3D city models provide great tools to coordinate the different actors and initiatives around energy transition.

Consumption of the buildings of the city of Ferrara – source: Project Sunshine

They allow to compare and choose the best low-carbon strategies and then monitor their progress over the years to achieve the ultimate goal: carbon neutrality by 2050 for the France and 21 other countries (roadmap approved at the COP22).

Based on these models, the decision makers have in their hands a series of simulations and analyses interconnected, useful for each phase of the energy transition plan:

• Diagnostic predictions of energy savings and thermal needs related to the renovation of the buildings.
• identify the potential of solar energy
• integration of renewable energies,
• comparison of centralized and decentralized energy systems,
• calculation of consumption and grey energy, CO2 emissions
• estimated costs (investment and overall costs).

These analyses that apply to urban, or even regional, have a very fine granularity (each building is individually modeled realistically) and particularly reliable results if the data used are of good quality. This makes it possible to meet considerations macro (plan to scale of the neighborhood or the city, changing the energy mix) and micro (individual housing renovations, solar panels on the roof, the heating network connection).

For energy transition, the result as important as the way to achieve it. Especially for scenarios of energy renovation of buildings, the impact of different renovation rate (percentage of buildings renovated annually) as well as different priorities of renovation (depending on age, consumption of heat, the potential energy of the building, or of energy poverty) can be compared.

Finally, acceptance and involvement in this reflection of different urban actors, whose populations, is essential. Different collaborative tools to become immersed in these 3D city models and thus visualize the energy transition can be used: touchtable, 3D, etc. augmented reality web interface

Prerequisite: Model town 3D (LoD2 at least), data on the energy state of the buildings and systems.

Initiatives & contacts

Territory of the County of Ludwigsburg climate energy plan

• Klimaschutzkonzept (map energy climate territory) of the 32 municipalities of the County of Ludwigsburg (500,000 inhabitants)
• Partners: HFT Stuttgart, Drees & Sommer, Landkreis Ludwigsburg
• Contacts: Volker Coors, New Roman (HFT Stuttgart).

Rotterdam:

• Estimated needs of heat and CO2 emission scenarios of renovation of ~ 1000 buildings of the district Bospolder of Rotterdam (report).
• Partners: HFT Stuttgart, City of Rotterdam
• Contacts: New Roman, Volker Coors (HFT Stuttgart)

The urban heating network extension or planning process usually begins with an analysis of the potential of heat need. Follows the route of the network generally to rule along main streets. Then comes the concept of heat production which will cover the needs (with a comfortable overdesign factor), to finish on optimization at all and in particular costs.

This process (almost) – Centennial is still very fragmented, mixing calculation tools very various, management of "semi" data, decisions to the wet finger based on experience. CEL in addition to strangers such as: what proportion of households will connect to the network? What proportion of buildings will be renovated (and will therefore see their need of heat declined drastically) the next years? The application of heat will be always strong enough along the network? Because of this complexity, operators of heating network is limited to city centres, if possible close to buildings energy efficient, to ensure their profitability. While several projects have proved their profitability to connect neighborhoods of low-energy and passive houses.

The 3D city models represent a new generation of tools for planning, more automatic and integrated than the traditional method, able to find optimum solutions to the problems.

City CityGML models include in particular models of buildings, land and underground, transport (if not importable from openstreetmap) and soon the models of urban networks (Thematic Module UtilityNetwork coming in the new version of CityGML 3.0). 3D allows to precisely model the path of the network in the basement, taking into account the other underground networks as well as the local geology.

By combining thermal needs geo-localized calculated precisely for each building, a digitized street map and a few parameters cost and constraints of felt (for a slice along a street, the route of a private field or a cellar etc.), and by turning the whole with a graph theory algorithm coupled with a software professional sizing and simulation of heat networks , it will be possible to generate automatically a trace and dimensioning of heating network optimized. From there, many variations are possible: simulation of different rates of connection, of different scenarios for building renovation, intensification in the medium term, criteria for connection etc… the possibilities are endless.

Prerequisite: 3D city model LoD1/LoD2, model field, data network if existing (plan, temperature etc…)

Initiatives & contacts

SIMSTADT, urban energy simulation platform

• Partners: HFT Stuttgart, GEF, MOSS
• Contacts: New Roman, Eric Duffy (HFT Stuttgart).

Platform AixLib (Germany)

• Developer: RWTH Aachen – E Research center
• Contact: Moritz Lauster