No abstract

No abstract

online ordering: http://www.ntis.gov/ordering.htm Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste iii Executive SummaryAs renewable electricity becomes a larger portion of the electricity generation mix, new strategies will be required to accommodate fluctuations in energy generation from these sources. One of the primary strategies proposed for integrating large amounts of renewable energy is using energy storage to absorb excess electricity-generating capacity during times of low demand and/or high rates of generation by renewable sources and then reconverting this stored energy into electricity during periods of high demand and/or low renewable generation.Various energy storage technologies have been developed or proposed. The goal of this analysis was to develop a cost survey of the most-promising and/or mature energy storage technologies and compare them with several configurations employing hydrogen as the energy carrier. A simple energy arbitrage scenario was developed for a mid-sized energy storage system consisting of a 300-MWh nominal storage capacity that is charged during off-peak hours (18 hours per day on weekdays and all day on weekends) and discharged at a rate of 50 MW for 6 peak hours on weekdays.For all the hydrogen cases, off-peak and/or excess renewable electricity is used to electrolyze water to produce hydrogen, which is stored in compressed gas tanks or underground geologic formations. The hydrogen is reconverted into electricity using a polymer electrolyte membrane (PEM) fuel cell or hydrogen expansion combustion turbine. The hydrogen storage scenarios are compared with the use of several battery systems (nickel cadmium, sodium sulfur, and vanadium redox), pumped hydro, and compressed air energy storage (CAES).All the energy storage systems are evaluated for the same energy arbitrage scenario using consistent financial and operational assumptions. Costs and performance parameters for the technologies were gathered from literature sources and, in the case of the hydrogen expansion combustion turbine, Aspen Plus modeling. Producing excess hydrogen for use in vehicles or backup power is also evaluated. Two production levels are analyzed: 1,400 kg/day (roughly equivalent to the U.S. Department of Energy's standard model for smallscale distributed hydrogen production) and 12,000 kg/day. As for the purely energy arbitrage scenarios, it is assumed that hydrogen would be produced with offpeak/renewable electricity. Cost results for the analysis are presented in terms of the annualized ("levelized" 1 Figure ES -1 ) cost for producing the energy output from the storage system: electricity fed back onto the grid during peak hours ($/kWh) and, in the case of producing excess hydrogen for vehicles, hydrogen ($/kg).summarizes the comparison of levelized cost of delivered electricity for hydrogen (green bars) and competing technologies (blue bars). For each technology, high-cost, mid-range, and low-cost cases were analyzed, and sensitivity analyses were 1 The leve...

Executive SummaryThis report is intended to provide offshore wind industry stakeholders a basis for evaluating potential cost saving installation, operation, and maintenance (IO&M) strategies and technologies. Some of the IO&M strategies in this report were analyzed without projecting the capital expenditures associated with an enabling technology or method. Thus, the results show the upside or added value to a strategy (e.g. increased energy production), and not the potential downside (e.g. added capital cost of new hardware). The results of the analysis can therefore be used by industry stakeholders to take the cost savings presented in this report and add their revised technologies costs to arrive at a net decrease or increase in cost of energy resulting from a proposed IO&M strategy. This allows many technologies that target the same improvement area to be evaluated subsequent to this study. To clarify this concept, an example is presented below.Company X is interested in bringing an innovative vessel capable of operating at higher wind and wave conditions to market. If a strategy using an innovative vessel capable of operating in higher wind and wave conditions (similar to Company X's design) is shown to reduce costs by $100/kW with respect to the baseline, Company X can see that in order to be viable in the market, they must be able to deliver their innovative vessel at a rate no more than $100/kW greater than the vessel rate used in the baseline. If Company X can deliver their innovative vessel at $25/kW more than the baseline, they will have demonstrated that their new vessel technology is capable of saving $75/kW with respect to the baseline. IntroductionIO&M is expected to account for nearly one-third of offshore wind levelized cost of energy (LCOE) in the United States (U.S. Department of Energy, 2011). Consequently, there is a large potential for reducing LCOE through advanced IO&M strategies. NREL and ECN, along with a panel of subject matter experts who provided input, have used their offshore wind cost modeling capabilities to fulfill the project's two primary objectives:• Conduct analysis and modeling to identify the most practical means of reducing offshore wind LCOE through advanced IO&M techniques, integrated service providers, and preferred supporting infrastructure.• Identify preferred IO&M strategies in a case study of a hypothetical U.S. offshore wind project. viThis report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.To accomplish the objectives related to installation costs, NREL has developed a new offshore wind turbine installation cost module which, coupled with the NREL offshore wind plant balance of station (BOS) model, is capable of analyzing many scenarios including the six (6) turbine assembly strategies and three (3) additional project installation strategies that this study analyzes.To accomplish the objectives related to O&M costs, ECN has established an O&M tool for the U.S. offshore market based on their industry-l...

No abstract