• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3307-3314
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• 2012

The annual energy demand of the standard rural house models was analyzed using the DesignBuilder. Indoor temperature set-point, U-value of outer wall, type of window, and degree of ventilation were selected as simulation parameters. In all the simulation cases, heating energy demand was higher than cooling energy demand regardless of the building size. When the lower U-value of the outer wall was applied to account for the thicker insulation layer, heating energy demand was decreased while cooling energy demand was increased. However, it is better to reduce the area of outer wall which is directly exposed to outdoor air because reducing the U-value of the outer wall is not effective in decreasing heating energy demand. Among the four different window types, the double skin window is most favorable because heating energy demand is the lowest. For a fixed infiltration rate, higher ventilation rate resulted in an increased heating energy demand and had minor impact on cooling energy demand. As long as the indoor air quality is acceptable, lower ventilation rate is favorable to reduce the annual energy demand.

• The Journal of Engineering Geology
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• v.25 no.4
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• pp.599-612
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• 2015

The development of renewable energy technologies that can replace fossil fuels is environmentally important; however, such technologies must be economically feasible. Economic analyses are important for assessing new projects such as geothermal heating-cooling systems, given their large initial costs. This study analyzed the economics and carbon dioxide emissions of: a SCW (standing column well), a vertical closed loop boiler, a gas boiler, and an oil boiler. Life cycle cost analysis showed that the SCW geothermal heating-cooling system had the highest economic feasibility, as it had the highest cost saving and also the lowest carbon dioxide emissions. Overall, it appears that geothermal systems can save money when applied to large-scale controlled agriculture complexes and reclaimed land.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.120-120
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• 2010

에너지 절약적 차원에서 한 대의 실외기에 다수의 실내기가 접속되는 개별공조형 멀티 열펌프에 관한 연구 및 개발과 보급이 증대되고 있다. 본 연구에서는 복수의 실내기를 갖고 가변속 압축기를 채용한 지열원 물대공기 멀티열펌프시스템을 학교 현장에 설치하여 제조사의 운전 제어 알고리즘에 따라 일일 냉난방 실증 성능 특성을 분석하였다. 2008년 9월 30일의 냉방부하가 낮은 일자에 대하여 시간에 따른 부하 변동에 따라 압축기의 용량가변으로 실내기 냉방용량은 정격용량 대비 17.1%에서 111.3%의 범위에서 변이되었으나, 열펌프 유닛의 일일 최대 COP는 6.2를 나타냈으며, 일일 평균 열펌프 유닛 COP는 4.5로 열펌프 유닛 인증 기준 이상의 성능을 나타냈다. 2008년 11월 10일 대비 2008년 12월 15일에는 시스템 가동 중의 평균 외기온도가 $9.6^{\circ}C$ 감소하였으나, 각 재실공간의 용도별 부분 부하특성으로 11월 10일 보다 난방 부하량이 작게 나타났다. 하지만, 12월 15일에는 부하량이 매우 작아서 11월 10일보다 잦은 압축기 가변에 따른 손실로 일일 평균 COP가 낮게 나타났다. 2009년 1월 12일에는 정격 용량대비 94%의 부하율로 11월 10일과 12월 15일 대비 4배 이상의 부하량으로 압축기 용량 가변율이 작아서 난방용량과 COP 변화율이 작게 나타났다. 2009년 1월 12일에는 지중순환수의 실외열교환기 유입온도가 2008년 12월 15일보다 감소하고, 시스템의 난방용량 증가로 상대적으로 응축기와 증발기 크기가 감소한 효과로 히트펌프 유닛 COP가 감소하였으나, 본 지열원 열펌프 제조사에서 생산하고 있는 본 지열원 시스템과 동일한 압축기 등을 채용한 동일 용량의 공기열원 열펌프의 1월 12일 외기온도 $-10^{\circ}C$에서의 열펌프 유닛 COP 대비 70% 우수한 성능을 나타냈다. 본 지열원 히트펌프의 2008년 11월 10일의 일일 평균 히트펌프 유닛 COP는 외기온도가 낮고 일일 부하량이 크게 나타난 1월 12일의 일일 평균 히트펌프 유닛 COP 대비 37% 높게 나타났으나, 지중순환펌프의 정속운전으로 시스템 요구 지중순환수 유량 증가에 따른 성능 향상보다 소비전력 증가 영향이 커서 1월 12일의 시스템 COP 보다 33.3% 작은 값을 나타냈다. 본 연구의 용량 가변형 압축기를 채용한 지열원 멀티 히트펌프 유닛을 지열원 냉난방 시스템의 히트펌프 유닛으로 사용할 경우 시스템 최적화를 통한 시스템 COP 향상과 연간에너지 절감을 이루기 위해서는 히트펌프의 용량 변화 시에 지중순환펌프의 순환 유량 최적화를 위한 효율적 운전 제어 알고리즘 개발이 요구된다.

• KIEAE Journal
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• v.13 no.2
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• pp.21-26
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• 2013

Due to the increasing concerns about the buildings which have affected the global environment, most countries have enacted a regulation for the sustainability of domestic buildings. In 2008, the Korean government started to enact a regulation of apartment and office buildings for energy saving. Many research on the sustainable apartment building focuses on $84m^2$ or larger type in response to market demand; therefore, small size type such as $46m^2$ type needs to be researched. In addition, the research on the orientation and window to wall ratio of the building have been separately studied as a means of energy reduction; therefore, the research on correlation of the orientation and window to wall ratio hasn't been fully explored yet. This paper analyzes the energy demand of the apartment building as the change of orientation and window to wall ratio among $46m^2$ and $84m^2$ type. In conclusion, when reducing the window to wall ratio, energy demand was reduced, except when the orientation of the building was between from +10 to -20 from the south.

• Journal of the Korean Institute of Landscape Architecture
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• v.42 no.1
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• pp.41-49
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• 2014

This study spatially assesses the impact of trees on residential rooftop solar energy potential using urban three-dimensional models derived from Light Detection and Ranging(LiDAR) data in San Francisco, California. In recent years on-site solar energy generation in cities has become an essential agenda in municipal climate action plans. However, it can be limited by neighboring environments such as shade from topography, buildings and trees. Of all these effects, the impact of trees on rooftop photovoltaics(PVs) requires careful attention because improper situation of solar panels without considering trees can result in inefficient solar energy generation, tree removal, and/or increasing building energy demand and urban heat island effect. Using ArcMap 9.3.1, we calculated the incoming annual solar radiation on individual rooftops in San Francisco and the reduced insolation affected by trees. Furthermore, we performed a multiple regression analysis to see what attributes of trees in a neighborhood(tree density, tree heights, and the variance of tree heights) affect rooftop insolation. The result shows that annual total residential rooftops insolation in San Francisco is 18,326,671 MWh and annual total light-loss reduction caused by trees is 326,406 MWh, which is about 1.78%. The annual insolation shows a wide range of values from $34.4kWh/m^2/year$ to $1,348.4kWh/m^2/year$. The result spatially maps the locations that show the various levels of impact from trees. The result from multiple regression shows that tree density, average tree heights and the variation of tree heights in a neighborhood have statistically significant effects on the rooftop solar potential. The results can be linked to municipal energy planning in order to manage potential conflicts as cities with low to medium population density begin implementing on-site solar energy generation. Rooftop solar energy generation makes the best contribution towards achieving sustainability when PVs are optimally located while pursuing the preservation of urban trees.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1540-1547
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• 2013

The energy economic analysis of the standard rural house model with PV system was performed based on annual energy demand calculation using the EnergyPlus to contribute in reducing building energy which occupies 25% of national energy consumption and in developing a low-energy & eco-friendly house model. Two types of PV system installation was considered to cover electricity demand for cooling, electric, and heating devices. For the selected house model, heating energy demand is 7 times higher than cooling energy demand. For the Case1, it is favorable to use electricity from PV system for cooling and electric devices and to sell surplus electricity. For the Case2, it is favorable to use electricity from PV system for cooling, electricity and heating devices and to sell surplus electricity. Considering the installation cost of PV system and heat pump air conditioning system, the break-even point of Case1 and Case2 are about 13 and 11 years respectively. Although the installation cost of Case2 is more expensive, Case2 provides three times more profit than Case1 after the break-even point. Because the expected average life time of the selected PV system is 25 years, Case2 is more favorable option for the given standard rural house model.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.30 no.4
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• pp.159-166
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• 2018

The Korean fenestration energy consumption efficiency rating system only considers thermal performance of the heat transfer coefficient (U-value) and airtightness excluding optical characteristics of the solar heat gain coefficient (SHGC). This study analyzed annual heating and cooling energy requirements on the middle floor of apartment by optical and thermal performance of windows to evaluate the suitability of the rating system. One hundred and twenty-eight windows were analyzed using THERM and WINDOW 7.4, and energy simulation for a reference model of an apartment house facing south was performed using TRNSYS 17. The results showed that window performance was the main factor in the heating and cooling load. The heating load of the reference model was 539 kWh to 2,022 kW, and the cooling load was 376 kWh to 1,443 kWh. The coefficient of determination ($R^2$) of the heating and cooling loads driven from the SHGC were 0.7437 and 0.9869, which are more compatible than those from the U-value, 0.0558 and 0.4781. Therefore, it is not reasonable to evaluate the energy performance of windows using only the U-value, and the Korean fenestration energy consumption efficiency rating system requires a new evaluation standard, including SHGC.