Individual Heat Pumps Research Articles

Changes in hourly electricity consumption profiles and price elasticities in Denmark 2019–2022

Changes in consumption profiles affect the need for investments in production and grid capacities. Extending a model with categorical variables for hours of the day, months and types of days to include short-term electricity prices, and applying Danish data for the hourly electricity consumption by aggregated categories of customers, consumption profiles for each of the years from 2019 to 2022 are estimated and it is tested if the profiles change significantly. Further, the short-term price elasticity of hourly electricity demand is estimated. During the first COVID-19 lockdown, residential electricity consumption increased and non-residential consumption decreased and the residential consumption profile on weekdays resembles the weekend profile. However, long-term effects are quite limited. For 2022, the residential consumption profile is significantly different from the profile in 2019. The profile has become flatter, increasing consumption during the night and reducing consumption during the daytime. An increasing number of electric vehicles and individual heat pumps contribute to this change. The short-term price elasticity for total electricity consumption increased in 2022. Especially, the price elasticity for residential customers increased and became significant in the second half of 2022 where electricity prices were high and volatile and customers were aware of prices.

Modeling and contribution of flexible heating systems for transmission grid congestion management

The large-scale integration of flexible heating systems in the European electricity market leads to a substantial increase of transportation requirements and consecutively grid congestions in the continental transmission grid. Novel model formulations for the grid-aware operation of both individual small-scale heat pumps and large-scale power-to-heat (PtH) units located in district heating networks are presented. The functionality of the models and the contribution of flexible heating systems for transmission grid congestion management is evaluated by running simulations for the target year 2035 for the German transmission grid. The findings show a decrease in annual conventional redispatch volumes and renewable energy sources (RES) curtailment resulting in cost savings of approximately 5% through the integration of flexible heating systems in the grid congestion management scheme. The analysis suggests that especially large-scale PtH units in combination with thermal energy storages can contribute significantly to the alleviation of grid congestion and foster RES integration.

Accelerating renewable heat: Overcoming barriers to shared-loop ground source heat pump systems in the United Kingdom

Heat decarbonisation is needed rapidly and at scale to reach net-zero carbon emissions by 2050. Shared-loop ground source heat pumps (GSHPs) are an under-researched technology with potential to deliver clean heat at scale. These involve the installation of connected GSHPs for a group of homes, a whole street or apartment building, with shared use of deep boreholes, coupled with individual heat pumps installed in each property. However, a range of socioeconomic, political and technical barriers inhibit their mass deployment and there is a research gap surrounding potential policy, governance and financial support mechanisms to help overcome these. This study investigates the advantages and challenges associated with this technology, and reviews measures which could accelerate uptake. Analysis draws on 58 interviews with policymakers, industry stakeholders, users and non-users in the UK. Advantages include neighbourhood scale-deployment, with the potential to decommission local gas grids. Compared with air-source heat pumps, shared-loop GSHPs are more compact, less noisy, and more efficient, with lower running costs. However, they share many barriers associated with all heat pumps, and have higher up-front costs. A range of policy options are discussed which address the need for investor confidence, skills and training, information provision, and other incentives. Overall, carefully designed policy and financial support mechanisms could accelerate mass deployment of shared-loop GSHP technology, helping to reduce reliance on fossil fuels, boost energy security and reduce carbon emissions.

On the design of 5GDHC substation control systems

ABSTRACT This paper presents challenges in the control of 5GDHC networks and proposes an approach for the robust control design of these networks. Temperatures are low and temperature differences are small in 5GDHC networks, in order to minimise heat losses in the distribution network and directly utilise low-temperature heat sources. Therefore, the robust control design of substations is crucial for stable and efficient operation of 5GDHC networks. We proposed the key steps to obtain a consistent control design that can be verified and tested prior to commissioning of the building substations and network. The design approach was elaborated in a case study in an existing neighbourhood in Haarlem, the Netherlands, constructed in the 1930s to 1970s. This neighbourhood will become independent of natural gas using PVT-rooftop panels, individual heat pumps (HP), a 2-pipe, bi-directional energy flow network operating at ultra-low temperatures and ATES system as a seasonal and daily storage facility.

Impact of locational pricing on the roll out of heat pumps in the UK

This paper investigates the impact of locational pricing on the roll out of heat pumps in the UK. Qualitative assessment of proposals set out for electricity market reform in the UK identified locational pricing as potentially having an impact on heat pump running costs. Energy system modelling was used to assess the economics of both individual heat pumps and system-wide heat pump roll out under both unified pricing and locational pricing for the UK for 2020 and 2035. PyPSA-GB, a future power system model, was employed to simulate unified and locational wholesale prices and the Octopus Agile tariff was used to calculate indicative retail tariffs applicable to domestic heat pumps. The research highlights that locational pricing can create market conditions which better reflect the true cost of generating and delivering electricity, however, it can also lead to higher heat pump operating costs in regions with projected high heat demand. Key findings reveal that locational pricing could result in significant geographical disparities in heat pump operating costs due to varying electricity prices across different zones. Further work is required to develop policy to alleviate high operating costs and to promote flexible operation of heat pumps.

Communal or individual – Exploring cost-efficient heating of new city-level housing in a systems perspective

As cities expand, new buildings are constructed and they require heating. With increasing integration of the heating and electricity sectors and forecasts of rapid growth in electricity demand, heating choices become critical for the sustainability transition. The main heating options are communal or individual, where the communal option is represented by district heating (DH) and the individual option mainly by heat pumps or biomass heating. Which option is best from the cost perspective depends on the building type and on the energy system development. Thus, this paper investigates cost-efficient heating of new city-level housing in a systems perspective under various scenarios.The investigation was carried out using an energy systems optimization model based on a case representing Swedish conditions. A dynamic approach was used to investigate cost-efficient development of the supply side and demand side simultaneously.The results indicate that the most cost-efficient heating systems are: DH for apartment buildings; and individual heating options for single-family housing with low heat demands. For large single-family housing with high heat demands, the cost-efficient solution depends on the heat demand profile. Higher heat use during winter favors DH and individual biomass boilers, but diminishes the economic feasibility of individual heat pumps.

Probabilistic Flexoffers in residential heat pumps considering uncertain weather forecast

The penetration of renewable energies is increasing in energy systems worldwide. Consequently, the intermittency of the energy sources raises technical challenges for sustainable energy supply. Demand-side flexibility is an effective solution to counterbalance renewable power fluctuations. In the residential sector, electrical heat pumps exhibit great flexibility potential. In this paper, a novel approach is proposed to generate FlexOffers for individual heat pumps considering the uncertain nature of weather conditions. To achieve the aim, firstly, the thermal dynamic model of residential buildings is presented mathematically. The model addresses different temperature zones. The constant coefficients of the thermal dynamics are estimated using Continuous-Time Stochastic Model (CTSM) in R software. Afterward, the building model is integrated with a success function to generate FlexOffers. The success function is comprised of two objective functions including minimization and maximization of the energy consumption of heat pumps. The FlexOffers are generated considering the existing gap between the minimum and maximum energy consumption. The patterns of energy consumption are defined based on occupants’ thermal comfort temperature setpoint. The FlexOffers are programmed in UPPAAL-STRATEGO software. Finally, a high-fidelity building model with four rooms is used to examine the proficiency of the suggested approaches. The simulation results confirm that the proposed method generates flexibility potentials for the upstream network in both optimistic and pessimistic states of energy consumption patterns.

Accurate metering and billing of ambient loop systems

• Accurate billing of ambient loop systems requires complex metering and billing strategy. • Tenants exchanging energy via an ambient loop offers potential energy savings. • Transparency of energy usage gives tenants control to reduce energy consumption. In order to reduce the operational energy consumption in the heating and cooling of buildings, the building industry is exploring methods of combining district heating and cooling networks where tenants’ premises are equipped with individual water source heat pumps. This has the potential to create an ambient loop where tenants can exchange heat with each other, and a main source of heating or cooling can top up the energy demand of the loop. A challenge that arises in such a system is how the landlord can accurately bill tenants when energy is shared between tenants via the landlord's services loop. This study takes a theoretical approach on one potential solution where the billing model is developed to use data from energy meters and electricity meters, analyze the operational modes of the components in the system and proportion the energy usage accordingly.

The Balance between Energy Efficiency and Renewable Energy for District Renovations in Denmark

Emissions can be reduced by increasing the energy efficiency of buildings and supply systems or increasing the share of renewable energy in the energy system. Denmark has a long tradition for district heating and today it supplies more than 65% of dwellings, which indicates that a major part of the transition from fossil fuels to renewables can be achieved at the supply system level rather than on the individual building level. This paper presents calculations performed on a generic Danish district undergoing major renovation. The generic district is based on an existing district in Aalborg and consists of 1019 dwellings spread over three different building typologies. The purpose of the investigation was to determine which combination of energy saving measures would achieve the optimal level of energy efficiency. Calculations were made with average data for district heating in Denmark, district heating based on natural gas, and district heating from renewable energy sources, such as solar heating, biofuels, and heat pumps, respectively. The calculations include costs for investment, maintenance, and operating as a function of the primary energy needs. Global warming potential (GWP) was calculated and included CO2 emissions from space heating, domestic hot water, and electricity for operation and household. The calculations show that for the generic Danish district, which is already connected to a district heating network, the optimal solution is to add 200 mm insulation to roofs (in total 300 mm) and 150 mm insulation to walls (in total 200 mm) and replacing the existing windows with new three-layer low energy windows. Furthermore, the calculations show that in a future scenario with a significantly higher level of renewable energy in the energy system, a shift to individual heat pumps can reduce total emissions by up to 1.5 kg CO2 eq/m2 per year (20% reduction) at an additional cost of EUR 8.0/m2 per year (40% increase). The calculations described in this paper are part of a larger investigation carried out in IEA EBC Annex 75.

Towards Climate Neutral Buildings – Case Study of Positive Building in Brussels: Gare Maritime project

The Gare Maritime is a former freight station in Brussels that has been vacant for quite some time. The exceptional architectural features of the building have encouraged the owner to maintain and restore the building and create commercial and office spaces. To this end, the large hall is renovated into a well-insulated envelope in which the office volumes are placed independently. These spaces are climatised by using a geothermal loop with ATES to which individual heat pumps are connected: Cooling is provided in a passive way and heating is done through the heat pumps. A 3MW of PV-panels installations is on the existing roof structure. By means of the insulation package and an intelligent control system for openable parts of the building envelope, a comfortable indoor climate is created within the hall itself in which activities can take place for most of the year. The moderate temperature in the hall leads to a low energy consumption of the built-in volumes and losses to the outside environment are drastically limited. The ventilation is supplied in all spaces using a mechanical system. Inside the office-volumes, a perfect flexible climate is guaranteed by means of chilled ceilings, which also act as acoustic absorption material. Large window-openings maximize the benefit of daylight penetrating the building. By using variable frequency pumps, variable air volumes and daylight controlled light fixtures and sensors; the energy use of the building is minimized. Besides the 100% refurbishment of the existing structure, the design team developed a structural strategy of prefabricated, wooden constructions for the built-in office spaces, making it a perfect example of the reduction of the use of natural resources and maximizing the amount of absorbed CO2. To come to the overall strategy of this renovation, numerous simulations, brainstorms and gathering of references were conducted from the early-stages. The start design parameters of the project were determined through simulations before the elaboration of an architectural design. This process allowed the client to take decisions based on robust data relating to attainable comfort, investment costs and environmental considerations. Overall, the project is Energy Positive Building

Optimal Dispatch of Water Source Heat Pump Regional Energy Systems Based on Neighborhood Adaptive Particle Swarm Optimization

To achieve the global Carbon Neutral goal required by the Paris Agreement, considerable concerns are advanced regarding improving the efficacy of clean energy in recent years. Taking as the research object a ground‐source heat pump (GSHP), which is a recently developed, highly efficient, and energy‐saving air‐conditioning technology, herein, the optimization of operational strategies regarding GSHP systems from the perspective of its individual heat pump units is studied. To attain this aim, an optimal scheduling model of surface water source heat pump regional energy systems with energy storage devices is established and then solved by the neighborhood adaptive particle swarm optimization (NAPSO) algorithm proposed. A method is proposed to transform the mixed integer programming problem into a continuous optimization problem to address the energy storage device model difficulties with integer variables. The experimental results show that the NAPSO algorithm can save 8.65% in cooling conditions and 7.22% in heating conditions in terms of operating costs compared with the empirical operation method. In addition, it can save 11.13% and 9.66% of operating expenses on average compared with the five other intelligent optimization algorithms.

CASE ANALYSIS OF HEAT PUMP INTEGRATION IN DISTRICT HEATING SYSTEM

The installation of heat pumps in district heating (DH) systems is one of the most promising technologies to increase the efficiency of heat supply by using renewable energy sources and reducing heat carrier temperatures in the networks. The possibilities of installing heat pumps in DH systems are very wide, but most often the main purpose of their application is to increase the temperature of the supplied heat carrier at the heat substations of individual consumers or their groups. This paper describes a study that analyzed the possibilities of integrating an individual heat pump at a heat substation in a building to reduce the temperature of the heat carrier in the return line. The results of the study revealed the dependences of the reduction of the heat demand of the building from the DH network, the power of the heat pump, the coefficient of performance (COP), and the reduction of the return temperature.

Environmental Life Cycle Assessment scenarios for a district heating network. An Italian case study

District heating networks have present and future great potential in decarbonization and in general for improving the environmental profile of the European building sector. It is due to the integration of solar-thermal energy and other renewable sources, flexibility by thermal storage, and mainly the ability to recover industrial and municipal waste heat: providing benefits at the element (energy system) and city level. However, individual appliances, such as electric-driven heat pumps, are and will be an attractive option; the decarbonization process of the European electricity grid makes them very appealing from an environmental perspective (from an energy system viewpoint). In this paper, the authors investigate the environmental competitiveness of a district heating network to provide space heating and domestic hot water using the Life Cycle Assessment method. The evaluation was carried out for a new building area (approx. 26 500 m2 of net surface) located in Milan. The present and future (2030) environmental profiles of North Milan’s district heating network were assessed and compared with three individual electric-driven heat pumps (groundwater-source and 450 kW capacity each), as an alternative energy system. 16 potential impact categories were evaluated using, 1 kWh of thermal energy as a functional unit, ecoinvent as background database, and the Environmental Footprint 3.0 as impact assessment method. The results indicated that despite the higher CO2eq emissions compared to the heat pumps (208 vs 118 gCO2eq/kWhth), district heating could potentially have an almost equivalent climate change impact in the future, due to the integration of renewables sources, feasible with the 4th generation. The value of district heating and electric-driven heat pumps were 89 and 81 gCO2eq/kWhth, respectively for 2030. In contrast, the weighting results showed a better environmental profile for the district heating in both scenarios, allowing a reduction of 67% (in the present) and 19% (in the future).

Synergies between buildings retrofit and district heating. The role of DH in a decarbonized scenario for the city of Milano

The goal of this work is to present challenges and opportunities for the development of 4th generation district heating in future decarbonized scenarios for the Italian city of Milano. The work has been developed in the framework of a Climate-KIC project to support Milano municipality in developing decarbonization measures. The first part of the work consists in the evaluation of a geographical distribution of the civil sector heat demand according to a bottom-up approach based on open data. Thanks to this statistical tool, also buildings retrofit can be analysed. Three retrofit scenarios are simulated according to policy goals for 2030 and 2050, foreseeing a retrofit priority of worst energy performances buildings, resulting in 8.8TWh, for the first two scenarios, and 9.4TWh for the last one. The areas characterized by the majority of retrofit can be identified as the most suitable for low temperature district heating development. Renewables and low temperature waste heat sources are also assessed, resulting in 9.8TWh of available heat. The application of district heating in combination with the identified renewables is assessed in these scenarios with a clustering approach. The evaluation of potential diffusion of 4GDH is based on the comparison between the overall cost of district heating and the competing individual systems costs: district heating is considered feasible only in retrofitted buildings where district heating cost is lower than individual systems cost (about 0.7TWh in each scenarios). The retrofitting scenarios combined with the diffusion of renewable based 4GDH are assessed also in terms of environmental impact. The current greenhouse gas emissions related to the actual heating systems, evaluated through the Thermal Systems Regional Cadastre database, is compared to the district heating development scenarios and to individual heat pump system scenarios. The results show the highest reduction of emission in the district heating scenarios (65%).

Performance characteristics of a cascade multi-functional heat pump in the winter season

Cascade multi-functional heat pumps are becoming popular due to their ability to simultaneously provide cooling, heating, and hot water. In this study, the performance characteristics of a water-to-water cascade multi-functional heat pump designed to provide heating, hot water, and simultaneous heating and hot water during the winter season are analyzed according to variation in secondary fluid temperature. The simultaneous heating and hot water cycle was optimized to meet the design heating and hot water capacities by increasing the compressor speeds of the low stage and high stage cycles above those in the heating and hot water cycles. An increase in the outdoor heat exchanger entering water temperature increased the performance of the cascade multi-functional heat pump in all operating modes, while an increase in the indoor heat exchanger entering water temperature resulted in a decrease in the performance of the cascade multi-functional heat pump in all operating modes except the capacity of the hot water cycle in heating-hot water mode. Furthermore, an increase in the hot water entering water temperature resulted in a decrease in the performance of the cascade multi-functional heat pump. The cascade multi-functional heat pump in heating-hot water mode showed similar performance trends as individual heat pumps for space heating and hot water generation and provided much stable hot water capacity at varying outdoor entering water temperature conditions. Cascade multi-functional heat pumps have the potential to provide better energy efficiency at higher heating and hot water loads, and can, therefore, be used for simultaneous space heating and hot water generation in winter seasons.

Economic comparison of 4GDH and 5GDH systems – Using a case study

For decades the focus of district heating (DH) has been on energy efficiency and minimum operating temperatures. This quest for continuous efficiency improvements led to the modern 4th generation of DH (4GDH), operating at lowest possible temperature for direct utilization by end-user. In recent years the term 5th generation DH (5GDH) has become popular for individual heat pump systems sharing thermal sources via uninsulated pipe network. While 5GDH has similarity with 4GDH it is a technically different solution, as the heat generation is moved to the end-users. When discussing 4GDH and 5GDH the focus quickly revolves about the efficiency of the distribution grid, however the discussion should be on the overall system efficiency and the levelized cost of the heat (LCOH). This paper analyzes LCOH for a mixed building area consisting of a central heat source, high or low energy buildings connected to 4GDH, 5GDH or a 4GDH variant with end-user temperature boosting for domestic hot water purposes. The analysis considers two countries: DK and UK. The analysis further explores the impact of the heat source temperature, from 10 °C to 60 °C, on the LCOH. The results indicate that 4GDH is the more competitive heat supply solution for the considered case.

Mitigating heat demand peaks in buildings in a highly renewable European energy system

Space and water heating accounts for about 40% of final energy consumption in the European Union and thus plays a key role in reducing overall costs and greenhouse gas emissions. Many scenarios to reach net-zero emissions in buildings rely on electrification, but meeting the heat demand peaks in the winter can be challenging, particularly when wind and solar resources are low. This paper examines how to mitigate space heating demand peaks most cost-effectively in a top-down, sector-coupled model with carbon dioxide emissions constraint to be net-zero. It introduces the first model that co-optimises both supply and efficiency simultaneously including all European countries with hourly resolution. The competition between technologies to address these heating peaks, namely building retrofitting, thermal energy storage and individual hybrid heat pumps with backup gas boilers is examined. A novel thought experiment demonstrates that the level of building renovation is driven by the strong seasonal heat peaks, rather than the overall energy consumption. If all three instruments are applied, total costs are reduced by up to 17%. Building renovation enables the largest benefit with cost savings of up to 14% and allows individual gas boilers to be removed from the energy system without significant higher costs.

Potential and costs of decentralized heat pumps and thermal networks in Swiss residential areas

Globally, there has been an increasing trend toward electricity production from renewables, hence promoting the opportunity for the electrification of the residential heating sector as opposed to fossil fuels' combustion. Decentralized heat pumps and district heating networks could play a key role in the Swiss future approach to heating. This study provides a detailed enviro-economic assessment of the application of heat pumps and district heating systems based on renewable sources in different Swiss building archetypes on different scales. The results show that the levelized costs of heat from individual heat pumps and large-scale district heating networks (using industrial excess heat with a lower energy price than for the other energy carriers) are 7% to 20% and 65% to 75% higher than individual fossil fuel boilers for single-family houses, respectively. However, for multifamily houses, individual heat pumps, small thermal grids, and large-scale district heating networks are competitive. The district heating network coupled with a large centralized water source heat pump is found to be the most expensive solution (0.24-0.29 CHF/kWh) for residential heating today. The sensitivity analysis suggests the economic feasibility of different heating technologies significantly overlaps with each other depending on the boundary conditions, hence justifying not only the mixed opinions by experts in Switzerland but also the disagreements over costs of these technologies in international literature. It can be concluded that, based on the levelized cost of heat, there are sufficient economically viable options for decarbonization and electrification of the residential heating sector. While this is an important finding for policymakers, the barriers, for example, high upfront cost, need to be addressed. Highlights Low-carbon heating technologies are investigated for residential heating supply. Levelized costs of heat from heat pumps and district heating networks are computed. Levelized costs of the heating technologies significantly overlap with each other.

Heat consumption scenarios in the rural residential sector: the potential of heat pump-based demand-side management for sustainable heating

BackgroundPoor air quality and inadequate domestic heating sources are tightly connected problems in the Eastern-European countryside. There are a few alternatives to comprehensively solve these problems with an emphasis on economic and environmental sustainability. In this paper, individual heat pumps and energy efficiency measures are analyzed in four scenarios to investigate their role for cleaner and sufficient heating in rural settings. From a high-level perspective, this paper assesses the potential for electricity demand flexibility based on the use of individual heat pumps equipped with hot water storage.MethodsIn a first step, the current annual residential heating energy consumption of a rural area in Hungary is estimated with a bottom-up model using data from field surveys and official datasets. In a second step, four scenarios estimate the future heating energy consumption considering demographic trends and the average number of building retrofits (thermal insulation) performed yearly in the region.ResultsThe reference scenario is a 20-year projection of heating energy consumption with modest retrofit actions which resulted in small energy savings. Alternative scenarios based on more effective retrofit actions reaching higher rates of the building stock would result in a 23–69% reduction in final energy consumption. Phasing out lignite from the heating energy mix would reduce particulate matter emissions. Each well-insulated dwelling with a heat pump-based system and hot water storage tank could provide theoretical flexibility of approximately 3.4 kWh per 24 h.ConclusionsThe current energy retrofit practices are not sufficient to solve the challenges faced in this area. Demand-side management policies based on the widespread use of individual heat pumps are an alternative to promote access to cleaner residential heating. An additional benefit is the potential for flexibility in electricity demand. Thus, this paper calls for an integration of energy retrofit with efficient heating (including hot water storage tank) to achieve results that further contribute to a future of sustainable energy.

Double Loop Network for Combined Heating and Cooling in Low Heat Density Areas

This study investigated a double loop network operated with ultra-low supply/return temperatures of 45/25 °C as a novel solution for low heat-density areas in Denmark and compared the proposed concept with a typical tree network and with individual heat pumps to each end-users rather than district networks. It is a pump-driven system, where the separate circulation of supply and return flow increased the flexibility of the system to integrate and displace heating and cooling energy along the network. Despite the increased use of central and local water pumps to operate and control the system, the simulated overall pump energy consumption was 0.9% of the total energy consumption. This was also an advantage at the design stage as the larger pressure gradient, up to 570 Pa/m, allowed minimal pipe diameters. In addition, the authors proposed the installation of electrically heated vacuum-insulated micro tanks of 10 L on the primary side of each building substation as a supplementary heating solution to meet the comfort and hygiene requirements for domestic hot water (DHW). This, combined with supply water circulation in the loop network, served as a technical solution to remove the need for bypass valves during summer periods with no load in the network. The proposed double loop system reduced distribution heat losses from 19% to 12% of the total energy consumption and decreased average return temperatures from 33 °C to 23 °C compared to the tree network. While excess heat recovery can be limited due to hydraulic issues in tree networks, the study investigated the double loop concept for scenarios with heat source temperatures of 30 °C and 45 °C. The double loop network was cost-competitive when considering the required capital and operating costs. Furthermore, district networks outperformed individual heat pump solutions for low-heat density areas when waste heat was available locally. Finally, although few in Denmark envisage residential cooling as a priority, this study investigated the potential of embedding heating and cooling in the same infrastructure. It found that the return line could deliver cold water to the end-users and that the maximum cooling power was 1.4 kW to each end-user, which corresponded to 47% of the total peak heat demand used to dimension the double loop network.