The research team, led by Jingchun Shen and Xingxing Zhang, built detailed urban energy models of three case-study districts using the City Energy Analyst framework, supplemented with geospatial data from OpenStreetMap and refined in QGIS. The Amsterdam site comprises thirty-five boathouses along the Stadhouderskade canal, hemmed in by street trees and taller neighboring buildings. The Riga district, Daugavgrīva, contains eight mid-rise apartment blocks, a kindergarten and a grocery store. The Borlänge site in Sweden consists of ten low-rise, two-storey houses in the Rymdgatan community. These contrasting morphologies, the authors argue, are precisely what determines whether solar integration can realistically push a district toward net-zero operation.

To capture the influence of climate change, the team generated future weather files for 2050 and 2080 by morphing baseline Typical Meteorological Year data within the CMIP5 framework, and validated the results against the newer CMIP6 SSP2-4.5 middle-of-the-road emissions scenario. The comparison showed nearly identical warming trends and almost complete overlap in solar radiation projections, giving confidence that the principal climatic drivers of building energy demand and photovoltaic generation are robust across both datasets. The projected changes are striking. By 2080, annual mean temperature rises by 3.4 degrees Celsius in Amsterdam, 5.4 degrees in Riga and 4.8 degrees in Borlänge, while cumulative global horizontal irradiance increases by roughly 57, 65 and 210 kilowatt-hours per square metre respectively.

These shifts translate into a fundamental rebalancing of thermal demand. Heating degree days, calculated against an 18-degree base, fall by 35 percent in Amsterdam, 39 percent in Riga and 49 percent in Borlänge by 2080. Cooling degree days, measured against a 24-degree base, surge by 545 percent in Amsterdam and a remarkable 646 percent in Riga, although they rise by only 88 percent in the cooler Swedish context. The study concludes that European districts are moving from heating-dominated to cooling-sensitive demand profiles, a transition that will reshape building design, urban planning and the value of solar-generated electricity, which becomes more consistently available year-round as global irradiance increases.

At the heart of the methodology is an irradiance threshold framework, a deliberately simple but powerful idea. Rather than covering every available surface with panels, the researchers tested five annual radiation thresholds, from zero to 800 kilowatt-hours per square metre per year, placing panels only on surfaces receiving radiation above each cutoff. This allows planners to trade off total energy yield against the levelized cost of electricity, calculated with a 20-year system lifetime, a 5 percent discount rate and operation and maintenance costs set at about 1 percent of annualized capital expenditure. The team also ran sensitivity analyses using a solar learning rate of 24 percent, drawn from Berkeley Lab data on utility-scale photovoltaics, meaning each doubling of cumulative installed capacity reduces costs by roughly a quarter.

The results expose three distinct structural archetypes. Amsterdam’s boathouse district is demand-dominated: high density, heavy shading from adjacent buildings and trees, and severely limited envelope area mean that even with unrestricted panel placement, on-site photovoltaics would cover only 29 percent of current electricity demand, falling to 17 percent by 2080 as consumption climbs 48.3 percent. The recommended irradiance threshold is therefore the lowest tested range of 0 to 200 kilowatt-hours per square metre per year, and the authors argue that Amsterdam’s decarbonization must rely on multi-vector strategies, including higher-efficiency technologies, rooftop integration, flexible storage and an active role for distributed solar in grid decarbonization rather than local self-sufficiency alone.

Riga presents a balanced-to-surplus profile. Mid-rise buildings with favorable façade exposure and moderate density allow photovoltaic generation to exceed annual demand across all scenarios, with demand coverage ranging from 170 to 270 percent. Here the economics favor selectivity: the levelized cost of electricity, ranging from 0.18 to 0.36 US dollars per kilowatt-hour at baseline, reaches its minimum at an irradiance threshold of 600 kilowatt-hours per square metre per year, where self-consumption approaches 55 percent. Under moderate and strong technology-learning scenarios, costs fall by 30 to 50 percent, expanding the range of economically viable installation sites. The authors note that such surplus districts create opportunities for grid export, storage and sector coupling, but also warn that rising shares of variable generation reduce system inertia, requiring adapted market rules and balancing mechanisms of the kind already operating in Nordic electricity markets.

Borlänge, with its low-rise morphology, large roof and façade areas per unit of demand and minimal mutual shading, is surplus-dominated. Photovoltaic potential exceeds district demand by roughly four to five times at low irradiance thresholds and remains about three times higher even at 600 kilowatt-hours per square metre per year. The optimal threshold is 800 kilowatt-hours per square metre per year, where baseline costs of 0.13 to 0.26 dollars per kilowatt-hour reach their lowest point. Because the district is served by a low-carbon district heating network and cooling demand remains limited, total energy consumption rises only 1 percent by 2080 while solar potential grows 15 percent. The authors position Borlänge as an ideal testbed for export-oriented operations, curtailment management and grid-supportive flexibility measures under high renewable penetration.

The study also delivers a nuanced verdict on photovoltaic-thermal hybrid panels, which generate electricity and heat simultaneously. In Amsterdam, where dwellings rely on individual heating systems, the thermal output of hybrid panels directly offsets domestic hot water and space heating demand, keeping self-sufficiency ratios around 30 percent even in future scenarios. In Riga and Borlänge, however, mature district heating networks already supply most thermal demand, and projected reductions in heating needs further diminish the marginal value of additional heat, making electricity-only photovoltaics the more cost-effective choice. The technology-learning analysis adds a final insight: future cost reductions improve the absolute viability of every strategy, but the relative ranking of irradiance thresholds remains stable, confirming that solar access, installation area and demand, not economics alone, are the primary determinants of district-scale solar success.

Subject of Research: Techno-economic assessment of district-scale solar energy integration in three residential districts under future climate conditions

Article Title: Techno-economic assessment of district-scale solar energy integration in three residential districts under future climate conditions

Article References: Shen, J., & Zhang, X. (2026). Techno-economic assessment of district-scale solar energy integration in three residential districts under future climate conditions. Energy Reports, 16, Article 109698. https://doi.org/10.1016/j.egyr.2026.109698

Image Credits: AI Generated

DOI: 10.1016/j.egyr.2026.109698

Keywords: Techno-economic, assessment, district-scale, solar, energy, integration, three, residential, districts, under, future, climate