| Rural areas are the main space for human life.China has more than 500 million rural population,accounting for 36.11%of the total number of the country.However,compared with cities,China’s rural economic conditions are poor,and infrastructure construction is still at a low level,especially in rural toilets.Since the 18 th National Congress of the Communist Party of China,the Party Central Committee and the State Council have proposed to carry out the"toilet revolution"and incorporate rural toilet reform into the rural revitalization strategy.In the northwest rural areas of China,due to the backward economy,bad weather,cold and dry winter,it is very inconvenient for rural residents to toilet in winter.Therefore,under the background of"toilet revolution"and"clean heating",it is of great significance to improve the winter thermal environment of rural toilets by using local abundant solar energy resources.Firstly,this paper investigates the construction of toilets in rural areas of Qinghai Province,and finds that the vast majority of local rural toilets are dry toilets,only 11.9%of public toilets and 15.6%of household toilets are flush toilets,and 56.3%of farmers expressed their hope to improve the winter heat preservation and heating conditions of toilets.Through questionnaire survey,the tolerance of local rural residents to low temperature is slightly higher than that of township and urban residents.The acceptable critical temperature for local residents to the indoor temperature of the toilet is 5°C,and the critical temperature for them to feel comfortable is 11°C.Secondly,an active and passive solar toilet experimental platform was built in a village in Qinghai Province,and its operation under different operating conditions was tested on the spot.The results showed that the average daily heat of the collector wall was 4.64 MJ.The average indoor temperature of the toilet under the pure passive operating condition(operating condition 2)is 11.3°C,and the number of hours when the average indoor temperature reaches 11°C accounts for 37.5%,of which 54.5%and 23.1%of the time reaches 11°C during the day and night respectively.Under the active and passive combined operating condition(operating condition 3),the daily heat collection of the active solar heating system is 16.24 MJ～20.30 MJ,the heat supply is 4.63 MJ～10.12 MJ,and the average heat supply efficiency is 43%;the average indoor temperature is 11.7°C,and the average indoor temperature reaches more than 11°C in 59.4%and 35.9%of the day and night respectively,which is higher than that of condition 2.Thirdly,TRNSYS is used to model the experimental toilet.On the basis of model verification,the operation of the experimental toilet in the whole heating season is simulated.The results show that the highest hourly temperature in the toilet room is31.1°C,the lowest is-9.6°C,and the average hourly temperature in the room is 7.3°C.During the heating period,the proportion of time when the indoor temperature of the toilet is above the acceptable critical temperature of 5°C and the comfortable critical temperature of 11°C is 56.7%and 32.7%respectively.The heating capacity of the active and passive solar system in the whole heating season is 2585.63 MJ,of which the heating capacity of the passive system is 949.73 MJ,and the heating capacity of the active system is 1635.90 MJ,and the contribution rates are 36.7%and 63.3%respectively.Finally,by simulating the heating load under different design temperatures,the low-frequency period(21:00～7:00 of the next day)5°C and high-frequency period(7:00～21:00)11°C are determined as the heating design temperature.At this time,the cumulative heating load of the benchmark building(experimental toilet)in the heating season is 786.9 k W·h,and the cumulative auxiliary heating load is 401.6 k W·h.The thickness of the insulation layer of the retaining structure,the area of the passive collector wall,the combination of the active solar system and the running time are optimized and analyzed,and the optimal design scheme of this study is obtained.The design parameters are as follows:the thickness of the external wall insulation layer is250 mm,the thickness of the roof insulation layer is 200 mm,the area of the passive collector wall is 4 m~2,the area of the solar hot water collector is 4 m~2,and the volume of the heat storage tank is 300 L;the heating time of the active system is 10:00-17:30,and the heating time is 17:30-10:00.The cumulative auxiliary heating load under this scheme is 103.5 k W·h,and the energy saving rate is 86.8%,which is 74.2%lower than that of the benchmark building.When other auxiliary heat sources are not used,the time when the indoor temperature reaches 5°C and 11°C in the whole heating season is 88.5%and 58.1%,respectively.Only 0.4%of the time the indoor temperature is lower than 0°C,and the toilet thermal environment improvement and energy saving effect are obvious.The annual cost per unit area of the optimization scheme is 195.3 yuan/m~2,which is 16.8 yuan/m~2 higher than that of the benchmark building.With the electric auxiliary heating equipment as the auxiliary heating source,the auxiliary heating cost of the optimized scheme in the heating season is 9.8 yuan/m~2,which is 64.4 yuan/m~2 lower than that of the reference building without the active and passive solar system.The initial investment payback period is 15 years. |
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