Abstract

This study investigates the transient response of a novel CO2 geothermal thermosyphon (GT) integrated with heat recovery ventilators (HRVs), used to reduce the heating load of buildings in northern regions. Particularly, the transient response of the GT-HRV test bench is presented in this paper, characterizing the integrated system response under various test conditions in terms of time constant (T), heat transfer rate, and average evaporator temperature (Tev). Key experimental parameters include the GT filling ratio, coolant temperature, and coolant flow rate. The results indicate that a distinct T can be associated with each location of GT in fixed experimental conditions ranging from 417 seconds to 3762 seconds for coolant flow rate and inlet temperature set points of 0.05, 0.1, 0.15 and 0.2 l/s, and -9, -5 and -1 C.

Abstract

Using a static bifaciality to simulate the dynamic output power of bifacial photovoltaic (bPV) modules would produce errors. To address the problem, the present study proposed a novel parallel equivalent circuit model based on the single diode model, incorporating the structural characteristics and electrical properties of bPV modules. The results showed that the difference between the novel model and the traditional model increased as irradiance decreasing. When the incident solar irradiance on the module was 100 W/m², the output power simulated by the novel model is 3.3% lower than that of the traditional model and is more aligned with actual conditions. Further analysis showed that the difference between the two models increased with module temperature, though temperature changes have less impact than solar irradiance changes. Additionally, there is a superimposed effect between module temperature and irradiance. When the module temperature is 60 °C and the irradiance is 100 W/m², which significantly differs from the standard test conditions (STC), the simulation results of the novel model are 4.3% lower than those of the traditional model.

Abstract

This paper investigates the electricity procurement plan problem for charging service providers. The problem presents two challenges from both the demand and supply sides. On the demand side, the historical charging demand data is unavailable during the planning stage. On the supply side, multiple procurement options, including the spot market, financial power purchase agreements, self-invested power generation and energy storage are available on the market, with different costs, validity duration, and available capacities. To address these challenges, we propose a charging demand model to estimate demand at charging stations and develop cost models for various electricity procurement options. An optimization-based method to manage the electricity procurement portfolio is proposed. This method aims to minimize the total procurement costs while ensuring a reliable supply to meet the forecasted demand. The proposed approach is intended to guide charging service providers’ participation in the electricity market.

Abstract

The coalbed methane (CBM) reservoirs in eastern Yunnan and western Guizhou have the characteristics of multiple seams superposed, which are commonly exploited by multilayer commingled methods. It is observed that there is crossflow within the reservoir during the development, which impacts the production. To accurately describe the fluid flow law of multilayer CBM co-production, according to the flow mechanism of CBM in composite reservoirs, establish a multilayer combined fluid flow model including crossflow. A numerical simulator based on a fully implicit finite difference solution was developed to analyze the effect of permeability ratio and interlayer pressure differences on production. The results indicate that the numerical simulation results of the established model have a high compliance rate with the fitting results of the field production data, which confirms the validity of the model production prediction in this paper; With the increase of permeability ratio and interlayer pressure difference, the phenomenon of interlayer interference is intensified, the single well production is low, and the degree of reservoir utilization is poor. Differences in the above major influencing factors have resulted in interlayer conflicts and disturbances during combined production. Therefore, the development of CBM reservoirs should select homogeneous multiple coal seams under the same pressure system for co-production as far as possible. The research results provide a theoretical basis for the rational and efficient development of the CBM reservoir, realize quantitative evaluation of multilayered parameters, and have a certain guiding significance for CBM co-production of the reservoir.

Abstract

Proper resilience metrics (RMs) for energy systems are necessary to be identified, evaluated, and implemented to improve the energy system resilience. The proposed framework is aimed to be implemented as a tool, in the form of an energy resilience matrix, for energy system evaluation. The application of the engineering and infrastructure part of the framework was demonstrated in evaluation of a sport activity area located in Sweden. The results show potential to improve the resilience by installing solar cells and increase battery storage capacity in the area, connect with neighbouring area and utilize vehicle to grid.

Abstract

Large amounts of offshore wind (OW) power are expected to be installed in the North Sea in the next decades with countries aiming for a total of 300 GW by 2050 as stated in the Ostend declaration. This scale-up will help achieve the decarbonization of the European energy system. However, it is unclear how the introduction of such large volumes of OW will impact the power system, the energy system and the profitability of the OW developments. This paper investigates these issues. A capacity expansion planning model of the European energy system is used to compare cases with limited OW investments, free investments and investments in OW fixed to the targets for 2040. It finds that large amounts of OW mainly reduce the installation of onshore wind, PV and nuclear while causing a total system cost increase across the horizon of about 1%. The offshore grid layout has little impact on the return on investment (ROI), with slightly higher ROIs for meshed offshore grids. Meeting the OW targets increase their ROI by forcing investments to be made at an earlier date, allowing production in periods with higher electricity prices.

Abstract

Integration of rooftop photovoltaics and electric vehicle as battery is a promising technology to deeply decarbonize Bali, Indonesia because of Bali’s high sun altitude angle. In this study, we used techno-economic analyses to evaluate the decarbonization potentials of rooftop PV system integrated with battery in EVs in year 2019 and 2030 for Bali when technology price is expected to decline. Adoption of only rooftop PV in 2019 brings cost benefits to only few regions in Bali owing to the high prices of PV system. In 2030, widescale adoption of rooftop PV in all Bali can bring 5%-38% of cost saving and 30%-43% CO2 emission reduction. Performance further increases by adopting widescale integration of EVs as battery for rooftop PV, resulting 8%-41% cost saving and 72%-96% CO2 reduction, indicating deep decarbonization is possible by enhanced uses of rooftop PVs integrated with EV as battery in Bali.

Abstract

The impact of CO2 emissions constraints on the optimum configuration of a hydrogen production system and the associated energy flows, material flows and cost was assessed; focusing on Japan as case of study. Two scenarios were considered: Base scenario, focusing on optimizing cost; and WEC+C scenario, focusing on optimizing simultaneously energy use, water use, CO2 emissions and cost. Results show that all natural gas available is used to produce hydrogen using SMR for CO2 intensities higher than 11 kg-CO2/kg-H2 in both scenarios. As CO2 intensity decreases, SMR is replaced with electrolysis using hydroelectricity. Levelized cost of hydrogen tends to increase as CO2 intensity decreases, reaching 9.51 USD/kg-H2 for a CO2 intensity of 0 kg-CO2/kg-H2 in both scenarios. CO2 intensity affects energy and material flows. Reducing CO2 intensity increases water use in the WEC+C scenario as SMR is replaced with electrolysis using hydroelectricity.

Abstract

The efficient use of energy and sustainable development is the eternal development theme of today’s era. Finned-tube heat exchangers are widely used in various systems, and the heat transfer efficiency and operating performance have an important impact on the energy consumption of the system. When finned-tube heat exchangers are running at low temperature, the phenomenon of surface frosting often occurs. The generation of frost layer will worsen the heat transfer performance, and defrosting also needs additional energy consumption, resulting in a waste of energy. This paper conducted an experimental study on the frosting characteristics of a finned-tube heat exchanger with variable fin spacing, built a test platform for the frosting performance of the finned tube heat exchanger, and analyzed the effects of air temperature, relative humidity and wind speed on the frosting characteristics of the finned-tube heat exchanger with variable fin spacing. The experimental results show that the increase of air temperature, relative humidity and wind speed will promote frost formation.

Abstract

Carnot battery is an emerging long-term energy storage technology with lower cost, larger capacity, and no geography restrictions, which is expected for large-scale applications, promoting renewable energy consumption. However, the Carnot battery contains a HP unit, a heat storage unit, and an Organic Rankine Cycle unit, involving amounts of thermodynamic parameters that are coupled to each other. The importance and influence of thermodynamic parameters on power-to-power efficiency are still unclear. Therefore, in this paper, the SHAP model is used to establish the analysis framework for the power-to-power efficiency of the Carnot battery. Firstly, heat pump evaporation temperature and Organic Rankine Cycle evaporation temperature are the two most important parameters. Their maximum importance is 0.80 and 0.58, respectively. Then, the most important thermodynamic parameter in different scenarios is analyzed. Finally, the influence rules of HP evaporation temperature and ORC evaporation temperature on power-to-power efficiency are studied. The results are of guiding significance for the parameter optimization and engineering application of the Carnot battery.