Yuji Ryu

Field Study and Sensitive Analysis of PV System by Multiple Regression Method

Abstract In this paper, the PV system in Kitakyushu Science and Research Park (KSRP) in Japan has been introduced. By analyzing the recorded data in 2002, the power generation result has been evaluated. On the basis of this, comprehensive module conversion efficiency for two different photovoltaic cells, single-crystal and multi-crystal, has been discussed. Furthermore, the factors influencing power generation amount and module conversion efficiency have been analyzed by using the single regression and the multiple regression method. And the environment contribution also has been evaluated. The results can be summarized as follows: 1) Although the PV system has been responsibility for little part of power consumption at KSRP, it has high reliability and stable running situation. 2) The average hourly module conversion efficiency is 10.6%, about 74.1% of comprehensive conversion efficiency with 14.3%. 3) Irradiance is the most important influence factor on power output of PV system and almost in direct proportion with power generation amount. The influence from air temperature is important than the one from wind velocity on power output, but the influence from them are both very small. 4) PV system has contributed to reduce environmental load greatly.

Evaluation of the Energy and Environmental Performance by Introducing a District Energy System

Abstract In Kitakyushu Science and Research Park, a new district energy system has been introduced. In this study, we chose this system as a case study and have carried out an analysis on the efficiency of the power generation and heat release utilization of the fuel cell and gas engine in summer by using recorded data. The results can be summarized as follows; 1) Although the power generation efficiencies of the gas engine and fuel cell are slightly lower than the standard designated value, they are almost constant throughout the period of study. 2) The collected heat energy is lower than the designated value. The heat release utilization, which is used for cooling and hot water, is lower than expected. Considering the efficient use of energy for such systems, it is important to have a good use of heat release when we introduce a district energy system. 3) The discarded heat energy of the system is very big in this investigation when evaluating the system as a whole. It is fundamental to the future of energy conservation to use primary energy more efficiently.

Evaluation Research on the Introduction Effect for Various Energy Supply Systems for Detached Houses

Abstract In this paper, seven cases with three different options for energy provision, PV, co-generation and all-electrified system, have been assumed for a detached house. In order to obtain an energy-saving effect, a new theory concerning the determination of running schedule for the co-generation system has been presented. On this basis, the outcomes for various options have been evaluated regarding the energy-saving, environmental and economic effects. The results can be summarized as follows: (1) A function relationship between the heat-to-power ratio and energy saving has been proposed. Moreover, expressions to calculate the minimum thermal utilization efficiency and the electric generating efficiency for the track electricity and track thermal operation modes also have been derived. (2) Energy supply systems using PV can achieve excellent effects considering each evaluating index. However, because of the high initial cost, the payback period is longer than for other systems, at more than 9 years. (3) The co-generation system can achieve energy-saving and environmental effects. In addition, with the remarkably low running cost, its payback period is less than 4 years. (4) The energy saving and environmental effect of the all-electrified energy supply system depends on the COP/efficiency performance of electricity consumption equipment. However, the economic effect is excellent compared with the reference system.

Examination of the Viability of Co-generation for a Small-scale Housing Development in Kitakyushu, Japan

Abstract A multidisciplinary team comprising researchers at Cranfield University at Kitakyushu, a local architectural and engineering practice and the Development Office for KSRP examined how urban form could enhance the opportunities for more sustainable development. Options for energy provision particularly was considered at the scale of the overall site development and for the individual dwellings, as apartments, terraced and detached housing. A holistic approach was taken for the development of a 1-hectare site in order to assess the potentials and opportunities for energy systems and environmental solutions at this scale. Subsequently a team from Cranfield University at Kitakyushu and the Environmental Engineering Faculty at Kitakyushu University investigated options for cogeneration on this development site in the form of Combined Cooling Heat and Power (CCHP). The options ranged from a centralised system based within the apartment building that served all the dwellings on the site to individual 1 kW electric cogeneration systems that served individual dwellings. A computer software model was used to examine the energy efficiencies of these options from hourly through to annual timescales, based upon typical electricity, heating, cooling and hot water consumption profiles for Japanese dwellings. In Japan a hot bathtub is filled each evening throughout the year and is used by the whole family. This constitutes a base load for hot water consumption that could be served through thermal storage. At present high output capacity gas boilers are used to provide the hot water for this purpose. Consequently, the computer models considered modes and scales of thermal storage as one of the key parameters for the examination of the relative viability of the options considered. The analysis was carried out using hourly weather data provided by a Test Reference Year weather data file for the local area.

Investigation and Evaluation on District Energy System at Kitakyushu Science and Research Park : Field Study on Running Situation during 2002(Environmental Engineering)

Abstract A district energy system in Kitakyushu Science and Research Park (KSRP) has been introduced. In this paper, the system′s running situation was analyzed by using the recorded data in 2002. Generating electricity, heat recovery efficiency and recovery heat utilization efficiency for gas engine and fuel cell were calculated. On the basis of the above study, energy saving and CO2 reduction were evaluated. The results can be summarized as follows: 1) The on-site generating electricity equipments provided 51.2% of the total electricity demand, including fuel cell with 34.5%, gas engine with 13.4% and PV system with 3.3%. In total heat energy demand, 70% of hot water load, 30.9% of cooling load and 14.3% of heating load were provided by recovering the heat energy from fuel cell and gas engine system. 2) Fuel cell was running 8572 hours with constant generating electricity efficiencies, about 30.8%. Gas engine only run 4281 hours with higher generating electricity efficiencies, about 24.5%. PV system achieved over 8% module conversion efficiencies in 83% of generating electricity time. 3) Fuel cell had lower heat recovery efficiency, but this heat energy recovered almost was utilized by the heat exchanger or absorption chiller. Gas engine had higher heat recovery efficiency, but only 70% of them were utilized by heat recovery equipments. 4) Compared with the conventional energy supply system, the district energy system achieved 56% primary energy utilization efficiency, 10.9% saving energy ratio and 1.32% CO2 reduction ratio.

EXPERIMENTAL STUDY ON THERMAL CHARACTERISTICS OF HVAC SYSTEM WITH CEILING PLENUM BUILDING STRUCTURE THERMAL STORAGE AND THAT WITH UNDERFLOOR PLENUM BUILDING STRUCTURE THERMAL STORAGE

The thermal performances of two types of Building Structure Thermal Storage HVAC system, the Ceiling Plenum type (SC) and Underfloor Plenum type (SF), were analyzed through real scale experiments under maximum cooling loads. Subsequently, they were compared with the performances of the ordinary HVAC systems without heat storage, with the ceiling air supply system (OC) and underfloor air supply system (OF) operated with and without pre-cooling operating hours. The results obtained were as follows:1) The SF system, that provides heat storage during the nighttime, in some cases supplies the stored heat inconveniently to building structures in the daytime cooling mode. Therefore the total daily loads for the SF system is greater for than the SC system. However, it reduces the cooling loads in the daytime.2) The pre-cooling operating mode in both the OC system and OF system is effective for the reduction of cooling loads in the daytime, but slightly inferior to the operation of the SC system and SF system.

INVESTIGATION ON A SUMMER OPERATION EFFECT OF A DISTRICT ENERGY SYSTEM AT KITAKYUSHU SCIENCE RESEARCH CITY(Environmental Engineering)

In Kitakyushu Science and Research Park, a new district energy system has been introduced. In this study, we chose this system as a case study and have carried out an analysis on the efficiency of the power generation and heat release utilization of the fuel cell and gas engine in summer by using the recorded data. The results can be summarized as follows; (1) Although the power generation efficiencies of the gas engine and fuel cell are a little bit lower than the standard designated value, they are almost running at stable condition. (2) The collected heat energy is lower than the designated value. The heat release utilization, which is used for cooling and hot water, is fairly low. Considering the efficient use of energy, it is a key to have a good use of heat release when we introduce a district energy system. (3) The discarded heat energy of the system is very big in this investigation when evaluating the system as a whole. It is fundamental to the future of energy conservation to use primary energy more efficiently.