Photovoltaic systems and heat pumps installations are increasing faster than ever before in Finland. Load regulation is becoming a hot topic in the PV market. With load regulation, the self-consumption can be increased, and the user may earn money. An air-to-water heat pump can be regulated with own produced electricity from a PV system by overheating the tank. A typical single-family house of 150 m2 is simulated in Polysun for one year. The house has a photovoltaic system of 5.76 kW and an air-to-water heat pump with a tank of 180 l. The heat pump is used for space heating and domestic hot water. It is located in Helsinki, Finland. This work aims to compare two different control strategies for the heat pump.The first control strategy is based on the power output from the photovoltaic system and the second control strategy also takes the electricity consumption of the house into account. Both control strategies overcharge the tank with the heat pump to its maximum temperature of 65°C. Key figures such as self-consumption of photovoltaic system, annual electricity savings, payback time of regulation components and the performance of the heat pump are evaluated. The investment of a control system for overcharging is economically feasible, and the selfconsumption of the photovoltaic system has been increased due to overcharging.Economical savings has been made annually and mostly during Summer. The performance of the heat pump has decreased slightly with overcharging.

Ethyl alcohol (ethanol) as secondary fluids is very popular as heat transfer fluid for indirect refrigeration system with ground source heat pump systems (GSHP) in several countries such as Sweden, Norway, Switzerland, Finland and other European countries. There have been several researches about the future ofthe refrigeration sector, refrigerants and refrigeration systems. Moreover, strict regulations such as F-gasregulation and Kigali Amendment forcing a phase down of many current widely used high global warming potential (GWP) refrigerants, i.e. R134a or R410A. Therefore, secondary refrigeration systems and their working fluids are expected to play a key role in order to minimize the refrigerant charge in the systems, reduce the indirect refrigerant leakages as well as increase the safety during operation. The aim of this thesis is to investigate the effect different additives to increase the flame point together with ethanol-based secondary fluids and validate their thermophysical properties by comparing them with reference values for pure ethanol water solutions. The study aims to design a new commercial ethyl alcohol-based product for GSHP system that could replace existing ones in the Swedish market and could workwith natural or flammable low GWP refrigerants. Different high flash point additives were tested such as 1-propyl alcohol, n-butyl alcohol, glycerol andpropylene carbonate. Thermophysical properties were investigated and a GSHP model in Excel was created in order to assess the energy performance of the resulted blends. After screening different blends and assessing the energy performance, glycerol as additive in low concentration seems to be the future for the ethyl alcohol-based secondary fluids because of its high flashpoint (160ºC) that will reduce the flammability risk associated to ethyl alcohol blends, the low viscosity (by 12% lower compared to pure ethyl alcohol blends) that help reduce pumping power by 4.5% compared topure ethyl alcohol blends. Moreover, ethyl alcohol and glycerol blend showed the lost in heat transfer coefficient by 4% lower compared to pure ethyl alcohol blends due to lower thermal conductivity compared to pure ethyl alcohol blends. Finally, it is a rather cheap and natural product which has no problem related to corrosion since ethyl alcohol and glycerol are less corrosive than water. Although, flash point test was not conducted so there is no data regarding the flash point, it is expected the flash point is increased due to the high flash point of glycerol compared to ethyl alcohol or other possible additives. Therefore, it is expected that the flammability risk associated to ethyl alcohol-based secondary fluids is reduced. / Etylalkohol (etanol) som köldbärare är mycket populärt som värmeöverföringsvätska för indirekt kylsystemmed bergvärmepumpsystem (BVP) i Sverige, Norge, Schweiz, Finland och andra europeiska länder. Fleraundersökningar har gjorts om kylsektorns framtid, köldmedier och kylsystem. Dessutom strängaförordningar som F-gas förordning och Kigali- förordning tvingar en utfasning av många nuvarande allmäntanvända köldmedier med den höga globala uppvärmningspotentialen (GWP), dvs. R134a eller R410A. Därför förväntas det att kylsystem och deras köldbärare spela en nyckelroll för att minimera köldmediumsmängd i systemen, minska de indirekta köldmedieläckage och öka säkerheten under drift. Syftet med detta examensarbete är att undersöka effekten av olika tillsatser för att öka flammanpunkten tillsammans med etanolbaserade köldbärare och validera deras termofysikaliska egenskaper genom att jämföra dem med referensvärden för rena etanolvattenlösningar. Studien syftar till att utforma en nykommersiell etylalkoholbaserad produkt för BVP-system som skulle kunna ersätta befintliga produkter på den svenska marknaden och kan arbeta med naturliga eller brandfarliga köldmedier med låg GWP. Olika tillsatser med hög flampunkt testades såsom 1-propylalkohol, n-butylalkohol, glycerol och propylenkarbonat. Termofysikaliska egenskaper undersöktes och en BVP-modell i Excel skapades för att bedöma energiprestanda för olika blandningarna. De erhållna resultaten för olika blandningar visar att glycerol i en låg koncentration som tillsats kan vara framtidens additiv för de etylalkoholbaserade köldbärare på grund av dess höga flampunkt (160 ºC) som förmodligen kan minska brandrisken för etylalkoholblandningar. Dessutom hade glycerol och etanolblandningar den lägsta viskositeten (c.a.12% lägre jämfört med ren etylalkoholblandningar) som bidrar tillen minskning av pumpeffekten med c.a. 4,5% jämfört med rena etylalkoholblandningar. Däremot visade etylalkohol och glycerol blandningen c.a. 4% lägre värmeöverövergångstal jämfört med de rena etylalkoholblandningar på grund av lägre värmeledningsförmåga jämfört med ren etylalkoholblandningar. Slutligen är glycerol en ganska billig och naturlig produkt som inte har några korrosionsproblem eftersom etylalkohol och glycerol är mindre frätande än vatten. Även om flampunkttest inte genomfördes i projektet, förväntas det att flampunkten ökas lite på grund av den höga flampunkten av glycerol jämfört med etylalkohol och andra tillsatser. Därför förväntas det att brännbarhetsrisken förknippad med etylalkoholbaserade köldbärare reduceras.

The building sector account for 40 % of the global energy demand, and an increasingly popular way to supply buildings with heat is through the use of heat pumps. Solar thermal (ST) can either be used as a low temperature energy source in the heat pump or to directly supply the building’s heating demand.  The increasing market of PV has made it a favorite for roof-top solar installation. Its physical integration with buildings and HPs is simpler than that of ST and can supply any available electric load associated with the building and not just the HP system. It can also supply any excess power to the grid.  In order to properly compare these two options, key performance indicators (KPIs) were identified for several system boundaries within the building and HP system. Technical KPIs used were seasonal performance factor (SPF), solar fraction (SF) and self-consumption (SC), while internal rate of return (IRR), net present value (NPV), profitability index (PI) and payback time was used to evaluate their economic performance.  For the thesis a multi-family house was modelled in TRNSYS where different system sizes of either ST or PVs was simulated for a year with three-minute intervals. The ST was connected in a parallel configuration thereby supplying the building’s domestic hot water (DHW) through a separate storage tank. The modelled heat pump was a ground source heat pump (GSHP) which utilizes boreholes as the low temperature energy source. The SPF increased for both the ST and PV integration from the reference scenario (no PV/ST integration) but to a varying degree depending on the analyzed system boundary. The economic results suggested that PVs are the more financially sound option over ST for the simulated MFH. The sensitivity analysis also showed the large impact of economic assumptions on the expected profitability for both the PV and ST systems. Based on the results would the simulated MFH with an existing GSHP benefit more from installing PV instead of ST from both a technical, economic and environmental perspective.  It is reasonable that PVs will most likely be an integral part for future buildings in Sweden with or without HPs because of its financial strength and versatility of demand supply, especially compared to ST. / Byggsektorn står för 40% av det globala energibehovet, och ett alltmer populärt sätt att leverera värme till ett hus är genom användning av värmepumpar. Solvärmefångare kan antingen användas som en lågtemperaturenergikälla i värmepumpen eller för att direkt leverera byggnadens värmebehov.  Den ökande marknaden för solceller har gjort den till en favorit för takmonterad solinstallation. Dess fysiska integration med byggnader är enklare än solvärmefångare och kan leverera el till hea byggnaden och inte bara värmepumpssystemet. Solceller kan också leverera till elnätet om produktionen överstiger byggnadens behov. För att korrekt jämföra dessa två alternativ identifierades viktiga indikatorer för flera systemgränser inom byggnaden och värmepumpssystemet. Tekniska indikatorer som användes var årsvärmefaktor, solfraktion och självförbrukning, medan internränta, nuvärde, lönsamhetsindex och återbetalningstid användes för att utvärdera deras ekonomiska resultat. För uppsatsen modellerades ett flerbostadshus med tillgänglig takyta i TRNSYS där olika systemstorlekar (i kvadratmeter) av antingen solvärmefångare eller solceller var simulerade i ett år med tre minuters intervall. Solvärmefångaren var ansluten i en parallell konfiguration med värmepumpen, varigenom byggnadens varmvatten levereras genom en separat lagertank. Den modellerade värmepumpen var en bergvärmepump som utnyttjar borrhål som lågtemperaturenergikälla. Årsvärmefaktorn ökade för både solvärmefångar- och solcells-integrationen från referensscenariot (ingen solteknisk-integration) men i varierande grad, beroende på den analyserade systemgränsen. De ekonomiska resultaten visade att solceller är det mer ekonomiskt sunda alternativet över solvärmefångare för det simulerade flerbostadshuset. Känslighetsanalysen visade också på den stora effekten av ekonomiska antaganden på den förväntade lönsamheten för både solceller och solvärmefångare. Baserat på resultaten skulle det simulerade flerbostadshuset med en befintlig bergvärmepump dra nytta av att installera solceller istället för solvärmefångare från ett tekniskt, ekonomiskt och miljömässigt perspektiv. Det är troligt att solceller kommer vara en del i framtida byggnader i Sverige med eller utan värmepumpar på grund av den ekonomiska styrkan och möjligheten att tillgodose både byggnaden och elnätet vid överproduktion.

This work deals with the problem of choosing the correct heating curve for a certain building package (envelope plus distribution system). This topic is particularly relevant in countries like Sweden where heating curve is the most common way to control heat pumps. The analysis, involving four building models with respective distribution systems (two have floor heating and two radiators) and a variable speed GSHP, shows how, for a fixed location, the proper heating curve changes considering different building envelopes and different emitters. It is highlighted, therefore, how the adoption of a generic heating curve for all the buildings can cause discomfort and energy inefficiency. An algorithm to adjust the curve is then presented, and the results are compared with the reference case. The algorithm manages to improve comfort considerably and, for the A-class building, also SPF increases a lot (12.5%). The whole study was performed by means of TRNSYS® neglecting the DHW demand. / EffSys Expand P18: Smart Control Strategies for Heat Pump Systems

The aim of this study was to investigate the economic and energy-efficiency potentials for configuring thermal energy storage (TES) units in Swedish residential buildings. Consequently, the goal was to carry out economical and energy calculations over two applications of coupling two different types of heat pumps with a TES unit (water tank) for providing space heating in a detached single-family house in Stockholm, Sweden during winter time. The heating systems with the heat pumps and TES unit were modeled and simulated using the software MATLAB. Different criteria were applied to govern when the heat pumps would charge the TES unit, for example one criterion stated that the charging process would only occur if the electricity price was lower than a certain value. The results showed that there were savings both in terms of energy and economy for coupling a TES unit with a heat pump, for both types of heat pumps and regardless of criteria selection. The conclusions of the study is that there is potential for configuring TES units with heat pumps in detached single-family households in Sweden. However, since the models in this study included several simplifications, it is necessary to perform similar simulations with wider and more accurate models. / Energieffektivisering i byggnader är ett mycket aktuellt område i miljödiskussioner idag. Den totala energianvändningen i villor i Sverige 2014 motsvarade 31.2 TWh. Ett av forskningsområdena inom energieffektivisering i villor är värmelagringssystem (thermal energy storage systems, TES). Med TES kan man lagra energi och således uppstår möjligheten att frikoppla energianvändningen från energiproduktionen. Det finns olika typer av lagringsmetoder men denna rapport fokuserade på sensibel värmelagring i form av en tank, med vatten som lagringsmedium, kopplad till en värmepump. Syftet var att undersöka både ekonomisk- och energipotential för att konfigurera TES-enheter i fristående svenska villor. Således var målet att utföra beräkningar för ekonomiska- och energibesparingar för de två olika typer av värmepumpar kopplade med TES-enheten som tillgodoser värmebehovet för en fristående villa i Sverige under en vintervecka i februari. Värmebehovet för hushållet räknades fram timvis för den vecka som studerades. Utifrån detta behov bestämdes värmepumpens uteffekt per dag. För timmar där effekten producerad av värmepumpen översteg värmebehovet laddades TES-enheten för senare användning vid timmar med värmebehov som översteg effekten producerad av värmepumpen. TES-enheten som var en vattentank dimensionerades utefter det största värmebehovet under  veckan. De två värmesystemskonfigurationer presenterades som case A och B, där case A inkluderade en TES-enhet kopplad med en bergvärmepump med ett konstant COP-värde och case B en luftvattenvärmepump med ett varierande COP-värde kopplad med en TES-enhet. För att kunna utföra beräkningar användes datorprogrammet MATLAB, där olika kriterier styrde hur värmepumparna laddade TES-enheten. Båda casen undersöktes med och utan hänsyn till ett elektricitet-prisvariationskriterium samt ett COP-variationskriterium för case B. Resultatet indikerade att för ett värmesystem med en TES-enhet kopplad till en värmepump finns både ekonomisk-och energibesparing. Besparingarna varierade beroende på typ av värmepump och kriterier som togs till hänsyn. Men oavsett typen av värmesystem och kriterier fanns det besparingspotential. Slutsatserna är att det finns potential att implementera TES-enheter med värmepump i fristående svenska villor men att det behövs undersökningar med noggrannare modeller för att erhålla ett mer ackurat resultat. Detta då flera förenklingar och antaganden har gjorts i denna studie.

The global demand for heat as the primary source of final energy underscores the urgency of decarbonizing the heating sector to foster sustainability. Heat pumps are crucial in achieving sustainability, particularly in district heating applications, offering efficient centralized heating solutions. However, certain refrigerants used in heat pumps have environmental implications, prompting the European Union to introduce the F-Gas Regulation and PFAS Ban proposal to phase out harmful options. This study focuses on performance analyses of natural and synthetic refrigerant options applicable to heat pump systems with a heating capacity of 10 MW and above in district heating applications. Comparative evaluations were conducted under five distinct boundary conditions, using R134a as the current refrigerant. Moreover, to understand performance variations caused by seasonal temperature changes, additional general boundary conditions were introduced for further comparison. The research demonstrates that R717(Ammonia) performs best among the tested refrigerants, followed by R600a and R152a, with commendable results. However, performance alone is insufficient for refrigerant selection. Safety analysis revealed that despite its high performance, ammonia may not be a suitable choice due to its toxic nature. Thus, when considering performance, technological compatibility, and safety aspects, R152 or R600a refrigerants emerge as more appropriate options for these applications. The study highlights the importance of identifying environmentally friendly and efficient refrigerants for heat pump systems in district heating applications. By considering various performance scenarios and safety considerations, decision-makers can make informed choices to decarbonize the heating sector effectively, contributing to a more sustainable and eco-friendly world. / Den globala efterfrågan på värme som den primära källan till slutlig energi understryker vikten av att ta bort koldioxid från värmesektorn för att främja hållbarhet. Värmepumpar är avgörande för att uppnå hållbarhet, särskilt i fjärrvärmeapplikationer, och erbjuder effektiva centraliserade värmelösningar. Vissa köldmedier som används i värmepumpar har dock miljökonsekvenser, vilket får EU att införa F-gasförordningen och PFAS-förbudsförslaget för att fasa ut skadliga alternativ. Denna studie fokuserar på prestandaanalyser av naturliga och syntetiska köldmediealternativ som är tillämpliga på värmepumpsystem med en värmekapacitet på 10 MW och mer i fjärrvärmeapplikationer. Jämförande utvärderingar utfördes under fem distinkta gränsförhållanden, med användning av R134a som aktuellt köldmedium. Dessutom, för att förstå prestandavariationer orsakade av säsongsbetonade temperaturförändringar, introducerades ytterligare allmänna randvillkor för ytterligare jämförelse. Forskningen visar att R717 (Ammoniak) presterar bäst bland de testade köldmedierna, följt av R600a och R152a, med lovvärda resultat. Enbart prestanda är dock otillräcklig för val av köldmedium. Säkerhetsanalys visade att trots dess höga prestanda kanske ammoniak inte är ett lämpligt val på grund av dess giftiga natur. Sålunda, när man överväger prestanda, teknisk kompatibilitet och säkerhetsaspekter, framstår R152 eller R600a som mer lämpliga alternativ för dessa applikationer. Studien belyser vikten av att identifiera miljövänliga och effektiva köldmedier för värmepumpsystem i fjärrvärmeapplikationer. Genom att överväga olika prestationsscenarier och säkerhetsöverväganden kan beslutsfattare göra välgrundade val för att minska koldioxidutsläppen från värmesektorn på ett effektivt sätt, vilket bidrar till en mer hållbar och miljövänlig värld.

<p>Air conditioning, space heating, and refrigeration account for approximately 40% of the electricity usage in the U.S. residential and commercial building sector. To improve energy utilization and reduce energy consumption in space conditioning applications, advanced heat pumping technologies are needed. The chemical looping heat pump (CLHP) is a promising thermodynamic cycle that has shown the potential to achieve a cooling coefficient of performance (COP_c) increase of over 20% relative to conventional vapor compression (VC) systems.</p> <p><br></p> <p>The overarching goal of this study is to evaluate the chemical looping heat pump concept for residential applications, including thermodynamic potential, as well as technical and economic feasibility before developing and deploying a pilot scale system. The evaluation process includes advanced thermodynamic modeling for better assessments of working fluids and systems, techno-economic analysis for initial cost assessment of the scaled-up system, and small-scale experiments for proof-of-concept.</p> <p><br></p> <p>A working fluid screening process was developed to identify suitable working substance pairs for CLHP systems. The key metrics for evaluating the working fluids are associated with the possibility of phase change after a chemical reaction, reversible cell potential and power consumption, and cooling capacity of the system. Such metrics were applied to several fluids to assess their suitability. It was found that isopropanol/acetone working substances showed the highest cooling capability for a given power consumption. Even though this approach was applied to particular organic fluids (e.g., alcohols and ketones), this analysis can be generalized to other single-component fluids, multi-component fluids, and several chemical designs.</p> <p><br></p> <p>A modeling framework to estimate operating cost, capital cost, and levelized cost of energy was developed to enable a direct early-stage comparison of a CLHP with conventional VC systems. The models were helpful in understanding the influence of key factors such as efficiency, unit utilization (annual cooling and heating delivered, kWh_t/yr), and price of electricity ($/kWh_e) with the goal of determining target markets for initial CLHP products. The LCOE of CLHP could be less than that of VC in the case of high utilization (≥  20,000 kWh_t) with high performance improvements (COP_CLHP/COP_VC = 1.3) even though the capital cost of the CLHP is nearly 1.5-2 times higher than VC.</p> <p><br></p> <p>The key process of a CLHP cycle, which is electrochemically driven phase transformation, was experimentally demonstrated based on the advanced test rig and electrochemical cell. A polymer electrolyte membrane flow cell with a self-fabricated membrane electrode assembly and flow channels was employed to drive the reaction. The breakdown voltage analysis indicates that ohmic and mass transfer overpotentials account for more than 90% irreversibilities of the reactions. In addition, the results showed the possibility of phase transition of 20-30% at current density of ~0.003 A/cm² and the cell voltage of 0.025 V. The extent of a chemical reaction can be further improved by increasing the current and reducing the flow rate.</p> <p><br></p> <p>A semi-empirical cycle model was leveraged to predict realistic system performance. The model includes an electrochemical cell model with other component models in a CLHP cycle. The Second law efficiency was 50% of the Carnot limit with a cooling capacity of 2.24 mW (cooling density of 1.6 W/m²) at sink temperature of 40 °C  and source temperature of 23 °C. The cause for the precipitous drop in COP_c with increasing current density was overpotential, which requires further research on the optimization of membrane and catalytic materials as well as a geometry of flow channels to minimize the losses. Higher efficiency can theoretically be achieved at an elevated fluid temperature as long as an electrochemical cell can achieve a greater degree of conversion.</p> <p><br></p> <p>There are several challenges that should be reconciled in a future operational device and cycle at scale. Additional research on both material- and system-level performance is indispensable to meet practical size requirements. Nevertheless, this study is intriguing in terms of the possibility of developing a high efficiency device with the ability to use more environmentally friendly working fluids. Broadly, this CLHP research can contribute to accelerating the development of the newly emerging field, which is thermal systems coupled with electrochemical processes, that can maximize system efficiency using low-GWP fluids.</p>

This thesis considers the problem of implementation of Model Predictive Control (MPC) strategies in the general area of Heating, Ventilation, Air Conditioning (HVAC). Specifically, the contributions utilize the constraint handling and optimality properties of MPC to achieve energy efficient control of many different HVAC systems. First, the thesis focuses on a linear offset-free MPC design for a vapor compression cycle. The key contributions include a a sequential tuning method and application to a detailed simulation test-bed, demonstrating superior closed-loop results to that of traditional control strategies in the presence of both disturbances and measurement noise. Next, a modified linear offset-free MPC formulation is implemented on a heat pump. The key contribution is the formulation of an optimization problem that recognizes the tradeoff between energy conservation and tracking performance. Simulation results illustrate superior performances as measured through three separate metrics: safety, energy efficiency and tracking. The implementation of MPC formulations to these realistic problems also pointed to a lack of MPC formulations with explicit performance considerations in the control design. Thus, in the final part of the thesis, these observed shortcomings in the standard offset-free linear MPC design are addressed via a new performance specification-based MPC. Desired closed-loop output response is specified and achieved through a tiered optimization formulation that can handle plant model mismatch. Superior closed-loop response, in terms of desired transient behavior and disturbance rejection, relative to standard linear-based and offset-free MPC designs is achieved. Finally, directions for future work are discussed. / Thesis / Doctor of Philosophy (PhD)

This work aims to investigate the potential electricity savings, as well as the potential decrease in LCoH and OPEX, that an integration of an industrial heat pump can have on a molten salt-based power-to-heat system with integrated thermal energy storage. The original system uses an electric heater to heat up molten salt, which acts as the heat transfer fluid of the system, from which heated steam can be produced and delivered at the output. The idea of integrating an industrial heat pump into this power-to-heat system is that it would heat up the molten salt for a certain temperature range in the beginning of the heating phase, while the electric heater would be used for the later part of the heating phase of the molten salt.  First, a background section is presented in order to provide background information about the topic at hand, primarily focusing on heat pump theory and avaliable process- and waste heat that could be used by an industrial heat pump. After that, a system configutaion is presented of the investigated power-to-heat system with all the components in it thoroughly explained. The methodology followed throughout this work is then presented, which includes the description of a mixed-integer linear program that is of fundamental importance in relations to this work, and used for conducting simulations from which much of the results is derived from.  When using a waste heat tempreture of 100°C and a sink temprerature of 250°C for the industrial heat pump, results show that the electrical power used in the system without an industrial heat pump can be decreased by 15,6%. Moreover, a maximum decrease of 13,4% of the LCoH and 16,6% of the OPEX can be achieved by the integration of the industrial heat pump. The biggest decrease, in regard to the LCoH and the OPEX, were for the countries with the highest average electricity prices, while a smaller decrease was shown for the countries with lower average electricity prices.  A cost increase for the industrial heat pump, which would affect the CAPEX of the system, was shown to have a small outcome for the LCoH savings, the major contributor was the OPEX of the system. If any impactful change for this particular power-to-heat system is desired, it's going to have to decrease the OPEX for best result, which is what the integration of an industrial heat pump aims at doing.

No description available.