OVERVIEW OF MODERN ARCHITECTURES OF BIDIRECTIONAL HEATING SUBSTATION IN DISTRICT HEATING SYSTEMS ON TRANSPORT INFRASTRUCTURE FACILITIES

Summary. Modern systems of district heating of the fourth (4GDH) and district heating and cooling of the fifth (5GDHC) generations increasingly integrate renewable energy sources (RES) and waste heat, while changing the role of consumers to active “thermal prosumers”. The key element of such two-way interaction between the network and the building is a bidirectional heating substation, which provides both heat withdrawal from the network and the return of excess energy. The article is devoted to a review of modern architectures of bidirectional heating substation in the context of 4GDH and 5GDHC networks. The aim is to analyze typical configurations of these heating substation, identify differences in their functioning in conditions of low-temperature networks of the 4th generation and ultra low-temperature networks of the 5th, as well as outline technical, regulatory and economic aspects of implementation. The review considers the main functional components of bidirectional heating substation. It is shown that in 4GDH networks, bidirectional heating substations allow integrating distributed local heat sources at supply temperatures of ~50– 70°C. In contrast, in 5GDHC systems with a "neutral" temperature level of 10–30°C, each heat point is equipped with a reversible heat pump capable of operating both for heating and cooling. This ensures dynamic exchange of thermal energy (“heat sharing”) between consumers. The focus is on the key challenges of implementing bidirectional heating substation. In particular, the issues of hydraulic stability of two-way flows, the need to update the regulatory framework (accounting standards and compensation mechanisms for returned heat) and economic factors (significant investment costs, adaptation of tariff models) are considered. Keywords: district heating, bidirectional heating substation, renewable energy sources, thermal prosumer, heat pump, cooling, low-temperature district heating, waste heat energy.