Abstract

The purpose of this paper is to ascertain the reliability of a zero-dimensional approach, aimed to design a double rotor kinetic turbine prototype, by means of computational fluid dynamic analysis. The interaction between the flow and the blade of the turbine prototype external rotor is evaluated. The calculation is carried out by a three-dimensional analysis using the commercial code FLUENT 15.0. In the present work, the Reynolds Averaged Navier-Stokes approach is used, with the two-equation Realizable k-epsilon turbulence model. The blades profile is a NACA 4412 interacting with flow at an attack angle of 4°, which is kept constant along the blade height. The estimation of the forces acting on the blades allows a more accurate evaluation of the blade lift coefficient, which is useful to design the blades geometry and to compute the power coefficient, previously estimated by the traditional mono-dimensional approach.

 

 

Abstract

Climate change poses novel challenges for cities, threatening long-term sustainability objectives and necessitating investments in resilience. Climate change exacerbates the challenge of identifying the range of impacts of natural hazards in terms of scale and frequency. This study focuses on climate change adaptation responses with regard to flood management in the Metro Vancouver regional area, which is the last large non-amalgamated region in Canada. It is comprised of 24 local authorities and a regional government with delegated and distributed authority for flood management and other responsibilities. The area is subject to river flooding, intense rain storms and an increasing rate of sea level rise. The study identifies mechanisms by which the municipalities make sense of the existing hazards as well as how they design and invest into responses for future risks under conditions of uncertainty. Given the geographic, demographic and socio-economic differences across municipalities in the region, the study found a diverse set of responses in planning regimes in regard to the long-term risks as well as the short-term political pressures that municipalities face. This resulted in a significant variability of planning policies and practices across the region, which could potentially reduce overall regional ability to adapt to change. The paper concludes with a discussion of measures that can be taken to strengthen the regional coordination process.

 

Abstract

A large part of the thermal energy in buildings is lost through the drain and ends up as warm wastewater in the sewer system. The installation of heat exchangers in the sewer system enables a rise of the source temperature of heat pumps, increasing their coefficient of performance. To investigate the potential of such a technique in the Brussels Capital Region, a test facility named MYRTES has been installed in the sewer network, the starting point of this facility being to have one heat recovery system per residence. To estimate the heat recovery rate, potentially available in the Brussels Capital Region, the data from this test facility have been used as inputs and validation for a predictive model, considering both the heat recovery and its financial and environmental implications. Simulations show a minimum heating power of the heat pump of 6.3 kW, at a hot water temperature of 45 °C. A maximum of 35% of the buildings in the Brussels Capital Region are eligible for the use of such a system. At current tariffs, the levelized cost of energy for these systems, is lower than for traditional air heat pumps, but is higher than for gas boiler systems. The total equivalent warming impact, however, is estimated to be around 49% lower than for gas boiler systems and around 13% lower than for air heat pumps. In conclusion, heating through these types of systems is more expensive than gas boiler systems, but with increased consumption the competitiveness of these systems improves.

Abstract

In this research, a new model was developed and modified with a combined solar heating system which works with solar radiation and electricity. In order to model the system, the outdoor temperature of the location and solar irradiance has been considered. The case study of this research has been done in Porsgrunn City in the south of Norway. The building which was modelled in this research is a passive solar building which is able to store heat by using phase change materials, which are mounted on the floor and release the heat when the temperature of the house decreases. The model of the house was designed based on some assumptions about ambient temperature, solar collector size, transmitting lines length and some specific properties like air density and specific heat. The results of this research show that a solar heating system which is working with electricity can provide a sufficient temperature for the house in winter time. With using the phase change materials in order to have a passive solar building design, an improvement in the temperature inside the house was seen. Based on the simulation results which were achieved, a solar heating system which works with electricity can be an efficient system to heat the house, especially in the winter times.

Abstract

Bioenergy business operators can significantly contribute to the sustainability of bioenergy systems. While research has addressed the maturity of corporate responsibility for sustainability, the maturity levels of bioenergy business have not been determined. The objectives of this research were to characterise the maturity levels of bioenergy corporate responsibility for sustainability and outline an approach by which companies can operate at the most mature sustainability excellence level. Literature, three workshops attended by bioenergy experts and a case study on biobutanol production in Brazil were used to develop the maturity model and approach. The results characterise the profitability, acceptability, and sustainability orientation maturity levels through sustainability questions and methods, and list the components of a systemic, holistic approach. Although the shift of business mindset from sustainability-as-usual to sustainability excellence is challenging, a systemic approach is necessary to broadly identify sustainability questions and a multitude of methods by which they can be answered.

Abstract

Mango is one of the most popular and best paid tropical fruits in worldwide markets, its exportation is regulated within a phytosanitary quality control for killing the “fruit fly”. Thus, mangoes must be subject to hot-water treatment process that involves their immersion in hot water over a period of time. In this work, field measurements, analytical and simulation studies are developed on available hot-water treatment equipment called “Original” that only complies with United States phytosanitary protocols. These approaches are made to characterize the fluid-dynamic and thermal behaviours that occur during the mangoes’ hot-water treatment process. Then, analytical model and Computational fluid dynamics simulations are developed for designing new hot-water treatment equipment called “Hybrid” that simultaneously meets with both United States and Japan phytosanitary certifications. Comparisons of analytical results with data field measurements demonstrate that “Hybrid” equipment offers a better fluid-dynamic and thermal performance than “Original” ones.

Abstract

Abstract

Urban mobility is highly dependent on private vehicles causing pollution, traffic congestion and traffic accidents. The tram has become one of the most relevant public transport modes in those cities which need to reduce the private vehicle dependency. However, the implementation of this kind of infrastructure must be done carefully to avoid unsuccessful route designs which make the system unfeasible to operate. With the aim of analysing the impact that a tram can cause in a city, an original methodology has been developed, which takes into account the effect of the new transport system implementation on three subimpacts: traffic, public bus and outskirts neighbourhoods. This methodology uses different data sources from urban traffic, environmental and energy systems. The methodology has been applied to the city of Zaragoza (Spain) with a current population of around 700,000 inhabitants. The main results found were that tram line 1 saves 6% of the annual final energy consumption of urban mobility, urban traffic has decreased by 7.7% in the city as a whole and by 39.7% for streets close to the tramway.

Abstract

This study focuses on the uncompleted multi-storey residential buildings located in hot climates. This construction pattern is common in the case of incremental housing, where additional floors are added to the building as housing needs grow. Top roofs in these buildings are usually left without thermal insulation until the rest of upper floors are erected. This causes higher thermal discomfort in the top flats compared to the lower ones. Thus, the aim of this study is to investigate thermal effect of some proposed temporary measures that are intended to protect these roofs from unwanted heat gains until the rest of storeys are constructed. This has been carried out using thermal modelling to find out the effect of these measures on the amount of heat transfer through the roof in both summer and winter times. The analysis showed that it is possible to achieve competent thermal protection of the top roof compared to the layered thermal insulation using simple, cost-effective, and reversible measures. Among the examined measures, covering the roof with white foldable sheets and the use of pergolas have been found to be the most effective measures. In both cases, a reduction of 38% in conductive heat transfer through the top roof in summer was observed compared to the unprotected modelling case.

Abstract

Thermoeconomic diagnosis represents a promising technique for the detection of
common faults in refrigeration systems, which are responsible of degradation in their
energetic performance. Recently, the authors have carried out a sensitivity analysis of the
performance of this method to the thermodynamic conditions of inlet air and to the
geometry of the direct expansion coil, in case of degradation induced by evaporator
fouling. The analysis showed that the method is able to detect this fault, but sometimes its
quantitative assessments are not satisfactory. In order to understand more in-depth the
origin of such results and identify margins for refinement of the technique, this paper is
aimed at evaluating at what extent changes in the exergetic performance of faults-free
components may negatively influence the model capability to detect the fouled
evaporator and quantify the consequent additional exergy consumption. The results
suggest that the method is particularly sensitive to the cost of “induced malfunctions” on
the compressor and the condenser, especially when low coil depth or high relative
humidity of inlet air are considered.

Abstract

This paper demonstrates the correct application of discounted cash flow methodology for
evaluating and designing energy and chemical production plants. Such processes usually
correspond to capital intensive long-term projects. Simple economic criteria, like the
profit or production cost are insufficient for this type of decision making because they do
not take into account the time value of money and underestimate the profitabilities of the
evaluated plants. This paper shows that some of those criteria based on the discounted
cash flows establish suitable compromises between long-term cash flow generation and
profitability. As several alternative options are usually evaluated in parallel, it is shown
how to rank mutually exclusive alternatives properly and how to select the best option
from among them. Two large-scale case studies demonstrate that using discounted cash
flow methodology can result in substantially different decisions than non-discounted
criteria, however, these decisions are affected by several input parameters.

Abstract

Recently different studies of green transport have become interesting for policy makers,
car manufacturers, customers and energy suppliers. Many stakeholders from the public
and private sectors are investing a lot of effort to identify consumer behaviour for future
improvements in development of green products and effective strategies, which could
accelerate the transition to sustainable future. This paper presents the effects of electric
vehicle promotional policies and customer preferences about alternative fuel vehicles.
This study has shown that the electric vehicle promotional policies adopted in Slovenia
have been unsuccessful, as the share of first-time registered electric vehicles in 2013 was
below 1%. For different segments of people whose opinions about low emission vehicles
differ, different measures must be adopted. When designing promotional policies focus
must be on the most relevant factors such as the total vehicle price and fuel economy.

Abstract

The integration of absorption chillers in micro-cogeneration systems based on micro-gas turbines can be useful as an appropriate strategy to increase the total system energy efficiency. Since it is an area intensive in technology, it is necessary to develop and use models of simulation, which can predict the behavior of the whole system and of each component individually, at different operating conditions. This work is part of a research project in high efficiency cogeneration systems, whose purpose at this stage is to model a micro-cogeneration system, which is composed of a micro gas turbine, Capstone C30, a compact cross flow finned tube heat exchanger and an absorption chiller. The entire model is composed of specifically interconnected models, developed and validated for each component. The simulation of the microturbine used a thermodynamic analytic model, which contains a procedure used to obtain the micro turbine characteristic performance curves, which is closed with the thermodynamic Brayton cycle model. In the cogeneration system discussed in this paper, the compact heat exchanger was used to heat thermal oil, which drives an absorption chiller. It was designed, characterized and installed in a cogeneration system installed at the Centre d'Innovació Tecnològica en Revalorització Energètica i Refrigeració, Universtat Rovira i Virgili. Its design led to the heat exchanger model, which was coupled with the micro turbine model. Presented in this work is a comparison between the data from the model and the experiments, demonstrating good agreement between both results.

Abstract

Over the last decades, phytodepuration has been considered an efficient technology to treat wastewaters. The present study reports a bench scale depuration assay of swine wastewater using Lemna minor. The highest observed growth rate obtained in swine wastewater was 3.1 ± 0.3 g_DW m⁻² day⁻¹ and the highest nitrogen and phosphorus uptake were 140 mg N m⁻² day⁻¹ and 3.47 mg P m⁻² day⁻¹, respectively. The chemical oxygen demand removal efficiency in the swine wastewater assay was 58.9 ± 2.0%. Furthermore, the biomass valorisation by anaerobic co-digestion with swine wastewater was assessed. Results showed a clear improvement in specific methane production rate (around 40%) when compared to mono-substrate anaerobic digestion. The highest methane specific production, 131.0 ± 0.8 mL CH₄ g⁻¹ chemical oxygen demand, was obtained with a mixture containing 100 g of duckweed per liter of pre-treated swine wastewater. The water-nutrients-energy nexus approach showed to be promising for swine waste management.

Abstract

The planning of urban settlements requires a targeted approach towards more sustainable energy, water, and environment systems. This research work analyses the city of Uppsala and a district that is an urban renewal project at the site of former high voltage power lines, namely Östra Sala backe, which will have a new energy concept. The latter is analysed based on proposals for two phases that aim to reach a net-zero district target based on the quality of energy (exergy). An indicator set with five main categories is introduced based on per capita values to enable a comparable basis between the scales of the city and the district, including exergy per capita as a new indicator. The present status of Uppsala is further analysed based on Sankey diagrams to provide insight into the present urban metabolism of the city. The results indicate that the best practice values of Östra Sala backe based on phase two can achieve significant savings in per capita values, which include 5.5 MWh of energy usage, 6.1 MWh of exergy consumption, 33 m³ of water consumption, 22 kg of waste generation, and 4.2 tonnes of carbon dioxide (CO₂) emissions. Additional scenarios for Uppsala indicate that the district can be about 10 years ahead of the city’s existing performance.

Abstract

This study focuses on the adsorption and preconcentration of various metals by silica gel surfaces modified with aminopolycarboxylic acids namely ethylenediaminetetraacetic acid or diethylenetriamine-pentaacetic acid. The adsorption performance of the studied materials was determined in mixed metal solutions and the adsorption isotherm studies were conducted for cobalt, nickel, cadmium, and lead. The results were modeled using various theoretical isotherm equations, which suggested that two different adsorption sites were involved in metal removal although lead showed clearly different adsorption behavior attributed to its lowest hydration tendency. Efficient regeneration of the adsorbents and preconcentration of metals was conducted with nitric acid. Results indicated that the metals under study could be analyzed rather accurately after preconcentration from both pure, saline and ground water samples.

Abstract

In the paper, comparison of an analytical and a numerical model of silica gel/water adsorber/desorber is presented. Adsorber/desorber as a part of the two-bed single-stage adsorption heat pump is discussed. The adsorption heat pump under consideration consists of an evaporator, two adsorber/desorber columns and a condenser. Only heat and mass transfer was taken into account during operation of assumed adsorption heat pump. Adsorption equilibrium was described by the Dubinin-Astachov model. The presented mathematical models, both analytical and numerical, were created to describe the temperature, heat and concentration changes in the adsorber/desorber and consequently to describe the performance of the adsorption heat pump. Heat and mass transfer equations of the model were solved analytically and calculation parameters were entered in the common spreadsheet. The numerical model was established comprising of the set of heat and mass balance partial differential equations, together with the initial and boundary conditions and was solved by the numerical method of lines. The developed analytical model is very basic and can be used only for the initial estimates of mean cyclic temperature of the cooling/heating water in the adsorber/desorber bed. Validation of the numerical model shows reasonable agreement between the numerical and experimental averaged bed temperatures and is an indication of the proper mathematical modeling and the accuracy of the numerical analysis.

Abstract

The Moravian-Silesian Region is one of the most polluted sites by dust particles in the Czech Republic. Therefore, atmospheric concentrations of heavy metals as cadmium, cobalt, chromium, copper, nickel, lead, antimony, thallium, manganese, iron and zinc, were monitored at 10 localities in the region during summer of 2014. Heavy metals were monitored in 10 particle size classes from 18.3 nm to 9.93 μm. The percentage of the amount of heavy metals in the sum PM at all localities ranged from 0.2-2.5%. It was found that chromium, manganese, iron and zinc were mostly accumulated in dust particles with diameter greater than 1.6 μm. Lead, cadmium and antimony occur mainly in the class below 0.949 μm. These metals are more dangerous for human health, and can have potential carcinogenic effect. The influence of metallurgical industry evaluated on the basis of heavy metals in the individual particle size classes in the air within the Moravian-Silesian Region has not been unequivocally demonstrated.

Abstract

The temperature of the coolant is known to have significant influence on engine performance and emissions. Whereas existing literature describes the effects of coolant temperature in engines using fossil derived fuels, very few studies have investigated these effects when biofuel is used. In this study, Jatropha oil was blended separately with ethanol and butanol. It was found that the 80% jatropha oil + 20% butanol blend was the most suitable alternative, as its properties were closest to that of fossil diesel. The coolant temperature was varied between 50 °C and 95 °C. The combustion process enhanced for both diesel and biofuel blend, when the coolant temperature was increased. The carbon dioxide emissions for both diesel and biofuel blend were observed to increase with temperature. The carbon monoxide, oxygen and lambda values were observed to decrease with temperature. When the engine was operated using diesel, nitrogen oxides emissions correlated in an opposite manner to smoke opacity; however, nitrogen oxides emissions and smoke opacity correlated in an identical manner for biofuel blend. Brake specific fuel consumption was observed to decrease as the temperature was increased and was higher on average when the biofuel was used. The study concludes that both biofuel blend and fossil diesel produced identical correlations between coolant temperature and engine performance. The trends of nitrogen oxides and smoke emissions with cooling temperatures were not identical to fossil diesel when biofuel blend was used in the engine.

Abstract

Adiabatic compressed air energy storage systems offer large energy storage capacities and power outputs beyond 100 MWel. Salt production in Austria produces large caverns which are able to hold pressure up to 100 bar, thus providing low cost pressurized air storage reservoirs for adiabatic compressed air energy storage plants. In this paper the results of a feasibility study is presented, which was financed by the Austrian Research Promotion Agency, with the objective to determine the adiabatic compressed air energy storage potential of Austria’s salt caverns. The study contains designs of realisable plants with capacities between 10 and 50 MWel, applying a high temperature energy storage system currently developed at the Institute for Energy Systems and Thermodynamics in Vienna. It could be shown that the overall storage potential of Austria’s salt caverns exceeds a total of 4 GWhel in the year 2030 and, assuming an adequate performance of the heat exchanger, that a 10 MWel adiabatic compressed air energy storage plant in Upper Austria is currently feasible using state of the art thermal turbomachinery which is able to provide a compressor discharge temperature of 400 °C.