Rita Streblow

New energy concepts and related information technologies: Dual Demand Side Management

This paper presents the concept of Dual Demand Side Management (2DSM) as an evolution of the conventional Demand Side Management concept. 2DSM accounts at the same time on one hand for the local needs, i.e. energy efficiency of the building stock as well as optimization of the local distribution grid and on the other hand for the challenges of the higher level electrical grid arising from the integration of renewable and alternative energy sources. The proposed concept shows the possibilities originating from the interaction of local district heating, heat storage and micro grid technology. Finally the paper shows the development and testing processes required for designing complex multi-domain systems.

MIP approach for designing heating systems in residential buildings and neighbourhoods

In this work, a mixed integer linear programming (MIP) approach for the optimal design of energy systems in residential buildings is presented. The optimization model considers the economic criteria of the guideline VDI 2067. The objective of the MIP is to minimize the annual costs which comprise the investment as well as demand- and operation-related costs. Conventional boilers, electrical heaters, combined heat and power (CHP) units, heat pumps (HPs), photovoltaic (PV) systems and thermal storages as well as local heating networks (HNs) are defined as options. The investigation on a building level shows that a boiler is the economically optimal solution for small buildings, followed by a HP unit. In multi-family buildings, both boilers and CHP units hold an economical advantage over HPs. For apartment buildings, CHP is identified as the economically optimal system. In the neighbourhood analysis of six buildings, the solver establishes a local HN which allows for both economical and CO2-emission reductions.

Dynamic Modeling, Simulation and Exergy Analysis of an Innovative Hydronic Heating System

In this study, dynamic modeling and simulation of a decentralized hydronic heating system has been performed. The simulated space heating system is a model of an innovative heating system of an apartment with a boiler that supplies heat for eight radiators which are served by distribution pipes. Eight small pumps, located at the outlet of the radiators instead of a central circulation pump, work according to demand, and supply each radiator with hot water only when required. A PID controller regulates the rotational speed of the pumps and consequently the power of the radiators to maintain the room temperature at the set point.To evaluate the performance of such a heating system, a model of the entire energy chain from generation to distribution is needed. Therefore, in this work, detailed sub-models for the hydraulic system have been developed and coupled with the model of a building to make a general model for simulating the performance of the whole system. The analysis has been carried out by simulation of the system using the object-oriented programing language Modelica. Dymola, which is a multi-domain modeling and simulation tool, has been used as simulation environment. The Modelica Standard Library 3.2 and the Modelica libraries for building simulation such as BaseLib, Database, Building and HVAC components libraries have been applied to simulate the hydraulic and thermal behavior of the system. In the next step, the system has been analyzed form exergy point of view and the simulation results from the dynamic model have been presented in an exergetic framework.Copyright

Design of an Optimization Algorithm for the Distribution of Thermal Energy Systems and Local Heating Networks within a City District

The linkage of combined heating and power (CHP) systems with local heating networks has the potential to increase energy efficiency on city district scale. First, CHP systems have a high overall efficiency. Second, the usage of CHP systems as heat sources for local heating networks can lead to advantageous economics of scale effects. With an increasing number of buildings the number of possible energy system combinations enlarges tremendously. A manual design approach might lead to a suboptimal solution. This paper describes an approach for the optimized placement of CHP systems, boilers, thermal storages and local heating networks on city district level. A mixed integer linear programming (MILP) problem has been formulated within the General Algebraic Modeling System (GAMS). The objective function is the cost minimization of the overall system under ecological and technical constraints. To reduce the optimization runtime, a k-Medoids demand day clustering and a minimum spanning tree strategy have been implemented. A small city district has been designed as test case. On one hand the algorithm leads to planning solutions with reduced overall costs as well as decreased greenhouse gas emissions. On the other hand a number of 9 buildings leads to 2.5 hours runtime. Therefore, further work on strategies for run time reduction is required.

Simulation-based implementation and evaluation of a system of systems optimization algorithm in a building control system

The objective of this research is to evaluate the performance of a system of systems optimization algorithm, namely, L4G-PCAO, in building energy systems. Since the test bed of this research is an office building with more than two hundred occupiers, the heating and cooling demands of the building must always be fully satisfied. Consequently, changes in the currently-installed control system cannot be made forthrightly. Therefore, fresh ideas like implementation of new control strategies or optimization algorithms should be firstly put to the test via dynamic simulation, which makes engineers capable of examining new control and optimization strategies. The performance should then be analyzed and evaluated before implementing in the use case. This paper presents a strategy for simulation-based implementation of L4G-PCAO in a building energy system and also evaluates its performance. The results show that it is not only possible to conserve energy by applying this newly-developed optimization algorithm to existing control systems, but also it can shift the usage of energy sources in a more environment-friendly direction.

System of Systems theory as a new perspective on building control

Energy efficiency of buildings has been identified as a core element in facing the climate change and the scarcity of energy resources. The energy supply system for a building is, especially with view on thermal interrelations, a highly complex and heterogeneous system that emerges jointly with the building construction, the users behavior, the weather conditions and the surrounding energy and price policy to a real system-of-system. The building control system as the “intelligent instance” of the System of Systems (SoS) takes a special role in realizing the potential of the joint operating constituent systems due to the energy efficiency of the building or district. We apply SoS as an innovative engineering approach to a complex energy system.

Laboratory Approaches to Studying Occupants

Laboratories offer the possibility to study occupant behavior in a very detailed manner. A wide range of indoor environmental scenarios can be simulated under precisely controlled conditions, and human subjects can be selected based on pre-defined criteria. The degree of control over experiments is high and a large number of physical, physiological, and psychological quantities can be monitored. This chapter gives an overview of various types of test facilities in the world and their main features in terms of experimental opportunities. It then presents typical technical equipment and sensor technologies used in laboratory environments. Finally, questions on appropriate laboratory design and experimental set-ups are discussed. One conclusion is that, in spite of many advantages, there are limits to investigating occupant behavior in a laboratory’s “artificial” environment, in part due to the fact that subjects always feel observed to some extent. However, valuable results can be achieved if the specific opportunities of laboratories are utilized both by appropriate design and precise experiments during operation.

Test of new control strategies for room temperature control systems fully controllable surroundings for a heating system with radiators

About one third of Germany;s energy demand is used for room heating thus offering a huge potential for energy savings. The development of intelligent home energy systems should optimize the energy consumption of buildings. In Germany the most common way to control the room temperature while heating is to use a thermostatic valve. This temperature-control system is self-sustaining but has no possibility to communicate to the heating system or other devices in the household. For the test and development of new control strategies and the appropriate components a Hardware-in-the-Loop test bench for hydraulic network applications is developed at the E.ON Energy Research Center. This test bench allows the test of a heating system of a flat in a controllable surrounding under dynamic boundary conditions. In this paper the new test bench concept will be described.

Impact of control approaches for building energy systems on distribution grid state

A growing penetration of decentralized power generation (especially photovoltaics) and additional distributed loads is expected in future energy systems in Germany. This paper investigates the impact on the electrical grid of heat-driven as opposed to electrical-driven control of energy systems in buildings. Different penetrations of the building energy systems are additionally analyzed to show their influence on the performance indicators of the electrical grid (voltages, line utilization). Different models for load/generation and the behavior of the building energy systems including the heat storages are coupled with an electrical grid simulation to perform a numerical analysis on a realistic representation of the system. The results show that a coordination of BES operation has to be considered and slight improvements of the electrical quantities can be reached by improved control. CHP plants supplemented by HR are more beneficially for the electrical grid as they can shape both loads and generation.