• Energy Research

AbstractThe international building sector plays an important role on energy policy and reduction of CO2 emissions. The focus of energy conservation has started from building level and nowadays expands to district, city, region or national level. In this study, an overview, performed within the European project Sinfonia for preparation of a new district tool with focus on energy conservation, will be presented about existing district tools. Several aspects of the tools were included in the overview, such as focus, aim, analytical approach, methodology, geographical coverage, required input data, commercial/freeware, source code, language, tool status, organization/project developing the tool, and web link. The main components of energy district tools such as 3D geographical data, data for building features and properties, and simulation methods were also addressed.Additionally, the issue of appropriate boundary conditions on urban energy analysis, such as user behaviour, will be discussed. A simulation study of a dwelling in various energy standards including different occupant scenarios was performed, and as a result, a formula was developed to estimate an equivalent heating reference temperature as a function of building envelope, living area, and outdoor temperature. Thus, the estimated equivalent heating reference temperature can be used as input in district energy simulations, instead of a constant set point value independent of the building.The present study can serve as a basis for new or further development of tools trying to cover the gap and the limits of the existing ones.

The use of heat pumps in buildings is one of the best and often the only option for the decarbonization of the building stock. District heating seems a promising solution in urban areas and in existing buildings when the use of heat pumps is restricted and also technically and economically challenging (source exploitation, space restrictions, sound emissions, etc.). Heat pumps can be integrated in various ways in buildings and district heating systems: large central high-temperature heat pumps in district heating, medium-size heat pumps block- or building-wise or small heat pumps decentral apartment-wise. The best option depends on the individual district heating CO2 emissions and the electricity mix as well as on the perspective of the building owner versus that one of the district heating system and its future development. Austrian examples of district heating systems and different variants of integrating heat pumps are investigated in a comprehensive way by means of an energetic and environmental simulation-based analysis. This assessment includes a detailed investigation of the capabilities of the booster heat pump to increase the PV own-consumption and is also expanded to include various scenarios for the development of the electricity mix and the decarbonisation of district heating.

Abstract An energy auditing tool (PHPP) was evaluated against a dynamic simulation tool (TRNSYS) and used for the assessment of energy conservation measures in a demo case study. The comprehensive comparison of useful heating and cooling demands and loads included three building types (single-, multi-family house, and office), three building energy levels (before renovation and after renovation with a heating demand of 45 and 25 kWh/(m²·a)) and seven European climates. Dynamic simulation results proved PHPP (monthly energy balance) to be able to calculate heating demand and energy savings with good precision and cooling demand with acceptable precision compared to detailed numerical models (TRNSYS). The average deviation between the tools was 8% for heating and 15% for cooling (considering climates with a relevant cooling load only). The higher the thermal envelope quality was, i.e. in case of good energy standards and in cold climates, the better was the agreement. Furthermore, it was confirmed that PHPP slightly overestimates the heating and cooling loads by intention for system design. The renovation design of a real multi-family house was executed using PHPP as energy auditing tool. Several calculation stages were performed for (a) baseline, (b) design phase, and (c) verification with monitoring in order to calculate the corresponding heating demand. The PHPP model was calibrated twice, before and after the renovation. The necessity for tool calibration, especially for the baseline, was highlighted increasing the confidence with respect to a number of boundary conditions. In this study, PHPP was tested as an energy auditing tool aiming to be a versatile and less error-prone alternative to more complex simulation tools, which require much more expert knowledge and training.

To address the huge market of renovation of multi-apartment buildings, minimal-invasive decentral serial-renovation solutions are required. One major challenge in the design of decentral heat pumps is to find the optimal balance between, on one hand, compactness and pleasant design, and on the other hand, efficiency and minimal sound emissions. A comprehensive holistic design and optimization process for the development of decentral heat pumps, from the component level, to the system level, and up to the building level, is developed. A novel façade-integrated speed-controlled exhaust air to supply air heat pump combined with a mechanical ventilation system with heat recovery and recirculation air was developed and simulated in a reference flat. Compared to a traditional supply air heat pump without recirculation, it shows only slight performance improvement, but allows significantly better thermal comfort and control, independently from the hygienic air flow rate and from the heating and cooling loads. Detailed measurement and simulation results are presented for several functional models with heating power of around 1 kW up to 2.5 kW. The design was optimized by means of CFD simulations to allow for low pressure drop, homogeneous flow, and low sound emissions. Moreover, mock-ups of innovative façade-integrated heat pump outdoor units are presented.

Abstract The very low heating load of deep renovated buildings following standards such as EnerPHit, and the limited space in renovation create the need for compact heating systems. An innovative heating and ventilation system - consisting of an exhaust air to supply air heat pump combined with a heat recovery ventilation unit, both integrated into a prefabricated timber frame facade - was developed and installed in a flat during the renovation of a multi-family house in Ludwigsburg, Germany. The system and the flat were monitored for the complete heating season 2016/2017. This paper presents: (a) an analysis of the monitoring data, (b) the development and validation of the models of the system and the flat, and (c) the results of the dynamic simulations that were performed for further system optimisation. Inside the flat, good thermal comfort and indoor air quality conditions were achieved. The monitored SPF of the system was 2.8. Simulation results showed that with the optimised system and control, there can be an electricity savings of 25%. The developed system has the potential to be cost-effective due to prefabrication and low heating capacity. It represents a compact solution with moderate energy performance, appropriate for minimally disruptive renovations.

In this paper, dynamic simulation was used to compare the energy performance of three innovativeHVAC systems: (A) mechanical ventilation with heat recovery (MVHR) and micro heat pump, (B) exhaustve ...

Abstract A new residential district will be built in Innsbruck, Austria. The energy and environmental impact are considered during the decision-making procedure. A complete and comprehensive simulation study was performed to develop a decision support tool with respect to a) which type of heating system i.e. heat pumps, connection to district heating, or natural gas boilers, b) which level of centralization of the heating system i.e. from one central solution for the entire district up to decentral systems located in each flat, c) which type of heat distribution system and d) the corresponding pipe insulation level. To compare the aforementioned combinations, various key performance indicators were calculated, using two different calculation methods: one with annual and one with monthly conversion factors. The results show that the use of heat pumps or district heating instead of gas boilers decreases the carbon emissions by a maximum of 75% and 52%, respectively. The choice of the appropriate key performance indicator and calculation method had a minor influence on the ranking of the investigated solutions but a significant influence on the quantitative results.

The majority of existing building stock in Europe and worldwide is poor energy performance buildings and renovation plays a major role in achieving climate protection and energy independence. Deep renovation solutions in combination with integrated HVAC systems are developed within the framework of the European project iNSPiRe. The development, testing and modelling of a façade integrated micro-heat pump (μ-HP) in combination with mechanical ventilation with heat recovery (MVHR) is presented. A detailed physical model of the μ-HP is developed within the Matlab simulation environment. The vapour cycle and the air heating/cooling are modelled in steady state to derive the thermodynamic states of the refrigerant and of the air. The refrigerant cycle and the governing equations for the moist air are solved iteratively. Two functional models (dimensions: 2.75 m x 2.75 m) were built for the tests in PASSYS test cells, which allow controlling the temperature with high-power heater and cooler. With a so-called cold box the external boundary conditions can be emulated. Experimental results are used to validate the physical heat pump and MVHR model. The physical model is used to create the performance map data for building and system simulation. Combined building and HVAC simulations are performed to investigate the energy performance of the μ-HP on building level. The performance of the system is investigated for different renovation standards (EnerPHit and Passive House) and for seven different European climate conditions. Different control strategies are investigated and a frosting model is used to optimize defrosting control and thus to reduce energy demand. A functional model will be later monitored in a demo building in Ludwigsburg, Germany. The example of social housing built in the 1970s contains four flats on four stories. The main advantages of the μ-HP are the compactness, providing the possibility of integration into the façade, and cost reduction.