Exergy analysis of operation process of district heating systems

Abstract

The nature of the exergy consumption of district heating (DH) systems can not be explained clearly using the first law of thermodynamics. Exergy analysis method was used. A case study based on a DH system in Inner Mongolia, China, was carried out. The impact of operating parameters and design parameters on the energy quality of circulating water and exergy losses of DH systems during heat distribution was revealed. Results show that the energy quality of circulating water and exergy losses of DH systems during heat distribution could be reduced by decreasing the indoor temperature or increasing radiator areas. Compared with other factors, the outdoor temperature and indoor temperature have a greater impact on the energy quality of circulating water, exergy losses of circulating water, and total exergy losses during heat distribution. When the outdoor temperature varied by 10.00%, the average variation rates of such parameters were 85.12%, 90.02%, and 64.60%, respectively. When the outdoor temperature was 273.00 K and indoor temperature varied by 50.00%, the average variation rates of such parameters were 83.88%, 99.34% and 32.87%, respectively. It can be observed that the energy quality and exergy losses of DH systems can be reduced in the operation process.

Keywords

energy quality coefficient / exergy loss rate / design parameters / operating parameters / energy conservation measures

References

[1] LundH, WernerS, WiltshireR, SvendsenS, ThorsenJ E, HvelplundF, MathiesenB V. 4th generation district heating (4GDH) integrating smart thermal grids into future sustainable energy systems [J]. Energy, 2014, 68: 103-111

[2] ØstergaardP A, LundH. A renewable energy system in Frederikshavn using low-temperature geothermal energy for district heating [J]. Applied Energy, 2011, 88(2): 479-487

[3] ØstergaardP A, MathiesenB V, MöllerB, LundH. A renewable energy scenario for Aalborg Municipality based on low-temperature geothermal heat, wind power and biomass [J]. Energy, 2010, 35(12): 4892-4901

[4] HassineI B, EickerU. Impact of load structure variation and solar thermal energy integration on an existing district heating network [J]. Applied Thermal Engineering, 2013, 50(2): 1437-1446

[5] BolattürkA. Determination of optimum insulation thickness for building walls with respect to various fuels and climate zones in Turkey [J]. Applied Thermal Engineering, 2006, 26: 1301-1309

[6] ChwiedukD. Towards sustainable-energy buildings [J]. Applied Energy, 2011, 76(1-3): 211-217

[7] BakosG C. Insulation protection studies for energy saving in residential and tertiary sector [J]. Energy and Buildings, 2000, 31(3): 251-259

[8] Building Energy Research Center of Tsinghua University.2013 annual report on china building energy efficiency [M], 2013, Beijing, China Architecture & Building Press

[9] Building Energy Research Center of Tsinghua University.2014 annual report on china building energy efficiency [M], 2014, Beijing, China Architecture & Building Press

[10] ZmeureanuR, WuX Y. Energy and exergy performance of residential heating systems with separate mechanical ventilation [J]. Energy, 2007, 32(3): 187-195

[11] YildizA, GüngöA. Energy and exergy analyses of space heating in buildings [J]. Applied Energy, 2009, 86(10): 1939-1948

[12] GonçalvesP, GasparA R, SilvaM G. Comparative energy and exergy performance of heating options in buildings under different climatic conditions [J]. Energy and Buildings, 2013, 61: 288-297

[13] ÇomakliK, YükselB, Çomakli. Evaluation of energy and exergy losses in district heating network [J]. Applied Thermal Engineering, 2004, 24(7): 1009-1017

[14] RezaieB, RosenM A. District heating and cooling: Review of technology and potential enhancements [J]. Applied Energy, 2012, 93: 2-10

[15] LiT-l, ZhuJ-l, ZhangWei. Performance analysis and improvement of geothermal binary cycle power plant in oilfield [J]. Journal of Central South University, 2013, 20(2): 457-465

[16] JinN, ZhaoJ, ZhuNeng. Energy efficiency performance of multi-energy district heating and hot water supply system [J]. Journal of Central South University, 2012, 19(5): 1377-1382

[17] LiuJ-p, FuJ-q, FengR-h, ZhuG-hui. Effects of working parameters on gasoline engine exergy balance [J]. Journal of Central South University, 2013, 20(7): 1938-1946

[18] GongG-c, WeiZ, ChangS-j, HeJ, LiK-qing. Scheme-selection optimization of cooling and heating sources based on exergy analysis [J]. Applied Thermal Engineering, 2007, 27: 942-950

[19] OzgenerL, HepbasliA, DincerI. Energy and exergy analysis of geothermal district heating systems: An application [J]. Building and Environment, 2005, 40(10): 1309-1322

[20] OzgenerL, OzgenerO. Monitoring of energy exergy efficiencies and exergoeconomic parameters of geothermal district heating systems (GDHSs) [J]. Applied Energy, 2009, 86(9): 1704-1711

[21] RosaA D, ChristensenJ E. Low-energy district heating in energy-efficient building areas [J]. Energy, 2011, 36(12): 6890-6899

[22] ZhuM-shanExergy analysis of energy systems [M], 1988, Beijing, Tsinghua University Press

[23] DovjakM, ShukuyaM, OlesenW B, KrainerA. Analysis on exergy consumption patterns for space heating in Slovenian buildings [J]. Energy Policy, 2010, 38(6): 2998-3007

[24] LiH-w, SvendsenS. Energy and exergy analysis of low temperature district heating network [J]. Energy, 2012, 45(1): 237-246

[25] WangTengEnergy saving potential analysis of heating system based on energy quality [D], 2012, Beijing, Tsinghua University

[26] OzgenerL, HepbasliA, DincerI. Exergy analysis of two geothermal district heating systems for building applications [J]. Energy Conversion and Management, 2007, 48(4): 1185-1192

[27] KeçebasA. Performance and thermo-economic assessments of geothermal district heating system: A case study in Afyon, Turkey [J]. Renewable Energy, 2011, 36(1): 77-83

[28] HepbasliA. A comparative investigation of various greenhouse heating options using exergy analysis method [J]. Applied Energy, 2011, 88(12): 4411-4423

[29] CoskunC, OktayZ, DincerI. New energy and exergy parameters for geothermal district heating systems [J]. Applied Thermal Engineering, 2009, 29: 2235-2242

[30] China Academy of building research.design code for heating ventilation and air conditioning of civil buildings (GB50736-2012) [S], 2012, Beijing, China Architecture & Building Press

[31] LiD-yingHeating engineering [M], 2004, Beijing, China Architecture & Building Press

[32] WangS-c, ShenW-d, XuJ-f, LiYun. Structural-acoustic coupling characteristics of honeycomb sandwich plate based on parameter sensitivity analysis [J]. Journal of Central South University, 2014, 21(1): 252-261

[33] WangP, JonesS L, YangQ, GurupackiamS. Sensitivity analysis of key input parameters in conditional cell transmission model for oversaturated arterials [J]. Journal of Central South University, 2013, 20(6): 1772-1780

[34] ZhangL-x, QinJ, HeY-x, YeY, NiL-lin. Network-level optimization method for road network maintenance programming based on network efficiency [J]. Journal of Central South University, 2015, 22(12): 4882-4889