Energy Supply in Buildings and Districts
The research on energy-optimised buildings and districts is focussing on efficient and, at the same time, economic supply structures. Systemic approaches instead of individual solutions are required to progress sectoral coupling and digitisation and to significantly reduce primary energy requirements throughout the system through the integration of renewable energies.
For the heat supply system, this involves increasing the efficiency of energy converters through technological development, expanding renewable energies, adapting the transfer systems to low-exergy systems and integrating the heat supply systems into gas, electricity and heating networks.
Current research projects support the goal of improving decentralised energy supply technologies in primary energy, economic and ecological terms. This applies in particular to heating and cooling technologies, cogeneration systems, distribution networks and transfer stations. In addition, heating and cooling systems with innovative concepts for waste heat utilisation, multiple feed-ins and thermal storage are being tested and optimised.
Energy-efficient and economical energy systems play an important role in the supply, distribution, storage, and use of energy. They supply both individual properties and urban districts with electricity and heat. As renewable energy is finding increasing use in this context, these systems are becoming increasingly dynam-ic and diverse. Short-term fluctuations in renewable energy production need to be offset by a large number of small, geographically distributed systems. At the same time, the electricity, heating, and gas supply sec-tors as well as production and mobility are becoming increasingly integrated.
As a result, to optimize an energy system, it is not sufficient to consider just one sector. The various energy sectors are closely linked by energy generation units and consumers, leading to a high level of complexity in the analysis, optimization, and operation of energy systems.
With the continuously rising share of renewable energies in the energy supply system, energy storage systems for electrical and thermal energy are becoming increasingly important. If electricity is converted before it is stored, for example into hydrogen or other chemical energy sources, this energy can not only be later re-electrified but also used in other energy industry-related sectors and thus for the much-needed coupling of the various sectors.
Heat storage systems can be used for integrating renewable energies, especially in combination with solar thermal heat for space and domestic hot water heating in buildings as well as for industrial processes. Renewable electricity from photovoltaics and wind energy can also be stored by converting the electricity into heat (power-to-heat). Thermal energy storage systems can therefore be used to shift the demand for heating and cooling energy. They can also increase the overall efficiency when generating electrical energy, for example by storing the waste heat from CHP plants.
It is not just the condition of the building envelope and building materials used that has an impact on the energy efficiency of buildings and districts. In addition to structural aspects and user behaviour, optimised operation and the improved energy management of both building energy systems and heating and cooling networks offer considerable savings potential. Modern methods for optimising the operational management of buildings have long been a subject of research. New requirements arise through the necessary optimised integration of plants in energy systems for supplying districts – for example, efficient cooling plants and heat pumps.
In larger building complexes, energy savings of up to 30 per cent can be achieved through just using control-based optimisation measures. A current research theme is therefore the online operation monitoring of complex buildings and properties – automated and linked to the building management systems. This helps to identify and correct malfunctioning individual technical components and problems in the operation management.
Load management relates to measures for optimising energy consumption. Through targeted management of the energy consumed by buildings, districts or companies, load peaks can be reduced, load profiles harmonised and, through optimised utilisation, the price per kilowatt can be reduced. Smart control systems and control technology are required for this. Predictive methods can support this process. The consideration of an entire district, i.e. coupling several buildings to form a network, can additionally increase the economic efficiency of such concepts.
In contrast to heat recovery, the waste heat generated in one process is transferred to other processes during waste heat utilisation. However, heat is not just heat. Here is it concerned with how and where waste heat can be used, what temperature levels are usable and the possibilities with combined heat and power (CHP).
A large range of modern technologies are available for successfully integrating industrial waste heat: In addition to direct integration within operational processes, the waste heat can be used at a high temperature level in other processes, as well as for space and domestic hot water heating. Furthermore, the waste heat can be converted into other forms of useful energy such as cooling energy or electricity – using already technically mature and economically viable technologies such as steam processes and ORC systems. Research is therefore focussing less on new technological developments and more on the conceptual integration of waste heat potential into supplies for urban districts and the design of local waste heat network systems.