Active and Passive Thermal Energy Storage in Combined Heat and Power Plants to Promote Wind Power Accommodation

Abstract

Employing thermal energy storage (TES) for combined heat and power (CHP) can improve flexibility in an integrated electric-thermal system (IETS) and therefore is beneficial to the accommodation of variable renewable energy sources (RESs). In general, there are two kinds of thermal storage: active thermal storage (ATS) and passive thermal storage (PTS). Active thermal storage capacity, provided by devices designed for special purposes, is generally fully exploited; passive thermal storage capacity, defined as the TES capacity provided by system components such as pipelines and building envelopes, has yet to be employed. To explore the possibility of using ATS and PTS for flexibility enhancement in the IETS, this paper presents a unified model of an IETS with both ATS and PTS in which heat transfer is included. In the proposed model, ATS is expressed by a phase-change TES device, and PTS is expressed by pipelines and heat consumers. Then, for the operation of the integrated system with both ATS and PTS, a dispatch model is presented, which can be simplified to a system with only ATS or only PTS by setting different boundary conditions. Finally, a test system is set up to verify the proposed model. The impact of factors such as transport time delays and temperature variation ranges in PTS is also analyzed in the test system. Results show that both ATS and PTS can provide extra flexibility in system operation and thus promote wind power accommodation.