Operational Flexibility of Small-Scale Electricity-Coupled Heat Generating Units

Abstract

Heat generation that is coupled with electricity usage, like combined heat and power generators or heat pumps, can provide operational flexibility to the electricity sector. In order to make use of this in an optimized way, the flexibility that can be provided by such plants needs to be properly quantified. This paper proposes a method for quantifying the flexibility provided through a cluster of such heat generators. It takes into account minimum operational time and minimum down-time of heat generating units. Flexibility is defined here as the time period over which plant operation can be either delayed or forced into operation, thus providing upward or downward regulation to the power system on demand. Results for one case study show that a cluster of several smaller heat generation units does not provide much more delayed operation flexibility than one large unit with the same power, while it more than doubles the forced operation flexibility. Considering minimum operational time and minimum down-time of the units considerably limits the available forced and delayed operation flexibility, especially in the case of one large unit. Keywords Operational flexibility • Electricity-coupled heat generation • Combined heat and power generation • Heat pumps • Virtual power plants • Smart grid Nomenclature Abbreviations CHP Combined heat and power DH District heating EHG Electricity-coupled heat generator HP Heat pump TES Thermal energy storage VPP Virtual power plant Superscripts Max Symbol related to the maximum operation mode Min Symbol related to the minimum operation mode Subscripts t Denotes the current time interval,

Quantifying the Operational Flexibility of Distributed Cross-Sectoral Energy Systems for the Integration of Volatile Renewable Electricity Generation

“…The indicators from the literature can be categorized into indicators for time flexibility in [29,35,36], power flexibility in [29][30][31][32][33]35,41], energy flexibility in [31,32,35,37,38], energy efficiency in [31,32,34], and the quantification of flexibility through external variables or signals in [31,[37][38][39][40]. The indicators for time flexibility, power flexibility, energy flexibility, and energy efficiency focus on flexibility definitions concerning only single energy units or separate energy systems.…”

Quantifying Operational Flexibility of Distributed Cross-Sectoral Energy Systems for the Integration of Volatile Renewable Electricity Generation

“…The indicators from the literature can be categorized into indicators for time flexibility in [22][23][24], power flexibility in [22,[24][25][26][27][28][29], energy flexibility in [22,27,28,30,31], energy efficiency in [27,28,32] and the quantification of flexibility through external variables or signals in [27,30,31,33,34]. The indicators for time flexibility, power flexibility, energy flexibility and energy efficiency focus on flexibility definitions concerning only single energy units or separate energy systems.…”