• Energy Research
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Abstract Hydrogen is considered a potential game changer for world energy systems and a solution to climate change concerns, as it generates zero waste and it is suited for power generation and transportation. Despite its several advantages, there are significant technical challenges in deploying a stable hydrogen economy including improving its process efficiencies, lowering production costs, maintaining cost-effective transmission and distribution, and exploiting inexpensive and sustainable feedstocks. In this context, a detailed study was conducted to analyze the production sources, technologies, storage and transport systems, and global potential exportable feedstocks to produce hydrogen. A comprehensive analysis of current hydrogen production technologies with their energy efficiencies and hydrogen selling prices was reported in this study. Various hydrogen production technologies with their capital investments and CO2 emissions were also presented. Potential feedstocks for hydrogen production were identified and analyzed through a product space model, which characterizes a network of global exportable products based on their similarities and productive knowledge. It was established that the hydrogen production feedstocks and sources currently used are primarily available in six countries: the United States of America, France, Russia, Sweden, the Netherlands, and Spain. Broadly, the results revealed that the United States of America and Russia shared the highest hydrogen feedstock exports, indicating a higher probability of hydrogen production in these countries. Except for Russia, all the studied countries fell in the most desired quadrant, indicating that they can move in all product space directions to exploit unexplored hydrogen feedstocks for better sustainable economic growth.

Abstract The South Korean government has been actively promoting an educational-facility improvement program as part of its energy-saving efforts. This research seeks to develop a decision support model for selecting the facility expected to be effective in generating energy savings and making the facility improvement program more effective. In this research, project characteristics and electric-energy consumption data for the year 2009 were collected from 6282 elementary schools located in seven metropolitan cities in South Korea. In this research, the following were carried out: (i) a group of educational facilities was established based on electric-energy consumption, using a decision tree; (ii) a number of similar projects were retrieved from the same group of facilities, using case-based reasoning; and (iii) the accuracy of prediction was improved, using the combination of genetic algorithms, the artificial neural network, and multiple regression analysis. The results of this research can be useful for the following purposes: (i) preliminary research on the systematic and continuous management of educational facilities’ electric-energy consumption; (ii) basic research on electric-energy consumption prediction based on the project characteristics; and (iii) practical research for selecting an optimum facility that can more effectively apply an educational-facility improvement program as a decision support model.

With gel treatment, application of low salinity waterflood recovers significant amount oil from mixed- or oil-wet and severely heterogeneous reservoirs due to wettability alteration. In order to assess the performance of hybrid gel treatment with low salinity waterflood, numerical simulations has been performed for various injection schemes including low salinity polymer flood and hybrid gel treatment with low salinity waterflood. While injectivity in polymer process is significantly reduced by injection of low salinity water, that of gel treatment process is not highly influenced. In addition, optimization algorithm maximizing net present value (NPV) is applied to injection scheme under consideration of injectivity to clarify the assessment of potential of hybrid gel treatment with low salinity waterflood comparing with low salinity polymer flood. Restricted constraint condition of injection makes hybrid gel treatment with low salinity waterflood to become efficient recovery method with respect to not on...

Abstract Due to the various restrictions on the energy performance of public office buildings, it is essential to obtain occupancy information for not only evaluating but also regulating the building energy performance. There is still a lack of information and standard, however, for occupancy density due to the limitations on data collection and the lack of reliable data. Therefore, this study aimed to determine the optimal occupancy density for reducing the energy consumption in public office buildings. Towards this end, this study used various statistical methods, such as correlation analysis, decision tree, and Mann-Whitney U test, based on the actual occupancy data from public office buildings in South Korea. This study was conducted in three steps: (i) establishment of the database; (ii) determination of the optimal occupancy density using the statistical approach; and (iii) application of the proposed occupancy density using building energy policies. As a result, it was shown that buildings with an occupancy density above 31.41 m2/person could save up to 50.3% energy on average compared to those with an occupancy density below 31.41 m2/person. The analysis results showed that the proposed occupancy density could help in deciding the appropriate occupancy density for reducing the energy consumption of public office buildings.

Abstract Waste heat recovery has attracted a significant attention because of the world growth in energy demand. In this paper, we report the study on an energy recovery system utilizing low-grade waste heat below 100 °C. This system called a thermal-driven electrochemical generator is composed of reverse electrodialysis (RED) power generation and thermal separation using waste heat. We especially focus on the experimental characterization of the RED process with ammonium bicarbonate (NH4HCO3) solution, which is known to be easily decomposed at the temperature around 60 °C. We characterized this NH4HCO3-RED system with various parameters including the concentration difference, the membrane type, the inlet flow rate, and the compartment thickness. We found the best power density at the concentrated solution of 1.5 mol L−1 and the diluted solution of 0.01 mol L−1. The maximum power density increases as the inlet flow rate increases or the compartment thickness decreases owing to the decrease in the internal resistance. We obtained the excellent power density of 0.77 W m−2, compared with the previous studies.

This study investigates the performance of the “green refurbishment” of existing buildings. Two ordinary rooms in an existing building were chosen for examination. Refurbishment measures such as additional insulation, high-performance glazing, and air-tightening were applied to the control room. Temperature and electricity use were monitored to identify heating performance in winter and then compared with a baseline. The results of the field tests showed that green refurbishment significantly improved heating performance. Lowered heating load and electricity use with increased airtightness were also verified through building performance simulations. The empirical investigation suggests a predictive model to obtain indoor minimum temperatures as a function of outdoor temperature swings.

AbstractRepublic of Korea is the seventh largest CO2 emission country in 2010 and the third fastest country in the growth of CO2 emission according to the European Commission's Joint Research Center. To mitigate the effect of CO2 on the climate change and global warming, Korea should reduce the anthropogenic CO2 emissions from sources such as the power plants and iron works. So carbon dioxide capture and storage (CCS) technology is regarded as one of the most promising reduction options. This study established the CO2 transport strategies from the sources to sinks (such as the saline aquifers and gas fields in the Southeast Sea of the Korean Peninsula) for the offshore CCS in Korea. Also the cost estimations were carried out with the CO2 transport strategies. The CO2 transport methods suggested in this study were pipelines for both onshore and offshore, and a complex concept consisting of a pipeline for the source to coast (including the liquefaction facility on a barge) and a CO2 carrier for the coast to sink (including the temporary storage near offshore sink). With respect to the onshore pipelines, it was desirable to construct the CO2 transport pipelines along existing roads and/or LNG (liquefied natural gas) pipelines, as already realized in the United Kingdom (UK) and the Australia CO2 transport chains because of the cost and environmental aspects. The CO2 carrier was considered for the offshore CCS demonstration stage starting in 2016 to meet the timeline set by the Korea National CCS Master Plan. To optimize the CO2 transport systems, the advantages and drawbacks for the CO2 transport using the pipeline and shipping were analysed and the costs for them were also estimated with the CO2 transport strategies. There were several factors to be considered before constructing the CO2 pipelines including the amount of CO2, the terrain, the diameter of pipe, the transport pressure, the CO2 quality, the transport temperature, the CO2 state (i.e. gas, liquid or supercritical phases), etc. Also for the CO2 shipping it should be considered such as the amount of CO2, the shape and capacity of CO2 cargo tanks, the ship capacity, the liquefaction pressure and temperature, the type of the temporary storage, etc. Although the present study is now on-going to optimize the CO2 transport infrastructure for the offshore CCS in Korea, the preliminary results show the CO2 transport cost for the pipeline system is lower than that for the shipping in the present status.

The earth provides a vast resource of groundwater from aquifers a few meters beneath the surface. Thus, buildings that use underground space must be equipped with dewatering wells to drain the permeated groundwater to the sewage pipelines to ensure the structural stability of the building. Although the inflowing groundwater temperatures and flow rates are stable enough for groundwater to be used as an energy source, 79% of the permeated groundwater is discarded through the sewers, generating significant sewerage expenses. This study introduced a novel heat exchanger module to utilize the permeated groundwater as an unused energy source using heat pumps, and the performance of the system was evaluated by TRNSYS simulations. First, the sizing of the unit heat exchanger module was proposed according to the mean inflow rate of the permeated groundwater. Second, the heat pump system was configured using multiple modules in the source-side loop. Finally, the performance of the proposed heat pump system was compared with that of a conventional air source heat pump using realistic load and temperature profiles. This preliminary study demonstrated interesting performance results, with a coefficient of performance for heating that was higher than that of a conventional heat pump system by 0.79. The results show the potential utilization of the systems for a construction project requiring large-scale underground spaces, where abundant groundwater is available.