scholarly journals Wastewater Treatment Plants as Local Thermal Power Stations—Modifying Internal Heat Supply for Covering External Heat Demand

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1981
Author(s):  
Florian Kretschmer ◽  
Bernd Hrdy ◽  
Georg Neugebauer ◽  
Gernot Stoeglehner
Keyword(s):  
Wastewater Treatment ◽  
High Temperature ◽  
Low Temperature ◽  
Feasibility Study ◽  
Heat Recovery ◽  
Heat Supply ◽  
Wastewater Treatment Plants ◽  
Internal Heat ◽  
District Heating ◽  
Gas Combustion

To counteract climate change, the application of renewable energy sources and their efficient use are of crucial importance. In this context, wastewater has also gained increased attention in recent years. For decades, wastewater treatment plants have applied the heat from digester gas combustion to supply internal demands. However, in the context of efficient energy use the question arises: can using high temperature heat for supplying low temperature demand still be considered the best option? This article presents an innovative approach to covering wastewater treatment plant (WWTP) internal demand with low temperature wastewater heat recovery, making thermal energy from digester gas combustion available for feed-in to a local high temperature district heating network. The presented feasibility study was carried out in an Austrian municipality and investigates the heat balance, the economic risk, climatic benefits and the social aspects of the suggested approach. The practical implementation of the novel approach was planned in two steps. First, the WWTP should be connected to the district heating network to enable the feed-in of excess heat. Second, the WWTP internal heat supply should be modified and based on wastewater heat recovery from the effluent. Due to the promising results of the feasibility study, the first step was realized in summer 2020. The second and final step was initiated in 2021.

scholarly journals Technology Pathways and Economic Analysis for Transforming High Temperature to Low Temperature District Heating Systems

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3218
Author(s):  
Pedro Durán ◽  
Herena Torio ◽  
Patrik Schönfeldt ◽  
Peter Klement ◽  
Benedikt Hanke ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Renewable Energy ◽  
High Temperature ◽  
Low Temperature ◽  
Economic Analysis ◽  
District Heating ◽  
Heating System ◽  
District Heating System ◽  
Heating Systems ◽  
District Heating Systems

There are 1454 district heating systems in Germany. Most of them are fossil based and with high temperature levels, which is neither efficient nor sustainable and needs to be changed for reaching the 2050 climate goals. In this paper, we present a case study for transforming a high to low temperature district heating system which is more suitable for renewable energy supply. With the Carnot Toolbox, a dynamic model of a potential district heating system is simulated and then transformed to a low temperature supply. A sensitivity analysis is carried out to see the system performance in case space constrains restrict the transformation. Finally, an economic comparison is performed. Results show that it is technically possible to perform the transformation until a very low temperature system. The use of decentralized renewable sources, decentralized heat storage tanks and the placement of a heat pump on each building are the key points to achieve the transformation. Regarding the sensitivity analysis, the transformation is worth doing until the seasonal storage and solar collector field sizes are reduced to 60% and 80% of their values in the reference case, respectively. The economic analysis shows, however, that it is hard for highly efficient low temperature renewable based heat networks to compete with district heating systems based on a centralized fossile CHP solution. Thus, though the presented transformation is technically possible, there is a strong need to change existing economic schemes and policies for fostering a stronger promotion of renewable energy policies in the heat sector.

Performance Improvement of a Combined Power and Cooling Cycle for Low Temperature Heat Sources Using Internal Heat Recovery and Scroll Expander

2019 ◽  
Author(s):  
Martina Leveni ◽  
Arun Kumar Narasimhan ◽  
Eydhah Almatrafi ◽  
D. Yogi Goswami
Keyword(s):  
Low Temperature ◽  
Heat Recovery ◽  
Pressure Ratio ◽  
Internal Heat ◽  
Operating Conditions ◽  
Maximum Efficiency ◽  
Water Mixture ◽  
Heat Sources ◽  
Scroll Expander ◽  
Temperature Heat

Abstract Low temperature heat sources inherently result in lower cycle efficiencies, which can be improved by means of combined power and cooling generation. In order to produce power and cooling, appropriate thermodynamic cycles and working fluids must be used. Goswami cycle is a combined cycle that produces power and refrigeration by using ammonia-water mixture for low temperature heat sources. In the present study, a scroll expander is modeled specifically for the cycle operating conditions and a theoretical investigation is conducted to determine the cycle performance. A scroll expander design suitable for the operating conditions improves the power output and thereby overall thermal efficiency. The scroll expander efficiency varied between 0.05 and 0.61 for the pressure ratio between 2.2 and 8.6, with a maximum efficiency of 0.697 achieved at a pressure ratio of about 4.4. An internal heat recovery from the rectifier is proposed along with a flow split in the strong solution and analyzed for overall cycle energy efficiency improvement. Internal heat recovery from the rectifier increased the first law effective efficiency and the effective exergy efficiency by 7.9% and 7.8%, respectively, over the basic configuration.

Structural Analysis and Optimization of Transition Section of Convex Tube Sheet

2016 ◽  
Vol 853 ◽  
pp. 356-360
Author(s):  
Zun Chao Liu ◽  
Ke Wang ◽  
Tong Liu ◽  
Wei Feng Xu ◽  
Min Shan Liu
Keyword(s):  
Thermal Stress ◽  
High Temperature ◽  
Low Temperature ◽  
Heat Recovery ◽  
Sheet Thickness ◽  
Heat Recovery Boiler ◽  
Tube Sheet ◽  
Section Thickness ◽  
Shell Side ◽  
Transition Section

The convex tube sheet which is used in heat recovery boiler consists of three parts: the high temperature tube sheet, the low temperature tube sheet and the transition section.Three-dimensional finite element model of convex tube sheet in new type of heat recovery boiler is established in this paper. Using the ANSYS Workbench software, thermal stress of the convex tube sheet is analyzed. The temperature fields and thermal stress distribution of convex tube sheet are obtained, and its structure strength is checked. The effects of the high temperature tube sheet thickness, low temperature tube sheet thickness and transition section thickness on the maximum equivalent stress of the convex tube sheet are analyzed. The results show that: temperature of most parts of convex tube sheet is close to the tube side fluid temperature, and the large temperature gradient only existed in the thinner regions of shell side of convex tube sheet; temperature distribution shows obvious skin effect. At the transition section, the temperature along the thickness direction is more evenly distributed, with little change in temperature gradient; larger thermal stress mainly concentrated at tube layout area which close to the shell side of the high temperature tube sheet and the connecting parts of transition section and low temperature tube sheet in the tube side. Through checking the strength intensity, convex tube sheet structural strength meets the requirements.The transition section thickness are optimized. The optimum thickness of the transition section analyzed in this paper is 31mm.

Waste heat recovery from a data centre and 5G smart poles for low-temperature district heating network

Energy ◽  
2021 ◽  
Vol 218 ◽  
pp. 119468
Author(s):  
A. Khosravi ◽  
T. Laukkanen ◽  
V. Vuorinen ◽  
S. Syri
Keyword(s):  
Low Temperature ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
District Heating ◽  
Data Centre

scholarly journals Technical problems with compression units in mechanical vapour recompression systems

2018 ◽  
Vol 70 ◽  
pp. 03006
Author(s):  
Władysław Kryłłowicz ◽  
Krzysztof Kantyka ◽  
Włodzimierz Szewczyk ◽  
Paweł Pełczyński
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Heat Recovery ◽  
Technical Problems ◽  
University Of Technology ◽  
Working Medium

The evidence gathered during works on two prototype heat recovery systems is summarised. The first installation is a low-temperature vapour recompression system, whereas the second is a high-temperature (from an industrial viewpoint) installation. Vapour-contaminated air is the working medium. The authors focused their attention on machine issues mainly. All compressors described below were designed at the Lodz University of Technology.

scholarly journals From the Wastewater Treatment Plant to the Turnstiles of Urban Water and District Heating Networks

2020 ◽  
Vol 2 ◽  
Author(s):  
Wolfgang Gruber-Glatzl ◽  
Christoph Brunner ◽  
Sarah Meitz ◽  
Hans Schnitzer
Keyword(s):  
Wastewater Treatment ◽  
Heat Pump ◽  
Wastewater Treatment Plants ◽  
Treatment Plant ◽  
District Heating ◽  
Heat Pumps ◽  
Reference Scenario ◽  
Selling Price ◽  
Price Ratio ◽  
Heating Networks

Wastewater treatment plants (WWTP) are among the largest energy consumers in municipalities and cause high operating costs. At the same time, many WWTPs produce biogas and have immense untapped potential for the integration of heat pumps (HP). District heating operators are looking for new possibilities to diversify their heat production portfolio and to provide cheap and clean heat to their customers. In our work, we investigate the case study of the WWTP Gleisdorf (Austria) and propose a combination of biogas utilization and heat pump integration to deliver heat for all internal thermal processes as well as to a 1,000 m heat connection line (HCL) toward the district heating network. The net annual costs of different scenarios were calculated for economic comparison. Negative net annual costs mean net annual savings. The reference scenario (biogas combined heat and power, no HCL, no HP; net annual costs of −51,000 €/year) is compared with three different heat pump integration options (HP-IO). The HP-IOs are considering different hydraulic connections, flow temperatures, and heat exchanger placement. The HP-IO-1 focuses on the low-temperature internal demands, but proves to be too limited to balance out the high cost of the HCL. HP-IO-2 operates at higher temperatures (75°C) leading to the lowest efficiency, but ultimately achieving the lowest net annual costs (−57,700 €/years with a 750 kWth HP). HP-IO-3 uses a serial heating concept trying to take advantage of lower flow temperatures while also delivering heat to the district heating network. At 300–400 kWth this leads to net annual costs of −50,100 €/years. The price ratio of 0.5 (40 €/MWh selling price of heat to 80 €/MWh purchasing price of electricity) are varied to analyze the sensitivity of the results. HPs already play an increasing role in the district heating sector, using sewage water as a heat source. The combined analysis of biogas utilization, HP integration options and the thermal as well as electrical demands of WWTP and district heating networks allow the determination of the most viable option.

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