Thermodynamic analysis of a novel fossil-fuel–free energy storage system with a trans-critical carbon dioxide cycle and heat pump

This paper presents and analyzes a novel fossil-fuel–free trans-critical energy storage system that uses CO2 as the working fluid in a closed loop shuttled between two saline aquifers or caverns at different depths: one a low-pressure reservoir and the other a high-pressure reservoir. Thermal energy storage and a heat pump are adopted to eliminate the need for external natural gas for heating the CO2 entering the energy recovery turbines. We carefully analyze the energy storage and recovery processes to reveal the actual efficiency of the system. We also highlight thermodynamic and sensitivity analyses of the performance of this fossil-fuel–free trans-critical energy storage system based on a steady-state mathematical method. It is found that the fossil-fuel–free trans-critical CO2 energy storage system has good comprehensive thermodynamic performance. The exergy efficiency, round-trip efficiency, and energy storage efficiency are 67.89%, 66%, and 58.41%, and the energy generated of per unit storage volume is 2.12 kW·h/m3, and the main contribution to exergy destruction is the turbine reheater, from which we can quantify how performance can be improved. Moreover, with a higher energy storage and recovery pressure and lower pressure in the low-pressure reservoir, this novel system shows promising performance

High-Fidelity Archeointensity Results for the Late Neolithic Period From Central China

Archeomagnetism focuses on exploring high-resolution variations of the geomagnetic field over hundreds to thousands of years. In this study, we carried out a comprehensive study of chronology, absolute and relative paleointensity on a late Neolithic site in central China. Ages of the samples are constrained to be ~3,500–3,000 BCE, a period when available paleointensity data are sparse. We present a total of 64 high-fidelity absolute paleointensities, demonstrating the field varied quickly from ~55 to ~90 ZAm2 between ~3,500–3,000 BCE. Our results record a new archeomagnetic jerk around 3,300 BCE, which is probably non-dipolar origin. The new results provide robust constraints on global geomagnetic models. We calculated a revised Chinese archeointensity reference curve for future application. The variations of absolute and relative paleointensity versus depth show good consistency, reinforcing the reliability of our results. This new attempt of combining absolute and relative paleointenstiy provides a useful tool for future archeomagnetic research

Magnification relations of quad lenses and applications on Einstein crosses

In this work, we mainly study the magnification relations of quad lens models for cusp, fold and cross configurations. By dividing and ray-tracing in different image regions, we numerically derive the positions and magnifications of the four images for a point source lying inside of the astroid caustic. Then, based on the magnifications, we calculate the signed cusp and fold relations for the singular isothermal elliptical lenses. The signed fold relation map has positive and negative regions, and the positive region is usually larger than the negative region as has been confirmed before. It can also explain that for many observed fold image pairs, the fluxes of the Fermat minimum images are apt to be larger than those of the saddle images. We define a new quantity cross relation which describes the magnification discrepancy between two minimum images and two saddle images. Distance ratio is also defined as the ratio of the distance of two saddle images to that of two minimum images. We calculate the cross relations and distance ratios for nine observed Einstein crosses. In theory, for most of the quad lens models, the cross relations decrease as the distance ratios increase. In observation, the cross relations of the nine samples do not agree with the quad lens models very well, nevertheless, the cross relations of the nine samples do not give obvious evidence for anomalous flux ratio as the cusp and fold types do. Then, we discuss several reasons for the disagreement, and expect good consistencies for more precise observations and better lens models in the future.Comment: 12 pages, 11 figures, accepted for publication in MNRA

Challenges and opportunities of low or zero carbon building: prospects of business models

Papers from the Designated Session TG66 - Energy and the Built EnvironmentCIB Publication 382: Selected papers presented at the CIB World Building Congres Construction and Society, Brisbane 5-9 May 2013There is an emerging consensus amongst governments, business sectors and civil societies regarding the urgent need to address the multiple challenges of climate change, environmental pollution, resource depletion and economic instability. The building and construction sector has been identified with the most opportunities for cost-effectively reducing carbon emissions. However, although business opportunities have been identified for low or zero carbon building (L/ZCB), L/ZCBs are generally perceived as more expensive and challenging than conventional buildings. Also, L/ZCBs are often addressed solely from their technological and environmental perspectives, while important economic and sociocultural aspects have been overlooked or examined implicitly. This paper aims to contribute to the knowledge of the challenges and opportunities of L/ZCB in a systems manner, and to explore how business models can help construction organisations address the former and maximise the latter. The research was carried out through the combination of a comprehensive literature review and case study with a large construction organisation which played a significant role in the UK and internationally. The examination of the challenges and opportunities employed the PESTEL analysis framework (Political, Economic, Sociocultural, Technological, Environmental and Legal). The case study included a desk study, observations, meetings and personal interviews with senior business and sustainability managers of the company. The results suggest the imperative role of business models for L/ZCB developments. Establishing and innovating business models were considered to present an opportunity for the company to sharpen their competitive edge in the market. A wide take-up of business models of L/ZCBs among construction firms was perceived to fit well the building industry's socio-technical system in addressing the multiple challenges.published_or_final_versio

A BIM-integrated fuzzy multi-criteria decision making model for selecting low-carbon building measures

Themes: Knowledge and Information Modeling - Special Session on BIM: no. O1.07published_or_final_versio