Waste heat is mostly a waste of time

Analysis of Low-Grade Waste Heat Driven Systems for Cooling and Power for Tropical Climate

  The most widely accepted concept of energy balance in the volume of the urban canopy layer is expressed by the following equation,Q* + QF = QH + QE + ΔQS + ΔQAwhere Q* is the net all-wave radiation, QF  the anthropogenic heat flux, QH the turbulent sensible heat flux, QE the latent heat flux, ΔQS the net storage heat flux and ΔQA the net advective heat flux.Through observations and simulations targeting a residential area in Tokyo, this study proposes revisions to the above conventional concept for energy balance in the following two respects.1. QF  should be interpreted not as the anthropogenic exhaust heat released to the urban atmosphere but as energetic bulk input to the urban canopy where QF  is equivalent to heat resulting from fuels combustion and electricity consumption with usually negligible metabolic heat there.2. Instead, actual anthropogenic exhaust heat should be treated as components of the turbulent heat fluxes (QH and QE) using the following equation,QH = QHb + QHt + QHswhere QHb is the net building anthropogenic heat consisting of waste heat from HAC (heating and air conditioning) systems and exchanged heat between indoors and outdoors through ventilation, QHt the anthropogenic heat from traffic and QHs the turbulent sensible heat flux (convection) from the urban surfaces. The same concept holds true for the latent heat.   The above revisions are applied in this study to the full energy flow analysis for the residential urban canopy in Tokyo using the eddy covariance CO2 flux and O2 & CO2 concentrations measurements, together with fine resolution (time and space) inventory data of electricity use and car traffic. Through the analysis, we estimate QF  by source (electricity, liquid and gas fuel) and each component of the turbulent heat fluxes (QHb, QHt and QHs). Finally, those observation-based estimates are compared with the simulations with a focus on QHb. The authors’ multi-layer urban canopy model coupled with the building energy model is used for the simulations. Resultantly, observation-based components of urban energy balance show good agreement with those from simulations including QHb, suggesting the validity of the authors’ revisions to the conventional urban surface energy balance concept.

Enhancing the waste heat utilization of industrial park: A heat pump-centric network integration approach for multiple heat sources and users

Liquid Thermocells Enable Low-Grade Heat Harvesting

An overview on adsorption cooling systems powered by waste heat from internal combustion engine

Assessment of waste and renewable heat recovery in DH through GIS mapping: The national potential in Italy

Chapter 6 - Liquid-based electrochemical systems for the conversion of heat to electricity

Energy consumption in the urban environment impacts the urban surface energy budget and leads to the emission of anthropogenic sensible heat and moisture into the atmosphere. Anthropogenic heat and moisture emissions vary significantly both in time and space, and are not readily measured. As a result, detailed models of these emissions are not commonly available for most cities. Furthermore, most attempts to quantify anthropogenic emissions have focused on the sensible heat component, largely ignoring moisture emissions and invoking assumptions—such as the equivalence of energy consumption and anthropogenic sensible heating—which limit the accuracy of the resulting anthropogenic heating estimates. This paper provides a historical perspective of the development of models of energy consumption in the urban environment and the associated anthropogenic impacts on the urban energy balance. It highlights some fundamental limitations of past approaches and suggests a roadmap forward for including anthropogenic heat and moisture in modelling of the urban environment. Copyright © 2010 Royal Meteorological Society

Anthropogenic heat variation during the COVID-19 pandemic control measures in four Chinese megacities

A waste heat assessment of a manufacturing facility was conducted. A physical survey identified potential waste heat sources. For these sources, the temporal fluctuations in temperature and flowrate, and the frequency of occurrence of the waste heat, were determined from measurements, calculations, and company records. The energy and exergy of the waste heat were calculated. The total annual waste heat is 36.5 TJ of energy, which represents 0.84 TJ of exergy. The boiler, plant vacuums, and chiller comprise 96% of the energy rejected and are the major contributors to the rejected exergy. Using the waste heat for space heating is evaluated. Based on fuel consumption in the boiler, the annual energy for space heating is estimated at 8.5 TJ. Theoretically, waste heat from the boiler flue, polypropylene dryers, and plant vacuums could meet up to 39% of this energy without storage. Simply allowing the vacuum exhausts to cool in the building could theoretically meet up to 27%. Models are developed to investigate using waste heat recovery and thermal energy storage (TES) to provide space heating for a prototype warehouse building, and estimates for the initial costs of the recovery system are developed. Modeling indicates that TES is highly beneficial for matching short-term demand fluctuations and for smoothing the temporal oscillations in the waste heat. A nine-month heating season is simulated to determine the fraction of the load met by the recovery system. A small amount of thermal storage, e.g., 12.5–25% of daily waste heat, improved the fraction of demand that could be met. Larger sizes had diminishing returns and significantly increased the initial cost and payback period. To reduce initial cost, a refined recovery system design that uses a TES as an intermediate and for storage is proposed. The study highlights the need to consider fluctuations in the waste heat supply and sink demand, for thermal storage, and to identify relatively simple modifications to recover waste heat.

Thermodynamic performance comparison between ORC and Kalina cycles for multi-stream waste heat recovery

A waste heat assessment of a manufacturing facility with low-quality waste heat is conducted. A physical survey identified seven potential waste heat sources with fluid exhausts: the boiler flue, the chiller loop for the HVAC system, the exhaust from polypropylene dryers, from the compressed air dryer, from the plant vacuums, and from an electroplating air handler, and the deaerator. The temporal fluctuations in temperature and flow rate, and the frequency of occurrence of the waste heat, were determined from measurements, calculations, and company records. Variations were observed in the boiler flue and in the dryers. The monthly energy and exergy of the waste heat were calculated for a reference temperature of 25 °C. The total annual waste heat is calculated to be 36.5 TJ of energy which represents 0.84 TJ of exergy. The boiler, plant vacuums, and chiller comprise 96% of the energy rejected and are the major contributors to the rejected exergy. Matching the waste heat to space heating is evaluated. Based on fuel consumption in the boiler, the annual energy for space heating is estimated 8.5 TJ. Waste heat from the boiler flue, polypropylene dryers, and plant vacuums could meet up to 39% of this energy without storage and 63% with thermal storage to better overlap waste heat supply with demand. Simply allowing the vacuum exhausts to cool in the building could theoretically meet up to 27%. The study highlights the need to consider fluctuations in the waste heat supply and sink demand, the need for thermal storage, and identifying relatively simple modifications to recover waste heat.

The present scenario is like that the need of the electrical energy is growing rapidly whereas the resource availability is lagging behind the load demand due to its extinction which leads to hinder our overall generation. It has been observed that the sustainable resources have great future potential to take lead to generate power and supply demand. In the present scenario there exists a few energy resources equivalent to fuel resource. So, there must be a technology to trap the waste and unutilized heat available in the atmosphere and utilize it into the form useful electrical energy. In the current situation, waste heat in the form of thermal energy is recovered and converted into conventional electrical energy. Today, 70% of produced energy in automobiles is wasted in form of heat by exhaust gases. The main outcome of this paper is to manage the waste heat is being generated in the vehicles efficiently, by introducing the concept of “Thermo Electric Generator” (TEG) which convert the waste heat produced inside the vehicles and Re-Generate in the form electric current and give it back to the “storage unit” due to “Seebeck effect” concept.

This paper deals with climate change mitigation and addresses waste heat reuse as a measure which is until now considered only to a limited extent. The City of Vienna serves as a case study to explore potentials to improve the urban heat supply using waste heat as an additional energy source. As no observation data about waste heat and detailed heating demand is available, this data is derived from proxy data for estimating waste heat reuse potential and residential heating demand patterns. Heat requirements for manufacturing and service provision is explored and, based on the distribution of the companies within the city, mapped as waste heat sources. Employees per company serves as proxy data to allocate the heat volume. Waste heat share and temperature ranges is reviewed from literature. Heating demand is mapped based on floor space of the buildings by age class and building type. Merging supply and demand maps allows to quantify the residential heating demand coverage through local waste heat in the potential supply areas within different distance ranges and housing density classes. In high density housing areas, only a small share of the demand can be covered by waste heat supply even within 250 m distance from sources due to few companies which could provide waste heat. In medium to low density housing areas in Vienna’s outer districts with more industry, a higher share of residential heating demand near the sources can be covered by waste heat within a 250 m distance. Within a 500 m distance, around half of the residential heating demand can be covered only in low density housing areas near the waste heat sources.

Работа большинства предприятий промышленного комплекса сопровождается выработкой большого количества низко потенциального вторичного (сбросного) тепла, которое никак не используется, а просто теряется, выбрасываясь в атмосферу. Сбросное тепло имеет небольшую температуру, отличающуюся от температуры окружающей среды на 30 - 50°C, поэтому его использование обычным путем затруднено, но это тепло обладает большой энергией и вырабатывается в больших объемах. Поэтому утилизация вторичного тепла является важной технико-экономической задачей. В настоящее время одной из наиболее эффективных и перспективных технологий для утилизации сбросного тепла - является Органический Цикл Ренкина (ОЦР). The operation of the majority of enterprises of the industrial complex is accompanied by the production of a large amount of low potential secondary (waste) heat, which is not used in any way, but is simply lost, being thrown into the atmosphere. Waste heat has a small temperature, which differs from the ambient temperature by 30 - 50 ° C, so it is difficult to use it in the usual way, but this heat has a lot of energy and is generated in large volumes. Therefore, the utilization of waste heat is an important technical and economic task. Currently, one of the most efficient and promising technologies for waste heat utilization is the Organic Rankine Cycle (ORC).