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Hybrid energy storage offers a new way to increase the renewable energy proportion (REP) of near-zero energy community energy system (NZECES). However, the optimization operation method of NZECES combining hybrid energy storage is not yet mature. Therefore, this paper proposes integrating electricity storage, heat storage and hydrogen storage into the NZECES, and conducting multi-time scale (MTS) operation optimization research. Firstly, a NZECES with electricity-heat-hydrogen storage is constructed. Secondly, a MTS optimization operation model of day-ahead scheduling, intra-day rolling, and real-time adjustment is established. Among them, the hourly scheduling scheme targeting the lowest daily operating cost is obtained through the optimization of the day-ahead stage. In the intra-day stage, the scheduling scheme with a time interval of 15 min is obtained by the rolling optimization. The operation scheme of electrical-related equipment with the minimum adjustment cost is obtained in the real-time stage. Finally, a NZEC with different building types is used as the energy supply object. The results show that compared to the traditional day-ahead scheduling scheme, the REP is increased by 3.6 % and the operation cost of the energy system is reduced by 5.3 % by using the MTS operation optimization method. • A near-zero energy community energy system with hybrid energy storage is constructed. • A multi-time scale operation scheme of day-ahead, intra-day, real-time is proposed. • The scheme can improve the renewable energy proportion and operation economy. [ABSTRACT FROM AUTHOR]

• HCHO oxidation by oxygen on FeN 3 -graphene surface was investigated using DFT method. • L-H mechanism plays a leading role in the oxidation of HCHO. • The HCHO oxidation reaction can be carried out spontaneously and irreversibly. • The desorption energy of the product was only 0.89 eV. • FeN 3 -graphene can be a potential and efficient catalyst for the oxidation of HCHO. Developing high activity and low cost catalyst for oxidative degradation of HCHO is critical for reduction HCHO pollution in indoor air. Herein, we proposed FeN 3 -graphene as a novel catalyst to oxidatively degrade HCHO into non-toxic H 2 O and CO 2. The DFT calculations were used to systematically study the reaction mechanism of HCHO oxidation by oxygen on the surface of FeN 3 -graphene. The L-H and E-R reaction mechanisms were adopted to guide the exploration of possible catalytic reaction pathways, and the change rules in equilibrium and rate of reaction at different reaction temperatures were obtained by thermodynamic and kinetic analysis. Five HCHO oxidative degradation paths were obtained, and the formaldehyde oxidation reaction can be carried out spontaneously and irreversibly within the temperature range of 300–800 K. At the same time, temperature showed a promoting effect on the reaction rate. The minimum activation energy is 0.95 eV, and the product needs only 0.89 eV to desorb from the catalyst surface, indicating that the catalyst has potential for practical application. Our theoretical prediction work can provide a new direction for the research and development of formaldehyde removal catalyst, and provide theoretical guidance for experimental research. [ABSTRACT FROM AUTHOR]

• Effect of passive heating renovation on energy poverty alleviation was verified. • Coal consumption and thermal comfort were measured and compared respectively. • Air tightness, thermal defect and indoor air quality were measured and evaluated. • Potential of the passive heating renovation was explored and further optimized. • Affiliated issues for alleviating energy poverty in policy, technology, etc. were discussed. Energy poverty refers to a situation that people cannot access and use energy safely. It is a major challenge for the global energy system because of its negative impacts on household income, health, education, gender equality and environmental conditions. To solve this problem, many countries advocate the development and promotion of passive solar technology, but the effectiveness of them for energy poverty mitigation has not been evidenced. Therefore, based on empirical studies in the rural areas of Qinghai-Tibet Plateau, this paper aims at investigating the effectiveness of passive solar heating renovation to alleviate energy poverty in rural plateau areas. Specifically, this paper compared and analyzed the coal consumption and indoor air quality during the heating period before and after the renovation of a single-storey building. Further, based on the IES-VE numerical simulation, this paper analyzed the impact of building envelope structure performance on indoor air temperature. The results show that after building renovation, the coal consumption during the heating period could be reduced by 97 kg/week, while the indoor average temperature of two bedrooms were increased by 4.8 °C and 1.7 °C respectively. Setting up the coal stove as an auxiliary heating device, can alleviate the defects of insufficient heating of passive solar energy technology, and indoor temperature could be further improved. However, indoor air quality was lowered because of the high PM 2.5 concentration. In contrast, improving envelope performance could further improve the average temperature of two bedrooms and the sunspace to 16.7 °C, 15.9 °C and 15.6 °C, meeting the requirements of indoor space heating. In general, passive solar heating could achieve satisfactory results, but to alleviate energy poverty effectively in rural plateau areas, further attention should be paid to other technical, economic, social and policy issues. [ABSTRACT FROM AUTHOR]

Abstract To relieve soil thermal accumulation and performance degradation over a long-time operation for ground source heat pump (GSHP) system in cooling-dominated area, a hybrid GSHP system with cooling tower (HGSHP) was proposed. The purpose of this paper is to study the performance and feasibility of HGSHP in Shanghai. Firstly, the simulation model of GSHP system for an office building was established by TRNSYS 17.0 and the reliability of simulation was validated by the measurement data. Then, one-year and ten-year variation of performance parameters of GSHP and HGSHP systems were calculated respectively and explored in depth. These results shown that, compared with GSHP system, the annual average electricity consumption of HGSHP system decreased by 6.40% and coefficient of performance (COP) increased by 7.12% during the first year of operation. Additionally, the outlet temperature of buried pipes was below 32 °C for HGSHP system during ten-year operation, while in GSHP system, the over-standard rate of outlet temperature of buried pipes could reach approximately 80% and soil temperature increased by 10.9 °C. These findings indicated that HGSHP system could provide a feasible solution for cooling and heating in hot summer and cold winter zones. Highlights • GSHP system for case building was evaluated by field measurement and simulation. • A cooling tower-assisted hybrid ground source heat pump system was proposed. • Performance parameters for these two systems for one and ten years were compared. • Feasibility and performance of this novel HGSHP system was confirmed. [ABSTRACT FROM AUTHOR]

Abstract The energy consumption in buildings accounts for a significant proportion of total energy and carbon emissions over the world. To reduce the building energy consumption and achieve sustainable development of buildings, nearly zero energy buildings (NZEBs) have attracted widespread attention as a future building energy target. This paper reviews energy-efficient measures (EEMs) and renewable energy technologies (RETs) in NZEBs and discusses the application and suitability of the key technologies, i.e. minimizing the energy demand in NZEBs by EEMs and adopting RETs to meet the remaining energy needs. EEMs contain efficient thermal insulation system, high-performance window system, good airtightness and fresh air heat recovery system. RETs are composed of solar photovoltaic/thermal (PV/T) system, air source heat pump system (ASHP), ground source heat pump system (GSHP), and wind power. In addition, this paper emphasizes further research works, which involve life cycle energy analysis (LCEA), meteorological parameters change, intelligent building operation management (IBOM) system, energy storage system and social policy issues. This paper will provide some references for the further development of NZEBs in different climatic regions in China. Highlights • This paper systematically reviews application of EEMs and RETs in NZEBs in China. • Feasibility and suitability of EEMs and RETs are evaluated from different aspects. • Further research work and development direction of NZEBs are pointed out. [ABSTRACT FROM AUTHOR]

Highlights • Solar-air energy heating system coupled with floor radiation system was presented. • We quantitatively evaluated the contribution of the solar house to energy poverty alleviation. • Energy consumption and indoor temperature were measured and compared. • We analysed the performance of the hybrid heating system in the solar house. Abstract Energy poverty is prominent in rural Qinghai-Tibet region, China. In sacrifice of thermal comfort and health, residents adaptively choose the biomass fuels and cheap coal for heating and cooking, as an approach to energy expenditure reduction. Considering renewable energy utilization is effective to replace the utilization of conventional fuel, this paper aims to examine the potential of using solar house for energy poverty alleviation. Based on a novel hybrid heating system, we renovated a rural building into a solar house in Wangtun village, Qinghai-Tibet region. The energy consumption and indoor air temperature of the building before and after reconstruction were field measured and comparatively analysed. Results indicate that the energy consumed by solar house with the hybrid heating system was 153.3 kWh/day lower than that by the old building. The average air temperature of the living room and two bedrooms in the solar house reached 12.8°C, 11.0°C and 10.2°C, about 8.78°C, 7.61°C and 6.82°C higher than temperatures of the rooms in the old building. Overall, the solar house has considerably improved indoor environments and provided people with better thermal comfort. It is concluded that solar house can be an effective approach to mitigate domestic energy poverty of the rural Qinghai-Tibet region. The findings may also instruct other rural regions in either China or other developing countries to address the issue of energy poverty. [ABSTRACT FROM AUTHOR]

Solar heating should be recommended strongly for domestic buildings in the Qinghai–Tibetan plateau due to the area's high intensity radiation. In this paper, a novel hybrid solar heating system is presented, that includes a solar kang system, a Trombe wall and a direct gain window. The effects of five combined solar heating operation modes on the indoor hourly temperature for one case domestic building located in the Qinghai–Tibetan plateau were investigated by field measurement and numerical simulation. The optimal operation mode for improving the indoor thermal environment was determined. Furthermore, the effectiveness of each operational mode on the east room was quantitatively evaluated and ranked. The results show that the numerical simulation and field experimental results were well agreed, although there were some differences in specific values. In addition, the results it indicated that a solar kang running all days and Trombe wall running daytime played a significant role in improving the indoor thermal temperature. These relevant findings could provide a reference for solar heating system design and indoor thermal comfort improvement for rural domestic buildings in the Qinghai–Tibetan plateau. [ABSTRACT FROM AUTHOR]

As a renewable energy technology, ground source heat pump (GSHP) system is high efficient for heating and cooling in office buildings. However, this technology has strong dependence on the meteorological and building envelope thermal characteristic parameters. For the purpose of quantitative investigation on the feasibility and performance GSHP, three cities located in cold climate zone, Qiqihaer, Shenyang and Beijing, were sampled. Firstly, the office building dynamic loadings in these cities were calculated on basis of the different meteorological and envelope thermal characteristic parameters. The TRNSYS, one kind of energy simulation software, were employed to simulate the operation performances of GSHP on basis of these parameters. The simulation revealed the data on the outlet/inlet temperature of buried pipes, soil temperature, energy consumption distribution and the coefficient of performance (COP) for one year operation. Furthermore, ten years operation was also simulated to show the stability of the performance based on the outlet/inlet temperature of buried pipes and soil temperature. From these results, the GSHP had shown its most suitable performance in Beijing, second in Shenyang and worst in Qiqihaer. These results could be used as a reference on suitable utilization of GSHP systems in office buildings located in cold climate zone, China. [ABSTRACT FROM AUTHOR]

Measurements of heat collection rate and heat loss coefficient are crucial for the evaluation of in service water-in-glass evacuated tube solar water heaters. However, conventional measurement requires expensive detection devices and undergoes a series of complicated procedures. To simplify the measurement and reduce the cost, software based on artificial neural networks for measuring heat collection rate and heat loss coefficient of water-in-glass evacuated tube solar water heaters was developed. Using multilayer feed-forward neural networks with back-propagation algorithm, we developed and tested our program on the basis of 915measuredsamples of water-in-glass evacuated tube solar water heaters. This artificial neural networks-based software program automatically obtained accurate heat collection rateand heat loss coefficient using simply "portable test instruments" acquired parameters, including tube length, number of tubes, tube center distance, heat water mass in tank, collector area, angle between tubes and ground and final temperature. Our results show that this software (on both personal computer and Android platforms) is efficient and convenient to predict the heat collection rate and heat loss coefficient due to it slow root mean square errors in prediction. The software now can be downloaded from . [ABSTRACT FROM AUTHOR]

Many countries have proposed plans on distributed energy systems. However, distributed energy systems still can be improved in system optimization design methods, new-type load, and application scenarios. Therefore, a novel distributed energy system is developed combining solar energy utilization with hybrid energy storage technology, i.e., heat storage and electricity storage. Secondly, with primary energy saving rate, carbon dioxide equivalent emission reduction rate, and annual cost per unit supply area as objectives, an integration optimization method considering equipment configuration and operation strategy is adopted. Then, considering different community types and scales, 12 nearly zero energy community scenarios with electric vehicles as a new-type load are designed. Comparative analysis is conducted on the proposed system, comparing with separated production system and in different scenarios. The results show the scenario with 50% public buildings possesses considerable energy saving (53.1%), environmentally protection (56.4%), and economy (50.1 CNY/m2). The proportion of public buildings mainly influences primary energy saving rate (21.0%), followed by annual cost per unit supply area 17.7 (CNY/m2), finally carbon emission reduction (9.1%). The residential community with 196800 m2 building scale perform brilliantly. These findings worth popularization and application in the developing nearly zero energy communities. • A novel distributed energy system is proposed considering hybrid energy storage. • The co-optimization method improves the primary energy saving rate by 24.0%. • Community with 50% public and 50% residential buildings has optimal energy saving and carbon reduction. • Community with 196800 m2 has marked CO 2 reduction (49.8%) and economy (56.5 CNY/m2). [ABSTRACT FROM AUTHOR]

To promote the application of renewable energy in low-energy buildings in Alpine regions, a solar-air source heat pump (SASHP) system was investigated based on a low-energy residential building in Xining City. First, a solar fresh air (SFA) heating system simulation model was established in TRNSYS software, and the reliability of the model was verified with measured values. In addition, based on the SFA heating system model, a SASHP system model was further realized. The operating characteristics of the SASHP system were explored in depth and compared with those of the single-ASHP system in the heating season. The results show that the SFA heating system model is reliable, with relative errors that can be controlled within 15%. The indoor average temperature (T ave) can be maintained from 16.13 to 19.61 °C. The SASHP system can leads to T ave fluctuations within the range of 21.4–22.9 °C, and the solar fraction can reach 55% in the heating season. Furthermore, the SASHP system can reduce energy consumption by 55.38% compared to the ASHP system; additionally, the COP of the SASHP system is 109.43% higher than that of the ASHP system, and the annual cost is 9.7% lower. Moreover, the SASHP system produces 55.48% less carbon emissions than the ASHP system. These results provide guidance for the application of SASHP systems in Alpine regions. [ABSTRACT FROM AUTHOR]

• Equipotential line method of relative cost was proposed. • The optimal energy station location with relative cost, about 89.22%, is determined intuitively. • Triple-generation system was combined with distributed variable-frequency speed pump heating system. • Economic analyses were carried out for the coupling system in terms of payback period. • Reliability of two strategies was compared for the coupling system. The district heating system with distributed variable-frequency speed pumps (DVFSP) can provide substantial energy savings. Moreover, the energy station location has a great impact on the capital expenditure of heating system. Therefore, to determine the optimal energy station location in DVFSP system, this paper initially built a theoretical model of a DVFSP district heating system based on a cost-oriented index. Subsequently, an equipotential line method was illustrated and applied to a case study. This novel method can intuitively present the district distribution of the relative cost (RC network) of DVFSP district heating system, which can conveniently determine the optimal location of an energy station. In the case study, six oval equipotential RC network lines were described. The maximum RC network reached 137.04% in the E4 location, and the minimum RC network was 89.22% in the E11 location. The results showed that the optimal energy station location was near the district load center and biased to the side with higher building loads. Finally, a new energy utilization mode that coupled a combined cooling, heating and power (CCHP) system and a DVFSP district heating system was proposed. Economic analyses were carried out for the coupled system based on the following electric load (FEL) strategy and the following thermal load (FTL) strategy. The results confirmed that, in terms of the payback period and partial load rate (PLR) of the prime mover, the FEL strategy was more suitable for the coupled system. These results can provide guidance for district heating system design and management. [ABSTRACT FROM AUTHOR]

With the rapid development of urbanization and the improvement of living standards of residents in China, the energy consumption and carbon emissions of the building sector is expected to increase in the near future. Nearly or net zero energy buildings have become a hot topic of research to reduce the fossil energy consumption and greenhouse gas emissions in the building sector. As the largest developing country and carbon emitter around the world, China has also made significant efforts on nearly zero energy buildings in recent decades. The central government has approved many demonstration projects on nearly zero energy buildings in different climate zones for more than ten years. This paper summarizes international definitions of zero-energy buildings, analyzes the latest definition and identifies the boundaries of nearly zero energy buildings in China. It provides an overview of the current situation, detailed policies and building codes of nearly zero energy buildings in China. Suggestions were given on the development and promotion of nearly zero energy buildings in China. These findings in this paper will help to guide the government to implement more efficient and effective policies and building codes of nearly zero-energy buildings in order to reduce carbon emissions in the building sector. • The definitions of ZEB are inconsistent. • Rapid development of ZEB in China is observed. • The current situation of zero energy building in China is presented. • The building codes and policies of ZEB from Chinese central and local governments are summarized. [ABSTRACT FROM AUTHOR]