1882 † To whom correspondence should be addressed. E-mail: taeahn@skku.edu Korean J. Chem. Eng., 30(10), 1882-1888 (2013) DOI: 10.1007/s11814-013-0121-9 INVITED REVIEW PAPER 2D representation of life cycle greenhouse gas emission and life cycle cost of energy conversion for various energy resources Heetae Kim*, Claudio Tenreiro* , **, and Tae Kyu Ahn* ,† *Department of Energy Science, Sungkyunkwan University, 300, Cheoncheon-dong, Jangan-gu, Suwon, Gyeonggi-do 440-746, Korea **Faculty of Engineering, Universidad de Talca, 2 Norte 685, Talca, Chile (Received 16 April 2013 • accepted 7 July 2013) Abstract -We suggest a 2D-plot representation combined with life cycle greenhouse gas (GHG) emissions and life cycle cost for various energy conversion technologies. In general, life cycle assessment (LCA) not only analyzes at the use phase of a specific technology, but also covers widely related processes of before and after its use. We use life cycle GHG emissions and life cycle cost (LCC) to compare the energy conversion process for eight resources such as coal, natural gas, nuclear power, hydro power, geothermal power, wind power, solar thermal power, and solar photo- voltaic (PV) power based on the reported LCA and LCC data. Among the eight sources, solar PV and nuclear power exhibit the highest and the lowest LCCs, respectively. On the other hand, coal and wind power locate the highest and the lowest life cycle GHG emissions. In addition, we used the 2D plot to show the life cycle performance of GHG emis- sions and LCCs simultaneously and realized a correlation that life cycle GHG emission is largely inversely proportional to the corresponding LCCs. It means that an expensive energy source with high LCC tends to have low life cycle GHG emissions, or is environmental friendly. For future study, we will measure the technological maturity of the energy sources to determine the direction of the specific technology development based on the 2D plot of LCCs versus life cycle GHG emissions. Key words: 2D Projection, Life Cycle Analysis (LCA), Life Cycle Cost (LCC), Electricity Conversion, Coal, Natural Gas, Nuclear Power, Hydro Power, Geothermal Power, Wind Power, Solar Thermal Power, Solar Panel INTRODUCTION There is a general consensus that worldwide energy consumption is growing, and our energy system is moving gradually towards an electricity-centered system. In 2006 the total energy consumption in the world was 11,730 Mtoe, and we expect that energy demand will increase by an average of 1.6 % every year by 2,030 [1]. A sig- nificant percentage of greenhouse gas (GHG) emissions comes from fossil-based energies and has resulted in anthropogenic climate change [2]. To mitigate environmental impact and to improve convenience of daily life, new technologies have been developed, such as elec- tric vehicles. But these technologies consume electricity as the main energy source. In fact, worldwide electricity consumption reached 15,665 TWh in 2006, and it is expected to increase up to 20,760 TWh in 2015 and 28,140 TWh in 2030 [1]. At last, post-carbon energy system is shifting to electricity-centered energy system. To design an electricity-based energy system, analysis and re- search on energy technologies that produce electricity are quite cru- cial. To support national governments in energy policy making and to assist individual or industrial consumers in choosing appropriate energy source, the life cycle environmental impact of each option should provide with corresponding life cycle cost (LCC). Consumers have become concerned not only about the affordability of prod- ucts, but also the environmental conservation perspective. Reports said they are willing to pay up to 20% more for using sustainable products, so called LOHAS [3]. The consumer trend is reflected in the electricity market as well and electricity power is considered as a product rather than a part of infrastructure systems controlled by the government. Currently, the government determines national elec- tricity generation mix and all consumers can do is to follow it. How- ever, once smart grid systems soon are introduced, an electricity consumer will be able to decide his or her own electricity mix and then buy the electric power from a local electricity distribution com- pany. In the electric power market, consumers need typical infor- mation of the comparison of environmental impact with its cost of electricity generation sources. Also, national governments require data in order to formulate energy policies. Intuitive and holistic data analy- sis, which enables us to make a decision at a glance, is needed for designing future energy systems. Life cycle assessment (LCA) estimates the environmental impact of a product or a service through its supply chain. The concept of LCA was created in the 1960s for the purpose of estimating the ex- ternal environmental impacts. Its principle and framework was codi- fied as the ISO standard in 1997 and the methodological require- ments and the guidelines were established in 2006 [4]. In addition, the United Nations Environmental Program (UNEP) and Society of Environmental Toxicology and Chemistry of the U.S. (SETAC) jointly proposed an UNEP/SETAC Life cycle Initiative in 2000 to actively utilize LCA in assessing environmental impacts. Because LCA examines the total impact of an entire system, it is widely used in assessing GHG emissions and calculating carbon footprints by