30 under 30: Engineering Hong Kong’s vertical cities

Hong Kong and Mainland China have some of the highest urban densities in the world. How does this ‘vertical’ context influence innovation?

Zhengguang Liu: In ultra-dense, vertical cities – such as Hong Kong and many Mainland China megacities – conventional sustainability approaches based on incremental efficiency gains reach their limits quickly.

Spatial constraints, limited roof area and tightly coupled infrastructure mean that optimising individual components is no longer sufficient. This context forces a shift in thinking: buildings must be treated as active nodes within a wider urban energy system rather than isolated energy consumers.

Much of my work focuses on how building-integrated photovoltaics and demand-side flexibility can unlock system-level decarbonisation in environments where space, capacity and redundancy are constrained.

Jill Leung: In Hong Kong and Mainland China, density and verticality push us to innovate beyond standard practice. Extremely high occupant and equipment densities require advanced load prediction, dynamic zoning and AI-assisted chiller and air-side optimisation to maintain comfort while cutting energy use.

Space constraints drive modular, prefabricated, multi-trade integrated mechanical, electrical and plumbing (MiMEP) systems that fit tight plantrooms and enable staged retrofits. Onsite renewables move beyond roofs to building-integrated photovoltaics (PVs) on façades, and hybrid PV and solar thermal (PVT) systems that provide electricity and useful heat. Micro wind turbines are also being explored.

Tsz Kai Charles Lam: Vertical city conditions have pushed us to design sustainability as a three-dimensional, operational discipline – where plant, air paths, controls, logistics and user behaviour must work together at height, speed and scale.

In that context, innovation is less about inventing new standards and more about re-engineering how international best practice is applied to dense, mixed-use towers and campuses with long operating hours and complex stakeholder interfaces.

In ultra-dense districts, we cannot treat buildings as isolated assets; we have to optimise clusters such as shared central plants and district energy interfaces, and we need resilient maintenance strategies that work in constrained plantrooms and vertically distributed risers.

That ‘stacked’ complexity forces earlier, more integrated decisions: separating sensible vs latent cooling demands, and designing for 24/7 tenancy diversity (for example, retail, offices and serviced apartments in one tower). Retrofit phasing has to be planned carefully so that decarbonisation happens without disrupting business continuity.

Building services in the region are dominated by cooling and humidity challenges. What is the biggest hurdle to achieving true net zero in a subtropical climate?

Zhengguang Liu:  The biggest hurdle is not cooling demand itself, but the rigid coupling between thermal comfort, humidity control and conservative operational strategies. In humid subtropical climates, maintaining wellness often locks systems into inflexible modes of operation, leaving little room for optimisation. My research explores how thermal storage, system inertia and predictive control can decouple when cooling is generated from when it is used. This allows energy use, carbon emissions and comfort to be optimised simultaneously, rather than forcing trade-offs that undermine performance or wellbeing.

Jill Leung: The biggest hurdle is managing rapidly rising cooling and dehumidification loads without over-reliance on energy-intensive systems. Climate change is increasing temperature and humidity, which drives up latent and sensible loads, and lowers equipment efficiency. To approach true net zero, we must dissect cooling load components rigorously, then reduce demand through façade optimisation, airtightness, moisture control and heat recovery. In parallel, we must promote behaviour change via green tenancy and incentive schemes, and encourage acceptance of higher setpoints. This load reduction underpins efficient, wellness-focused system design.

Tsz Kai Charles Lam: The biggest hurdle is latent load. We have to remove moisture safely and efficiently during long operating hours, without overcooling or compromising indoor air quality and comfort. Research focused on Hong Kong shows the latent portion can dominate ventilation cooling load (reported around 80% in one study) and it is highly sensitive to outdoor moisture, making dehumidification energy a core barrier to ‘true’ net zero in our climate.

How are we moving from using data as a mere ‘monitoring tool’ to using it as an active ‘decarbonisation engine’ in building services?

Zhengguang Liu Data becomes a decarbonisation engine only when it changes the engineering paradigm, not merely the interface. Rather than using data to validate fixed design assumptions after the fact, data-driven models can be used to challenge them continuously.

In my work, this approach reveals latent flexibility across buildings, thermal systems and grids that rule-based operation cannot capture. By combining data with physical system understanding, engineers can move from compliance-orientated practice to adaptive, system-level optimisation, where carbon, comfort and energy are treated as co-evolving variables rather than static constraints.

Jill Leung We can shift from passive monitoring to active decarbonisation by turning raw data into engineered insight and automated action. The rapid expansion of the internet of things has created a data explosion, so our first priority is robust data governance, including sensor specification, calibration and validation.

Development of physics-based models and key performance indicators could relate data to real plant behaviour, comfort and energy performance. This engineering layer allows us to identify avoidable loads, faults and optimisation opportunities. On this foundation, we deploy analytics and AI-driven control to continuously fine-tune operation, driving ongoing carbon reduction rather than one-off tuning.

Tsz Kai Charles Lam To move from data-as-dashboard to data-as-action, we must close the loop: instrument–diagnose–predict–control–verify, with governance that lets engineers implement changes quickly and safely.

Digital twin approaches are increasingly positioned not just for visualisation, but as adaptive, data-driven decision tools that use continuous sensor feedback to optimise operation in real time – shifting building services from reactive tuning to proactive carbon reduction while protecting occupant comfort.

What is one specific high-performance building technology or strategy emerging from China to which the Western engineering community should be paying closer attention?

Zhengguang Liu One of the most valuable lessons emerging from China is not a single technology, but the speed and scale of system-level integration in practice. Many projects integrate photovoltaics, thermal systems, storage and grid interaction from the earliest planning stages, treating buildings as part of a coordinated energy ecosystem.

This systems-first strategy contrasts with more fragmented approaches that optimise technologies in isolation. The key insight for the Western engineering community lies in prioritising integration and system behaviour over individual component performance.

Jill Leung One area that merits closer attention is China’s rapid development of modular integrated MEP (MIMEP) systems for high-rise projects/MEP-dominated projects, such as data centres. MIMEP adopts a modular design approach in which multi-trade services are factory assembled into standardised racks, riser modules and plant skids. This optimises scarce space, improves coordination and delivers consistent quality under controlled manufacturing conditions. Onsite installation time and interfaces are reduced significantly.

From a life-cycle perspective, modules are designed for safe access and easier maintenance. Integrated sensors at module level enhance data granularity, providing a strong foundation for advanced analytics and AI-based optimisation in operation.

Tsz Kai Charles Lam Global engineers should pay closer attention to China’s rapid scaling and localisation of ultra-high-efficiency, oil-free magnetic-bearing chiller packages (often integrated with inverter drives and smarter factory integration). They directly target the dominant cooling electricity demand in dense Asian cities.

These designs reduce friction losses and remove oil-system complexity, improving efficiency and maintenance performance. This is an attractive pathway for large existing portfolios where chiller plant upgrades deliver outsized carbon benefits.

 How can the Hong Kong and Chinese engineering sectors better empower the next generation of ‘sustainability champions’ to challenge the status quo?

Zhengguang Liu In ultra-dense, vertical cities – such as Hong Kong and many Mainland Chinese megacities – conventional sustainability approaches based on incremental efficiency gains quickly reach their limits.

Spatial constraints, limited roof area and tightly coupled infrastructure mean that optimising individual components is no longer sufficient. This context forces a shift in thinking: buildings must be treated as active nodes within a wider urban energy system rather than isolated energy consumers.

Much of my work focuses on how building-integrated photovoltaics and demand-side flexibility can unlock system-level decarbonisation in environments where space, capacity and redundancy are extremely constrained.

Jill Leung Hong Kong and Mainland China already show growing awareness of sustainable development, which gives a strong platform for the next generation. To truly empower young sustainability champions, we must emphasise that sustainability is a lifelong, evolving discipline that demands continuous learning, curiosity and critical thinking.

Design guidelines should be presented as informed references rather than fixed rules, grounded in sound engineering fundamentals. By mentoring young engineers to understand underlying physics and systems thinking, we enable them to justify alternative or innovative solutions, challenge norms, and confidently advocate for higher performance outcomes across projects and organisations.

Tsz Kai Charles Lam The sector can empower the next generation by giving young engineers real authority over pilots (decarbonisation, controls optimisation, humidity-decoupled ventilation trials, retrofit M&V), plus the mentoring and data access needed to prove outcomes and scale them.

We also need stronger cross-border practice communities – linking Hong Kong’s professional networks and governance roles with Mainland delivery speed – so young ‘sustainability champions’ can challenge design defaults and operational inertia with evidence, not just ambition.