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pumped hydro, as Swider (2007) correctly points out. A major difference is that <strong>the</strong>compressor <strong>and</strong> generator could also be operated simultaneously.Wind production at <strong>the</strong> offshore node in <strong>the</strong> North Sea is set at a nominal capacity of1000MW with 5% unavailability. The wind power production has been generated frommeasurements at <strong>the</strong> FINO1 research plat<strong>for</strong>m at a height of 100m, following <strong>the</strong> multiturbinepower curve approach suggested by Nørgaard <strong>and</strong> Holttinen (2004). The annualcourse of data, which is used as input to <strong>the</strong> stochastic data model of WILMAR, isdisplayed in <strong>the</strong> following figure.Figure 7: Wind power generation at <strong>the</strong> offshore site5 Case descriptionsThe underlying idea is to compare an onshore AA-CAES power plant e.g. in <strong>the</strong>Ne<strong>the</strong>rl<strong>and</strong>s, Germany or Denmark with <strong>the</strong> option of placing it offshore. Alternatively,interconnector capacity to Norway could be increased. Three main exemplary cases aredistinguished:1. An AA-CAES storage (70% round-cycle efficiency) with a 150MWcompressor, 250MW generator <strong>and</strong> a storage volume of 2,000 MWh is inserted in <strong>the</strong>Northwestern German electricity market region. Fur<strong>the</strong>rmore, an offshore hub with1,000 MW wind power capacity <strong>and</strong> connected to <strong>the</strong> United Kingdom, <strong>the</strong> Ne<strong>the</strong>rl<strong>and</strong>s<strong>and</strong> Northwestern Germany with an interconnector capacity of 1,000 MW each is added.2. Everything else unchanged, <strong>the</strong> AA-CAES storage is placed in <strong>the</strong> offshore hub(instead of Germany).3. The AA-CAES storage is replaced by an equivalently increased interconnectorcapacity (250 MW) between Germany <strong>and</strong> Norway.6 ResultsFigure 8 illustrates an example of storage operation at <strong>the</strong> offshore site. The value isindicated as net generation because <strong>the</strong>se modes never occur simultaneously. It canclearly be seen that charging <strong>and</strong> production periods follow a diurnal pattern provokedby power prices.Figure 9 shows <strong>the</strong> analogous example if <strong>the</strong> AA-CAES facility is placed onshore.Production does not reach <strong>the</strong> maximum capacity of 250 MW, <strong>and</strong> <strong>the</strong> compressor <strong>and</strong>generator always operate simultaneously. This is due to <strong>the</strong> fact that this operation modeallows <strong>the</strong> AA-CAES unit to provide least-cost spinning reserves to <strong>the</strong> overallelectricity system. Spinning reserves are determined on a daily basis, which is why adaily spinning reserve level <strong>and</strong> hourly spikes caused by st<strong>and</strong>ard operation on dayahead<strong>and</strong> intraday markets can be distinguished. It should be noted that positiveRisø International <strong>Energy</strong> Conference 2011 Proceedings Page 4

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