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Emission reduction in buildings is essential to combat climate change. However, current strategies failed to balance development and emissions reduction goals. This paper selects a public building in China and simulates its initial energy consumption and carbon emissions. Then it establishes a multi-objective optimization model to explore cost-effective and emission-reduction strategies, considering photovoltaic and ground-source-heat-pump (GSHP) systems. Finally, NSGA-Ⅱ is used to solve, and sensitivity analysis is carried out. Results show that: (1) Energy consumed by the air conditioning system is the largest in January for heating and in July for cooling, validating the accuracy of the energy simulation model. (2) Economic efficiency and emission reduction effect are better when photovoltaic and GSHP systems are implemented simultaneously. (3) Electricity price, initial investment cost, annual solar peak hours, and the proportion of shallow geothermal energy significantly impact carbon emissions and cost. (4) The photovoltaic and power grid substitution ratio will exceed 8% every five years, and all substitutions will be completed in 2050. After adopting the GSHP system, the complete replacement will be advanced to 2045. Setting subsidies significantly shortens the payback period of investment and ensures firms' economic benefits. In summary, using photovoltaic and shallow geothermal energy is conducive to reducing emissions and saving costs in the long term. [ABSTRACT FROM AUTHOR]

China has been the world's largest producer and consumer of air conditioners, and more and more RACs 1 1 The RACs is short for room air conditioners. would be owned by China's households along with the rapid economic development. Air Conditioner is also considered as one of the largest potential contributors to energy reduction among home appliances because of the huge energy consumption. Therefore, the national energy efficiency standards were issued to promote the use and production of high-efficient RACs. According to China's energy efficiency standards, this paper investigated the electricity savings and CO 2 emission reductions from RACs over the period of 2005–2025. The results indicate that the rural RAC market which develops more slowly than the urban one still has great potential, and government has to revise subsidy policies to make the standards more effective, especially for rural areas. In 2025, the total electricity consumption of RACs is projected to be 598–674 TW h, while the amount without energy efficiency standards is 753 TW h. From 2005 to 2025, the energy efficiency standards for RACs can save 1430–2540 TW h electricity and reduce 908.3–1610. 1 Mt CO 2 emissions in different scenarios. Finally, we suggest that the standards should be revised every 4 or 5 years with higher revision pace of 8% to 10% [ABSTRACT FROM AUTHOR]

• Cooling operation of the multi-energy system (SAAC and GSHP) was discussed, three different operation configurations and their best working condition in a NZEB was analyzed. • Real energy consumption of three working modes wad analyzed and discussed. A 4025 m2 office building was built in Beijing, China, in 2014 as a living laboratory and prototype to explore the technical energy systems of nearly zero energy buildings (NZEBs) in China. Not only the building itself but also the heating, ventilation and air conditioning (HVAC) systems were designed with flexibility to explore their performance. Solar-assisted air conditioning (SAAC) and ground source heat pump (GSHP) systems with different terminal units were designed as HVAC systems for either experimental, comparison, or measurement purposes. In this paper, the cooling operation of multienergy systems is discussed on the basis of actual measurement data. HVAC systems have three possible types of operation configuration types, namely, SAAC priority, GSHP only and multimode. Operation scenarios for these configurations are presented first, and the small-scale simulation was carried out to analyze the performance of SAAC priority and GSHP#1 only mode. It indicates that SAAC could save about 47% of energy than that of GSHP#1. Then, the actual operation performance in 2018 was analyzed by reference to the operation data. Through this study, it is found that 1) multienergy systems of SAAC and GSHP operated well in this NZEBs during the summer season; 2) a 10 RT absorption chiller can work well for an NZEB building of approximately 1000 m2 when outdoor enthalpy is low and the solar radiation is stronger than 400 W/m2 as a result of high building thermal performance and air tightness; 3) SAAC can save about 40 to 50% of energy compared to that of GSHP system when providing services for the same terminal system under the same outdoor weather conditions and 4) The GSHP system is a good complement to the SAAC system which works well in June, September and early July when outdoor enthalpy is low. This study indicates that a combination of GSHP and SAAC systems is highly promising for NZEBs in cold climate zones such as Beijing, where the solar radiation is sound. [ABSTRACT FROM AUTHOR]

A ceiling-sidewall composite air carrying energy radiant air-conditioning system (ACERS) is presented, and the heating performance of the ceiling-sidewall composite ACERS combined with air source heat pump is investigated by field experiment. The results show that the combined system can meet the heating requirement for office buildings in south-central China, and also have the energy-saving potential. Moreover, the indoor thermal environment under three different installation types, namely the ceiling, the sidewall, and the ceiling-sidewall composite type, is analyzed by using computational fluid dynamic (CFD) simulation. The comparisons of three types indicate that all of them can meet the temperature requirement, but the temperature is more uniform and higher in the composite ACERS. Meanwhile, the temperature gradient in the ceiling ACERS is smaller than that of the sidewall ACERS due to the further heat transfer caused by air penetration. Both the experimental and CFD simulated temperature distribution demonstrates that the shelter of furniture has an impact on the indoor thermal environment, and it should not be ignored in practical engineering. This research shows the feasibility of winter heating by using the ACERS in office buildings, and is helpful for HVAC engineers to design and apply different ACERS types and realize the integration of air conditioning in winter and summer in this area. [ABSTRACT FROM AUTHOR]