Case of energy system in northwest China

Abstract

In rural areas of northern China, cooking, household appliances, and winter heating make up the basic energy consumption which almost totally depends on coal until now while renewable energy, such as solar energy, biomass, and wind energy, is abundant in these areas. Great efforts have been made to meet one of basic energy demands with renewable energy. However, unsteady renewable energy has significantly challenged the reliability of the renewable energy system and users' expectations. Hence, in order to meet multilevel energy demands above with solar energy and biomass and to efficiently overcome the influences of seasons, climates, environment temperature, and other factors on renewable energy production, an energy system of combined heating, power and biogas (CHPB), was developed and tested in a 117.07 m 2 insulated rural building. The CHPB system is composed of solar water collectors, PV arrays with batteries, thermostatic biogas digesters, and other devices. Besides, to keep the temperature of the biogas digester stable, the solar water collector is also used to heat the building in winter. PV arrays with batteries supply electricity for the system and household appliances, while biogas is used for cooking. The CHPB system shows favorable performances in heating period of 2014-2015, according to the theoretical analysis on efficiency, conservation, and environmental benefits of the system in winter. The energy supply performance of CHPB in winter is studied experimentally. The test results show that: (1) During the heating periods, the energy supplied by the system used for building heating meets 69% of the building needs. When the daily average ambient temperature is higher than 3 °C, the system is capable of meeting the energy demands of building heating completely, while when the accumulated daily solar radiation is less than 14 MJ/m 2 , the system fails to meet the energy demands of building heating; (2) The total biogas produced by the system in the test is 110.71m 3 , with an average methane content of 54.74% which always meets the cooking fuel demands of the residents; (3) Most of the time, the daily electricity generation is higher than the electricity consumed by CHPB and relies on batteries. Besides, the generated electricity had met the demands of CHPB all the time, and the system can meet the electricity demands of the residents partly in the heating periods and completely in the nonheating periods.