Abstract

Additional water storage is modeled in concentrated and distributed configurations in a case study water distribution system model of Cleveland, Tennessee, U.S.A. This is done to understand: if there are energy generation capabilities from increased storage, and if new water demand modeled to represent a doubling population can be supported by additional water storage. Model outputs show that the distributed water storage configuration increases water system resiliency to population growth, meeting doubled water demand. The concentrated storage configuration cannot meet doubled water demand, due to the inability of the design to manage pressure and deliver water across the space-and-time continuum. Both scenarios are unable to meet water demands and maintain pressures while also generating energy. This research concludes that the primary motivation for adding additional water storage (e.g., for energy generation or to withstand chronic population growth) should determine additional tank locations and configurations.

Abstract

The global climate is currently undergoing vast changes due to the high concentrations of carbon dioxide within the atmosphere. This is already evident through the occurrence of more extreme weather events around the globe. Consequently, in this work the impact of climate change on highly weather dependent electricity systems is assessed by quantifying the extreme needs for dispatchable energy. Large-scale weather data with 3 hourly resolution, from the EURO-CORDEX project are used, reflecting three different projections of the Intergovernmental Panel on Climate Change of possible climate outcomes for the 21^st century. It is found that the end-of-century period projected by two representative concentration pathways, RCP2.6 and RCP4.5, slightly increases the need for dispatchable backup energy. On the other hand, the RCP8.5 emission scenario leads to more significant increases. The demand for dispatchable energy happens to occur temporally highly clustered which introduce challenges to the electricity systems. Energy storage may be applied to handle the extreme electricity demands. To investigate this possibility, a simple theoretical modelling of energy storage is presented.

Abstract

In this research paper, design strategies of retrofitting activities were evaluated based on specified district sustainability indicators. The main objective is to identify the existing conditions of the selected district within the scope of applied indexes to develop new strategies for retrofitting. The district is represented by 3 buildings with 20,000 m² conditioned area which contains similar building characteristics as remaining residential buildings in the city. Accordingly, energy models of selected buildings were created and analyzed where hourly dynamic simulation tool was used to assess energy indicators. The intention is to have detailed calculations of the energy index with reference to indoor comfort, greenhouse gas emission and the economical index with reference to return on investment. The findings of this assessment reveal a number of significant implications for the improvement of the overall building performance. The most explicit finding of this study is to show that 65% energy saving, correspondingly 69 kg/m²year greenhouse gas emission reduction with 5.16 years return on investment can be achieved by the well-defined and precisely calculated district sustainability indicators.

Abstract

The energy system in Europe changes towards a smart energy system with interconnection of heat, power and gas networks, increasing the flexibility and efficiency. Combined heat and power units play an important role in such systems, since they have a high total efficiency and enable the interconnection between the networks. Yet, control concepts are needed to ensure an optimal operation planning of available capacities. The resulting unit commitment problem can be approached with mixed-integer linear programming. This paper presents a generic modelling method of coupled and decoupled combined heat and power units with mixed-integer linear programming. Furthermore, operation data of two steam turbine types are compared with the model performance to demonstrate the feasibility of this modelling approach. Finally, a model of a combined cycle is presented, derived from the presented method.

Abstract

As a step towards sustainable energy management systems, energy providers use various demand side management techniques to reduce fluctuations in consumer energy demand. Dynamic pricing schemes encourage consumers to shift their energy usage patterns from peak hours towards off-peak periods, but here usually the active participation of consumers is anticipated. Smart household devices, which can autonomously shift their time of operation, can efficiently support such demand side management techniques. In this paper an adaptive model-based control scheme is proposed to create intelligent cost-aware household appliances, which can change their behaviour to minimize the cost of consumed energy and at the same time provide the required quality of service.
The controller utilizes the dynamically changing energy price list, published ahead by the energy provider, thus it cooperatively supports demand side management. The proposed methods are evaluated in a case study, utilizing a household refrigerator. The proposed adaptive model predictive controller can save 5-10% of the energy bill, according to simulation results.

                                                                                                                                                                                                                                                 

Abstract

Due to the new technologies development based on renewable sources of energy, in recent years Stirling engines have become very important in the energetic sector. Many of them do not allow the use of fluid lubricants and, thus, the effect of friction losses is important. For this purpose, a mathematical model has been developed based on the force balance in the crankshaft using the pressure distribution in the cylinders. The aim of this work is to characterize the mechanical losses in a Genoa 03 Stirling engine using a numerical model and experimentally via the drag method. The results of this model have been compared with those obtained experimentally on Genoa 03 Stirling engine. In the experimental results, a proportional increase in friction torque due to the average pressure and the speed of the crankshaft is observed. The first of these is caused by an increase of dry friction forces and the second, by the viscous friction between the working fluid and the inner walls of the engine. Also in this paper, irreversible processes in a beta type Stirling engine have been investigated in order to highlight the impact of losses on mechanical power and its performance. This article develops the first study of the mechanical losses of Genoa 03 experimental Stirling engine, which has an output power of 3 kW. Although the model response follows the same trends as the experiments, those simplifications provide errors which become more significant as the engine speed increases.

Abstract

Nowadays, building-integrated solar systems (i.e. photovoltaic modules installed directly in the façades) and concentrating solar systems are more popular. This paper defines the possibility of using Fresnel lens to improve the efficiency of building integrated photovoltaic modules. Both dynamic simulations (done using TRNSYS software) and experimental results (conducted on dedicated set-up with linear Fresnel lens) were described. It can be concluded, that Fresnel lenses allow improving the overall efficiency of the building integrated photovoltaic systems – during conducted tests, the performance of the tested photovoltaic module increased by about 7%.

Abstract

Nowadays, resilience is a necessary component for a sustainable development of cities. Achieving increased resilience requires improved risk assessment and modeling, better planning and design, increased communication and collaboration. The aim of this study is to propose a flexible methodology in order to analyse the energy sustainability and the risks of the metropolitan cities, in this case the method has been applied to the City of Turin. The main objectives are to evaluate the characteristics of the existing energy systems, their impact on sustainability and to understand how to satisfy the high-energy demand in a critical urban environment with few available renewable energy sources. This work describes a methodology to identifying energy risks, vulnerabilities and resilience for residential and tertiary buildings in Turin. Three indicators to evaluate the energy resilience and security assessment were used. In particular, the assessment of impact of individual indicators was conducted by using the aggregation and weighting method. To improve energy resilience, two future scenarios were assumed: the expansion of the existing district heating and the exploitation of roof-integrated solar-thermal collectors. The first results on historical trend show that the annual thermal energy consumption depends on climate data but also on per capita earning, with an annual decrease of 3% after 2007. A similar trend can be observed in natural gas consumption, in fact every year, natural gas decreases by 3%, while the district heating network increases by 8%. The results of future scenarios show an improvement of energy resilience, with a reduction of greenhouse gas emissions up to 12% with district heating expansion and 39% with also the use of solar collectors.

Abstract

Freshwater resources are very limited and because of the power plants, the water consumption in industry is even more than municipal. The cooling systems is a very important part of water consumption and in the past studies, it has been neglected.
The analysis of cooling systems shows that, evaporative air conditioners will consume high rate of water directly and that for a house with area of 140 m² is about 40 m³/month, that is about 10% of the total annual water use in typical households in an arid climate. The high power usage in compression air conditioner will also consume high water withdrawal indirectly and up to 102 m³/month in once-through cooling system. The results of the research show that the evaporated water in evaporative air conditioners is from the municipal network and since it is being evaporated, the impact is much higher than the urban water consumption that can be collected by wastewater systems. Therefore, it is necessary to improve the previous methods to achieve the goals of sustainable development.

Abstract

This special issue of JSDEWES brings together the selected papers presented at the 24th symposium Interklima 2017, held in Zagreb in April 6th, 2017. The organizers were the Faculty of Mechanical engineering and Naval Architecture, University of Zagreb, Croatia; SDEWES Centre, Zagreb, Croatia and Faculty of Energy Technology, University of Maribor, Slovenia. Held since 1969, Interklima is the oldest symposium on heating, refrigeration and air conditioning in this part of Europe. During the past decades Interklima has grown into an international venue for meetings of scientists and experts in the field. Interklima 2017 brought many new and actual topics such are:

• district heating/cooling
• energy from waste biomass
• geothermal energy
• nearly zero energy buildings
• smart meters/cities
• process engineering energy audits of large enterprises

The symposium was divided in two sections - Fran Bosnjakovic Day and District heating systems. The papers published in this special issue were carefully selected among the presented papers at section "Fran Bosnjakovic Day" and thoroughly revised before they were accepted for publication.

Abstract

The aim of the research is to outline the possibilities of utilizing waste heat in small municipal wastewater treatment plants. The facility, which was chosen as case-study, accepts about 2,300 m³ of raw sewage daily. In wintertime the wastewater temperature decreases to 10-14 °C which results in lower nitrification capacity based on measurement and validated model results. The excess heat of the wastewater would serve to increase the temperature of the aeration tank in order to enhance the microbiological activity and thus the efficiency of pollutant removal. The amount of reusable waste heat is calculated and with the help of dynamic simulation the effluent quality was determined to compare it with the original results. Increasing the temperature by 6 °C in the aerated tank, ammonium removal could be improved by 61%. This way not only the heat, but the nutrient pollution could be mitigated, too.

Abstract

The overall energy conversion efficiency of the waste-to-energy technologies is strongly affected by the distance of the biomass supply and the rate available during the year. Therefore, a simulation tool for the evaluation of the main outputs of a power plant for the wastes exploitation is a useful instrument for investigating the best trade-off between the plant size and the biomass supply. Nevertheless, it usually involves a large number of data and an extensive training and expertise. This paper focuses on the development of a numerical tool for the comparison of different waste-to-energy technologies and thus supporting the selection of the best exploitation strategy based on the data usually accessible to administrations. The numerical approach employs validated numerical models for the considered biomass exploitation technologies and its capabilities are demonstrated by simulating a reference case: the energy recovery from manure of different livestock farms in the province of Modena (Italy). The electric and thermal power production from the manure available in the considered territory is estimated and the produced electric energy is balanced with the energy requirements of the local animal farms. The remaining amount of wastes that has to be disposed is also calculated and compared with the initial input to the systems. Finally, different strategies for distributed and centralized exploitation of the manure are investigated and the related plant size and production of electric and thermal energy are evaluated. The proposed approach and the developed numerical tool prove to be useful instruments for decision makers and can help the efficient exploitation of the biomasses available in a region.

Abstract

In 2015, 1.2 billion people, or 16% of the global population, did not have access to electricity. Simultaneously, solid waste generation reached 200 million tons annually, and is projected to exceed 11 million tons per day by 2100. Solutions must hence be found, with Waste-to-Energy conversion a strong but controversial and costly contender. By use of cluster sampling, a sample of 361 individuals was obtained, from which a confirmatory factor analysis and structural equation model was undertaken using LISREL 9.1. All causal factors in the model were shown to have a positive influence on the creation of shared value of the Waste-to-Energy Power Plant and the local community, with 68% of the variance of the factor affecting the creation of shared value. Ranked in importance, the variables were government policy, the Waste-to-Energy operators and community participation, with a total score of 0.83, 0.37 and 0.36, respectively.

Abstract

Decentralized energy is growing in importance with time. The electricity being needed even in the most remote places, far from power stations, increases the importance of small power production devices such as micro-hydro devices like turbines. In this research, the velocity field in a meandering channel is studied in its natural conditions and with the introduction of spur-dikes, structures that prevent bank erosion, a natural phenomenon observed in meandering channels, with the use of computational fluid dynamics software. With the objective of improving the power production by investigating the changes of the flume velocities with the introduction of spur-dikes, one test without any spur-dike and three tests with it were conducted. Good results were reached, with velocities increasing between 10 to 20% with the introduction of these structures. In certain cases, the increase in power production can reach up to 85% than in a normal situation without spur-dikes in the river.

Abstract

The article is devoted to the use of unmanned aerial vehicle for geothermal waters exploitation monitoring. Development of a geothermal reservoir usually requires a system of wells, pipelines and pumping equipment and control of such a system is quite complicated. In this regard, use of unmanned aerial vehicle is relevant. Two test unmanned aerial vehicle based infrared surveys have been conducted at the Khankala field (Chechen Republic) with the Khankala geothermal plant operating at different regimes: during the first survey – with, and the second – without reinjection of used geothermal fluid. Unmanned aerial vehicle Geoscan 201 equipped with digital (Sony DSX-RX1) and thermal imaging (Thermoframe-MX-TTX) cameras was used. Besides different images of the geothermal plant obtained by the surveys, 13 thermal anomalies have been identified. Analysis of the shape and temperature facilitated determination of their different sources: fire, heating systems, etc., which was confirmed by a ground reconnaissance. Results of the study demonstrate a high potential of unmanned aerial vehicle based thermal imagery use for environmental and technological monitoring of geothermal fields under operation.

Abstract

Rural water coverage in Ghana is on the increase, yet there are real concerns about the level of service received and sustainability of water supply systems. One of the reasons is the lack of systematic maintenance because of inadequate funding and unreliable cash flow for Capital Maintenance Expenditure. This paper highlights the current gaps and needs of water management models in three districts using focus group discussion and key informant interviews to collect qualitative and quantitative data. The study revealed that the mechanism inherent in the National Community Water and Sanitation Strategy for addressing Capital Maintenance Expenditure works for systems that have been implementing it. Limited capacity and weak management characterize water systems with inadequate mechanism to address Capital Maintenance. Results showed limited awareness and application of water sector guidelines for the management of the piped systems by the management models and the districts. This paper contributes to the literature on funding mechanisms for small town systems sustainable water delivery in Ghana. The study concludes that to effectively address sustainable water delivery in small town systems, governance, operations and financial management regimes in line with the water sector guidelines are critical to bring about the necessary change in the management models. This calls for stronger supervisory and oversight responsibilities from Community Water and Sanitation Agency and the District Assemblies.

Abstract

In the challenge of achieving environmental sustainability, industrial production plants, as large contributors to the overall energy demand of a country, are prime candidates for applying energy efficiency measures. A modelling approach using cubes is used to decompose a production facility into manageable modules. All aspects of the facility are considered, classified into the building, energy system, production and logistics. This approach leads to specific challenges for building performance simulations since all parts of the facility are highly interconnected. To meet this challenge, models for the building, thermal zones, energy converters and energy grids are presented and the interfaces to the production and logistics equipment are illustrated. The advantages and limitations of the chosen approach are discussed. In an example implementation, the feasibility of the approach and models is shown. Different scenarios are simulated to highlight the models and the results are compared.

Abstract

In anaerobic digestion of microalgae, the intracellular material may remain intact due to the non-ruptured membrane and/or cell wall, reducing the methane yield. Therefore, different pretreatment methods were evaluated for the solubilization of microalgae Scenedesmus sp. The anaerobic digestion of biomass hydrolyzed at 150 °C for 60 min with sulfuric acid 0.1% v/v showed higher methane yield (204-316 mL methane/g volatile solids applied) compared to raw biomass (104-163 mL methane/g volatile solids applied). The replacement of sulfuric acid with carbonic acid (by bubbling carbon dioxide up to pH 2.0) provided results similar to those obtained with sulfuric acid, reaching solubilization of 41.6% of the biomass. This result shows that part of the flue gas (containing carbon dioxide and other acid gases as well as high temperatures) may be used for the hydrolysis of the residual biomass from microalgae, thus lowering operational costs (e.g., energy consumption and chemical input).

Abstract

Geothermal energy provides an opportunity for sustainable energy supply. Nevertheless, some local geothermal energy projects face public opposition. To understand public acceptance or rejection of technologies, appropriate methods need to be applied depending on the project phase. This is exemplified for geothermal energy, for which an exploratory, qualitative study was conducted which uncovered laypeoples’ mental models by assessing picture, word and colour associations on geothermal energy. Participants (N = 79) were asked for their associations on geothermal energy, as well as its general acceptance. The results revealed insights into cognitive conceptions as well as possible misconceptions. It could also be shown that participants’ evaluation of associations in terms of positive emotions correlated positively with geothermal energy acceptance. The study verifies that assessing mental models can be valuable in early phases of understanding public acceptance, as acceptance-relevant criteria and topics to be addressed can be identified in order to adequately respond to people’s concerns.

Abstract

This paper presents a study about an autonomous photovoltaic system making use of the novel Lithium Iron Phosphate as a battery pack for isolated rural houses. More particularly, this paper examines the behavior and efficiency of a low-cost isolated photovoltaic system for typical rural houses near Luena in Angola. The proposed system (solar panel, batteries, controller, and inverter) has been projected having in mind the required household daily load of 1,300 Wh and available solar irradiance. The initial batteries charging revealed to be essential to not only ensure a long battery life but using a balanced pack it was possible to achieve more stored energy. On-site, the polycrystalline solar panels used showed a daily average efficiency of 10.8%, with the total system having 75% efficiency. This result was adjusted to the average temperature in Angola. This way, it was made an extrapolation to the monthly irradiation values in Angola. The results achieved showed good energy production during almost all year except January and December, which revealed critical production values of 1,356 Wh and 1,311 Wh, respectively. These values are too close to the daily consumed energy and indicate the addition of a 2^nd alternative source of energy (wind generator, diesel generator, etc.) to be explored further.