Building Heat Demand Research Articles

Creating Comparability among European Neighbourhoods to Enable the Transition of District Energy Infrastructures towards Positive Energy Districts

Planning the required energy infrastructure for the energy transition is a crucial task for various neighbourhood concepts, such as positive energy districts. However, energy planning often comes with the challenges of data shortages and a lack of comparability among solutions for different districts. This work aims to enable this comparability by introducing an approach for categorising districts according to parameters that are relevant for the planning of neighbourhood energy infrastructures. Four parameters (climate, floor space index, heating demand and share of residential buildings) and their respective ranges (bands) were derived from the literature. Additionally, this work visualised the combination of all parameter bands across Europe to conveniently showcase districts that are comparable according to the selected parameters. This approach and its visualisation could be used in urban planning to share knowledge from existing energy district projects with those planned in comparable districts.

System modelling and optimization of a low temperature local hybrid energy system based on solar energy for a residential district

Utilizing solar energy for heat supply can reduce CO2 emissions and mitigate global climate change. In the Nordic region (e.g., Iceland and Finland), a tremendous seasonal mismatch exists between the availability of solar radiation and building heating demand. This paper proposes a local hybrid energy system based on solar energy for a residential district. It applies a borehole thermal energy storage to store solar energy in non-heating seasons, and uses stored energy for part of total heating demand in a residential neighbourhood in heating seasons. Photovoltaic panels are used to generate electricity for heat pump operation. To find out cost-optimal and eco-friendly solutions, the local energy system was first modelled and simulated in TRNSYS. Then, genetic algorithms were applied to optimize the system performance and costs. In optimal solutions, 38%-58% of total heating demand could be covered by on-site heat energy with the levelized cost of energy of 110–184 €/MWh. On this basis, importing additional electricity from grid to increase the utilization rate of air-to-water heat pumps can further increase the on-site heat energy fraction to 41%-88% with the levelized cost of energy of 108–201 €/MWh. Compared with the situation of fully district heating input, the proposed system can annually reduce CO2 emissions by 102–217 tons with the rate of 31–66%. Although the initial cost of the studied system is higher than that of district heating, the local hybrid energy system is worth further developing considering decentralizing heat energy production and reducing CO2 emissions.

Energy Transition Pathways for Deep Decarbonization of the Greater Montreal Region: An Energy Optimization Framework.

More than half of the world’s population live in cities, and by 2050, it is expected that this proportion will reach almost 68%. These densely populated cities consume more than 75% of the world’s primary energy and are responsible for the emission of around 70% of anthropogenic carbon. Providing sustainable energy for the growing demand in cities requires multifaceted planning approach. In this study, we modeled the energy system of the Greater Montreal region to evaluate the impact of different environmental mitigation policies on the energy system of this region over a long-term period (2020–2050). In doing so, we have used the open-source optimization-based model called the Energy–Technology–Environment Model (ETEM). The ETEM is a long-term bottom–up energy model that provides insight into the best options for cities to procure energy, and satisfies useful demands while reducing carbon dioxide (CO2) emissions. Results show that, under a deep decarbonization scenario, the transportation, commercial, and residential sectors will contribute to emission reduction by 6.9, 1.6, and 1 million ton CO2-eq in 2050, respectively, compared with their 2020 levels. This is mainly achieved by (i) replacing fossil fuel cars with electric-based vehicles in private and public transportation sectors; (ii) replacing fossil fuel furnaces with electric heat pumps to satisfy heating demand in buildings; and (iii) improving the efficiency of buildings by isolating walls and roofs.

Low energy demand scenario for feasible deep decarbonisation: Whole energy systems modelling for Ireland

Typically, energy system decarbonisation scenarios neglect the mitigation opportunities from reducing and restructuring energy service demands (ESDs), focusing instead on technology and fuel substitutions. Models tend to be designed to factor technologies explicitly while ESDs are exogenous. However, existing literature suggests that the scale and speed of decarbonisation required to limit global warming to 1.5∘ C by the end of the century requires a shift in energy demands to avoid the need for large-scale negative emission technologies. This can be brought about by major structural changes in drivers of demand such as transport modal shifting, substituting emission intensive materials like cement, and reducing building heat demand through behaviour change and efficiency. Ireland, the subject of this paper, has legislated one of the most ambitious decarbonisation targets in the world: the need to understand the role of demand shift is paramount. To fill this gap, the Irish Low Energy Demand (ILED) mitigation narrative is developed and applied to the TIMES-Ireland Model (TIM), an energy systems optimisation model. ILED represents a scenario where ESDs are decoupled from economic growth by shifting travel, increasing end-use efficiency, densifying urban settlement, focusing on low-energy intensive economic activities and changing social infrastructure. Compared to a scenario where ESDs follow ‘Business-as-usual’ growth, ILED enables the achievement of steep decarbonisation targets with a less rapid energy system transformation, lower capital and marginal abatement costs, and with lower reliance on the deployment of novel technologies.

Source-to-sink efficiency of blue and green district heating and hydrogen-based heat supply systems

Hydrogen is commonly mentioned as a future proof energy carrier. Hydrogen supporters advocate for repurposing existing natural gas grids for a sustainable hydrogen supply. While the long-term vision of the hydrogen community is green hydrogen the community acknowledges that in the short term it will be to large extent manufactured from natural gas, but in a decarbonized way, giving it the name blue hydrogen. While hydrogen has a role to play in hard to decarbonize sectors its role for building heating demands is doubtful, as mature and more energy efficient alternatives exist. As building heat supply infrastructures built today will operate for the decades to come it is of highest importance to ensure that the most efficient and sustainable infrastructures are chosen. This paper compares the source to sink efficiencies of hydrogen-based heat supply system to a district heating system operating on the same primary energy source. The results show that a natural gas-based district heating could be 267% more efficient, and consequently have significantly lower global warming potential, than a blue hydrogen-based heat supply A renewable power-based district heating could achieve above 440% higher efficiency than green hydrogen-based heat supply system.

Climate Change Effects on Heating and Cooling Demands of Buildings in Canada

Climate change is causing more frequent extreme weather events. The consequences of increasing global temperature on the operating cost of existing buildings, and the associated health, safety, and economic risks were investigated. Eight cities in Ontario, Canada, across climate zones 5 to 8, were selected for this study. Statistical models were employed to forecast daily temperatures for 50 years. The impact of climate change on buildings’ heating and cooling demands for energy was measured as changes in heating degree days (HDD) and cooling degree days (CDD) compared to current design requirements. The results predict an increase in the demand for cooling and a decrease in that for heating within the next 50 years. A drop in the total HDD and CDD is shown which reflects a more comfortable outdoor thermal condition. Risk to human health attributable to the increase in global temperature is negligible.

Assessment of the Possibility of Using Various Types of Renewable Energy Sources Installations in Single-Family Buildings as Part of Saving Final Energy Consumption in Polish Conditions

The aim of this work is to develop a model of heat supply to buildings with almost zero energy consumption, indicating the significant importance of heat losses and gains in heating installations. The prepared model is to indicate the need for changes in the structure and topology of heating installations, resulting from the changing heat demand of buildings. The need to create a new model is heightened by changes that relate to tightening legal regulations related to energy consumption and demand, which must meet the standards of buildings in Poland from 2021. The article presents the assumptions and results of analyses of the use of energy installations in residential buildings that use renewable energy sources to balance energy consumption in various areas of its use. To achieve this goal, calculations were made using simulations of the impact of the use of installations using renewable energy sources on the energy performance of a building with different quality of partitions and improvement of energy efficiency in accordance with the Polish standard PN-EN 12831. The test results allow to choose the most advantageous, from the point of view of economic profitability, option of replacing installations in residential buildings, and they also allow to determine the possibilities of meeting national obligations in the field of final energy reduction and increasing the share of renewable energy sources in meeting its demand in accordance with the EU obligations imposed on Poland. Thermomodernization of buildings in the temperate climate zone allows for a reduction of 38% of energy demand over the entire life cycle of a building and a reduction of CO2 emissions by 99%.

Robust Optimisation of Building Retrofits for Present versus Future Climate Scenarios in Humid Continental Climates (Dfb subtype) to Reduce Heating Demand and Mitigate Future Overheating Risk

The outdoor environment is a major driver of building performance; a changing climate poses a significant challenge to the effective deployment of building retrofits. The Dfb Köppen climate zone, a humid continental climate with warm summer subtype, is poised to confront significant annual and seasonal temperature changes within the next thirty years. This study examined the relationship between retrofits’ ability to reduce heating demand and simultaneously mitigate future overheating risk. A low-rise apartment was used as the basis of a multi-objective design optimisation (MODO) that modelled building heating demand and overheating risk across a series of input variables, considered either optimisable (i.e.: building envelope upgrades) or non-optimisable (i.e.: occupancy profiles) in the context of this study. The metric overheating-degree-hours (OHDH) was utilised to assess overheating risk. The results of this study reinforced previous findings indicating envelope upgrades can significantly reduce heating demand, but also underscored the importance of implementing solar heat gain mitigation strategies for overheating risk reduction. Additionally, the study highlighted the appropriateness of amalgamated weather data for performance analysis.

Estimation of shallow geothermal potential to meet building heating demand on a regional scale

Extracting shallow geothermal energy using borehole heat exchangers (BHEs) can help decarbonising the residential heating sector, particularly where no other low-carbon heating solutions are readily available. To assist urban planners and policy makers in developing carbon-neutral heating plans, the regional technical shallow geothermal potential must be known. Here, we calculate the technical geothermal potential of BHE fields on a regional scale while taking potential thermal interference between BHEs, geological conditions, as well as space available for BHE installation into account. The number of BHEs placed is maximized and heat extraction rate from each BHE is optimized taking regional regulations into account. When the methodology is applied to the German state of Baden-Württemberg on a building-block scale, results suggest an annual technical potential of 33.5 TWh. We then link this technical geothermal potential to heating demand scenarios on a building block scale and the results show that, depending on the renovation status of the buildings, between 44% and 93% of all building blocks can be heated using only BHEs. This allows for a rapid identification of building blocks for which BHEs are not able to meet the heating demand and where other means of heat supply will be needed.

Exploring the Long-Term Development of the Ukrainian Energy System

This study analyses the Ukrainian energy system in the context of the Paris Agreement and the need for the world to limit global warming to 1.5 °C. Despite ~84% of greenhouse gas emissions in Ukraine being energy- and process-related, there is very limited academic literature analysing long-term development of the Ukrainian energy system. This study utilises the TIMES-Ukraine model of the whole Ukrainian energy system to address this knowledge gap and to analyse how the energy system may develop until 2050, taking into current and future policies. The results show the development of the Ukrainian energy system based on energy efficiency improvements, electrification and renewable energy. The share of renewables in electricity production is predicted to reach between 45% and 57% in 2050 in the main scenarios with moderate emission reduction ambitions and ~80% in the ambitious alternative scenarios. The cost-optimal solution includes reduction of space heating demand in buildings by 20% in frozen policy and 70% in other scenarios, while electrification of industries leads to reductions in energy intensity of 26–36% in all scenarios except frozen policy. Energy efficiency improvements and emission reductions in the transport sector are achieved through increased use of electricity from 2020 in all scenarios except frozen policy, reaching 40–51% in 2050. The stated policies present a cost-efficient alternative for keeping Ukraine’s greenhouse gas emissions at today’s level.

A machine-learning model for the prediction of aggregated building heating demand from pan-European land-use maps

Aggregated building energy demand is a useful indicator for urban energy planning. It can be used by planners and decision-makers to identify clusters of high energy demand in a given urban area and efficiently plan, for example, district heating networks. Various data sources exist at the pan-European level describing land use and built areas. Combined with statistical data, such maps have been used in previous research for estimating building energy performance aggregated at the hectare level, using engineering assumptions. In this paper, we show that large-scale land-use maps alone can be used for predicting annual building energy demand with an accuracy comparable to the one of previous engineering models. We hence present a preliminary method based on Convolutional Neural Networks at different spatial resolutions. The resulting model was trained and tested in an area of about 170 km1 in Geneva (Switzerland) using a local annual heating demand dataset comprising 16239 buildings. On a 300-m aggregation tile, the obtained mean error (14.3%) is significantly reduced compared to the one of a simple linear model (37.2%). Using solely land-use data, we also achieve similar results for a 100-m tile as those of an engineering model from the literature.

There’s no place like home – The impact of residential heterogeneity on bottom-up energy system modeling

Building heating demand makes up about a third of final energy consumption in Germany. Increasing energy efficiency and switching to alternative heating technologies, e.g., based on renewable energies, plays a pivotal role in achieving greenhouse gas emission targets in the building sector. In developing meaningful and efficient policies such as incentive schemes, a thorough understanding of the building sector structures and heating systems is crucial. To approach the said matter, we couple an urban energy system platform to assess single building heat demands based on geometrically exact 3D building models (SimStadt) with a mixed-integer linear program (MILP) for cost-optimization of residential technology investment and operation (COMODO). We apply the novel bottom-up model framework to show the loss of heterogeneity in actual building geometries and their physical properties induced by using simplified approaches with archetypal buildings. In the analysis, 100 buildings of the same TABULA building type are simulated and optimized with the proposed model framework. We assess heterogeneity on several levels, including net energy demand, the choice of cost-optimal heating system, and final energy demand: for example, specific heating demand varies by 20% between the 100 case study buildings which would have hitherto considered to have equal demand. This spread shows that details such as building geometries are a critical factor in modeling energy systems on a local scale.

Data driven model for heat load prediction in buildings connected to District Heating by using smart heat meters

An accurate characterization and prediction of heat loads in buildings connected to a District Heating (DH) network is crucial for the effective operation of these systems. The high variability of the heat production process of DH networks with low supply temperatures and derived from the incorporation of different heat sources increases the need for heat demand prediction models. This paper presents a novel data-driven model for the characterization and prediction of heating demand in buildings connected to a DH network.This model is built on the so-called Q-algorithm and fed with real data from 42 smart energy meters located in 42 buildings connected to the DH in Tartu (Estonia). These meters deliver heat consumption data with a 1-h frequency. Heat load profiles are analysed, and a model based on supervised clustering methods in combination with multiple variable regression is proposed. The model makes use of four climatic variables, including outdoor ambient temperature, global solar radiation and wind speed and direction, combined with time factors and data from smart meters. The model is designed for deployment over large sets of the building stock, and thus aims to forecast heat load regardless of the construction characteristics or final use of the building. The low computational cost required by this algorithm enables its integration into machines with no special requirements due to the equations governing the model.The data-driven model is evaluated both statistically and from an engineering or energetic point of view. R2 values from 0.70 to 0.99 are obtained for daily data resolution and R2 values up to 0.95 for hourly data resolution. Hourly results are very promising for more than 90% of the buildings under study.

A finite-volume method for full-scale simulations of coaxial borehole heat exchangers with different structural parameters, geological and operating conditions

The coaxial borehole heat exchangers (BHEs) are commonly used for efficient heat exchange between the heat carrier (usually water) and geothermal energy. Driven by the demand for the performance evaluation of extremely large length-diameter ratio BHEs under various working conditions in the practical engineering, this article presents a high-efficiency finite-volume computational model using variable-length control volumes to study the thermal behaviors of coaxial BHEs. The solution method is validated using data collected from three wells of 47.2 m, 879.6 m and 2,600.0 m depths. It is also used to guide the structural design and performance optimization of BHEs. The comparisons show that the present method can accurately predict the BHE performance with different structures, geological conditions and operating modes. With more reasonable thermal conductivity values, an approximate 100 kW deviation between the predicted and test heat exchange rates was avoided, and RMSE of the outlet temperature was improved from 4.09 to 0.82 for a 2,600 m BHE. The application of the proposed method in engineering projects indicates that setting the periodic operation interval of geothermal wells, according to the building types and heating demand, is an important factor to optimize the utilization of geothermal energy for space heating.

A circular economy approach to building heating: The role of exergy in policymaking

Building heating accounts for 17% of the United Kingdom’s (UK) direct greenhouse gas (GHG) emissions and is the third largest emitter after surface transport and industry. There is a significant potential for building CO2 emission reductions to contribute towards the UK’s 2050 net zero-carbon target.The UK Government’s approach to decarbonising building heating centres on reducing the energy demand of buildings and displacing the use of fossil fuels with low to zero-carbon and renewable energy technologies. While this approach can minimise energy consumption, it continues to quickly downcycle resources through a linear economy approach of take–make–waste. There is no consideration of how effective the technologies are in their efficient use of the primary energy resources (PER), with some technologies being far more wasteful in terms of energy resource consumption than others. This strategy will lead to an increasing, and avoidable burden on the national electricity infrastructure as heat becomes increasingly electrified towards 2050 and that will translate to higher costs for both consumers and the economy. A similar outcome would result from the use of renewable electricity to produce hydrogen for building heating.Larger cities have more local heat sources available in the form of waste heat and environmental heat (in the ground and water) than there is building heat demand. A circular economy approach requiring new regulation and policy can prioritise the reuse of these freely available heat sources enabled by heat networks to realise a more sustainable approach to building heating. This will ultimately result in the decoupling of resource consumption from its depletion, which is a key circular economy principle.Exergy analysis used in city energy planning can identify and prioritise those more resource-efficient system options that utilise local heat sources and better conserve primary energy resources. The implementation of more resource-efficient heat supply systems can reduce energy resource consumption by over two-thirds and avoid the need to reinforce the national electrical infrastructure thus keeping citizens’ heating costs down.

Simulation-based design optimization of heat pump systems considering building variations

Heat pump systems (HPS) are a promising technology to reduce greenhouse gas emissions in the building sector by low-emission heat supply. However, their market penetration is inhibited by lower costs of conventional technologies. Thus, heat pumps must become cheaper to purchase and operate. Investment costs are related to the design, while operating costs are related to operational efficiency. Although design and operation are mutually interdependent, they are considered separately in conventional design procedures. This disconnect prevents the full potential of the technology from being realized.In this contribution, we present a framework to simultaneously consider design and operation in one optimization step using a simulation-based optimization approach called HPS eOD Design. Based on a building heat demand, the framework optimizes annualized costs and emissions of heat pump systems considering the operational behaviour already in the design. By coupling the optimization program with a software for automatic generation of building models called TEASER, HPS eOD Design can be applied to a wide variety of building types and locations.Optimization results reveal that optimizing heat pump system sizing improves annualized costs and emissions for six examined buildings by up to 8.2% in costs and 12.7% in emissions compared to sizings derived by the conventional design procedure VDI4645. To exploit even further potential, the integration of operational optimization within the design is highly recommended. In addition, a more detailed modeling approach of the building should be implemented in HPS eOD Design. Both measures lead to an acceleration of the building sector defossilization.

Modelling of Solar Irradiance Incident on Building Envelopes in Polish Climatic Conditions: The Impact on Energy Performance Indicators of Residential Buildings

In this study, we use the data of Polish typical meteorological years and 15 transposition models to obtain global solar irradiance on sloped surfaces to calculate solar irradiance on external building partitions, solar gains, heating demands, and primary nonrenewable energy for heating and domestic hot water (EPH+W) of two typical Polish residential buildings, each for two variants in five locations. In relation to TMYs, annual solar gains were lower by −31% and −36% on average in a single and multifamily building, respectively, and the annual heating demands increased by 9% and 16%, respectively. Consequently, averaged EPH+W in relation to TMYs rose by 1.4 kWh/m2 and 4.5 kWh/m2, respectively. The mean differences between TMYs and the new method from the recently published EN-ISO 52010 standard for test Building 1 were 1.6 and 1.2 kWh/m2, for Variants 1 and 2, respectively. Similarly, for test Building 2, the mean differences were 5.1 kWh/m2 and 3.9 kWh/m2, respectively. This means that the simulation model that is chosen has a visible impact on a building’s energy performance indicators and its rating without any changes in the physical structure and use of the building.

Long term performance monitoring and KPIs’ evaluation of Aquifer Thermal Energy Storage system in Esker formation: Case study in Stockholm

The majority of Aquifer Thermal Energy Storage (ATES) systems studies have been conducted in aquifer systems located in large sand aquifers. Esker formation present a more challenging geometrical complexity compared to typical sand aquifers. This study aims to conduct comprehensive and long term performance evaluation of doublet type ATES system in esker geological formation in Stockholm, Sweden. The total heating and cooling used from the ATES are 673 MWh and 743 MWh respectively during the first 3 annual storage cycles of operation. The licensed total amount of water extraction and injection is 50 liters per second with undisturbed groundwater temperature of 9.5°C. Over the first three storage cycles, the average injection and extraction temperatures for the warm side are 13.3°C and 12.1°C, and for the cold side 7.6°C and 10.5°C. The average temperature differences across the main heat exchanger from the ATES side are 4.5 K during winter and 2.8 K during summer which is 4-5 degrees lower than the optimum value. The average thermal recovery efficiency over the first 3 storage cycles were 47 % and 60 % for warm and cold storages respectively. The data analysis indicated annual energy and hydraulic imbalances which results into undesirable thermal breakthrough between the warm and cold side of the aquifer. This was mainly due to suboptimal operation of the building energy system which led to insufficient heat recovery from the warm side, and subsequently insufficient cold injection in the cold wells, despite the building heating demand and the available suitable temperatures in the ATES. The cause of the suboptimal operation is the oversizing of the heat pumps which were designed to be coupled to larger thermal loads as compared to the ones in the final system implementation. As a result, the heat pumps could not be operated during small-medium loads. Additionally, the paper discusses the limitations of currently used energy and thermal key performance indicators (KPI) for ATES and propose an additional thermal KPI named heat exchanger efficiency balance (βHEX) that connects and evaluate the optimum operational point of temperature differences from both the building and ATES prospective. In addition to ATES energy and hydraulic KPIs, βHEX can contribute in providing more complete picture on the ATES-building interaction performance as well as highlights if the losses in energy recovery from ATES are due to the subsurface processes or building energy system operation which has been proven to be critical for the optimum ATES performance.

Impact of wastewater heat recovery in buildings on the performance of centralized energy recovery – A case study of Stockholm

New concepts and technologies are needed to upgrade conventional energy systems and cope with environmental challenges. However, while emerging new technologies may serve to improve energy efficiency at the local level, they might also have disruptive effects at the system level. This paper investigates the potentially disruptive impacts of upscaling local wastewater heat recovery at the building level on the performance of the wastewater treatment and district heating systems in Stockholm. A hybrid model based on data-driven and process-driven mathematical models was developed to simulate the performance of the wastewater system and interlinkages among different actors. Two types of technologies (heat exchanger and heat pump) and different technology penetration scenarios (10%, 20%, and 40%) are considered for heat recovery in buildings. If 20% of the buildings install heat exchangers, the amount of heat demand in buildings decreases by 3% and total heat losses in the sewerage network decreases by 2%. In the case of local heat recovery using heat pumps in 20% of the buildings, there is a 4% reduction in the heat demand in buildings and 3% decrease in total heat losses in the network. Meanwhile, the heat demand in the wastewater treatment plant increases by 2% (with heat exchangers) or 4% (with heat pumps). Moreover, the district heating company recovers 5% and 9% less heat from the wastewater treatment plant, respectively, as compared to current conditions. These findings indicate that enhanced heat recovery in buildings could have disruptive impacts on currently centralized energy and water service provision over time. This justifies closer consideration of the balance between local and system-level solutions as policymakers define goals for energy efficiency, and evaluate potential societal and economic implications of different alternatives.

Climate Change and Building Energy Consumption: A Review of the Impact of Weather Parameters Influenced by Climate Change on Household Heating and Cooling Demands of Buildings

The growth of urban population as the result of economic and industrial development has changed our place of living from a prosperous place to where the resources are carelessly consumed. On the other hand, long-term climate change, i.e. global warming, has had adverse impact on our resources. Certain resources are on the verge of depletion as the consequence of climate change and inconsiderate consumption of resources, unless serious measures are implemented immediately. The building sector, whose share in the municipal energy consumption is considerably high, is a key player that may successfully solve the problem. This paper aims to study the effects of climate change on the energy consumption of buildings and analyze its magnitude to increase the awareness of how construction can reduce the overall global energy consumption. A descriptive-analytical method has been applied to analyze valid models of energy consumption according to different scenarios and to interpret the conditions underlying current and future energy consumption of buildings. The results clearly show that the energy consumption in the building sector increasingly depends on the cooling demand. With that being said, we can expect the reduction of overall energy consumption of buildings in regions with high heating demands, whereas rising the energy consumption in buildings is expected in regions with high cooling demand. To conclude, the long-term climate change (e.g. global warming) underlies the increased energy consumption for the cooling demand whose share in total energy consumption of buildings much outweighs the heating demand. Therefore, to conserve our resources, urban energy planning and management should focus on working up a proper framework of guidelines on how to mitigate the cooling loads in the energy consumption patterns of buildings.