DELTA: Living Lab for the Energy Transition in Darmstadt
Connecting the Energy System of the City

Cities could be so much more energy efficient: waste heat produced by industrial plants, for instance, could be used to heat buildings in place of fossil fuels. DELTA, the newly launched living lab for the energy transition, is now looking to implement such energy-saving ideas – initially aiming to make the city of Darmstadt’s energy system more flexible and environmentally friendly.

Cities have high energy densities and a range of complex energy flows. This urban energy system is therefore of particular relevance to Germany’s climate change goals. The energy transition would be much simpler to achieve if it could be started from scratch on undeveloped greenfield land. However, the reality of the situation involves starting with existing residential buildings, industrial plants, mobility infrastructure, and energy grids, and taking into account the requirements of current stakeholders and the resulting energy consumption. Is there a way of optimizing such energy systems to ensure that cities can actually take the next step in the energy transition?

To answer this question, several stakeholders that have already implemented successful innovations have come together in Darmstadt to work on the regulatory sandbox project DELTA. These include large-scale industrial companies, small- and medium-sized enterprises, start-ups, municipal enterprises, and research institutions – all coordinated by TU Darmstadt. The work packages of this new living lab draw on the success of the university’s ETA-Fabrik project. DELTA, which stands for the Darmstadt Energy Laboratory for Technologies in Application, is set to become a showcase for urban energy transition through interconnected, energy-optimized districts. The project has lofty ambitions: as a living lab, DELTA aims to play a pioneering role and obtain results that can be put into practice in other cities.

DELTA launches with seven subprojects

Methodological and technical approach of DELTA, a regulatory sandbox for the energy transition © PTW, TU Darmstadt | Methodological and technical approach of DELTA, a regulatory sandbox for the energy transition

The researchers follow a bottom-up approach in three stages, all of which pursue the aim of reducing CO2 emissions. First of all, they seek to implement energy-saving subprojects in various districts. The aim is to then interconnect and optimize these subprojects. To maintain a focus on optimization and the efficient implementation of cross-cutting activities right from the start, the seven subprojects will be scientifically and technically linked through joint project management as opposed to being pursued on an individual level. This ensures that when it comes to planning the subprojects, they are focused on the common goal of an optimized urban energy supply from the outset. The launch of the interconnected district systems, and any final improvements to the systems, are to be completed by the end of the project in 2026.

Cities are comprised of many individual types of district. The DELTA project focuses on both residential and industrial districts. These districts differ, for example, in terms of their mobility requirements, energy infrastructure, development of energy usage over time, and useful energy requirements. Intelligent sector coupling might result in conventional energy carriers being displaced from the energy system.

The DELTA subprojects are focused on energy-optimized residential districts, the utilization of industrial waste heat, decentralized electrolysis, flexibility in medium-voltage grids, low-emission mobility, and non-technical innovations. They will be interconnected in practice with pipelines and storage systems for heat, electricity, gas, and hydrogen, and the grids will be operated using digital methods.

The animated film below provides an initial overview of the project:

Reducing CO2 emissions by 14,500 tonnes per year

The DELTA team estimates that it will be able to reduce CO2 emissions in Darmstadt by approximately 14,500 tonnes per year in the long term. This roughly equates to the entire carbon footprint of more than 1,600 people, or one percent of the population of Darmstadt. In addition, the energy flexibility potential is set to increase by 4.6 MW, thus enabling the further decarbonization of the electricity supply. This flexibility in terms of individual energy producers and consumers is required to integrate volatile energy sources (e.g. wind and solar power) in the grid and compensate for them whenever they supply particularly large or small amounts of energy. Hydrogen storage and battery storage are useful in this respect. In addition, consumers who draw on the electricity supply at the right time or who change their energy requirements also have a role to play. An example of this would be electric car charging stations that are able to adapt to the current level of energy supply.

Scaling up after the project is completed could see the reductions in CO2 emissions rise to 25,000 tonnes per year and the flexibility potential increase by up to 12 MW. 

In addition to the increase in energy efficiency, the regulatory sandbox aims to ensure that innovative business ideas go on to become economically viable business models. In doing so, it aims to exhaust the possibilities of existing legal frameworks and identify any additional scope for action in terms of regulations.

Subproject 1: Energy-optimized residential district

Part of the DELTA project will involve an energy- and resource-efficient residential district with an interconnected energy system. Energy will be provided from solar installations, among other sources. © ISM+D, TU Darmstadt | Part of the DELTA project will involve an energy- and resource-efficient residential district with an interconnected energy system. Energy will be provided from solar installations, among other sources.

A new urban district for around 3,000 people, Ludwigshöhviertel, is to be built on the site of two former US army barracks. The city of Darmstadt aims to create a nearly zero energy district and to provide affordable housing.

The use of waste heat and geothermal energy (via a central geothermal probe field) as low-emission sources of heat should be sufficient for heating energy-optimized buildings. Support will be provided by heat pumps and hybrid PVT collectors that combine photovoltaic cells with solar thermal power. Any additional electricity produced can be used, for example, to supply a car park with battery storage systems and charging points for electric cars. Local operators will thus be able to develop new business models, while residents will also profit from energy data visualization and sharing opportunities.

The CO2-optimized planning of the district will not only focus on operation, but also on construction and deconstruction. The use of recyclable building components will also help to reduce CO2 emissions, as will the centralized heating supply. Once all these measures have been accounted for, there is the potential to save over 1,000 tonnes of CO2 per year. The centralized heating supply with heat pumps, as well as the decentralized use of PV battery storage systems and charging infrastructure also offer considerable potential for flexibility.

The project partners aim to use the existing network infrastructure as efficiently as possible. The use of the tram power supply system for fast-charging infrastructure is conceivable, for example. One district storage system could supply an additional 250 kW of charge/discharge capacity to further increase flexibility. 

Subproject 6: Conservation of resources through urban sharing models

DELTA’s focus goes beyond technical innovations that utilize networks more efficiently; for example, the “sharing economy” offers considerable potential for saving energy. The sharing economy is a social movement that pursues the joint use of goods manufactured in an energy-intensive manner in order to reduce climate-damaging emissions. Electric scooters, for instance, have shown how just a few units can be sufficient for use by many people. This helps to save on manufacturing resources and increases the rate of utilization.

A “sharing hub” on the Lichtwiese campus of TU Darmstadt and two additional “sharing points” in the city of Darmstadt serve as central meeting points and handover locations for digitally arranged physical sharing processes, for example as a location where technical devices are available for rent. In addition, they streamline the range of services on offer and as mobility hubs they enable car sharing projects, for instance, which help to reduce the volume of traffic and emissions. 

Subproject 7: Technology scale-up

DELTA also involves start-ups whose innovations are a good fit for the project objective and whose fresh ideas can help in achieving this objective. Kraftblock, for instance, is a start-up that has developed a thermal energy storage system, which – as a large central heating plant – is able to utilize waste heat and thus replace the use of natural gas for multiple residential units. The founders of the start-up had previously lacked the opportunity to demonstrate the capabilities of the storage system in a real-world environment. Through the DELTA project, the aim is for the technology to find widespread application.

Additional innovations include an intelligent window handle that could reduce natural gas requirements in older buildings by 20 percent and an intelligent radiator thermostat that could lower heating energy requirements of schools and town halls by more than 30 percent.

Overlapping activities united by three clusters

DELTA’s additional project work is organized into three clusters that unite the overlapping activities of the subprojects. They combine aspects of digitalization, evaluate project progress, and serve to disseminate information and results.