As an alternative to conventional methods of conveying and delivering energy in mobile applications or to remote locations, we have examined the combustion of nanostructured metal particles assembled into metal clusters. Clusters containing iron nanoparticles (∼50nm in diameter) were found to combust entirely in the solid state due to the high surface-to-volume ratio typical of nanoparticles. Optical temperature measurements indicated that combustion was rapid (∼500ms), and occurred at relatively low peak combustion temperatures (1000-1200K). Combustion produces a mixture of Fe(III) oxides. X-ray diffraction and gravimetric analysis indicated that combustion was nearly complete (93–95% oxidation). Oxide nanoparticles could be readily reduced at temperatures between 673K and 773K using hydrogen at 1atm pressure, and then passivated by the growth of a thin oxide layer. The nanostructuring of the particles is retained throughout the combustion–regeneration cycle. Modeling of the combustion process is in good agreement with observed combustion characteristics.

The goal of the Cooling, Heating, and Power (CHP) Program established in 2000 by the US Department of Energy (DOE) is to provide research, development, and testing (both laboratory and field) and to accelerate implementation of distributed electric generation (DG) with thermally activated technologies (TAT). The objective is to provide DG with waste heat recovery, i.e., combination of DG and waste heat recovery utilization to drive various TATunits (heat recovery, desiccant, absorption chiller units, etc) and increase overall fuel efficiency of the technology. Dynamic tests of the CHP system, which were performed at the CHP Integration Laboratory of the Oak Ridge National Laboratory (ORNL), are presented. The CHP system at the lab includes: a 30-kW microturbine generator an air-to-water heat recovery unit, an indirect-fired single-effect 10-ton (35-kW) absorption chiller and indirect and direct-fired desiccant dehumidification units. The dynamic system response of the CHP system was tested during both cold-start-up and power-dispatch (changing electric/thermal demand) modes. The test results provide valuable information for both understanding CHP performance as well as for use to develop better control tools for CHP equipment.

Integrated energy systems (IES) offer the potential for a significant increase in the nation's fuel use efficiency by generating electricity onsite near the load and recycling the exhaust gas for heating, drying, cooling, or dehumidifying. A key challenge for IES is the efficient and cost-effective integration of distributed generation (DG) equipment with thermally-activated (TA) technologies. The US Department of Energy (DOE) launched the IES program in 2001 to focus on laboratory and field research to address these critical issues, advance the technology and accelerate application of combined Cooling, Heating and Power (CHP). An example of IES is the combination of an onsite microturbine with heat recovery, HVAC, desiccant and absorption chiller units. IES, in conjunction with other new energy efficient building technologies, will maximize the efficiency of energy use, reduce harmful emissions to the environment, improve power quality and reliability and provide flexibility for meeting electric power peak load demands as compared with large central power plants. The R&D performed at the Oak Ridge National Laboratory's (ORNL) IES Laboratory focuses on assessing the operational and emissions performance of current DG and TA technologies operated individually and in combination as an IES; developing and verifying mathematical models of the individual devices and IES; and supporting the development of test protocols and standards for assessing IES technologies.The IES Test Laboratory is a flexible test-bed for the configuration of DG (presently a 30-kW natural gas-fired microturbine-generator) with various heat recovery units (an air-to-water heat recovery unit or HRU, direct- and indirect-fired desiccant dehumidification systems, and an indirect-fired single-effect absorption chiller). The exhaust gas from the microturbine-generator (MTG) is used to drive the HRU and/or used directly in the direct-fired desiccant dehumidification unit. The hot air and hot water flows from the HRU can be controlled and directed via automated damper controls in order to test various TES configurations and operating modes. The hot air can be conditioned with an air-mixing chamber.The IES testing results produced so far show that the operating parameters and efficiencies of the overall system and individual devices depend on loading (electric and thermal), as well as on ambient weather conditions (temperature and humidity levels). Outdoor temperature is a major factor since the MTG is located outside and its power and heat output are functions of the outside temperature and humidity and no attempt is currently being made to adjust its inlet air temperature, i.e., air cooling from the TA units. Under certain operating conditions and combinations of IES, the efficiency (including all parasitics) of the overall system can be as high as 55% (based on higher heating value of the natural gas). Published by Elsevier Ltd.

This paper documents the development and validation of predictive algorithms for modeling the microturbine in a building combined cooling, heating and power (BCHP) system. The mathematical model developed in this study is based on a 30-kW natural gas-fired microturbine; however, it can be extended to encompass a microturbine of any capacity and fuel-type. Both experimental and theoretical data are being used to model the BCHP system consisting of a combined microturbine and heat-recovery components and to determine ways to improve the overall BCHP system efficiency. The purpose of this paper is to outline the basis for the development of the BCHP model and to report on progress that has been made in regards to modeling microturbine operation with thermal recovery. The basic steps being used to develop the modular structure of the BCHP system mathematical model are described, and the model developed to date has been validated by experimental data. The first step has been the mathematical modeling of the natural gas-fired microturbine. The process involved developing the thermodynamic equations that describe the polytropic processes of compression and expansion in the compressor and turbine, respectively, and developing the heat balance and mechanical energy balance equations. A linear analysis method was used to derive the equations that relate the change in the microturbine exhaust backpressure to the change in its output power and efficiency. The mathematical model was applied to the baseline performance data collected on the 30-kW natural gas-fired microturbine unit under steady-state conditions at various loads (10 to 30 kW or one-third to full output power settings, in 5 kW increments) and at various exhaust backpressures (2.7x10 to 1.7x10 atm). Under these modes of operation, the basic operating parameters (temperatures, pressures, flows, voltages, currents, etc.) and the output power of the microturbine were measured, and its energy efficiency was calculated. Without any external backpressure applied to the microturbine exhaust (damper fully open), the average measured power output ranged from 10.0 to 27.8 kW. The microturbine efficiency averaged from 18.0% to 23.0% for the one-third to full output power demand settings. With maximum externally applied backpressure (1.70x10 atm), the model shows that the output power losses (decrease in power output) due to backpressure range from 3.5% for full output to 5.5% for one-third power (lowest value of ~3% occurs at 25 kW), while the efficiency losses (decrease in efficiency) range from 2.5 to 4% (lowest value of ~2.0% occurs at 25 kW), correspondingly. The internal energy losses were calculated to be approximately 30% of the total power produced.

ABSTRACT The number of Distributed Energy Resources (DER), such as gas microturbines, as well as combined Cooling, Heating and Power (CHP) systems which combine power generation with thermal heat recovery have increased markedly over the last several years. Environmental issues are among one of the ,most important aspects of operating ,these systems. This paper presents results of an ,emissions study of a microturbine-based CHP Integration Test System that is located at the ,Oak Ridge National Laboratory (ORNL). For the DER emissions tests, a CHP system consisting of a 30-kW natural gas-fired microturbine located

Abstract On-site and near-site distributed power generation (DG), as part of a Buildings Cooling, Heating and Power (BCHP) system, brings both electricity and waste heat from the DG sources closer to the end user’s electric and thermal loads. Consequently, the waste heat can be used as input power for heat-activated air conditioners, chillers, and desiccant dehumidification systems; to generate steam for space heating; or to provide hot water for laundry, kitchen, cleaning services and/or restrooms. By making use of what is normally waste heat, BCHP systems meet a building’s electrical and thermal loads with a lower input of fossil fuel, yielding resource efficiencies of 40 to 70% or more. To ensure the success of BCHP systems, interactions of a DG system — such as a microturbine and thermal heat recovery units under steady-state modes of operation with various exhaust backpressures — must be considered. This article studies the performance and emissions of a 30-kW microturbine over a range of design and off-design conditions in steady-state operating mode with various backpressures. In parallel with the experimental part of the project, a BCHP mathematical model was developed describing basic thermodynamic and hydraulic processes in the system, heat and material balances, and the relationship of the balances to the system configuration. The model can determine the efficiency of energy conversion both for an individual microturbine unit and for the entire BCHP system for various system configurations and external loads. Based on actual data from a 30-kW microturbine, linear analysis was used to obtain an analytical relationship between the changes in the thermodynamic and hydraulic parameters of the system. The actual data show that, when the backpressure at the microturbine exhaust outlet is increased to the maximum of 7 in. wc (0.017 atm), the microturbine’s useful power output decreases by from 3.5% at a full power setting of 30 kW to 5.5% at a one-third power setting (10 kW), while the efficiency of the unit decreases from 2.5 to 4.0%, accordingly. Tests on the microturbine were conducted at the Cooling, Heating, and Power Laboratory set up at the Oak Ridge National Laboratory’s Buildings Technology Center. Data were collected from the microturbine at power demand settings of 30 kW (full load) to 10 kW in 5-kW increments. For each power demand setting, data measurements were taken over an entire range of microturbine exhaust backpressures. The parameters measured were engine speed, ambient air temperature, air temperature at the microturbine inlet, gas temperature at the turbine outlet, exhaust gas temperature, throttle pressure loss, flow rate of natural gas, and composition of combustion products. The mathematical model provided gas temperature before the turbine, compression rate, and air flow rate, which were determined based on the measured data. The results of these early tests and the computer-based simulation model are in very close agreement.

An analytical method is proposed for finding numerical values of binary interaction coefficients for the Lee-Kesler-Plöcker (LKP) equation of state. The method is based on solving simultaneous equations from Plöcker's mixing rules for pseudocritical parameters of a mixture and the Lee-Kesler equation for the saturation line. For mixtures of hydrocarbons containing from two to nine carbon atoms, the divergence between calculated and experimentally based interaction coefficients (ICs) is no more than ±0.4%. The method is extended to mixtures of polar substances. For polar mixtures, aneffective molar composition concept is introduced which takes into account the impact of dipole moments on the process of molecular associations. Formulas for finding the effective molar composition of mixtures containing polar and/or nonpolar constituents and the binary interaction coefficient (κij) based on this effective composition and pure component properties are shown. Calculatedκij values for 12 binary mixtures of polar substances differ by 0.4 % or less from correspondingκij values obtained by processing experimental data on saturated pressure (Ps) and saturated temperature (Ts) lines for these same mixtures. A simplified alternativeκij approximation method with an error (2–5 %) is also given for mixtures of polar substances.

The use of on-site or near-site distributed electric power generation (DG), as part of an Integrated Energy System (IES), brings available waste heat closer to the end user=s thermal loads. Heat-activated technologies such as desiccant dehumidification units are increasingly being viewed as an important element to effectively apply in IES designs that increase system efficiency, reduce fuel costs and consumption, and provide both electrical and thermal load energy. The purpose of this study is to investigate both the baseline performance of a commercially available direct- fired desiccant dehumidification unit and its performance as one of the components of an IES. Desiccant dehumidification units, which are used to reduce the latent load (remove moisture) of the process (conditioned) air, are specified on the basis of grain depression and/or latent capacity (LC). Several operating parameters, such as process and regeneration air conditions (dry-bulb temperature and humidity), volumetric air flow rates, and desiccant loading affect the ability of the desiccant unit to remove moisture. This study investigates the impact of varying process and regeneration conditions on LC and latent coefficient of performance (LCOP) of heat-activated desiccant dehumidification units. The baseline performance of the desiccant unit with regeneration air heated by direct burning of natural gas is compared with an IES case in which the exhaust gas from a microturbine and its heat recovery unit are used as the regeneration energy source. Baseline performance tests show that both LC and LCOP increased with inlet air dew-point while keeping the other parameters (gas input and electrical parasitics) constant. The maximum baseline LCOP and LC were 0.58 and 103,246 Btu/h (30 kW), respectively. Using residual microturbine exhaust gas (what remains of the exhaust after going through an air-to water heat recovery unit) as the regeneration heat source results in a 50% decrease in the latent cooling capacity of the desiccant dehumidification unit as compared to its baseline performance. However, adding the desiccant dehumidification unit to a microturbine/heat recovery unit in the IES increased system efficiency by 7% over the microturbine/heat recovery unit only. Emissions tests show that the most significant pollutant is carbon monoxide (CO). The average CO level in the regeneration outlet air (flue gas) was found to be ~13 ppm. In addition, the emissions tests did not show any significant cross-contamination between the process and regeneration air stream sides of the desiccant dehumidification unit.

A laboratory facility for testing combined cooling/heating and power (CHP) or more currently referred to as Integrated Energy Systems (IES) has been commissioned at the Oak Ridge National Laboratory (ORNL). The scope of the facility is to test distributed generation (DG) with thermally-activated (TA) technologies for waste heat recovery. The designation of the IES Laboratory Facility as a "National User Facility" provides industry with greater access and control to various IES testing that can be conducted at the laboratory. The IES laboratory test facility is concluding the testing of a 30 kW microturbine generator (MTG) with a first generation heat recovery unit (HRU), direct and indirect- fired desiccant dehumidification systems and an indirect- fired 10-ton single-effect absorption chiller. The MTG has been operated individually to obtain its baseline performance characteristics as well as in combination with various waste heat recovery configurations to test an MTG-based IES. The dynamic and steady-state electrical, thermal, and emissions performance of the MTG has been measured over the power output range of 3 to 30 kW as well as during startup and shutdown. The heat recovery process has been found to reduce the energy efficiency and power output of the MTG slightly due to the increased backpressure on the MTG's exhaust. However, the overall MTG-based IES system produces a 35-60% efficiency vs. the ~23% efficiency of the individual MTG. A number of key results have been produced by the laboratory and are leading to IES recommendations. Also, performance issues related to the MTG have been identified and are being addressed.

The scope of the Integrated Energy Systems (IES) Program directed by the U.S. Department of Energy (DOE)'s Distributed Energy Program is to provide R&D and testing of distributed generation (DG) combined with thermally-activated technologies (TAT) for waste heat recovery. The goal is to improve the overall performance and efficiency of IES technology and accelerate its use by industry. One of the key parameters that exert an influence on IES performance is ambient inlet air condition. The R&D currently performed at the Oak Ridge National Laboratory's (ORNL) IES Test Laboratory, a National User Facility, is focused on the operational (electrical and thermal) and emissions performance of a 30-kW microturbine generator (MTG)-based IES system. Specifically, this paper addresses the use and effectiveness of MTG inlet cooling and humidification. Results of testing at the IES Laboratory reveal that, although inlet cooling with and without moisture injection can result in performance improvement in some IES components, there is no overall gain in IES efficiency. In the case of inlet cooling with moisture injection (for humidification), much higher evaporative cooling and subsequently moisture levels is needed at the input of the MTG in order to produce any significant gain in IES performance. However, these increased moisture levels could potentially be harmful to the MTG unit. These tests indicate that inlet cooling is not recommended for this size MTG if the goal is to achieve either IES efficiency gains or reduction of emissions from the MTG exhaust. These findings do not, however, completely rule out inlet cooling for larger microturbines or for other types of distributed generators (i.e., reciprocating engines). Future testing is needed to determine effects of inlet cooling on the performance characteristics of larger microturbines and other generators.