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Lu, Xi

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Lu, Xi
Author's Publications: search.filters.isAuthorOfPublication.346c0602-e81c-44e4-8899-dc05304c205c

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Now showing 1 - 10 of 12
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    India’s Potential for Integrating Solar and On- and Offshore Wind Power Into Its Energy System
    (Springer Science and Business Media LLC, 2020-09-21) Lu, Tianguang; Sherman, Peter; Chen, Xinyu; Chen, Shi; Lu, Xi; McElroy, Michael
    This paper considers options for a future Indian power economy in which renewables, wind and solar, could meet 80% of anticipated 2040 power demand supplanting the country’s current reliance on coal. Using a cost optimization model, here we show that renewables could provide a source of power cheaper or at least competitive with what could be supplied using fossil-based alternatives. The ancillary advantage would be a significant reduction in India’s future power sector related emissions of CO2. Using a model in which prices for wind turbines and solar PV systems are assumed to continue their current decreasing trend, we conclude that an investment in renewables at a level consistent with meeting 80% of projected 2040 power demand could result in a reduction of 85% in emissions of CO2 relative to what might be expected if the power sector were to continue its current coal dominated trajectory.
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    Optimal Integration of Offshore Wind Power for a Steadier, Environmentally Friendlier, Supply of Electricity in China
    (Elsevier, 2013) Lu, Xi; McElroy, Michael; Nielsen, Chris; Chen, Xinyu; Huang, Junling
    Demand for electricity in China is concentrated to a significant extent in its coastal provinces. Opportunities for production of electricity by on-shore wind facilities are greatest however in the north and west of the country. Using high resolution wind data derived from the GEOS-5 assimilation, this study shows that investments in off-shore wind facilities in these spatially separated regions (Bohai-Bay or BHB, Yangtze-River Delta or YRD, Pearl-River Delta or PRD) could make an important contribution to overall regional demand for electricity in coastal China. An optimization analysis indicates that hour-to-hour variability of outputs from a combined system can be minimized by investing 24% of the power capacity in BHB, 30% in YRD and 47% in PRD. The analysis suggests that about 28% of the overall off-shore wind potential could be deployed as base load power replacing coal-fired system with benefits not only in terms of reductions in CO2 emissions but also in terms of improvements in regional air quality. The interconnection of off-shore wind resources contemplated here could be facilitated by China’s 12th-five-year plan to strengthen inter-connections between regional electric-power grids.
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    Additionality of Wind Energy Investments in the U.S. Voluntary Green Power Market
    (Elsevier, 2014) Gillenwater, Michael; Lu, Xi; Fischlein, Miriam
    In the United States, electricity consumers are told that they can “buy” electricity from renewable energy projects, versus fossil fuel-fired facilities, through participation in voluntary green power markets. The marketing messages communicate to consumers that they are causing additional renewable energy generation and reducing emissions through their participation and premium payments for a green label. Using a spatial financial model and a database of registered Green-e wind power facilities, the analysis in this paper shows that the voluntary Renewable Energy Certificate (REC) market has a negligible influence on the economic feasibility of these facilities. Nevertheless, voluntary green power marketers at least implicitly claim that buying their products creates additional renewable energy. This study indicates the contrary. Participants in U.S. voluntary green power markets associated with wind power, therefore, appear to be receiving misleading marketing messages regarding the effect of their participation. In the process of completing this analysis, a potentially relevant factor in explaining investor behavior was identified: the potential for the overlap of voluntary REC markets with compliance REC markets that supply utilities need to meet their obligations of Renewable Energy Portfolio Standard (RPS). The majority of state RPS rules allow for regional or even national sourcing of RECs, meaning that projects are generally eligible to provide compliance RECs to utilities not only in their home states, but in several other states.
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    Opportunity for Offshore Wind to Reduce Future Demand for Coal-Fired Power Plants in China with Consequent Savings in Emissions of CO 2
    (American Chemical Society (ACS), 2014) Lu, Xi; McElroy, Michael; Chen, Xinyu; Kang, Chongqing
    Although capacity credits for wind power have been embodied in power systems in the U.S. and Europe, the current planning framework for electricity in China continues to treat wind power as a nondispatchable source with zero contribution to firm capacity. This study adopts a rigorous reliability model for the electric power system evaluating capacity credits that should be recognized for offshore wind resources supplying power demands for Jiangsu, China. Jiangsu is an economic hub located in the Yangtze River delta accounting for 10% of the total electricity consumed in China. Demand for electricity in Jiangsu is projected to increase from 331 TWh in 2009 to 800 TWh by 2030. Given a wind penetration level of 60% for the future additional Jiangsu power supply, wind resources distributed along the offshore region of five coastal provinces in China (Shandong, Jiangsu, Shanghai, Zhejiang, and Fujian) should merit a capacity credit of 12.9%, the fraction of installed wind capacity that should be recognized to displace coal-fired systems without violating the reliability standard. In the high-coal-price scenario, with 60% wind penetration, reductions in CO2 emissions relative to a business as usual reference could be as large as 200.2 million tons of CO2 or 51.8% of the potential addition, with a cost for emissions avoided of $29.0 per ton.
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    Prospects for shale gas production in China: Implications for water demand
    (Elsevier BV, 2016) Guo, Meiyu; Lu, Xi; Nielsen, Chris; McElroy, Michael; Shi, Wenrui; Chen, Yuntian; Xu, Yuan
    Development of shale gas resources is expected to play an important role in China's projected transition to a low-carbon energy future. The question arises whether the availability of water could limit this development. The paper considers a range of scenarios to define the demand for water needed to accommodate China's projected shale gas production through 2020. Based on data from the gas field at Fuling, the first large-scale shale gas field in China, it is concluded that the water intensity for shale gas development in China (water demand per unit lateral length) is likely to exceed that in the US by about 50%. Fuling field would require a total of 39.9–132.9 Mm3 of water to achieve full development of its shale gas, with well spacing assumed to vary between 300 and 1000 m. To achieve the 2020 production goal set by Sinopec, the key Chinese developer, water consumption is projected to peak at 7.22 Mm3 in 2018. Maximum water consumption would account for 1% and 3%, respectively, of the available water resource and annual water use in the Fuling district. To achieve China's nationwide shale gas production goal set for 2020, water consumption is projected to peak at 15.03 Mm3 in 2019 in a high-use scenario. It is concluded that supplies of water are adequate to meet demand in Fuling and most projected shale plays in China, with the exception of localized regions in the Tarim and Jungger Basins.
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    Challenges faced by China compared with the US in developing wind power
    (Springer Nature, 2016) Lu, Xi; McElroy, Michael; Peng, Wei; Liu, Shiyang; Nielsen, Chris; Wang, Haikun
    In the 21st Conference of the Parties held in Paris in December 2015, China pledged to peak its carbon emissions and increase non-fossil energy to 20% by 2030 or earlier. Expanding renewable capacity, especially wind power, is a central strategy to achieve these climate goals. Despite greater capacity for wind installation in China compared to the US (114.7 vs. 65.9 GW), less wind electricity is generated in China (153.4 vs. 181.8 TWh). Here, we quantify the relative importance of the key factors accounting for the unsatisfactory performance of Chinese wind farms. Different from qualitative studies, we find that the difference in wind resources explains only a small fraction of the current US-China difference in wind power output (-17.9% in 2012); the curtailment of wind power, differences in turbine quality and delayed connection to the grid are identified as the three primary factors (respectively -49.3%, -50.2%, and -50.3% in 2012). Improvements in both technology choices and the policy environment are critical in addressing these challenges.
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    Meteorologically Defined Limits to Reduction in the Variability of Outputs from a Coupled Wind Farm System in the Central US
    (Elsevier, 2013-08-26) Huang, Junling; Lu, Xi; McElroy, Michael
    Studies suggest that onshore wind resources in the contiguous US could readily accommodate present and anticipated future US demand for electricity. The problem with the output from a single wind farm located in any particular region is that it is variable on time scales ranging from minutes to days posing difficulties for incorporating relevant outputs into an integrated power system. The high frequency (shorter than once per day) variability of contributions from individual wind farms is determined mainly by locally generated small scale boundary layer. The low frequency variability (longer than once per day) is associated with the passage of transient waves in the atmosphere with a characteristic time scale of several days. Using 5 years of assimilated wind data, we show that the high frequency variability of wind-generated power can be significantly reduced by coupling outputs from 5 to 10 wind farms distributed uniformly over a ten state region of the Central US in this study. More than 95% of the remaining variability of the coupled system is concentrated at time scales longer than a day, allowing operators to take advantage of multi-day weather forecasts in scheduling projected contributions from wind.
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    Implications of the Recent Reductions in Natural Gas Prices for Emissions of \(CO_2\) from the US Power Sector
    (American Chemical Society, 2012) Lu, Xi; Salovaara, Jackson; McElroy, Michael
    \(CO_2\) emissions from the US power sector decreased by 8.76% in 2009 relative to 2008 contributing to a decrease over this period of 6.59% in overall US emissions of greenhouse gases. An econometric model, tuned to data reported for regional generation of US electricity, is used to diagnose factors responsible for the 2009 decrease. More than half of the reduction is attributed to a shift from generation of power using coal to gas driven by a recent decrease in gas prices in response to the increase in production from shale. An important result of the model is that, when the cost differential for generation using gas rather than coal falls below 2–3 cents/kWh, less efficient coal fired plants are displaced by more efficient natural gas combined cycle (NGCC) generation alternatives. Costs for generation using NGCC decreased by close to 4 cents/kWh in 2009 relative to 2008 ensuring that generation of electricity using gas was competitive with coal in 2009 in contrast to the situation in 2008 when gas prices were much higher. A modest price on carbon could contribute to additional switching from coal to gas with further savings in \(CO_2\) emissions.
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    Costs for Integrating Wind into the Future ERCOT System with Related Costs for Savings in \(CO_2\) Emissions
    (American Chemical Society, 2011) Lu, Xi; McElroy, Michael; Sluzas, Nora A.
    Wind power can make an important contribution to the goal of reducing emissions of \(CO_2\). The major problem relates to the intrinsic variability of the source and the difficulty of reconciling the supply of electricity with demand particularly at high levels of wind penetration. This challenge is explored for the case of the ERCOT system in Texas. Demand for electricity in Texas is projected to increase by approximately 60% by 2030. Considering hourly load data reported for 2006, assuming that the pattern of demand in 2030 should be similar to 2006, and adopting as a business as usual (BAU) reference an assumption that the anticipated additional electricity should be supplied by a combination of coal and gas with prices, discounted to 2007 dollars of $2 and $6 per MMBTU respectively, we conclude that the bus-bar price for electricity would increase by about 1.1¢/kWh at a wind penetration level of 30%, by about 3.4¢/kWh at a penetration level of 80%. Corresponding costs for reductions in \(CO_2\) range from $20/ton to $60/ton. A number of possibilities are discussed that could contribute to a reduction in these costs including the impact of an expanded future fleet of electrically driven vehicles.
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    Accelerated Reduction in \(SO_2\) Emissions from the U.S. Power Sector Triggered by Changing Prices of Natural Gas
    (American Chemical Society, 2012) Lu, Xi; McElroy, Michael; Wu, Gang; Nielsen, Chris
    Emissions of sulfur dioxide (\(SO_2\)) from the U.S. power sector decreased by 24% in 2009 relative to 2008. The Logarithmic Mean Divisia Index (LMDI) approach was applied to isolate the factors responsible for this decrease. It is concluded that 15% of the decrease can be attributed to the drop in demand for electricity triggered by the economic recession, and 28% can be attributed to switching of fuel from coal to gas responding to the decrease in prices for the latter. The largest factor in the decrease, close to 57%, resulted from an overall decline in emissions per unit of power generated from coal. This is attributed in part to selective idling of older, less efficient coal plants that generally do not incorporate technology for sulfur removal, and in part to continued investments by the power sector in removal equipment in response to the requirements limiting emissions imposed by the U.S. Environmental Protection Agency (U.S. EPA). The paper argues further that imposition of a modest tax on emissions of carbon would have ancillary benefits in terms of emissions of \(SO_2\).