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Distributed solar heating systems have high energy-saving potential as clean and energy-efficient production units in residential building applications. Solar energy resources are weak in hot summer and cold winter zone in China, which makes it difficult to completely rely on solar energy to heat residential buildings. A critical challenge is the lack of a theoretical basis for how to choose the solar-assisted heating system form. In this paper, seven solar-assisted heating systems are modeled and their performances are evaluated in six cities by using TRNSYS software. In terms of performance indicators, the solar fraction, the season performance factor, and the heat efficiency are used to thoroughly discuss the viability of using solar heating technologies in this zone. Based on the results, the average indoor air temperature was maintained between 16 °C and 20 °C, and the lowest solar fraction obtained was 10.1%. The carbon emission reduction in each city ranged from 60 kg to 400 kg, yielding good environmental benefits. According to the comprehensive comparison of the six evaluation indexes considered, the parallel or dual-source solar-assisted air source heat pump system can be used in a zone with medium solar energy resources. It is more suitable to use a dual-source solar-assisted air-source heat pump system in a zone with poor solar energy resources. The findings of this work can guide and promote the widespread application of distributed solar heating in household residential buildings in the hot summer and cold winter zone in China. [Display omitted] • The application status of solar heating technology is investigated in HSCW zone. • TRNSYS simulation verifies the feasibility of 7 different solar-assisted systems. • Comprehensively evaluate the thermal performance of 7 systems in 6 cities. • Multi-dimensional investigations of which system is suitable in HSCW zone. [ABSTRACT FROM AUTHOR]

• Data-driven and comprehensive thermodynamic technology models are developed. • Multi-fidelity approaches are used to compare heat-generation solutions. • Centralised CHP systems appear to be the most profitable option at present. • Heat pumps can achieve a significant degree of heat decarbonisation (55–62%). • Thermodynamic models reduce uncertainty by 75% compared to black-box approaches. This paper presents a multi-scale framework for the design and comparison of centralised and distributed heat generation solutions. An extensive analysis of commercially available products on the UK market is conducted to gather information on the performance and cost of a range of gas-fired combined heat and power (CHP) systems, air-source heat pumps (ASHPs) and ground-source heat pumps (GSHPs). Data-driven models with associated uncertainty bounds are derived from the collected data, which capture cost and performance variations with scale (i.e. , size and rating) and operating conditions. In addition, a comprehensive thermoeconomic (thermodynamic and component-costing) heat pump model, validated against manufacturer data, is developed to capture design-related performance and cost variations, thus reducing technology-related model uncertainties. The novelty of this paper lies in the use of multi-fidelity approaches for the comparison of the economic and environmental potential of important heat-generation solutions: (i) centralised gas-fired CHP systems associated with district heating network; (ii) gas-fired CHP systems or GSHPs providing heat to differentiated energy communities; and (iii) small-scale micro-CHP systems, ASHPs or GSHPs, installed at the household level. The pathways are evaluated for the case of the Isle of Dogs district in London, UK. A centralised CHP system appears as the most profitable option, achieving annual savings of £13 M compared to the use of decentralised boilers and a levelised cost of heat equal to 31 £/MWh th. However, if the carbon intensity of the electrical grid continues to reduce at current rates, CHP systems will only provide minimal carbon savings compared to boilers (<6%), with heat pumps achieving significant heat decarbonisation (55–62%). Differentiating between high- and low-performance and cost heat pump designs shows that the former, although 25% more expensive, have significantly lower annualised costs (£4.9 M vs. £7.7 M) and 12% higher CO 2 -equivalent savings. The uncertainty propagation reveals that data-driven and detailed thermoeconomic models can reduce the uncertainty in the total annualised energy cost and emissions by more than 75% compared to simplified black-box approaches, while the economic comparison of centralised CHP systems and domestic heat pumps for various electricity and gas price scenarios provides guidance to support energy policy. [ABSTRACT FROM AUTHOR]

• Over the technologies' typical 20-year lifetime, most UK dwellings have a cost optimum low-carbon heating system using air source heat pumps. • Dwelling properties and spatiotemporal variabilities significantly change the optimum low-carbon technology from blue hydrogen boilers, direct electrical heating, and air source heat pumps, to ground source heat pumps. • Direct electrical heating is economically preferred over heat pumps in lower demand dwellings and with analysis over shorter timescales. • Incentives for low-carbon heating need to target adoption of efficient technologies to reduce the greater increase in network demands. An understanding of heating technologies from the consumers' perspective is critical to ensure low-carbon technologies are adopted for reducing their current associated emissions. Existing studies from the consumers' perspective do not compare and optimise the full range and combinations of potential heating systems. There is also little consideration of how spatiotemporal and dwelling variations combined alter the economic and environmental effectiveness of technologies. The novelty of this paper is the creation and use of a new comprehensive framework to capture the range of heating technologies and their viability for any specific dwelling's traits and climate from customers' perspective which is missing from current studies. The model optimises combinations of prime heaters, energy sources, ancillary solar technologies and sizes, thermal energy storage sizes and tariffs with hourly heating simulation across a year and compares their operation, capital, and lifetime costs alongside emissions to realise the true preferential heating systems for customers, which could be used by various stakeholders. Using the UK as a case study, the results show electrified heating is generally the optimum lifetime cost solution, mainly from air source heat pumps coupled with photovoltaics. However, direct electrical heating becomes more economically viable as dwelling demands reduce from smaller dwellings or warmer climates, as shorter durations of the ownership are considered, or with capital cost constraints from lower income households. Understanding this is of high importance, as without correctly targeted incentives, a larger uptake of direct electrical heating may occur, which will burden the electrical network and generation to a greater extent than more efficient heat pumps. [ABSTRACT FROM AUTHOR]

• Techno-economic analysis of low-carbon heat supply options for UK supermarkets. • RIHC, an ASHP, and a thermal storage tank with advanced control is recommended. • Best investments provide a 16-to-18-year payback without a carbon price. • The UK renewable heat incentive subsidy (for ASHP) generates 89% of the 'savings' • When a £100/tCO2e tax is considered, paybacks are reduced to a 9–11 years. Eliminating the use of natural gas for non-domestic heat supply is an imperative component of net-zero targets. Techno-economic analyses of competing options for low-carbon heat supply are essential for decision makers developing decarbonisation strategies. This paper investigates the impact various heat supply configurations can have in UK supermarkets by using heat recovery principles from refrigeration systems under different climatic conditions. The methodology builds upon a steady-state model that has been validated in previous studies. All refrigeration integrated heating and cooling (RIHC) systems employ CO 2 booster refrigeration to recover heat and provide space heating alongside various technologies such as thermal storage, air-source heat pumps (ASHPs) and direct electric heaters. Seven cases evaluating various technology combinations are analysed and compared against a conventional scenario in which the building is heated with a natural gas boiler. The specific combinations of technologies analysed here contrasts trade-offs and is a first in the literature. The capital costs of these projects are considered, giving insights into their business case. Results indicate that electric heaters are not cost-competitive in supermarkets. Meanwhile, RIHC and ASHP configurations are the most attractive option, and if a thermal storage tank system with advanced controls is included, the benefits increase even further. Best solutions have a 6.3% ROI, a payback time of 16 years while reducing energy demand by 62% and CO 2 emissions by 54%. Such investments will be difficult to justify unless policy steers decision makers through incentives or the business case changes by implementing internal carbon pricing. [ABSTRACT FROM AUTHOR]

• Solar assisted heat pump coupled to a seasonal storage allows heating production. • Seasonal storage of thermal energy is technical and economically feasible. • Seasonal storage is able to be implemented in middle latitude. • PVT panels performance increase with the inclusion of a seasonal storage tank. • Key sizing factors are solar field area, volume of storage and capacity of heat pump. A water-water solar-assisted heat pump (SAHP) is projected on an under construction academic building at the University of Zaragoza (Spain). It integrates a heat pump heating system with photovoltaic/thermal collectors and seasonal storage. Because of its innovative design, considerably higher performances than a conventional type air-source heat pump are expected. This paper shows the simulation of the system performed in TRNSYS, a graphically based software used to simulate the behavior of transient systems. In addition, starting from the current design of the energy system, different sensibility analysis are simulated in order to study alternative configurations of the heating system. The solar coverage of the current installation design is about 60% and the expected savings yield to a payback period of 15,4 years. Three alternative configurations are proposed in this work, reaching up to around 98% of solar coverage. The study results show the technical and economic feasibility of the heating installation based on a solar assisted heat pump with implementation of seasonal storage in an educational building located in a middle latitude. [ABSTRACT FROM AUTHOR]

• A novel bed-based air source heat pump (B-ASHP) system was proposed. • A prototype experimental B-ASHP system was established and tested. • The B-ASHP system can be operated at both nighttime and daytime modes. • Better thermal comfort and bed surface temperature distribution can be achieved. • A number of issues requiring further considerations were identified. Air source heat pumps (ASHPs) have been increasingly used for space heating due to their high energy efficiency and installation flexibility. On the other hand, in many rural areas in northern Chinese provinces, Kangs, a kind of traditional heating systems based on burning biofuels, are still being used for space heating in winter. Based on the pros and cons of both ASHPs and Kang-based heating systems, a novel bed-based ASHP (B-ASHP) system has been proposed to combine the advantages from both an ASHP and a Kang heating system. In this paper, a prototype experimental B-ASHP system was designed and established, and its dynamic and steady-state operating performances tested in four test cases. The test results from the four test cases demonstrated that the prototype experimental B-ASHP system can achieve quicker increases in indoor air temperatures and bed-surface temperatures than Kang-based heating systems. The use of experimental B-ASHP system can lead to a more uniformed vertical indoor air temperature gradient, thus a better occupants' thermal comfort, than the use of a conventional convection-based ASHP system. Furthermore, compared to using a Kang-based heating system, a more uniformed bed surface temperature may be obtained when using a B-ASHP system. Nonetheless, although currently the prototype experimental B-ASHP system can be satisfactorily operated, a number of issues related to the designs of a B-ASHP system such as choices of refrigerant, refrigerant tube layout optimizations, and the use of variable speed compressors for capacity control, should be carefully considered to further improve its operational safety and energy efficiency. [ABSTRACT FROM AUTHOR]