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Research Papers: Heat Energy Generation/Storage/Transfer

A Theoretical Study on Decentralized Space Heating System

[+] Author and Article Information
Zhi-Ping Song

Beijing Key Laboratory of Energy Security and Clean Utilization, School of Energy Resources and Power Engineering, North China Electric Power University, Beijing, China 102206zpsong@public.bta.net.cn

J. Energy Resour. Technol 130(3), 032401 (Aug 08, 2008) (9 pages) doi:10.1115/1.2955479 History: Received January 02, 2005; Revised April 05, 2008; Published August 08, 2008

Global climate change mitigation requires the fossil fuel consumption substantially reduced. Space heating is an energy-consuming sector. Despite the fact that the thermal efficiency of current space heating systems has achieved a value higher than 85%, corresponding to lower than 40kg c.e./GJ, there is still a big potential for energy conservation. In order to realize the full potential, investigations of heating systems should appeal to reversibility/exergy analysis made on total energy concept basis. This paper starts with an introduction of the concept “reversible mode of heating,” leading the readers think of space heating in terms of reversibility. Right after, a systematic reversibility analysis on a “mine to home” basis is conducted to reveal the impact of any irreversibility of all subsystems or devices involved in the total energy system of heating on the fuel/monetary specific consumption of unit end-use heat. The paper points out that although combined heat and power (CHP) and electrically driven heat pump are both of “reversible mode,” the former is far more favorable in terms of energy conservation. The recently ascent decentralized energy system provides the best circumstances for CHP implementation. The demand-side improvement is a topic of most importance but frequently neglected. This study reveals that, if properly engineered, this improvement together with adopting a direct type of heat grid might lower the fuel specific consumption of end-use heat of CHP to a level as low as 139kg c.e./GJ.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Typical composition of a reversible mode of heating system. b—fuel energy delivery subsystem; W—power generation subsystem; WD—power transmission and distribution system; Q—heat generation subsystem; QD—heat transmission and distribution subsystem; US—user's subsystem (definition of letters, W, WΣ and EECR see Sec. 3).

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Figure 2

Dependence of the theoretically minimum fuel specific consumption of a heating system on demanded temperature level

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Figure 3

Dependence of fuel specific consumption of a CHP heating system on power plant efficiency

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Figure 4

Representative exergy index values versus heat generation subsystem outlet temperature tR0out

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Figure 5

Diagram of the heat transmission and distribution subsystem

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Figure 6

Energy conservation potential via quantitatively synchronic supply and via qualitative matching

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Figure 7

Exergy efficiency of the users’ subsystem

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Figure 8

Interrelationships between K, AU, W, ηUS, and inlet/outlet temperatures of heating medium

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Figure 9

The relative capital cost of fan-assisted radiator versus its relative heat transfer intensity

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