Ultra-high-voltage direct current (UHVDC) converter stations represent a critical infrastructure for long-distance power transmission, but their converter valves continuously generate substantial low-grade waste heat—typically in the megawatt range—that conventional systems reject through cooling towers. This thermal rejection not only wastes energy but also requires significant auxiliary electricity consumption to maintain adequate valve-hall air conditioning, reducing overall system efficiency.
Researchers have developed an innovative cascade waste-heat utilization system to address this inefficiency. The approach integrates a vapor-compression heat pump (VCHP) that upgrades the low-grade converter waste heat, which then powers a single-effect lithium-bromide (LiBr) absorption refrigeration subsystem to produce chilled water for cooling demands.
The system operates through coupled thermodynamic cycles. The VCHP evaporator absorbs approximately 3.88 megawatts of waste heat from converter-cooling water, while the compressor (consuming 1.25 MW) raises this to a higher temperature level. The condenser then delivers 5.13 megawatts of upgraded heat to the absorption chiller's generator. The LiBr-water absorption refrigeration cycle produces 2.0 megawatts of chilled-water capacity using the heat input, without requiring direct electricity.
Testing across 24-hour operating cycles revealed strong performance metrics. The heat pump achieved a mean coefficient of performance (COP) of 4.10, meaning each unit of compressor input generated 4.1 units of heat output. The absorption subsystem delivered a mean COP of 0.74, while the integrated cooling-only system achieved 0.56 COP—all while maintaining crystallization-safe solution temperatures in the 51–55°C range.
Comparative analysis against baseline systems using conventional cooling towers plus electrically driven chillers showed approximately 40% improvement in normalized integrated performance across winter, summer, and transition seasonal scenarios. This result demonstrates significant potential for reducing both energy consumption and operational costs in UHVDC converter station operations, while improving thermal management efficiency. The thermodynamic feasibility has been validated, opening pathways for industrial deployment in converter stations worldwide.
