Vol.3 No.3 2010

Research paper : An optimum design method utilizing a strategic system design concept (J. Fukuda et al.)−192−Synthesiology - English edition Vol.3 No.3 (2010) of a strategic system design, a composite datacenter that combines the datacenter and agriculture is designed to review the effectiveness quantitatively.First, a datacenter seen from the physical aspect is considered. Looking at the energy flow of the datacenter in Fig. 1, most of the energy is emitted from the datacenter as heat. The electricity consumed by the CPU for computation is less than 1 % of the overall energy.A more efficient system can be proposed by combining the business and system for reusing the waste heat from the datacenter (Fig. 5). The businesses that may reuse waste heat include: cooling/heating and hot water supply in offices, residences, and hospitals; warm water supply for bath, pool, and plants; and heating for greenhouse farming. In heating for greenhouse farming, the required temperature is relatively low, the time change for heat demand is relatively stable, and the waste heat from the datacenter that serves as a low-temperature heat source can be used directly in the form of warm air. Therefore, this system is a likely candidate for adoption by a business that employs waste heat from the datacenter. Also, the farmer can see a direct benefit because the majority of the cost of greenhouse farming during winter is dominated by heating fuel cost (Fig. 6).An estimate is carried out for the effects of reductions in fuel cost and CO2 emissions, assuming the greenhouse heating using waste heat from the datacenter in the Utsunomiya area, which is a relatively cold area and is within the supply region of the Tokyo Electric Power Company that is a power company with least CO2 emission coefficient in Japan.The assumed model datacenter has a maximum capacity of 1,000 racks (actual operation rate 85 %) with a maximum power supply of 6 kW/rack (average 4.2 kW/rack). It is assumed that the waste heat from the air conditioners of the datacenter will be used for heating a greenhouse, and the necessary amount of heat needed to heat the greenhouse to 15 °C or higher during the winter period from October 1 to May 31 is calculated. As a result of the estimation, the amount of heat generation from the datacenter reaches 566,300 MJ/day, and this corresponds to combustion of 12.6 kL/day of kerosene. Even considering the reduction of heating efficiency, this amount is capable of heating a greenhouse of 88,100 m2 size during the midwinter period (Table 3)Note 5).This will allow a reduction of cost needed for greenhouse heating by about 190 million yen per year, and CO2 will be reduced by 4,256 t per year. This corresponds to 21.9 % of CO2 emitted by the datacenter, and the combination of the datacenter and the greenhouse will have a CO2 reduction effect of 17.9 % (Table 3). Dramatic reduction in CO2emissions can be expected by compositing the datacenter and the greenhouse.4.2 Total value system design for a composite datacenter through strategic system designUnless the two stakeholders, the datacenter company and the greenhouse farmer, accept the values (stakes), it is not possible to realize optimization by achieving the physical system. Therefore, we shall investigate the value design of the composite system of the datacenter and the greenhouse.4.2.1 Condition when the datacenter alone invests in environmental measuresThe profit of datacenter company is set as P0, the sales of service is S, and the energy cost is EC. It is assumed that an environment tax (TC) is introduced by the social system that attempts to control the CO2 emissions of the energy consumption. The company makes an environment measure investment (IC) such as introducing efficient air conditioning to minimize profit reduction, and attempts to reduce the energy cost and environment cost. Here, the condition under which the environment measure investment IC is conducted is when the sum of reduced energy cost EC2 and the reduced environment tax TC2 is higher than the investment IC, as Fig. 5 Energy flow of the composite datacenterTable 3 Reduction in CO2 emission by a composite datacenter566,308m2MJ/dayWaste heat from entire datacenter (Utsunomiya)1,709kL/yearReduction in heating fuel (kerosene)189,7341,000 yenCost reduction of heating fuel4,256t-CO2Reduction in CO2 emission by reduction of heating fuel19,464t-CO2CO2 emission from datacenter-21.9 %%Rate of reduction of CO2 emission seen from datacenter-17.9 %%Rate of reduction of CO2 emission of datacenter + greenhouseSurface area of greenhouse88,100Other service companies・Heating for buildings and residences・Heated pool and bath facility・Heat source of natural gas transport facility・Heating for greenhouse farming, etc.UserCommunicationcompanyDatacenter companyPowerplantPowersupplyUninterruptiblepower deviceServerEmergencygeneratorNetworkservicePCWasteheatAirconditioningdeviceReuse ofwasteheatNewproductsandservicesElectricpowercompanyFig. 6 Use of waste heat from datacenter in farmingWaste heatfrom serverDatacenterWaste heat from power supply facilityAirconditionerHeat is released into atmosphere during summerWaste heat is used for heating greenhouse during winterGreenhouse farming


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