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The present paper introduces an iterative methodology to progressively reduce building simulation model complexity with the aim of identifying potential trade-offs between computational requirements (i.e., model complexity) and energy estimation accuracy. Different levels of model complexity are analysed, from commercial building energy simulation tools to low order calibrated thermal networks models. Experimental data from a residential building in Germany were collected and used to validate two detailed white-box models and a simplified white-box model. The validation process was performed in terms of internal temperature profiles and building thermal energy demand predictions. Synthetic profiles were generated from the validated models and used for calibrating high order models. A reduction (trimming) procedure was applied to reduce the model complexity using an energy performance criterion prior to model trimming. The proposed methodology has the advantage of keeping the physical structure of the original RC model, thus enabling the use of the trimmed lumped parameter building model for other applications. The analysis showed that it is possible to reduce the model complexity by half, while keeping the accuracy above 90% for the targeted building.
Mattia De Rosa; Marcus Brennenstuhl; Carlos Andrade Cabrera; Ursula Eicker; Donal P. Finn. An Iterative Methodology for Model Complexity Reduction in Residential Building Simulation. Energies 2019, 12, 2448 .
AMA StyleMattia De Rosa, Marcus Brennenstuhl, Carlos Andrade Cabrera, Ursula Eicker, Donal P. Finn. An Iterative Methodology for Model Complexity Reduction in Residential Building Simulation. Energies. 2019; 12 (12):2448.
Chicago/Turabian StyleMattia De Rosa; Marcus Brennenstuhl; Carlos Andrade Cabrera; Ursula Eicker; Donal P. Finn. 2019. "An Iterative Methodology for Model Complexity Reduction in Residential Building Simulation." Energies 12, no. 12: 2448.
In the paper, a method was developed to automatically dimensionalize and calculate central energy generation and supply scenarios with a district heating system for cities based on 3D building models in the CityGML format and their simulated heat demand. In addition, the roof geometry of every individual building is used to model photovoltaic energy generation potential. Two types of supply systems, namely a central heat pump (HP) system and a large co-generation (combined heat and power-CHP) system (both with a central storage and district distribution system), are modeled to supply the heat demand of the area under investigation. Both energy generation models are applied to a case study town of 1610 buildings. For the HP scenario, it can be shown that the case study town’s heat demand can be covered by a monovalent, low-temperature system with storage, but that the PV only contributes 15% to the HP electricity requirement. For the CHP scenario, only 61% of the heat demand can be covered by the CHP, as it was designed for a minimum of 4000 operating hours. Both the PV and the CHP excess electricity are fully injected into the grid. As a result, the primary energy comparison of both systems strongly depends on the chosen primary energy factors (PEF): with given German regulations the CHP system performs better than the HP system, as the grid-injected electricity has a PEF of 2.8. In the future, with increasingly lower PEFs for electricity, the situation reverses, and HPs perform better, especially if the CHP continues to use natural gas. Even when renewable gas from a power to gas (P2G) process is used for the CHP, the primary energy balance of the HP system is better, because of high conversion losses in the P2G process.
Verena Weiler; Jonas Stave; Ursula Eicker. Renewable Energy Generation Scenarios Using 3D Urban Modeling Tools—Methodology for Heat Pump and Co-Generation Systems with Case Study Application †. Energies 2019, 12, 403 .
AMA StyleVerena Weiler, Jonas Stave, Ursula Eicker. Renewable Energy Generation Scenarios Using 3D Urban Modeling Tools—Methodology for Heat Pump and Co-Generation Systems with Case Study Application †. Energies. 2019; 12 (3):403.
Chicago/Turabian StyleVerena Weiler; Jonas Stave; Ursula Eicker. 2019. "Renewable Energy Generation Scenarios Using 3D Urban Modeling Tools—Methodology for Heat Pump and Co-Generation Systems with Case Study Application †." Energies 12, no. 3: 403.
High fluctuations of renewable energy sources, such as wind and solar energy, require storage capacity to maintain supply reliability. For long term storage energy carriers to substitute fossil fuels must be found. The reduction of carbon dioxide to liquid substances such as formic acid or formate with electrons from renewable energy sources seem to be a promising approach. This paper tries to find answers for the following question: Under which conditions is it possible to use electrochemical carbon dioxide reduction to formate as urban seasonal energy storage?
Daniel Lust; Paul Rößner; Marcus Brennenstuhl; Elias Klemm; Bernd Plietker; Ursula Eicker. Decentralized city district hydrogen storage system based on the electrochemical reduction of carbon dioxide to formate. Proceedings of the 13th International Renewable Energy Storage Conference 2019 (IRES 2019) 2019, 1 .
AMA StyleDaniel Lust, Paul Rößner, Marcus Brennenstuhl, Elias Klemm, Bernd Plietker, Ursula Eicker. Decentralized city district hydrogen storage system based on the electrochemical reduction of carbon dioxide to formate. Proceedings of the 13th International Renewable Energy Storage Conference 2019 (IRES 2019). 2019; ():1.
Chicago/Turabian StyleDaniel Lust; Paul Rößner; Marcus Brennenstuhl; Elias Klemm; Bernd Plietker; Ursula Eicker. 2019. "Decentralized city district hydrogen storage system based on the electrochemical reduction of carbon dioxide to formate." Proceedings of the 13th International Renewable Energy Storage Conference 2019 (IRES 2019) , no. : 1.
Daylight usage in buildings improves visual comfort and lowers the final energy demand for artificial lighting. The question that always occurs is how much conservation can be achieved? New or rare materials and constructions have a lack of information about their application. Therefore, the current investigation quantifies the daylight and energy performance of a rare multi-layer textile membrane roof. A translucent, thermal insulation with a glass fibre fleece between the two roof membranes combines daylight usage and heating demand reduction. A sports hall built in 2017 is used as a case study building with 2300 m2 membrane roof surface. The optical properties of the roof construction were measured with a total visual light transmittance τv of 0.72% for a clean surface. A climate-based annual daylight modelling delivers daylight indicators for different construction scenarios. The results show that, in comparison to only one glass façade, the additional translucent and thermally insulated membrane roof construction increases the annual daylight autonomy (DA700) from 0% to 1.5% and the continuous DA700 from 15% to 38%. In the roof-covered areas of the sport field, this results in a 30% reduction of the electricity demand for artificial lighting from 19.7 kWhel/m2/a to 13.8 kWhel/m2/a, when a dimming control is used. The study also found that the influence of the soiling of one layer decreases its light transmittance by a factor 0.81. Two soiled layers lower τv by a factor of 0.66 to 0.47%. This increases the electricity demand for lighting by only 12%. The results should be very valuable as a comparison and benchmark for planners and future buildings of a similar type.
Daniel Gürlich; Amando Reber; Andreas Biesinger; Ursula Eicker. Daylight Performance of a Translucent Textile Membrane Roof with Thermal Insulation. Buildings 2018, 8, 118 .
AMA StyleDaniel Gürlich, Amando Reber, Andreas Biesinger, Ursula Eicker. Daylight Performance of a Translucent Textile Membrane Roof with Thermal Insulation. Buildings. 2018; 8 (9):118.
Chicago/Turabian StyleDaniel Gürlich; Amando Reber; Andreas Biesinger; Ursula Eicker. 2018. "Daylight Performance of a Translucent Textile Membrane Roof with Thermal Insulation." Buildings 8, no. 9: 118.
Energy efficient cooling systems are urgently required in order to face the increasing cooling demand of the building and industry sectors and comply with the ambitious EU target of greenhouse gas emission reductions. The present work aims to show that simple heat rejection control strategies can lead to significant energy savings. Different approaches of sequencing the operation of several cooling towers and a method to adapt the cooling water temperature set-point to the actual ambient conditions are proposed. These strategies are first investigated theoretically for an existing chilled-water plant of 13.7 MW installed cooling capacity. Up to 20% energy savings are theoretically possible depending on the used control strategy and the weather conditions. A variable cooling water set-point as a function of the wet bulb temperature allows for the most significant savings. After implementation of this measure in the existing cooling plant, 2 years monitoring results show that the overall system efficiency of the chilled water plant could be increased by 15% compared to the initial status confirming the results of the theoretical study.
Antoine Dalibard; Andreas Biesinger; Mariela Cotrado; Andreas Trinkle; Ute Bartels; Ursula Eicker. Performance improvement of a large chilled-water plant by using simple heat rejection control strategies. International Journal of Refrigeration 2018, 94, 1 -10.
AMA StyleAntoine Dalibard, Andreas Biesinger, Mariela Cotrado, Andreas Trinkle, Ute Bartels, Ursula Eicker. Performance improvement of a large chilled-water plant by using simple heat rejection control strategies. International Journal of Refrigeration. 2018; 94 ():1-10.
Chicago/Turabian StyleAntoine Dalibard; Andreas Biesinger; Mariela Cotrado; Andreas Trinkle; Ute Bartels; Ursula Eicker. 2018. "Performance improvement of a large chilled-water plant by using simple heat rejection control strategies." International Journal of Refrigeration 94, no. : 1-10.
Daylight usage in buildings improves visual comfort and lowers the final energy demand for artificial lighting. The question always occurs: how much conservation can you achieve? New upcoming or rare materials and constructions have a lack of information about their application. Therefore, the current work investigates the daylight performance of a multi-layer textile membrane roof with 2 300 m² on top of a sports hall. A translucent, thermal insulation with a glass fibre fleece between the roof membranes combines daylight usage and heating demand reduction. A sports hall with built year 2017 is selected as the case study building. The optical properties of the roof construction are measured. The (visual) light transmittance amounts to 0.72 % with a clean surface. An accordingly parametrized climate-based annual daylight modeling delivers daylight indicators for different construction scenarios. The results show that in comparison to only one glass facade, the additional translucent and thermally insulated membrane construction increases the annual daylight autonomy700/ continuous DA700 from 0/ 15 % to 1.5/ 38 %. In the roof covered areas of the sport field, this results in a reduction from 19.7 to 13.8 kWhel/m²/a electricity for the artificial lighting with dim control (30 % savings). Also, the influence of soiling on the light transmittance was determined with a relevant reduction of one layer about a factor 0.81. The novel results are of great value as a comparison and benchmark for planners and future buildings of similar type.
Daniel Gürlich; Amando Reber; Andreas Biesinger; Ursula Eicker. Daylight Performance of a Translucent Textile Membrane Roof with Thermal Insulation. 2018, 1 .
AMA StyleDaniel Gürlich, Amando Reber, Andreas Biesinger, Ursula Eicker. Daylight Performance of a Translucent Textile Membrane Roof with Thermal Insulation. . 2018; ():1.
Chicago/Turabian StyleDaniel Gürlich; Amando Reber; Andreas Biesinger; Ursula Eicker. 2018. "Daylight Performance of a Translucent Textile Membrane Roof with Thermal Insulation." , no. : 1.
Many installed solar thermally driven cooling systems suffer from high auxiliary electric energy consumption which makes them not more efficient than conventional compression cooling systems. A main reason for this is the use of non-efficient controls with constant set points that do not allow a chiller power modulation at partial-load and therefore lead to unnecessary high power consumption of the parasitics. The aims of this paper are to present a method to control efficiently solar thermally driven chillers, to demonstrate experimentally its applicability and to quantify the benefits. It has been shown that the cooling capacity of a diffusion absorption chiller can be modulated very effectively by adjusting both the temperature and the flow rate of the cooling water. With the developed approach and the use of optimization algorithms, both the temperature and the flow rate can be controlled simultaneously in a way that the cooling load is matched and the electricity consumption is minimized. Depending on the weather and operating conditions, electricity savings between 20% and 60% can be achieved compared to other tested control approaches. The highest savings are obtained when the chiller is operated at partial load. The presented method is not restricted to solar cooling systems and can also be applied to other conventional heating ventilation and air conditioning (HVAC) systems.
Antoine Dalibard; Daniel Gürlich; Dietrich Schneider; Ursula Eicker. Control Optimization of Solar Thermally Driven Chillers. Energies 2016, 9, 864 .
AMA StyleAntoine Dalibard, Daniel Gürlich, Dietrich Schneider, Ursula Eicker. Control Optimization of Solar Thermally Driven Chillers. Energies. 2016; 9 (11):864.
Chicago/Turabian StyleAntoine Dalibard; Daniel Gürlich; Dietrich Schneider; Ursula Eicker. 2016. "Control Optimization of Solar Thermally Driven Chillers." Energies 9, no. 11: 864.
The results in this work show the influence of long-term operation on the decomposition of working fluids in eight different organic rankine cycle (ORC) power plants (both heat-led and electricity-led) in a range of 900 kWel to 2 MWel. All case study plants are using octamethyltrisiloxane (MDM) as a working fluid; the facilities are between six to 12 years old. Detailed analyses, including the fluid distribution throughout the cycle, are conducted on one system. All presented fluid samples are analyzed via head space gas chromatography mass spectrometry (HS-GC-MS). Besides the siloxane composition, the influence of contaminants, such as mineral oil-based lubricants (and their components), is examined. In most cases, the original working fluid degrades to fractions of siloxanes with a lower boiling point (low boilers) and fractions with a higher boiling point (high boilers). As a consequence of the analyses, a new fluid recycling and management system was designed and tested in one case study plant (Case Study #8). Pre-post comparisons of fluid samples prove the effectiveness of the applied methods. The results show that the recovery of used working fluid offers an alternative to the purchase of fresh fluid, since operating costs can be significantly reduced. For large facilities, the prices for new fluid range from € 15 per liter (in 2006) to € 22 per liter (in 2013), which is a large reinvestment, especially in light of filling volumes of 4000 liters to 7000 liters per unit. Using the aforementioned method, a price of € 8 per liter of recovered MDM can be achieved.
Tobias G. Erhart; Jürgen Gölz; Ursula Eicker; Martijn Van Den Broek. Working Fluid Stability in Large-Scale Organic Rankine Cycle-Units Using Siloxanes—Long-Term Experiences and Fluid Recycling. Energies 2016, 9, 422 .
AMA StyleTobias G. Erhart, Jürgen Gölz, Ursula Eicker, Martijn Van Den Broek. Working Fluid Stability in Large-Scale Organic Rankine Cycle-Units Using Siloxanes—Long-Term Experiences and Fluid Recycling. Energies. 2016; 9 (6):422.
Chicago/Turabian StyleTobias G. Erhart; Jürgen Gölz; Ursula Eicker; Martijn Van Den Broek. 2016. "Working Fluid Stability in Large-Scale Organic Rankine Cycle-Units Using Siloxanes—Long-Term Experiences and Fluid Recycling." Energies 9, no. 6: 422.
Ursula Eicker; Dirk Pietruschka; Maximilian Haag; Andreas Schmitt. Systematic design and analysis of solar thermal cooling systems in different climates. Renewable Energy 2015, 80, 827 -836.
AMA StyleUrsula Eicker, Dirk Pietruschka, Maximilian Haag, Andreas Schmitt. Systematic design and analysis of solar thermal cooling systems in different climates. Renewable Energy. 2015; 80 ():827-836.
Chicago/Turabian StyleUrsula Eicker; Dirk Pietruschka; Maximilian Haag; Andreas Schmitt. 2015. "Systematic design and analysis of solar thermal cooling systems in different climates." Renewable Energy 80, no. : 827-836.
Jürgen Schumacher; Dirk Pietruschka; Ursula Eicker. Commissioning and Operational Control of Photovoltaic Power Plants through Online Simulation. Energy Procedia 2014, 57, 152 -160.
AMA StyleJürgen Schumacher, Dirk Pietruschka, Ursula Eicker. Commissioning and Operational Control of Photovoltaic Power Plants through Online Simulation. Energy Procedia. 2014; 57 ():152-160.
Chicago/Turabian StyleJürgen Schumacher; Dirk Pietruschka; Ursula Eicker. 2014. "Commissioning and Operational Control of Photovoltaic Power Plants through Online Simulation." Energy Procedia 57, no. : 152-160.
A 7 MWth combined heat and power plant (CHP) based on an organic Rankine cycle (ORC) with 5.3 MWth and 1 MWel nominal output is analyzed. A district heating system serves as heat sink; the entire system is heat-led. Two examples for winter and summer operation are shown. The observed characteristics of the condenser are compared to results of a theoretical model. Variable mass flows, temperature levels (72 °C–95 °C) and temperature spreads result in varying condensation temperatures and pressure levels in the condenser (90 mbar to 150 mbar). High mass flows on the secondary side and related low temperature spreads improve the heat transfer and increase the condensation rate in the condenser. The monitoring data support the findings of a steady-state condenser model. As a consequence, advantageous load profiles according to the pressure characteristic of the system can be reached. Live steam pressure, pressure difference across the turbine, and flow rate increase. The effect on the electric efficiency is one percentage point in summer and 1.5 percentage points in winter, which translates to a difference in the electric yield of the cycle of about 10%. Furthermore, the data show that the transient sink conditions cause unsteady operation for the entire cycle.
Tobias G. Erhart; Ursula Eicker; David Infield. Influence of Condenser Conditions on Organic Rankine Cycle Load Characteristics. Journal of Engineering for Gas Turbines and Power 2013, 135, 042301 .
AMA StyleTobias G. Erhart, Ursula Eicker, David Infield. Influence of Condenser Conditions on Organic Rankine Cycle Load Characteristics. Journal of Engineering for Gas Turbines and Power. 2013; 135 (4):042301.
Chicago/Turabian StyleTobias G. Erhart; Ursula Eicker; David Infield. 2013. "Influence of Condenser Conditions on Organic Rankine Cycle Load Characteristics." Journal of Engineering for Gas Turbines and Power 135, no. 4: 042301.
Cities consume the vast majority of global energy and, therefore, are major contributors of worldwide CO2 and greenhouse gas emissions. Energy use is chiefly driven by how electricity is produced, how energy is utilized within buildings and how people and materials are moved around a city. Thus, many cities today are committed to increasing the energy efficiency of buildings and the fraction of renewables in energy budgets. However, quantitative data on energy performance and costs are rarely available, making it difficult for cities to effectively evaluate which energy-saving concepts work today and which will work best in the future. This article contributes to the analysis of urban energy performance through a detailed study of three urban case studies. The German case studies cover a medium-sized city (Ludwigsburg) and two city quarters under development (Munich) as well as a recently built (Ostfildern). Although in all cases, solar technologies have the highest potential for decentral renewable supply, the main renewable sources used are biomass and deep geothermal energy, the main reason being today's cost-effectiveness. The Munich case study showed that deep geothermal energy can produce renewable heat at less cost and emissions than biomass or conventional fuels, but there is no renewable contribution to the electricity demand. The 350 ha development will rely on large-scale photovoltaic (PV) integration for a renewable electricity contribution. In the low energy building quarter of Ostfildern, a biomass cogeneration plant covers 80% of the heating and 35% of the electricity consumption. Another 45% of the electricity consumption could be theoretically covered by rooftop PV. The monitoring results show that even on a city quarter scale, it is very difficult to achieve a 100% renewable supply of heating and electricity, if the consumption levels stay at current levels.
Ursula Eicker; Martin Klein. Large-scale renewable energy integration within energy-efficient urban areas: results from three German case studies. International Journal of Low-Carbon Technologies 2012, 9, 202 -213.
AMA StyleUrsula Eicker, Martin Klein. Large-scale renewable energy integration within energy-efficient urban areas: results from three German case studies. International Journal of Low-Carbon Technologies. 2012; 9 (3):202-213.
Chicago/Turabian StyleUrsula Eicker; Martin Klein. 2012. "Large-scale renewable energy integration within energy-efficient urban areas: results from three German case studies." International Journal of Low-Carbon Technologies 9, no. 3: 202-213.
Efficient heat rejection is crucial for the overall primary energy balance of sorption systems, as it dominates the auxiliary energy consumption. Low ratios of cooling power to auxiliary electricity of 3.0 or less are still common in sorption system, so that the primary energy efficiency is not always higher than for conventional compression chillers. Whereas dry heat rejection systems require electricity for fan operation, hybrid or wet cooling systems in addition need pumping energy for the cooling water and the water itself. The energy efficiency can be improved for heat rejection to the ground, where only pumping energy is needed for the geothermal heat exchange. Dynamic simulation models were used for a single effect absorption chiller powered by solar thermal collectors via a hot storage tank. The chiller models were coupled to a three dimensional numerical ground heat exchanger model or to cooling tower models. The models were validated with operating data of a 15 kW solar cooling system installed in an office building. Primary energy efficiency ratios were determined for different heat rejection systems and improved control strategies were developed. The installed system primary energy ratios varied between 1.1 and 2.2 for auxiliary heating and between 1.2 and 2.5 for auxiliary cooling depending on the heat rejection and control strategy chosen. The low electrical energy consumption of the geothermal heat rejection saves 30% of auxiliary electricity and results in an electrical coefficient of performance of 13. The maximum primary energy ratios for solar fractions up to 88% are 2.7 for auxiliary heating and 3.2 for auxiliary cooling, i.e. nearly three times higher than for the reference electrical compression system of 1.2.
Ursula Eicker; Dirk Pietruschka; Ruben Pesch. Heat rejection and primary energy efficiency of solar driven absorption cooling systems. International Journal of Refrigeration 2012, 35, 729 -738.
AMA StyleUrsula Eicker, Dirk Pietruschka, Ruben Pesch. Heat rejection and primary energy efficiency of solar driven absorption cooling systems. International Journal of Refrigeration. 2012; 35 (3):729-738.
Chicago/Turabian StyleUrsula Eicker; Dirk Pietruschka; Ruben Pesch. 2012. "Heat rejection and primary energy efficiency of solar driven absorption cooling systems." International Journal of Refrigeration 35, no. 3: 729-738.
Ursula Eicker; Aneta Strzalka; Tobias Erhart; Jose Antonio Perrella Balestieri. Low Energy City Quarters with High Renewable Fractions: Monitoring Results and Potential for Replication. International Journal of Sustainable Building Technology and Urban Development 2011, 2, 69 -79.
AMA StyleUrsula Eicker, Aneta Strzalka, Tobias Erhart, Jose Antonio Perrella Balestieri. Low Energy City Quarters with High Renewable Fractions: Monitoring Results and Potential for Replication. International Journal of Sustainable Building Technology and Urban Development. 2011; 2 (1):69-79.
Chicago/Turabian StyleUrsula Eicker; Aneta Strzalka; Tobias Erhart; Jose Antonio Perrella Balestieri. 2011. "Low Energy City Quarters with High Renewable Fractions: Monitoring Results and Potential for Replication." International Journal of Sustainable Building Technology and Urban Development 2, no. 1: 69-79.
Wie die nachhaltige Stadt der Zukunft aussehen könnte, zeigt der Stadtteil „Scharnhauser Park“ in Ostfildern bei Stuttgart. In diesem Quartier versuchen Wissenschaftler und Investoren, einen ganzen Stadtteil so optimal wie möglich nach nachhaltigen Gesichtspunkten zu gestalten.
Ursula Eicker; Tobias Erhart; Frank Hettler; Ursula Pietzsch; Aneta Strzalka. Auf dem Weg zum nachhaltigen Stadtviertel. Ökologisches Wirtschaften - Fachzeitschrift 2011, 26, 1 .
AMA StyleUrsula Eicker, Tobias Erhart, Frank Hettler, Ursula Pietzsch, Aneta Strzalka. Auf dem Weg zum nachhaltigen Stadtviertel. Ökologisches Wirtschaften - Fachzeitschrift. 2011; 26 (1):1.
Chicago/Turabian StyleUrsula Eicker; Tobias Erhart; Frank Hettler; Ursula Pietzsch; Aneta Strzalka. 2011. "Auf dem Weg zum nachhaltigen Stadtviertel." Ökologisches Wirtschaften - Fachzeitschrift 26, no. 1: 1.
Component performance and seasonal operational experiences have been analysed for desiccant cooling systems powered by solar air collectors. Measurements during the commissioning phase in Spain (public library) and in Germany (production hall) showed that the dehumidification efficiency of the sorption rotors was 80% and the humidification efficiency of the contact evaporators was 85–86%. Only in a two-stage desiccant system monitored in China (laboratory building), a dehumidification efficiency of 88% was reached. The rotary heat exchangers only had 62–68% measured heat recovery efficiency, which is lower than specified. Seasonal performance monitoring carried out in the German installation showed that average seasonal COP’s were close to 1.0, when related to all operation hours. COP’s increase if low regeneration temperatures are used with low dehumidification rates, which is often sufficient for moderate German climatic conditions, but much less so in the humid Chinese climate. Electrical COP’s for the German system including air distribution were between 1.7 and 4.6 and reach values of 7.4, when only additional pressure drops of the desiccant unit are considered. It could be shown that conventional control strategies lead to high auxiliary energy consumption, for example if fixed heating setpoint temperatures are used. Furthermore the solar air collector energy yield was very low in the German system, as regeneration was only used when all other options such as humidification at high air volume flows did not reduce the room air temperature enough. The studies showed that the measured auxiliary energy consumption could be reduced to near zero, if regeneration temperature setpoints were not fixed to constant values. The solar air collector efficiency was good at about 50% both for the flat plate collectors used in Spain and Germany and the Chinese vacuum tube solution. A cost analysis demonstrated the viability of the concept, if some funding of the high investment costs is provided.
Ursula Eicker; Dietrich Schneider; Jürgen Schumacher; Tianshu Ge; Yanjun Dai. Operational experiences with solar air collector driven desiccant cooling systems. Applied Energy 2010, 87, 3735 -3747.
AMA StyleUrsula Eicker, Dietrich Schneider, Jürgen Schumacher, Tianshu Ge, Yanjun Dai. Operational experiences with solar air collector driven desiccant cooling systems. Applied Energy. 2010; 87 (12):3735-3747.
Chicago/Turabian StyleUrsula Eicker; Dietrich Schneider; Jürgen Schumacher; Tianshu Ge; Yanjun Dai. 2010. "Operational experiences with solar air collector driven desiccant cooling systems." Applied Energy 87, no. 12: 3735-3747.
One of the first rehabilitated passive energy standard office buildings in Europe was extensively monitored over two years to analyse the cooling performance of a ground heat exchanger and mechanical night ventilation together with the summer comfort in the building. To increase the storage mass in the light weight top floor, phase change materials (PCM) were used in the ceiling and wall construction. The earth heat exchanger installed at a low depth of 1.2 m has an excellent electrical cooling coefficient of performance of 18, but with an average cooling power of about 1.5 kW does not contribute significantly to cooling load removal. Mechanical night ventilation with 2 air changes also delivered cold at a good coefficient of performance of 6 with 14 kW maximum power. However, the night air exchange was too low to completely discharge the ceilings, so that the PCM material was not effective in a warm period of several days. In the ground floor offices the heat removal through the floor to ground of 2–3 W m−2 K−1 was in the same order of magnitude than the charging heat flux of the ceilings. The number of hours above 26 °C was about 10% of all office hours. The energy performance of the building is excellent with a total primary energy consumption for heating and electricity of 107–115 kW h m−2 a−1, without computing equipment only 40–45 kW h m−2 a−1.
Ursula Eicker. Cooling strategies, summer comfort and energy performance of a rehabilitated passive standard office building. Applied Energy 2010, 87, 2031 -2039.
AMA StyleUrsula Eicker. Cooling strategies, summer comfort and energy performance of a rehabilitated passive standard office building. Applied Energy. 2010; 87 (6):2031-2039.
Chicago/Turabian StyleUrsula Eicker. 2010. "Cooling strategies, summer comfort and energy performance of a rehabilitated passive standard office building." Applied Energy 87, no. 6: 2031-2039.
The paper contributes to the system design of solar thermal absorption chillers. A full simulation model was developed for absorption cooling systems, combined with a stratified storage tank, steady-state or dynamic collector model and hourly resolved building loads. The model was validated with experimental data from various solar cooling plants. As the absorption chillers can be operated at reduced generator temperatures under partial load conditions, the control strategy has a strong influence on the solar thermal system design and performance. It could be shown that buildings with the same maximum cooling load, but very different load time series, require collector areas varying by more than a factor 2 to achieve the same solar fraction. Depending on control strategy, recooling temperature levels, location and cooling load time series, between 1.7 and 3.6 m2 vacuum tube collectors per kW cooling load are required to cover 80% of the cooling load. The cost analysis shows that Southern European locations with higher cooling energy demand lead to significantly lower costs. For long operation hours, cooling costs are around 200 € MWh−1 and about 280 € MWh−1 for buildings with lower internal gains and shorter cooling periods. For a Southern German climate, the costs are more than double.
Ursula Eicker; Dirk Pietruschka. Design and performance of solar powered absorption cooling systems in office buildings. Energy and Buildings 2008, 41, 81 -91.
AMA StyleUrsula Eicker, Dirk Pietruschka. Design and performance of solar powered absorption cooling systems in office buildings. Energy and Buildings. 2008; 41 (1):81-91.
Chicago/Turabian StyleUrsula Eicker; Dirk Pietruschka. 2008. "Design and performance of solar powered absorption cooling systems in office buildings." Energy and Buildings 41, no. 1: 81-91.
External cooling loads of a building façade are caused mainly by shortwave irradiance transmission, but also secondary heat flows from the internal glass panes and through ventilation gains from the façade. In a double façade with sun-blinds in the air gap, thermal energy is produced through absorption on the blinds. The work quantifies the thermal performance of single and double façades under summer conditions using laboratory and full scale building experiments. The experimental results were used for model validation and parameter studies were done using dynamic building simulation tools. While the measured sun-blind surface temperature reached up to 45 °C, the air temperature increase in a one storey high double façade was between 3 and 5 K, with peak values of 8 K. For typical absorption coefficients between 10 and 30% the summer thermal energy produced ranges between 50 and 100kWhmfaçade−2. Depending on the ventilation rates between façade and room, only an air flow fraction of about 10% enters the room and adds to the cooling loads. Additional summer cooling loads through façade ventilation of 2–5 kWh m−2 room surface were obtained. The measured total energy transmittance of shaded double façades was about 10%, nearly independent of blind position and opening cross section, so that short wave irradiance can be effectively blocked with sun-blinds. Secondary heat flows only play a role if no shading system is used and are otherwise negligible.
U. Eicker; V. Fux; U. Bauer; L. Mei; D. Infield. Façades and summer performance of buildings. Energy and Buildings 2007, 40, 600 -611.
AMA StyleU. Eicker, V. Fux, U. Bauer, L. Mei, D. Infield. Façades and summer performance of buildings. Energy and Buildings. 2007; 40 (4):600-611.
Chicago/Turabian StyleU. Eicker; V. Fux; U. Bauer; L. Mei; D. Infield. 2007. "Façades and summer performance of buildings." Energy and Buildings 40, no. 4: 600-611.