• Energy Research

Nowadays, biogas is widely used as a renewable energy source due to the increasing price of fossil fuels and is commonly produced from the agriculture industry. However, it mainly consists of carbon dioxide and methane, which both have impact on climate change and global warming. The objective of this study is to explore the environmental impact of biogas production from the manure of dairy cows. Normally, the potential of biogas production depends on the manure characteristics of the cows. As a result, the manure characteristics of the cows are therefore dependent on their diet. Theoretically, the dietary influences on the component ratio of the biogas. In this study, three different cow diets are used. Three samples of biogas are examined for each diet for more accuracy. The results show that the different diets of the cows have an effect on the biogas production, CO2 and CH4 contents, and the total greenhouse gas emissions. Moreover, the total greenhouse gas emissions of the biogas used are reduced as compared to the equivalent use of natural gas by 43.6%, 43.8%, and 44.2% for the diet types of T1, T2, and T3, respectively.

Les modules de refroidissement thermoélectrique (TEC) sont réalisés dans de nombreux appareils en raison de leur dimensionnement flexible. Cette application a besoin d'un courant continu pour produire un effet de refroidissement. Dans cette étude, l'expérience s'est concentrée sur la conception du système de refroidissement en utilisant le TEC dans une paroi sous vide. La paroi sous vide est connue pour être bien isolée, ce qui contribue à réduire la charge thermique des applications. Une boîte de refroidissement pour la conservation du vaccin a été conçue dans cette étude, avec une température intérieure variant entre 17, 19, 21, 23 et 25 °C. Des conditions de vide de −15, −20 et −25 en Hg ont été utilisées. Les résultats montrent que la puissance requise diminue lorsque la température intérieure augmente. Le TEC peut également contrôler la température intérieure, lorsque la température ambiante extérieure est légèrement différente dans toutes les conditions d'essai. La puissance varie directement avec le niveau de vide, ce qui montre que la paroi de vide peut réduire la charge thermique de l'environnement extérieur. De plus, la corrélation de l'exigence de puissance dans laquelle la température intérieure peut être prédite avec un bon accord est rapportée. Los módulos de enfriamiento termoeléctrico (TEC) se están logrando en muchos dispositivos debido a su tamaño flexible. Esta aplicación necesita un DC para hacer un efecto de enfriamiento. En este estudio, el experimento se centró en el diseño del sistema de refrigeración utilizando TEC en una pared de vacío. La pared de vacío se conoce como bien aislada, lo que ayuda a reducir la carga de calor de las aplicaciones. En este estudio se diseñó una caja de enfriamiento para conservar la vacuna, con una temperatura interior que variaba entre 17, 19, 21, 23 y 25 °C. Se utilizaron condiciones de vacío de -15, -20 y -25 en Hg. Los resultados muestran que la potencia requerida disminuye cuando aumenta la temperatura interior. El TEC también puede controlar la temperatura interior, cuando la temperatura ambiente exterior es ligeramente diferente en todas las condiciones de prueba. La potencia varía directamente con el nivel de vacío, lo que demuestra que la pared de vacío puede reducir la carga de calor del entorno exterior. Además, se informa la correlación del requisito de potencia en el que se puede predecir la temperatura interior con un buen acuerdo. Thermoelectric cooling (TEC) modules are being accomplished in many devices due to their flexible sizing. This application needs a DC to make a cooling effect. In this study, the experiment was focused on the cooling system design using TEC in a vacuum wall. The vacuum wall is known as being well-insulated which helps to reduce the heat load of applications. A cooling box for vaccine preservation was designed in this study, with the inside temperature varied between 17, 19, 21, 23, and 25 °C. Vacuum conditions of −15, −20, and −25 in Hg were used. The results show that the power required decreases when the inside temperature increases. The TEC can control the inside temperature as well, when the outside ambient temperature is slightly different in all testing conditions. The power varies directly with the vacuum level, which shows that the vacuum wall can reduce the heat load from the outside environment. Moreover, the correlation of the power requirement in which the inside temperature can be predicted with good agreement is reported. يتم إنجاز وحدات التبريد الكهربائي الحراري (TEC) في العديد من الأجهزة بسبب حجمها المرن. يحتاج هذا التطبيق إلى تيار مستمر لإحداث تأثير تبريد. في هذه الدراسة، ركزت التجربة على تصميم نظام التبريد باستخدام TEC في جدار التفريغ. يُعرف جدار التفريغ بأنه معزول جيدًا مما يساعد على تقليل الحمل الحراري للتطبيقات. تم تصميم صندوق تبريد لحفظ اللقاح في هذه الدراسة، مع اختلاف درجة الحرارة الداخلية بين 17 و 19 و 21 و 23 و 25 درجة مئوية. تم استخدام ظروف الفراغ من -15 و -20 و -25 في الزئبق. تظهر النتائج أن الطاقة المطلوبة تنخفض عندما ترتفع درجة الحرارة الداخلية. يمكن لـ TEC التحكم في درجة الحرارة الداخلية أيضًا، عندما تكون درجة الحرارة المحيطة الخارجية مختلفة قليلاً في جميع ظروف الاختبار. تختلف الطاقة بشكل مباشر مع مستوى التفريغ، مما يدل على أن جدار التفريغ يمكن أن يقلل من الحمل الحراري من البيئة الخارجية. علاوة على ذلك، يتم الإبلاغ عن ارتباط متطلبات الطاقة التي يمكن من خلالها التنبؤ بدرجة الحرارة الداخلية باتفاق جيد.

This study developed a heat load model of an air-conditioned room using multiple linear regression. A sensitivity analysis was first used to simplify the heat load model by neglecting the less sensitive levels of independent variables. The experiments were tested in three thermostat setting conditions of 25, 26, and 27 °C. The experimental data were collected to determine normalized sensitivity coefficients and regression coefficients of the heat load model. The sensitivity analysis results showed that the radiation parameters had a major impact on heat load. Furthermore, the air-conditioned room properties did not give a significant difference in the heat load as compared to other parameters. Moreover, the heat load model with the regression coefficients was reported, as well as the correlation coefficient. This model gave a good prediction of the heat load with an error of 0.15%.

The objective of this study is to develop and compare two simplified heat load models for air-conditioned rooms. The heat load models are intended for use in a demand response (DR) program in future work, to solve critical electricity peaks from air-conditioners used. Buckingham-Pi theorem was applied to develop the heat load model in this study. Moreover, another heat load model using sensitivity analysis and multiple linear regression was developed in this study. Then, the result of the heat load model using Buckingham-Pi theorem was compared to the heat load model using sensitivity analysis and multiple linear regression to identify the advantage of both heat load models. In this study, heat load model using the Buckingham-Pi theorem was successfully developed. A heat load model with three independent variables was recommended for heat load prediction. The results showed that the heat load model gave a good prediction of the heat load with an RMSE of 4.82%. However, the RMSE of predicting the heat load model using sensitivity analysis and multiple linear regression is 0.55% using a model with ten independent variables. The comparison shows that the heat load model using Buckingham-Pi theorem has a good agreement and simplifies the model better than using sensitivity analysis and multiple linear regression.