Heat Transfer and Bearing Characteristics of Energy Piles: Review

Energy piles, combined ground source heat pumps (GSHP) with the traditional pile foundation, have the advantages of high heat transfer efficiency, less space occupation and low cost. This paper summarizes the latest research on the heat transfer and bearing capacity of energy piles. It is found that S-shaped tubes have the largest heat transfer area and the best heat transfer efficiency; that energy piles need to be designed conservatively, such as adjusting the safety coefficient, number and spacing of the piles according to the additional temperature loads; and that unbalanced surface temperature has not been resolved, caused by uneven refrigeration/heating demand in one cycle. A composite energy pile applied to water-rich areas is proposed to overcome the decay of bearing and heat transfer performance. Besides, most of the heat transfer models are borehole-oriented and will fit for energy piles effectively if the models support variable ground temperature boundary conditions.

Capturing Multidimensional Energy Poverty in South America: A Comparative Study of Argentina, Brazil, Uruguay, and Paraguay

Roughly 789 million people have no access to energy, and around 2.8 billion people lack access to clean cooking solutions according to the World Bank, and so we also find many people that cannot afford energy (reliable and clean) at the current prices. In the literature, accessibility, availability, and affordability are underlined as the key drivers of energy poverty. In South America, these aspects have not been studied in depth. This research is relevant because it provides a standardized, cross-country, and comparable analysis of multidimensional energy poverty in the region. The study of energy poverty is critical for the development and well-being of countries, especially in regions such as South America, where this issue can be affected by geographical, cultural, infrastructure, and/or socio-economic differences. In this study, we measured the magnitude of energy poverty in Argentina, Brazil, Uruguay, and Paraguay. This methodology is based on the analysis of energy poverty through a multidimensional approach, considering three parameters as drivers of energy poverty in the countries: accessibility, availability, and affordability. Through a two-step process, first, we calculate the Weighted Average Energy Poverty Index (WAEPI), based on three proposed scenarios (W1, W2, and W3), and finally, through the Composite Energy Poverty Index (CEPI), we measure the existing gaps, based on the selected indicators, between the countries under study and the benchmark country. Additionally, we decided to focus our analysis on the country that has shown the highest level and gaps on multidimensional energy poverty in the region, as a case study to validate the results obtained through the chosen methodology. The results show that during the period of analysis (2000–2016), Paraguay has been the most energy-poor country among the countries under study, while Argentina has been the least energy-poor country. At the local level, we observed that, Paraguay, despite being one of the largest producers and exporters of clean hydroelectric energy in the region, still presents high levels of consumption of biomass or coal for cooking, while electricity only represents 17% of the total final energy consumption in the country (biomass and fossil fuels account for 83%). These results could lead the design of energy policies, projects, and programs to reduce the multidimensional energy poverty, nationally, also at the common platform: MERCOSUR. Finally, this study includes an analysis of policy implications and alternative solutions to eradicate energy poverty in the region.

Synthesis of Three-Dimensionally Interconnected Hexagonal Boron Nitride Networked Cu-Ni Composite

A three-dimensionally interconnected hexagonal boron nitride (3Di-hBN) networked Cu-Ni (3DihBN-Cu-Ni) composite was successfully synthesized in situ using a simple two-step process which involved the compaction of mixed Cu-Ni powders (70 wt.% Cu and 30 wt.% Ni) into a disc followed by metal-organic chemical vapor deposition (MOCVD) at 1000 oC. During MOCVD, the Cu-Ni alloy grains acted as a template for the growth of hexagonal boron nitride (hBN) while decaborane and ammonia were used as precursors for boron and nitrogen, respectively. Boron and nitrogen atoms diffused into the Cu-Ni solution during the MOCVD process and precipitated out along the Cu-Ni interfaces upon cooling, resulting in the formation of the 3Di hBN-Cu-Ni composite. Energy-dispersive spectroscopic analysis confirmed the presence of boron and nitrogen atoms at the interfaces of Cu-Ni alloy grains. Optical microscopy examination indicated that there was a minimum amount of bulk hBN at a certain compaction pressure (280 MPa) and sintering time (30 min). Scanning electron microscopy and transmission electron microscopy revealed that an interconnected network of hBN layers surrounding the Cu-Ni grains developed in the 3Di-hBN-Cu-Ni composite. This 3Di-hBN network is expected to enhance the mechanical, thermal, and chemical properties of the 3Di-hBN-Cu-Ni composite. Moreover, the foam-like 3Di-hBN extracted from 3Di-hBN-Cu-Ni composite could have further applications in the fields of biomedicine and energy storage.