Hydrogen can be produced by gasification of biomass and other combustible fuels. Depending on oxydant agents, syngas or producer gas compositions become quite different. Since biomass has limited amount of hydrogen including moisture in it, the hydrogen concentration in the syngas is about 15% when air is supplied for oxidant agent. Experiments were conducted to investigate the channges in hydrogen concentrations in syngas with different oxidant agent conditions, fuel conditions, and external heat supply. Allothermal reaction resulted in higher concentrations of hydrogen with the supply of steam over air, reaching over 60%. Hydrogen is produced by water-gas and water-gas shift reactions. These reactions are endothermic and require enough heat. Autothermal reaction occurred in the downdraft gasifier used in the experiment did not provide enough heat in the reactions for hydrogen production. Steam seems a more desirable oxidant agent in producing the syngas with higher concentrations of hydrogen from biomass gasifications since nitrogen is included in syngas when air is used.
Modification of an LPG Engine Generator for Biomass Syngas Application
Syngas, also known as synthesis gas, synthetic gas, or producer gas, is a combustible gas mixture generated when organic material (biomass) is heated in a gasifier with a limited airflow at a high temperature and elevated pressure. The present research was aimed at modifying the existing LPG engine generator for fully operated syngas. During this study, the designed gasifier-powered woodchip biomass was used for syngas production to generate power. A 6.0 kW LPG engine generator was modified and tested for operation on syngas. In the experiments, syngas and LPG fuels were tested as test fuels. For syngas production, 3 kg of dry woodchips were fed and burnt into the designed downdraft gasifier. The gasifier was connected to a blower coupled with a slider to help the air supply and control the ignition. The convection cooling system was connected to the syngas flow pipe for cooling the hot produce gas and filtering the impurities. For engine modification, a customized T-shaped flexible air/fuel mixture control device was designed for adjusting the correct stoichiometric air-fuel ratio ranging between 1:1.1 and 1.3 to match the combustion needs of the engine. The composition of produced syngas was analyzed using a gas analyzer and its composition was; 13∼15 %, 10.2∼13 %, 4.1∼4.5 %, and 11.9∼14.6 % for CO, H2, CH4, and CO2 respectively with a heating value range of 4.12∼5.01 MJ/Nm3. The maximum peak power output generated from syngas and LPG was recorded using a clamp-on power meter and found to be 3,689 watts and 5,001 watts, respectively. The results found from the experiment show that the LPG engine generator operated on syngas can be adopted with a de-ration rate of 73.78 % compared to its regular operating fuel.
Establishment of Condition Assessment Criteria in Agricultural Reservoirs by AHP
심재웅 Shim Jae-woong , 이영학 Lee Young-hak , 이달원 Lee Dal-won
In this study, in order to establish the criteria for evaluation of importance by the type of facility specialized for agricultural reservoirs, an expert group consisting of a total of 167 members who were in management, or specialized in the fields of design, research, and diagnosis were organized, and the importance for facilities was set with application of the AHP technique. The importance of dam body, spillway, and intake structure composing a reservoir were set at 59%, 24%, and 17%, and the importance of dam crest, upstream slope, and downstream slope constituting a dam body was set at 32%, 31%, and 37%, respectively. In addition, the importance of approach channel, regulated channel, chute channel, and stilling basin consisting a spillway was set at 15%, 44%, 26%, and 15%, and the importance of inclined conduit and outlet conduit consisting an intake structure was set at 35% and 65%, respectively. The safety grade of the reservoirs evaluated by applying the newly presented importance values in this study showed the rearrangement of the grades with a change of 11% compared to the previous grades. In this way, the newly established criteria are expected to be utilized as basic data with strategic importance in reservoir safety management and disaster prevention as well as the operation of systems in the future.
Data-Based Model Approach to Predict Internal Air Temperature in a Mechanically-Ventilated Broiler House
최락영 Choi Lak-yeong , 채영현 Chae Yeonghyun , 이세연 Lee Se-yeon , 박진선 Park Jinseon , 홍세운 Hong Se-woon
The smart farm is recognized as a solution for future farmers having positive effects on the sustainability of the poultry industry. Intelligent microclimate control can be a key technology for broiler production which is extremely vulnerable to abnormal indoor air temperatures. Furthermore, better control of indoor microclimate can be achieved by accurate prediction of indoor air temperature. This study developed predictive models for internal air temperature in a mechanically-ventilated broiler house based on the data measured during three rearing periods, which were different in seasonal climate and ventilation operation. Three machine learning models and a mechanistic model based on thermal energy balance were used for the prediction. The results indicated that the all models gave good predictions for 1-minute future air temperature showing the coefficient of determination greater than 0.99 and the root-mean-square-error smaller than 0.306℃. However, for 1-hour future air temperature, only the mechanistic model showed good accuracy with the coefficient of determination of 0.934 and the root-mean-square-error of 0.841℃. Since the mechanistic model was based on the mathematical descriptions of the heat transfer processes that occurred in the broiler house, it showed better prediction performances compared to the black-box machine learning models. Therefore, it was proven to be useful for intelligent microclimate control which would be developed in future studies.
Evaluation Methods of Carbon Reduction Contribution for Green Budget of National R&D Projects in Agricultural Sector
김솔희 Kim Solhee , 한승현 Han Seunghyun , 강성수 Kang Seong-soo , 서교 Suh Kyo
Carbon neutrality is emerging as a new paradigm for the international society by transiting from climate change to climate risk. This study proposes evaluation methods for the carbon reduction contribution of climate-related national R&D projects in order to introduce a green budget system in the agricultural sector. We considered the domestic and foreign green budget systems and classified national R&D projects into positive, negative, and neutral from the perspective of carbon reduction. The results of this study propose three methods to estimate the monetary costs and carbon benefits by adopting the framework for the economic evaluation of national R&D projects conducted by the Rural Development Administration. These methods support to evaluate the potential contribution to carbon reduction of national R&D projects in the agricultural sector. Finally, the proposed methods were tested and verified for the efficiency and validity of evaluating carbon reduction contribution. These evaluation methods of the carbon reduction contribution can be used as a basic methodology for the pre-budget calculations of national R&D projects and the contribution for the greenhouse gas reduction budget.
Assessment of Flood Vulnerability for Small Reservoir according to Climate Change Scenario - Reservoir in Gyeonggi-do -
허준 Heo Joon , 봉태호 Bong Tae-ho , 김성필 Kim Seong-pil , 전상민 Jun Sang-min
Most of the reservoirs managed by the city and county are small and it is difficult to respond to climate change because the drainage area is small and the inflow increases rapidly when a heavy rain occurs. In this study, the current status of reservoirs managed by city and county in Gyeonggi-do was reviewed and flood vulnerability due to climate change was analyzed. In order to analyze the impact of climate change, CMIP6-based future climate scenario provided by IPCC was used, and future rainfall data was established through downscaling of climate scenario (SSP8-8.5). The flood vulnerability of reservoirs due to climate change was evaluated using the concept provided by the IPCC. The future annual precipitation at six weather stations appeared a gradual increase and the fluctuation range of the annual precipitation was also found to increase. As a result of calculating the flood vulnerability index, it was analyzed that the flood vulnerability was the largest in the 2055s period and the lowest in the 2025s period. In the past period (2000s), the number of D and E grade reservoirs was 58, but it was found to increase to 107 in the 2055s period. In 2085s, there were 17 E grade reservoirs, which was more than in the past. Therefore, it is necessary to take measures against the increasing risk of flooding in the future.
Structural System Reliability Analysis of Semi-rigid Connected Frame - Focused on Plastic Greenhouse -
이상익 Lee Sangik , 이종혁 Lee Jonghyuk , 정영준 Jeong Youngjoon , 김동수 Kim Dongsu , 서병훈 Seo Byunghun , 서예진 Seo Yejin , 최원 Choi Won
Recently, the trend in structural analysis and design is moving towards the development of reliable system. The reliability-based method defines various limit states related to usability and failure, thereby enabling multiple levels of design according to the importance of a structure. Meanwhile, an actual structure is composed of a set of several elements, and particularly, a frame type is composed of a system in which the members are connected each other. At this time, the actual connection between members is in a semi-rigid condition, not in complete rigid or hinged. This semi-rigid is found in several structures, especially in agricultural facilities designed with lightweight materials. In this study, a system reliability analysis technique for frame structure was established, and applied to an analysis of the semi-rigid connection. Various conditions of correlation were applied to reflect the connectivity between members, and through this, the limitations of existing structural analysis method and the behavioral characteristics of structure were analyzed. The failure probability of the frame member component and the overall structure system was significantly different in consideration of the semi-rigid connection. In addition, it was evaluated that the behavior of structure can be more accurately analyzed if the correlation according to the position of members in a system is further investigated.
