Wastewater heat utilization through heat pumps: The case study of City of Rijeka

Đurđević, Dinko; Balić, Dražen; Franković, Bernard

doi:10.1016/j.jclepro.2019.05.235

Cited by 28 publications

(12 citation statements)

References 25 publications

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“…It can be used to heat digesters or even for sludge drying. Moreover, it can be used outside to heat nearby buildings or greenhouses [250]. Another factor that significantly affects the efficiency of the process is the variation in the flow and temperature of the effluent since, currently, the most widespread heat pumps have a single operating speed.…”

Section: Heat Pumps: Thermal Energy Recoverymentioning

confidence: 99%

Towards the Implementation of Circular Economy in the Wastewater Sector: Challenges and Opportunities

Guerra-Rodríguez

Oulego

Rodríguez

et al. 2020

Water

125

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The advancement of science has facilitated increase in the human lifespan, reflected in economic and population growth, which unfortunately leads to increased exploitation of resources. This situation entails not only depletion of resources, but also increases environmental pollution, mainly due to atmospheric emissions, wastewater effluents, and solid wastes. In this scenario, it is compulsory to adopt a paradigm change, as far as the consumption of resources by the population is concerned, to achieve a circular economy. The recovery and reuse of resources are key points, leading to a decrease in the consumption of raw materials, waste reduction, and improvement of energy efficiency. This is the reason why the concept of the circular economy can be applied in any industrial activity, including the wastewater treatment sector. With this in view, this review manuscript focuses on demonstrating the challenges and opportunities in applying a circular economy in the water sector. For example, reclamation and reuse of wastewater to increase water resources, by paying particular attention to the risks for human health, recovery of nutrients, or highly added-value products (e.g., metals and biomolecules among others), valorisation of sewage sludge, and/or recovery of energy. Being aware of this situation, in the European, Union 18 out of 27 countries are already reusing reclaimed wastewater at some level. Moreover, many wastewater treatment plants have reached energy self-sufficiency, producing up to 150% of their energy requirements. Unfortunately, many of the opportunities presented in this work are far from becoming a reality. Still, the first step is always to become aware of the problem and work on optimizing the solution to make it possible.

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Section: Heat Pumps: Thermal Energy Recoverymentioning

confidence: 99%

Towards the Implementation of Circular Economy in the Wastewater Sector: Challenges and Opportunities

Guerra-Rodríguez

Oulego

Rodríguez

et al. 2020

Water

125

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“…[ 13–15 ] The refrigerant type is R134A. [ 15–32 ] The electricity consumed by systems is provided by coal‐fired power plants.…”

Section: System Descriptionmentioning

confidence: 99%

“…Theoretical calculations presented by Dinko Đurđević et al have shown that the low‐grade thermal energy from reclaimed water could be considered as a feasible solution to cover a significant share (75.24 MWt) of heat generation capacity in Rijeka (104 MWt), through district heating system. [ 20 ]…”

Section: Introductionmentioning

confidence: 99%

A Novel District Heating System Coupled with Reclaimed Water Source Heat Pump: Energy, Economic, Environmental, and Application Analysis

Wang

Zhang

et al. 2022

Energy Tech

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Wastewater treatment plants (WWTPs) are an energy-intensive industry. The high energy consumption of WWTPs is detrimental to achieving carbon neutrality. Wastewater treatment accounts for an estimated 3.4% of annual electricity consumption in the United States, nearly 1% of the total electricity consumption in Germany, and 0.25% of the total electricity consumption in China. [1][2][3] The unit electricity consumption for wastewater treatment in the aforementioned countries is around 0.52, 0.40, and 0.254 kWh m À3 , respectively. [3] The volume and standard of wastewater treatment will be further improved due to the increase in urban population and more stringent environmental protection requirements, [4] which will bring higher energy consumption. To achieve the energy balance of wastewater treatment, it is necessary to recover energy from resources contained in wastewater. [5] In the early period, most of the energy recovery of wastewater concentrated on organic matter in wastewater. Organic energy in wastewater is about 9-10 times higher than that used to treat wastewater. [6] Researchers have explored the potential of biogas generated from sludge for power generation at the national level. [7,8] For example, the vast majority of existing biogas plants in Sweden are located in WWTPs, which almost accounts for 60% of the total biogas production (3 PJ year À1 ). [7] Anaerobic digestion plays an important role for its abilities to further transform organic matter into biogas. [9,10] However, anaerobic sludge digestion systems tend not to be well operated in developing countries. For example, less than 100 WWTPs in China (3% of all plants) use biogas from anaerobically digested sludge to generate heat and electricity. [11] Co-digestion with kitchen or other organic wastes is currently only applied on a laboratory scale in China. [12] The chemical energy extracted from the wastewater depends not only on the amount of biodegradable chemical oxygen demand (COD) in the wastewater, but also on the conversion efficiency of chemical energy in CHP system. Hao et al. think based on a BNR-WWTP (an AAO process; Q ¼ 600 000 m 3 d À1 ), only about 13% (0.20 kWh m À3 ) of the theoretical chemical energy (1.54 kWh m À3 at COD ¼ 400 mg L À1 , in the influent of the evaluated WWTP) can be converted into electricity and heat. [5] The thermal energy recovery potential of wastewater was significantly higher than that of chemical energy. [13] In northern China, the wastewater temperatures are 10-16 °C. [13][14][15] The large amount of low-grade thermal energy from wastewater is not fully utilized. The untreated wastewater will scale at the heat exchanger, which will affect the heat transfer effect, so treated

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“…Many publications have focused on the upgradation of LGE, such as absorption refrigeration, , desalination, , heat pump, , heat pipe, , and power generation. − Jouhara et al , recently comprehensively reviewed the recovery methods of WE and advanced technologies for industrial processes. Imran et al thoroughly reviewed the volumetric expander applications for LGE recovery using the organic Rankine cycle and comparatively assessed their advantages and disadvantages.…”

Section: Introductionmentioning

confidence: 99%

“…Many publications have focused on the upgradation of LGE, such as absorption refrigeration, 13,14 desalination, 15,16 heat pump, 17,18 heat pipe, 19,20 and power generation. 21−23 Jouhara et al 24,25 recently comprehensively reviewed the recovery methods of WE and advanced technologies for industrial processes.…”

Section: Introductionmentioning

confidence: 99%

Sustainable Retrofit Design of Natural Gas Power Plants for Low-Grade Energy Recovery

Tang

Chen

et al. 2019

Ind. Eng. Chem. Res.

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Large amounts of low-grade energy in natural gas power plants are not being efficiently recovered or used. They are often emitted directly to the environment. It is quite challenging to retrofit natural gas power plants for the integration of low-grade energy recovery and further optimize power generation, production and supply of hot and cold energy, and pipeline networks for cold energy distribution as a total site. In this study, we present a process superstructure for the sustainable retrofit of natural gas power plants to recover low-grade energy and deliver it to different users. The waste energy sources include cold energy from liquefied natural gas, pressure energy from pipeline natural gas streams, and lowgrade heat from low-pressure steam in power plants. A mixed integer nonlinear programming framework is formulated to optimize the process structure to minimize the total annual cost and maximize the exergy efficiency to obtain the best sustainable retrofit process for low-grade energy recovery. The optimization framework includes models of the existing gas turbines and boilers and the new pipeline network and refrigeration system. The mathematical framework is applied to a real industrial example, and the power consumption for cold energy production is significantly reduced by 32%. The ratio of different energy sources and the distance of cold energy distribution are investigated, and different optimization results are analyzed. Finally, exergy analysis is suggested to evaluate the sustainability of the retrofit. According to the results of the exergy analysis, the total exergy efficiency under the minimum total annual cost is increased by 6.172%.

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Wastewater heat utilization through heat pumps: The case study of City of Rijeka

Cited by 28 publications

References 25 publications

Towards the Implementation of Circular Economy in the Wastewater Sector: Challenges and Opportunities

Towards the Implementation of Circular Economy in the Wastewater Sector: Challenges and Opportunities

A Novel District Heating System Coupled with Reclaimed Water Source Heat Pump: Energy, Economic, Environmental, and Application Analysis

Sustainable Retrofit Design of Natural Gas Power Plants for Low-Grade Energy Recovery

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