Energy Dispatch Model for Integrated Waste-to-Energy Plant

The energy consumed by buildings for air conditioning accounts for a large percentage of global energy consumption. To promote efficiency and sustainability, the scientific community is making great efforts to develop renewable technologies. A well-known but unfortunately underestimated solution is the development of centralized heating and cooling systems that consistently reduce energy consumption.The work proposes a comparison between three heating configurations covering the demand of a settlement in the Latvian region: 1) centralized district heating (DH) system; 2) 5th generation district heating & cooling (5GDHC) system and 3) individual home heating (HH) systems. Thermal and electrical loads are evaluated by transient simulations of a residential area with 80 buildings for the Riga climate and compared with the same settlement in a Mediterranean region (Milan, IT). The energy plants are based on different technologies: combined heat and power (CHP) plants, gas-fired boilers, and domestic heat pumps.The analysis includes the option of power exchange with the national grid. A transient numerical model has been developed for each solution. Every component is modelled according to performance maps provided by the manufacturers, allowing an accurate simulation in both design and off-design operating conditions. The study includes energy, economic and environmental aspects.The result of the simulation highlights the large difference between the two locations, not only in terms of annual load, but also in terms of load distribution. On an annual basis, the Latvian residential complex requires almost twice as much energy as the Italian one. The thermal losses in the district systems are 4.21% in Milan solution and 5.65% in Riga. The district heating system coupled with heat pump represents the best layout in terms of primary energy consumption in both locations, with energy savings of 50% compared to other solutions. The use of 5GDHC is a good compromise that could increase the use of renewable energy. The adoption of cogeneration plant is a good choice in case of centralized district system that allows the installation of high efficiency genset. On the contrary, for small application as residential, the installation of cogeneration system results expensive and the conversion efficiency does not justify the installation.

A system with several actors will increase the possibilities for collaboration and therefore, in many cases also increase the possibilities to affect the operation with economic and environmental benefits. In this paper a district heating system is studied with purpose to create economic and environmental operation guidelines in favour of the involved actors. The company LuleKraft owns a combined heat and power plant, while the four heating stations together with the DH network are owned by Luleå Energi. District heat is produced from the CHP plant and the four heating stations which are fired with process gases from an integrated steel plant, oil, wood pellets or electricity. The heat demand in the system is strongly depending on the outdoor temperature. In this paper, the system is modelled with Mixed Integer Non Linear Programming in order to optimise the profit and CO2 emission. A comparison between actual process data and modelled results is performed. A pareto front is derived to show the trade-off between economic benefits and CO2 emissions. It is found that the main suggestions, under conditions for optimised profit, are (1) to prioritize effective heat production instead of electricity production at cold outdoor temperatures and (2) redistribution of the accessible process gases between the CHP plant and one of the heating stations. This will lead to an improved operation strategy, resulting in increased profit and reduced energy consumption.

Metamorphoses of cogeneration-based district heating in Romania: A case study

China has the largest population (1.33 billion) on Earth and a 2010 GDP of $5.4 trillion. This nation has experienced rapid economic growth in the last decade that has been accompanied by the generation of an enormous amount of municipal solid wastes. From 2000 to 2009, the reported MSW increased by 33% to 157 million tons. This paper presents the current situation in MSW generation, characterization, and means of disposal, based on the results of studies by WTERT (www.wtert.org) in China. The landfills serving the large cities of China are reaching or have already reached full capacity and there is strong government support for the waste to energy (WTE) alternative, resulting in over 90 WTE plants built or under construction. The thermal treatment technologies are based mostly on imported or domestic grate combustion technologies and on fluid bed combustion of shredded wastes. Of particular interest to the WTERT studies have been the Air Pollution Control systems used in Chinese plants and their performance, in particular the dioxin and furan levels attained, in view of continuing public opposition to WTE in Beijing and some other cities. The cities of Guangzhou, Shanghai, and Beijing were visited to examine any obstacles to further expansion of the WTE industry in China. There are extreme differences in the composition of MSW as well as waste management from region to region. It is believed that one of the reasons for public opposition to WTE projects is inadequate transparency as to the emissions of WTE plants. Also, it appears that some WTE facilities tend to cut down costs at the expense of adequate emission control. The paper concludes with discussion of the economics of Chinese WTE plants built in the last six years.

Dynamic response of gravity-driven flow in multi-section absorption heat pump

The decentralisation of existing district heating systems by network separation is a promising approach for district heating transformation. A district heating network is separated into several smaller district heating network structures that can be individually adapted, e.g. in relation to the existing network structure or concerning the properties of the local buildings supplied, such as the temperature requirements of their heating systems. In this work, an approach for the optimal separation of existing district heating networks is expanded, which enables the decentralisation of a specific district heating system and the partial transformation of the separated network depending on the heat source utilised and the local district heating system conditions. The approach first identifies coherent network areas through community detection and aggregation, then optimises network separation and the installation of heat pumps, and finally evaluates the arising district heating network systems through district heating network simulations. The individual steps of this approach are adapted to be applicable to large district heating network structures, e.g. to handle the great number of separation options. The approach is applied to two existing district heating systems with over four thousand buildings supplied. Two types of utilised waste heat sources are investigated, a sewage plant with fluctuating temperatures and an electrolyser with a dynamic operation schedule. The results show favourable transformation alternatives for existing district heating networks, as the separated network areas are transformed by reducing supply temperatures depending on the heat source potential utilised and the temperature requirements of the buildings supplied. • Separating district heating networks facilitates the utilisation of heat sources. • An optimisation model reveals the optimal separation of district heating networks. • The network separation considers available heat capacity and temperature level. • Heat pumps are installed in the separated network to utilise low-temperature heat. • A subsequent simulation evaluates the separated district heating networks.

As the second-largest city in Taiwan, the Kaohsiung municipality has faced serious environmental loadings in recent decades. Among them, waste management is a key issue because of large amount of urban and industrial waste produced daily. In this regard, waste-to-energy (WTE) systems adopting the best available control technology for air pollution is a win-win approach because it also generates electricity to mitigate the dependence on imported fossil fuels and the greenhouse gas emissions incidentally. In this work, the updated status of municipal solid waste (MSW) and WTE plants in Kaohsiung were analyzed to get the crux based on the official database. Using the operational data on the WTE plants over recent years (2003–2018), the analysis of operational efficiencies for the four WTE plants in Kaohsiung was addressed in the paper. It showed that their operational efficiencies, ranging from 0.287 to 0.568 kW-h/kg, indicated an approximate “bathtub curve” pattern. In addition, analyzing the project for revamping the Gangshan WTE plant showed a significant progress in operational efficiencies with a significant increase from 0.506 kW-h/kg in 2016 to 0.587 kW-h/kg in 2018. Finally, some recommendations on technological measures and regulatory incentives for upgrading the operational efficiencies of existing WTE plants were addressed in the work.

Techno-economic model for district heating systems

Comparative Analysis Between District Heating and Geothermal Heat Pump System

The use of computational modeling has become very popular and important in many engineering and physical fields, as it is considered a fast and inexpensive technique to support and often substitute experimental analysis. In fact system design and analysis can be carried out through computational studies instead of experiments, that are typically demanding in terms of cost and technical resources; sometimes the systems characteristics and the technical problems make the experiments impossible to perform and the use of computational tools is the only feasible option. Demand of resources for realistic simulation is increasing due to the interest in studying complex and large systems. In these framework smart modeling approaches and model reduction techniques play a crucial role for making complex and large system suitable for simulations. Moreover, it should be considered that often more than one simulation is requested in order to perform an analysis. For instance, if a heuristic method is applied to the optimization of a component, the model has to be run a certain number of times. The same problem arises when a certain level of uncertainty affect the system parameters; in this case also many simulation are required for obtaining the desired information. This is the reason why the use of technique that allows to obtain compact model is an interesting topic nowadays. In this PhD thesis different reduction approaches and strategies have been used in order to analyze three energetic systems involving large domain and long time, one for each reduction approach categories. In all the topic considered, a smart model has been adopted and, when data were available, tested using experimental data. All the model are characterized by large domain and the time involved in the analysis are high in all the cases, therefore a method for compact model achievement is used in all the cases. The considered topics are: • Groundwater temperature perturbations due to geothermal heat pump installations, analyzed trough a multi-level model. • District heating networks (DHN), studied from both the fluid-dynamic and thermal point of view and applied to one of the larger network in Europe, the Turin district heating system (DHS), trough a Proper Orthogonal Decomposition - Radial Basis Function model. • Forest fire propagation simulation carried out using a Proper Orthogonal Decomposition projection model.

Recovering energy from waste in Sweden—a systems engineering study

The present work proposes a comparison between three solar-powered district heating and cooling systems, namely: 1) centralized district heating & cooling (DHC) system; 2) 5th-generation district heating & cooling (5GDHC) system and 3) individual AC plants (HHC, Home Heating and Cooling), in different climate conditions. Thermal loads are evaluated by transient simulations of a residential compound featuring 56 detached houses for three different Italian climates: (1) a Mediterranean region on the seaside (Palermo, I), (2) a temperate climate in Central Italy (Roma, I), and (3) a cold-temperate climate in Northern Italy (Bolzano, I). The DHC system shows the highest efficiency in terms of energy-savings, whatever the location. The 5GDHC system reaches a compromise between installation and operational costs.

Promoting efficient district heating in Estonia

Machine-learning-based multi-step heat demand forecasting in a district heating system

Two air vents situated on a heat transport pipe in district heating system were exposed to the same environment for 10 years. However, one air vent was more corroded than the other. It also had a hole on the top of the front-end pipe. Comparative analysis was performed for these air vents to identify the cause of corrosion and establish countermeasures. Through experimental observation of the damaged part and analyses of powders sampled from air vents, it was found that corrosion was initiated at the top of the front-end pipe. It then spread to the bottom. Energy dispersive X-ray spectroscopy results showed that potassium and chlorine were measured from the corroded product in the damaged air vent derived from rainwater and insulation, respectively. The temperature of the damaged air vent was maintained at 75 ~ 120 °C by heating water. Rainwater-soaked insulation around the front-end pipe had been hydrolyzed. Therefore, the damaged air vent was exposed to an environment in which corrosion under insulation could be facilitated. In addition, ion chromatography and inductively coupled plasma measurements indicated that the matrix of the damaged front-end pipe contained a higher manganese content which might have promoted corrosion under insulation.