In the ferronickel production process, mineral calcination is one of the most energy-intensive stages. In a typical rotary kiln calciner, particulate solids and combustions gases move counter currently, while solids undergo drying, pre-reduction, and partial reduction reactions. The combustion of natural gas provides the thermal energy for drying and reduction reactions. About 80 to 85% of the incoming laterite ore leaves the reactor as calcined ore, while the flue gases entrain part of the solids as dust. This work presents a theoretical analysis contrasted with experimental results to evaluate the partial reduction of laterite ores in two rotary kilns of 185 m and 135 m length. The study focused on the water formed in the process, including a comparative analysis of water consumption by two different solids recovery technologies, a gas scrubber and an electrostatic precipitator. Simulations allowed evaluating the water and greenhouse gas formation in the main streams of the process. Among the tested operation conditions, the moisture content in the pellets, consisting of agglomerated dust, strongly influenced the amount of water released in the process and the energy consumption. Furnace RK-2 needs approximately 56% more energy to evaporate the moisture content in the feedstock. Furthermore, furnace RK-2 released 55.4 m 3 h −1 of water into the atmosphere, which represented two times the amount released by furnace RK-1. Gas scrubber analysis showed that as the liquid water increased, more H 2 O in the gases was condensed; however, the destroyed exergy also increased. Electrostatic precipitators appear as an adequate technology for reducing water and energy consumption in the ferronickel industry.

The thermoelectric generator (TEG) output power is mainly dependent on physical characteristics, dimensions, leg configuration, number of p-n thermocouples, and other parameters. Therefore, identifying the optimal leg configuration that attains the best performance is essential. The present work considers several leg configurations by the volume reduction of the conventional prism leg, without changing the shape class via decreasing basic dimensions (i.e. leg height or cross-sectional area) and with morphing the original prism into X and trapezoidal shapes. A three-dimensional thermo-electric model is developed to investigate the performance of TEG legs at the uni-thermocouple level. Besides, to determine the reliability of the proposed configurations, a wide range of thermal boundary conditions are applied on the hot side to resemble the realistic working environment that TEG might experience at room temperature on the cold side with natural convective cooling. The model is numerically simulated after being validated with the available experimental and numerical data. The comparison indicates that decreasing leg height adversely affects the TEG performance, whereas a significant enhancement in the performance is achieved (in order) for X , trapezoidal and reduced area shapes. However, the performance enhancement, i.e. power and efficiency, associated with the simple reduced area configuration is relatively close to those achieved by X or trapezoidal ones, raising many questions in terms of simplicity and manufacturing cost. The performed research further deepens our understanding of TEG performance enhancement via optimizing legs’ attributes at uni-thermocouple as a single building block of the full-size TEG module.

The food processing industry exists at the nexus between food, energy, and water systems. Improving the sustainability of this industry is critical to reduction of carbon emissions and enhanced utilization of vital resources such as water. The overarching aim of the present research is to create a process-based modeling platform for food processing systems that would allow the most appropriate combination of water-sustainable, energy-efficient, and renewable energy (WERE) technologies to be determined for a system. This paper focuses on one specific process in a thermal processing line: the cooling step after sterilization and prior to packaging. A typical process might use groundwater in a once-through loop. To reduce water use, two sustainable alternatives are considered and compared: (a) solar thermal coupled with an absorption chiller and (b) evaporative cooling of chilled water using a sub-wet bulb evaporative chiller (SWEC). The former uses a parabolic trough solar field with thermal storage that is connected to a single-effect water/lithium bromide (LiBr) chiller. The field and thermal storage are modeled using NREL’s System Advisor Model software and coupled to in-house Python code for the chiller and process heat exchanger. For the latter option, a novel SWEC is used as a chiller. The energy and water use, and capital cost of the two alternative technologies are presented.

Recently, researchers have focused on molten-salt-based nanofluids, relying on their unique ability to form special fractallike nanostructures due to the interaction between molten salt ionic molecules and the nanoparticles. These nanostructures are thought to be causing the observed heat capacity enhancement. Thus far, this phenomenon was believed to be exclusive to molten salt nanofluids. In this study, the nanostructure observed in molten-salt-based nanofluids is mimicked, and similar fractallike nanostructures were formed in-situ in polyalphaolefin (PAO) oil as the base fluid by dispersing alumina (Al 2 O 3 ) nanoparticles (1% wt. concentration) in the PAO and adding hydroxyl-ended polymer (PPG) (1% wt. concentration) as surfactants to form “artificial” nanostructures by ionically bonding to the nanoparticle’s surface. The effect of these artificial nanostructures was studied to confirm that they affect the base fluid similar to the nanostructures formed in molten salt nanofluids. Results showed an increase of 4.86% in heat capacity, and a 42% increase in viscosity was measured at high shear rates, as well as a noticeable non-Newtonian rheological behavior at low shear rates. These results show that the nanostructure has formed and that the thermophysical and rheological properties of the oil have been affected as expected.

Microalgae have a high biotechnological potential as a source of biofuels (biodiesel, biohydrogen) and other high-added value products (e.g., pharmaceuticals, proteins, pigments). However, for microalgae cultivation to be economically competitive with other fuel sources, it is necessary to apply the concept of biorefinery. This seems to be the most ambitious strategy to achieve viability. Therefore, the objectives of this study were to isolate and identify the main microalgae line used to produce biofuels at Federal University of Parana, Brazil, using the rDNA sequence and micromorphological analysis, and to evaluate the potential of this lineage in the production of hydrogen and co-products with biological activity. For the purification of the lineage (LGMM0001), an aliquot was seeded into solid CHU culture medium and an isolated colony was selected. The genomic DNA was purified using a commercial kit (Macherey-Nagel, Düren, Germany) for molecular identification, the ITS region (ITS1, 5.8S and ITS2) (Internal Transcribed Spacer) was amplified and sequenced using primers LS266 and V9G. Morphological characterization was performed as described by Hemschemeier et al. [1]. Finally, for biological activity research, secondary metabolites were extracted by fractionation and evaluated against bacteria of clinical interest. Through microscopic analysis, general characteristics shared by the genus Tetradesmus were observed. The plasticity of the morphological characteristics of this genus reinforces the need for further studies to classify correctly the species in this group, using DNA sequencing. ITS sequence analysis of LGMM0001 showed 100% homology with sequences from the Tetradesmus obliquus species, so, the lineage was classified as belonging to this species. The evaluated microalgae strain was able to produce hydrogen, showing positive results for gas formation. Biological activity was observed with the extract obtained from the residual culture carried out with alternative medium used in the photobioreactors (PBR), against the Staphylococcus aureus pathogenic lineage. In conclusion, the microalgae strain used in this work was identified as Tetradesmus obliquus (= Acutodesmus obliquus ), and was able to produce a compound with economic potential in association with the existing biofuel production process.

A direct absorption receiver using ceramic particles (CentRec) has been successfully developed by DLR and tested under solar conditions at the Juelich Solar Power Tower, demonstrating receiver outlet temperatures of more than 900 °C. The next step towards commercial application of the technology is to demonstrate a cost-effective, high temperature heat extraction and transfer to a process medium. Besides e.g. steam for electricity generation in a steam turbine, hot air can be used to supply heat to industrial processes with energy demand at high temperature level. A great potential for higher efficiencies and lower costs has been identified for a moving bed heat exchanger. Several concepts of direct contact heat exchangers have been analyzed and evaluated. The selected concept is a combination of several crossflow-sections that are arranged in series with fluid-mixing-chambers between each crossflow-section. Based on the selected design a heat exchanger prototype with 10 kW thermal power and a design air outlet temperature of 750 °C has been built and integrated into a test setup. The test setup provides particles at 900 °C that are heated up electrically inside a hopper on top of the heat exchanger. Hot particles are then moving downwards (moving bed) from the hopper through the direct contact heat exchanger driven by gravity. Cold air supplied by a compressor flows through the particle bed in cross-flow and is heated up. The hot air flow leaves the heat exchanger with a temperature of 750 °C. The particle mass flow is controlled by an oscillating mass flow controller, positioned under the heat exchanger. The cold particles are collected in a container on the bottom. The particle cycle is closed by transporting them back to the hopper. A measurement and control system is implemented to carry out the tests. The test setup has undergone successful commissioning in October and an extensive testing phase started in January 2019. This paper presents the development and manufacturing as well as the successful commissioning of the heat exchanger prototype.

This paper presents an exergy-based sustainability analysis of manufacturing roof tiles from plastic waste in Uganda. Exergy analyses measure the sustainability of industrial processes. This work focuses specifically on the developing country context and on utilizing waste material. A summary of the current plastic waste situation in Uganda, the environmental and health issues associated with plastic waste, current means of recycling plastic waste into new products, and an analysis of the Ugandan roofing market are presented. The motivation for this study is to examine the resources utilized to improve overall exergy efficiency, reduce production costs, and reduce negative environmental impacts. The company, Resintile, is the only manufacturer of roof tiles from plastic waste in Uganda. Their tiles comprised mainly of sand and plastic waste are manufactured in an industrialized process involving drying, extrusion, and pressing. The exergy consumed at each stage including transportation is presented. The extruder consumes the majority of the exergy, but wrapping insulation around the barrel could save over 3 MJ, and a heat engine could provide over 7.5 MJ of usable exergy. The total exergy consumed to produce one batch of seventy-five tiles is over 122 MJ, the potentially recoverable exergy is over 5 MJ (4.3% of consumed exergy), and the realistic recoverable exergy is nearly 10.7 MJ (8.7% of consumed exergy). The realistic can be greater than the potential by adding a heat engine to the sand drying process to generate usable exergy rather than merely recover consumed exergy. Resintile’s plastic roof tiles save a net 86.3 kg of CO 2 from entering the atmosphere per batch of tiles and adoption of the suggested improvements to the manufacturing process would save an additional 3.8 kg of CO 2 per batch.

Computer simulations aid in the design of any device. However, physical testing is still needed to validate these simulations and problems may arise if fabrication limits are not incorporated. This study was undertaken to quantify the losses in a low-solidity turbine rotor designed for less energetic flow. The blade was tested at a scale of 1m resulting in a blade length of 219mm. A 0.5mm minimum thickness fabrication limit was worked with by shifting all the points of the upper surface of the blade sections by 0.5mm at the 219mm scale introducing a huge distortion in each of the blade sections. Lift and drag characteristics of the distorted aerofoil are obtained via ANSYS Fluent and served as the corrected inputs for the BEM characterisation. It was found that the BEM predicts a reduced performance similar to the physical testing although it still over predicts the performance of the turbine. However, there is an agreement on the trend of the simulated performance and the physical testing in addition to the reduction of the variation between the two. Additional aerofoil alterations are studied to inform on future experimental designs. It was then found that out of the altered cases, shifting the upper surface by the required minimum thickness resulted in the best approximation of the simulated performance. This is far from acceptable as the variation between the ideal computer simulated case is too large to just incorporate corrections. Thus, an analysis is carried out using a 400mm scaled blade, thereby decreasing the distortion on each blade section. The results of the analysis show good agreement with the ideal section and minimal reduction in performance at about 5% less than the ideal.

A sodium thermal electrochemical converter (Na-TEC) converts heat directly into electricity without moving parts by isothermal expansion of ions through beta”-alumina solid-electrolyte (BASE). These generators are most similar to thermoelectric generators; however, they are considerably more efficient than the best performing thermoelectric materials. While these heat engines have been considered for CSP applications, literature review found that the efficiency of single-stage Na-TEC could readily achieve 20% even though ideal cycle efficiencies predict above 45% efficiency at elevated temperatures. Thermal parasitic loss has been identified to be responsible for the largest drop in the efficiency. Our recent study shows that staging helps to improve thermal management of the Na-TEC, due to the lower average temperature of the device, which can reduce the thermal parasitic loss. We demonstrate that dual-stage device can improve the efficiency by up to 8% over the best performing single-stage device. We are currently designing and developing a modular dual-stage Na-TEC power block with target efficiency of 33%. We emphasize modularity because this power block can be potentially deployed for both small-scale dish solar, which is appropriate for distributed residential scale (2–3 kWe), and large-scale heliostats and parabolic trough CSP, which is appropriate for centralized industrial scale. A fundamental cost-scaling relationship for this technology was developed based on this design. System variables and component manufacturing methods with material selection for processes were established. The current off-the-shelf component costs indicated an overnight capital cost of $2,044/kWe. The costs of BASE, manufacturing, and electrode preparation have driven the overall price of the module. The paper demonstrates $/W design optimization and cost scaling analysis to reduce the system capital $/W metric below $ 1,500/kWe, with the goal being to achieve the cost target of <900/kWe set by Department of Energy’s Sun Shot Initiative.

One direct absorption receiver concept currently investigated at the DLR is the Centrifugal Particle Receiver (CentRec ® ). Successful tests and promising results of this receiver design have been achieved in a Proof-of-Concept scale with 7.5 kW thermal power and 900°C particle temperature in 2014. Based on these results the prototype has been scaled up to 2.5 MW thermal power for a future pilot plant. Lab tests have been carried out with infrared heaters. In a next step the prototype has been prepared to be tested on-sun in a test setup in the Juelich Solar Tower, Germany. The tests aim to demonstrate high temperature operation and to evaluate the performance of the system. The test setup consists of a centrifugal receiver integrated into the tower and a closed loop particle transport system. The transport system includes an air cooling system to cool down the particles at the receiver outlet, cold particle storage, belt bucket elevator, hopper and particle metering system. While the 2.5 MW th receiver prototype has been developed in a former project, the further infrastructure for the on-sun tests needed to be designed, manufactured and installed. The system is equipped with measurement instrumentation, data acquisition system and control software. Manufacturing of all main components has been completed. Installation of the test setup started in November 2016 and finished in June 2017. Cold and hot commissioning have been carried out from July 2017 until September 2017. On-sun tests started in September 2017. Receiver tests up to 775°C/1,430°F receiver outlet temperature and more than 900°C/1,650°F particle temperature in the receiver have already been achieved. Tests up to 900°C particle outlet temperature are planned at different load levels and will be conducted until summer 2018. This paper describes the test setup for a centrifugal particle receiver system, presenting design, installation and commissioning of the system. It presents test results of first on-sun tests and gives an outlook on further steps regarding solar tests planned for 2018.

This paper presents an application of MRI to measure flow distribution in fuel cell channels. Solid Oxide Fuel Cells (SOFC) are able to efficiently produce electricity directly from the oxidation of the natural gas by electrochemical conversion. The distribution of fuel gas between the high numbers of parallel flow paths within the fuel cell assembly is critically important to ensure high efficiency and uniform conditions within the fuel cell assembly. Practical approaches in conjunction with numerical models are needed to understand and control the physical processes taking place within fuel cells in order to design them to be efficient and reliable. The paper outlines a non-invasive experiment using magnetic resonance imaging (MRI) to measure the distribution of flow within an SOFC subassembly. The method quantifies the flow distribution by modelling the gas using water at Reynolds similar conditions. Water has a magnetic moment that can be imaged using an MRI scanner. Two-dimensional cross-section scans were taken perpendicular to the direction of flow in the fuel cell channel to measure area and velocity. The study evaluated a range of image resolutions and outlined how the data was processed to provide mass flow rates in each channel using the known fluid properties. At the highest image resolution the total mass flow rate was within 1% of the independent measurement from the experimental rig. The distribution of flow between the channels showed a similar trend to the computational model. The initial results demonstrate the feasibility for the method to measure flow in the SOFC channels.

The chlor-alkali industry produces significant amounts of hydrogen as byproduct and an interesting benefit can be obtained by feeding hydrogen to a PEM fuel cell unit, whose electricity and heat production can cover part of the chemical plant consumptions. The estimated potential of such application is up to 1100 MW el installed in the sole China, a country featuring a large presence of chlor-alkali plants. This work presents the modeling, development and first experimental results from field tests of a 2 MW PEM fuel cell power plant, built within the European project DEMCOPEM-2MW and installed in Yingkou, China as the current world’s largest PEM fuel cell installation. After a preliminary introduction to the market potential of PEM Fuel cells in the chlor-alkali industry, it is first discussed an overview of project’s MEA and fuel cell development for long life stationary applications, focusing on the design-for-manufacture process and the high-volume manufacturing route developed for the 2MW plant. The work then discusses the modeling of the power plant, including a specific lumped model predicting FC stack behavior as a function of inlet streams conditions and power set point, according to regressed polarization curves. Cells performance decay vs. lifetime reflects long-term stack test data, aiming to evidence the impact on overall energy balances and efficiency of the progression of lifetime. BOP is modeled to simulate auxiliaries consumption, pressure drops and components operating conditions. The model allows studying different operational strategies that maintain the power production during lifetime, minimizing efficiency losses; as well as to investigate the optimized operating setpoint of the plant at full load and during part-load operation. The last section of the paper discusses the experimental results, through a complete analysis of the plant performance after plant startup, including energy and mass balances and allowing to validate the model. Cumulated indicators over the first nine months of operations regarding energy production, hydrogen consumption and efficiency are also discussed.

The Industrial Assessment Center at University of Wisconsin-Milwaukee (WM-IAC) has implemented over 100 industrial energy, waste, and productivity assessments, and has recommended $9.5 million of energy and operational savings with about 950 recommendations since it was re-established in 2011. This paper analyzes the assessments, and the recommendations were performed over two years only, 2014 and 2015. During these two years, a total of 40 assessments were created by visiting different manufacturing facilities with the analysis of the data gathered and processed. The determinants of the data were the number of recommendations, recommended energy savings (in kWh/year), recommended energy cost savings (in US$/year), implemented energy savings (in US$/year), the Standard Industrial Code (SIC) and the groups of Energy Efficiency Opportunities (EEOs). Such an analytical study was meant to reveal the significance of EEO groups through a variety of SICs in terms of the potential for energy savings, particularly focused towards choosing plant facilities for IAC assessments. Additionally, this paper could be considered as a guide for plant managers, energy engineers and other personnel involved in the energy assessment process. Conclusions are inferred with respect to the most promising EEOs that can be resolved based on the characteristics of the manufacturing plants visited. The information investigated can pave the way for composing energy demanding industries and expose priority goal areas regarding minimizing the energy consumption.

Hydrogen generation in solar photoelectrochemical reactors could provide an important contribution to future energy regimes by storing intermittent renewable energy in a versatile energy vector. Using waste water as electron donor potentially facilitates economic operation. Here, organic contaminants instead of water are oxidised at the anode and two products of value are obtained simultaneously: hydrogen and clean water. Three different reactor concepts were compared in terms of ohmic losses. Based on the results of the simplified analysis a novel planar and scalable solar reactor with an aperture area of 368 cm 2 was developed. It features a perforated photocathode and a non-perforated photoanode, both cold gas sprayed, in tandem arrangement and accepts electrolyte temperatures of up to 80°C. Confirmed by ray-tracing simulations the slit design of the photocathode allows homogeneous illumination of the two involved photoelectrodes with DLR’s test platform SoCRatus (Solar Concentrator with a Rectangular Flat Focus). The photocathode compartment and the photoanode compartment are separated by a membrane. Thus, the membrane being located in the optical path has to show sufficiently high transparency for solar light, particularly in the UV-Vis range. A 1,418 h aging study was performed in order to assess the optical performance of a Nafion™ membrane N1110 exposed to an aqueous mixture at 80°C, which contained 10 vol.-% methanol as a model substance for organic contaminants and sulfuric acid to adjust pH 3. It could be verified that the membrane maintains high transparency in the considered wavelength region from 280 nm to 1,100 nm which suggests the feasibility of the reactor concept. The design electrolyte flow of 2.5 l/min through each of the two reactor chambers practically allows isothermal operation on the SoCRatus under 17.5-fold concentrated irradiation. The inlet and outlet geometry of the reactor aims at uniform flow patterns, a low pressure drop as well as effective product gas transport and was optimised for automatic manufacturing. Reference electrodes and temperature sensors are incorporated directly in the reactor body for extended analysis and operation options. The parts of the reactor ensure compatibility with a wide range of waste waters and involved chemicals as well as mechanical stability. Moreover, they are resistant to light exposure and weathering.

Development is underway for modifications to an existing central receiver power tower concentrator solar power research facility to accommodate a new solar chemical test module. Optical analysis, using Sol Trace, is done to model the existing heliostat field, general tower geometry, and planned system layout to predict the incident irradiation to the new experimental receiver called the Solar Reducer Receiver Reactor (SR3). Within the SR3, a layer of particles flowing over an inclined plane will be highly irradiated to chemically reduce the particulate. To accommodate the inclined plane reactor geometry, a beam down mirror will be modeled. An estimated 1000 suns will be required at the aperture. Currently, the field typically provides around 300 suns over a 1 m × 1 m area. To achieve the required higher flux, a secondary concentrator will concentrate the irradiation from a larger area into a smaller focal spot. Rather than using an expensive compound parabolic design, a series of flat plate petals will instead be used to create a cost effective secondary. The flat plate design also provides added benefits for ease of installation, manufacturing, and cooling. The ray tracing model is used to compare several design parameters including the number of petals, petal length, aperture size and the inclination angle of the petals for the secondary. With these parameters selected, designs have been created for a test module to be constructed at King Saud University’s Riyadh Techno Valley CSP Tower. Additionally, the model is used to estimate the necessary cooling needed to operate both the secondary concentrator and the beam down mirror. These models will be tested experimentally using several quartz heaters. The beam down will be cooled by forced convection air, while the secondary concentrator will use water cooling. Lab experiments will measure the feasibility and effectiveness of the proposed cooling before construction. Once these proof of concepts tests have been completed, construction of the secondary concentrator and beam down mirror will begin to allow for testing in 2018.

Thin film solar cells (TFSC) differ from the conventional wafer solar cell panels in that they are a fraction of the thickness, hence they boast reduced material costs, lighter weight, and possible flexibility. To improve their light-trapping and absorption efficiency, manufacturers currently use nanometer scale texturing. When manufacturing nano textured thin film solar cells in the substrate configuration, the back reflector is also textured. It has been observed that a textured back reflector leads to parasitic light absorption in silicon solar cells. This occurrence reduces the back reflector effectiveness, and thus reduces absorption in the absorber layer and overall efficiency. However, there is little to no similar research done for thin film (CdTe/CdS) solar cells devices. In this work, wave optical analyses of thin film CdTe/CdS solar cells with and without nano texturing on the metal back reflectors were simulated using ANSYS ANSOFT High Frequency Structural Simulator (HFSS). The optical analyses yielded percentage absorptions for unit cells with four absorber thicknesses range between 250- to 1000 nm, with and without a textured back reflector over six wavelengths range from 360nm to 860 nm, and with 3 different back contact metals (Au, Ag, and Al). It was noted that the textured back contacts show a substantial increase in the absorption in the active CdTe layer in the infrared range. Additionally, back reflector texturing increases the parasitic absorption in the metal back reflector layer as well, especially with ultrathin absorber layer. It was also found that additional parasitic absorption due to a textured back reflector has less of an impact on absorption as the active absorber thickness increases to 500 nm, 750 nm, or 1000 nm. Finally, silver (Ag) as back contact outperforms both aluminum (Al) and gold (Au). This finding might be crucial to solar cell manufacturers because it could possibly be an overlooked factor in achieving higher efficiencies for relatively thin cells.

In the sugar mill in Tanegashima which is an isolated island in Japan, raw sugar production process produces raw sugar and bagasse simultaneously. Raw bagasse is not storable because of its perishability due to high moisture content. Actually, the bagasse boiler burns more bagasse than that is required for the sugar mill. Hence, the temperature of flue gas increases and a massive amount of unused heat at around 200 °C is exhausted during sugar mill operation period. On the other hand, many other factories in this island burn imported oil at package boilers to generate process steam up to 120 °C all year around. To resolve this spatial and seasonal mismatch, we employed thermochemical energy storage and transport system using zeolite steam adsorption and regeneration cycle. We introduced a basic design of heat release device which is called “Zeolite boiler”, that is a moving bed with indirect heat exchanger. Adsorbed steam is assumed to be generated by a package boiler. A small zeolite boiler with 20 kg/h of zeolite was designed by using a developed quasi-2D simulation code that numerically solves mass and heat conservation equations of the counter-flow reactor model. As the result of single injection from the top of chamber, the zeolite boiler could generate 4.95 kg/h of dry saturated steam at 0.2 MPa when 4.0 kg/h of steam was injected from the package boiler. Multi injection process was considered to improve the heat recovery rate. By injecting 3.0 kg/h and 1.0 kg/h of steam separately from the top and the middle of the chamber, 5.9 kg/h of steam was generated and heat recovery rate was increased by 13 points.

In this study, prototype electrodynamic dust shield (EDS) devices large enough to cover commercial photovoltaic (PV) modules were fabricated and tested in the lab and in the field. The EDS device consisted a polyethylene terephthalate (PET) substrate with screen-printed silver electrodes, and a PET cover sheet that bonded to the substrate using a synthetic rubber adhesive. The voltage-current characteristics of the EDS device was measured while square wave high voltage was applied to the device, so as to determine the power consumption of the EDS device. The EDS device was also tested in the field to determine its effectiveness in soiling mitigation. Measurements showed that the EDS capacitance varied from approximately 600 pF in the air-conditioned lab to 2 nF in the field when the EDS device temperature reached 45 °C. The variation of the capacitance has significant relevance to the capacity requirements for the high voltage sources needed to energize the EDS device and its power consumption. Under laboratory conditions, the EDS power consumption was found to be 0.3 W m −2 at 6 kV p-p and 1 Hz, and roughly proportional to the voltage squared. In the field test electrode damage was observed, due to electrical discharge at the electrode lines. As a result, the EDS operation did not show significant effect of soiling mitigation. The results of this study are useful for designing high voltage sources for EDS operation, and for modifying the design and fabrication methods in order to produce EDS devices that can effectively repel dust in the field.

Supercritical carbon dioxide (sCO2) Brayton power cycles have the potential to significantly improve the economic viability of concentrating solar power (CSP) plants by increasing the thermal to electric conversion efficiency from around 35% using high-temperature steam Rankine systems to above 45% depending on the cycle configuration. These systems are the most likely path toward achieving the Department of Energy’s (DOE) Office of Energy Efficiency and Renewable Energy (EERE) SunShot targets for CSP tower thermal to electric conversion efficiency above 50% with dry cooling to air at 40 °C and a power block cost of less than 900 $/kWe. Many studies have been conducted to optimize the performance of various sCO2 Brayton cycle configurations in order to achieve high efficiency, and a few have accounted for drivers of cost such as equipment size in the optimization, but complete techno-economic optimization has not been feasible because there are no validated models relating component performance and cost. Reasonably accurate component cost models exist from several sources for conventional equipment including turbines, compressors, and heat exchangers for use in rough order of magnitude cost estimates when assembling a system of conventional equipment. However, cost data from fabricated equipment relevant to sCO2 Brayton cycles is very limited in terms of both supplier variety and performance level with most existing data in the range of 1 MWe power cycles or smaller systems, a single completed system around 7 MWe by Echogen Power Systems, and numerous ROM estimates based on preliminary designs of equipment for 10 MWe systems. This data is highly proprietary as the publication of individual data by any single supplier would damage their market position by potentially allowing other vendors to undercut their stated price rather than competing on reduced manufacturing costs. This paper describes one approach to develop component cost models in order to enable the techno-economic optimization activities needed to guide further research and development while protecting commercially proprietary information from individual vendors. Existing cost models were taken from literature for each major component used in different sCO2 Brayton cycle configurations and adjusted for their magnitude to fit the limited vendor cost data and estimates available. A mean fit curve was developed for each component and used to calculate updated cost comparisons between previously-reviewed sCO2 Brayton cycle configurations for CSP applications including simple recuperated, recompression, cascaded, and mixed-gas combined bifurcation with intercooling cycles. These fitting curves represent an average of the assembled vendor data without revealing any individual vendor cost, and maintain the scaling behavior with performance expected from similar equipment found in literature.

Bi-directional turbines convert oscillating axial fluid flow into uniform radial rotation and have proven effective in wave energy harvesting applications, like ocean wave generators. Two of the most widely studied designs for these scenarios are the Wells and axial turbines. This study characterizes the effectiveness of these turbines for use with a thermoacoustic generator; which is a relatively new technology that uses an induced temperature gradient to propagate acoustic waves within an enclosed, looped chamber. These generators are widely applied to refrigeration cycle systems; yet when paired with a bi-directional turbine, the resulting sound wave can be harnessed to generate electricity. This paper begins with a discussion of the thermoacoustic application covering relevant issues for the turbine. Next, the Wells, axial, and a combined hybrid turbine are presented in thorough detail including governing design features that were explored. Fabrication of a test fixture and turbine prototypes and experimental results from a broad ranging study of the performance of the turbine designs is shown. Finally, conclusions from the obtained results are discussed.