Walk on sunshine, decide on data: a smart-city approach to solar

Power to the people – and to public assets

Cities already hold a diverse energy portfolio: a patchwork of rooftops, façades, depots, car parks, schools, hospitals, sports halls, and long corridors of street lighting. Historically, these assets were not designed to talk to each other – or to the grid. Solar shifts that baseline. 

When photovoltaics (PV) are paired with storage and intelligent controls, the city’s physical fabric behaves like an active energy layer that can generate, schedule, and exchange electricity with purpose.

The benefits show up in budgets and operations. Energy spend is one of the fastest-growing operating expenditure (OPEX) lines for municipalities. PV converts part of that bill from volatile tariffs to predictable, long-term production. 

Adding batteries and a building energy management system (BEMS) smooths peaks, steadies invoices, and creates a buffer during grid disturbances. In practice, the effect is felt in everyday services: lighting that adapts, buses that charge on time, and schools that stay comfortable without surprise costs.

The rooftops that pay their way

Public buildings emerge as a natural starting point. Most operate during daylight hours, when PV output is strongest. Schools, administrative offices, libraries, and clinics often provide usable roof area and straightforward access, supporting high self-consumption without complex export arrangements. Programs typically begin with audits of structure and waterproofing, followed by sizing of PV and storage to match the building’s load profile rather than the theoretical maximum.

Control multiplies value. A BEMS that schedules heating, ventilation, and air conditioning (HVAC), server rooms, heat pumps, and hot-water preparation around solar peaks and tariff valleys tends to lift self-consumption by double digits.

Even without batteries, orchestrating loads – pre-cooling or pre-heating buildings, aligning hospital or sports-facility routines with production windows – adds measurable gains. 

Long-term operation becomes the quiet differentiator. Municipal portfolios that standardize components, monitoring, and service-level agreements (SLAs), publish simple internal dashboards, and plan refresh cycles for inverters and batteries often see the payoff beyond spreadsheets: fewer service calls, lower peak demand, and teams spending less time firefighting energy surprises.

Poles and depots as one smart system

Mobility and lighting sit where energy, safety, and data intersect. Bus and tram depots, municipal fleets, and park-and-ride sites concentrate predictable demand, while street corridors concentrate luminaires and sensing opportunities. Together, they function as an integrated platform.

Fleets that feed on sunshine. Solar canopies over depot rows, paired with batteries and smart chargers, transform a cost center into a controllable microgrid. In many cities, deployments phase in over time: a pilot lane of 10–20 chargers is instrumented, cable trays and switchgear are sized for the end state, and resilience is framed around a critical subset of vehicles that must operate during outages. The result is a depot that charges when PV peaks, tops up at low tariffs, and keeps essential services moving when the grid is stressed.

Poles that patrol, light, and listen. Modern luminaires double as connected nodes. Adaptive dimming trims kWh; sensors – traffic, air, acoustic – feed planning and safety dashboards. Where grid access is costly, solar luminaires take the lead; elsewhere, grid-tied smart lighting with open protocols keeps maintenance simple and data flowing. A shared digital backbone – secure networking, device management, and a city data platform – supports both charging and lighting, reducing silos and duplicated spend.

Energy on the outside, stability on the inside

Building-integrated photovoltaics (BIPV) place generation on the façade while system stability remains calm inside the grid. In new civic buildings or deep renovations, façades, skylights, balustrades, and brise-soleil elements can produce electricity while adding shading, thermal comfort, and a strong visual identity. Unlike rooftop PV, BIPV displaces materials rather than stacking on top, so the case often rests on lifecycle value and public visibility, not the lowest €/W.

Early projects frequently focus on front-of-house assets – city halls, cultural venues, transport interchanges, and museums – where design carries public meaning. Architects, planners, and heritage authorities typically join early; color-stable modules, anti-reflective treatments, and concealed fixings protect the cityscape while meeting yield targets. Full-scale mock-ups reduce uncertainty on glare, texture, and mounting details. Inside, lobby displays showing real-time production and avoided emissions turn buildings into civic “energy dashboards.”

Stability flows from integration choices. Interconnections are right-sized; smart inverters provide reactive power and ride-through; generation pairs with flexibility – batteries, controllable HVAC, and thermal storage. 

Each BIPV site sits within a portfolio view

A school cluster with midday load, a sports complex with evening peaks, and an admin block with steady daytime use can flatten combined exports when orchestrated by an energy management system (EMS).

In jurisdictions where rules allow, portfolios engage with flexibility markets or demand-response programs. Even modest batteries can shift BIPV output away from feeder stress, trim demand charges, and create a steady revenue stream that offsets operations and maintenance (O&M) and inverter refreshes. For critical sites – clinics, water and wastewater, information and communications technology (ICT) hubs – resilience planning commonly defines “must-run” loads and sizes PV – battery energy storage systems (BESS) for realistic autonomy, often targeting a four-hour islanding window and testing the islanding sequence before handover.

Contracts that keep the sun shining

Financing is not one size fits all. Three models dominate municipal practice, and mixing them across a portfolio maximizes coverage.

• Capital expenditure (CAPEX) with grants works best for schools, libraries, and clinics. The city owns the asset, captures the savings, and uses national/EU funds to shorten payback. The constraint is budget cycle timing; early planning wins here.
• Energy-as-a-Service / energy service company (ESCO) shifts delivery and performance risk to a specialist who guarantees savings. Payments come from actual performance, and the ESCO handles O&M. The city needs a robust measurement and verification (M&V) plan to protect outcomes.
• On-site power purchase agreement (PPA) brings third-party investment for larger roofs, depots, and canopies. The city signs a long-term €/kWh contract, indexed and capped per local norms. PPA volume should track real load, not just roof area; designing for 70–85% self-consumption keeps economics resilient against tariff changes.

Smart city energy needs a backbone

It’s as essential as the panels themselves. Think in four layers.

Field layer – the things that make (and use) power

PV arrays, inverters, batteries (BESS), EV chargers, smart meters, and luminaires. Open, documented interfaces and secure firmware update paths are preferred, avoiding proprietary black boxes that trap data.

Site control layer – the conductor

The building/energy management system (BEMS/EMS) orchestrates assets on each site, enforces safety and islanding sequences, and exposes clean APIs (e.g., Modbus TCP, Open Platform Communications Unified Architecture (OPC UA), OCPP for chargers, MQTT/REST for telemetry). This is where schedules and tariff logic live.

Cyber layer – the guardrails

Network segregation – operational technology vs. information technology (OT vs. IT) – strong credentials and certificate management, patch policies, backups, and incident response complete the picture. Every charger, inverter, and luminaire is an endpoint, and is treated accordingly.

Across the stack, one principle appears repeatedly: interoperability by default. Procurements and pilots alike tend to test integrations in a sandbox and weigh standards conformance and data portability alongside technical performance.

The city scorecard: KPIs that matter

Programs that measure well, manage well. The most useful metrics stay short, comparable, and decision-oriented.

• Financial: annual energy cost reduction (€ and %), avoided demand charges, PPA €/kWh vs. tariff, maintenance cost per m².
• Technical: self-consumption and self-sufficiency (%), peak-load shaved (kW), charger uptime (%), lighting kWh per luminaire, islanding hours at critical sites.
• Environmental & service: CO₂e avoided (t), air-quality improvements on corridors, e-bus punctuality during heatwaves/outages, citizen satisfaction on lighting/safety.

Results often appear in a quarterly dashboard: predictability for finance, trends and alarms for operations, and progress that can be communicated clearly by city leadership.

Why start now (and where)

Early wins commonly surface where demand is predictable and roofs are ready. Schools and administrative hubs align with daytime generation and standardize quickly. Sports halls add evening demand that makes small batteries pay off. A flagship depot illustrates the concept in public view, linking solar canopies and managed charging to a service everyone recognizes – public transport. 

Many city programs begin with a school cluster and a depot microgrid on the same data platform, and then replicate district by district, with smart-lighting corridors widening the benefits beyond building walls.

Wiren in the loop

In this landscape, Wiren operates as an engineering and delivery partner focused on municipal portfolios: mapping assets and building business cases; designing and constructing PV and storage systems; integrating EV-depot microgrids and smart lighting; connecting interoperable controls and data platforms; supporting grants, ESCOs, and PPAs; and running structured O&M with clear SLAs and dashboards. 

The aim is consistent: public assets that power themselves, services that run reliably, and numbers that stay steady.