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Distributed Generation

Cogenra Solar, Inc.

Double-Focus Hybrid Solar Energy System with Full Spectrum Utilization

Cogenra Solar is developing a hybrid solar converter with a specialized light-filtering mirror that splits sunlight by wavelength, allowing part of the sunlight spectrum to be converted directly to electricity with photovoltaics (PV), while the rest is captured and stored as heat. By integrating a light-filtering mirror that passes the visible part of the spectrum to a PV cell, the system captures and converts as much as possible of the photons into high-value electricity and concentrates the remaining light onto a thermal fluid, which can be stored and be used as needed. Cogenra's hybrid solar energy system also captures waste heat from the solar cells, providing an additional source of low-temperature heat. This hybrid converter could make more efficient use of the full solar spectrum and can provide inexpensive solar power on demand.

Colorado School of Mines

Low-Cost Intermediate-Temperature Fuel Flexible Protonic Ceramic Fuel Cell Stack

The Colorado School of Mines is developing a mixed proton and oxygen ion conducting electrolyte that will allow a fuel cell to operate at temperatures less than 500°C. By using a proton and oxygen ion electrolyte, the fuel cell stack is able to reduce coking - which clogs anodes with carbon deposits - and enhance the process of turning hydrocarbon fuels into hydrogen. Today's ceramic fuel cells are based on oxygen-ion conducting electrolytes and operate at high temperatures. Mines' advanced mixed proton and oxygen-ion conducting fuel cells will operate on lower temperatures, and have the capacity to run on hydrogen, ethanol, methanol, or methane, representing a drastic improvement over using only oxygen-ion conducting electrolytes. Additionally, the fuel cell will leverage a recently developed ceramic processing technique that decreases fuel cell manufacturing cost and complexity. Additionally, their technology will reduce the number of manufacturing steps from 15 to 3, drastically reducing the cost of distributed generation applications.

Colorado School of Mines

High Efficiency, Low Cost & Robust Hybrid SOFC/IC Engine Power Generator

The Colorado School of Mines will develop a hybrid power generation system that leverages a pressurized, intermediate-temperature solid oxide fuel cell (SOFC) stack and an advanced low-energy-content fuel internal combustion (IC) engine. The custom-designed, turbocharged IC engine will use the exhaust from the anode side of the SOFC as fuel and directly drive a specialized compressor-expander that supplies pressurized air to the fuel cell. High capital costs and poor durability have presented significant barriers to the widespread commercial adoption of SOFC technology. In part, these challenges have been associated with SOFC high operating temperatures of 750-1000°C (1382-1832°F). This team will use a robust, metal-supported SOFC (600°C or 1112°F) technology that will provide greater durability, better heat management, and superior sealing over standard ceramic-supported SOFC designs. The modified diesel IC engine in a hybrid system provides a low-cost, controllable solution to use the remaining chemical energy in the fuel cell exhaust. The system will use the hot air and exhaust gases it produces to keep components running at the proper temperatures to maximize overall efficiency. The team will also develop supporting equipment, including a specialized compressor-expander and power inverter. The new system has the potential to enable highly-efficient, cost-effective distributed power generation.

Creare LLC

Closed-Loop 5-kWe Brayton-Cycle Microturbine with 38% Efficiency: Advanced Generator Technology Designed for Inexpensive Mass Production

Creare, in partnership with IMBY Energy, is developing a mass-manufacturable, recuperated, closed-loop Brayton-cycle microturbine that will provide 5 kW of electrical power for residential and commercial buildings. The waste heat from the device can be harvested for heating. Technical innovations in the system that are anticipated to enable high efficiency at an attractive cost include a diffusion bonded foil recuperator, a turbomachine with specialized hydrodynamic gas bearings, a binary working fluid mixture and flameless combustion.

FuelCell Energy, Inc.

Adaptive SOFC for Ultra High Efficiency Power Systems

FuelCell Energy will develop an adaptive, pressurized solid oxide fuel cell (SOFC) for use in hybrid power systems. Hybridized power generation systems, combining energy efficient SOFCs with a microturbine or internal combustion (IC) engine, offer a path to high efficiency distributed generation from abundant natural gas. Proof-of-concept systems have shown the potential of this hybrid approach, but component optimization is necessary to increase system efficiencies and reduce costs. Existing SOFC stacks are relatively expensive components, and improving their efficiency and robustness would enhance the overall commercial viability of these systems. This team's approach is to focus directly on improving SOFCs with hybrid integration as their end goal. Their adaptive cells will withstand the necessary pressure fluctuations, and the compact stack design aims to make the best use of heat transfer while minimizing leakage losses and maintaining high performance. The team will take a modular approach, building 2-5kW stacks that can be grouped together in a pressurized container. These modules can be added or removed as needed to suit the scale of the hybrid system, enabling a range of power applications. The baseline cell technology will also be modified through advanced materials that extend the useful life of stack and mitigate the harmful effects of contaminants on fuel cell performance. If successful, these adaptive, efficient, robust SOFCs could provide a path to greater than 70% efficiency when integrated into a hybrid system.

FuelCell Energy, Inc.

Dual-Mode Intermediate Temperature Fuel Cell: Liquid Fuels and Electricity

FuelCell Energy will develop an intermediate-temperature fuel cell that will directly convert methane to methanol and other liquid fuels using advanced metal catalysts. Existing fuel cell technologies typically convert chemical energy from hydrogen into electricity during a chemical reaction with oxygen or some other agent. FuelCell Energy's cell would create liquid fuel from natural gas. Their advanced catalysts are optimized to improve the yield and selectivity of methane-to-methanol reactions; this efficiency provides the ability to run a fuel cell on methane instead of hydrogen. In addition, FuelCell Energy will utilize a new reactive spray deposition technique that can be employed to manufacture their fuel cell in a continuous process. The combination of these advanced catalysts and advanced manufacturing techniques will reduce overall system-level costs.

Gas Technology Institute

Hybrid Solar System

Gas Technology Institute (GTI) is developing a hybrid solar converter that focuses sunlight onto solar cells with a reflective backside mirror. These solar cells convert most visible wavelengths of sunlight to electricity while reflecting the unused wavelengths to heat a stream of flowing particles. The particles are used to store the heat for use immediately or at a later time to drive a turbine and produce electricity. GTI's design integrates the parabolic trough mirrors, commonly used in CSP plants, into a dual-mirror system that captures the full solar spectrum while storing heat to dispatch electricity when the sun does not shine. Current solar cell technologies capture limited portions of the solar spectrum to generate electricity that must be used immediately. By using back-reflecting gallium arsenide (GaAs) cells, this hybrid converter is able to generate both electricity from specific solar wavelengths and capture the unused light as heat in the flowing particles. The particle-based heat storage system is a departure from standard fluid-based heat storage approaches and could enable much more efficient and higher energy density heat storage. GTI's converter could be used to provide solar electricity whether or not the sun is shining.

General Electric

Electrothermal Energy Storage with a Multiphase Transcritical CO2 Cycle

GE is designing and testing components of a turbine system driven by high-temperature, high-pressure carbon dioxide (CO2) to develop a more durable and efficient energy conversion system. Current solar energy system components break down at high temperatures, shortening the system's cycle life. GE's energy storage system stores heat from the sun in molten salt at moderate temperature and uses surplus electricity from the grid to create a phase change heat sink, which helps manage the temperature of the system. Initially, the CO2 remains at a low temperature and low pressure to enable more efficient energy storage. Then, the temperature and pressure of the CO2 is increased and expanded through a turbine to generate dispatchable electricity. The dramatic change in temperature and pressure is enabled by an innovative system design that prevents thermal losses across the turbine and increases its cycle life. This grid-scale energy storage system could be coupled to a hybrid solar converter to deliver solar electricity on demand.

George Washington University

Micro-Scale Ultra-High Efficiency CPV/Diffuse Hybrid Arrays Using Transfer Printing

George Washington University (GWU) and their partners will develop a hybrid CPV concept that combines highly efficient multi-junction solar cells and low-cost single-junction solar cells. When direct sunlight hits the lens array, it is concentrated 1000-fold and is focused onto the multi-junction solar cells. Diffuse light not captured in this process is instead captured by the low-cost single-junction solar cells. The module design is lightweight, fewer than 10 mm thick, and has a profile similar to conventional FPV. Moreover, the combination of the two types of cells increases efficiency. GWU will use its expertise in micro-transfer printing to fabricate and assemble the multi-junction cells. This process will reduce manufacturing costs and further increase efficiency.

George Washington University

Transfer Printed Virtual Substrates

George Washington University (GWU) will develop a new technique to produce commercial III-V substrates called Transfer Printed Virtual Substrates (TPVS). To reduce costs, the team proposes using a single source substrate to grow numerous virtual substrate layers. The team will use an enabling technology, called micro-transfer printing (MTP), to transfer the layers from the source substrate, in the form of many microscale "chiplets," and deposit them onto a low-cost handle (silicon, for example). Once printed, the clean surfaces of the MTP process allows each chiplet to complete the epitaxial growth process on the lower cost substrate after having been seeded from the initial source and having sacrificial layers in between to release the chiplets from the source wafer. The TPVS process can potentially yield tens to hundreds virtual substrates from a single source wafer. Any micro/nanoscale device grown on III-V substrates, such as sensors, detectors, lasers, power electronics, and high-speed transistors, will experience significant cost reductions as a direct result of TPVS deployment. TPVS can also reduce the demand for rare minerals used for a wide range of critical technological applications due to the greater efficiency with which each initial source substrate is utilized.

Georgia Tech Research Corporation

A Novel Intermediate-Temperature Fuel Cell Tailored for Efficient Utilization of Methane

Georgia Tech Research Corporation is developing a fuel cell that operates at temperatures less than 500°C by integrating nanostructured materials into all cell components. This is a departure from traditional fuel cells that operate at much lower or much higher temperatures. By developing multifunctional anodes that can efficiently reform and directly process methane, this fuel cell will allow for efficient use of methane. Additionally, the Georgia Tech team will develop nanocomposite electrolytes to reduce cell temperature without sacrificing system performance. These technological advances will enable an efficient, intermediate-temperature fuel cell for distributed generation applications.

Glint Photonics, Inc.

Self-Tracking Concentrator Photovoltaics

Glint Photonics is developing an inexpensive solar concentrating PV (CPV) module that tracks the sun's position over the course of the day to channel sunlight into PV materials more efficiently. Conventional solar concentrator technology requires complex moving parts to track the sun's movements. In contrast, Glint's inexpensive design can be mounted in a stationary configuration and adjusts its properties automatically in response to the solar position. By embedding this automated tracking function within the concentrator, Glint's design enables CPV modules to use traditional mounting technology and techniques, reducing installation complexity and cost. These self-tracking concentrators can significantly decrease the cost of solar power modules by enabling high efficiency while eliminating the additional costs of precision trackers and specialized mounting hardware. The concentrator itself is designed to be manufactured at extremely low-cost due to low material usage and compatibility with high-speed fabrication techniques. Glint's complete module costs are estimated to be $0.35/watt-peak.

Glint Photonics, Inc.

Stationary Wide-Angle Concentrator PV System

Glint Photonics in collaboration with the National Renewable Energy Laboratory (NREL), will develop a stationary wide-angle concentrator (SWAC) PV system. The SWAC concentrates light onto multi-junction solar cells, which efficiently convert sunlight into electrical energy. A sheet of arrayed PV cells moves passively within the module to maximize sunlight capture throughout the day. Two innovations allow this tracking to occur smoothly and without the expense or complexity of an active control system or a mechanical tracker. First, a fluidic suspension mechanism enables nearly frictionless movement of the sheet embedded in the module. Second, a thermal-gradient-driven alignment mechanism uses a tiny fraction of the collected energy to drive the movement of the sheet and keep it precisely aligned. Glint will develop the novel optical and fluidic components of the SWAC, while NREL will develop custom multi-junction solar cells for the prototype modules.

Integral Consulting

Cost Effective Real Time Wave Assessment Tool

Integral Consulting is developing a cost-effective ocean wave buoy system that will accurately measure its own movements as it follows the surface wave motions of the ocean and relay this real-time wave data. Conventional real-time wave measurement buoys are expensive, which limits the ability to deploy large networks of buoys. Data from Integral Consulting's buoys can be used as input to control strategies of wave energy conversion (WEC) devices and allow these controlled WECs to capture significantly more energy than systems that do not employ control strategies. Integral Consulting's system will also enable assessment of the optimal locations and designs of WEC systems. Integral Consulting's ocean wave buoy system could measure and relay real-time wave data at 10% the cost of commercially available wave measurement systems.

MAHLE Powertrain

Advanced Lean Burn Micro-CHP Genset

MAHLE Powertrain with partners at Oak Ridge National Laboratory, Louthan Engineering, Kohler Company, and Intellichoice Energy will design and develop a CHP generator that uses an internal combustion engine with a turbulent jet ignition (TJI) combustion system. Similar to an automotive internal combustion engine, the proposed system follows the same process: the combustion of natural gas fuel creates a force that moves a piston, transferring chemical energy to mechanical energy used in conjunction with a generator to create electricity. The TJI combustion system incorporates a pre-chamber combustor, enabling the engine to operate in ultra-lean conditions (i.e. high air to fuel mixture), which results in significant improvement in engine thermal efficiency. The team will further increase the system's efficiency by using low friction engine components, while a low-temperature after-treatment system will reduce exhaust emissions.

Massachusetts Institute of Technology

Integrated Micro-Optical Concentrator Photovoltaics with Lateral Multijunction Cells

The Massachusetts Institute of Technology (MIT) with partner Arizona State University will develop a new concept for PV power generation that achieves the 30% conversion efficiency associated with traditional concentrated PV systems while maintaining the low cost, low profile, and lightweight of conventional FPV modules. MIT aims to combine three technologies to achieve their goals: a dispersive lens system, laterally arrayed multiple bandgap (LAMB) solar cells, and a low-cost power management system. The dispersive lens concentrates and separates light that passes through it, providing 400-fold concentration for direct sunlight and 3-fold concentration for diffuse sunlight. The dispersive lens is a thin layer consisting of inexpensive, lightweight materials that can be manufactured at low cost using plastic molding, an improvement over traditional methods. The lens focuses the direct light onto the array of LAMB solar cells, while also focusing the diffuse light onto common PV cells integrated beneath the LAMB array. The power management system combines power from multiple cells into a single output so that the power from a panel of LAMB arrays can be processed with grid-interface power electronics, enabling as much as 20% additional energy capture in applications where the roof is partially shaded.

Massachusetts Institute of Technology

Spectrum Splitting for High-Efficiency Photovoltaic and Solar Thermal Energy Generation

Massachusetts Institute of Technology (MIT) is developing a high-efficiency solar cell grown on a low-cost silicon wafer, which incorporates a micro-scale heat management system. The team will employ a novel fabrication process to ensure compatibility between the indium gallium phosphide (InGaP) solar cell and an inexpensive silicon wafer template, which will reduce cell costs. MIT will also develop a color-selective filter, designed to split incoming concentrated sunlight into two components. One component will be sent to the solar cells and immediately converted into electricity and the other will be sent to a thermal receiver to be captured as heat. This will allow the simultaneous availability of electricity and heat. By leveraging the InGaP system, MIT's solar cells will be more tolerant to high temperature operation than today's PV cells and allow recovery of more useful higher temperature waste heat through the micro-scale heat management system. The solar cell and heat recovery system will enable more efficient use of the entire solar spectrum to produce dispatchable renewable electricity.

Massachusetts Institute of Technology

Full-Spectrum Stacked Solar-Thermal and PV Receiver

Massachusetts Institute of Technology (MIT) is developing a hybrid solar converter that integrates a thermal absorber and solar cells into a layered stack, allowing some portions of sunlight to be converted directly to electricity and the rest to be stored as heat for conversion when needed most. MIT's design focuses concentrated sunlight onto metal fins coated with layers that reflect a portion of the sunlight while absorbing the rest. The absorbed light is converted to heat and stored in a thermal fluid for conversion to mechanical energy by a heat engine. The reflected light is directed to solar cells and converted directly into electricity. This way, each portion of the solar spectrum is directed to the conversion system where it can be most effectively used. The sunlight passes through a transparent microporous gel that also insulates each of the components so that the maximum energy can be extracted from both the heat-collecting metal fins and the solar cells. This unique stack design could utilize the full solar spectrum efficiently and enable the dispatch of electricity at any time of the day.

Massachusetts Institute of Technology

Wafer-Level Integrated Concentrating Photovoltaics

The Massachusetts Institute of Technology (MIT) with partner Sandia National Laboratories will develop a micro-CPV system. The team's approach integrates optical concentrating elements with micro-scale solar cells to enhance efficiency, reduce material and fabrication costs, and significantly reduce system size. The team's key innovation is the use of traditional silicon PV cells for more than one function. These traditional cells lay on a silicon substrate that has etched reflective cavities with high-performance micro-PV cells on the cavity floor. Light entering the system will hit a primary concentrator that then directs light into the reflective cavities and towards the high performance micro-PV cells. Diffuse light, which most CPV technologies do not capture, is collected by the lower performance silicon PV cells. The proposed technology could provide 40-55% more energy than conventional FPV and 15-40% more energy than traditional CPV with a significantly reduced system cost, because of the ability to collect both direct and diffuse light in a thin form factor.

Metis Design Corporation

Advanced Microturbine Engine for Residential CHP

Metis Design Corporation (MDC) with Lawrence Berkley National Laboratory will develop a Brayton cycle engine for residential use to produce heat and electricity. To begin the cycle, air is drawn into the system where it is compressed and pressurized. This compressed air is then heated in a recuperator and introduced in to the combustion chamber. Fuel is injected in to the combustion chamber and subsequently the air-fuel mixture is ignited. The high temperature exhaust gases then expand through a turbine, providing some of the work that drives the original compressor and the remainder produces electricity in a generator. Other innovations include adding a rotating vaneless diffuser to the compression process to reduce viscous losses that would normally reduce the efficiency of small compressors. The design also includes a high-efficiency recuperator to capture waste heat from the turbine exhaust and a low swirl burner to reduce emissions.

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