Hardware in the loop evaluation of a hybrid heating system for increased energy efficiency and management

This study presents the tests of a hybrid heating prototype, designed for retrofitting thermal treatment plants like pasteurization, to use hot water and steam in controlled ratios. In the food industry, steam with a temperature above 140°C usually supplies the thermal production processes. The majority of processes require temperatures below 100°C and could be supplied more eficiently by cogeneration, heat recovery or heat pumps. These low temperature heat sources can only be combined with the rigid steam system if the demand structure is changed to a hybrid use of hot water below 100°C and steam. The hybrid heating system (H2S) increases the energy efficiency by integrating the highest possible amount of low temperature heat and responds to sudden changes in the supply structure, like demand response strategies on intermittent renewable energies and the changing availability of hot water and steam. The technical implementation is realised by a hydraulic interconnection of heat exchangers and valves. A smart algorithm controls the integration of hot water and steam into the thermal process. For reasons of food safety and product quality defined process temperatures have to be met. Prerequisite for functional verification on a laboratory scale is a simulation of the process heat demand and potential of hot water during the entire production cycle. The load profiles and relevant process parameters are passed in real time to a hardware-in-the loop (HIL) test-bed and returned to the simulation respectively. Two scenarios, hot water integration from heat pump and demand response management with a gas engine CHP and an electrical steam generator, were evaluated and the functionality of the H2S was proved. Up to 78 % of the final energy demand can be reduced by the H2S based implementation of a heat pump. The control response of the system, even with fluctuating hot water potential and temperature, met the requirements of the dairy industry

Simulation of the space debris environment in LEO using an analytical approach

Several numerical approaches exist to simulate the evolution of the space debris environment. These simulations usually rely on the propagation of a complete population of objects in order to determine the collision probability for each object. Using a Monte Carlo (MC) approach the chances for events, such as explosions and collisions, are triggered based on an assumed probability distribution. So in many different scenarios different objects are fragmented and contribute to a different version of the space debris environment. Finally, the results of the different scenarios are averaged to get a statistically significant estimation. This method is computationaly very expensive due to the propagation of the objects and the application of the MC method. At the Institute of Aerospace Systems (ILR) an analytical model capable of describing the evolution of the space debris environment has been developed and implemented. The model is based on source and sink mechanisms, where yearly launches as well as collisions and explosions are considered as sources. The natural decay and post mission disposal measures are the only sink mechanisms. This method reduces the computational costs tremendously. In order to achieve this benefit a few simplifications have been applied. The approach of the model partitions the LEO into altitude shells. Only two kinds of objects are considered, intact bodies and fragments, which are also divided into diameter bins. As an extension to the previously presented model the eccentricity has additionally been taken into account with 67 eccentricity bins. While a set of differential equations has been implemented in a generic manner, the Euler method has been chosen to integrate the equations for a given time span. For this paper parameters have been chosen so that the model is able to reflect the results of the numerical MC-based simulation LUCA, which is also being developed at the ILR. The evolution of the population in LEO for a 200 years time span is shown and compared for both approaches using step sizes of 1 year. For selected objects in LEO the flux and environmental criticality values are shown. In conclusion the field of application for such a fast analytical model is shown

Energy Efficiency Measures for Batch Retort Sterilization in the Food Processing Industry

The purpose of this study is to highlight the energy saving potentials of a batch retort sterilization process operated by steam and to develop concepts for improving its energy efficiency. By using the methodical approach of the Onion Diagram and the recovery of low grade heat sources, four comprehensive improved energy efficiency concepts have been developed. Two concepts increase the initial product temperature resulting in lower transient steam consumption rates and a decreased energy demand. The other two options transform the waste heat and the energy for product cooling into heat streams for supplying nearby heat sinks or other processes in the plant. Results show that the total energy demand can be reduced by more than 23 % and 42 % of the energy injected into the system can be recovered. The scope of the study focused on a single, independent retort to ensure the transferability of the concepts. This study also shows, using a practical example, the importance of a comprehensive process understanding and analysis prior to application of Pinch Analysis, which is needed to ensure that the correct waste heat stream temperatures are defined, necessary processing constraints are appreciated, and all possible heat sinks in the process are considered

Optimal Energy Supply Structures for Industrial Sites in Different Countries Considering Energy Transitions: A Cheese Factory Case Study

This present study focuses on analysing the most efficient utility energy supply structure in terms of primary energy efficiency, carbon emissions and energy costs. In the German dairy industry, separate conversion with gas fired steam boiler, and cooling with ammonia chillers are the-state-of-the-art technologies. It is attractive due to its robustness and low investment costs. But given the ongoing energy transition to renewable energy, opportunities to reduce emissions will become increasingly important. There are other energy supply options, such as Combined Heat and Power (CHP) and Heat Pumps (HP), that if implemented need to compete against the conventional energy supply systems. One option is CHP to provide cogenerated electricity and heat while cooling remains supplied by ammonia chillers. In countries with high electricity Grid Emissions Factors (GEF) such as Germany and the USA, the use of decentralised CHP results in savings of primary energy and emissions. However, this option is less attractive for countries with low GEF such as France and Norway, and for places like Germany where the energy transition lowering its GEF by 50 % in 2030. In these cases, HP solutions provide the lowest emissions and highest primary energy efficiency

Optimal energy supply structures for industrial food processing sites in different countries considering energy transitions

This is a post-peer-review version of the article "Optimal energy supply structures for industrial food processing sites in different countries considering energy transitions". The final authenticated version is available online at: https://doi.org/10.1016/j.energy.2017.05.06