Why the Next Generation of Cities Will Be Built on Solar
In 2019, at the Global Green Finance Summit in London, a Swiss venture capital firm called 5D Solar City AG was invited to present. The company had spent three years studying something most energy firms had not considered worth studying: what happens when you stop trying to add solar panels to cities that were never designed for them, and start designing cities around solar instead.
The difference matters more than it sounds.
The Retrofit Trap
Every major European city was built on assumptions about energy that no longer hold. The street widths, the grid connections, the building orientations, the planning codes — all of it was laid down in an era of centralised fossil fuel generation. Coal, then gas, then nuclear. The infrastructure assumes that power comes from somewhere else and gets delivered through cables.
Solar does not work like that. Solar is distributed. It is generated where it is consumed. It responds to geography, to orientation, to the angle of a roofline. Bolting it onto infrastructure designed for an entirely different energy model is like trying to run a modern operating system on hardware from 1985. It functions, but barely, and at enormous cost.
Planning permissions. Grid capacity constraints. Listed building restrictions. Heritage objections. Every rooftop installation in London or Paris or Rome is a small battle against the built environment. The result is that solar in developed cities remains marginal — a supplement, not a foundation.
750 Hectares in Zanzibar
The Zanzibar Investment and Promotion Authorities offered 750 hectares on a long-term lease. The land was undeveloped. No existing grid to fight. No listed buildings to navigate around. No fossil fuel infrastructure already in the ground demanding to be used.
Solar Smart City Zanzibar Limited was incorporated in December 2021. The pre-feasibility report — which had taken three years to complete — outlined something unusual: a city where the energy system came first and everything else followed. The urban plan, the building orientation, the grid architecture, the financial model. All shaped by the sun.
The project was designed to match all 17 United Nations Sustainable Development Goals. Not as a marketing claim bolted on afterwards, but as a structural constraint written into the financial model from day one. Thirty percent of the project company's shares were allocated to Zanzibari entities — the National Social Security Fund, educational foundations, youth organisations. The feasibility study noted that almost 100 percent of the value added would remain in the country. That indicator, the authors wrote, is very rare in the world and essentially unseen in Africa.
The Urbanisation Arithmetic
The International Energy Agency projects that by 2050, the equivalent of a new Paris will be built every single week. The overwhelming majority of that construction will happen in Africa and South Asia. Those cities do not exist yet. Their roads have not been paved. Their power stations have not been commissioned. Their energy systems are, right now, a choice that has not yet been made.
Every one of those cities built around diesel generators and imported gas is a city that will need an expensive, disruptive energy transition in twenty or thirty years. Every one built around solar will not. The window in which this choice can be made cheaply — before the concrete is poured and the grid is laid — is open now. It will not stay open.
Bulgaria, and the Modular Model
The European flagship is called Pegasus. It sits north of Sofia, Bulgaria. First phase: 102 hectares. Four thousand residential units. Eight hundred affordable units for young professionals. A fintech hub. Education facilities. Data centres. Solar manufacturing workshops — over fifty green industrial enterprises. Smart agriculture. Sports infrastructure.
The master plan is modular. Each development block can be financed, constructed, and operated independently. An investor does not need to fund an entire city. They fund a block. The block generates returns. The returns fund the next block. The city assembles itself piece by piece, each piece viable on its own.
Design requests have since arrived from Tanzania, Zimbabwe, Italy, Cyprus, and Malta. The model travels because the physics are universal. The sun shines in Zanzibar and it shines in Sofia. The cost curves for solar generation and battery storage have fallen ninety percent in a decade and are still falling. The constraint was never the technology. The constraint was whether anyone would design a city around it.
What Comes Next
Most of the conversation about clean energy still centres on retrofit. Better insulation for Victorian terraces. Heat pumps replacing gas boilers. Charging points squeezed into streets designed for horses. These are necessary projects. They are also, fundamentally, projects of compromise — negotiating with infrastructure that was built for a different century.
The Solar Smart City programme represents something else: the chance to build it right the first time. 5D Solar City AG, founded in Lugano with an asset management office in London, has spent the better part of a decade developing this model — from feasibility studies to government partnerships to real projects on real land. The leadership team came to this work through property management and international development, not through the energy industry, which may explain why the approach looks different from what the energy industry typically produces.
The cities of 2050 are being designed now. The question is not whether they will be built. The question is what they will run on.
This article is for general information only and does not constitute legal advice. Always seek independent legal advice for your specific circumstances.