energies Article Environmental and Efficiency Analysis of Simulated Application of the Solid Oxide Fuel Cell Co-Generation System in a Dormitory Building Han Chang * and In-Hee Lee * Department of Architecture, Pusan National University, Busan 46241, Korea * Correspondence: [email protected] (H.C.); [email protected] (I.-H.L.) Received: 23 August 2019; Accepted: 11 October 2019; Published: 15 October 2019 Abstract: The problem of air pollution in Korea has become progressively more serious in recent years. Since electricity is advertised as clean energy, some newly developed buildings in Korea are using only electricity for all energy needs. In this research, the annual amount of air pollution attributable to energy under the traditional method in a dormitory building, which is supplying both natural gas and electricity to the building, was compared with the annual amount of air pollution attributable to supplying only electricity. The results showed that the building using only electricity emits much more air pollution than the building using electricity and natural gas together. Under the traditional method of energy supply, a residential solid oxide fuel cell cogeneration system (SOFC–CGS) for minimizing environmental pollution of the building was simulated. Furthermore, as a high load factor could lead to high efficiency of the SOFC–CGS, sharing of the SOFC–CGS by multi-households could increase its efficiency. Finally, the environmental pollution from using one system in one household was compared with that from sharing one system by multi-households. The results showed that the environmental pollution from sharing the system was relatively higher but still similar to that when using one system in one household. Keywords: environmental impact; device efficiency; air pollutant; multi-households; solid oxide fuel cell cogeneration system 1. Introduction 1.1. Research Background Electricity as non-combusted energy is advertised to the public as clean energy. Since the price of natural gas and the price of electricity for residential use are similar [1], in the areas of architecture and construction, some real estate developers have been developing new buildings using only electricity for power. However, as a secondary energy resource, electricity is either clean or not clean depending on the electricity generation procedure. In Korea, 39% of electricity is generated from burning coal and only 4% is generated from renewable resources as seen in Figure1[2]. Energies 2019, 12, 3893; doi:10.3390/en12203893 www.mdpi.com/journal/energies Energies 2019, 12, 3893 2 of 20 Energies 2019, 12, x FOR PEER REVIEW 2 of 20 6% 1% 4% Electricity generation by using nuclear energy 31% Electricity generation by combusting coal 19% Electricity generation by using LNG Electricity generation by using renewable resources Electricity generation by other fuel resources Electricity generation by hydraulic power 39% Figure 1. Electricity generation system in Korea. The traditional methodmethod ofof supplyingsupplying energy energy to to a a building building in in Korea Korea is mainlyis mainly using using natural natural gas gas for forheating heating and and hot hot water water and and using using electricity electricity for for lighting, lighting, cooling, cooling, and and equipment. equipment. AA recentrecent method of supplying energy to a building is using only electricity for all energy needsneeds inin thethe building.building. This research compared the annual amount of air pollution attributable to energy under the traditional method in a dormitory building, which is supplying both natural gas and electricity to the building and the annual amount of air pollution attributable to supplying only electricity.electricity. A solid oxide fuel cell (SOFC) is a clean energy devicedevice for generatinggenerating electricity by consuming hydrogen or natural gas. By By utilizing utilizing chemical chemical interaction interaction in in the the cell cell stack during the process of electricity generation in SOFC, there is no environm environmentalental pollution. However, there is a large amount of heat dissipation during SOFC operation. In In order order to to improve the efficiency efficiency of SOFC, the SOFC cogeneration system (SOFC–CGS) waswas developeddeveloped toto collectcollect andand useuse the heat loss. The heat heat dissipation dissipation generated from SOFC is collected by residential SOFC–CGS and supplied to a hot water tank for hot water demand of a household. A fuel cell as a clean energy system is widely studied for residential use. In In recent recent years, years, various various researches researches were were done done about about optimizing optimizing the theoperation operation efficiency efficiency of a offuel a cell.fuel cell.Some Some scholars scholars proposed proposed efficiency efficiency optimiza optimizationtion methods methods of ofa afuel fuel cell cell through through improving working principles of electronicelectronic components.components. Wa Wangng et al. proposed proposed a a novel stack and converter interpreted design scheme to improveimprove thethe converterconverter eefficiencyfficiency [[3].3]. A micromicro tri-generation system could increase the system eefficiencyfficiency toto overover 90%90% [[4].4]. An energy management system could also achieve cost cost reduction, reduction, CO CO2 2mitigation,mitigation, and and energy energy consumption consumption [5]. [ 5Some]. Some scholars scholars aim aimto find to finda way a wayto improve to improve the efficiency the efficiency of a fuel of a cell fuel from cell fromanalysis analysis of energy of energy demand, demand, energy energy distribution, distribution, and energyand energy supplication supplication of a offuel a fuelcell. cell.Adam Adam et al. et pr al.esents presents a multi-objective a multi-objective modeling modeling approach approach that allowsthat allows an optimized an optimized design design of micro-combined of micro-combined heat heat and and power power (CHP) (CHP) systems systems considering considering the source, distribution and emission requirements in un unisonison to to achieve achieve more more efficient efficient whole whole systems systems [6]. [6]. Coordination between utilizationutilization factorfactor ofof SOFCSOFC andand featuresfeatures ofof aa DCDC/AC/AC (Direct(Direct current current//AlternatingAlternating currentcurrent)) inverter inverter is is also also an an efficient efficient control control strategy for SOFC operation [[7].7]. Some researchers have combined a photovoltaic, battery, battery, or heat pump wi withth a fuel cell to satisfy the energy needs by a household while reducing cost and CO2 emission [8–10]. [8–10]. From From a a wi widerder energy supply perspective, SOFC was considered toto supplysupply energyenergy forfor bothboth householdshouseholds and and EV EV (Electric (Electric vehicle)vehicle) to to improve the efficiencyefficiency andand energyenergy supply supply capacity capacity of of SOFC. SOFC. Using Using a hydrogena hydrogen supply supply system system for afor residential a residential fuel fuelcell tocell provide to provide energy energy for fuel for cell fuel vehicles cell vehicles is also ais method also a method to solve theto solve problem the ofproblem lacking of hydrogen lacking hydrogenstations for stations fuel cell for vehicles fuel cell [11 ,12vehicles]. Field [11,12]. experimental Field studiesexperimental demonstrated studies thatdemonstrated a residential that fuel a residentialcell could significantlyfuel cell could reduce significantly the CO2 reduceemissions the andCO2 primaryemissions energy and primary consumption energy [ 13consumption]. Accurate [13].mathematical Accurate modelsmathematical were developed models were to analyze developed the performanceto analyze the of SOFC.performance A 1D dynamicof SOFC. modelA 1D wasdynamic built formodel studying was systembuilt for integration studying and system developing integration adequate and energy developing management adequate and controlenergy managementstrategies of SOFCand control systems strategies [14]. Gallo of SOFC et al. developedsystems [14]. a model Gallo ofet aal. non-conventional developed a model SOFC of systema non- conventionalby applying aSOFC lumped system energy by applying balance toa lumped each component. energy balance This to model each comp couldonent. efficiently This model increase could the efficientlyheat exchanges increase inside the theheat system. exchanges This inside model the is verified system. by This experiments model is verified and applicable by experiments to numerous and applicablelayouts [15 to]. numerous According layouts to reference [15]. According [16], a fuel to cell reference is mainly [16], used a fuel in America,cell is mainly Europe, used South in America, Korea Europe, South Korea and Japan worldwide. From environmental aspect, analysis of CO2 reduction by a fuel cell was also shown in recent researches from Europe, Japan and South Korea. Fuel cell for Energies 2019, 12, x; doi: FOR PEER REVIEW www.mdpi.com/journal/energies Energies 2019, 12, 3893 3 of 20 and Japan worldwide. From environmental aspect, analysis of CO2 reduction by a fuel cell was also shown in recent researches from Europe, Japan and South Korea. Fuel cell for EV is mainly applied and investigated in Korea. Environmental impact of CO2 reduction and emission by fuel cell EV is conducted [17,18]. In order to encourage the utilization residential fuel cell in households in Korea, Lim et al. did a study in the view of CO2 emissions