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Energy and the environment is a hot issue of general concern in the world today. Non-renewable fossil fuel-based energy consumption is exacerbated by the destruction of the human survival environment, threats to sustainable human development. The development and utilization of environmentally friendly renewable energy has become a necessity. Solar and biomass resources of a large amount of very widespread distribution of these renewable energy. The the biomass anaerobic fermentation technology and low-temperature solar collector technology is a currently two mature technology. The anaerobic fermentation of biomass technology to effectively solve the problem of fuel shortages in rural areas, to achieve safe handling of livestock manure and multi-level resource utilization, and therefore subject to the universal concern of all countries. However, the anaerobic fermentation process is severely affected by temperature, fermentation temperature is too low or fluctuating too fast, will affect the the anaerobic fermentation gas production rate and biogas CH4 content. The methods some the existing digesters warming insulation using biomass, coal, electricity and other energy, thermal energy conversion rate is low, easy to pollution, some warming insulation effect is difficult to control the process of anaerobic fermentation of biomass. The solar collector temperature of the economy with the thermostat anaerobic fermentation temperature matching the basis of integration of the solar collectors and the anaerobic fermentation of biomass. To this end, the subject of research and development of solar heating thermostat digesters. The system is the solar energy collected by the solar collectors, heat medium water supply fermenter to meet the fermentation of the heat required, breaking the shackles of the day and night, seasons, climate, and other unfavorable factors, to achieve a continuous and stable energy supply . In order to study the fermentation temperature, fermentation raw performance thermostat fermentation gas production, gas production properties and device performance and overall efficiency of solar heating thermostat digesters, this subject the following research work. Parallel four 11.5L fermenter batch experiments studied 19 ° C, 30 ° C, 37 ° C and 52 ℃ under fresh cow dung, fresh cow dung mixed with lotus leaves raw fermentation process and biogas analyzer real-time measurement of biogas, methane, carbon dioxide and hydrogen sulfide content, found that: (1) the concentration of cow dung fermentation of 8%, 38 days 52 ° C, 37 ° C, 30 ° C and 19 ℃ cumulative gas production were 173.12L, 187.59 of L, 153.41L and 39.12L, fermentation period of 22 days, 22 days, 27 days and 36 days, respectively, the cumulative amount of methane-producing fermentation cycle 90.44L, 100.47L, 79.35L 13.90L, tank volume gas production rate respectively 0.71m3/m3 · d, 0.76 m3/m3 · d, 0.51 m3/m3 · d and 0.10m3/m3 · d. 37 ℃ anaerobic fermentation gas production, gas production quality. (2) cow dung fermentation concentration of 4%, 22 days, 30 ° C at 37 ° C and 52 ℃ cumulative gas production were 41.69L 52.30L and 55.57L fermentation period of 16 days, 15 days and 14 days, fermentation cycle pool capacity gas production rate were 0.23 m3/m3 · d, 0.32 m3/m3 · d and 0.36 m3/m3 · d, cumulative methane production were 19.07L, 24.49L and 25.22L, the average methane content 51.07%, 51.76% and 50.63%, respectively. Compared with other temperature 52 ° C under a short fermentation period, the pool capacity high rate of gas production, biogas quality was the worst. Cow dung with lotus leaves VS quality than 3 the mixed raw fermented concentration 8% (3), 52 ℃, 37 ℃ and 30 ℃ experimental group cumulative gas production were 201.83L, 225.18L 195.76L, fermentation cycle 31 days, 42 days and 58 days, the tank volume rate of gas production were 0.65 m3/m3 · d, 0.54 m3/m3 · d and 0.34 m3/m3 · d, the cumulative amount of methane-producing 99.31L, 117.96L and 102.10L, the average methane content of 49.20%, 52.38% and 52.16%. Cow dung and lotus leaves mixed anaerobic fermentation can significantly improve the conversion rate of anaerobic fermentation of cow dung and lotus leaves. Under the experimental conditions, the fermentation cycle of 30 ° C, 37 ° C and 52 ℃ mixed raw anaerobic fermentation anaerobic fermentation than cow dung single raw cumulative gas production increased by 7.00%, 34.08% and 22.16%, respectively. VS mass ratio of 3:00, and the optimum fermentation temperature of 37 ° C; natural fermentation can not start mixing raw materials fermentation Lotus course content should be reduced, reducing the VFA inhibition of methanogenic bacteria, need real-time adjustment to pH. 2 in the average environmental temperature was 8.6 ° C, the solar heating thermostat digesters at 30 ± 2 ℃ stable operation, the total solids concentration of 7% peak gas production in the first 11 days, the gas production rate up to 2.059m3 / D ; maximum feed capacity of the gas production rate 0.86m3/m3 · d, fermentation period of 28 days; if the system is operating normally, simply 3m3 of biogas digesters to meet day boil water for cooking needs of a family of 4 to 5 . The financial net present value of the biogas plant, solar heating thermostat NPV (i = 10%) to 8,573 yuan, FIRR of 43.64% internal rate of return, benefit cost ratio is 2.80, dynamic payback period of 2.9 years. Gansu Province rural daily energy way cooking annual CO2 emission reductions of up to 2.35 × 107t, biogas alternative stalks, firewood and coal's contribution to CO2 reduction of 47.47%, 40.80% and 11.73%, respectively. The topic of innovation that: (1) Experimental study of the influence of the temperature on the thermostat anaerobic fermentation ability and found that the maximum amount of methane-producing anaerobic fermentation at 37 ℃, gas production of the highest quality; (2) research and development of new solar heating thermostat digesters, the pilot plant in Lanzhou region winter conditions can be stable biogas production. Heated digesters, solar heating of the subjects developed breakthrough time of the northern region, the season, the shackles of climate change on the anaerobic fermentation of biomass and effective solution to the methane gas production is low in winter, the problem of unstable gas production. Compared with the traditional digester insulation warming method, solar heating thermostat digesters more energy-saving and environmental protection, the anaerobic fermentation process controllable better. The research topics conducive to solar heating thermostat digesters in large scale in the northern region, thus promoting the transformation of peasant lifestyle to a more healthy, civilized, hygienic way to promote a new rural construction, reducing the need for traditional energy dependence, expanding the scope of the use of renewable energy, to improve the share of renewable energy use, energy and environmental sustainability.
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