A Fundamental Study for Designing a Safe and Eco-friendly Community

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1 A Fundamental Study for Designing a Safe and Eco-friendly Community Keisuke Yamamoto , Hiyoshi, Kohoku-ku, Yokohama, Kanagawa, Japan yamamoto-1@hs.sd.keio.ac.jp Takuya Kamayama Tomohiro Suzuki Jorge Almazan Haruki Sato hsato@sd.keio.ac.jp ABSTRACT After the Great East Japan earthquake on 11 March 211, a safe and eco-friendly urban city is strongly desired by Japanese citizens. Designing a safe and eco-friendly community from an energy-utilization viewpoint is discussed in this paper as a part of Cluster Energy Management System, CEMS, which is proposed by our group. A new software for predicting energy demand in a single house or a group of residential houses from dynamic behaviors of dwellers has been developed. As an example of the application, a reconstruction plan for Kamaishi-city in East Japan is designed. We have proposed an appropriate combination of energy supply for electricity and thermal energy by using the CEMS concept. A vision of energy supply introducing solar energy is also discussed. 1. INTRODUCTION Global warming due to consumption of fossil fuel beyond the limits of Nature s capacity should be immediately taken measures by utilizing renewable energies. The necessities for energy conservation and reduction of CO 2 are impossible to be denied. In Japan, energy consumption and CO 2 emission of residential sector keep rising. The CO 2 emission of residential sector increased 34% in 21 from 199 [1]. Besides the situation, the Great East Japan earthquake happened on 11th March 211 and the infrastructure systems of cities were completely destroyed. Therefore, a safe and eco-friendly community is strongly desired by Japanese citizens. Energy supply in Japan is not one-sided in electricity because the proportion of thermal energy (cooling, heating, and hot-water supply) is 55% in all energy demand of residential sector. [1] is high-value energy. On the other hand, thermal energy of residential-sector demand is low-value energy. That means supplying thermal energy by electricity is not always necessary and the energy system in Japan has a great potential to be improved. We are studying from a viewpoint of energy utilization. A high efficient hybrid solar panel, a cooling equipment using solar thermal energy, and high-performance ejector refrigerating cycle, as well as a software for estimating energy consumption of residential houses from dwellers behavior, an idea of eco-friendly interface space between buildings and natural environment, and Cluster Energy Management System (CEMS) for a new energy utilization system are under study in our group. Based on above studies, we take up Kamaishi-city located in a bay of East Japan as a case of reconstruction from a viewpoint of safe and eco-friendly community with an energy supply including solar-energy utilization. 2. CLUSTER ENERGY MANAGEMENT SYSTEM (CEMS) Our study group has proposed a system constructed from a viewpoint of energy utilization, which we call CEMS. CEMS can build some win-win relationships in energy interchange among various types of energy demanders. One of them is a relationship in a couple of thermal energy and electricity rich demanders because a possibility of jointly having co-generation system. The other of them is a relationship between energy demanders whose energy demand time is different from each other because a possibility to get closer in an operation of facilities under a constant load. Finding a win-win relationship from CEMS concept, we can make it possible to utilize primary energy with higher efficiency, e.g. by using co-generation systems and to utilize energy facilities with higher operation-rate. From a viewpoint of energy value, the exergy of electricity is the largest nearly 1 %, and that of thermal energy depends on the temperature difference from the ambient temperature. It means that thermal energy has different value depending on the temperature as shown in 1

2 Energy demand Exergy [MJ] Figure. 1. Because the temperature difference from the ambient temperature of hot-water, heating and cooling is relatively small, the exergy of those heats is not large. Therefore, supplying to thermal energy demand by electricity is needed to be carefully treated from a viewpoint of exergy. 1 is placed on-site. Remaining electricity generated by can be transmitted to large electricity demander such as offices and schools. University Office 8 Energy: 1 MJ ambient temperture: 15 Hospital (15 ) (9 ) (4 ) (22 ) Fig. 1: Exergy of thermal energy at different temperature. The characteristics of thermal energy and electricity are shown in Table 1, which should be considered in designing an energy supply. TABLE 1: CHARACTERISTICS OF ELECTRICITY AND THERMAL ENERGY Transportation Storing is easy to transport over a long distance with little transmission loss, but storing electricity has many difficulties that battery is expensive and it needs an ample space to store large amount of electricity. On the other hand, thermal energy can be stored much easier by using storage tank, but thermal energy transportation has a lot of heat loss and it needs pumping power of electricity, high-value energy, to supply hot-water or chilled water. In the other words, thermal transportation is not rational from an aspect of the energy value. Effective utilization of thermal energy would be on-site, not be transported over long distance, and electricity can be transported while residual electricity could be transported to other demanders instead of storing on-site. Storing thermal energy compensates the time variance of thermal demand, and transmitting electricity to other demanders makes more freedom in operation of co-generation systems (). From an above viewpoint, a win-win relationship among energy demanders whose energy-demand time is different would be possible to be found. As shown in Figure 2, is installed near large thermal energy demander such as hospital, hotel and supermarket, etc. demand of those facilities is supplied from the exhaust heat of, which Office Exhaust heat Office Fig. 2: Win-win relationship among different demanders. Energy peak in demand should be avoided by a win-win relationship among those demanders, while the demand in any demander should be assessed from a viewpoint of exergy to effectively utilize primary energy resources. The energy system would be a base of developing safe and eco-friendly cities from a viewpoint of energy utilization. Figure. 3 shows an energy demand of a cluster consists of residential houses and officies, which demand would become more flat than each demander. The energy peaks of residential houses exist in the morning and evening. On the other hand, energy demand of office would have a peak in day time. By combining those demands, which is a kind of cluster, the total energy demand becomes flat. The energy-supply facilities can be used with higher operation-rate. Time Fig. 3: Energy demand of a cluster with a win-win relationship by a couple of different demanders. In addition, the peak load becomes closer to the average load when we can find good couplings, which makes appropriate capacity of energy-supply facility can be installed. It might be another important merit of CEMS. 3. ESTIMATION OF ENERGY DEMAND IN RESIDENTIAL SECTOR High school Combined energy demand Energy demand of residential Energy demand of office To construct CEMS, it is needed to grasp the actual energy demand of residential sector which fluctuates 2

3 Staying home rate of 4's male worker [%] Energy demand [MJ] irregularly at different time, day, weather, etc. Estimating energy demand of each household is not easy when we need a time function of demands reflecting dwellers behaviors. It relates various factors such as climates, dwelling performances, family configuration, life-stages of dwellers, and performance of appliances, so on. Our study group develops software, which can estimate energy demand and consumption of each household based on behavior of dwellers. Figure 4 is the estimation flow process of this estimation. This software can replicate the dynamic behavior schedules of each dweller and estimate the energy demand at each moment. Total energy demand is estimated by accumulating the demand at each moment. This software can also reflect the influence of climates and performance of appliances on the demand. Determination of family members, dwelling performance, appliances and the performance etc. Calculation of dynamic behavior of dwellers by Monte Carlo random number generation based on various statistics. Estmation of energy consumption at each time and day with weather information Fig. 4: Energy estimation flow of our software. 3.1 Creating dwellers dynamic behavior Generally, energy demand is estimated by allocating annual energy consumption to each time using burden rate with degree-day method. In this way, we can get one average energy demand model whose schedule is only one set not for everyday and not for different families. With this method, the energy demand for a group of dwellers cannot be correctly estimate because all the dwellers have never repeated exactly the same schedule every day : 3: 6: 9: 12: 15: 18: 21: 24: NHK's statistics Time Replicated behavior schedule Our system can calculate each dweller s dynamic or different behavior at each time on each day and estimate energy demand at each moment on the basis of various statistics and weather etc. with statistical randomness. The behavior model of dwellers is mainly based on the NHK national living activities research [2]. Figure 5 shows the action staying home of 4s male worker as an example of dynamic behavior schedule. 3.2 Estimating energy demand and consumption Energy demand is estimated on the basis of the replicated behavior schedule by Monte Carlo method. Energy demand is classified into hot-water demand, heating, cooling, cooking, and non-thermal energy demand, which is possible to supply only electricity. Hot-water demand is allocated by the behavior for taking bath, washing one s face, cleaning dishes. We set the usage temperature and amount of hot-water for each purpose, and estimate a hot-water demand by considering the temperature of tap water. Cooking demand is estimated from the family size. ing and cooling demand is estimated from heat loss coefficient of house and the temperature difference between inside and outside of house. On-off judgments for appliances are requested in the tags for staying room of the behavior schedule. Non-thermal energy demand is electrical demand such as lighting, electrical appliances except those for heating, cooling, and hot-water supply. Lighting demand is estimated from staying room tag and amount of insolation Hot-water Cooling Cooking : 3: 6: 9: 12: 15: 18: 21: : Time Fig. 6: Estimated energy-demand of 3 households on a certain summer day. In this operation, each energy demand based on dynamic behavior of dwellers is estimated. Figure 6 is the estimated energy demand of 3 households on a certain day in summer. Fig. 5 Statistics of a staying home for 4s male worker. 3

4 Fig. 7: Reconstruction image of Kamaishi-city. 4. TOHOKU RECONSTRUCTION DESIGN We took up Kamaishi-city as an example of a model city of reconstruction. Kamaishi-city is a coastal city whose population is about 4, and the infrastructure was devastated by the disaster. Therefore, we proposed a concentrated community where the infrastructure can be mounted. The area is within 15minutes-walk, about 1 km radius and the center of the area, an artificial hill is assumed where citizens can be safe from both earthquake and tsunami. In each community, the population of 5 people and normally 2,5 people in 1, households can live on an artificial hill (the Hill) and other 2,5 people can live around the Hill. Eight communities are necessary in Kamaishi-city for 4, populations. A kind of safe and eco-friendly community will be designed from a viewpoint of energy utilization based on CEMS. Fig. 9: Web network of communities. 4.1 Safe and Eco-friendly Community in Kamaishi-city We simulated energy supply based on CEMS concept with introduction of solar-utilization panels. Solar thermal energy should be used for supplying thermal energy demand of the community. The solar thermal panel is placed on the Hill and on the roof of each detached houses around the Hill. welfare facility school solar panel parking office dwelling Fig. 8: Image of an artificial hill, the Hill. station We estimated thermal energy demand for hot-water supply, heating, and cooling and electricity by using our software of Monte Carlo simulation. The area of solar thermal panel (solar panel) was used as a parameter of the calculation. The amount of solar thermal energy based on the insolation was calculated. The solar thermal energy collected on the Hill was assumed to be used only by residents on the Hill and the solar thermal energy collected on the roof of each detached houses was assumed to be used only by residents in each detached houses. is also considered to supply thermal energy demand on the Hill. We operated the at a constant rated load and the exhaust heat was used to supply the thermal demand on the Hill. The remained electricity generated by the can be transmitted to the detached houses or another Hill. Remained collected solar thermal energy and/or exhaust heat of the can be stored in heat storage tank and to be used on-site at different time. Figure 1 shows the outline of energy supply. 4

5 at the Hill Energy demand Energy supply Secondary energy consumption around the Hill Energy demand Energy supply Secondary energy consumption Solar thermal Fig. 1: Outline of energy supply in a community. An advanced thermal energy utilization of the good combination of thermal energy sources, solar thermal energy,, and heat pump are effectively used as well as the electricity supply can be provided by rated-load operation of the is recommended for the efficient utilization of primary energy resources. 4.2 Energy supply system exhaust heat gas consumption Solar heat other than solar other than solar from outside We assumed four different cases of solar thermal panel areas for the Hill, 1, m 2, 2, m 2, 3, m 2, and 4,m 2. And we also assumed the panel area of detached houses as being 7.64 m 2 of four panels because each panel has 1.91 m 2. A capacity is determined as a function of the amount of solar thermal energy and demand as well as an auxiliary heat produced by heat pump system. We compared the calculation results of energy-supply balance of the systems 1, 3, 5, and 7 in Figure 11 and 12 under the assumptions in Table 2 and 3. The amount of collected solar thermal energy increases in proportional to panel area. Simultaneously, capacity becomes smaller, that automatically makes the exhaust heat and power from the also to be smaller. Therefore, electricity supply from outside increases, which can be replaced by photovoltaic cells and/or the transmitted power from the Hill. On the fact described above, the capacity of is getting smaller with increasing solar thermal panel area. It means energy consumption of can be reduced. However, the electricity supply to the Hill from outside increase because power generation from is also reduced. On the other hand, transmitted power from the Hill also automatically reduces and the electricity supply to the houses around the Hill from outside also increases. 4.3 Environmental load and peak power load by from outside Transmitted Transmitted power from outside TABLE 2: ASSUMPTION CONDITION OF EACH SYSTEM Solar panel efficiency 6 % Temperature from solar panel 7 Efficiency of data of each device Temperature from 9 ing system and panel heating, radiation Cooling system Absorption chiller and panel cooling, radiation TABLE 3: SIMULATION CONDITIONS OF EACH SYSTEM Area of solar thermal panel [m 2 ] operation time [h] for the Hill for detached houses Sys. 1 1, (9-23) Sys. 2 1, (6-22) Sys. 3 2, (9-23) Sys. 4 2, (6-22) Sys. 5 3, (9-23) Sys. 6 3, (6-22) Sys. 7 4, (9-23) Sys. 8 4, (6-22) Energy demand System1 System3 System5 System7 5, 1, 15, 2, 25, 3, Fig. 11: Energy supply for the Hill by systems of 1, 3, 5, or 7. Energy demand System1 System3 System5 System7 Energy demand [GJ] Energy supply [GJ] Energy demand [GJ] 1, 2, 3, 4, 5, Energy supply [GJ] Solar thermal Exhaust heat of sub-hp Power from outside Power by Transmitted power Power Solar thermal other than solar Transmitted power Power from outside Power Fig. 12: Energy supply for buildings around Hill by systems 1, 3, 5, or 7. 5

6 Primary energy consumption [GJ] CO 2 emission [t] We evaluate the environmental load and peak power of all the seven systems. Figure 13 shows the primary energy consumption and peak power of each system. 16, 14, 12, 1, 8, 6, 4, 2, Existing Sys.1 Sys.2 Sys.3 Sys.4 Sys.5 Sys.6 Sys.7 Sys.8 Hot-water ing Cooling &Cooking sub-hp Peak power 4, 3,5 3, 2,5 2, 1,5 1, Fig. 13: Primary energy consumption and peak power of each systems Primary energy consumption of hot-water supply, heating, and cooling is reduced drastically by 48% in maximum case without than that of conventional energy supply. On the other hand, primary energy consumption by accrues. From comparison among the systems, energy consumption of can be reduced with installing solar thermal panels. However, electricity production by is also reduced by increasing the solar panels. Therefore, there is not a great difference of primary energy consumption by installing the solar thermal panels. Primary energy consumption could be cut by about 3 % in systems 1 to 7 by introducing. Peak power of each system becomes less than a half of existing system. By comparing among the systems, peak power is in proportional to the operation time of. Primary energy consumption of increases with increasing operation time, however, entire primary energy consumption does not increase and the peak power is reduced. Peak power load could be cut by up to 6% in system 4 from that of existing system. Concerning the CO 2 emission, some similar tendencies as that for primary energy consumption can be seen as in Fig. 14. The CO 2 emission of hot-water supply, heating, and cooling, is reduced by 58% in the maximum case of using solar thermal and electricity energy without. However, the CO 2 emission by accrues simultaneously from the calculations in the present systems. When solar thermal panel area becomes smaller, the CO 2 emission increases due to operating more and/or consuming electricity outside. By comparing among the systems, there is not great difference in the CO 2 emission by the different area of solar thermal panels. Those systems can reduce CO 2 emission about 22% from the existing one. 5 Peak power [kw] 8, 7, 6, 5, 4, 3, 2, 1, Existing Sys.1 Sys.2 Sys.3 Sys.4 Sys.5 Sys.6 Sys.7 Sys.8 Hot-water Cooling sub-hp Fig. 14: CO 2 emission of each systems 5. CONCLUSION For establishing a safe and eco-friendly community, i.e., a solar community, CEMS concept was applied to the energy system of reconstruction in Kamaishi-city. There is a possibility of about 3% reduction in primary energy consumption and about 2% reduction in CO 2 emission by introducing an advanced thermal energy utilization including the introduction of solar thermal panels. It is also obtained that there is a possibility of about 6% peak power load reduction. On the other hand, those reductions are less influenced by the difference in the area of solar thermal panels. To achieve more eco-friendly community, from viewpoints of reducing the primary-energy consumption and CO 2 emission, we need to install not only solar thermal panels but also solar photovoltaic cells. Hybrid solar panel is one of the alternative options for saving the area of solar panels. In this paper, we discussed about only dwellings, but in the future we need to consider other clusters such as a combination of hospital with school or a couple of dwelling and office buildings to get the win-win relationship, which makes possibility to construct more safe and eco-friendly community through the CEMS concept. 6. REFERENCES ing &Cooking [1] Resources and Energy Agency, Annual report on energy for 29 (Energy survey 29), html/index29.htm, 21 [2] NHK Broadcasting Culture Research Institute, Data book NHK national living activities research 25, Japan Broadcast Publishing Co., Ltd., 26 6