Application of an Exhaust Heat Recovery System for Domestic Hot Water

Typically there is a great deal of waste heat available in drainage system of large-scale public bathhouses, such as public bathhouses in schools, barracks and natatoriums. The paper advances a heat pump system used in bathhouses for exhaust heat recovery. The system consists of solar energy collection system, drainage collection system and heat pump system for exhaust heat recovery. In the system, tap water is heated by energy from solar energy collection system, and is used as hot water for bathing at the beginning. At the same time, drainage collection system collects sewage from bathhouses, and then electric heat pump starts up and recovers the exhaust heat in sewage and heats the tap water. In this way, heat is recycled. Practical operation of the system was introduced, and drainage temperature as well as equipment capacity was optimized based on a practical example. Compared with gas-fired (oil-fired, coal-fired, electric) boilers, the system has advantages of lower energy consumption, less pollution and lower operating cost. Therefore, the system has great superiority in energy conservation and has a good application prospect.

Operation of a CCHP System Using an Optimal Energy Dispatch Algorithm

The Combined Cooling, Heating, and Power (CCHP) systems have been widely recognized as a key alternative for thermal and electric energy generation because of the outstanding energy efficiency, reduced environmental emissions, and relative independence from centralized power grids. Nevertheless, the total energy cost of CCHP systems can be highly dependent on the operation of individual components and load balancing. The latter refers to the process of fulfilling the thermal and electrical demand by partitioning or “balancing” the energy requirement between the available sources of energy supply. The energy cost can be optimized through an energy dispatch algorithm which provides operational/control signals for the optimal operation of the equipment. The algorithm provides optimal solutions on decisions regarding generating power locally or buying power from the grid. This paper presents an initial study on developing an optimal energy dispatch algorithm that minimizes the cost of energy (i.e., cost of electricity from the grid and cost of natural gas into the engine and boiler) based on energy efficiency constrains for each component. A deterministic network flow model of a typical CCHP system is developed as part of the algorithm. The advantage of using a network flow model is that the power flows and efficiency constraints throughout the CCHP components can be readily visualized to facilitate the interpretation of the results. A linear programming formulation of the network flow model is presented. In the algorithm, the inputs include the cost of the electricity and fuel and the constraints include the cooling, heating, and electric load demands and the efficiencies of the CCHP components. This algorithm has been used in simulations of several case studies on the operation of an existing micro-CHP system. Several scenarios with different operational conditions are presented in the paper to demonstrate the economical advantages resulting from optimal operation.

Tank Design for On-Board Hydrogen Storage in Metal Hydrides

The aim of this work is to reduce the refueling time of a metal hydride storage tank by improving its design, taking in account the total volumetric and mass capacity of the tank. A heat and mass transfer model is proposed and solved to obtain the charging curve for 1 kg hydrogen in a LaNi5 reference storage tank. Compared to gas transport and reaction kinetics, heat transfer is found to limit the hydrogen charging dynamics of the storage tank. To improve the refueling time, it is found to be necessary to increase first of all the heat transfer inside the metal hydride bed, and subsequently the heat transfer from the metal hydride bed to the cooling fluid. Technical solutions such as the implementation of aluminum foam and/or internal heat exchanger tubes are investigated. By combining both solutions, the refueling time can be reduced from 400 minutes (reference tank) to 15 minutes. The tank volume still meets the DOE targets, but its mass remains a problem. Therefore, new materials with improved gravimetric capacity have to be developed. With this work it is now possible to improve the tank design for newly developed storage materials and to evaluate their potential for technical applications.

Performance Evaluation of Concentrating Solar Cooker Under Indian Climatic Conditions

The work presented in this paper essentially consists of modeling and analysis of energy and exergy efficiency of a community solar cooker, installed at Holistic Health and Food Centre, I.I.T. Delhi India in March 1998. The cooker is meant for community cooking, which consists of a linear parabolic concentrator with concentration ratio of 20. The experiments, on this cooker, were performed in summer and winter, both the climatic conditions. The measurements were done by using microprocessor based on line data acquisition system using class I solar pyranometer and Pt. 100 temperature sensors. Based on the experimental data obtained by testing and performance evaluation of this concentrating type of solar cooker, the energy and exergy efficiencies are calculated. From an analysis of the experimental values the average efficiency of this cooker is measured as 14% only. The different losses contributes to low efficiency are optical losses (16%), geometrical losses (30%) and thermal losses (35%) accounts for more than, 80% energy waste from the radiation coming to the reflector. The rest of the losses are due to edge losses etc. the maximum temperature of water was recorded 98°C during water heating tests.

Demonstration of an Energy Meter Using a Pump Flow Station

Heating and cooling energy consumption measurements are critical for operations, controls, and fault detection and diagnosis of heating, ventilation and air conditioning (HVAC) systems. Generally water flow has to be measured in order to determine energy consumption in either chilled water systems or hot water systems. Economical and accurate water flow measurements are essential to develop energy meters. Since pump performance relates actual pump water flow to pump head and power, theoretically water flow through a pump can be determined by other pump performance characteristics, such as pump head and motor power. This paper presents the theoretical model of pump flow stations based on pump head and motor power, and the experiments and results of a cooling energy meter using a pump flow station developed on the chilled water system at a facility.

Development of a Program in Innovative and Sustainable Design of Automotive and Building Technologies

This paper describes the development of a program in Innovative and Sustainable Design that focuses on transportation and building systems. Transportation and buildings consume approximately 75% of the energy used in the US and significantly contribute to the technical issues related to sustainable energy sources and the environment. The program will be organized into four areas that revolve around the nucleus of innovation, sustainability, and design processes: namely, research, educational, outreach, and collaborative arms. Research teams will design highly efficient buildings, vehicles, and mobility systems for the future. Students will learn design approaches to address the needs for energy-neutral building technologies and an efficient, environmentally friendly transportation system fueled by sustainable energy sources. Outreach efforts will recruit secondary school and community college students into engineering programs and expand visibility for the program. Collaborative projects will provide students and faculty with opportunities to work with engineers, designers, and scientists from other universities, government institutions, and industry on timely and technically important projects.

Potential of Industrial Solid Wastes as an Energy Source and Gaseous Emissions Evaluation in a Pilot Scale Burner

Biomass is currently used as an alternative energy source in some industries. Due to problems with disposal of wastes, using biomass as an energy source is economically and environmentally attractive. In this work seven wastes from textile and food industry were characterized and their gaseous emissions resulting from their combustion in a pilot unit were measured. The aim of this paper is to evaluate the usage of industrial wastes as an energy source taking into account their composition and gaseous emissions when submitted to combustion tests. Gaseous emissions were compared to limits imposed by Brazilian and international current legislations. Volatile organic compounds (VOC) were analyzed by GC-MS and their content values were expressed as total organic carbon (TOC). Four combustion tests were carried out in a cyclone combustor and all TOC emissions were below regulations limits. CO, CO2, NOx, CxHy and SO2 were also measured. Chemical properties showed that the volatile matter values of all biomass were high what indicate that the solids burn rapidly and some biomass presented high levels of sulphur and consequently high levels of emission of SO2 when burned. The lower heating values ranged from 14.22 to 22.93 MJ.kg−1. Moisture content and particulate matter (PM) were measured during the combustion tests and showed effective combustion conditions. Thermogravimetric analysis of the biomasses showed ignition temperatures and maximum burning rate which were compared to other papers data. The usage of these biomasses as an energy source is possible however gas treatment would be required specially if the solid presents high levels of sulphur and chlorine.

Integrated Energy Strategy: A Case for Sustainability

The Integrated Energy Strategy (IES) is a systemic approach to pursue several goals by applying technologies that have not been integrated before. The concept was to maximize the use of proven technologies that reduce the risk while focusing on the key enabling developments that leverage the benefits of a systems approach. Each of the component operations illustrated in the paper will be part of the US energy infrastructure in the future. Additional economies of scale and advantages of earlier availability result from the APS-NETL approach. The future of America’s energy infrastructure must support utilities becoming leaders in transitions rather than just forced customers of risky solutions.

Conversion of Wet Ethanol to Syngas and Hydrogen

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 (H2) have the potential to meet this goal. Biofuels are attractive because they can be domestically produced and consume carbon dioxide (CO2) during the feedstock growth cycle. Hydrogen is appealing because its use emits no CO2, 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 (CH4). Although effective, this process still produces CO2. 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 (C2H5OH) 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 (O2) is 1 mole of ethanol for every 3 moles of oxygen: C2H5OH+3O2↔2CO2+3H2O 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.

The Performance Improvement of a 70kWe Natural Gas CHP System

It is well known that combined heating and power (CHP) generation permits the energy of the fuel to be more efficiently than electric and thermal separate generation. The paper deals with natural gas CHP system with a 70kWe gas-powered internal combustion engine (ICE), which has been set up at the Tsinghua University energy-saving building, in Beijing, China. The system is composed of an ICE, a flue gas heat exchanger and other heat exchangers. The conventional system’s characteristics is that the gas engine generates power on-site, and the exhaust of the gas engine is recovered by a high temperature flue gas-water heat exchanger, and the jacket water heat is recovered by a water-water heat exchanger to supply heat for district heating system. In order to improve the system’s performance, an innovative system with absorption heat pump is adopted. The exhaust of the gas engine drives an absorption heat pump to recover the flue gas sensible heat and further recover the latent heat, so the outlet temperature of the exhaust could be lowered to 50°C. In this paper, the electrical and thermal performance of the innovative system were tested and compared with conventional cogeneration systems. The test and comparison results show that the innovative CHP system could increase the heat utilization efficiency 10% in winter. All the results provide important insight into CHP performance characteristics and could be valuable references for CHP system’s improvements.