INES – Institute of Sustainable Energy Systems

The lab for Applied Control Engineering and Building Automation is equipped with a practical ventilation and air-handling system (HVAC system) featuring an integrated climate control and conditioning unit. The system allows for the targeted creation of defined outdoor and operating conditions and is fully integrated into a modern building automation environment. For experiments, a single room can be specifically isolated from the rest of the building structure and climate-controlled independently. This enables the investigation of control engineering issues under reproducible and realistic conditions.

Automation is handled by a freely programmable Direct Digital Control (DDC) system with field devices, interface modules, sensors, and actuators, as well as a higher-level building management system. Comprehensive capabilities are available for measurement data acquisition, trend recording, parameterization, and visualization of system states. The laboratory facility is suitable for both fundamental control engineering investigations and application-oriented experiments in the field of building automation.

Typical laboratory experiments:

• Investigation and parameterization of temperature control systems in ventilation systems (supply air, room air, and cascade control).

• Analysis and comparison of P and PI controllers, including controller tuning according to standard methods (e.g., Ziegler-Nichols, Chien-Hrones-Reswick).

• Evaluation of the dynamic behavior of controlled systems (step response, time constants, dead times).

• Design and analysis of cascade control systems to improve room temperature control.

• Development and analysis of control and sequencing strategies for heating, cooling, and heat recovery systems.

• Investigation of heat recovery strategies (recuperative and regenerative) during heating and cooling operations.

• Practical training in the programming, commissioning, and operation of building automation systems.

• Integration of control engineering, energy efficiency, and building operations using real system components.

Our battery lab is equipped with comprehensive in-operando and post-mortem diagnostics for decentralized energy storage systems and generators, with a particular focus on lithium-ion battery cells and battery modules. Performance, cycling and aging tests under defined thermal parameters can be performed in the battery lab, as well as characterizations of cell capacity, internal resistance and impedance, opening of lithium-ion cells and post-mortem diagnostics of electrodes and other cell components. The lab equipment includes:

• Battery cyclers for various cell types for maximum currents up to 800 A and voltages up to 80 V (a total of around 25 channels of the Biologic, BaSyTec systems and EA Elektro-Automatik)

• Electrochemical impedance spectrometers (EIS)

• Five temperature test chambers of various sizes with safety equipment for lithium-ion batteries and lead-acid batteries (-40°C to +180°C)

• Glovebox for working under inert gas atmosphere

• Equipment for opening commercial lithium-ion cells and harvesting cell components

• Sample preparation including grinding and polishing machine for scanning electron microscopy, light microscopy and chemical analysis

The equipment was largely financed through funds from the Federal Ministry of Education and Research (BMBF) within the "Enerlab 4.0" project (2018-2020) and has since been gradually expanded. The infrastructure was installed as part of the new construction of the Research and Innovation Center of Energy Technology (RIZ Energie).

A climate chamber simulates the environmental climate. The combination of two adjacent indoor climate chambers provides a so-called double climate chamber. In the two identical test chambers (adiabatic, with high thermal inertia), technical building systems can be evaluated under real-life conditions. Extensive measurement technology, measurement data acquisition and process automation are available for this purpose. Typical areas of application are:

• Performance measurements of facade-integrated building services, especially ventilation

• Evaluation of the dynamic behavior of heating/cooling and ventilation

• Performance measurements on surface temperature control systems ( including building component activation), especially under transient operating conditions for controller development

• Room air flow for different ventilation systems under variable operating conditions

•  Steady-state and dynamic special measurements for heating/cooling and ventilation for determining performance curves and time constants

• Management strategies for inert and agile indoor heat/cool transfer systems

• Assessment of Thermal Comfort (PMV/PPD and Local Comfort Parameters) in Living and Work Spaces

To fully test the operating ranges of the drive components (battery, DC/AC converter, electric motor), test benches such as the one shown in Figure 1 are commonly used. The components highlighted in blue are the DC/AC converter (frequency converter) or the electric motor under test. The components highlighted in green form the braking unit (electrical load machine), which is used to maintain the test machine at a specific speed. Highlighted in yellow is the power supply, which is connected to the electrical grid. For cost and safety reasons, projects often forego the use of a real drive battery and instead rely on battery emulation using a controllable battery emulator (red).

To cover the full range of electric mobility drive components in terms of variety and power class—from e-scooters to hybrid and electric vehicles to trams—two test benches are currently under construction or in the procurement phase. The medium-power test bench is expected to be completed shortly. The test bench is shown in Figure 2. The test bench for the highest drive power is expected to be commissioned by the end of 2021.

In addition to the test benches described for operating real electric machines, a so-called electric machine emulator is in use. An electric machine emulator is capable of simulating electric machines with (within certain limits) arbitrary parameters. It thus replaces the test specimen in Figure 1 with a power electronic component that behaves like the real electric machine at the terminals. This allows, for example, the functionality of the developed control and regulation algorithms to be validated in terms of their universality without the need for additional real machines. With minimal effort, fault conditions in electric machines can be simulated, and the response of the control and regulation algorithms can then be evaluated.

This lab for small-scale combined heat, power and cooling (mCHP) is used to simulate complex energy supply systems for electricity, heating and cooling in the grid network, taking into account the load situation at the consumer. The current network load is provided by an external signal. The actual load situation is mapped in the Air Conditioning/Ventilation Lab (with climate chamber). Based on these parameters, corresponding operation management algorithms optimize the micro-CHP system with power input or output, heat or cold production and thermal storage use. The following components are available:

• Cogeneration plant: 5 kW / 10 kW

• Hot-water stratified storage: 1.500 l with 6 kW heater

• Adsorption chiller: 12 kW

• Reversible heat pump: 12 kW, cooling, and 16 kW, heating

• Cold-water stratified storage: 1,450 l

• Cooling tower / outdoor unit: 29 kW, waste heat, also heat source

These components are connected in such a way as to allow very flexible thermo-hydraulic coupling. Extensive process automation in combination with market-standard field systems serves as a test platform for optimized control algorithms.

Small and medium-sized enterprises are increasingly focusing on their own energy supply, installing their own PV systems, charging stations and storage units. Up to now, energy management has primarily used the flexibility in the classic energy system components. In the course of ‘Industry 4.0,’ however, automation and digitalization are also making the production processes themselves more flexible.

To show how this flexibility in industrial processes can also be harnessed for energy management, a demonstrator for industrial energy management is under development at RIZ Energie. It will be equipped with central components of industrial processes, such as various engine types with frequency converters, compressors, heating and cooling elements, or lighting units. The components are supplemented by an extensive monitoring and automation system as well as a control system. Simultaneously, a so-called digital twin, i. e. a computer simulation of the real system, runs on the control system. This provides the basis for optimized control of the demonstrator through predictive optimization-based control approaches. New methods of industrial energy management can thus be tested and further developed on the demonstrator.

With the establishment of the first junior professorship in refrigeration and heat pump technology at a German university, Hochschule Offenburg has the opportunity to become one of the pioneers in this field in Germany.

In the Refrigeration and Heat Pump Technology Lab, research is conducted both on the systemic integration of smart grids and at the component level.

• How can the thermal integration of heat pumps be improved?

• How can the efficiency of these systems be further increased?

• How can their service life be extended at the same time?

Climate simulations (without solar simulator) in a walk-in climate chamber (CTS GmbH, Hechingen; construction year 2013), with a usable interior space of 40 m³ (5,50m (l) x 2,45 (w) x 2,90 m (h)) between -55 °C and +85 °C, high humidity variability (10% to 98% relative humidity; +5°C to +82°C in dew point range) and fast response time. Typical applications are:

•     Performance and fatigue tests on components exposed to weather conditions

•     Performance tests on vehicles with high-efficiency drives under winter and summer conditions

•     Performance tests on building services systems, especially electric and thermally driven heat pumps/cooling units

•     Building-physics product characterization of components and systems

Combining two adjacent indoor climate cells, a so-called double climate chamber is available for, e.g., evaluating facade-integrated building technology or the dynamic behavior of indoor heating/cooling and ventilation.

Together with wind energy, photovoltaics or PV is the mainstay of a future global energy supply that is based 100% on renewable sources. We conduct research and development to make PV even more environmentally sustainable – for example, by economizing on consumables to achieve even more solar power per square meter of surface area (or per gram of silicon, glass, etc.).

We are focusing on the following areas in particular:

• Solar modules without plastic encapsulation (N.I.C.E.TM technology - production and integration)

• Caracterization of solar cells and modules

We have laboratory equipment for this purpose to optimize production processes:

• Class A+AA+ LED flasher up to 1.0 x 2.0 m2 module size (Wavelabs)

• Laminator for glass-foil and glass-glass modules up to 640 x 480 mm2 (E.E.T.S.)

• Outdoor test bench with monitoring for mono- and bifacial modules (self-made)

• Dispenser up to 525 x 525 mm2 (NordsonAsymtek)

• Climatic test chamber

• Hand tool for plasma cleaning of surfaces (Relyon)

• Multi-tool for, e.g., PL/EL/Grid Resistance (self-made)

• QSSPC and SunsVoc (Sinton Instruments)

• LEXT laser scanning microscope (Olympus)

• IonSlicer for double-sided Ar-ion polishing of STEM samples (JEOL)

• SEM with STEM and EDX functions (JEOL)

Biochar is the solid residue from the pyrolysis of biomass. The corresponding process—PyCCS (pyrogenic carbon capture and storage) or BCR (biochar carbon removal)—accounts for over 80% of the carbon sinks produced worldwide. This makes it the most advanced negative emissions technology (NET) for active CO2 removal. Both biochar and the resulting pyrolysis oils and gases can help, both now and in the future, to decarbonize the economy and actively cool the climate.

Our focus is particularly on the following areas:

• Biochar from biomass for use in agriculture and materials

• Characterization of pyrolysis processes and biochar

To this end, we have laboratory equipment to optimize the production and application of biochar and pyrolysis products:

• Mills for comminution (cutting mills, hammer mills, ball mills, shredders)

• Pelletizing system

• Drying cabinets

• Muffle furnace

• Chemical analysis in the chemistry lab (including TOC, TN, GC, ICP-OES)

• Water-holding capacity

• Lab for circular chromatography

• Turf sanding machine for applying biochar

• Access to a greenhouse for plant experiments

• Kon-Tiki manual pyrolysis reactor with exhaust gas analysis

• Fully automated pyrolysis plant with a biomass throughput of 10 kg/h (Regenis MAX)

Our biochar projects are conducted as part of the FYI:Agriculture 5.0 think tank (fyi-landwirtschaft5.org).

The Air Conditioning and Ventilation Lab primarily explores innovative air conditioning systems and new components such as air diffusers, chilled ceilings, heat recovery systems, air/water heat exchangers, etc. in terms of their energy efficiency and thermal comfort. It includes a lab room and an air conditioning unit. In the lab room (variable size, up to 7.20 m x 7.20 m x 5.50 m, temperature-controllable side walls), extensive measurement equipment is available for the investigation of indoor air flow and thermal comfort, in particular for the measurement of indoor air velocity and degree of turbulence, sound, air temperature, humidity and differential pressure. Flow visualization can be provided as well. The air conditioning system includes all components for thermodynamic air treatment and can be used both for studying optimized operation management strategies and for air preconditioning (experimental analysis of air conditioning systems).