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The concept and a new method for the shielded development of bottom gas hydrates have been proposed, the technological phases and constructive elements of their implementation have been substantiated. The research provides for the realization of the idea suggesting the simultaneous dissociation of the vast areas of a gas hydrate deposit, management of the targeted process of the penetration of methane recovered from gas hydrates into water space and its accumulation under the extensive gas-collecting shield wherefrom it is removed by bottom pipe transportation facilities. To do hydraulic fracturing, a well is drilled into the plane of the junction of the surface of a gas hydrate deposit and the rocks of a roof, the open system of fissures in the rocks of a roof is made through which produced gas is released to a gas-collecting blanket in a water.

Abstract In this study, the influence of real-world conditions on the performance of a selective catalytic reduction (SCR) system in a Euro-6 diesel passenger car was analysed. NOx emissions and exhaust gas temperatures were recorded before and after the SCR system during real-world driving tests. The results showed that engine-out NOx emissions were positively correlated with vehicle specific power (VSP). The average NOx reductions (deNOx) of the SCR were 82.8%, 91.7%, and 85.5% for SCR-inlet gas temperatures below, within, and above the thermal window of 220–340 °C, respectively. The 92% of the tailpipe NOx peaks appeared under high power (VSP ≥ 10 W kg−1) and an insufficient deNOx level. Urban driving and long downhill sections in rural conditions caused cooling down of the SCR-inlet gas to below 200 °C, where the deNOx efficiency decreased and became dependent on the exhaust mass flow rate. To estimate the NOx benefit and CO₂ penalty via electrical heating of the SCR-inlet exhaust gas, the vehicle, the real driving dynamics, and the heating were simulated in Passenger car and heavy-duty emission model (PHEM). The minimum threshold of 200 °C resulted in the best NOx/CO₂ trade-off, reducing on average 4.7 mg of NOx per gram of CO₂.

The incorporation of Energy Storage Systems (ESS) in an electrical power system is studied for the application of Energy Time Shift (ETS) or energy arbitrage, taking advantage of the turbinable energy discharged in hydroelectric plants. For this, three storage systems were selected: Lithium-Ion Batteries (LIB), Vanadium Redox Flow Battery (VRFB), and Hydrogen Storage Systems (H2SS). The spilled turbinable energy available at the Paute Integral hydropower complex in the Republic of Ecuador is taken as the case study. Based on real data from the operation of these plants, a distinctive element of the study, the performance of the selected energy storage systems was analyzed applying the Analytic Hierarchy of Process for decision-making, where technical, economic, and environmental criteria were considered. Electrical energy stored during the early morning seeks to displace the thermal generation during peak hours, close to the demand centers. The results show that all the storage systems analyzed satisfy the required demand, although VRFB is recommended for the ETS. From an economic point of view, LIB represents the best alternative. From a technical point of view, H2SS is slightly superior, while prioritizing environmental aspects, VRFB technology prevails. However, the selection of the best ESS alternative must be continually evaluated, due to permanent technological changes. It is concluded that ESS represent a viable alternative to improve the operational performance of hydroelectric plants, meet the variability of demand, improve the quality of the electrical energy delivered, and displace the pollution-generation plants. Ingeniería y Tecnología Digital

Abstract Exhaust aftertreatment systems are crucial to ensuring real-world NOx emission limits for motor vehicles. Operating conditions constrain the NOx reduction performance of aftertreatment devices. This study analysed real-world NOx emissions, tailpipe exhaust gas temperatures, and air-fuel ratios during cold start in a closed-loop urban route, followed by hot-start real driving emissions (RDE) tests. Five Euro-6b sport utility vehicles (SUV) were tested: two gasoline vehicles with three-way catalyst (TWC), namely, one gasoline direct injection (G-DI) and one hybrid electric vehicle (HEV); three diesel vehicles with different NOx control systems, namely, only exhaust gas recirculation (EGR), lean-burn NOx trap (LNT), and selective catalytic reduction (SCR). The only-EGR- and LNT-equipped diesel vehicles and the G-DI vehicle surpassed the NOx Euro 6 limits in all tested sections. For the same vehicles, the total RDE emission factors were 9.0, 7.4, and 5.0 times the Euro 6 limits, respectively. In contrast, the diesel vehicle with SCR had an RDE emission factor 1.0 times the limit, and the HEV exhibited very low emissions at approximately 2 mg NOx km−1. However, during the cold start phase (first 5 min), the emission levels of the SCR and HEV vehicles surpassed the Euro 6 limits by 2.7 and 1.1 times, respectively. Based on the measurements at the tailpipe, the results indicate that cold start, urban driving, and cooling conditions of aftertreatment devices can lead to a decrease in the NOx conversion efficiency of TWC and SCR systems. The air-fuel ratio was key for the NOx conversion in TWC aftertreatment. The large differences between G-DI and HEV vehicles were primarily attributed to the lean and rich operations of the G-DI and HEV engines, respectively. To comply with stringent future regulations, lean-burn engines would require diesel-like aftertreatment. SCR and hybrid vehicles would require a careful aftertreatment thermal management or heating to further exploit their potential for reducing emissions in urban areas.

Abstract Viable implementation of building energy-efficiency policies is inevitable to mitigate climate change, above all as buildings account for around 40% of the world's energy consumption. Although some 75% of all buildings in Europe are energy-inefficient, only 0.4–1.2% of the whole stock is renovated each year. The greatest challenge for the coming decades is to increase the rate, quality and effectiveness of building renovation. The overall goal of the present article is to illustrate the key role to be played by Life Cycle Thinking in sustainable development policies and its implementation in the design of optimal retrofit solutions. The main housing renovation policies implemented in Spain were submitted to analysis using the focus of Life Cycle Approaches. Representative case studies were selected based on the analysis of 3245 real renovation solutions funded by policy programmes in the period between 2010 and 2014. Current solutions were assessed and compared to other retrofit scenarios that a priori might seem more desirable when striving for energy-efficient buildings. Multi-criteria assessment results reveal that the current renovation strategies applied in Madrid and Seville are, by no means optimal solutions, while only a small additional cost could produce significant performance improvement in Bilbao. The Passivhaus standard that offers the greatest reduction of energy consumption in all three cities would appear, however, not to be the solution of choice for any of them. These findings demonstrate the need to integrate Life Cycle thinking into the building process to identify the most sustainable energy pathways.

Abstract The global development of the offshore renewable energy sector has been driven by extensive investment and research in the utilization of offshore renewable energies, mainly at the regional level. However, for mid to long-term marine energy development planning, a comprehensive assessment of the global potential for the exploitation of the main offshore resources is required. This work developed and implemented an innovative methodological approach to identify potential zones for wind and wave energy exploitation at the global level, using long-term data series with fine spatial and temporal resolution. The proposed methodology was based on a five-step approach comprised of: (i) a resource assessment, to identify the zones with favorable conditions for energy exploitation; (ii) a structural survivability assessment, to identify feasible areas which would likely ensure the integrity and durability of the wind and wave devices; (iii) a logistics assessment, to evaluate the possibility of carrying out installation, operations, and maintenance activities; (iv) an assessment of the distance to consumer centers, to estimate the feasibility of transmission to the main urban areas; and (v) an estimate of the extractable power of the identified potential zones. For wind power, the United Kingdom (with 1470 TWh/month using a 10-MW turbine) and the United States (1079 TWh/month) were the countries with the highest estimated energy output of the identified potential zones. For wave energy, Brazil and New Zealand presented good opportunities for the development of the wave energy industry, with an estimated extractable power of 372 TWh/month and 286 TWh/month, respectively. The unique preliminary global analysis presented in this work provides guidelines to assist in the development of wave and offshore wind industries, in addition to supporting the management of marine spaces. Moreover, the methodologies can be replicated for other marine activities.

This work is performed to investigate the effect of using different sun tracking mechanisms on the flat plate photovoltaic system performances and the main parameters affecting the amount of their electrical energy output as well as those affecting their gains compared to the traditional fixed photovoltaic systems. To this end, five configurations of sun tracking systems and two traditional fixed panels have been considered. The sun tracking systems effect on the PV system performances is improved by using the hourly data collected over 18 days for different seasonal sky conditions. The daily cumulative electrical energy produced by the different systems have been quantified separately for each sky state and the corresponding electrical gains have then been compared to those experienced with two traditional fixed photovoltaic systems. It is found that for a completely clear day, the highest obtained gains are those related to the two-axis sun tracker systems, which decrease gradually from the inclined to the vertical rotating axis when the same optimum slope is applied and from the seasonal to the yearly optimum slope if the same rotating axis is considered. On the other hand, for the partially clear days, the gain amounts are mainly dependant on the clearness index and on the seasonal variation of day length values. For a completely cloudy day, the results show that all considered systems produced closely the same electrical energy and the horizontal position of the photovoltaic panel presented the best performance.

Abstract Non-renewable technologies still play a significant role in the electricity generation mix of most countries. Thus, relevant up-to-date environmental data are needed to provide a good understanding of the environmental consequences of the fossil fuel electricity generation technologies. The focus of this work is to examine the fossil-based electricity generation technologies used in Ecuador, providing a compelling insight into the revision of existent international databases. The main combinations of fossil fuel and thermal generation technologies have been studied: fuel oil in steam power plants (FO-SP), fuel oil in internal combustion engine power plants (FO-ICE), natural gas in gas turbine power plants (NG-GT), and diesel in gas turbine power plants (D-GT). ISO standards and CML 2000 methodology were further considered to quantify the potential environmental impact associated with the systems. Results show that NG-GT has the lowest environmental burdens, while FO-SP represents the highest impacts in 5 of the 6 studied impact categories. It is remarkable that for the same type of fuel (fuel oil), the ICE power plants have a lower environmental impact than FO-SP plants. Finally, lights and shadows of fossil-based electricity are discussed to provide a general picture of the current debate concerning transition pathways.

AbstractWorldwide and likewise in Ecuador, the 1982–1983 and 1997–1998 El Niño Southern Oscillation (ENSO) events had devastating effects in the economic and human dimension. Thus, scientists and decision markers look for a deeper knowledge about ENSO and its phases El Niño (EN)/La Niña (LN). Recent research highlights the changing nature of ENSO under opposite conditions of the Pacific Decadal Oscillation (PDO), making the assessment of the ENSO–PDO relation in Ecuador urgent. This study explores the time‐frequency characteristics of rainfall in the coast of Ecuador from January to April (PC‐JA) and evaluates the influence of PDO in the relation of ENSO with PC‐JA. For this, wavelet analysis was used to asses this nonstationary problem, Five long‐term (1964–2014) ground stations were used. The main results indicate that during the warm PDO period 1980–2000, the high wavelet coherence (ca. 0.9) implies a strong coupling between ENSO and PC‐JA. For cold PDO periods, prior to 1980 and after 2005, such coupling weakens with coherence about 0.5. This might indicate that PDO influence the relation between ENSO and rainfall in the coast of Ecuador. This coupling, during warm PDO, enhances high rainfall when in phase with EN, and drought conditions in LN events. The weak coupling of ENSO‐PC‐JA during cold PDO produces high rainfall amounts in Niño Neutral conditions and droughts during Neutral and LN. To account for ENSO flavours variability, the wavelet coherence between PC‐JA and the two ENSO uncorrelated indices E and C from Takahashi et al. was studied. Interestingly, we show that PDO warm phase influences the relation of Eastern Pacific related E index with PC‐JA from 2 to 8 years periods, and that the orthogonal Central Pacific related C index is not affected. These results raise questions about the validity of ENSO indices for contrasting PDO phases.