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

154 Discussionity according to 2017 and 2025. By 2017 the amount of critically low prices will increaseby a factor of 8 (to 13 % share) on an annual basis, and by 2025 to a factor of 17 (29 %),when compared to 2008 (2 %). In addition, the average duration of these price periodsare lasting 2 and 3 times longer in 2017 and 2025, which is an interesting developmentin relation to the mentioned lack of market response from CHP units. Therefore, if nosystem measures are introduced by the time the wind capacity reaches the level of 2017and 2025, value will flow out of the system in the form of “free” electricity contributed bylocal heat costumers, a significant part of the year – something to be regarded as a greatmarket problem. However, with the average duration of the critical periods increasingfrom averagely 5 hours in 2008 to 12 and 15 hours in 2017 and 2015, there could be agreater techno-economical foundation for adapting to the market situation. In this connection,the model results show a complete down-regulation (and sometimes decommitment)of power from central units within these longer critical periods, which indicatesthat no technical limits in theory are exceeded. When looking at the 2017- and2025 reference scenario in general, it seems clear that operators of central units in thefuture will have to put up with a new role leaning more to the supplying of peak- andmedium loads, than the traditional base load, if value is not to be lost.It has been proved (chapter 6) that increasing heat prices from CHP units is a negativeresult of expanding the wind capacity in the reference scenario. Since the power generationcosts in decentralized heat distribution areas (gas) are much higher than in the centralareas (coal) the economic loss from the generated “waste electricity” increases correspondingly.Based on the larger potential for economic optimization in the decentralizedheat areas, this thesis therefore suggests a prioritization of the rural – rather thanurban – areas, in solving the problem of heat-constrained power generation.In the constraint analysis of central extraction units, it was shown that, averagely twothirds of the time that the units are committed, the backpressure line of the units is constrainingthe optimal solution, indicated by the generation of shadow prices (see Table7.12). This means that most of the time, power is generated in order to produce heat onextraction units. However, the share of constrained hours does in general not increase asthe wind production increases to the 2017 and 2025 scenarios. But with a 300 % marginalefficiency on the extracted heat, it could seem natural for the model to maximize thecombined heat and power supply by constantly operating in backpressure mode. Theconstraint given by the lower boiler output (Benson minimum) is generating twice asmany hours with shadow prices in 2025 (40 %), which means that the power generationis attempted minimized more in 2017 and 2025 than in 2008, and that lower capacitytherefore might be given more focus in the future than today.As shown from the calculations of the revenues of the model results of the reference scenario,central units will experience an increase of 12 % and 27 % in 2017 and 2025 underthe given assumptions. For comparison, decentralized CHP units will maximum loose 7%, thus being highly insensitivity to the increased wind penetration. An insensitivity,which can be explained by the natural monopoly characterizing the heat supply, whichin general characterizes the reference system’s ability to integrate the increased windcapacity.

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