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

134 Economic AnalysesShadow price factor, backpressure [%]Extraction unitsEl.SYSTEM SCENARIOS: Central units: G1 G2 G3 G4 G5 G6 G7 Meanc v2008 66.2 65.7 65.6 67.5 68.5 66.7 66.1 66.6Reference2017 70.0 66.6 66.6 70.3 69.7 69.4 69.6 68.9c m2025 68.6 66.9 66.9 69.6 70.0 69.2 68.0 68.52008 46.2 46.2 46.8 45.7 47.4 45.7 47.5 46.5Pel minHeat pump2017 57.6 57.9 55.0 55.7 56.6 56.6 58.9 56.9Heat2025 63.6 61.2 62.2 62.0 61.0 62.4 66.0 62.6Table 7.12, Shadow price factors – the amount of operating hours with shadow prices differentfrom zero, indicating the share of electricity generation constrained by the heat demand. Asseen on the red line, shadow prices are generated by relaxing the linear constraint one unit inthe electricity’s direction (y-axis).One thing is how frequent the backpressure limit causes (or forces) the electricity to beconstrained, another, is the size of the particular shadow prices and thus, the necessarycontribution from heat. Table 7.13 below shows a comparison of the average shadowprices of the extraction units in the different system scenarios, showing significant differencesbetween the reference and heat pump scenarios as well as difference betweenthe different wind penetration levels. In the reference scenario, the average shadowprice increases from 17 €/MWh in 2008 up to 20 €/MWh and 22 €/MWh in 2017 and2025, respectively, being a logical result of the low electricity prices caused by the increasedwind penetration (cf. the increasing heat production costs from falling electricityprices). In the heat pump system, the average shadow price is around one third of thecorresponding shadow price of the reference scenario. The main reason for this is probablythe higher shadow price on electricity characterizing the heat pump system.Average shadow price, backpressure [€/MWh]Extraction unitsEl.SYSTEM SCENARIOS: Central units: G1 G2 G3 G4 G5 G6 G7 meanc v2008 17.28 17.02 17.01 17.08 16.89 17.18 17.28 17.11Reference2017 20.42 20.47 20.47 19.99 20.31 19.97 20.44 20.30c m2025 20.79 23.79 23.79 20.90 23.62 20.83 20.54 22.042008 5.74 5.74 5.74 5.75 5.71 5.75 5.71 5.73Pel minHeat pump2017 6.90 6.67 6.76 7.05 6.64 6.98 6.93 6.85Heat2025 7.61 7.35 7.58 8.25 7.35 8.14 7.91 7.74Table 7.13, Average shadow price level from backpressure constraint. Note that the averageshadow price level of the heat pump scenario is about one third of the corresponding price inthe reference scenario.So far, we have seen, that when the electricity price drops to a critically low level, thecentral power generation decreases to a minimum (if not de-committing) while maintaininga correspondingly low heat production. Therefore, the constraint given by the lowerbound of the power generation P el,min is assumed to affect the optimal solution. In Table7.14 the shadow price characteristics of this particular constraint is seen, calculated for

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