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| 1 |
ID:
115156
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2012.
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| Summary/Abstract |
We investigate the economic viability of coupling a wind farm with compressed air energy storage (CAES) to participate in the day-ahead electricity market at a time when renewable portfolio standards are not binding and wind competes freely in the marketplace. In our model, the CAES is used to reduce the risk of committing uncertain quantities of wind energy and to shift dispatch of wind generation to high price periods. Other sources of revenue (capacity markets, ancillary services, price arbitrage) are not included in the analysis. We present a model to calculate profit maximizing day-ahead dispatch schedules based on wind forecasts. Annual profits are determined with dispatch schedules and actual wind generation values.
We find that annual income for the modeled wind-CAES system would not cover annualized capital costs using market prices from the years 2006 to 2009. We also estimate market prices with a carbon price of $20 and $50 per tonne CO2 and find that revenue would still not cover the capital costs. The implied cost per tonne of avoided CO2 to make a wind-CAES profitable from trading on the day-ahead market is roughly $100, with large variability due to electric power prices.
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| 2 |
ID:
116937
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2012.
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| Summary/Abstract |
We develop a metric to quantify the sub-hourly variability cost of individual wind plants and show its use in valuing reductions in wind power variability. Our method partitions wind energy into hourly and sub-hourly components and uses corresponding market prices to determine variability costs. We use publically available 15-min ERCOT data, although the method developed can be applied to higher time resolution data if available. We do not estimate uncertainty costs though our metric can separate integration costs into variability and uncertainty components. The mean variability costs arising from 15-min to 1-h variations (termed load following) for 20 ERCOT wind plants was $8.73±$1.26 per MWh in 2008 and $3.90±$0.52 per MWh in 2009. Load following variability costs decrease as capacity factors increase, indicating wind plants sited in locations with good wind resources cost a system less to integrate. Twenty interconnected wind plants had a variability cost of $4.35 per MWh in 2008. The marginal benefit of interconnecting another wind plant diminishes rapidly: it is less than $3.43 per MWh for systems with 2 wind plants already interconnected, less than $0.7 per MWh for 4-7 wind plants, and less than $0.2 per MWh for 8 or more wind plants.
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| 3 |
ID:
115126
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2012.
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| Summary/Abstract |
A reconfigurable network can change its topology by opening and closing switches on power lines. We use real wind, solar, load, and cost data and a model of a reconfigurable distribution grid to show that reconfiguration allows a grid operator to reduce operational losses as well as to accept more intermittent renewable generation than a static configuration can. Net present value analysis of automated switch technology shows that the return on investment is negative for this test network when considering only loss reduction, but that the investment is attractive under certain conditions when reconfiguration is used to minimize curtailment.
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| 4 |
ID:
104888
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| Publication |
2011.
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| Summary/Abstract |
Compressed air energy storage (CAES) could be paired with a wind farm to provide firm, dispatchable baseload power, or serve as a peaking plant and capture upswings in electricity prices. We present a firm-level engineering-economic analysis of a wind/CAES system with a wind farm in central Texas, load in either Dallas or Houston, and a CAES plant whose location is profit-optimized. With 2008 hourly prices and load in Houston, the economically optimal CAES expander capacity is unrealistically large - 24 GW - and dispatches for only a few hours per week when prices are highest; a price cap and capacity payment likewise results in a large (17 GW) profit-maximizing CAES expander. Under all other scenarios considered the CAES plant is unprofitable. Using 2008 data, a baseload wind/CAES system is less profitable than a natural gas combined cycle (NGCC) plant at carbon prices less than $56/tCO2 ($15/MMBTU gas) to $230/tCO2 ($5/MMBTU gas). Entering regulation markets raises profit only slightly. Social benefits of CAES paired with wind include avoided construction of new generation capacity, improved air quality during peak times, and increased economic surplus, but may not outweigh the private cost of the CAES system nor justify a subsidy.
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| 5 |
ID:
086025
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| Publication |
2009.
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| Summary/Abstract |
Each year, the effects of climate change are coming into sharper focus. Barely a month goes by without some fresh bad news: ice sheets and glaciers are melting faster than expected, sea levels are rising more rapidly than ever in recorded history, plants are blooming earlier in the spring, water supplies and habitats are in danger, birds are being forced to find new migratory patterns.The odds that the global climate will reach a dangerous tipping point are increasing. Over the course of the twenty-first century, key ocean currents, such as the Gulf Stream, could shift radically, and thawing permafrost could release huge amounts of additional greenhouse gases into the atmosphere. Such scenarios, although still remote, would dramatically accelerate and compound the consequences of global warming. Scientists are taking these doomsday scenarios seriously because the steady accumulation of warming gases in the atmosphere is forcing change in the climate system at rates so rapid that the outcomes are extremely difficult to predict.Eliminating all the risks of climate change is impossible because carbon dioxide emissions, the chief human contribution to global warming, are unlike conventional air pollutants, which stay in the atmosphere for only hours or days. Once carbon dioxide enters the atmosphere, much of it remains for over a hundred years. Emissions from anywhere on the planet contribute to the global problem, and once headed in the wrong direction, the climate system is slow to respond to attempts at reversal. As with a bathtub that has a large faucet and a small drain, the only practical way to lower the level is by dramatically cutting the inflow. Holding global warming steady at its current rate would require a worldwide 60-80 percent cut in emissions, and it would still take decades for the atmospheric concentration of carbon dioxide to stabilize.
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| 6 |
ID:
169715
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| Summary/Abstract |
We assess the ability of distributed solar to defer distribution capacity projects in a typical low load growth utility in the Northeast USA, PECO. We find that targeted placement can increase the deferral value of solar up to fourfold, but that deferrable projects are rare. In our baseline scenario, we find a 5% solar energy penetration with Net Energy Metering rolled out from 2020 to 2030 would increase rates by 0.8% over a 20-year horizon and generate just $1 MM in net present deferral value. This estimate assumes untargeted placement of solar, a low effective capacity (i.e. the reduction in peak load relative to solar's nominal capacity), a 1% growth rate, and 1% of PECO's distribution yearly capex budget that is deferrable. A higher effective capacity (e.g. from coupling energy storage with solar) and targeted placement could generate a net $8 MM of value over the same horizon, but the rate increase is mostly unaffected. We recommend the use of targeted solar placement in utility planning processes. Compared to untargeted placement, targeted placement can increase the total deferral value fourfold, but the effect on rates is small for PECO because few capacity deferral opportunities exist.
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| 7 |
ID:
180165
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| Summary/Abstract |
A fundamental policy question for distributed energy resources (DER) is whether they create system benefits shared by all utility customers in addition to being profitable for the installing customer. This question has received considerable attention in “value of DER” and net metering reform proceedings for behind-the-meter solar photovoltaics in recent years. Commercial customer-sited lithium-ion batteries with a primary use case of demand charge management are forecast to greatly increase in the coming decade due to falling storage costs, making comparison of their customer and system benefits a timely topic in DER valuation. We conduct an overview of the system benefits of standalone commercial customer-sited storage on United States’ electric tariffs and find system benefits will not be realized for many standalone commercial customer-sited storage installations in the absence of incentives for storage dispatch during the top 50–100 annual hours that drive grid infrastructure investment. Regulatory implementation of default peak pricing during a small subset of annual hours for customer-sited storage can realize additional system benefits and offer Pareto improvement. Additional transparency in regulatory estimates of these system benefits helps catalyze longer-term visions for increased competition at the retail level using DERs.
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| 8 |
ID:
092748
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| Publication |
2009.
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| Summary/Abstract |
Using data from the North American Electric Reliability Council (NERC) for 1984-2006, we find several trends. We find that the frequency of large blackouts in the United States has not decreased over time, that there is a statistically significant increase in blackout frequency during peak hours of the day and during late summer and mid-winter months (although non-storm-related risk is nearly constant through the year) and that there is strong statistical support for the previously observed power-law statistical relationship between blackout size and frequency. We do not find that blackout sizes and blackout durations are significantly correlated. These trends hold even after controlling for increasing demand and population and after eliminating small events, for which the data may be skewed by spotty reporting. Trends in blackout occurrences, such as those observed in the North American data, have important implications for those who make investment and policy decisions in the electricity industry. We provide a number of examples that illustrate how these trends can inform benefit-cost analysis calculations. Also, following procedures used in natural disaster planning we use the observed statistical trends to calculate the size of the 100-year blackout, which for North America is 186,000 MW.
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| 9 |
ID:
150368
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| Summary/Abstract |
We investigate the resource adequacy requirements of the PJM Interconnection, and the sensitivity of capacity procurement decisions to the choice of reliability metric used to measure resource adequacy. Assuming that plants fail independently, we find that PJM's 2010 reserve margin of 20.5% was sufficient to achieve the stated reliability standard of one loss of load event per ten years, with 0.012 expected loss of load events per year. PJM could reduce reserve margins to 13% and still achieve adequate levels of reliability as measured by the 2.4 Loss of Load Hours metric and the 0.001% Unserved Energy metric, which are used by other U.S. and international systems. A reserve margin of 13–15% would minimize long-run system costs. Reducing reserve margins from 20.5% to 13% in 2010 would have reduced PJM's capacity procurement by 11 GW, the same amount of coal capacity that PJM has identified as at high risk of retirement. We also investigate the risk posed by correlated failures among generators, a risk traditionally not modeled by system planners. We illustrate that three types of correlated failures may increase outage risks: natural gas supply disruptions, reduced reliability among generators during winter months, and the simultaneous shutdown of multiple nuclear generators for regulatory reasons.
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| 10 |
ID:
097340
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| Publication |
2010.
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| Summary/Abstract |
We present the first frequency-dependent analyses of the geographic smoothing of wind power's variability, analyzing the interconnected measured output of 20 wind plants in Texas. Reductions in variability occur at frequencies corresponding to times shorter than 24 h and are quantified by measuring the departure from a Kolmogorov spectrum. At a frequency of 2.8×10-4 Hz (corresponding to 1 h), an 87% reduction of the variability of a single wind plant is obtained by interconnecting 4 wind plants. Interconnecting the remaining 16 wind plants produces only an additional 8% reduction. We use step change analyses and correlation coefficients to compare our results with previous studies, finding that wind power ramps up faster than it ramps down for each of the step change intervals analyzed and that correlation between the power output of wind plants 200 km away is half that of co-located wind plants. To examine variability at very low frequencies, we estimate yearly wind energy production in the Great Plains region of the United States from automated wind observations at airports covering 36 years. The estimated wind power has significant inter-annual variability and the severity of wind drought years is estimated to be about half that observed nationally for hydroelectric power.
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