Residential Heating Systems Research Articles

Analysis of energy savings for residential electrical and solar water heating systems

A solar water heating system is a device that takes energy from the sun radiation to raise the water temperature for use of water supply in the home. Water heating is the second-largest household electricity user. Replacing EWHs with a SWHs with an electrical backup can reduce electricity usage. An experimental setup and POLYSUN program were used for a simulation-based approach for evaluating the comparison between (SWHs) and (EWHs) for three different cities in the Kurdistan region of Iraq. The investigated setup consists of a flat plate solar water heating system with a total area of 2.01 m2 and a 200 L storage tank, and it suits a single-family house composed of four people. The numerical simulation results reveal that the use of SWHs decreases substantial energy consumption. For Duhok, Erbil, and Sulaymaniyah cities, the annual saved energy is 1365 kWh, 1383 kWh, and 1459 kWh, constituting a solar fraction of 39.4%, 40.4%, and 34.2% with an annual CO2 reduction of 771 kg, 781 kg, and 824 kg, respectively. The experimental work was also conducted in January 2021 in Erbil City, in the Kurdistan Region. A comparison of electricity consumption between SWHs and EWHs was demonstrated.

Residential heating systems’ selection process: empirical findings from Greece on the relations between motivation factors and socioeconomic, residence, and spatial characteristics

ABSTRACT The residential sector is responsible for a large portion of global energy consumption, with the primary needs consisting of space heating. Therefore, consumers’ decisions concerning the heating system selection play a significant role in shaping the sector's conditions. This study examines the relationship between residential heating systems’ selection-related motivation factors and socioeconomic, residence, and spatial characteristics. A questionnaire survey focusing on the Greek population was performed during 2012 and 2019, with the two samples being examined in parallel. The motivation factors were classified into convenience, market, performance, and cost-related aspects, with performance-related and cost-related aspects being perceived as the most important. Convenience-related aspects are more important for older people and women, while performance-related aspects for individuals with environmentally friendlier behaviour.

Variable-Load Heat Pumps: Impact of the Design and Control Parameters on the Actual Operation Conditions

Nowadays heat pumps (HPs) represent the main alternative to traditional heating systems for the transition to nearly zero-energy buildings. Though HPs are a well-known technology, the estimation of their actual energy performance is still under discussion. Indeed, the proper choice of the HP design parameters (e.g. size, rated supply temperature) and the adopted control strategy can assume a paramount role to cover the mismatch between declared and actual performance of the system. Objective of this work is to analyze this mutual dependence in an operating system to provide guidelines for the design of a residential heating system with a HP. Through a dynamic energy simulation tool, a variable-load air-to-water HP is used to cover the thermal demand of a residential building. The effect of the reciprocal influence of different design choices (e.g. rated heating capacity or design supply temperature) and control strategies (e.g. climatic regulation) is analyzed by simulating different scenarios. To complete the evaluation, the impact of a thermal energy storage is also assessed. The study allows to identify guidelines for the design of different system configurations and results seem to confirm the impact of the investigated parameters on the seasonal performance of the system.

Development of an HTR-Type nuclear and bifacial PV solar based integrated system to meet the needs of energy, food and fuel for sustainable indigenous cities

In this study, a unique integrated system is developed to produce multiple useful outputs, including energy, fuel, and food, for indigenous communities to achieve sustainable development and address some of the sustainability goals developed by the United Nations in this regard. The Nunavut Territory is identified with the highest food and energy insecurity across Canada for the present study. A pilot project is, in this regard, developed under a case study and thermodynamically analyzed for Iqaluit, Nunavut as an Indigenous City. The high-temperature reactor (HTR)-type pebble bed nuclear reactors are considered to be used with the copper chlorine Cu-Cl hydrogen production cycle, bifacial photovoltaic (PV) plant, gas and steam turbines, greenhouse, fish farm and residential heating systems, and multi-effect water desalination in the integrated multigenerational system. The proposed system primarily produces electricity, district heating, fresh water, domestic hot water, and hydrogen fuel. The simulations are carried out on the PVsyst and Aspen Plus. The renewable and nuclear energy systems, as well as other subsystems, are assessed via the engineering equation solver (EES) software package. The proposed integrated system has achieved a 62.64% overall energy efficiency and a 68.91% overall exergy efficiency at the average ambient conditions. Moreover, the present system is designed in different capacities for eleven indigenous communities in Nunavut Territory by considering the energy resources and local demand.

Feasibility of Cloud Based Smart Dual Fuel Switching System (SDFSS) of Hybrid Residential Space Heating Systems for Simultaneous Reduction of Energy Cost and Greenhouse Gas Emission

Through tests conducted at the Toronto and Region Conservation Authority’s (TRCA) Archetype Sustainable Houses, a hybrid residential space heating system with a supervisory controller was monitored and studied to evaluate its performance and effectiveness for the heating season. A high efficiency natural gas furnace (NGF) and an electric air source heat pump (ASHP) were coupled together to meet the space heating demand of the house. This integrated system is called the cloud based Smart Dual Fuel Switching System (SDFSS) that considers time-of-use (TOU) pricing, fuel cost, short-term weather forecast, and equipment efficiencies and capacities. This multi-variable decision-making process defines an optimal schedule for the hybrid system to run more cost effectively. This paper analyses two separate SDFSSs. According to these analyses, the SDFSS systems showed lower operating cost with respect to the furnace or the ASHP system alone with various carbon tax (CT) levels from $0 to $250/tonne of CT with an increment of $10/tonne of CT that were simulated, along with a significant GHG emission reduction relative to the conventional heating systems. Furthermore, with these technologies, Canada’s residential sector could potentially meet Canada’s Paris Agreement goals. The SDFSS technology is a is flexible, user friendly, ubiquitous technology for the smooth transition from today’s natural gas dominated space heating system to the future’s low carbon infrastructure powered by a heat pump and renewable energy.

When to replace products with which (circular) strategy? An optimization approach and lifespan indicator

A longer product use requires less resources, causing less environmental impacts. Even though this assumption may appear intuitive, it is not necessarily the case for all products. Consider a product that causes significant impacts during its service life and loses performance through wear and degradation. Its extended use may cause higher impacts overall than replacing it before it reaches its end-of-life with an evolved alternative. In this paper, we propose a method for finding the replacement time when impacts become minimal, i.e. the optimal environmental lifetime (OEL), taking into account non-linear dynamics of technological efficiency improvements and efficiency degradation during usage. Different replacement options, including lifetime extension strategies such as re-manufacturing, are considered. Based on this, we define an indicator to measure the environmental performance of an achieved lifetime in comparison to the optimum. This lifespan indicator ϕ measures the relative achievement of the maximum possible impact savings, when replacing the initial product at OEL. It accounts for unsustainable throughput of materials and waste of resources when deviating from it. To illustrate the application of the method and lifespan indicator, the OEL of residential heating systems are calculated. It reveals that gas boilers shall be replaced in short intervals with evolved gas boilers or – more effectively – with a heat pump. This case study nullifies the common hypothesis that “durability is per se environmentally beneficial”, requiring to evaluate OEL on a case by case basis.

Analysing Energy-Saving Behaviours in Italian Households

In the European context of moving to a low-carbon economy, knowledge regarding household decisions surrounding residential heating systems is crucial for policymakers in order to design effective policies both to reduce non-renewable energy consumption and to enhance energy efficiency in the residential sector. The choices made by households concerning decisions on how to heat their homes can significantly influence the related environmental impacts. This research examines two aspects of decision making with respect to heating system upgrades in Italian households using, for the first time, data from the 2013 Italian Households Energy Consumption survey: the choice of using renewable energies for space heating and decision to invest in energy efficient retrofits. Our findings show that household socio-economic characteristics and contextual factors are critical for good decision-making regarding heating system. We also find that previous cash retrofit investments and dwelling characteristics are important determining factors both for the choice of heating system based on renewable sources and for the subsequent decision regarding the adoption of energy efficient retrofit measures.

Performance evaluation of a seasonal residential space heating system based on thermochemical energy storage

Abstract Performance of a novel configuration of residential seasonal space heating system based on open thermochemical energy storage (TCES) is numerically investigated. The system comprises two open TCES reactors and a humidifier operating in a complete closed-loop or in partial recirculation to maintain a comfortable temperature in a detached room. A detailed three-dimensional model for flow and heat transfer in a detached room is coupled with a model of the reactive bed undergoing exothermic reaction. The thermal and breathing comfort requirements in the room are obtained simultaneously by operating the system on partially recirculated air. A comparative study of the closed-loop configuration with its open-loop counterpart for the detached room indicates a significant energy saving of 76.61% (92.90 W) for the former. A realistic case study is conducted by operating the system with 10% fresh air, subject to ambient conditions for a winter night in Pune, India. Numerical studies conducted for constant ambient conditions reveal improvement in the room’s heat distribution with increased airflow rate. Employment of two TCES reactors instead of one reactor enhances the Coefficient of Performance (COP) by a factor of 1.39. Adiabatic humidification in the humidifier eliminates its external heat requirement with the increase in the blower power input. Investigation of different locations for the exhaust vent is carried out for minimum heat loss to the surroundings. The system’s energy consumption reduces by 10.18% using a cross-flow air-to-air heat exchanger for pre-heating fresh air. An annual heating cost of 0.44 USD.kWh−1 is estimated for the system.

Incorporating consumer choice into an optimization model for the German heat sector: Effects on projected bioenergy use

The energy transition requires policy makers to adopt a holistic view that also considers non-economic factors when developing cleaner technology deployment schemes. In particular, a broad knowledge base is required to ensure an efficient energetic use of the limited biomass potential. Energy system optimization models are widely used to inform decision makers about energy transition strategies. The heterogeneity of consumers, especially in the heat sector, is rarely considered in these models and therefore these models lack of completion to contribute to this holistic approach. In this study, a literature review was conducted to find empirical data on consumer behavior regarding the adoption of residential heating systems. This data was integrated into an optimization model for the German heat sector, combining established methods for integrating consumer heterogeneity with a novel approach for calculating indirect costs representing behavioral factors. The incorporation of consumer choice leads to a broader distribution of market shares of different technologies in both a “business-as-usual” scenario and an “ambitious measures” scenario. In particular, the future role of log wood technologies in the private household sector may have been underestimated in previous studies and should be discussed, when designing policies. With this study, the knowledge base for decision makers was extended to discuss the future efficient use of biomass within the German heat sector.

Demand response strategies in residential buildings clusters to limit HVAC peak demand

Due to the increasing spread of residential heating systems electrically powered, buildings show a great potential in producing demand side management strategies addressing their thermal loads. Indeed, exploiting the intrinsic characteristics of the heating/cooling systems (i.e. the thermal inertia level), buildings could represent an interesting solution to reduce the electricity peak demand and to optimize the balance between demand and supply. The objective of this paper is to analyse the potential benefits that can be obtained if the electricity demand derived from the heating systems of a building cluster is managed with demand response strategies. A simulation-based analysis is presented in which a cluster of residential archetypal buildings are investigated. The buildings differ from each other for construction features and type of heating system (e.g. underfloor heating or with fan coil units). By supposing to be able to activate the energy flexibility of the single building with thermostatic load control, an optimized logic is implemented to produce programmatically an hourly electricity peak reduction. Results show how the involvement of buildings with different characteristics depends on the compromise that wants to be achieved in terms of minimization of both the rebound effects and the variation of the internal temperature setpoint.

Assessing the impact of filtration systems in indoor environments with effectiveness

Effectiveness is commonly used to evaluate the particle removal performance of residential filtration systems. Previous investigations have used various effectiveness metrics to assess system performance through modeling efforts. However, the model assumptions often lead to an overestimation of effectiveness. Further, none of the studies considered the impact of realistic residential heating, ventilation, and air conditioning (HVAC) system operation patterns. In this investigation, we evaluated the strength and limitations of various effectiveness metrics. We identified exposure reduction as the most appropriate metric for modeling analyses because it does not rely on any steady-state assumptions. A time-varying mass balance model that accounts for system operation parameters including runtimes and cycle on-times, and the impact of indoor emission sources is used to simulate the changes in indoor particulate matter smaller than 2.5 μm (PM2.5) concentration with and without system operation. The effectiveness results show that runtime has the biggest impact on exposure reduction. At a fixed runtime, short cycle on-times and the coincidence of system operation with emission events can further improve the removal performance of the system. Thus, the particle removal performance of a filtration system can be optimized by changing its operation pattern while still maintaining similar fan energy use.

Integration of Micro-Cogeneration Units and Electric Storages into a Micro-Scale Residential Solar District Heating System Operating with a Seasonal Thermal Storage

A micro-scale district heating network based on the operation of solar thermal collectors coupled to a long-term borehole thermal storage is modeled, simulated and investigated over a period of five years. The plant is devoted to covering the domestic hot water and space heating demands of a district composed of six typical residential buildings located in Naples (southern Italy). Three alternative natural gas-fueled back-up auxiliary systems (condensing boiler and two different technologies of micro-cogeneration) aiming at balancing the solar energy intermittency are investigated. The utilization of electric storages in combination with the cogeneration systems is also considered with the aim of improving the self-consumption of cogenerated electric energy; heat recovery from the distribution circuit is also evaluated to pre-heat the mains water for domestic hot water production. The performances of the proposed plant schemes are contrasted with those of a typical Italian decentralized heating plant (based on the utilization of natural gas-fueled non-condensing boilers). The comparison highlighted that the proposed configurations can decrease the primary energy consumption (up to 11.3%), the equivalent emissions of carbon dioxide (up to 11.3%), and the operation costs (up to 14.3%), together with an acceptable simple pay-back period (about 4.4 years).

Residential Natural Gas Demand Response Potential during Extreme Cold Events in Electricity-Gas Coupled Energy Systems

In regions where natural gas is used for both power generation and heating buildings, extreme cold weather events can place the electrical system under enormous stress and challenge the ability to meet residential heating and electric demands. Residential demand response has long been used in the power sector to curtail summer electric load, but these types of programs in general have not seen adoption in the natural gas sector during winter months. Natural gas demand response (NG-DR) has garnered interest given recent extreme cold weather events in the United States; however, the magnitude of savings and potential impacts—to occupants and energy markets—are not well understood. We present a case-study analysis of the technical potential for residential natural gas demand response in the northeast United States that utilizes diverse whole-building energy simulations and high-performance computing. Our results show that NG-DR applied to residential heating systems during extreme cold-weather conditions could reduce natural gas demand by 1–29% based on conservative and aggressive strategies, respectively. This indicates a potential to improve the resilience of gas and electric systems during stressful events, which we examine by estimating the impact on energy costs and electricity generation from natural gas. We also explore relationships between hourly indoor temperatures, demand response, and building envelope efficiency.

Conversion of Residential Heating Systems from Fossil Fuels to Biofuels: A Cross-Cultural Analysis

This paper aims to analyse: (a) how the attitude towards renewable energy-based heating systems, pro-environmental behaviour and the perceived attributes of technology influence intention to convert residential heating systems from fossil fuels to biofuels, and (b) the moderating role of culture based on Hofstede’s individualism dimension. A total of 425 responses were collected from a panel of internet users from representative countries in three continents (the United States, the United Kingdom and South Africa); the data analysis was carried out using structural equation models in a multigroup analysis. The results showed that attitude towards renewable energy-based heating systems is influenced by environmental variables in the United States and the United Kingdom, and by the perceived attributes of clean residential heating systems in the United States and South Africa. Attitude, in turn, impacts on the intention to convert from fossil fuels to biofuels. In addition, individualism has a moderating effect between these variables and there are intercultural differences in the degree of importance attributed to them. The study concludes the use of these energy systems as drivers of environmentally-sustainable development.

Demand Side Management of a pool of air source heat pumps for space heating and domestic hot water production in a residential district

The ongoing electrification of the heating sector will severely affect the patterns of power consumption in electrical distribution systems. Coupling electric heat pumps to thermal energy storage systems allows to increase the flexibility in their operation, thus minimizing the side effects on the electrical grid. This paper investigates the potential of an optimization algorithm that coordinates the operation of a pool of heat pumps in a residential district with the aim of reducing the power peak at grid level. In the simulated scenarios, the heat pumps are coupled to heat storage tanks for space heating and domestic hot water production. The simulations show that the proposed Demand Side Management strategy allows reducing daily peaks up to 21% when only space heating is considered, and up to a 35% when domestic hot water tanks are included in the optimization. The article discusses the effects of different factors, such as weather conditions and user behavior, as well as the uncertainty inherent to the predictions of domestic hot water and electrical consumption. In conclusion, the paper shows that a centralized management of the heat pumps can significantly contribute to reducing the issues linked to the extensive electrification of residential heating systems.

Automated modelling of residential buildings and heating systems based on smart grid monitoring data

More than 60% of the energy is consumed in European households for space heating. Combined with the currently low renovation rate, the realization of the 2000 W society will be challenging. A fast and remote detection of optimal retrofitting targets may help to address this problem. In this contribution, a novel procedure to characterise a building and its heating systems from smart grid monitoring data is presented. The parameters of a simplified physical simulation model for the building and heating system are adjusted to match the simulated and the actual power consumption of the heat pump. The method is validated on three reference buildings with almost perfect reproduction of the heat consumption over the course of one year and good recovery of relevant building/heating system parameters. The application on five real-world buildings shows the possibility to reproduce the annual heat consumption within a maximal deviation of 5% in four out of five cases. These convincing results enable also the application of the developed procedure as a load prediction tool.

Enabling a just transition: A composite indicator for assessing home-heating energy-poverty risk and the impact of environmental policy measures

Home-heating energy-poverty risk presents both challenge and opportunity for policymakers, businesses and communities. Effective measurement and management of this risk requires an evidence base that accounts for characteristics of the householder, building, and heating system. A composite index utilising 10 indicators refined to Small Area level is created to deliver spatially refined analysis of home-heating energy-poverty risk. The index is used to assess home-heating energy-poverty risk across 18,641 Small Area clusters in Ireland. This risk index is a scalable and internationally transferrable methodology that can be extended to cover other energy uses. Importantly the index is also dynamic and offers the capacity to analyse changes in energy-poverty risk associated with specific policy intervention proposals, including major contemporary environmental policy transitions such as residential fabric retrofit, residential heating system changes, energy price changes and carbon taxation. The application of the index to the Irish case affords refined insight into the impact and incidence of various market, technology and policy driven interventions such as fuel price changes, retrofit strategies and carbon tax increases. Risk and impacts vary geographically, and this index is designed to inform targeted policy interventions to mitigate home heating energy-poverty risk and thereby support ambitions for a ‘just transition’.

Numerical thermal performance investigation of a latent heat storage prototype toward effective use in residential heating systems

Latent heat thermal energy storage has been receiving increasing interests in residential heating applications. In this paper, a numerical heat transfer model was built with finite element method for a cylindrically encapsulated latent heat storage prototype and used for investigating its thermal performance optimization measures. The model was validated against four sets of experimental results for both charge and discharge, as the difference in accumulated storage capacity between simulation and experiment is less than 4%. Transient storage inlet boundary conditions were set in simulation for discharge considering the thermal output from the coupled radiators. The results of the optimization analyses show that: 1) reducing the capsule diameter from 69 mm to 15 mm shortens the completion time of charge and discharge by up to 70%, however, at the expense of 23% decrease in total storage capacity; 2) using parabolic or linear time-increasing heat transfer fluid flowrate profiles than a time-constant one extends around twofold the useful discharge timespan; 3) increasing the storage vessel diameter from 0.6 m to 0.7 m and to 0.8 m prolongs the useful discharge timespan from 2 hrs to the recommended 3 hrs, though the further enlargement to 0.8 m results in a lower state of charge after 3 hrs due to increase in unexploited storage capacity. From the numerical optimization study, we proposed a storage design adjustment of using 15 mm-diameter phase change material capsules in a 0.7 m-diameter cylindrical storage vessel, coupled with a parabolic flow strategy, to improve the storage on-peak discharging performance.

Optimal operation of residential heating systems with logwood boiler, buffer storage and solar thermal collector

Modern central heating systems with logwood boilers are comprised of the boiler, a buffer storage and solar thermal collectors. Conventional control strategies for these heating systems do not coordinate the utilization of all components. This can lead to a sub-optimal operation of the entire heating system resulting in a loss of efficiency and increased pollutant emissions. This contribution presents a control strategy which considers all components of the heating system including the user and forecasts for the solar yield and heat demand. It determines and carries out an optimal operating strategy that improves the user utility and maximizes the heating system efficiency while also ensuring a clean and efficient combustion. The control strategy continuously learns the user behavior and instructs the user when to refill the logwood boiler and how much fuel to use. The new control strategy was verified through test runs performed at an experimental setup consisting of a commercially available logwood boiler with a nominal capacity of 28kW, two buffer storages with a capacity of 1.5m3 each and a heating device with a thermal output of up to 12kW simulating a solar thermal collector. During these test runs, the CO emissions were reduced by 93.6% in the main combustion phase, 7.1% more solar yield was utilized, the buffer losses were reduced by −16.9% and the overall efficiency was increased by 3.1%. Thus, the application of this control strategy resulted in a significantly improved user utility and heating system efficiency.

Performance analysis of a residential heating system using borehole heat exchanger coupled with solar assisted PV/T heat pump

Abstract Borehole heat exchanger (BHE) is a promising method for extracting heat from the deep geothermal energy which has been widely used for residential heating in high latitude areas. The solar assisted photovoltaic/thermal (PV/T) heat pump could convert solar energy into useful heat efficiently, and could be further used to heat water from the BHE to a higher temperature level. In this paper, a residential heating system using BHE coupled with solar assisted PV/T heat pump is therefore proposed with further performance analysis. The simulation results show that a larger mass flow rate could increase the BHE's heat extract capacity but also increase the flow resistance and pump power under nominal conditions. The circulating water would not extract heat from rock-soil if the inlet temperature exceeds 48.5 °C when mass flow rate is 12 kg/s. Furthermore, the maximum water temperature from this hybrid system could reach 40.8 °C while the solar fraction is 67.5% when the area of PV/T module is 1000 m2, solar irradiation is 600 W/m2 and depth of the BHE is 2500 m. In the meantime, the heating COP of this hybrid system could reach 7.4 and the system could operate independently without power input from electrical grid.