Decarbonisation Of Heat Research Articles

District Heating of Buildings by Renewable Energy Using Thermochemical Heat Transmission

The decarbonisation of building heating in urban areas can be achieved by heat pumps connected to district heating networks. These could be ‘third-generation’ (85/75 °C), ‘fourth-generation’ (50/40 or 50/25 °C) or ‘fifth-generation’ (near ambient) water loops. Networks using thermochemical reactions should require smaller pipe diameters than water systems and be more economic. This work investigates thermochemical transmission systems based on liquid–gas absorption intended for application in urban district heating networks where the main heat source might be a MW scale heat pump. Previous studies of absorption for heat transmission have concentrated on long distance (e.g., 50 km) transmission of heat or cold utilizing waste heat from power stations or similar but these are not directly applicable to our application which has not been investigated before. Absorbent-refrigerant pairs are modelled using water, methanol and acetone as absorbates. Thermodynamic properties are obtained from the literature and modelling carried out using thermodynamic analysis very similar to that employed for absorption heat pumps or chillers. The pairs with the best performance (efficiency and power density) both for ambient loop (fifth-generation) and high temperature (fourth-generation) networks use water pairs. The next best pairs use methanol as a refrigerant. Methanol has the advantage of being usable at ambient temperatures below 0 °C. Of the water-based pairs, water–NaOH is good for ambient temperature loops, reducing pipe size by 75%. Specifically, in an ambient loop, heat losses are typically less than 5% and the heat transferred per volume of pumped fluid can be 30 times that of a pumped water network with 10 K temperature change. For high temperature networks the heat losses can reach 30% and the power density is 4 times that of water. The limitation with water–NaOH is the low evaporating temperature when ambient air is the heat source. Other water pairs perform better but use lithium compounds which are prohibitively expensive. For high temperature networks, a few water- and methanol-based pairs may be used, but their performance is lower and may be unattractive.

Performance analysis for the UK's first 5th generation heat network – The BEN case study at LSBU

The decarbonisation of heat requires a transition from gas boilers to low-carbon heating systems such as heat pumps. Efficiency gains can be achieved by linking heating systems through ambient loops called Fifth Generation District Heating and Cooling (5GDHC) networks. The UK needs working demonstrators to understand both the technical and practical challenges in the heat transition. The Balanced Energy Network (BEN) links two buildings on LSBU's campus and is the UK's first 5GDHC system at scale and among the first in the world to be retrofit in parallel to an incumbent gas system and include an active demand side response control system to toggle between energy vectors in way that minimises cost and carbon emissions. This paper presents performance data from its first year of operation in baseline mode, as it was commissioned and optimised. High temperature heat pumps were retrofit to an existing gas boiler circuit and match the 79 °C output temperature of the gas boiler system. No fabric upgrades were required and no pipes, ducts or heat emitters were resized, however the system maintained performance to reduce overall building carbon emissions by 13% and gas use by 40% across both buildings compared to the pervious heating season while the system was in use.

Evaluation of Heat Decarbonization Strategies and Their Impact on the Irish Gas Network

Decarbonization of the heating sector is essential to meet the ambitious goals of the Paris Climate Agreement for 2050. However, poorly insulated buildings and industrial processes with high and intermittent heating demand will still require traditional boilers that burn fuel to avoid excessive burden on electrical networks. Therefore, it is important to assess the impact of residential, commercial, and industrial heat decarbonization strategies on the distribution and transmission gas networks. Using building energy models in EnergyPlus, the progressive decarbonization of gas-fueled heating was investigated by increasing insulation in buildings and increasing the efficiency of gas boilers. Industrial heat decarbonization was evaluated through a progressive move to lower-carbon fuel sources using MATLAB. The results indicated a maximum decrease of 19.9% in natural gas utilization due to the buildings’ thermal retrofits. This, coupled with a move toward the electrification of heat, will reduce volumes of gas being transported through the distribution gas network. However, the decarbonization of the industrial heat demand with hydrogen could result in up to a 380% increase in volumetric flow rate through the transmission network. A comparison between the decarbonization of domestic heating through gas and electrical heating is also carried out. The results indicated that gas networks can continue to play an essential role in the decarbonized energy systems of the future.

Energetic and economic analysis of decoupled strategy for heating and cooling production with CO2 booster heat pumps for ultra-low temperature district network

The ultra-low temperature district heating and cooling (ULTDHC) systems are among the most interesting solutions for the decarbonisation of heating and cooling sectors. It is a technology where different optimised integrations and operations are still under development. The booster heat pumps (BHPs) or substations associated with this new generation take on a more critical role because the energy supplied by the main network is not enough for covering the user's requirements. Reviewing the literature, it has been seen necessary to make a short and long-term energetic and economic analysis of BHPs operation (considering heating, cooling and SHW requirements) under variable ULTDHC conditions. On this line, this work focuses on the analysis of the operation of two of the most promising BHP types: one with a single CO2 heat pump, type 1, and the other with two CO2 heat pumps with a decoupled operation, type 2. Both BHPs are connected to an ultra-low temperature District Heating and Cooling network with variable parameters throughout the year. The simulation is carried out in a representative building located in Toledo (Spain), in an area with considerable heating and cooling demands throughout the year. The objectives of the work are the following: analyse the daily and annual operations of the two BHPs types, study the effect of outdoor temperature on their optimal operation, point out their main parameter influence and variation and make an economic evaluation of these systems. The BHP type 2 investment is 8.3% more expensive than type 1 but the economic analysis shows an annual saving in heating and cooling operation of the building of 7.7% for BHP type 2 regarding type 1. The size of the BHP, total demand and buildings supplied affects the profitability of the BHP type. For this analysis, type 2 shows more profitable than type 1 when the annual heating demand is greater than a certain threshold.

The implications of ambitious decarbonisation of heat and road transport for Britain’s net zero carbon energy systems

Decarbonisation of heating and road transport are regarded as necessary but very challenging steps on the pathway to net zero carbon emissions. Assessing the most efficient routes to decarbonise these sectors requires an integrated view of energy and road transport systems. Here we describe how a national gas and electricity transmission network model was extended to represent multiple local energy systems and coupled with a national energy demand and road transport model. The integrated models were applied to assess a range of technologies and policies for heating and transport where the UK’s 2050 net zero carbon emissions target is met. Overall, annual primary energy use is projected to reduce by between 25% and 50% by 2050 compared to 2015, due to ambitious efficiency improvements within homes and vehicles. However, both annual and peak electricity demands in 2050 are more than double compared with 2015. Managed electric vehicle charging could save 14TWh/year in gas-fired power generation at peak times, and associated emissions, whilst vehicle-to-grid services could provide 10GW of electricity supply during peak hours. Together, managed vehicle charging, and vehicle-to-grid supplies could result in a 16% reduction in total annual energy costs. The provision of fast public charging facilities could reduce peak electricity demand by 17GW and save an estimated £650 million annually. Although using hydrogen for heating and transport spreads the hydrogen network costs between homeowners and motorists, it is still estimated to be more costly overall compared to an all-electric scenario. Bio-energy electricity generation plants with carbon capture and storage are required to drive overall energy system emissions to net zero, utilisation of which is lowest when heating is electrified, and road transport consists of a mix of electric and hydrogen fuel-cell vehicles. The analysis demonstrates the need for an integrated systems approach to energy and transport policies and for coordination between national and local governments.

PROSPECTS FOR DECARBONIZATION OF DISTRICT HEATING IN UKRAINE

The purpose of the work is to determine promising areas for decarbonization of district heating in Ukraine, as well as measures necessary for their practical implementation. State of the development of bioenergy in the world and in the EU is presented, and considerable contribution of bioenergy to the production of renewable heat is emphasized. In Ukraine, the existing problems of long-term planning at the state and regional levels in the heat supply sector need to be addressed. Recommendations for solving these problems have been developed. One of them is the elaboration of the Heat Supply Strategy until 2035, built on the principle of the Energy Strategy of Ukraine, as well as the Action Plan for its implementation. It is recommended to introduce the term “efficient district heating” in the legislation of Ukraine, which corresponds to Directive 2012/27/EU on energy efficiency, and to declare the purpose of increasing the share of such systems in district heating. The role of bioenergy in the process of decarbonization of district heating of Ukraine is analyzed. It is shown that one of the ways that can significantly improve the situation in heat supply is the wide involvement of biomass and solid biofuels in this sector. For the effective implementation of this task it is necessary to launch an electronic trade system for solid biofuels (biofuel exchange), introduce competition in district heating systems, as well as perform a set of additional actions and measures. This will allow not only to stabilize the situation with heat supply in Ukraine, but also to reduce the heat tariff for end users by 15-20%.

Modelica-based simulations of decentralised substations to support decarbonisation of district heating and cooling

District heating and cooling are considered effective solutions to decarbonise the energy use in the building sector. The latest generation of district heating and cooling also increases the potential of integrating heat pumps and chillers in each building substation. The benefits of such integration are the reduction of network temperature and distribution losses; the recovery of waste heat through a bidirectional network; and the decentralised production of heating and cooling. Sizing the network depends mainly on the heat flows between connected buildings. The substation performance and technical installations determine these heat flows. We present in this paper Modelica-based simulations of two design cases for substations. The first design case involves installed heat pump, chiller, and circulation pumps. Alternatively, the second design enables the heat pump to provide direct cooling through a heat exchanger. The models for these installations were developed using the Modelica language to perform continuous-time simulations. The performance in each design case was evaluated in terms of seasonal coefficient of performance and total electric energy use. An analysis on a cluster of 11 buildings suggests that the addition of the direct cooling heat exchanger can save up to 10% of the total annual electric energy use. Additional savings can be achieved by optimising the building supply temperatures and the district network temperature.

A Review of the Performance of Minewater Heating and Cooling Systems

As the decarbonisation of heating and cooling becomes a matter of critical importance, it has been shown that flooded mines can provide a reliable source of low-carbon thermal energy production and storage when coupled with appropriate demand via an appropriate heat transfer technology. This paper summarises the potential resource represented by a long legacy of mining operations, the means heat can be extracted from (or rejected to) flooded mine workings, and then considers the risks and challenges faced by minewater geothermal energy (MWG) schemes in the planning, construction, and operational phases. A combination of site visits, interviews and literature reviews has informed concise, updated accounts for many of the minewater geothermal energy systems installed across the world, including accounts of hitherto unpublished systems. The paper has found that a number of previously reported MWG schemes are now non-operational. Key risks encountered by MWG schemes (which in some cases have led to decommissioning) include clogging of system components with mineral precipitates (e.g., ochre), uncertainty in targeting open mine voids and their hydraulic behaviour, uncertainty regarding longevity of access to minewater resource, and accumulated ongoing monitoring and maintenance burdens.

Weather-induced variability of country-scale space heating demand under different refurbishment scenarios for residential buildings

The decarbonisation of residential heat through integration with the power system and deployment of refurbishment policies is at the core of European energy policies. Yet, heat-electricity integration may be challenged, in practice, by the large variability of heat demand across weather years. Current approaches for residential heat demand simulation fail to provide insights about the extent of such variability across many weather years and about the benefits potentially brought about by nearly zero-energy buildings. To fill this gap, this work develops an open-source space-heating demand simulation workflow that is applicable to any country's building stock. The workflow, based on a well-established lumped-parameter thermodynamic model, allows capturing sub-national weather-year variability and the mitigation effects of refurbishment. For Italy, different weather years lead to variations in heat demand up to 2 TWh/day, lasting for several days. Moreover, some weather regimes produce spatial asymmetries that may further complicate heat-electricity integration. The refurbishment of about 55% of buildings constructed before 1975 could substantially mitigate such oscillations, leading to a 31–37% reduction of yearly heat demand, primarily in colder regions. Intra-day heat demand variations, driven by user behaviour, are not substantially impacted by refurbishment, calling for the simultaneous deployment of flexible heat generating technologies.

Thermal energy transfer around buried pipe infrastructure

Decarbonisation of heating is essential to meet national and international greenhouse gas emissions targets. This will require adoption of a range of solutions including ground source heat pump and district heating technologies. A novel route to these solutions includes dual use of buried infrastructure for heat transfer and storage in addition to its primary function. Water supply and wastewater collection pipes may be well suited for thermal energy applications being present in all urban areas in networks already in proximity to heat users. However, greater understanding of their potential interactions with surrounding heat sources and sinks is required before full assessment of the energy potential of such buried pipe networks can be obtained. This paper presents an investigation into the thermal interactions associated with shallow, buried water filled pipes. Using the results of large scale experiments and numerical simulation it is shown that soil surface ambient conditions and adjacent pipes can both act as sources or sinks of heat. While conduction is the main mechanism of heat transfer in the soil directly surrounding any pipe, any adjacent water filled pipes may lead to convection becoming important locally. In the test case, the thermal sphere of influence of the water filled pipe was also shown to be large, at in excess of 4 m over a timescale of 4 months. Taken together, these points suggest that design and analysis approaches when using water supply and wastewater collection networks for heat exchange and storage need careful consideration of environmental interactions, heat losses and gains to adjacent pipes or other infrastructure, and in ground conditions for a number of pipe diameters from any buried pipe.

Techno-economic comparison of technology options for deep decarbonization and electrification of residential heating.

This study aims to provide detailed information on the key technologies that utilize renewables for decarbonization and electrification of the residential heating sector. To contextualize and compare the economics of the technologies, a levelized cost model is employed to perform a comparative analysis for a dense urban area in Switzerland. The outcome shows that decarbonization of the heat supply with a dominant share of renewables is feasible, but it is challenged by the high cost of some options. In the given context (current energy and CO2 prices, no coercive measures), the rapid shift from conventional boilers to electrification via decentralized heat pumps and/or the introduction of targeted small-scale thermal energy networks utilizing cheap local resources like industrial excess heat is the most viable option. The replacement of natural gas boilers with electrification technologies also is recommendable because it would result in a sixfold reduction in specific CO2 emissions. Wide-scale application of heat pumps may require significant electricity grid reinforcement which ultimately may escalate the costs. Large-scale district heating systems are currently relatively expensive due to the high network costs and require a sustainable financing mechanism. To speed up the energy transition, policy interventions by the government are urgently needed.

Evaluation of a battery energy storage system in hospitals for arbitrage and ancillary services

The ambitious target of reaching net-zero greenhouse gas emissions by 2050 in the UK, which includes the decarbonisation of heat and electricity, means the increase of instantaneous power from non-dispatchable renewable energy sources (RESs). The intermittency of RESs will cause stability issues for the grid resulting from the mismatch between generation from RES and load demand. Battery energy storage systems (BESS) can match loads with generation and can provide flexibility to the grid. This study is proposing the health sector as a new flexibility services provider for the grid through BESS. The health sector has large loads that run throughout the year, and by managing this load it can provide flexibility to the grid. Four different scenarios have been evaluated for a range of behind-the-meter (BTM) BESS for a hospital in the UK to provide arbitrage and ancillary services considering the option of installing a photovoltaic (PV) system. It was found that BESS would not be economically viable through arbitrage alone since the payback period was always greater than the BESS lifetime. However, bundling services by participating in the ancillary services market resulted in payback periods as low as 3.10 years for some systems, and the net present value (NPV) could reach more than £5 million. This work provides evidence that the health sector can be a significant player in the transition to a renewables-led energy system, an exemplar for other sectors, and one of the solutions to recovery from the COVID19 pandemic.

Domestic heating with compact combination hybrids (gas boiler and heat pump): A simple English stock model of different heating system scenarios

The heat decarbonisation challenge remains substantial, competing low carbon solutions such as hydrogen and heat pumps (HPs) and the entrenched position of gas combination boilers create inertia in many markets. Hybrid appliances which can directly replace gas boilers may provide a low disruption, low-cost pathway to net zero in gas-reliant markets. Emerging compact combination (CoCo) hybrid heating appliances which combine a gas combi boiler and a small HP unit in one appliance have been modelled for the English housing stock across a range of different scenarios. CoCo hybrids offer sizeable energy demand reduction of up to 60% compared to current gas boilers, also reducing peak electrical demand by 10 GW compared to air source heat pumps. The control strategy for switching between HP and gas boiler is key in determining the scale of demand reduction. Modelling sensitivity to the HP size within CoCo hybrids showed that a 50% reduction in energy demand compared to gas boilers could be achieved with a standard 2.5 kW HP. A lack of clarity in regulation and policy incentives for hybrids exists. To drive innovation and performance improvement, product regulation for hybrids needs to be improved to support decarbonisation of heat with this promising technology. Practical Application Convenient, low disruption heat decarbonisation technology is crucial to the speed of deployment necessary to achieve net zero. This article defines the size of HP necessary to achieve rapid low disruption impact and distinguishes the types of compact hybrid which can deliver the highest decarbonisation impact while minimising in house disruption and the electrical grid impact.

Optimal Sizing of a Grid Independent Renewable Heating System for Building Decarbonisation

As the use of fossil fuels has led to global climate change due to global warming, most countries are aiming to reduce greenhouse gas emissions through the application of renewable energies. Due to the distributed and seasonal heating demand, the decarbonisation of heating is more challenging, especially for countries that are cold in winters. Electrically powered heat pumps are considered as an attractive solution for decarbonising heating sector. Since grid-powered heat pumps may significantly increase the power demand of the grid, this paper considers using local renewable energy to provide power for heat pumps, which is known as the grid independent renewable heating system including photovoltaic, wind turbine, battery storage system and thermal energy storage. This paper investigates a complete renewable heating system (RHS) framework and sizing the components to decarbonise building heating. The relationship between the reduction of gas consumption and the requirement of battery storage system (BSS) under the corresponding installation capacity of renewable components is analysed with their technical requirements. Then, according to different investment plans, this paper uses the particle swarm optimisation algorithm for optimal sizing of each component in the RHS to find a solution to minimise CO2 emissions. The results verify that the RHS with optimal sizing can minimise CO2 emissions and reduce the operational cost of natural gas. This work provides a feasible solution of how to invest the RHS to replace the existing heating system based on gas boilers and CHPs.

Framing branching points for transition: Policy and pathways for UK heat decarbonisation

This paper develops the use of the branching point concept as a tool to support key decisions for reorienting systems for sustainability. In this approach, a pathway is seen as arising from accumulation of many specific decisions which create momentum in a particular direction and so reinforce the irreversibility of the pathway. Three complementary approaches to branching point analysis are identified within the transitions literature: 1) in pathway-scenarios for sustainability, 2) framing key decision-points in historical analysis, 3) to deconstruct the politics of transition pathways. A case study of UK heat decarbonisation is used to apply the branching point concept. This analysis highlights the tension where a policy approach, framed by a sector-wide target, interacts with distinct socio-technical responses and an alternative policy approach to decision-points is proposed. This paper demonstrates the potential to develop branching point analysis into a tool to support and help structure policy decisions for transition.

A High Resolution Spatiotemporal Urban Heat Load Model for GB

The decarbonisation of heating in the United Kingdom is likely to entail both the mass adoption of heat pumps and widespread development of district heating infrastructure. Estimation of the spatially disaggregated heat demand is needed for both electrical distribution network with electrified heating and for the development of district heating. The temporal variation of heat demand is important when considering the operation of district heating, thermal energy storage and electrical grid storage. The difference between the national and urban heat demands profiles will vary due to the type and occupancy of buildings leading to temporal variations which have not been widely surveyed. This paper develops a high-resolution spatiotemporal heat load model for Great Britain (GB: England, Scotland a Wales) by identifying the appropriate datasets, archetype segmentation and characterisation for the domestic and nondomestic building stock. This is applied to a thermal model and calibrated on the local scale using gas consumption statistics. The annual GB heat demand was in close agreement with other estimates and the peak demand was 219 GWth. The urban heat demand was found to have a lower peak to trough ratio than the average national demand profile. This will have important implications for the uptake of heating technologies and design of district heating.

Development and testing of a novel geothermal wall system

Shallow geothermal energy systems have the potential to contribute to the decarbonization of heating and cooling demands of buildings. These systems typically present drawbacks as high initial investments and occupancy of wide areas. In this study, a novel energy wall system is proposed to overcome the limitations of conventional geothermal applications in urban areas. The system is characterized by ease of installation, low initial costs and applicability to existing buildings undergoing energy retrofitting. The paper illustrates the implementation of the prototype of such a system to an existing structure in Torino (Italy). An overview of the components is given together with the interpretation of an illustrative test carried out in heating mode. The data from both heating and cooling experimental campaigns allow us to highlight the potential of the proposed technology. The results suggest that an average thermal power of about 17 W per unit area can be exchanged with the ground in heating mode, while an average of 68 W per unit area is exchanged in cooling operations. The negligible impact on the stress–strain state of the wall and the surrounding soil thermal and hygrometric regime is also testified by the results collected. These aspects are associated with a reduced probability of interferences with other installations in highly urbanized areas, easiness of installation and affordable cost.

Temporospatial techno-economic analysis of heat pumps for decarbonising heating in Great Britain

The electrification of heat using heat pumps with renewable power presents an attractive and technically feasible pathway for decarbonising heating. However, until now, the uptake of heat pumps has been much slower than fossil-fuel-based heating, particularly in the UK. To accelerate the use of heat pumps for national-scale heat decarbonisation, this study proposes new approaches to synthesise high-quality temporospatial energy datasets (e.g. hourly depth-dependent region-based ground source temperature), a new framework that facilitates national-scale cost analysis using synthesised datasets rather than individual location-based analysis, and forward-looking analysis and discussions on potential subsidy structures and R&D directions for facilitating the transition to low-carbon heat using heat pumps. The results suggest that currently Renewable Heat Incentive (RHI) subsidised ground source heat pumps have the lowest levelised cost of heat (10–40% lower than gas boilers), benefiting from the high heating efficiency and the ‘feed-in-tariff’ style RHI subsidy. However, considering the change of future subsidies, required advances are analysed to improve the cash flow of owning heat pumps, improve heating efficiency,improve integration with low-cost power sources, and reduce heat demand via domestic energy efficiency improvements. These insights will help engineers and policy-makers to decarbonise domestic heat using heat pumps.

Hosting capacity assessment of heat pumps and optimised electric vehicle charging on low voltage networks

The decarbonisation of heat and transport using heat pumps (HPs) and electric vehicles (EVs) will require significant investment in low voltage (LV) networks both in terms of network reinforcement and in the provision of flexibility to avoid network upgrades where appropriate. In this paper, a heuristic methodology is presented to estimate headroom available for domestic EV charging optimisation in LV networks at different penetrations of HPs and a novel zonal approach is applied to EV optimisation. It was found that optimised charging of EVs can allow for a significantly higher penetration of EVs for a given HP penetration within the network, without the need for reinforcement. Significant improvements in terms of network hosting capacity were realised: for example, an increase from 34% EV and 50% HP penetration for dumb charging to 72% EV and 57% HP penetration for optimised charging was available for one particular case study. The level of improvement in hosting capacity was found to be strongly dependent on particular network topology and pre-existing demand; this reinforces the need for further study in unlocking the potential synergies of EV and HP uptake.

Making useful knowledge for heat decarbonisation: Lessons from local energy planning in the United Kingdom

Heat decarbonisation is challenging in many countries, but few studies address its ‘wicked problem’ qualities and the implications for producing useful knowledge. This paper elucidates the challenges by applying insights from science and technology studies, especially Callon’s concept of knowledge ‘frames’, to explain the fate of a prominent UK innovation – the EnergyPath Networks (EPN) and Local Area Energy Planning (LAEP) tool of the Smart Systems and Heat programme. The aim of the tool, which coupled an engineering model with local planning, was to provide authoritative knowledge to support local decision making. However, after six years of piloting with local authorities the future take-up of EPN and LAEP remained uncertain, for two key reasons. First the techno-economic knowledge frame encountered numerous overflows emanating from more potent political-economic and technological perspectives governing local priorities. Second the framing of local decision making neglected the marginality of energy planning at local government level. Our analysis shows the problems that arise when lab-based research and development prematurely frame energy system problems, before encountering societal and political contexts of use. Problem definitions and solutions for heat decarbonisation based predominantly on technical–economic knowledge lack requisite authority to progress this wicked problem, and must become more context-responsive.