Selection of public funded Projects of the
Research Group Energy Storage

Storage of electrical surplus energy by the use of heat pumps in combination with sensible and latent thermal storage

Duration:
07/2015 - 06/2018
Funding:

Graduate college Energy self-sufficient buildings, TAO

Contact Person:

Objectives / Short Description:

Within the framework of TechnologieAllianzOberfranken (Technology Alliance Upper Franconia), the graduate school „Energy self-sufficient buildings“ was founded in 2015 where a total of 13 scientists study on future energy systems for buildings.
At the Department of Engineering Thermodynamics and Transport Processes (LTTT) of the University of Bayreuth air/water heat pumps in combination with thermal storage systems are investigated to increase the energy self-sufficiency of buildings. The efficiency increase of air/water heat pumps and the Demand Side Management – to compensate electricity generation peaks caused by photovoltaic and wind power – using the coupling of air/water heat pumps and thermal storage, are research areas of the PhD project. The investigations are carried out computationally as well as experimentally with two identical state of the art air/water heat pumps.


Support Tool for Energy Efficiency pRogrammes in medical centres (STEER)

Duration:
12/2014 - 11/2018
Funding:

European Commission – Competitiveness and Innovation Framework Programme (CIP) – Intelligent Energy Europe programme

Contact Person:

Objectives / Short Description:

The aim of this project is to create a tool that provides the management of medical centers with information on the medical center’s ideal energy consumption in given situations and on the most appropriate energy reduction plan for the medium-long term. The project’s primary proposal is to identify the main variables that are responsible for the energy consumption in medical centers and give to each of them a weight. A sophisticated mathematical model will be developed to reproduce, analyze and optimize the energy consumption in a given scenario.


Additional information: http://cordis.europa.eu/project/rcn/194363_en.htmland http://steer.ctadventure.com/


Mobile latent heat storage with modular heat exchanger

Duration:
10/2012 - 06/2017
Funding:

Fraunhofer Institute for Environmental, Safety, and Energy Technology in the framework of the Fraunhofer Center for Energy Storage

Project Partners:

Fraunhofer UMSICHT, Sulzbach-Rosenberg; REHAU AG + Co, Rehau; FSAVE Solartechnik GmbH, Kassel; Kraft GmbH & Co. KG, Korbach; Ingenieurbüro Budach, Kaarst; LOGEX SYSTEM GmbH & Co. KG, Ingolstadt

Contact Person:

Objectives / Short Description:

The aim of this joint project is to develop novel concepts for mobile latent thermal storage. In addition to lowering the investment costs of such storage systems, especially the reduction of loading and discharging time is aspired in order to increase the achievable annual number of cycles and thus the efficiency of this type of heat transport.

Existing CFD simulation models are developed purposefully, validated by experimental studies and applied for large-scale systematic parameter variations to clarify detailed project-specific questions. The operational behavior of the entire storage will also be investigated with the aid of simplified models.


Development of macro-encapsulated latent heat storage for the transport of heat

Duration:
07/2013 - 06/2016
Funding:

Federal Minsitry for Economic Affairs and Energy

Project Partners:

Lehrstuhl Metallische Werkstoffe, Universität Bayreuth

Contact Person:

Objectives / Short Description:

The application of highly efficient mobile thermal storage systems is an essential approach to extend the use of waste heat. The goal of this project is to develop a next generation of mobile latent heat storage system. Compared to available storages it will be characterized by lower production costs and significantly enhanced application potentials.

The improvements are achieved due to the transition from tank storages with heat exchanger units to macro-encapsulated phase change materials (PCM). Suitable PCMs are to be identified and assessed, and numerous parameters of the capsules have to be examined and optimized, such as geometry, size, metallic materials and wall thickness. Promising concepts are practically tested in a laboratory storage. The range of applications of mobile latent heat storage is significantly extended by the use of PCM with melting temperatures between 70 °C and 150 °C. Various thermodynamic data as well as chemical and physical properties must be determined by measurements. Furthermore, the compatibility of PCM and capsule materials has to be carefully assessed.


Computer based optimization of the thermal mass of monolithic brick walls for the enhancement of energy efficiency and comfort of buildings

Duration:
03/2013 - 02/2015
Funding:

Central Innovation Program, Federal Minsitry for Economic Affairs and Energy

Project Partners:

Ziegelwerk Freital EDER GmbH, Freital; Ziegelwerke Leipfinger-Bader KG, Vatersdorf; Franken Maxit GmbH & Co., Kasendorf; rent a scientist GmbH, Regensburg

Contact Person:

Objectives / Short Description:

One of the most important criteria for the evaluation of the energy efficiency of buildings is the so-called “U” value, which is based on thermal conductivity according to energy saving regulations. Currently used building techniques and modernization measures cope with the regulations. However, practical experience shows that expectations concerning thermal protection are not met completely in many cases. Especially in the case of brick masonry heavy monolithic construction with a high storage capacity gives way to light brick masonry, often combined with thermal insulation composite systems with low thermal conductivity.

It is therefore necessary to consider the heat transfer and energy storage in detail, in order to achieve an energetically advantageous behavior of buildings under real transient conditions. Due to an innovative functionalization by means of phase change materials (PCM) and based on an investigation of the intrinsic properties of the brick and plaster, an increase of energy efficiency and comfort of buildings is to be achieved in this project. By means of modeling and computer-aided simulation, potential improvements are identified and quantified. These approaches are then investigated on a laboratory scale, converted into small demonstration objects and tested under real field conditions.


Enhancement of the efficiency of air/water heat pumps by the integration of latent heat storage systems

Duration:
09/2009 - 09/2012
Funding:

Bavarian Ministry for Science, Research and Arts in the framework of the Bavarian Research Association for Energy-Efficient Technologies and Applications

Project Partners:

GlenDimplex GmbH, Kulmbach

Contact Person:

Results / Short Description:

This subproject of the research network FORETA had the main objective to increase the efficiency of air/water heat pumps by integrating latent thermal storages into the heating and cooling circuit. The disadvantages of air/water heat pumps which can be seen in the need to defrost the evaporator and the temperature variation of the heat source “outside air”, should be compensated as much as possible. Furthermore, it was examined whether the use of latent thermal storage allows a size reduction of heat pump components.

A test bench with two identical heating systems has been planned, constructed and operated (Figure 1). Both heating systems allow for the integration of different latent resp. sensitive buffers in series or parallel circuits. One of the plants has always been operated as a reference in order to be able to quantify efficiency gains over the conventional heating system with a sensitive line buffer storage. With parameter variations realizable at the test bench being limited, the heating systems have also been mapped in numerical models.

 

Measurement data obtained at the test bench were used to validate the model (Figure 2). Then, extensive parameter variations were then performed with this model. These variations included the heating curve end temperature, various phase change materials with different melting temperatures, serial and parallel connection of the buffer storage, storage capacity and the size of the heat exchanger surfaces in the storage. In addition, the control strategy of the heat pump system was varied.

The studies show that a purely demand-driven heat pump operation is inefficient. With the use of latent thermal buffer storage of small capacity and an operation mode focusing on heat demand, only minor efficiency gains are realizable. In contrast, COP can be increased by around 25 % with a transition to external temperature control and the use of a latent thermal storage with about ten times the capacity compared to the reference system. Furthermore, an undesired operation of the electric heating element can thus be avoided almost completely. However, also a more powerful heat pump is necessary in this case. It should be able to provide daily required heating energy during the hours of higher ambient air temperatures.


Modeling and simulation of the temperature profile of facades containing glass materials

Duration:
12/2009 - 11/2011
Funding:

Bavarian Research Foundation in the framework of the Bavarian Association Glass for Energy-Efficient Building Services  Engineering; subproject  III.2

Project Partners:

F. X. Nachtmann Bleikristallwerke GmbH, Neustadt a. d. Waldnaab

Contact Person:

Results / Short Description:

Nowadays not only an efficiency improvement of energy conversion processes is aspired, but also a reduction of net energy demand, especially for space heating. In the future, increasingly stringent legal regulations will be met no longer by conventional measures such as thermal insulation of facades.
Glass-based materials and semi-finished products developed in the framework of the joint-project FORGLAS provide an innovative approach to meet such challenges; they also provide a new business segment for glass industry. In this subproject of FORGLAS, simulation models for thermodynamic description of glass-based materials have been developed and integrated into hygrothermal simulation tools. Based on such modelling, glass-based products developed in other FORGLAS subprojects have been evaluated and optimized. In addition to a direct cooperation with an industrial company there we also collaborations with participating research institutes and other facilities.

 

In cooperation with the industrial partner Nachtmann a glass tile functionalized by coatings has been developed. Simulations and iterative optimisation indicate that both a thermal insulation during summer and a reduction of heating demand during winter can be achieved. In cooperation with another FORGLAS subproject additives for facade coatings have been examined. Simulations show that these additives can increase reflection of solar radiation. This effect is useful especially for heat protection in warm climates during summer, as significant savings in the demand for air conditioning can be achieved. As a further contribution to this subproject flakes have been studied which reflect radiation in the IR spectrum. These flakes are mixed to interior paints and increase indoor “comfortableness”. Based on comfort models and their adaptation, this subproject on hygrothermal simulation achieved remarkable results. The positive influence of reflected infrared radiation on humans allows for a reduction of the room temperature without compromising comfort. This results in a reduced space heating demand.
Again in cooperation with another subproject, the influence of porous glass flakes on moisture balance in highly insulated buildings has been examined. These flakes increase comfort and reduce risks of mold formation.


Extended application of industrial waste heat in Upper Franconia by the application of mobile thermal storage systems

Duration:
07/2009 - 12/2010
Funding:

European Regional Development Fund

Contact Person:

Results / Short Description:

The recycling of idle waste heat from various processes in industry and commerce is an essential issue to further improve energy efficiency and to reduce emissions of greenhouse gases, to reduce production costs and to increase competitiveness. However, a direct company-internal consumption of waste heat as well as heat supply for external consumers is often not feasible.

The main objective of this pilot project was to develop concepts for a more intensive use of waste heat and to examine the feasibility of such concepts in the region of Upper Franconia. The focus was on mobile thermal storage systems for the transport of thermal energy and efficient technologies to generate electricity from waste heat.

First, various types of storage systems have been analyzed and evaluated as to their suitability for mobile applications. Latent thermal storage proved to be very promising. Sodium acetate trihydrate already available with mobile storages may deliver thermal energy only at low temperatures and so the number of potential heat consumers is low. Thus additional storage materials with higher melting temperature are urgently needed and a first screening has been performed.

For usual storage with recuperative heat transfer, curves of loading and unloading performance have been evaluated and heat loss estimated. For macro-encapsulated storage materials and direct contact storage (see Figures 1 and 2) test benches in laboratory scale have been constructed and tested. Macro-encapsulated phase change materials proved to be most promising.

 

With regard to storage transport, economic and legal aspects have been considered as well as technical, logistical and safety issues. Results revealed the significant influence of storage capacity on economy. In this context a complete discharge of a mobile storage at the location of the recipient possibly should not be aspired in order to operate the storage most cost-effective.

Concerning the recovery of unused heat from CHP, possibilities of the generation of addi-tional electricity have been examined. Technical concepts for the integration of ORC technology at different temperature levels have been developed and their economic advantages and disadvantages have been worked out. In addition, options associated with the use of binary working fluid mixtures have been investigated, in order to increase ORC efficiency in electricity generation from low temperature heat.

Furthermore, own surveys and evaluations of data reported in the Energy Atlas have been performed, in order to identify suitable waste heat suppliers and consumers in the area of Upper Franconia. Although a number of companies might act as waste heat supplier, but there are hardly any suitable consumers of low temperature heat provided by sodium acetate trihydrate storages. For two case studies detailed waste heat recovery options have been elaborated. In both cases, however, no direct project for the use of such mobile storage systems could be initiated.

This ultimately underscores the need to develop thermal storage systems with higher melting temperatures of the PCM and energy- and cost-efficient ORC processes for electricity generation from waste heat. Based on the work carried out and the information thus obtained, new projects on these issues have been acquired successfully in the meantime.