Search

The 5th Generation District Heating and Cooling (5GDHC) network has great advantages in terms of integration of low-temperature resources, bi-directional operation, decentralised energy flows, and possible energy sharing. One way to develop the idea and concept of 5GDHC is to identify potential agents, including residential buildings, office buildings, shopping malls, data centres, electrical transformers, and so on, in 5GDHC in each target context. The prospects for 5GDHC have been assessed in light of the conditions in the Baltics. The multi-criteria analysis method was used to quantify the main identified barriers and drivers behind the implementation of 5GDHC systems. It should be noted that new urban areas in the Baltic states are being actively developed with low-energy buildings, so 5GDHS can be integrated to supply heat to these areas. The highest score in the multi-criteria assessment was achieved by Lithuania due to support availability and open heating market conditions. When all applied criteria are weighted equally, Estonia has the most favourable conditions for 5GDHC systems due to widespread use of heat pumps and greater excess heat potential. © 2022 The Author(s)

How is the UK market for domestic heat pumps developing? Recent events relating to geopolitics, politics, energy markets and wider society, widely regarded as unprecedented and disruptive, have the potential to create new challenges, opportunities, and drivers for heat pumps deployment in the UK. However, to date, there has been little attention to the consequences of such events. This report tackles this research gap. Using a systemic, co-evolutionary approach, it presents evidence of how the market for heat pumps has developed across four thematic areas of relevance to residential heat pump deployment – policy and regulation, business environment, wider society, and users – as well as on the focal technology itself. It ends by summarising the results of the review within a series of key messages and concludes that recent events have created a distinct opportunities to accelerate deployment whilst generating new challenges.

Pursuing long-term climate stabilisation scenarios subjects power, heat, industry, and transport sectors to undergo fundamental transitions towards fully renewable energy systems. Cost-efficient strategies involve the integration of energy vectors, introducing additional cross-sectoral electricity demand and flexibility for traditional power sectors. When performing cross-sectoral capacity expansion planning (CEP) analyses of low-carbon energy systems for decision making support, the underlying mathematical optimisation problems easily become intractable. To overcome the computational challenges of optimising real-world instances of future energy systems with adequate representations of temporal, spatial, and technological detail, this work investigates different modelling approaches for flexible heat pump systems at the power and heat sector interface of the long-term energy system model SCOPE SD. A comparative case study carried out for a net-neutral decarbonisation scenario in Europe and Germany highlights the implications of using model aggregation techniques. It is shown that the proposed modelling approaches can present computational benefits at only limited cost of result accuracy. However, poorly implemented grouping strategies can lead to high result inaccuracies and even a lack of performance improvements.

Over the last four years the RES4BUILD team has been working hard to support the transition to a clean energy future, developing integrated renewable energy-based solutions and tailoring them to the needs of users and installers. The project aimed to increase the uptake of such solutions for heating and cooling in buildings. This involved improving the performance and reducing costs of the most innovative components of the RES4BUILD solutions, including magnetocaloric and vapour compression heat pump technologies, PV/T collectors, borehole thermal energy storage and building energy management systems. In parallel to the technical work, partners collaborated with end-users and other stakeholders in the Netherlands and Poland to explore the needs and challenges with respect to decision making and implementation of integrated energy systems in their building(s). This, together with a full life-cycle impact assessment of the integrated RES4BUILD energy system, and a market review, aims to pave the route to market for integrated energy systems. The results are very encouraging, and we expect that in a refurbished multifamily building the RES4BUILD systems could deliver a significant reduction of CO2 emissions compared to traditional solutions. The booklet contain some of the key achievements and outcomes from the project. It can be also downloaded from the RES4BUILD websiteResults page or here.

Leakage of air in tumble dryers is an important parameter regarding the energy efficiency of the drying process. In general, tumble dryers are prone to leakage, therefore further investigation and optimization in this field is of great interest. This study investigates and quantifies leakage of air within the closed-loop system of an in-situ household heat pump tumble dryer. Each potential leakage location was characterized by leakage curve obtained either by isolated or cumulative measurements using system pressurization method. Based on the static pressure distribution within the closed-loop system, the leakage outflow and inflow were quantified. The leakage of air at the rear and front drum seal was evaluated with and without drum movement. The results indicated the highest leakage outflow rate at the heat pump housing, which represents 12,6% of the total drying air flow rate within the closed-loop system. Sealing heat pump housing improved the condensation efficiency from B to A class according to the IEC 61121.

Increasingly stringent regulations and new applications require selecting improved refrigerants for heat pumps. The selected refrigerants should be environmentally friendly and maximize the performance of the heat pump process. Systematic refrigerant selection methods usually model the compressor with onefixed isentropic efficiency identical for all refrigerants. However, compressor studies indicate that the isentropic efficiency may be highly refrigerant-dependent. Herein, the need for a refrigerant-dependent compressor model for refrigerant selection is investigated. For this purpose, a refrigerant-dependent compressor model is combined with an integrated design of refrigerant and heat pump process. To guarantee a comparable nominal heating power among refrigerants, the compressor design is tailored to the refrigerant by expanding the refrigerant-dependent compressor model toward compressor sizing. Integrating compressor design into systematic refrigerant selection is enabled by a computationally efficient model implementation. Accounting for refrigerant-dependent compression substantially changes the resulting refrigerant ranking compared to the widely used assumption of identical isentropic efficiencies forall refrigerants: The best-performing refrigerant is not even identified among the best ten refrigerants when assuming identical isentropic efficiencies.Consequently, compression is identified as the main driver for differences in refrigerant performance. Therefore, integrating refrigerant-dependent compressor models is crucial for systematic refrigerant selection., Energy Technology, 11 (4), ISSN:2194-4296, ISSN:2194-4288

Presentatie voor bewoners van Zuidwolde (Groningen) om hen te informeren over opties voor duurzame installaties die toegepast kunnen worden voordat het lage temperatuur warmtenet wordt aangelegd.

Greenhouse gas (GHG) emissions from the building sector in 2021 contributed 36% of overall US carbon dioxide (CO2)­ emissions according to Energy Information Administration (EIA 2021). The space heating of buildings, a large part of the overall emissions, relies heavily on natural gas. Electrification with a heat pump eliminates onsite emissions from space heating but results in indirect emissions from the electric grid. The generation mix of the electric grid evolves over time and varies widely by geographic location. This study presents a temporal and spatial distribution of the impacts of electrification of space heating in residential and office buildings. A comprehensive analysis was conducted to compare modeled GHG emissions over the operational life of a heat pump and a gas furnace installed between years 2022-2036 in six regions across the US. A residential home and a three-story medium office building were considered in this study and Energy Plus prototype models were used to simulate the energy use for space heating in 99 locations across the continental US. GHG impact calculations accounted for long-run marginal emissions from electricity generation from 2022 to 2050, emissions from natural gas combustion, and emissions from leakage of methane and refrigerant. The population weighted average results in the US for the residential home show a 30 - 68% reduction in 100-Year global warming potential (GWP) emissions for a heat pump over a gas furnace, with savings increasing as the year of the installation is deferred (2022-2036). Similarly, for the medium office building, the emissions change ranged from a 1% increase to 51% reduction. Office buildings show lower GHG emission savings in the initial years because of increase in refrigerant charge from the installation of a heat pump and reliance on electric-reheat in the variable air-volume boxes.

Представлены данные Всемирного сообщества возобновляемой энергетики 21-го века REN21 и Института экологических технологий AEE INTEC (Австрия), Международной ассоциации гидроэнергетики. В 2021 году в электрогенерации на основе ВИЭ отмечено лидерство гидроэнергетики (1360 ГВт, 4250 ТВт·ч/год); на втором месте ветроэнергетика (845 ГВт, 1980 ТВт·ч/год); далее солнечная энергетика (942 ГВт, 1138 ТВт·ч/год); биоэнергетика (143 ГВт, 602 ТВт·ч/год); геотермальная энергетика (16 ГВт, 105 ТВт·ч/год). В теплогенерации на основе ВИЭ на первом месте энергия биомассы (3892 ТВт·ч/год); солнечное теплоснабжение (522 ГВт, 425 ТВт·ч/год); геотермальное теплоснабжение (108 ГВт, 284 ТВт·ч/год). В России на 01.01.2022 г. установленная мощность и выработка электрической энергии для всех электростанций страны составляли соответственно: 246,6 ГВт (100%) и 1114,5 ТВт·ч/год (100%); в том числе ГЭС — 50 ГВт (20,26%) и 209,52 ТВт·ч/год (18,8%), СЭС — 1,96 ГВт (0,8%) и 2,25 ТВт·ч/год (0,2%); ВЭС — 2,035 ГВт (0,83%) и 3,62 ТВт·ч/год (0,35%). Общая установленная мощность возобновляемой энергетики (ВЭ) РФ составила 54 ГВт (20,9%), выработка электрической энергии — 210,76 ТВт·ч/год (20,1%) при выработке в 2021 г. всеми электростанциями России 1047 ТВт·ч/год (100%). Описано состояние российского рынка ВЭ, роль правительства в его формировании и регулировании. Представлены результаты деятельности в 2021 г. малой гидроэнергетики (1220 МВт), солнечного теплоснабжения (70 МВт), геотермальной энергетики (электрогенерации — 84 МВт, 428 тыс. МВт·ч/год; теплогенерации — 110 МВт, 280 тыс. МВт·ч/год), БиоЭС — 65,2 ГВт·ч/год, биотеплогенерации — 29,8 ТВт·ч/год., The data elaborated by the Renewable Energy Policy Network for the 21st Century REN21 and the Institute of Sustainable Technologies AEE INTEC (Austria), the International Hydropower Association are presented. In 2021, the leadership of hydropower was noted in RE generation (1360 GW, 4,250 TWh/year); wind energy (845 GW, 1,980 TWh/year) was in second place; then solar energy (942 GW, 1,138 TWh/year); bioenergy (143 GW, 602 TWh/year); geothermal energy (16 GW, 105 TWh/year). In heat generation based on RES, biomass energy is in the first place (3,892 TWh/year); solar heat supply (522 GW, 425 TWh/year); geothermal heat supply (108 GW, 284 TWh/year). In Russia, as of 01.01.2022, the installed capacity and electricity generation for all power plants in the country were, respectively: 246.6 GW (100%) and 1114.5 TWh/year (100%); including hydroelectric power plants — 50 GW (20.26%) and 209.52 TWh/year (18.8%), PPS — 1.96 GW (0.8%) and 2.25 TWh/year (0.2%); WPP — 2.035 GW (0.83%) and 3.62 TWh/year (0.35%). The total installed capacity of RE of the Russian Federation was 54 GW (20.9%), the generation of electric energy was 210.76 TWh/year (20.1%) when generated in 2021 all power plants in Russia 1,047 TWh/year (100%). The state of the Russian renewable energy market, the role of the government in its formation and regulation is described. The results of the activities in 2021 of small hydropower (1,220 MW), solar heat supply (70 MW), geothermal energy (power generation — 84 MW, 428,000 MWh/year; heat generation — 110 MW, 280,000 MWh/year), bioelectric power — 65.2 GWh/year, bioteplogeneration are presented — 29.8 TWh/year.

In contrast to rural distribution grids, which are mostly “feed-in oriented” in terms of electrical power, urban distribution grids are “load oriented”, as the number of customer connections and density of loads in urban areas is significantly higher than in rural areas. Taking into account the progressive electrification of the transport and heating sector, it is necessary to assess the required grid optimization or expansion measures from a conventional, as well as an innovative point of view. This is necessary in order to be able to contain the enormous investment volumes needed for transforming the energy system and aligning the infrastructures to their future requirements in time. Therefore, this article first explains the methodological approach of allocating scenarios of the development of electric mobility and heat pumps to analyzed grids. The article continues with describing which power values need to be applied and which conventional and innovative planning measures are available for avoiding voltage band violations and equipment overloads within the framework of strategic grid planning. Subsequently, the results of grid planning studies are outlined and evaluated with an assessment model that evaluates capital as well as operational costs. On this basis, planning and operation guidelines for urban low-voltage grids are derived. The main result is that low-voltage grids can accommodate charging infrastructure for electric mobility, as well as heat pumps to a certain degree. In addition, it is concluded that conventional planning measures are not completely avoidable, but can be partially avoided or deferred through dynamic load management.

Improved end-user engagement is considered to be a key factor in decarbonization efforts towards climate neutral energy systems. While first adopters are already actively seeking ways how to optimize their energy consumption, a true shift in consumer behaviour can only be achieved if the financial benefits are well established and presented. The study aims at estimating the economic performance of end-user engagement in provision of demand response services using air-to-air heat pumps as the underlying technology. The results of the paper help evaluate in a real data setting whether the existing market framework provides sufficient incentives to facilitate end-user participation in the demand response service.

Electrification is key to reaching decarbonization goals and curbing the impacts of climate change. Multi-function integrated heat pumps provide opportunities to reduce installation costs and space required for all-electric buildings. Multi-function heat pumps can use the compressor heat during a space cooling operation, which is otherwise wasted to the ambient through the condenser coil, to heat up water for domestic use. This project tested a multi-function heat pump that combines space cooling, dehumidification, ventilation, and domestic hot water (DHW) in a compact system (POD). Evaluation of the POD was conducted in environmental chambers simulating various indoor and outdoor conditions. Air flow and ventilation rates were calibrated, and the system was operated as per manufacturer recommendations. Performance metrics were compared across two operational modes of the POD: space cooling only and space cooling with DHW production. Operational mode decisions of the system controls impact the performance, for instance, cooling COP increases during operation with DHW heating compared to space cooling-only mode. In the combined mode, it was also observed that the cooling COP diminishes by 0.1 with every 3°F rise in tank temperature. The results indicate that a multi-function heat pump performance is not only dependent on the indoor and outdoor conditions but also on the DHW tank water temperatures. This study describes the performance of an integrated space conditioning and water heating system, while shedding light on the system metrics that would be useful to evaluate and rate such systems.

New green energy policies are encouraging district heating (DH) companies to exploit heat production by power-to-heat (P2H) assets, e.g., heat pumps (HPs) and electric boilers (EBs). Therefore, they are shifting to exploit these assets in their distribution network besides the traditional central combined heat and power (CHP) units in their production chain. It will lead to an increasingly complex interaction between DH networks and electricity markets. This article proposes an economic model predictive control (EMPC) framework to investigate how DH companies can manage this extra complexity and if they can contribute in an efficient way towards balancing the production and consumption of electric power in smart grids through playing in the reserve capacity markets. The framework is applied to a real world case study and the results are discussed. The results show the new paradigm increases operation costs. However, reserving a part of the capacity for playing in reserve capacity market will not only make up for the extra costs to some extent, but also improve the capability of providing regulating power.

In this study, the energy, exergy and economic (3E) analyses were performed for the photovoltaic/thermal collector-assisted heat pump domestic water heating system under two different climatic regions (Hakkari and Trabzon) in Turkey. Designed photovoltaic/thermal collector-assisted heat pump domestic water heating system with a storage tank having larger volume and cross-flow heat exchanger in Turkey can be considered as novelty of this study. The system modelled with the help of TRNSYS simulation code by using real weather data and energy analysis was performed based on year-round simulation results. And then, exergy and economic analyses were obtained based on monthly average temperatures. The system considered in this study was also compared economically with conventional natural gas and electricity water heating systems. According to the results, the maximum energy and annual average exergy efficiencies of the considered system were 68% and 22.3%, respectively, for Hakkari, and 67% and 21.4%, respectively, for Trabzon. Although Hakkari has cold climate conditions, the investigated system had lower energy consumption costs than conventional systems. The annual energy consumption costs of the system for Hakkari and Trabzon were calculated as 67.14$ and 135.75$, respectively. The results bring out that although the investment of the system is feasible for Hakkari, it is not feasible for Trabzon.

Transformation of the heating sector is recognized as being essential for ensuring reliable and affordable energy services provided with reduced consumption of energy sources, diminished impact on the environment and less import dependency. The possibility of utilizing energy sources that otherwise would be wasted needs to be considered and treated as a big advantage of district heating systems. Despite many advantages, sewage wastewater heat is still a mostly unused resource at the global level and a totally unused energy source in Serbia, while data about the potential of this energy source are lacking. This research proposes a methodology for the determination of the technical potential of waste heat from wastewater treatment facilities for use in district heating systems by heat pump application. Data from existing wastewater treatment facilities are used for providing data for replication in cities without wastewater treatment plants but with district heating systems. An estimation of the recoverable heat energy potential of wastewater is used for evaluation of some effects that could be obtained through its full utilization for heat production in the existing district heating systems. Three groups of indicators are selected for analysis focusing on district heating systems' energy performance (primary energy factor, specific heat consumption per degree day and heating area), the security of energy supply (import dependency, Shannon Wiener diversification index, the share of renewables) and environmental impact (carbon dioxide emission coefficient). Values of the selected indicators are determined for the current state of district heating systems and for the possible future state that could be achieved after full utilization of sewage wastewater potential. The proposed methodology is applied to Serbia, as a case study. It has been shown that all analyzed indicators for the projected future would have more preferable values compared to the values that correspond to the current state of the district heating systems. The use of this renewable energy source should provide primary energy savings of 5% per year, reduction of carbon dioxide emission of 6.5% per year, reduction of import dependency of DH systems of 9.8% and improved diversification of energy sources of 21%.

Reversible heat pumps are increasingly adopted for meeting the demand for space heating and cooling in buildings. These technologies will play a key role not only in the decarbonization of space air conditioning but also in the development of 100% renewable energy systems. However, to assess the achievable benefits through the adoption of these technologies in novel applications, reliable models are needed, capable of simulating both their steady-state operation and dynamic response at different conditions in terms of heating loads, outdoor temperatures, and so on. The operation of heat pumps is often investigated by highly simplified models, using performance data drawn from catalogs and paying scarce attention to the critical influence of controllers. In this respect, this paper proposed an integrated thermodynamic and control modeling for a reversible air-to-water heat pump. The study considered a heat pump alternatively equipped with variable-speed compressors and constant-speed compressors with sequential control. The developed modeling was then used to investigate the operation of an air-to-water heat pump serving an office building in Italy. Results show that the model provided insights into the transient operation of variable-speed heat pumps (e.g., the settling time). Regarding constant-speed heat pumps, the model provided hints of interest to the control engineer to prevent, in the examined case study, the risk of quick compressors cycling on low-load heating days or when low-temperature heating devices are supplied. Finally, using a control strategy based on a heating curve for the variable-speed heat pump, results show the potential for a sensible increase in the average coefficient of performance, from 17% up to 50%.

Data centres are large global energy consumers that create low-temperature waste heat. To alleviate the impact of the temperature increase on the information technology equipment, the data centres are cooled with different technical solutions, drastically increasing the facilities’ power consumption. In different regions, the use of data centre waste heat combined with heat pumps in district heating systems was identified as a lower-cost heat energy generation solution compared to alternative fossil or renewable energy-based heating solutions. The research paper aims to identify the data centre’s waste heat potential as an energy source in district heating in Latvia. The technical and economic potential for using heat pumps in the data centre’s waste heat systems was evaluated. To reach the goal of the study, a mixed methodological approach was used divided into four steps: the creation of the statistical calculation method, stakeholder survey to evaluate the energy consumption, mapping of the quantitative results to evaluate technical potential and distribution patterns, and system dynamics modelling to evaluate possible adoption scenarios of the technological solutions. The results of the research reveal a heterogenic distribution of data centres in Latvia, which limits the use of waste heat at the national level. Furthermore, the study identified the total waste heat potential of data centres in Latvia and provided recommendations for the adoption of data centres’ waste heat based on the results of the system dynamic simulations.

Nineteen percent of global final energy consumption is used to generate electricity and heat in buildings. Therefore, it is undisputed that the building sector needs to cut consumption. However, this reduction needs to be driven by data analysis from real building operations. Starting from this concept and with the aim of proving the benefits deriving from the installation of a monitoring system in a real operating environment, in this work a monitoring system has been installed to monitor the centralised heating and cooling system of a residential building composed of 57 residential units. The data acquired from the installed sensors are collected and subsequently analysed in an ad hoc tool to detect anomalies, performance decay, malfunctions, and failures of the machines, as well as to understand if the implemented management strategy is appropriate in terms of energy and cost savings. The results show the key role of the data acquired by the monitoring system and analysed by the developed tool in terms of ability to detect failures and malfunctions in both the heating and cooling modes, as well as to help both in finding the proper management strategy and in identifying the performance deviation precursors of machine failure.

This paper presents possible applications of heat pumps in buildings during the energy transformation and decarbonization of a country whose energy sector is highly centralized and based on coal. Contemporary cities are spreading beyond the existing borders and new areas cannot be supplied by the existing centralized district heating system. The only form of energy that is available on the outskirts of cities is electricity, which means that it must be used for all energy needs, including heating. In such a case, the use of heat pumps is perfectly justified in terms of energy, economy and environment, especially when they are coupled with photovoltaic systems. Hypothetical micro housing estate energy systems based on photovoltaics and heat pumps are analyzed in the paper. New options for configuration and operation of the energy systems are considered. Results of a simulation study show that by creating a common local electricity network and a local heating network powered by a central heat pump, the direct use of electricity generated in the local photovoltaic systems increases from 25% to at least 35%, thanks to enabling more even storing and consuming of solar energy during a day, compared to the independent operation of energy systems at individual houses.

This paper presents an economic assessment of three drying systems (DS) with different configurations: diesel-powered (DDS), grid-powered (GDS), and photovoltaic-powered (PVDS). The third configuration, PVDS, presents important technological innovations regarding the electric configuration (stand-alone PV, without batteries or grid support) and the heat pump technology used (optimized for drying the recirculated air, which permits a reduction in the electricity consumption by more than 45% if compared to a diesel air-heater or an electric resistance). The profitability of the investment required for the installation of the three systems is proven by calculating the profitability index (PI), the internal rate of return (IRR), the payback period (PBP), and the levelized cost of energy (LCOE). All the indicators show good profitabilities for the three technologies (the PI values range from 6.78 to 10.11, the IRR values range from 24% to 37%, and the PBPs are between 3 and 4 years), but the PVDS clearly offers important economic advantages: its PI and IRR are more than 40% higher, the PBP is 25% shorter, and the LCOE is between 40 and 47% lower than for the two other systems. The results of this analysis correspond to a particular base case but are obviously sensitive to geopolitical and economic changes: the ultimate strength of the PVDS configuration is its resilience against a possible rise in electricity and diesel prices, reducing the uncertainty for investors and policymakers.

The widespread adoption of low GWP alternative refrigerants across Europe is critical to achieving long-term carbon reduction emissions from the Refrigeration, Air Conditioning and Heat Pump (RACHP) sector. The RACHP sector has been identified as being responsible for significant greenhouse gas emissions through direct emission (leakage of high GWP refrigerants) and indirect emissions (energy use). The changes to EU's Fluorinated greenhouse gases (F-gas) regulation No 517/2014, which came to force since 1st January 2015, has enacted restrictions on the use of halocarbon refrigerants in certain applications with the intent of reducing the F-gas associated emissions in the EU region. There are currently inconsistent levels of knowledge and awareness of how alternative refrigerants can be sustainably procured and utilised. This paper provides an understanding of the needs for skills in some European countries, specifically covering the general overview of the “as installed“ RAC use, the current training provision, the potential use and status of alternative refrigerants and recommendations on procurement process. Furthermore, the paper discusses the availability of skills and existing training materials and template in specific European countries.

District heating has proven to be an efficient way of providing space heating and domestic hot water in populated areas. It has also proven to be an excellent way to integrate various renewable energy sources (RES) into the energy system. In Estonia, biomass covers most of the heat demand, but carbon-intensive fuels are still used to cover peaks and lows. Heat pumps can be a good solution for rural areas, as there is usually plenty of land available for heat pump facilities. In addition, heat pumps require low-grade heat sources such as ambient air, groundwater, lakes, rivers, sea, sewage water, and industrial waste heat. One of the downsides of heat pumps is the need for large investments compared to boilers fired by natural gas and biomass, and electric boilers. This study examines the impact of heat pump use on consumer prices for district heating in rural district heating networks in Estonia.

Combined borehole (BH) heat storage systems, batteries and power-to-gas system have the potential to shift load, reduce carbon emissions, provide hydrogen for fuel cell cars and save energy costs for end customers on an extended scale. This study proposes an optimal operation strategy for a local multi-vector energy storage system, which includes batteries, BH thermal storage, the power to the gas system and the fuel cell cars system. These storage systems can be divided into the short-term storage system and inter-seasonal storage system or low capacity storage system and high capacity storage system. The optimisation problem is divided into a two-stage framework, (i) the first stage optimisation is seasonal optimisation, which gives an approximate optimal operation plan for BH heat storage systems in the following year; (ii) the second stage develops a day-ahead robust optimal plan for all storage systems. Finally, the algorithm will return to seasonal optimisation to update the operation plan for BH heat storage systems to make results more accurate. The test case of eight nodes illustrates that the combined energy system of photovoltaic, heat pump power to gas, BH and batteries can provide hydrogen to fuel cell cars and significantly save power costs for customers with the optimal operation.

Air-to-water heat pumps are quite often integrated with a hot-water tank, to better decouple the generation from the delivery of heat in buildings and to improve the overall performance of the system. The estimation and prediction of the coefficient of performance of the heat pump is extremely important to enforce efficiency, but it is also a very challenging task, due to the strong dependency of the performance on disturbances and operating conditions. Another source of potential model mismatch is the variable water flow rate in the condenser side induced by the heat pump low-level control logic, which gives rise to a non-trivial nonlinear system. In this letter, we tackle the problem to develop and properly tune an equivalent control-oriented model for the system, i.e. heat pump and tank, under variable flow rate conditions on both the condenser and load side, while still preserving good prediction capabilities of the model, with no tank temperature nor mass flow rate sensors. In particular, we focus on a real case study consisting in an air-to-water heat pump system and a $ 150{m^2}$ building located in SYSLAB, Department for Electrical Engineering, Risoe Campus, Denmark Technical University. The quality of the developed models is then evaluated through a nonlinear model predictive controller suitably designed and checked against detailed reference models previously developed. Finally, different sensitivity analyses are performed, which witness the robustness of the proposed algorithm.

The majority of heat in the UK comes from the combustion of natural gas, and heat is responsible for 37% of the nation’s carbon emissions. Thus the decarbonisation of heat is a major challenge. Electrification is one possible approach to decarbonisation; however, huge increases in the electrical grid’s generation and transmission capacity would be needed to meet the peaks in space heat demand during cold winter weather. Thermal energy storage (TES) may have a role to play in alleviating this problem, by shifting heat demand by hours or longer periods, enabling peaks to be shaved. This work considers the utility of two varieties of thermal energy storage for this application. Adsorption thermal storage (ATS) is a technology offering long term storage at a high energy density, but is a costly and relatively immature option. By contrast, storage of sensible heat in hot water tanks is already widespread, although it has relatively short storage duration and lower density. Here, we simulate the deployment of these technologies in a small residential neighbourhood, in tandem with demand-side management (DSM), to attempt the reduction of peaks in demand. With no storage or DSM, electrification causes peaks to increase by a factor of 2.36. Results so far suggest that both TES technologies have potential to reduce peaks, with a 14% decrease achievable by either 5 m3 of hot water storage, or 0.25 m3 of ATS, in each dwelling. However, it is thought unlikely that adsorption storage is attractive for a purely peak shaving application, given its cost and complexity.

Unlike power sector decarbonisation, there has been little progress made on heat, which is currently the biggest energy consumer in the UK, accounting for 45% of total energy consumption in 2019, and almost 40% of UK GHG emissions. Given the UK���s legally binding commitment to "Net-Zero" by 2050, decarbonising heat is becoming urgent and currently one of the main pathways involves its electrification. Here, we present a spatially-explicit optimisation model that investigates the implications of electrifying heat on the operation of the power sector. Using hourly historical gas demand data, we conclude that the domestic peak heat demand is almost 50% lower than widely-cited values. A 100% electrification pathway can be achieved with only a 1.3-fold increase in generation capacity compared to a power-only decarbonisation scenario, but only, by leveraging the role of thermal energy storage technologies without which a further 40% increase would be needed.

[en] The global ambitions to hamper the greenhouse effect has led to ambitious targets for increasing renewable energy use. This, in combination with recent years' vast development of wind and solar power, implies that there will be significant amounts of variable renewable electricity (VRE) in future energy systems. With the inherent variability in VRE production comes a need for increased contingency in power systems. This requires both controllable production and consumption of power to cope with VRE deficits and surpluses. The purpose of this doctoral thesis is to investigate the potential for providing such power balancing services from Swedish district heating systems (DHS). Analyses are made for different system levels: community, regional, and national. Computer simulations of DH production systems with combined heat and power (CHP) plants, heat pumps, and thermal energy storage (TES), operated to supply a power balancing demand, are here shown to potentially reduce VRE deficits and surpluses. The results further show that reducing peak deficits and/or surpluses mainly depends on the installed capacities in CHP units and/or heat pumps. However, annual deficits or surpluses are reduced more if the system includes a TES. Also, the shares of wind and solar power in VRE mixes are shown to be relevant for fuel use and system performance. Solar-dominated VRE promotes heat pumps, reduces fuel use in CHP, and motivates a seasonal operation of TESs. Wind-dominated VRE matches with high capacities in CHP units, yields increased fuel use and motivates short-term operation of TESs. A crucial limitation is competition for the heat load between heat pumps and CHP units, which reduces the potential for CHP production. Competition between stored heat and heat pumps also occurs in systems with smaller TESs and large amounts of surplus electricity. In order for power balancing services to be economically viable for DHS operators, changed market structures that appropriately value the delivered services are likely required. The overall conclusions are: DHSs can offer power balancing, a high share of PV is essential to reduce fuel use, and finally, seasonal TESs are needed to cope with large amounts of surplus heat and/or replacement of peak load units.

This report summarizes the main activities carried out on the eld of supercoolers in the H2020 TRI-HP project. The overall goal of the TRI-HP project is the development of trigeneration systems based on electrically driven natural refrigerant heat pumps coupled with renewable electricity generators (PV). The systems are aiming to provide heating, cooling and electricity to multi-family residential buildings with a self-consumed renewable share of 80 %. One of the systems developed is based on a supercooling ice slurry heat pump. A successful development of such system relies on the development of a heat exchanger that can supercool water to temperatures around −2 °C to −3 °C without forming ice, the so-called supercooler. This report summarizes the development and testing results of such supercoolers. The specific goal of the project on the ice slurry field was to develop a compact and reliable supercooler to be used as an evaporator for a 10 kW heat pump using natural refrigerants heat pumps such as propane and CO2. This goal has been achieved by applying coatings (organic, inorganic or a mixture of them) on very compact flat plates heat exchangers. Results shown in this report show not only the reliability of the operation of supercoolers below 0 °C, but also prove the very ambitious measurable targets established at the project proposal phase, i.e. stable operation with a supercooling degree of 4 K. This achievement represents a significant progress respect state of the art Japanese supercoolers that operate at 2 K supercooling degree. Results achieved within TRIHP represent a ground-breaking progress in Europe where nothing similar has been achieved before. From the authors’ knowledge, the supercoolers tested here are the first operational ones at this capacity range ever develop in Europe. In this deliverable results of icephobic coated and nickel treated heat exchangers are summarized. Six heat exchanger with icephobic coatings were tested at SPF laboratories. As reference, a heat exchanger without any coating and a commercial heat exchanger coated with a ceramic anti-fouling coating was used. For coating comparison, three different chemical families were tested at three different mass flows. Experiments of coated heat exchangers show average supercooling degrees in the range of 3 K to 4 K. The anti-fouling coatings performed worse compared to the reference non coated heat exchangers with an about 70 % lower average supercooling degree. All icephobic coatings improved the supercooling degree respect to the reference non-coated case by 7 % to 44 % at 1000 kg/h. The target of 5 kW supercooling power has been reached with two coatings for a mass ow rate of 1000 kg/h in the water cycle. For a mass flow rate of 2000 kg/h a supercooling power of about 6 kW has been reached for five coatings at a temperature of −2.5 °C and hold constantly for a time span of 3 h. Some coatings could reach lower temperatures at this mass flow but the experimental setup was limited to this supercooling power. Thus, the full potential of these supercoolers in terms of capacity is still to be found. The two coatings performing best in the heat exchanger tests were both from the family class hybrid organic-inorganic silane sol-gel (HOIS). Both coatings showed the best results in the small scale laboratory tests as well. From previous investigations it was found that high phosphorous nickel plating creates a beneficial surface to achieve low temperatures. In order to analyse the potential benefits two different types of plate heat exchanger, i.e. brazed and gasketed, were evaluated. Due to the smaller laboratory setup capacity, the heat exchangers were 25 % smaller compared to those tested using icephobic coatings. As reference, the same heat exchangers were tested without any treatment. The nickel layer shows an increase of the supercooling potential of 7 % for a brazed heat exchanger and a water mass flow of 500 kg/h. For a gasketed heat exchanger of similar capacity, little benefits were observed. An average supercooling power of 2.3 kW was achieved on these experiments due to a lower mass flow and heat transfer surface area compared to the heat exchanger prototypes used for the icephobic coatings experiments.

This work analyzes how an over 99% efficient charging circuit and electrical offset fields enhance the coefficient of performance (COP) of electrocaloric heat pumps, an emerging technology with zero global warming potential. The COP is studied for Carnot-like cycles regarding the material’s permittivity and dissipation factor, and the system’s charging efficiency. Compared to the Carnot limit, a relative material COP of 50.4% is calculated for a lead magnesium niobate (PMN) ceramic, and enhanced to 87.4% by an offset field. The offset avoids high loss at low fields, where the non-linear permittivity-related dissipative loss is highest. A 99.2% efficient gallium nitride half-bridge switched-mode converter is used as charging circuit. Including the charging loss, the calculated relative system COP of 11.9% is significantly enhanced to 28.6% by an offset field. The 0.8% external loss exceeds the material loss (dissipation factor below 0.2%), reducing the system COP from the material COP. Compared to 80% efficient state-of-the-art resonant circuits for electrocalorics, this work’s approach reduced charging loss 20 times. The work contributes to transfer the high COP of electrocaloric materials also to electrocaloric heat pump systems.

Swimming pool heating systems are known as one of the best flexible resources in buildings. However, they can be flexible only for a certain number of hours throughout a day due to the comfort constraints of the users. In this study, a new approach is proposed to determine a group of contract hour sets to procure maximum flexibility of swimming pool heating systems supplied by heat pumps for trading in the regulation market while respecting the comfort of users. The main advantage of the contract hour sets is the certainty in response to flexibility requests. The proposed approach consists of three main steps. First, a stochastic mixed-integer linear program is proposed to find the optimal operation of a swimming pool heating system that has agreed to provide flexibility in a contract hours set. Then, a metric is proposed to evaluate the effectiveness of contract hour sets using the results obtained in the first step. Finally, an algorithm is proposed to identify a group of the most efficient contract hour sets using the calculated metric. The proposed approach is validated through comprehensive simulation studies for a summerhouse with an indoor pool heated by a heat pump. Also, a cost–benefit analysis is performed to examine the feasibility of these contract hour sets from financial viewpoint. Simulation results show that the maximum contract hours can vary from 2 to 12 h depending on the building occupation pattern and the minimum payment to owners is between 0.03 to 0.06 (Euro/kW).

Increasing the use of heat pumps is an important measure for reducing carbon emissions in the heating sector as well as natural gas imports. This report uses an electricity sector model to investigate the effects of an accelerated expansion of the heat pump stock on the German electricity sector in 2030. Adding around six million heat pumps would increase electricity demand by nine percent in 2030; to meet this demand with solar energy, photovoltaic capacity would have to be expanded by 23 percent. Natural gas imports could be reduced by 15 percent. From a macroeconomic perspective, the higher the price of natural gas, the more advantageous it becomes to increase the use of heat pumps. Accelerating the transition to heat pumps, however, requires an ambitious and coordinated policy program that also focuses on the production capacity of heat pumps and on providing advanced training to workers - a kind of “Apollo program” for heat pumps., DIW Weekly Report

The focus of the experimental work was on shallow spiral geothermal heat exchanger configurations. Real-scale experiments were carried out for vertically oriented spiral collectors (helix) in sand and soil. One objective was to develop a measurement concept in laboratory environment to create a framework for a validated database. This database serves as the basis for further and new development of engineering design tools. To achieve the highest possible data-point density in the observed environment, temperature sensors and a fiber-optic temperature measurement system (DTS) were used. Soil probes were taken in situ before and after the measurements and analyzed at a thermophysical laboratory to determine material properties. The heat flow was controlled by an electric heating cable, which was installed in the form of a spiral-shaped heat exchanger in a 1 m³ container. To guarantee constant boundary conditions, the measurements were carried out in a climate chamber at a defined ambient temperature. The evaluation of the transient response behavior is spatially resolved. The results are coordinate-based temperature points, which describe temperature gradients in all axes of the container over time, which are combined with known soil properties. The collected data was used to develop computational fluid dynamic (CFD) models, which are used to extend the variety of geometry and soil configurations for developing new design tools.

The advent of the COVID-19 pandemic puts stress on the requirements of indoor air quality. Significant improvements in the design of building ventilation systems have become necessary, as this allows for the supply of higher quantities of outdoor air in buildings. Additional capital investment is necessary for increases in the size of ventilation fans and ducts, as well as for the installation of efficient air-to-air recuperators, to recover the enthalpy of the rejected air. To address the increased operation costs, smart strategies are necessary to make rational use of the ventilation system. The required modifications are studied in the example of an 18-zone office building located in Volos, Greece. The building’s energy performance is studied by means of transient simulation. Operation of the ground-coupled heat pump, the upgraded ventilation system and the high-performance recuperators and filters’ interactions is presented in detail at various time scales. The results show the effect of increased ventilation requirements of new and renovated office and commercial buildings in the post-COVID era. The added capital equipment and operation costs must be met with a strong and sustained engineering effort. Especially in the case of nZEB buildings, the protection of public health must be attained, with reduction of the added electricity consumption penalties, in order to keep the nZEB character of the building.

Novel energy technologies are typically associated with large investments and environmental impacts generated in the construction phase. In this work, we present a systematic approach to optimally design residential energy systems, considering (prospective) costs and life cycle greenhouse gas (GHG) emissions of a large set of low-carbon energy technologies and sources. To achieve this, an optimization problem has been formulated and is tested on several scenarios considering climate-specific heat and electricity demand as well as scenario-specific conditions, such as the flexibility of grid electricity tariffs and associated GHG intensities. With GHG-intensive grid electricity supply and flexible energy tariffs, we recommend to implement policy measures to encourage the investment in residential solar PV-coupled batteries and heat pumps, especially in the near future. The inclusion of environmental impacts generated from the production of energy technologies cannot be neglected; they should be considered during the design phase of residential energy systems. Current high electricity and natural gas prices result in the installation of low-carbon energy system components. This implies that battery systems are already an effective option to reduce the reliance on carbon-intensive and expensive energy supply. And lastly, the large-scale deployment of residential lithium-ion batteries might be limited by global lithium production. This implies that energy system designers should consider alternative electricity storage technologies in their energy technology portfolio., Applied Energy, 331, ISSN:0306-2619, ISSN:1872-9118

This work combines a 99.2% efficient GaN-based low-voltage fast-switching half-bridge converter with a Si-based high-voltage slow-switching and almost lossless switched capacitor multiplexer using a partial power processing approach to a six-level prototype with 99.74% efficiency. A loss breakdown shows how the ideal partial power processing efficiency is theoretically increased to 99.84% by using four additional voltage levels, but then reduced to the measured efficiency by the additional static and dynamic losses of the multiplexer. For electrocaloric heat pumps, an emerging technology for cooling and heating applications with zero global warming potential, such high charging efficiencies enable a high heat pump system coefficient of performance (COP). Based on available data of electrocaloric lead magnesium niobate (PMN)-based samples, and based on a first-principle and best-case analysis for Carnot-like cycles, it is predicted that the 99.74% electrical charging efficiency in combination with the electrocaloric material data enables to surpass 50% of the thermal Carnot limit (for cooling with a heat pump). Ultra-high efficiency of power converters thus pave the way towards future electrocaloric heat pumps of competitive system performance.

Heat pumps (HPs) are seen as an increasingly important technology able to contribute significantly towards the decarbonisation of the domestic stock in the UK. However, there appears to be a performance gap between predicted and real-life HP performance, with several studies highlighting the need to include the HP’s interaction with users when examining their performance. This study examines the role of user behaviour in mitigating this performance gap from a systems perspective. A sample of 21 case studies was selected from 700 domestic HPs monitored across the UK via the government’s Renewable Heat Premium Payment Scheme for the collection of qualitative and quantitative socio-technical data. The application of systems thinking facilitated the identification of the underlying interactions between the HP system and its users. The systems analysis revealed that HP performance relies on complex socio-technical system interactions, including behavioural patterns, and that enabling feedback information processes can have a significant impact on user behaviour. The study enabled a deeper perspective on performance influencers relating to behavioural patterns and achieved new insights into the requirements for well-performing HPs. These findings have important implications for policy makers, installers and manufacturers of HP systems and their users.

In recent years, due to the rapidly growing global energy crisis and the ever-increasing prices of energy carriers, more attention has been paid to the energy efficiency of existing buildings, especially in the context of reducing harmful emissions and lowering heating costs. The purpose of this study was to analyse the influence of selected factors on heating costs and air pollution in a cold climate based on the example of a service building located in Bialystok, Poland. The following scenarios were assumed: the implementation of a heating schedule, improvement of the thermal insulation of the building envelope, lowering of the indoor temperature in all rooms, and moving away from a traditional heat source (gas boiler) to renewable energy (heat pump). The results showed that improvements in heat transfer coefficients had the greatest impact on reducing heating costs and that emissions from renewable energy sources depend largely on the national energy mix.

Waarom en hoe kunnen we warmtepompen besturen om flexibilitiet te krijgen.

Orientadores: Luis Augusto Barbosa Cortez, Clement Vigneault Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agricola Resumo: O tomate destinado tanto ao consumo de mesa, in natura, quanto à produção industrial, é uma hortaliça consumida o ano inteiro, sendo o Brasil um grande produtor, nas regiões Centro Sul e em algumas regiões do Nordeste e Sul do país. Mas as perdas pós-colheita superam 50 % durante o processo de colheita e de pós-colheita. Estas perdas são principalmente de tipos mecânica, fisiológica ou patológica. Portanto a utilização de uma tecnologia apropriada, como neste caso a concepção de um sistema de bomba de calor água/água em cascata, permitirá reduzir consideravelmente as perdas da pós-colheita dos tomates. Utilizando o sistema em conjunto, circuito de baixa e alta pressão na produção de água gelada (2°C) e quente (90°C), pode ser aproveitado para realizar as operações de resfriamento rápido por água gelada por aspersão, tipo chuveiro para tomates em estado de maturação verde maduro antes da embalagem para seu transporte em sistemas refrigerados para os mercados de comercialização em condições de qualidade exigida pelo consumidor. Ao mesmo tempo com a utilização do lado de alta pressão (alta temperatura) do sistema em estudo será possível a produção de uma fonte quente para atingir temperaturas (60 e 75°C) programadas no secador de bandejas e assim realizar a operação de secagem de tomates, previamente pré-tratados (redução de tamanho e eliminação de sementes) com fins de obter uma melhor transferência de calor no produto, e com a conseqüente eliminação de grande quantidade de água contida, reduzindo seu peso e volume, permitindo melhor conservação por tempo mais prolongado, fácil transporte e econômico. Para a determinação do melhor desempenho do sistema de bomba de calor indicado, foram realizados ensaios com a finalidade de encontrar o fluido refrigerante que atinja o melhor coeficiente de performance no ciclo de baixa e alta pressão, em base na melhor capacidade de trabalho na temperatura (abaixo de 0°C) de evaporação e condensação (perto de 90°C), e também com considerações de custo - beneficio. Assim foram testados os fluidos refrigerantes como o MP39, o R22, o R600 e R600a. O R22 mostrou melhor eficiência no circuito de baixa pressão, enquanto que o R600 teve melhor performance no circuito termodinâmico de alta pressão. Depois da escolha do melhor fluido refrigerante, se realizou a operação de resfriamento dos tomates, utilizando o sistema desenvolvido, onde o produto resfriado teve os mesmos resultados quando resfriado em outro sistema de bomba de calor convencional. Realizada a operação de secagem de tomates pré-tratados no sistema de bomba de calor, mostrou-se que o secador de bandejas operando com uma fonte de calor produzida pelo circuito da alta pressão ou de alta temperatura, atingiram-se as características de um produto seco em secador de bandejas com fonte de calor aquecida por resistência elétrica. Com estes resultados os objetivos planejados foram atingidos, mostrando a redução de consumo de energia no resfriamento e secagem de tomates (30%) e com boa qualidade de sabor, cor e umidade no produto final que o consumidor aceitaria. O sistema seria de muita utilidade para os produtores e distribuidores de tomates no Brasil Abstract: Tomato fruits are destined for consumption all around the year either in their natural form or as industrial product. Brazil is one the largest producers of tomato and its production is mainly located in the Center South regions and some northeast regions the country. Brazil also faces postharvest losses surpassing 50% of the production. The origin of these losses is mainly from mechanical, physiological or pathological injuries. The use of appropriate technologies, in the present case, the conception of an in-cascade water to water heat pump system could allow considerably reducing these losses. The system presented is and inset low and high pressure cycles to generate simultaneously cold and warm water to meet the requirement of fast cooling and drying system. The low pressure cycle generate the cold water for an aspersion hydrocooling system to cool down tomato fruits before being transported and commercialized to meet the increasing demand of the consumer for produce of high quality. At the same time, the high-pressure and high temperature cycle of the system produce heat stored in a form of hot water to produce air at the required temperature for drying tomato fruits previously cut and eliminating seed to eliminate a large amount of water contained in the produce, thus by reducing the weight and volume. Such dried tomato fruits better allow more time to be commercialized and used generating better economic returns and easier transportation. For obtaining optimum performance of the heat pump system, testes were carried out to determine the best cooling fluid, reaching the maximum coefficient of performance (COP). The R22 showed the best efficiency in the cycle of low pressure, while the R600 had better performance in the high-pressure thermodynamic cycle. Using these two fluid, the developed system was operated for cooling tomatoes and showed the same the results than conventional cooler but with better COP. Drying tomato operation using this incascade heat pump system revealed that the batch drier operating with the high-pressure or high temperature heat source cycle produced the same characteristics of dry product than drying batches of tomato fruits with electric resistance heat source. With these results the present objectives were reached, showing an important reduction of energy required for cooling and drying tomato fruits simultaneously and producing of good quality food, a product that the eventual consumer would accept. This system will be of much utility for the producers and processors of tomato in the entire Brazil Doutorado Tecnologia Pós-Colheita Doutor em Engenharia Agrícola

Orientador: Luis Augusto Barbosa Cortez Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica Resumo: O leite é um dos mais importantes produtos da agropecuária nacional, com cerca de 2/3 das propriedades rurais do país destinando-se à pecuária leiteira e com um dos maiores rebanhos do mundo. Apesar da grandiosidade, o setor ainda sofre com a baixa produtividade, os altos custos e a defasagem tecnológica. Como conseqüência, muitos produtores abandonaram suas atividades diante deste novo cenário competitivo. Atualmente, assuntos como uso racional de energia e aplicação intensiva de tecnologia tem sido intensamente discutidos e abordados, e indicados como aspectos importantes para a obtenção de ganhos de produtividade. Desta forma, visou-se neste trabalho avaliar o uso de energia no processamento de leite de três propriedades (leite pasteurizado tipo ¿A¿ e leite cru refrigerado), bem como, a representatividade dos diversos processos no consumo total, assunto este, ainda pouco conhecido e abordado no país. Objetivando ainda, promover a racionalização energética, avaliaram-se os potenciais de aproveitamento de calor de condensação de sistemas de refrigeração existentes para o aquecimento de água de limpeza e higienização, bem como, avaliou-se a viabilidade técnica e econômica da adequação dos sistemas (operação segundo um bomba de calor com geração simultânea de duas fontes térmicas) em substituição ao uso de resistências elétricas. Dentre as proposta, avaliou-se a adequação realizada em um planta piloto em operação. Com o uso de bomba de calor, a redução no consumo total de energia elétrica foi de até 15% com tempos de retorno dos investimentos variando entre 1,3 e 3,7 anos Abstract: Milk is one of the most important products of Brazilian agriculture, with about 2/3 of the rural properties dedicated to the milkmaid cattle breeding and with one of the largest flocks of the world. In spite of its size, the sector still suffers of low productivity, high costs and tecnological delay. As a consequence, many producers have abandoned its activities before this new competitive technology were introduced. Now, subjects as, the use rational of energy and intensive application of technology has been discussed intensely resulting in productivity gains. In this work , it was seek to evaluate the use of energy for milk processing in three different properties (pasteurized milk type " A " and refrigerated raw milk). It was also evaluated how representativive the several processes in the total consumption were, a problem, still not very well-known and trated in Brazil. To promote the energy rationalization, the potential use of condensation heat of refrigeration systems was evaluated for the cleaning water heating, as well as, the technical and economic viability of the adaptation of the systems was evaluated (operation according to a heat pump with simultaneous generation of cold and heat) in substitution to the use of electric resistances. In the midst of proposals, an adaptation was evaluated in a pilot plant in operation. With the use of heat pumps, there was a decreasing of 15% in the consumption of eletric energy with payback between 1,3 and 3,7 years Mestrado Mestre em Engenharia Mecânica

Presentatie van de resultaten van de 'Nul op de Trafo' project.

The smart grid paradigm and development of smart meters has led to availability of large volumes of data. This data is expected to assist in power system planning/operation and the transition from passive to active electricity users. With recent advances in machine learning, this data can be used to learn system dynamics. This paper explores two model-free reinforcement learning (RL) techniques - policy iteration (PI) and fitted Q-iteration (FQI) for scheduling the operation of flexibility providers - battery and heat pump in a residential microgrid. The proposed algorithms are data-driven and can be easily generalized to fit the control of any flexibility provider without requiring expert knowledge to build a detailed model of the flexibility provider and/or microgrid. The algorithms are tested in multi-agent collaborative and single agent stochastic microgrid settings - with the uncertainty due to lack of knowledge on future electricity consumption patterns and photovoltaic production. Simulation results show that PI outperforms FQI with a 7.2% increase in photovoltaic self-consumption in the multi-agent setting and a 3.7% increase in the single agent setting. Both RL algorithms perform better than a rule-based controller, and compete with a model-based optimal controller, and are thus, a valuable alternative to model- and rule- based controllers. ispartof: IET Smart Grid vol:3 issue:1 pages:1-11 status: published

Replacement of fossil fuel-fired boilers for generation of high-temperature water and steam is of paramount importance for reaching a fossil-free economy. Heat pumps could be possible substitutes, but the presently marketed solutions are mainly limited to low-temperature applications. This paper compares the thermodynamic performance of various High-Temperature Heat Pumps (HTHP) based on the vapor compression cycle with natural gas boilers for assessing their technical feasibility and competitiveness as future replacements. Different cycle configurations and natural refrigerants were compared based on the coefficient of system performance and exergetic efficiency. Moreover, the technical feasibility of the most interesting cycles was discussed based on current technologies. The results showed that HTHP are promising substitutes for gas boilers for heat production of temperatures up to 180 °C. In particular, ammonia cycles were preferable for source and sink temperatures lower than 60 °C and 110 °C, respectively, while water was a better-working fluid at higher temperatures. The complete exergy analysis showed different behaviors for various natural refrigerants in the working domain but confirmed the results identified by the energy analysis. In any case, the technological analysis showed that further improvement of compressor technologies is required for making these solutions competitive.

This paper discusses different decarbonisation scenarios for an existing district heating (DH) network supplied by coal-fired combined heat and power plants in Germany. Integrating higher shares of renewable heat is indispensable in reaching the climate goal and CO2 emission reduction targets. The study analyses the technical and economic aspects of integrating various technologies such as solar thermal, biomass boilers, waste incineration plant and heat pumps into the existing DH network, with the main focus on large-scale heat pumps. The approach consists of two main steps. First, we forecast future heat demand and the potential to extend the DH system by simulating the evolution and energy consumption of the city's building stock. Second, we use a supply dispatch model with hourly resolution to calculate alternative scenarios and sensitivities for the supply mix with a focus on heat pumps. Our results show that, under the current regulatory and economic framework, large-scale heat pumps are not cost competitive with the existing coal-fired CHP units. However, redesigning the regulatory framework and optimising heat pump design and operation could achieve cost parity. The CO2 price induced by the EU emissions trading scheme will most likely not be a sufficient incentive in short and medium term.

Exergy is a thermodynamic concept that allows us to articulate what is consumed and where it occurs in a working system. This paper provides an overview of the present state‐of‐the‐art of exergy research done by the author over the last 3 decades. In this paper, first, a brief introduction of warm and cool exergy concepts as quantities of state and flow, which can be rationally derived from the 2 fundamental laws of thermodynamics, is presented. Then, 3 typical applications are demonstrated: (a) exergetic evaluation of window systems with shading devices; (b) human body exergy analysis for summer seasons; and (c) exergetic evaluation of a heat‐pump system. Thorough and connective thinking with the concept of exergy helps us understand the essential points in environmental planning and design of the built environment.

The fundamental understanding of the thermal–hydraulic performance of working fluids during condensation is important for the optimal design of the condenser in various thermodynamic cycles. This paper is aimed at obtaining flow condensation heat transfer and pressure drop characteristics in a plate heat exchanger during the working conditions of the condenser of either organic Rankine cycle power systems or heat pump units. The selected working fluids are two hydrofluorocarbons, R134a and R245fa, as well as their hydrofluoroolefin replacements, R1234ze(E) and R1233zd(E). Measurements of heat transfer coefficients and pressure drops were carried out with varying saturation temperature, mass flux, and liquid Reynolds number, ranging from 30 °C to 70 °C, 16 kg/m2s to 90 kg/m2s and 65 to 877, respectively. Based on commonly used existing correlations, new heat transfer and pressure drop correlations were developed, including the effect of the surface tension. The experimental data indicate that different heat transfer mechanisms occur at low liquid Reynolds number with the different working fluids. The results suggest higher heat transfer coefficients and pressure drops for R1234ze(E) and R1233zd(E) than for R134a and R245fa at the same working conditions. The new correlations enable significantly better prediction accuracies for the experimental results in this study than existing correlations, indicating that the surface tension is a suitable parameter to consider in mini and micro-scale condensation heat transfer.

Shifting from heating using fossil fuel combustion to electrified heating, dominated by heat pumps, is central to many countries’ decarbonisation strategy. The consequent increase in electricity demand, combined with that from electric vehicles, and the shift from non-renewable to renewable generation requires increased demand flexibility to support system operation. Demand side response through interrupting heating during peak demands has been widely proposed and simulation modelling has been used to determine the technical potential. This paper proposes an empirical approach to quantifying a building’s potential to operate flexibly, presenting a metric based on measured temperature drop in a dwelling under standard conditions after heating is switched off, using smart meter and internal temperature data. A result was derived for 96% of 193 homes within a test dataset, mean temperature drop of 1.5 °C in 3 h at 15 °C inside-outside temperature differential. An empirical flexibility metric may support decision making and decarbonisation. For households it may support the transition to heat pumps, enabling time of use costs and tariffs to be better understood and system to be specified by installers. Electricity system stakeholders, such as aggregators and DNOs may use it to identify the potential for demand response, managing local networks, infrastructure and aggregation.