Following the rapid growth of distributed energy resources (e.g. renewables, battery), localized peer-to-peer energy transactions are receiving more attention for multiple benefits, such as, reducing power loss, stabilizing the main power grid, etc. To promote distributed renewables locally, the local trading price is usually set to be within the external energy purchasing and selling price range. Consequently, building prosumers are motivated to trade energy through a local transaction center. This local energy transaction is modeled in bilevel optimization game. A selfish upper level agent is assumed with the privilege to set the internal energy transaction price with an objective of maximizing its arbitrage profit. Meanwhile, the building prosumers at the lower level will response to this transaction price and make decisions on electricity transaction amount. Therefore, this non-cooperative leader-follower trading game is seeking for equilibrium solutions on the energy transaction amount and prices. In addition, a uniform local transaction price structure (purchase price equals selling price) is considered here. Aiming at reducing the computational burden from classical Karush-Kuhn-Tucker (KKT) transformation and protecting the private information of each stakeholder (e.g., building), swarm intelligence based solution approach is employed for upper level agent to generate trading price and coordinate the transactive operations. On one hand, to decrease the chance of premature convergence in global-best topology, Rubiks Cube topology is proposed in this study based on further improvement of a two-dimensional square lattice model (i.e., one local-best topology-Von Neumann topology). Rotating operation of the cube is introduced to dynamically changing the neighborhood and enhancing information flow at the later searching state. Several groups of experiments are designed to evaluate the performance of proposed Rubiks Cube topology based particle swarm algorithm. The results have validated the effectiveness of proposed topology and operators comparing with global-best version PSO and Von Neumann topology based PSO and its scalability on larger scale applications.

On-board hydrogen production via catalytic autothermal reforming is beneficial to vehicles using fuel cells because it eliminates the challenges of hydrogen storage. As the primary fuel for both civilian and military air flight application, Jet-A fuel (after desulfurization) was reformed for making hydrogen-rich fuels in this study using an in-house-made Rh/NiO/K-La-Ce-Al-O X ATR catalyst under various operating conditions. Based on the preliminary thermodynamic analysis of reaction equilibrium, important parameters such as ratios of H 2 O/C and O 2 /C were selected, in the range of 1.1–2.5 and 0.5–1.0, respectively. The optimal operating conditions were experimentally obtained at the reactor’s temperature of 696.2 °C, which gave H 2 O/C = 2.5 and O 2 /C = 0.5, and the obtained fuel conversion percentage, hydrogen yield (can be large than 1 from definition), and energy efficiency were 88.66%, 143.84%, and 64.74%, respectively. In addition, a discussion of the concentration variation of CO and CO 2 at different H 2 O/C, as well as the analysis of fuel conversion profile, leads to the finding of effective approaches for suppression of coke formation.

The unsteady 3D fluid flow coupled to radiative, convective, and conductive heat transfers are computed within a cavity-receiver that was successfully tested experimentally. A Monte-Carlo radiation model is used in the fluid regions of the reactor with source terms outside the cavity’s window to account for the concentrated radiative power input. Darcy’s law for the viscous regime and the Forchheimer’s term for the inertial regime are used in the momentum equation to account for the pressure drop within the porous region (RPC). Two separate energy equations for the solid and for the fluid regions of the porous domain are solved in order to capture the non-equilibrium effects in that region. Rosseland diffusion approximation is used in the solid regions of the RPC domain. The material properties and boundary conditions were taken from published experimental measurements. The simulation results are compared to the measurement data collected during the pre-heating and the ceria reduction phases, which sum up to four different radiative power inputs. Results of the comparison are very good and constitute the verification that the numerical methods, physical sub-process models and material properties are adequately selected and implemented. An analysis regarding the heat balance, the recirculating flow and, the effect of dual-scale porosity is also presented.

A sulfur based thermochemical energy storage cycle for baseload power generation is being developed under the support of US DOE Sunshot program. Solar heat is stored in elemental sulfur via thermal decomposition of sulfuric acid and disproportionation of sulfur dioxide into elemental sulfur and sulfuric acid. Heat energy is recovered upon sulfur combustion. On-sun decomposition of sulfuric acid in a solar furnace has been demonstrated between 650 and 850°C. Near equilibrium conversion was obtained at high temperature but conversion was reduced due to catalyst poisoning at the lower temperatures. Sulfur dioxide disproportionation modeling showed the reaction driving force is maximized at the high system pressure and low system temperature. The effect of system pressure was validated experimentally. However, the disproportionation rate was found to increase with system temperature as a result of increased reaction kinetics. Homogenous iodide catalysts were used to further enhance the degree of disproportionation and the reaction rate. The process steps required to recover the catalyst for reuse have been verified.

The redox chemistry of nonstoichiometric metal oxides can be used to produce chemical fuels by harnessing concentrated solar energy to split water and/or carbon dioxide. In such a process, it is desirable to use a porous reactive substrate for increased surface area and improved gas transport. The present study develops a macroscopic-scale model of porous ceria undergoing thermal reduction. The model captures the coupled interactions between the heat and mass transfer and the heterogeneous chemistry using a local thermal non-equilibrium (LTNE) formulation of the volume averaged conservation of mass and energy equations in an axisymmetric cylindrical domain. The results of a representative test case simulation demonstrate strong coupling between gas phase mass transfer and the chemical kinetics as well as the pronounced impact of optical thickness on the temperature distribution and thus global solar-to-chemical energy conversion.

The performance of the adsorption cooling system using the zeolite 13X/CaCl 2 composite adsorbent was studied using a numerical simulation. The novel zeolite 13X/CaCl 2 composite adsorbent with superior adsorption properties was developed in previous studies [11]. It has high equilibrium water uptake of 0.404 g/g between 25°C and 100°C under 870Pa. The system specific cooling power (SCP) and coefficient of performance (COP) were successfully predicted for different operation parameters. The simulated COP with the composite adsorbent is 0.76, which is 81% higher than a system using pure zeolite 13X under desorption temperature of 75°C. The SCP is also increased by 34% to 18.4 W/kg. The actual COP can be up to 0.56 compared to 0.2 for zeolite 13X-water systems, an increase of 180%. It is predicted that an adsorption cooling system using the composite adsorbent could be powered by a low grade thermal energy source, like solar energy or waste heat, using the temperature range of 75°C to 100°C. The performance of the adsorber with different design parameters was also studied in the present numerical simulation. Adsorbents with smaller porosity can have higher thermal conductivity and may result in better system performance. The zeolite bed thickness should be limited to 10mm to reduce the thermal response time of the adsorber. Addition of high thermal conductivity materials, for example carbon nanotube, can also improve the performance of the adsorber. Multi-adsorber tube connected in parallel can be employed to provide large heat transfer surface and maintain a large SCP and COP. The desorption temperature also showed a large effect on the system performance.

Additives of highly-conducting nanoparticles such as graphene to a phase change material (PCM) improves PCM heat diffusion, which in turn produces better energy storage than pure PCM. Equilibrium Molecular Dynamics (EMD) simulations with Green-Kubo relations are used to predict the thermal conductivity of graphene sheets of various sizes and using different ensemble formulations. The Tersoff potential function has been implemented to model the covalent bonds between carbon atoms. The MD simulations predict an increase in thermal conductivity with graphene sheet size, and the predictions for the canonical (NVT) ensemble are consistently larger than those using the microcanonical (NVE) ensemble. The autocorrelation functions for the NVT simulations converge to zero for large sampling periods, which is not the case for NVE simulations.

As environmental sustainability becomes increasingly integrated into the mainstream values, previously ignored externalities may be expected to enter into the economic valuation process. This is already evident, as an illustration, in the price that several entities are beginning to attach to carbon (with examples including cap-and-trade, carbon taxes, etc). In this paper, we present a basic economic partial equilibrium model to evaluate such externalities within the context of a particular industry. We begin by discussing how economic values may be attached to different externalities, and focus our analysis on carbon as an example of an environmental impact which may need to get internalized within the cost structure of a given organization. With such a new cost structure in place, we use historical estimates of the elasticity of supply and demand within a given industry to evaluate how the costs may propagate up and down the value chain. For example, how much of the costs are likely to get absorbed internally within a supply chain? What fraction of costs might a manufacturer reasonably expect to pass along to downstream consumers? With such estimates in place, we then predict using microeconomic theory how the supply-demand equilibrium within a particular market may shift. We discuss how such a simple approach to evaluating externalities may be used to simulate the effects of different policy choices, and illustrate the approach through an example case study of the electric utility industry. We conclude with a discussion of future work that seeks to expand considerations beyond the electric utility industry and methods to extend this simplified modeling framework.

In recent studies, plasma gasification has shown great potential as an effective method for solid waste treatment and energy recovery. In this study, a plasma gasification process is simulated based on a chemical equilibrium model developed in Aspen Plus. The model takes into account the properties of different feedstock, used for gasification, and the input plasma energy and evaluates the output syngas composition following a Gibbs free energy minimization approach. The model is used to evaluate plasma gasification of three types of feedstock i.e. industrial waste (shredded tires), construction waste (plywood), and baseline bituminous coal. The process is optimized for two different types of plasma gas: air and steam. Process metrics are evaluated and compared for the considered feedstock. Results showed an obtained plasma gasification efficiency of 46.4% for shredded tires and 41.1% for plywood and bituminous coal. Energy recovery potential is also evaluated using an integrated plasma gasification combined cycle (IPGCC) power plant model. Thermal efficiencies of the process are evaluated and compared for the different feedstock. Plasma gasification of waste tire material resulted in an energy efficiency of 28.5%, while the efficiency for coal and plywood was lower at 20.0% and 18.3%, respectively.

This paper compares hydrogen production by photovoltaic powered electrolysis of water at sea level and at low stratospheric altitudes up to 21 km. All the hydrogen production process has been considered from catchable solar radiation to storage technologies. The evaluation has been performed for 1 m 2 of flat horizontal plane. It has been considered the electric energy amount produced considering variations in equilibrium temperature and in solar. Hydrogen production through electrolysis has been evaluated too. Two different methods of hydrogen storage have been evaluated: high pressure compression up to 20 MPa and liquefaction process. The energetic cost of both production processes has been evaluated. The comparison is presented in terms of effective energy deliverable to final users considered in terms of HHV. This evaluation considers also, in the case of liquefaction process the energy which can be recovered by the rigasification process.

Composite adsorbents synthesized from zeolite 13X and CaCl 2 were investigated for applications in solar adsorption systems. The effect of Ca-ion-exchange on the adsorption properties of zeolite 13X was studied. Sodium ions in the zeolite structure were replaced by calcium ions by ion exchange. It was found that the Ca-ion-exchange process decreased the specific surface areas of the Ca-ion-exchanged zeolites while the total pore volumes were increased. The optimized Ca-ion-exchange condition existed when soaking zeolite 13X in 46wt% CaCl 2 solution for 36 hours. The increase in the total pore volume is good for further impregnating the zeolite with CaCl 2 . A large difference in equilibrium water uptake, 0.404g/g, between 25°C and 100°C under 870Pa was recorded for the 13X/CaCl 2 composite adsorbent impregnated in 40wt% CaCl 2 solution. This was 295% of that of zeolite 13X under the same condition. The 13X/CaCl 2 composite adsorbent showed a high potential in replacing vapor compression chillers in producing chilled water for central air-conditioning systems.

An equilibrium economic model for policy evaluation related to electricity generation has been developed; the model takes into account the non-renewable and renewable energy sources, demand and supply factors and environmental constraints. The non-renewable energy sources include three types of fossil fuels: coal, natural gas and petroleum, and renewable energy sources include nuclear, hydraulic, wind, solar photovoltaic, biomass wood, biomass waste and geothermal. Energy demand sectors include households, industrial manufacturing and commercial enterprises (non-manufacturing businesses such as software firms, banks, restaurants, service organizations, universities, etc.). Energy supply takes into account the electricity delivered to the consumer by the utility companies at a certain price which maybe different for retail and wholesale customers. Environmental risks primarily take into account the CO 2 generation from fossil fuels. The model takes into account the employment in various sectors and labor supply and demand. Detailed electricity supply and demand data, electricity cost data, employment data in various sectors and CO 2 generation data are collected for a period of seventeen years from 1990 to 2006 in U.S. The model is calibrated for the aggregate data. The calibrated model is then employed for policy analysis experiments if a switch is made in sources of electricity generation, namely from fossil fuels to renewable energy sources. As an example, we consider a switch of 10% of electricity generation from coal to 5% from wind, 3% from solar photovoltaic, 1% from biomass wood and 1% from biomass waste. It should be noted that the cost of electricity generation from different sources is different and is taken into account. The consequences of this switch on supply and demand, employment, wages, and emissions are obtained from the economic model under three scenarios: (1) energy prices are fully regulated, (2) energy prices are fully adjusted with electricity supply fixed, and (3) energy prices and electricity supply both are fully adjusted.

Three major challenges — grid stability, domestic oil limitations, and climate change — could all be addressed simultaneously by using off-peak electrical energy to recycle CO 2 into liquid fuels (such as gasoline, jet fuel, and diesel). Simulations have shown that recent innovations should make it practical to reduce CO 2 to CO at over 66% of theoretical efficiency limits. When combined with other process advances, it would then be possible to synthesize most hydrocarbons and alcohols from point-source CO 2 and clean off-peak grid energy (wind or nuclear) at system efficiencies in the range of 51–61%. Energy storage density in renewable, carbon-neutral kerosene is 44 MJ/kg, compared to ∼0.4 MJ/kg for Li-ion batteries. This process begins by electrolyzing water using clean energy to get the hydrogen required by the Reverse Water Gas Shift (RWGS) reactor and by a novel Renewable Fischer Tropsch Synthesis (RFTS) process. Off-peak grid energy averaged only $13/MWhr in the Minnesota hub in 2009. At such prices, the synthesized liquid fuels ( “WindFuels” ) should compete even when petroleum is only $50/bbl. Considerable effort over the past decade has been put into exploring high-temperature (HT) paths toward the production of renewable syngas (H 2 + CO) that could lead to sustainable synthesis of liquid fuels; but competitive fuel production from these HT thermo-chemical routes still appears to be decades away. An alternative path — the RWGS reaction — utilizes much less aggressive conditions and should be much more practical. With low-cost hydrogen becoming available from off-peak wind and nuclear, efficient reduction of CO 2 to CO becomes viable at moderate temperatures (750–1000 K) via the RWGS reaction. Challenges arise because of equilibrium limits imposed by the reaction thermodynamics below 800 K and because of competing methanation and coking reactions above 800 K to 1000 K, depending on the catalysts. Several promising sets of conditions and catalysts are being evaluated. To drive the reaction to the right, a multi-stage process is required with efficient separation processes. This in turn depends on advances in cost-effective gas-to-gas recuperators for relatively low pressures to limit parasitic methanation reactions. Another challenge may be passivation of the recuperator surfaces to minimize hydrogenation of the CO during the heat recovery. Preliminary simulations indicate reduction of CO 2 to CO with about 2.2 MJ/kg-CO should be practical at commercial scale.

Thermal energy storage can enhance the utility of parabolic trough solar power plants by providing the ability to match electrical output to peak demand periods. An important component of thermal energy storage system optimization is selecting the working fluid used as the storage media and/or heat transfer fluid. Large quantities of the working fluid are required for power plants at the scale of 100-MW, so maximizing heat transfer fluid performance while minimizing material cost is important. This paper reports recent developments of multi-component molten salt formulations consisting of common alkali nitrate and alkaline earth nitrate salts that have advantageous properties for applications as heat transfer fluids in parabolic trough systems. A primary disadvantage of molten salt heat transfer fluids is relatively high freeze-onset temperature compared to organic heat transfer oil. Experimental results are reported for formulations of inorganic molten salt mixtures that display freeze-onset temperatures below 100°C. In addition to phase-change behavior, several properties of these molten salts that significantly affect their suitability as thermal energy storage fluids were evaluated, including chemical stability and viscosity. These alternative molten salts have demonstrated chemical stability in the presence of air up to approximately 500°C in laboratory testing and display chemical equilibrium behavior similar to Solar Salt. The capability to operate at temperatures up to 500°C may allow an increase in maximum temperature operating capability vs. organic fluids in existing trough systems and will enable increased power cycle efficiency. Experimental measurements of viscosity were performed from near the freeze-onset temperature to about 200°C. Viscosities can exceed 100 cP at the lowest temperature but are less than 10 cP in the primary temperature range at which the mixtures would be used in a thermal energy storage system. Quantitative cost figures of constituent salts and blends are not currently available, although, these molten salt mixtures are expected to be inexpensive compared to synthetic organic heat transfer fluids. Experiments are in progress to confirm that the corrosion behavior of readily available alloys is satisfactory for long-term use.

Because of converging concerns about global climate change and depletion of conventional petroleum resources, many nations are looking for ways to create transportation fuels that are not derived from fossil fuels. Biofuels and hydrogen (H 2 ) have the potential to meet this goal. Biofuels are attractive because they can be domestically produced and consume carbon dioxide (CO 2 ) during the feedstock growth cycle. Hydrogen is appealing because its use emits no CO 2 , and because hydrogen fuel cells can be very efficient. Today most hydrogen is derived from syngas, a mixture of hydrogen, carbon monoxide (CO) and carbon dioxide, which is produced through catalytic steam reforming of methane (CH 4 ). Although effective, this process still produces CO 2 . Another method used to generate hydrogen is water electrolysis, but this process is extremely energy intensive. Thus, finding an energy-efficient approach to producing hydrogen from biofeedstock is appealing. Though there are many biofuels, ethanol (C 2 H 5 OH) is a popular choice for replacing fossil fuels. However, many have questioned its value as a renewable fuel since it requires a significant amount of energy to produce, especially from corn. Producing pure ethanol requires substantial energy for distillation and dehydration to yield an appropriate “dry” fuel for traditional combustion engines. Wet ethanol, or ethanol that has not been fully distilled and dehydrated, requires significantly less energy to create than pure ethanol. In this paper, we present a non-catalytic pathway to produce hydrogenrich syngas from wet ethanol. The presence of water in the reactant fuel can increase the hydrogen mole fraction and decrease the carbon monoxide mole fraction of the product syngas, both of which are desired effects. Also, because there are no catalytic surfaces, the problems of coking and poisoning that typically plague biomass-to-hydrogen reforming systems are eliminated. The non-catalytic fuel reforming process presented herein is termed filtration combustion. In this process, a fuel-rich mixture of air and fuel is reacted in an inert porous matrix to produce syngas. Some of the ethanol and air mixtures under study lie outside the conventional rich flammability limits. These mixtures react because high local temperatures are created as the reaction front propagates into a region where the solid matrix has been heated by exhaust gases. These high temperatures effectively broaden the flammability limits, allowing the mixture to react and break down the fuel into syngas. The conversion of pure and wet ethanol is a novel application of this process. Exhaust composition measurements were taken for a range of water fractions and equivalence ratios (Φ) and were compared to equilibrium values. The water fraction is the volumetric fraction of the inlet fuel and water mixture that is water. Equivalence ratio is the ratio of the fuel to oxidizer ratio of the reactant mixture to the fuel to oxidizer ratio of a stoichiometric mixture. A stoichiometric mixture is defined as a mixture with proportions of fuel and oxidizer that would react to produce only water and carbon dioxide. The stoichiometric mixture (Φ = 1) of ethanol and oxygen (O 2 ) is 1 mole of ethanol for every 3 moles of oxygen: C 2 H 5 OH + 3 O 2 ↔ 2 CO 2 + 3 H 2 O Hydrogen mole fraction of the exhaust gas increased with increasing equivalence ratio and remained nearly constant for increasing water-in-fuel concentration. Carbon monoxide mole fraction was also measured because it may be used as a fuel for certain fuel cells while it can poison others [1]. Species and energy conversion efficiencies were calculated, showing that significant energy savings could be made by reforming wet ethanol rather than pure ethanol into syngas. Also, it is shown that the hydrogen to carbon monoxide ratio increases with addition of water to the fuel, making this method attractive for the production of pure hydrogen.