integrated magnetic components for high switching frequency (>10 MHz) converters at 10 W, 50 W, 250 W? 4. For power converter technology (AC/DC & DC/AC), what are the drivers for integration?     a. Packaging costs     b. Footprint     c. Efficiency     d. Ease of use 5. For power converter technology (AC/DC & DC/AC), what are the barriers for integration?     a. Performance     b. Yield     c. Thermal management     d. Design complexity