DC-Powered Smart Streetlights Gain Momentum in China’s Renewable Push
In a bold stride toward urban decarbonization and smart infrastructure, Chinese engineers and energy planners are championing a transformative approach to municipal lighting: direct current (DC)-powered streetlights integrated with distributed photovoltaics, energy storage, and electric vehicle (EV) charging. This emerging model, detailed in a recent peer-reviewed study published in Zhaoming Gongcheng Xuebao (the Journal of Illuminating Engineering), offers a compelling blueprint for cities worldwide grappling with energy inefficiency, grid congestion, and the urgent need to scale renewable integration.
The research, led by Jianwei Liu of the China Power Engineering Consulting Group Co., Ltd., alongside a multidisciplinary team from China Energy Engineering Group Tianjin Electric Power Design Institute Co., Ltd., presents a comprehensive technical and economic case for DC-based street lighting systems. Far from a niche experiment, the paper argues that DC streetlights represent a strategic convergence point for multiple clean energy trends—solar power, battery storage, EV adoption, and intelligent urban management—all anchored on a single, scalable infrastructure platform.
At first glance, streetlights may seem like a mundane component of urban life. Yet they are among the most ubiquitous and energy-intensive public utilities. In China alone, road lighting accounts for roughly 25–30% of total lighting electricity consumption, which itself represents about 13% of the nation’s overall electricity use. Traditional alternating current (AC) systems, often powered by high-pressure sodium or metal halide lamps, suffer from high energy losses, limited compatibility with modern LED technology, and vulnerability to leakage currents and voltage drops over long distribution runs. These inefficiencies are magnified in sprawling metropolitan areas where power must travel kilometers from substations to individual fixtures.
Enter the DC streetlight. By eliminating the need for repeated AC-to-DC conversion—required by virtually all modern LED luminaires—DC systems dramatically reduce energy waste. More importantly, they create a native environment for integrating renewable sources like rooftop or pole-mounted solar panels, which naturally produce DC power. This synergy slashes conversion losses, simplifies system architecture, and enhances overall reliability.
Liu and his co-authors emphasize that the advantages extend well beyond energy savings. A DC microgrid for street lighting enables what they term a “four-in-one” energy ecosystem: generation (via photovoltaics), storage (through batteries), consumption (lighting and auxiliary loads), and charging (for EVs). This integrated model transforms passive streetlights into active energy nodes capable of bidirectional power flow, grid support, and emergency backup.
One of the study’s key contributions lies in its meticulous analysis of system architecture. The authors explore voltage selection, grounding strategies, and network topologies tailored to urban lighting applications. Drawing on national standards such as GB/T 35727–2017 and T/CECS 705–2020, they advocate for a 220 V DC nominal voltage as the optimal balance between safety, efficiency, and compatibility with existing LED products. At this level, the system avoids the heightened electrocution risks associated with higher DC voltages while still enabling practical transmission distances—up to 400 meters without excessive voltage drop—making it suitable for typical city blocks.
Grounding, a critical yet often overlooked aspect of DC safety, receives particular attention. The team evaluates three standard configurations—TT, TN-S, and IT—and concludes that the IT (isolated with high-resistance grounding) system offers the best compromise for public lighting. In an IT setup, a single-pole ground fault does not immediately trip the system, allowing continued operation while alerting maintenance crews—a crucial feature for ensuring uninterrupted nighttime illumination in critical zones. Moreover, this configuration minimizes fault currents, reducing the risk of fire and electric shock without relying on commercially immature DC residual current devices (RCDs), which remain scarce in the market.
The economic case is equally persuasive. The researchers model several deployment scenarios along a representative 1-kilometer urban corridor equipped with 160 streetlights. In a basic DC retrofit—replacing legacy AC lamps with modern LEDs and switching to a DC distribution backbone—they estimate a 20% reduction in energy consumption. At an electricity rate of ¥0.75/kWh, this translates to annual savings of over 28,000 kWh and nearly ¥21,000 in reduced utility bills. Crucially, the switch also cuts cabling costs: DC systems require only two conductors instead of the three or five used in typical AC setups, yielding an immediate ¥100,000 savings in materials for the modeled segment. The combined hardware and installation investment pays for itself in under three years.
But the real innovation unfolds when storage and solar are added. In a DC + battery scenario, the system leverages time-of-use electricity pricing to charge during off-peak hours (¥0.55/kWh) and discharge during peak periods (¥1.20/kWh). For a 100 kW/500 kWh lithium-ion system, this “peak shaving” strategy saves an additional ¥24,000 annually. While the payback period stretches to over 16 years for lithium batteries, it drops to just over eight years with lower-cost lead-acid alternatives—still a viable proposition when factoring in the added value of emergency backup during outages.
Integrating photovoltaics further enhances the economics and sustainability. The study assumes a modest 50 Wp solar panel per pole—easily mounted on the luminaire housing or adjacent structures. With eight hours of effective sunlight daily, each unit generates 0.4 kWh, offsetting grid consumption during daylight and storing excess for nighttime use. At peak tariff rates, this yields ¥175 in annual savings per pole, with a simple payback of less than five years. Multiply this across thousands of poles, and the cumulative impact becomes substantial.
Perhaps the most forward-looking application is the fusion of DC streetlights with EV fast chargers. As urban EV adoption accelerates, range anxiety and charging deserts remain persistent barriers. By embedding 60 kW DC fast chargers into smart poles—powered by the same DC bus that runs the lights—cities can rapidly expand charging infrastructure without costly grid upgrades. The study estimates that with just 10–20 daily charging sessions, a single unit can generate ¥82,000–¥220,000 in annual revenue, recouping its ¥100,000 investment in as little as five months.
This “pole-as-platform” concept aligns perfectly with China’s broader smart city ambitions. Beyond lighting and charging, these poles can host environmental sensors, 5G small cells, traffic cameras, digital signage, and emergency call systems—all powered by the same efficient DC backbone. The result is a leaner, more resilient urban nervous system that reduces visual clutter, lowers maintenance overhead, and creates new revenue streams for municipalities.
Real-world validation is already underway. Pilot projects in Shenzhen’s pedestrian districts and the Xiong’an New Area’s Citizen Service Center demonstrate the feasibility of DC smart lighting at scale. These installations not only validate the technical assumptions but also provide valuable operational data on reliability, user behavior, and system interoperability.
Nevertheless, challenges remain. As the authors candidly acknowledge, the DC lighting ecosystem is still in its demonstration phase. Standardization is incomplete, product specifications vary widely, and supply chains for key components—especially DC-rated breakers and controllers—are underdeveloped. Regulatory frameworks for grid interconnection, safety certification, and tariff structures for distributed generation also lag behind technological capabilities.
Moreover, successful deployment hinges on cross-sector collaboration. Utilities, lighting manufacturers, EV charging operators, and municipal authorities must align on technical standards, ownership models, and revenue-sharing mechanisms. The paper calls for policy support—such as subsidies for early adopters, streamlined permitting, and updated building codes—to accelerate market maturation.
From a global perspective, China’s push into DC street lighting could set a precedent. As cities from Los Angeles to London seek to meet net-zero targets, the lessons from Beijing and Tianjin offer a replicable template. The core insight is this: decarbonization isn’t just about swapping fossil fuels for renewables; it’s about rethinking how energy is distributed, managed, and consumed at the edge of the grid. By starting with something as fundamental as a streetlight, engineers can ignite a cascade of innovation that touches transportation, communications, and public safety.
In closing, Liu and his team position DC-powered streetlights not merely as an energy efficiency measure, but as a foundational element of the next-generation urban energy internet. Their work bridges engineering rigor with practical policy insight, offering a roadmap that is both technically sound and economically viable. As the world races toward the 2030 and 2060 climate milestones, such integrated, infrastructure-led solutions will be indispensable.
By Jianwei Liu (China Power Engineering Consulting Group Co., Ltd.), Kan Wang, Xuebin Li, Xiaoou Liu, Hao Zhao, Jian Liu, and Wanwei Xu (China Energy Engineering Group Tianjin Electric Power Design Institute Co., Ltd.), published in Zhaoming Gongcheng Xuebao (Journal of Illuminating Engineering), Vol. 35, No. 4, August 2024. DOI: 10.3969/j.issn.1004-440X.2024.04.020.