Integration of 50 % wind power in a CHP-based ... - Ea Energianalyse

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Integration of 50 % wind power in a CHP-based ... - Ea Energianalyse

122 Economic Analysesof the seven extraction units is switched on. The white areas indicate conventional operation(bypass being switched ‘off’). The corresponding wind and central heat demand isdisplayed to the right. Remembering, that the demands of the central heat distributionsareas (black curve) in the model are scaled according to the upper (and lower) capacitylimits of the connected extraction units, note, that the red lines indicate the lower heatcapacity limit when operating in bypass mode (a direct consequence of the Benson minimumof boilers).Of the things worth noticing from the figure is that, whereas BPO usual is assessed optimalin situations with high wind capacity and high heat demand, BPO is often alsoconsidered optimal in situations where the heat demand is lower than the minimumcapacity of the extraction unit (notice some of the hours in April as well as November inFigure 7.1 below). The consequence being, as seen, that the heat production sometimestakes place although bypass is turned on, as result of a very low electricity price. Thisillustrates the BPO-caused overproduction described previously.As a result of these factors, PBO is ‘switched on’ almost the entire time in the weeksamplefor January, whereas BPO only is ‘on’ about half of the time in the Novembersample. Note again that the wind production used for modeling these samples are thewindy profile.JanuaryAprilNovemberBPO:yes/noBPO:yes/noBPO:yes/noFull‐scale bypass scenario: Windy profileTime [h]Figure 7.1, Overview of the hourly 0-1 decisions of bypass operation in thefull-scale BPO scenario, one-week samples for January, April and November.Wind productionHeat demand(central)Minimum heat productionduring BPOUnits:G7G6G5G4G3G2G1Heat demand is oftenbelow the lower heat limitof BPO. Still, the el.production is bypassed.In addition to the full-scale BPO scenario, a scenario with BPO applied to a single unithas been modeled in order to fully study the BPO options made throughout the entireyear when subjected to the increased wind capacities. In this way, it also becomes clearhow often bypass operation is optimal given a smaller wind penetration, which is of interestin connection with the current West-DK system. Figure 7.2 below consists of threeplots, each indicating whether or not BPO is on or off for each hour of an entire year

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