Title: Facilitating the Integration of Renewable Energy through Combined-heat-and-power Flexibility
Other Titles: Faciliteren van de integratie van hernieuwbare energie door middel van WKK-flexibiliteit
Authors: Zapata Riveros, Juliana Victoria
Issue Date: 26-May-2015
Abstract: The liberalization of the electricity markets as well as the growing environmental concerns have triggered the widespread use of distributed generation technologies, especially renewable energy resources and combined heat and power generation (CHP). Nevertheless, the intermittency of some of these technologies such as photovoltaicnbsp;and wind turbines, yields an important challenge to the electric grid operator.
In this context it is proposed to group controllable and intermittent generation devices in what is known as a virtual power plant (VPP). This kind of aggregation will facilitate not only the participation of distributed generators in the electricity market but it also might help to compensate the forecast errors of renewables by using the flexibility of controllable devices.
The aim of this work is to develop several control strategies for the economic optimal operation of distributed generation devices that are aggregated into a virtual power plant incorporating thermal‑demand aspects. The main focus is on the role that cogeneration can play in increasing the flexibility of the system and the profits of the virtual power plant operator. In this respect, three main research questions are assessed: the ability to reduce the imbalance volume and the associated costs using residential micro‑CHPs, the opportunity to provide passive balancing with an aggregation of micro‑CHPs andnbsp;ability of cogeneration district heating to compensate for the uncertainty in the system.
It is shown that micronbsp;are able to partially compensate for the deviations between local electric power demand and local power generation. Nevertheless, this imbalance volume reduction does not always lead to a reduction of the imbalance cost. It is demonstrated that a control strategy aiming to minimize imbalance volumes disregarding the imbalance tariffs can lead to an increase in operational costs, especially during spring and summer. Furthermore, the results indicate that even in the best case scenario, the level of savings are not to be sufficiently high to motivate CHP owners to join a VPP.
The possibility to provide real-time balancing services or passive balancing is assessed for an aggregation of micro-CHP devices installed in different households and service buildings. The resultsnbsp;a clear indication that providing passive balancing leads to a total cost decrease in all the seasons compared to a case in which the electricity is traded only in the day‑ahead market.
Finally, the added value of using CHP linked to a district heating network (CHP‑DH) to compensate for the uncertainties regarding electricity generation and market prices development is investigated. Stochastic programming isnbsp;to explicitly model the uncertainties innbsp;system. It is shown that using the flexibility of the CHP‑DH together with a thermal‑storage unit results in an increase in profits during spring and summer. However, due to the high demand for heat during the winter, the CHP‑DH can offer less flexibility during these months resulting in a lower added value. In addition, if the VPP is allowed to react in real time to the current imbalance prices the profit increase is even larger.
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Applied Mechanics and Energy Conversion Section

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