Façade-integrated Massive Solar-thermal Collectors Combined with Long-term Underground Heat Storage for Space Heating

AbstractThis work shows how façades of industrial buildings can be used as a heat source for a heat pump heating system. Opaque sections of the building skin are formed by façade-integrated massive solar-thermal collectors (FMSC) in order to collect solar radiation and heat from the ambient air. By means of a building-integrated long-term storage (BLTS), the heat collected during the summer period is conserved for utilization during the heating season. Depending on the current ambient conditions and the actual heat demand, different operating modes are to be applied: In part load with favorable external conditions the space heating demand is covered by direct use of the FMSC heat output. With rising heat demand and lower heat gain from ambient, heating is accomplished by a heat pump with FMSC or BLTS as heat source. With regard to architectural restrictions, FMSC surfaces have to be operated at temperatures above the dew point, avoiding formation of condensate or frost at the building surface. The performance of the system is modeled by means of TRNSYS, relying to available model types for the system components. The model of the core component, i.e. the FMSC, has been validated by a laboratory measurement. A design study has been carried out for an industrial building with a foot print of 1,300 m2 and an annual heating demand of 82,000 kWh. Key aspect of the investigation is the identification of the most efficient system composition, characterized by the required size of collector area and heat storage volume

Application of customized absorption heat pumps with heating capacities above 500 kW : Project: Ackermannbogen, Munich

Part of: Thermally driven heat pumps for heating and cooling. – Ed.: Annett Kühn – Berlin: Universitätsverlag der TU Berlin, 2013 ISBN 978-3-7983-2686-6 (print) ISBN 978-3-7983-2596-8 (online) urn:nbn:de:kobv:83-opus4-39458 [http://nbn-resolving.de/urn:nbn:de:kobv:83-opus4-39458]A solar heating system was installed at “Ackermannbogen” in Munich, where a residential area was built in 2007. To achieve a solar fraction larger than 50%, a large seasonal storage was installed to store solar surplus during summer and supply solar thermal heat in winter. To decrease the needed volume of this storage an absorption heat pump was installed into the system. This heat pump utilises heat from the storage and is driven by heat from a district heating grid. The low temperature heat is lifted to temperatures useable within the local heating grid to provide heat and domestic hot water to the residential area. Due to the demand on temperature levels of the system a “twin” absorption heat pump - consisting of two separate absorption heat pumps within a single shell - had to be installed for this application. In order to gain maximum benefit of the stored solar thermal energy the system controls change the mode of operation depending on the temperatures of the storage and the return temperature of the solar thermal collectors. The system was monitored and the collected data (capacities and temperatures of the absorption heat pump) of a representative day is shown in this paper

Application of customized absorption heat pumps with heating capacities above 500 kW: Project: VIVO, Warngau (near Munich)

Part of: Thermally driven heat pumps for heating and cooling. – Ed.: Annett Kühn – Berlin: Universitätsverlag der TU Berlin, 2013 ISBN 978-3-7983-2686-6 (print) ISBN 978-3-7983-2596-8 (online) urn:nbn:de:kobv:83-opus4-39458 [http://nbn-resolving.de/urn:nbn:de:kobv:83-opus4-39458]In 2005 a gas fired single effect absorption heat pump was installed at the area of VIVO GmbH, who runs a local civic waste collection point. Besides other recyclable materials, biodegradable waste is collected here and composted. During the composting process heat is generated due to aerobic biological processes. As the exhaust air from the rotting heaps has to be cooled down due to process reasons, the heat has to be transferred to an auxiliary medium. Until 2005 the heat was set free to the environment by free air cooling. The thermally driven heat pump instead utilises this heat and supplies heat on a useful temperature level to a local district heating grid. The local district heating grid supplies heat to office buildings of VIVO GmbH as well as to a nearby industrial area. Hence, the heat pump has two beneficial effects on this application, it cools down a process were cooling is needed and uses this energy for fuel saving in a heating grid, which runs basically on oil burners instead

3D-CFD Design Study And Optimization Of A Centrifugal Turbo Compressor For The Operation In A Hybrid Sorption/ Compression Heat Pump Cycle

In various applications the use of sorption chillers and heat pumps is limited by the available temperature level of the driving heat source or the heat sink for export of reject heat. These constraints can be overcome by integrating an efficient high-speed transonic turbo-compressor into the internal cycle of a thermally driven water/lithium bromide absorption heat pump. The operation in a hybrid heat pump with the refrigerant water implies specific challenges for the design of the compressor: Saturation pressures in the sub-atmospheric range, low vapor density, high volume flows and a targeted pressure ratio of 3 result in high impeller tip speed up to 660 m/s and transonic flow phenomena in the flow channel of impeller and diffusor. Here the authors present a theoretical design study based on a 3D-simulation of a centrifugal compressor, targeted at the given operating conditions for a hybrid heat pump. Key figures are investigated to figure out the relationship between impeller tip speed, compressor pressure ratio and operating range of the compressor meeting the requirements, wide stable operating range between surge and choke line and appropriate pressure ratio. The optimization of the impeller geometry comprises both fluid dynamic behavior and structural stability

Solar heating and cooling with absorption chiller and latent heat storage

Part of: Thermally driven heat pumps for heating and cooling. – Ed.: Annett Kühn – Berlin: Universitätsverlag der TU Berlin, 2013 ISBN 978-3-7983-2686-6 (print) ISBN 978-3-7983-2596-8 (online) urn:nbn:de:kobv:83-opus4-39458 [http://nbn-resolving.de/urn:nbn:de:kobv:83-opus4-39458]Performance figures and control strategies of an innovative solar heating and cooling system (SHC-System) composed of an aqueous lithium bromide-water single-effect absorption chiller with 10 kW cooling capacity, a dry heat rejection system and a low phase change temperature (28-29°C) latent heat storage based on salt hydrates are given. During cooling season the latent heat storage serves as a secondary heat sink supporting the dry air cooler at high ambient temperatures to ensure 32°C coolant to the absorption chiller at any time. In the heating season the latent heat storage buffers heat surplus of the solar collectors latently by melting the phase change material (PCM) calcium chloride hexahydrate. As a result of the constant temperature during charging, solar thermal collector efficiency is increased and furthermore the overall heat dissipation is reduced. The results on the one hand show a positive effect on the cooling capacity, electrical and thermal Coefficient of Performance (COP) of the absorption chiller, which are significantly increased especially at hot days compared to solely dry air cooled systems. On the other hand a high solar fraction in the heating period, due to constantly low storage temperatures, is achieved

1155 Development of a realistic scenario for the thermal energy demand of residential buildings in Bavaria till 2050

To achieve the climate protection goals, enormous efforts must be undertaken in all sectors: households, industry, commerce, and transport. Following a straightforward approach, the political objectives foresee, that in the building sector a massive reduction of energy use for the heat supply is accomplished. However, previous investigations have shown that this reduction of energy consumption is not feasible. Older buildings exhibit especially high energy demand and emissions. Yet, due to the low refurbishment rate, no substantial change of the heat demand can be expected within the next decades. By fully renovating the entire residential building stock, approximately 70 % of the final energy demand and related CO2 emissions could be saved, still not enough to reach the political goals. Therefore, renovation or renewal of buildings and of the use of renewable energy sources have to be implemented jointly for achieving the desired savings.The methods used to estimate the characteristics of Bavaria’s residential building stock as well as its heating energy demand and related CO2 emissions for the year 2050 are presented. Alternative goals are given which base upon the achievable final energy saving for a realistic renovation scenario accompanied by further reduction of CO2 emissions by using renewable energies

Solar Heating and Cooling System with Absorption Chiller and Latent Heat Storage – A Research Project Summary

AbstractA reliable solar thermal cooling and heating system with high solar fraction and seasonal energy efficiency ratio (SEER) is preferable. By now, bulky sensible buffer tanks are used to improve the solar fraction for heating purposes. During summertime when solar heat is converted into useful cold by means of sorption chillers the waste heat dissipation to the ambient is the critical factor. If a dry cooler is installed the performance of the sorption machine suffers from high cooling water temperatures, especially on hot days. In contrast, a wet cooling tower causes expensive water treatment, formation of fog and the risk of legionella and bacterial growth. To overcome these problems a latent heat storage based on a cheap salt hydrate has been developed to support a dry cooler on hot days, whereby a constant low cooling water temperature for the sorption machine is ensured. Therefore the need of a wet cooling tower is avoided and neither make-up water nor maintenance is needed. The same storage serves as additional low temperature heat storage for heating purposes allowing optimal solar yield due to constant low storage temperatures. Four pilot installations between 7kW and 90kW nominal cooling capacity were equipped with latent heat storages between 80 kWh and 240 kWh energy content. Annual in situ measurement data shows a positive effect on the seasonal energy efficiency ratio (SEER) for cooling up to 11.4. Furthermore simulation results under different climatic conditions indicate raising efficiency up to 64% compared to a system with solely dry re-cooling. Long-term test bench measuring data concerning performance and durability as well as a new approach for a state of charge detection for latent heat storages are presented as well

Development of Reference Buildings to Analyze the Potential for Energy-Efficient Refurbishment of Buildings

The building sector offers the largest potential for a significant reduction of greenhouse gas emissions. Based on own preliminary investigations for the State of Bavaria, a complete renovation of the building envelope of the current residential building stock would result in a reduced demand for final thermal energy for space heating and domestic hot water by about 70 %. The present study analyzes different existing reference buildings and reference methods. Based on a general literature review, specific criteria will be developed for reference models to represent the thermal energy consumption of the residential building stock for the regional domain under investigation. The objective is to represent the building stock with a limited amount of reference buildings. The method for the development of a reference building will be shown exemplarily for one category

Development of Reference Buildings to Analyze the Potential for Energy-Efficient Refurbishment of Buildings

The building sector offers the largest potential for a significant reduction of greenhouse gas emissions. Based on own preliminary investigations for the State of Bavaria, a complete renovation of the building envelope of the current residential building stock would result in a reduced demand for final thermal energy for space heating and domestic hot water by about 70 %. The present study analyzes different existing reference buildings and reference methods. Based on a general literature review, specific criteria will be developed for reference models to represent the thermal energy consumption of the residential building stock for the regional domain under investigation. The objective is to represent the building stock with a limited amount of reference buildings. The method for the development of a reference building will be shown exemplarily for one category