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Building heating solutions in China

A spatial system analysis

Time: Tue 2019-12-17 10.00

Location: Kollegiesalen, Brinellvägen 8, Stockholm (English)

Subject area: Energy Technology

Doctoral student: Chang Su , Tillämpad termodynamik och kylteknik

Opponent: Professor Brian Elmgaard, DTU MECHANICAL ENGINEERING

Supervisor: Associate Professor Hatef Madani Larijani, Tillämpad termodynamik och kylteknik; Professor Björn Palm, Energiteknik, Tillämpad termodynamik och kylteknik

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Modern, clean, accessible and affordable building space heating is key tofuture sustainable development in China. However, it is impossible to recommendidentical building space heating solutions for all spaces in such alarge country as China. The decision making for choosing the most feasiblebuilding space heating solution is associated with a number of local characteristic spatial parameters, and stakeholders are still suffering from insufficient understanding of at which locations and under what conditions to choose a certain technology. Therefore, the present thesis aims at llingthis research gap by four steps: first, review current space heating situationin China; second, develop a systematic evaluation method for proper choice on building heating solution in different geolocations of China; third,demonstrate the efficacy of proposed method by case studies; fourth, analysethe Chinese energy sector administration infrastructure and its influence on building heating solutions.

Step one is to understand the current status of building space heating in China, including what technologies currently prevail and where they are implemented, as well as their application scales. It is found that under existing energy structures, coal as the primary energy source is extensively consumed in space heating systems. Coal-based regional boilers and combined heat and power district heating is prevalent in North China. Distributed heating, such as reversible air-conditioners, is still dominating South China. During past decade, sustainable energy space heating is increasing rapidly under a series of national policy initiatives, and will continue to grow in the future.

Following the current status review, a systematic method featured by spatial analysis is developed to compare the various heating options and find the best alternative. The method contains three system boundary levels, which reflect the characters of space heating technology, heat source, heat sink as well as the primary energy system. In each system level, local spatial parameters are analyzed. A set of key performance indicators is selected to quantitatively compare the relative advantages and disadvantages of implementing one building space heating solution over another from techno-economic-environmental as well geographical perspectives.

Case studies are then carried out to demonstrate the application of the method. In case study one, two Chinese cities with different local spatial conditions are chosen. Ground source heat pumps and air source heat pumps are compared with status-quo space heating solutions, which are coal boilers and electric boilers. The results lie in three aspects. Technically, heat pumps are more efficient than boilers from a primary energy point of view. Economically, ground source heat pumps have to reach a satisfying seasonal coefficient of performance value of 3.7 for a competitive payback period against existing heating solutions. Environmentally, heat pumps have to reach a critical seasonal coefficient of performance value around 2.5 to guarantee their environmental advantages compared with directly burning coal for space heating as long as coal is the dominant source of energy to produce electricity. Such a threshold is fairly easy to reach considering the coefficient of performance of the heat pumps in the market.

Case study two investigates seawater heat pumps potential in four coastal cities from north to south China. From techno-economic perspective, in North China seawater heat pumps can save primary energy use upto 18% in space heating, and can have a discounted payback period as short as 4 years compared with coal boilers. In southern Chinese cities on the other hand, seawater heat pumps can save primary energy use upto 14% in space heating but the discounted payback period is often more than 10 years compared with status-quo system. Environmentally, in North China seawater heat pumps have to reach a critical seasonal coefficient of performance value around 2.4 to guarantee their potential in carbon emissions saving when compared with fossil fuel boilers. In South China, seawater heat pumps generally emit less greenhouse gases than competing technologies. Geographically speaking, northern coastal cities are more feasible for seawater heat pumps applications compared with southern cities, as many buildings in northern coastal cities are within a proper distance to the seawater for efficient utilization of seawater for space heating and cooling.

Energy administration structure and energy policies in China are anavilyzed in parallel with case studies, in order to understand how energy management in China is regulated and how effective such energy policies can be. It is shown that energy administrations in China have great influence on the implementation of energy technologies and many energy policies are quite effective in promoting renewable space heating technologies.

In conclusion, stakeholders are suggested to adopt the system method proposed in this thesis, to promote the best building heating solution based on local spatial characteristics. By using the method in case studies, it is concluded that for heat pumps, a number of prerequisites have to be fullled for a more successful application in China. Future emphasis should be placed on heat pumps efficiency improvements, operation management and cost reduction. Meanwhile, increasing the share of zero-carbon electricity in the energy system should be a long-term goal so that the environmental benefits of heat pumps can be more prominent.