In terms of heating, insulation and CO₂ emissions, the conventional energy certificate still conceives of buildings as they were in the old days of big power plants and oil-fired boilers. All that matters is how much energy a building requires. "But when the house uses this energy and whether the consumption can be postponed to another time aren't taken into account," explains Sönke Nissen, Project Manager Innovation at DIN. This is because in the traditional energy landscape there was no need for this information.

As soon as a new technology becomes more widespread, institutions such as DIN, the European Committee for Standardization (CEN) and the International Organization for Standardization (ISO)  get to work on defining common terms and standards, otherwise nowadays cars could not be manufactured in German automotive plants with screws made in China, the internet would not work across borders because of the need to switch to a different code, and every country would have its own frequency on the power grid. The standardisation of products and processes is the logical result of industrialisation and globalisation. The first standards date back to before 1800. Today, they are everywhere and so we no longer even notice them.

Nissen's innovation department at DIN collaborates on national and European research projects with a view to immediately plugging the gaps that are being opened up all the time by technological progress.

In the energy industry, the challenge is to develop a common language as early as possible, whether to ensure the networking of sectors, to deal with the constantly growing number of new market players and generation systems, or to bring about the integration of other applications such as smart meters or storage facilities. In this way, innovations can be marketed as quickly as possible.

The energy certificate that is valid today has its origins in a standard that was developed from around the early 2000s: DIN V 18599. "With the gas and oil heating installations of that time, the energy system didn't need to know when the units were in operation," Nissen explains. That is why such issues were not covered by the standard.

But times have changed: most new detached houses in Germany already have heat pumps, while 1.7 million buildings across the country have solar panels on their roofs, and many have large hot-water storage tanks. Moreover, local heat networks are increasingly taking over the role of supplying entire neighbourhoods. At the same time, large wind farms are supplying electricity when the wind is strong enough. Unlike in the past, today's energy supply fluctuates over time.

The process starts with researching the standards that already exist – and there are a lot of those. Nissen's list of all the relevant standards contains 528 entries. From DIN V 44570-60531 (Household electric thermal storage room heaters) to VDI 2164 (PCM [i.e. phase-change material] energy storage systems in building services) and ISO/IEC 13273, which sets out common international terminology for energy efficiency and renewable energy sources.

Another of these existing standards is DIN V 18599 for assessing the energy efficiency of buildings, and therefore their energy certificate. "That standard is crucial for decisions on whether to provide financial assistance for new buildings and renovations, because support from the State is largely based on energy efficiency," explains Simon Hinterholzer, who is in charge of the development of DIN SPEC 91410-2, relating to the identification and assessment of flexibility in urban neighbourhoods, at the Borderstep Institute for Innovation and Sustainability in Berlin. In the future, this new DIN SPEC could see the flexibility of buildings join the set of criteria for building funding, or allow operators of virtual power plants to get a quick overview of the flexibility a building can deliver.

For the DIN SPEC to pass its reality check, the 'flexibility properties' specified there were checked in the field, specifically by looking at 13 houses in Schleswig-Holstein, two houses in Hesse and a neighbourhood with over 220 apartments in Berlin.

In particular in the Schleswig-Holstein municipality of Friedrich-Wilhelm-Lübke-Koog by the North Sea, this showed what the interplay of houses' heat supply with wind power can do for the energy system.

The 'Wind and Heat' model region was officially launched there in April 2019. In this North Frisian municipality, intensive use has been made of wind power for decades, with, according to the mayor, Europe's first wind farm being constructed behind the North Sea dike back in 1991, and today most members of the community having a financial stake in the surrounding wind turbines. Unlike in the past, however, nowadays the wind turbines are regularly 'shut down' because the lines carrying the power southwards are congested when there are strong winds. With a view to harnessing this electricity, 13 houses' heating systems were expanded as part of the Wind and Heat project. The heating systems were fitted with larger hot-water tanks comprising electric heating cartridges, similar to an immersion heater. These heating elements are switched on by means of a signal from the grid operator, at times when wind energy generation at the nearby community wind farm would otherwise be curbed via feed-in management. "During 2020, surplus wind power was used in a targeted way to help with heating the homes. This reduced their fossil-fuel consumption and led to fewer turbine shutdowns," explains Hinterholzer.

Here and in the other projects, the data collection sheets trialled for the DIN SPEC relating to flexibility in urban neighbourhoods proved their worth. The extent of the projects' CO₂ savings and the effectiveness of the flexible control for the energy system will only become apparent when the results are evaluated in 2021. But Hinterholzer is optimistic about their potential. "In the second phase of the energy transition, flexibility in the energy system will be vital. Although this cannot be easily quantified, it is only possible to develop it in a meaningful way using evaluation criteria. The new DIN SPEC provides a good approach to enable this to be used in buildings and neighbourhoods as well."

The Intelligent Energy Showcase (SINTEG) funding programme run by the German Federal Ministry for Economic Affairs and Energy (BMWi) launched five joint projects, four of which developed their own flexibility platforms. On these, operators of facilities such as battery storage facilities, cooling systems and electrolysers make offers to power-grid operators to postpone their electricity consumption to a favourable period. That usually means times at which a lot of electricity is being generated by wind and solar energy, when there is a risk of power grids being overloaded and renewable energy systems being switched off.

Up to now there have been no standards for integrating systems into grid congestion management on a voluntary basis.

In SINTEG, the individual joint projects initially developed their own flexibility platforms based on their regional circumstances. The lessons learned in the subprojects come together in DIN SPEC 91410-1. This standard thus forms a basis for laying down uniform requirements for providers on flexibility platforms on the German grid.

Specifically, the DIN SPEC sets out in this connection the access requirements for suppliers, the process for the submission and acceptance of bids, the time periods, the information and the interface and data structures needed and data protection requirements. In this way this DIN SPEC can be used as a potential blueprint for prospective flexibility trading platforms.

Regardless of whether you are looking at the energy system of a single home, a big city or a country like Germany, such a system's performance depends on its environmental impact, the costs and the reliability it offers. For example, an energy supply based purely on coal and oil could be regarded as very reliable in one model but a very poor option in terms of costs, import dependency, climate protection and the environment. On the other hand, a system solely using renewables that is introduced very quickly would be a strong performer in terms of the environment and the climate, but could find itself at a disadvantage in terms of security of supply and land use.

In a bid to establish a level playing field for evaluating different energy systems, DIN SPEC 91432 was developed as part of WindNODE. This provides the framework for a multi-criteria assessment – i.e. one that includes an adequate set of ecological, social, economic and security/safety-related aspects.