Flexibility of combined heat and power plants: A review of technologies and operation strategies

With an increasing penetration of renewable energy, combined heat and power (CHP) plants play an important role in connecting different energy sectors of an integrated energy system (IES). Technical flexibility is an essential ability for CHPs to provide secure and economic operation of the IES, as well as to implement a profitable arbitrage in different markets. Operation strategies (OSs) are adopted to utilize the existing technical flexibility in an optimal way. The delivered flexibility is evaluated in terms of the system performance and operation profits. In this paper, a literature review on technical flexibility and characteristics of different CHP technologies is summarized. Moreover, the applications of CHP system flexibility in the IES are discussed from the perspectives of plant owners, system operators and demand side. Literature classified by cost-based and price-based OSs is studied for system operators and generation plant owners respectively. Characteristics of the OSs in terms of the CHP modeling, optimization objectives, constraints and algorithms, etc. are discussed and compared. The study is beneficial to achieve more economic operation of the IES and more profitable operation of the CHP system by system operators and plant owners. Future research work regarding this topic is investigated in the last part.