Carbon Dioxide Emission Reduction With Distributed Generation in Northern California: A Case Study

Worldwide, energy-related carbon dioxide emission is projected to increase from 30.2 billion metric tons in 2008 to 43.2 billion metric tons in 2035 – an increase of 43% over 27 years [1]. The United States’ total carbon dioxide emission in 2008 was 5.84 billion metric tons, which is projected to increase to 6.31 billion metric tons in 2035 [2]. Among many alternatives for mitigating carbon dioxide emission, the distributed energy systems (DES) have received increasing attention in large part due to their potential for reduced transmission line losses. In particular, in conjunction with localized renewable resources, especially wind and solar photovoltaic, distributed generation (DG) offers significant reduction in both line losses and carbon emission. The line loss reduction based on optimal size and location of DG has been studied by a number of researchers [3]-[5]. In this paper, we present a model for analyzing the reduction in transmission line losses using PowerWorld. We have chosen the Sacramento Municipal Utility District (SMUD) in California as our case study because the exact transmission line characteristics, including:  load demand, distances between loads and sources in the grid, and also because line impedances were publically available. The carbon emission reduction associated to the reduced line loss is calculated using the emission model and various emission factors presented by International Energy Agency [6].

The SMUD grid in 2010 had an annual base source of 7,152 GWh and an annual base load of 6,132 GWh with 1,020 GWh of annual transmission line losses. Our results show that implementing 2,000 GWh of DG at one of the substations 25 miles away from the central power plants can reduce the line losses to 693 GWh annually. Furthermore, beginning in 2013, by adding 160 GWh of DG annually at various substations, SMUD can completely eliminate its need for in-house central power generation by 2038, which includes a projected annual increase of about 1.2%. Without implementing any DG, the SMUD carbon emission is expected to rise from 2.31 million metric tons in 2013 to 2.89 million metric tons in 2050. Addition of only 2% renewable DG per year can lower SMUD’s carbon emission to 0.826 million metric tons, which is a 71% reduction in CO₂emission.

References:

[1] J. Conti and P. Holtberg, "International energy outlook, 2011," U.S. Energy Information Administration, Washington D.C., US, Tech. Rep. DOE/EIA-0484(2011), 2011. http://www.eia.gov/forecasts/ieo/pdf/0484(2011).pdf, Accessed April 2013  [2] P. D. Holtberg, et. al., "Annual energy outlook 2011: With projections to 2035," U.S. Energy Information Administration, Office of Intergrated Analysis and Forcasting; U.S. Department of Energy; Washington, DC 20585, Tech. Rep. DOE/EIA-0383(2010), 2011. http://www.columbia.edu/cu/alliance/documents/EDF/Wednesday/Heal_material.pdf Accessed April 2013. [3] Khoa, T., “Optimizing Location and Sizing of Distributed Generation in Distribution Systems,” Power Systems Conference and Exposition, 2006. PSCE '06. 2006 IEEE PES, pp. 725 – 732, 2006. [4] Chiradeja, P., “An approach to quantify the technical benefits of distributed generation,” IEEE Transactions on Energy Conversion,Vol. 19, No. 4, pp. 764 – 773, December 2004. [5] M. A. Kashem, M. Negnevitsky,  G. Ledwich, “Distributed generation for minimization of power losses in distribution systems,” 2006 IEEE Power Engineering Society General Meeting,  p. 8, 2006. [6]M. Van der Hoeven, “Co2 emission from fuel consumption highlights,” International Energy Agency, OECD/IEA 2012, http://www.iea.org/co2highlights/co2highlights.pdf, Accessed April 2013.