| Renewable energy such as solar energy and biogas is the best solution for problems of the energy crisis and environmental pollution it can share with a big percentage in solving these problems in China.The present work aims to use the solar energy in a novel method to dewater the biogas slurry.The present work is divided into two main parts:estimating the solar radiation in the site of interest to design the solar energy dewatering biogas slurry system and used this information to develop the simulation model for whole system;and studying the possibility of using rice straw for adsorption the nutrients from biogas slurry and design the solar energy dewatering biogas slurry system,running the experiment and get the data,then developing a simulation model for the system and validate it by the experimental results.For the most application of solar energy,an accurate information of solar radiation amount received by a horizontal surface is the first step.Hence,three studies were performed in the first part in this work to determine and calculate the solar energy potential in Wuhan and China using the available data in the site of interest;the first study suggested that there is no data available to estimate the daily global solar radiation（DGSR）on a horizontal surface,hence,he number of the day was used as input to the models and general models were identified for each zone in China.Nine-day of the year-based models were calibrated and evaluated to estimate DGSR using long-term data of 84 stations all over China.After dividing China into five solar climatic zones,the highest performance model for each zone was chosen to be a general day of the year-based models and then calibrate and evaluated at each solar zone.The results indicated model D7 is the best for zone I and model D8 for zones II and IV.For zones III and V,the Gaussian form model（D3 model）and the 4th order polynomial model（D4 model）yield high performance,respectively.The second study focused on estimating the monthly average DGSR on a horizontal surface in Wuhan city using the available data and propose a plan for choosing the best accurate model according to the data record.Seven existing models and four proposed models were calibrated and evaluated using measured meteorological data from 2006 to 2011.The results showed that the sunshine duration（n）is an important parameter for estimating DGSR and adding the dew point temperature（DP）is a significant effect in humid regions especially in Wuhan.Using the simple linear?ngstr?m–Prescott model（A-P）was better than using the more complex Bahel model or Ododo model.Models based on the maximum,minimum and average air temperature and DP exhibited poor performance.The worst performance was displayed by the Badescu model,which uses only cloud cover as a key input.The third study in this part aimed to examine the literature gaps by evaluating recent predictive models and categorizing them into various groups depending on the input parameters,and comprehensively collect the methods for classifying China into solar zones.The selected groups of models include those that use sunshine duration,temperature,dew-point temperature,precipitation,fog,cloud cover,day of the year and different meteorological parameters（complex models）.220 empirical models were analyzed for estimating the DGSR on a horizontal surface in China.Additionally,the most accurate models from the literature were summarized for 115 locations in China and were distributed into the above categories with the corresponding solar zone;the ideal models from each category and each solar zone were identified.The second part from this work design the solar energy dewatering biogas slurry system,carried out the experiment developing and validate the simulation model.In the first study from this part,the rice straw possibility for absorption nutrients from biogas slurry was studied.The most abundant nutrients in biogas slurry was selected as example which is the ammonium nitrogen.The effect of rice straw thickness,rice straw particle size,and biogas slurry flow rate on the adsorption efficiency of ammonium nitrogen and total phosphors from biogas slurry.The results indicted to small particle size of straw achieved the highest performance where using one stage can absorb 46%of ammonium nitrogen and more than 42%of total phosphors.The factors that yielded the best performance are 0.5 L/min biogas slurry flow rate,150 mm thickness of straw and 0.355 mm rice straw particle size.From this conclusion,the rice straw can be used for absorption the nutrients from biogas slurry combined with the solar energy system for dewatering the biogas slurry as presented in next study.The solar energy dewatering biogas slurry system consisted of greenhouse covered with plastic cover and spray system supported with nozzles to convert the biogas slurry to small drops.Then,using suction fan to move the inside air to outside.The experiment was carried out during two different days using biogas slurry flow rates of 22.64×10-6 m3/s and 26.70×10-6 m3/s and air speeds at inlet and outlet of 1.0 m/s and 4.5 m/s.The high incident values of solar radiation results to increasing the heat absorbed by the greenhouse cover and leads to increasing its temperature.In the first day,the solar radiation and cover temperature ranged from 531 W/m2 to 1526 W/m2and 27.7°C to 44.6°C,respectively and the biogas slurry dewatering efficiency ranged from36.97%to 98.90%with average value of 63.95%.As,in the second day,the solar radiation and cover temperature ranged from 191 W/m2to 381 W/m2and 26.0°C to 29.4°C,respectively and the biogas slurry dewatering efficiency ranged from 25.67%to 60.02%with average value of 41.43%.During the experiment the inlet biogas slurry to the system was measured and the leachate was collected and measured to collect the concentration rate of biogas slurry during the experiment time.It should be mention that some time was left in the beginning of the experiment to ignore the amount of biogas slurry that absorbed by rice straw.The concentration biogas slurry percentage was 57.39%and the energy consumption during the experiment time also was calculated.It was 4.40×10-3k Wh/kg of biogas slurry or 7.61×10-3k Wh/kg of evaporated biogas slurry.These results illustrated that the solar energy can be used efficiently by this system for dewatering the biogas slurry and save energy.In the last study the simulation model for the system was developed using the presented information and models in the first part from this work and validated by the experimental results.The results illustrated that The mathematical model can be used to predict the greenhouse cover temperature,inside air temperature,rice straw temperature,and air humidity ratio with acceptable range of accuracy according to the root mean square error,the relative root mean square error,standard error and relative percentage error.The comparison between the predicted and measured values of all parameters was investigated.For example,,the predicted line of humidity ratio of inside air followed the measured line with value of average absolute e 9.37%and 9.17%,RMSE value of 0.0112 kg/m3and 0.0117 kg/m3,SE value of0.171×10-3 kg/m3and 0.207×10-3 kg/m3,and r RMSE was 11.11%and 10.17%（<20%）at26.70×10-6 m3/s and 22.64×10-6 m3/s biogas slurry flow rates in the two different days,respectively.Therefore,the model can be used to predict the humidity ratio of air with good accuracy and the solar energy can be used efficiently by this the suggested system for dewatering the biogas slurry and save energy. |
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