Improving combined cycle power plant performance in arid regions

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.In arid regions, where cooling water supplies are limited and highly regulated, combined cycle power plants (CCPPs) are turning to air-cooled condensers instead of water-cooled condensers. However, performance of air-cooled condensers can decline as ambient temperatures increase and result in loss of steam turbine power output. At the same time, as ambient temperature rises, net output of the gas turbine also can decline due to increased power consumption by the compressor and reduced power output by the gas turbine. In this paper, it is proposed to remedy these problems by pre-cooling the inlet air to the air-cooled condenser as well as the compressor, using a low-temperature thermal energy storage (TES) system. The TES is maintained around 5ºC by an absorption refrigeration system driven by the waste heat in the stack gases. A thermodynamic analysis of a 500-MW CCPP incorporating the above concept is presented.vk201

BiofilmScanner: A Computational Intelligence Approach to Obtain Bacterial Cell Morphological Attributes from Biofilm Image

Desulfovibrio alaskensis G20 (DA-G20) is utilized as a model for sulfate-reducing bacteria (SRB) that are associated with corrosion issues caused by microorganisms. SRB-based biofilms are thought to be responsible for the billion-dollar-per-year bio-corrosion of metal infrastructure. Understanding the extraction of the bacterial cells' shape and size properties in the SRB-biofilm at different growth stages will assist with the design of anti-corrosion techniques. However, numerous issues affect current approaches, including time-consuming geometric property extraction, low efficiency, and high error rates. This paper proposes BiofilScanner, a Yolact-based deep learning method integrated with invariant moments to address these problems. Our approach efficiently detects and segments bacterial cells in an SRB image while simultaneously invariant moments measure the geometric characteristics of the segmented cells with low errors. The numerical experiments of the proposed method demonstrate that the BiofilmScanner is 2.1x and 6.8x faster than our earlier Mask-RCNN and DLv3+ methods for detecting, segmenting, and measuring the geometric properties of the cell. Furthermore, the BiofilmScanner achieved an F1-score of 85.28% while Mask-RCNN and DLv3+ obtained F1-scores of 77.67% and 75.18%, respectively.Comment: Submitted to Pattern Recognitio

Global Environmental Engineering for and with Historically Marginalized Communities

Marginalized communities lack full participation in social, economic, and political life, and they disproportionately bear the burden of environmental and health risks. This special issue of Environmental Engineering Science, the official journal of the Association of Environmental Engineering and Science Professors (AEESP), reports research on the unique environmental challenges faced by historically marginalized communities around the world. The results of community-based participatory research with an Afro-descendant community in Columbia, Native American communities in Alaska, United States, villagers in the Philippines, disadvantaged communities in California, United States, rural communities in Mexico and Costa Rica, homeless encampments in the San Diego River (United States) watershed entrepreneurs in Durban, South Africa, and remote communities in the island nation of Fiji are presented. The research reported in this special issue is transdisciplinary, bringing engineers together with anthropologists, sociologists, economists, and public health experts. In the 13 articles in this special issue, some of the topics covered include inexpensive technologies for water treatment, novel agricultural strategies for reversing biodiversity losses, and strategies for climate change adaptation. In addition, one article covered educational strategies for teaching ethics to prepare students for humanitarian engineering, including topics of poverty, sustainability, social justice, and engineering decisions under uncertainty. Finally, an article presented ways that environmental engineering professors can engage and promote the success of underrepresented minority students and enable faculty engaged in community-based participatory research

Dual-purpose power-desalination plant augmented by thermal energy storage system

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.This paper presents a novel application of a sensible Thermal Energy Storage (TES) system for simultaneous energy conservation and water desalination in power plants. First, the TES mitigates negative effects of high ambient temperatures on the performance of air cooled condenser (ACC) that cools a 500 MW combined cycle power plant (CCPP); next, the same TES satisfies the cooling requirements in a 0.25 mgd multi-effect distillation (MED) plant. Stack gases from CCPP are used to drive an absorption refrigeration system (ARS) which maintains the chilled water temperature in a TES tank. A process model integrating CCPP, ARS, TES, and MED has been developed to optimize the volume of the TES. Preliminary analysis showed that a tank volume of 2950 m3 was adequate in meeting the cooling requirements of both ACC and MED in both hot and cold seasons. The proposed TES has the potential to save 2.5% of the power loss in a CCPP/ACC on a hot summer day. Further, our modeling results reveal that a desalination capacity of 0.25-0.43 mgd can be achieved with top brine temperatures between 100 ºC and 70 ºC of MED. The proposed integrated system, process modeling and simultaneous advantages of enhanced CCPP performance and sustainable desalination system will be discussed in the presentation.dc201

Self-sustainable electricity production from algae grown in a microbial fuel cell system

© 2015 The Authors. This paper describes the potential for algal biomass production in conjunction with wastewater treatment and power generation within a fully biotic Microbial Fuel Cell (MFC). The anaerobic biofilm in the anodic half-cell is generating current, whereas the phototrophic biofilm on the cathode is providing the oxygen for the Oxygen Reduction Reaction (ORR) and forming biomass. The MFC is producing electricity with simultaneous biomass regeneration in the cathodic half-cell, which is dependent on the nutrient value of the anodic feedstock. Growth of algal biomass in the cathode was monitored, assessed and compared against the MFC power production (charge transfer), during this process. MFC generation of electricity activated the cation crossover for the formation of biomass, which has been harvested and reused as energy source in a closed loop system. It can be concluded that the nutrient reclamation and assimilation into new biomass increases the energy efficiency. This work is presenting a simple and self-sustainable MFC operation with minimal dependency on chemicals and an energy generation system utilising waste products and maximising energy turnover through an additional biomass recovery

A sustainable performance assessment framework for circular management of municipal wastewater treatment plant

Municipal wastewater treatment plants (WWTPs) could become valuable contributors to a circular economy by implementing the 3R principles (reduce, reuse, and recycle). While reducing the pollution load of sewage is the primary objective of a WWTP, this process generates several potentially valuable byproducts including treated effluent, biogas, and sludge. The effluent can be reused in various end use applications and biogas can be reused as a fuel (for electricity generation, transportation, and cooking) or a chemical feedstock. The sludge can either be directly recycled as soil conditioner or via thermochemical/biochemical processing routes to recover material (e.g., hydrochar), energy (e.g., heat, and syngas), and resource value (phosphorus). This work presents a five-layered assessment framework for quantitatively evaluating the sustainable value of municipal WWTPs by using life cycle assessment (LCA) and life cycle costing assessment (LCCA) tools. In addition, indicators reflecting potential benefits to stakeholders and society arising from investments into municipal WWTPs such as the private return on investment (PROI) and the environmental externality costs to investment ratio (EECIR). The framework is validated in a hypothetical case study where the sustainable value of a circularly managed municipal WWTP is evaluated in situations involving multiple byproduct utilization pathways. Four future circular options (FCOs) are examined for a 50,000 m3/d capacity WWTP treating sewage up to tertiary standards. The FCOs mainly differ in terms of how biogas is reused (to meet the WWTP's internal energy demands, as cooking fuel, or as fuel for city buses after upgrading) and how sludge is recycled (as soil conditioner or by producing hydrochar pellets for electricity generation). The FCO in which treated effluent is reused in industry, biogas is used as cooking fuel, and sludge is used as a soil conditioner provides the greatest sustainable value (i.e., the lowest private costs and environmental externality costs (EEC) together with high revenues), the highest PROI, and the lowest EECIR. The strengths and limitations of the proposed assessment framework are also discussed. © 2022 The Author

Semantic Image Segmentation Using Scant Pixel Annotations

The success of deep networks for the semantic segmentation of images is limited by the availability of annotated training data. The manual annotation of images for segmentation is a tedious and time-consuming task that often requires sophisticated users with significant domain expertise to create high-quality annotations over hundreds of images. In this paper, we propose the segmentation with scant pixel annotations (SSPA) approach to generate high-performing segmentation models using a scant set of expert annotated images. The models are generated by training them on images with automatically generated pseudo-labels along with a scant set of expert annotated images selected using an entropy-based algorithm. For each chosen image, experts are directed to assign labels to a particular group of pixels, while a set of replacement rules that leverage the patterns learned by the model is used to automatically assign labels to the remaining pixels. The SSPA approach integrates active learning and semi-supervised learning with pseudo-labels, where expert annotations are not essential but generated on demand. Extensive experiments on bio-medical and biofilm datasets show that the SSPA approach achieves state-of-the-art performance with less than 5% cumulative annotation of the pixels of the training data by the experts

A sustainable performance assessment framework for circular management of municipal wastewater treatment plants

Municipal wastewater treatment plants (WWTPs) could become valuable contributors to a circular economy by implementing the 3R principles (reduce, reuse, and recycle). While reducing the pollution load of sewage is the primary objective of a WWTP, this process generates several potentially valuable byproducts including treated effluent, biogas, and sludge. The effluent can be reused in various end use applications and biogas can be reused as a fuel (for electricity generation, transportation, and cooking) or a chemical feedstock. The sludge can either be directly recycled as soil conditioner or via thermochemical/biochemical processing routes to recover material (e.g., hydrochar), energy (e.g., heat, and syngas), and resource value (phosphorus). This work presents a five-layered assessment framework for quantitatively evaluating the sustainable value of municipal WWTPs by using life cycle assessment (LCA) and life cycle costing assessment (LCCA) tools. In addition, indicators reflecting potential benefits to stakeholders and society arising from investments into municipal WWTPs such as the private return on investment (PROI) and the environmental externality costs to investment ratio (EECIR). The framework is validated in a hypothetical case study where the sustainable value of a circularly managed municipal WWTP is evaluated in situations involving multiple byproduct utilization pathways. Four future circular options (FCOs) are examined for a 50,000 m3/d capacity WWTP treating sewage up to tertiary standards. The FCOs mainly differ in terms of how biogas is reused (to meet the WWTP's internal energy demands, as cooking fuel, or as fuel for city buses after upgrading) and how sludge is recycled (as soil conditioner or by producing hydrochar pellets for electricity generation). The FCO in which treated effluent is reused in industry, biogas is used as cooking fuel, and sludge is used as a soil conditioner provides the greatest sustainable value (i.e., the lowest private costs and environmental externality costs (EEC) together with high revenues), the highest PROI, and the lowest EECIR. The strengths and limitations of the proposed assessment framework are also discussed