Abstract
The energy reserves in hot dry rock and hydrothermal systems are abundant in China, however, the developed resources are far below the potential estimates due to immature technology of enhanced geothermal system (EGS) and scattered resources of hydrothermal systems. To circumvent these problems and reduce the thermal resistance of rocks, here a shallow depth enhanced geothermal system (SDEGS) is proposed, which can be implemented by fracturing the hydrothermal system. We find that, the service life for SDEGS is 14 years with heat output of 4521.1 kW. To extend service life, the hybrid SDEGS and solar energy heating system is proposed with 10,000 m2 solar collectors installed to store heat into geothermal reservoir. The service life of the hybrid heating system is 35 years with geothermal heat output of 4653.78 kW. The novelty of the present work is that the hybrid heating system can solve the unstable and discontinuous problems of solar energy without building additional back-up sources or seasonal storage equipment, and the geothermal thermal output can be adjusted easily to meet the demand of building thermal loads varying with outside temperature.
Highlights
By the end of 2016 in north China, a total of 20.6 billion m2 building floor areas had space heating, about 83% of space heating areas used coal boiler or coal CHP, and the annual coal consumption was 400 million ton-coal-equivalent [1]
The main aim of this study is to evaluate the performance of the hybrid shallow depth enhanced geothermal system (SDEGS) and solar system for building heating
The actual heating load is assumed to be 20% less than the from solar energy into deep borehole heat exchanger (DBHE) is restricted due to rock having poor thermal conductivity
Summary
By the end of 2016 in north China, a total of 20.6 billion m2 building floor areas had space heating, about 83% of space heating areas used coal boiler or coal CHP (combined heat and power), and the annual coal consumption was 400 million ton-coal-equivalent [1]. There is an urgent need for clean energy building heating technology at the present stage. The energy reserves in hot dry rock (HDR) within subsurface of 3–10 km depths are more than. To extract heat from HDR, the enhanced geothermal system (EGS) is proposed by creating artificial fractures in the hot rocks and injecting fluid into them [7,8,9,10]. The exploiting technology of EGS is immature. The hydrothermal heating area in China was only 102 million m2 by the end of Energies 2020, 13, 2473; doi:10.3390/en13102473 www.mdpi.com/journal/energies
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