With the adoption of the Paris Agreement, 196 countries worldwide committed to the limitation of the global temperature rise. In order to achieve this goal more energy needs to be produced in a sustainable way. However, the industrial sector is still mainly fossil driven and therefore has to adapt to be able to utilize sustainable produced power, which most often is in the form of electricity. More than a quarter of the total heating demand is in the 100 ◦C to 200 ◦C range. In this temperature range heat pumps are a strong alternative to fossil fuels. Heat pumps can absorb energy from a low temperature heat source and deliver it at a higher, usable temperature. Various technologies for waste heat recovery were investigated in this thesis. It was identified that existing heat pump technologies are suitable to upgrade waste heat, but are limited to lower temperatures of around 120 ◦C. This limitation is mostly due to the high compressor discharge temperatures, which degrade the lubrication oil. Compression resorption heat pumps utilizing wet compression (CRHP’s) limit the superheating during compression and are able to operate oil free, because the working fluid acts as a lubricant. This increases the achievable compressor discharge temperature. The wet compression however is not yet a mature technique and an isentropic efficiency of 70% is required to be competitive with existing technologies. Absorption cycles show promising results for upgrading waste heat due to their non-isothermal heat source and sink, which can be matched to the waste heat temperature. At the Process and Energy lab experiments have been performed on a wet compressor using an ammonia water mixture. This thesis proposes a new method of analysing existing experimental data through a cycle energy balance model. In order to create a model of the experimental setup, four limitations of the setup were identified. First the influence of the gap seal flow, which is the flow from the high pressure to the lower pressure side of the compressor. Second, the mixture inside the compressor can not be assumed homogeneous, which means that both phases are not in equilibrium. Third, there is cooling oil flowing through the compressor housing which cools the process side, this results in a non-adiabatic compression. Finally the pressure drop on the high pressure side is not measured, resulting in an error when calculating the composition of the working fluid. In order to model these limitations a model of the experimental setup was created in Aspen Plus. This model was supplemented with Matlab code to account for the non-equilibrium compression as well as the pressure drop and gap seal flow. Empirical relations were used to determine the heat and mass transfer between the phases during compression. The isentropic efficiency of the modelled compressor was varied until the output matches the input indicating that the steady state solution has been found. The influence of the non-adiabatic compression and the gap seal flow seem to have a significant impact on compressor performance. It was found that the compressor has the highest volumetric and isentropic efficiency when the inlet vapor quality is around 0.85 and the performance decreases with higher vapor qualities. Isentropic efficiencies of up to 0.88 were calculated. The results were compared against previous analysis of the same experimental data which used different assumptions and did not consider the whole cycle. Finally, a case study was performed to analyse the applicability of heat pump technology to upgrade waste heat in a paper recycling plant. A conventional vapor compression heat pump (VCHP) and an electric boiler were compared to a CRHP. To deal with the uncertainty of wet compression performance a range of isentropic efficiencies were considered as well as different ammonia concentrations. The CRHP proved to be energetically and economically viable and outperformed both the VCHP and electric boiler in this case study.

Industrial refrigeration systems are known to consume approximately 17% of electrical energy, a figure that is projected to rise in the future. This high energy consumption contributes to global warming and environmental degradation since conventional sources of energy are typically utilized for electricity generation. Moreover, the energy-intensive nature of industrial refrigeration systems leads to increased costs for major food and beverage industries. Consequently, optimizing the energy efficiency of these systems becomes crucial.
In this research, the application of Digital Twin (DT) technologies was explored, which have demonstrated effectiveness in various areas such as supply chain streamlining and system optimization. By combining physical and virtual spaces, DT and big data analytics can facilitate energy performance evaluation and optimization. The literature review identified three categories of DT models: physics-based, empirical, and data-driven. Considering their accuracy and efficiency, empirical models were recommended for developing DT models, while data-driven models proved useful for performance prediction applications. It was recommended to establish empirical equations based on correlation analysis by adjusting higher degree terms for accuracy. Additionally, input-output parameters for the DT should be tailored to the specific application and equipment. The literature study showed the possible identification of energy performance deviations, their root causes, and potential optimizations, including equipment optimization, load sharing among parallel equipment, and optimization of condenser set points and defrosting time.
This thesis research focuses on three industrial refrigeration plants: the Verkade Plant, the LST Plant, and the GIST Plant. For the Verkade Plant, empirical models were developed and validated for the screw compressor, evaporator, and evaporative condenser. An algorithm for condenser optimization was proposed and tested, while deviations in evaporator performance were analyzed. Similar models were developed and validated for the LST and GIST Plants, enabling the prediction of equipment performance. The predicted results were compared to actual plant performance, and deviations were carefully examined. Furthermore, optimization techniques were applied to improve equipment efficiency.
The thesis research findings indicate that the empirical models for each equipment piece at the Verkade Plant achieved an accuracy within a 5% error range, suggesting their suitability for analyzing the other two plants. The proposed condenser optimization algorithm has the potential to annually save 7% of energy, resulting in savings of 32 MWh of electrical energy and 11 tonnes of CO2 emissions. The application of the proposed optimization techniques to the LST and GIST Plant resulted in a significant reduction in energy consumption. It was determined that these techniques can achieve savings of approximately 13% and 14% in total energy consumption, corresponding to 200 MWh and 170 MWh of electrical energy, as well as 70 tonnes and 60 tonnes of CO2 emissions, respectively. These energy savings contribute to the reduction of CO2 released into the atmosphere, aligning with the goals of the Paris Agreement. Consequently, this research offers valuable insights into mitigating global warming through the optimization of industrial refrigeration systems using DT technology.

Magnetocaloric heat pumps are those types of heat pumpswhich use a solidMagnetoCaloricMaterial (MCM) in place of a refrigerant to provide the work for the heat pump. MCMs are materials whose temperature changes on the application or removal of a magnetic field. This effect is known as the MagnetoCaloric Effect (MCE). Magnetocaloric heat pumps have the potential in replacing the conventional vapour compression technology for Dutch dwellings, since they have minimum environmental impact due to the absence of the coolant fluids that can harm the environment. A model of the regenerator of the magnetocaloric heat pump is developed in this project having in mind the application of this type of heat pumps to Dutch dwellings. The magnetic field that is used in the development of the model is 0.875 T, with permanent magnets being the source of the magnetic field. A sensitivity analysis is carried out in order to obtain the methods to optimize the regenerator for improving the performance of the heat pump. The performance of the heat pump is measured through its average cooling capacity, average heating capacity, temperature span and Coefficient of Performance (COP) for heating. TheMCM used for the regenerators is Gd with a totalmass of 1.18 kg. The parameter that influences the performance of the heat pump the most is the porosity of the regenerator. The heat losses through the casing have the least impact on the performance of the regenerator. The frequency of the cycle also has a profound impact on the heating capacity and cooling capacity up to temperature spans of around 18 K, but it does not have such an impact on the heating COP. After increasing the frequency, decreasing the particle diameter and decreasing the porosity, the heating capacity and the temperature span are optimized. For a temperature span of 15 K, the heating capacity is 164.2W, and for a temperature span of 20 K, the heating capacity is 99.1W.

On the island of Goeree-Overflakkee, local and regional municipalities, businesses and education and knowledge institutions are pursuing a pioneering project called H2GO. The H2GO project is a project that researches the role green hydrogen can fulfill in our society through eight different scalable sub-projects. One of these projects is making the local fishing fleet of Goeree-Overflakkee CO2 neutral. Due to technical limitations, adaptations to make the fishing vessels CO2 neutral will not be possible for the coming years. For the shorter term, the project is therefore also looking for different ways to make the fleet more sustainable. A substantial polluting factor for this type of fishing vessels is the refrigeration unit, used to cool the freshly caught fish. A technology, called thermally driven metal hydride cooling, shows potential to provide an alternative for the current refrigeration system. In this thesis, the technical feasibility is explored of replacing the conventional ice slurry machines that fishing vessels currently employ with this technology. In order to do this, a literature review on different types of metal hydrides and the state-of-the-art on metal hydride cooling systems has been conducted. After this, a numerical model is presented and validated with an equivalent model and experiments. The model shows good similarity regarding overall system performance compared to the experiments. Finally, a metal hydride cooling system, containing another low temperature metal hydride is proposed that is capable of achieving a cooling capacity of 16 kW at a cooling temperature of -10 to -20 ◦C. This leads to the conclusion that the system has some efficiency drawbacks, but that the metal hydride system is technically feasible for use in the fishing vessels at Goeree-Overflakkee. This, in return, reveals a significant opportunity for employing this new technology to lower the environmental impact of the Goeree-Overflakkee fishing fleet.

The global climate agreement signed in Paris in 2015 sets the goal of limiting global warming, which is essential of saving the planet for future generations. The energy transition from a fossil-fuel living to a sustainable society depends on the technological development of using the renewable energy sources on earth. Wind and solar are common energy sources, but more sustainable energy sources need to be used to achieve this fossil-free living. Ocean Thermal Energy Conversion (OTEC) uses the temperature gradient of the ocean for the generation of electricity to accelerate the energy transition. The OTEC cycle contains plate heat exchangers (PHEs) which are made from titanium for high heat transfer performance and to cope with corrosive fluids, like ammonia and seawater. However, titanium is expensive and replacement is needed to reduce costs and environmental impact [114]. Polymers, on the other hand, are cheaper and are corrosion-resistant, but heat transfer is poor. Heat transfer and pressure drop indicate the performance of PHEs and increasing heat transfer and lowering pressure drop will increase the efficiency of the entire system, thereby lowering the overall cost of energy produced. The performance of composite polymer plates in heat transfer applications is still unknown. The thermal conductivity is lower compared to metal plates, which has a significant effect on heat transfer [37]. In this thesis, a small 100WOTEC plant, constructed at the TU Delft, is used as experimental setup. The test section of the setup is the condenser of the OTEC cycle, which is a gasketed plate heat exchanger (GPHE). In the first part of this thesis, two types of composite polymers are investigated to determine the design requirements of polymer plates in PHEs. Sealing of the GPHE seems to be an issue due to the low ductility and compression strength of the composite polymers. The plates are not able to withstand the compressive force needed for sealing. Three types of seals are tested in this research: conventional rubber gasket, epoxy and rubber orings. Unfortunately, none of the seals achieved sealing. A new plate and gasket design has been proposed to be able to prevent plate failure and achieve sealing for the testing of composite polymer plates in a GPHE for future research. The second part of this research focuses on the validation of heat transfer and pressure drop correlations in a 2-channel stainless steel GPHE, with ammonia (NH3) as working fluid, developed by Tao [96]. The correlations are based on 20-80 kg/m2s mass flux range, which is the mass flow per flow passage area. The experimental research is conducted with two adjustments compared to the research by Tao: ammonia-water (NH3/H2O) as working fluid and 4-channels. Experiments are conducted at mass fluxes of 15, 20 and 30 kg/m2s with changing vapour qualities. The data is analysed and heat transfer coefficients (HTCs) and pressure drops are calculated using a data analysis model. HTCs and pressure drop results are compared with the correlations developed by Tao for validation. HTC results are low compared to the expected values based on previous work. This is likely due to the presence of fouling on the stainless steel plates, the presence of a non-condensable gas in the system and a maldistribution of the flow at the inlet of the GPHE, which causes an uneven distribution of liquid and vapour across the channels. As a consequence, the applicability of the heat transfer correlation by Tao for multi-channel NH3/H2O mixture at low mass fluxes is inconclusive. The pressure drop results seem to be less effected by the factors negatively influencing the HTCs. The pressure drop correlation by Tao underpredicts the obtained pressure drop results, which is possibly due to the change of working fluid: NH3/H2O mixture. However, the applicability of the frictional pressure drop correlation by Tao is inconclusive due to the maldistribution of the flow at the inlet of the GPHE. This concludes that the knowledge of the distribution of vapour and liquid across the channels in the GPHE is important during performance testing of a GPHE.

The purpose of this research is to find an alternative to the natural gas-fueled heating systems of dwellings for the neighborhood of Westenholte. Reasons for replacing this system include the high GHG emissions, resulting from the combustion product of natural gas (CO2), in addition to its greenhouse effect. As a solution to replace the GHG-intensive heating of dwellings, a district heating (DH) network is proposed. This heating system does not involve the vast amount of natural gas needed by the traditional system, leading to the desired reduction in CO2 emissions. However, constructing and using a DH network is considered a large investment, which might be higher in total cost in comparison to the traditional, CO2 emission intensive, heating system. Both the cost and CO2 emission of a new DH should be minimalized. Therefore, the following KPIs are selected for comparison of the DH network: CAPEX, OPEX, and LCOE to indicate the cost, as well as CO2 emission to indicate the difference in GHG emissions. The KPIs of the DH of Westenholte are then compared to a reference solution: a decentralized all-electric solution, which also stands largely independent of natural gas. These KPI of the DH of Westenholte are to be compared to a reference solution: a decentralized all-electric solution, which is also largely independent of natural gas. Two temperature regimes of the distribution temperature of the DH are calculated and optimized for the neighborhood of Westenholte. By using a lower temperature (50/30 °C) in comparison to the more conventional temperature (70/40 ° C), the KPIs could be improved. Lowering the distribution temperature could make the heat pumps more efficient, subsequently reducing the overall cost. Additionally, the DH can probably reduce the GHG emission and, at the same time, is cheaper by using multiple renewable heat sources. As the heat profile over time differs for all heat sources, using a combination of the energy sources is estimated to create a better match with the heat demand profile. This would reduce the required heat production, storage, and associated CO2 emission and cost. In this study, a DH network is divided into the different submodules – heat demand, supply, and coupling of demand and supply – and then modeled in Python. The heat demand submodule models the heat demand of the dwellings, including the domestic hot water (DHW). In the heat supply submodule, all the available thermal energy sources used are modeled: wastewater (TEWW), surface water (TESW), solar, and industrial waste (IWH). The coupling module then matches the demand and supply geographically, by modeling the distribution grid, and, in time, also by modeling the thermal energy storage. For the DH of Westenholte, the lowest LCOE of 0.15 € /kWh was found for a 70/40 °C DH combination of 25 percent IWH, 60 percent TEWW, and 15 percent TESW in addition to a peak supply, however, generating 34.67 ton/year CO2 emission. A DH network of 50/30 °C would provide the lowest CO2 emission, which would use 25 percent IWH and 75 percent solar thermal energy inducing a CO2 emission of 2.76 ton/year, nonetheless, requiring an LCOE of 0.40 e /kWh. In contrast to the all-electric reference scenario with an LCOE of 0.22 € /kWh and a CO2 emission of 49 ton/year, the LCOE-optimized scenario proved both cheaper and dissipating lower CO2 emissions.

Of the global energy demand, 20% can be allocated to residential energy demand. Most of this energy is produced by fossil fuels, which raises the importance of energy production in a more sustainable way. In order to do this on the level of residential heating applications, the Dutch government aims to make its residential neighborhoods natural gas-free. An often considered solution is making residential areas all-electric. However, when considering the heating of these households based on electricity, high peaks may occur in the electricity grid due to simultaneous heating at times of high demand. This could cause problems regarding the capacity of the electricity grid. Subsequently, the generation of electricity is nowadays associated with relatively high CO2 emissions, raising the awareness for alternative methods of heating. One of these methods is district heating coupled to (more) sustainable energy sources. A problem occurring with this combination is a possible discrepancy between the supply and demand of energy. Therefore, it could be beneficial to implement thermal energy storage in district heating. This research assesses the feasibility of different configurations of thermal energy storage integrated into district heating. For this research, a case study is conducted in which district heating for a residential area coupled with thermal energy storage is modeled. The model is based on the thermodynamic equilibrium of the network and is able to compute the required characteristics and key performance indicators of the district heating network. For the case study, multiple scenarios have been created which assess different distribution characteristics and heat sources. For reference, an all-electric scenario has been designed as well. The results of the case study show that the implementation of thermal energy storage in district heating is able to lower peak loads on the heat source by two-thirds. This implementation goes paired with an increase in levelized cost of energy of 10-16% and 8-73% higher CO2 emissions, compared to district heating without storage and depending on the characteristics of the district heating net and its heat source. However, for certain heat sources, the advantages of thermal energy storage outweigh the drawbacks or thermal energy storage might even be considered to be inevitable. This is especially the case for renewable heat sources, of which its share in the future energy market is considered to be substantial. Also, the results show that every scenario considering district heating performs better on levelized cost of energy and CO2 emissions than the all-electric scenario. When designing new DH projects, it is key that different available heat sources will be considered and that an accurate trade-off is made between the advantages and drawbacks of thermal energy storage. This research is based on the comparison of various scenarios for a case study. Therefore, it does not focus on finding the optimal parameters for either district heating or thermal energy storage. For finding these optimal parameters, future research must be conducted.

In the last decades, the excessive increase in average global temperature related to a massive rise in greenhouse gas emissions showed the world how the fossil fuel society we live in today is drastically modifying and destroying the world we live in and is turning it in an un-habitable planet. Scientist all over the world made it clear that if we stay on the current patterns and we don't reduce drastically our greenhouse gas emissions, we are gonna end up with the extinction of the human species. The urgency of the problem seems to be clear to most people, what we need now are immediate actions to drastically reduce our greenhouse gas emissions. Among all different sectors, the residential sector is one of the biggest contributors to greenhouse gases (GHG) emissions and most of the energy is used for space heating (SH) and electrical appliances. In the specific case of the Netherlands, most energy provided to the residential sector is produced by means of natural gas, and the goal of the country is to replace natural gas with net-zero CO2 solutions. In this thesis work, a solar-assisted ground-source heat pump (SAGSHP) system for space heating for a typical Dutch terraced house is thoroughly investigated. In particular a 115 m2 house with 3 people living in it. The main different components of the system are investigate by looking at the state-of-the-art technology to understand what are the different system components that would be more convenient to use in the Netherlands in terms of efficiency, costs, etc. After the different system components have been selected and a general layout of the system is determined, the different components are designed and modelled using Matlab or Simulink environment. Finally, the whole system is assembled together and simulated in a Simulink environment. The simulation runs over a period of one year using a simulation time step of 6 minutes (0.1 hours). In particular two different cases have been used for the simulation. The base case used is an year where the ambient conditions used (ambient temperature and irradiance intensity) are values averaged over a period of twenty years (1991-2020). The second case is the simulation of a very cold year to see how the system performs in extreme cases. The simulated year is the year 2010. The obtained results are presented and discussed to draw conclusions and future work recommendations. The final goal of this work is to understand the competitiveness of the system with respect to a traditional gas boiler in terms of CO2 emission reduction, performance and costs. From this work it was possible to conclude that the chosen SAGSHP system performs slightly better in colder climates where a higher heat load requirement is needed. From the base case study used in this work, it was concluded that the modelled SAGSHP system can achieve a system seasonal coefficient of performance (SSCOP) of about 3.8 and it can significantly reduce the amount of CO2 emissions generated, up to about 2.8 ton of CO2 every year. From an economical point of view, the system levelized cost of energy (LCOE) is still higher than the LCOE of a traditional gas boiler system due to the high initial investment associated with SAGSHP systems.

Compressors play an essential role in refrigeration. Recent industrial compressors are more efficient, less energy-demanding, and provide higher modularity than ever before. On the other hand, such innovation led to a higher degree of complexity of the equipment, which could undermine the reliability.Every compressor unit has sensors, programmable logic controller (PLC), and human-machine interaction (HMI) modules. The PLC can stop the equipment in case of danger, and the HMI displays the reason why the compressor stopped (e.g. high oil temperature).However, data from the sensors installed on the machinery can be used to obtain more insight to the status of the compressor. Less severe faults can be detected and diagnosed earlier, interrupting in advance the chain of events that leads to more expensive failures.GEA is one of the largest players in industrial refrigeration and produces different models of compressors, such as screw and piston compressors. The company performs maintenance services to their equipment located in different locations worldwide and they made available for this thesis multiple datasets of compressors experiencing different faulty behaviors. The aim of this project is to define methods of fault detection and diagnosis of faulty non-return valves, liquid refrigerant carryover in the compressor crankcase, and an investigation on faulty bearings.Different solutions about fault detection & diagnosis (FDD) in reciprocating compressors have been found in the literature. Among the proposed solutions, two rule-based methods have been developed for the leaking non-return valve. The same fault has then been detected by classifying the data with three supervised machine learning (ML) techniques: decision tree, random forest, and XGBoost. In the end, all the different models have been compared and their respective strengths and weaknesses analyzed. All the ML models showed an advantage in detecting the leaking in non-return valve compared to the rule-based models because the trend of such fault is not always predictable with a series of if-then-else rules.A similar approach has been used for the detection of liquid carryover in the compressor's crankcase. In this case, a rule-based model detected the fault accurately. This was due to the lower grade of complexity in detecting the symptoms of such fault. The ML models required a data augmentation step for the training dataset since the ratio between faulty and non-faulty data was too big. Two data augmentation methods have been used: random oversampling and synthetic minority over-sampling (SMOTE) technique.For the last study case, an investigation and detection of symptoms to detect faulty bearings has been performed. Multiple rule-based algorithms have been defined to detect the symptoms of such fault, while a model-based approach has been proposed to compare the measured power demand with the predicted power demand of GEA's proprietary compressor model.In conclusion, a hybrid approach, rule-based + ML, is the proposed method for the development of GEA's FDD program, since there is no outstanding method that fits all the possible faults. Based on the results of the models developed in this thesis, GEA can choose which algorithm is worth implementing in the FDD program embedded in their compressors.

Energy shortage and energy related environmental problems are urgent issues to be addressed in the coming years. Low-grade heat is utilized to drive energy conversion cycle and to produce electricity, which is a renewable and sustainable approach to energy supply. These thermodynamic cycles for energy conversion require eco-friendly working fluids and highly efficient heat transfer processes. NH3 is a natural refrigerant with superior thermal properties such as large latent heat and high thermal conductivity. However, the application of NH3 is restrained due to safety issues. Plate heat exchangers have the potential to be used in the thermal facility of NH3 for the recovery of low-grade heat. These compact structures are able to transfer large heat loads with reduced charge of working fluid, thereby mitigating the safety risk. For instance, the Organic Rankine Cycles of NH3 equipped with plate heat exchangers have smaller sizes compared with the plants filledwith other refrigerants. Furthermore, plate heat exchangers have the advantage of design flexibility and easy maintenance for highly efficient heat transfer, bringing aboutwide utilization in refrigeration, pharmacy and chemical engineering. In this thesis, NH3 condensation is experimentally and theoretically investigated in plate heat exchangers. The main aim is to provide design methods of compact plate condensers used in the thermal facility of NH3, which are not available in open literature. The experiments ofNH3 condensation have been reported, but no design method is provided. The heat transfer and frictional pressure drop correlations of hydrofluorocarbons (HFCs), hydrocarbons (HCs) and hydrofluoroolefins (HFOs) are assessed making use of an experimental database. Most suitable correlations are recommended.

Decarbonisation can be done through various routes: reducing the final energy consumption by improving process conditions and efficiency, reusing waste heat and by an outright energy transition to renewable sources. In this study, the focus is on reusing waste heat. Heat pumps have the potential to drastically reduce energy requirements in the industry and in that way reduce emissions (Kiss and Infante Ferreira, 2017). van de Bor et al. (2015) compared different heat pump technologies and for industrial applications where there is a temperature glide of the heat source and/or sink compression-resorption heat pumps (CRHP) utilizing wet compression can achieve a higher coefficient of performance (COP) than alternative technologies. However, an isentropic efficiency of 70% for the compressor was assumed. If this limit is not reached there might be no advantage of wet compression compared to the traditionally used vapour compression heat pump (VCHP) as pointed out by several authors (Itard and Machielsen (1994), and Zaytsev (2003)). This study consists of experimental and modelling aspects. The compressor model is experimentally validated in this thesis. Deep knowledge about relevant topics like wet compression, compressor specifications, thermodynamic and geometrical models is developed before starting off with the experiments. The experiments are carried out for four rotational speeds: 10320 rpm, 12910 rpm, 14205 rpm and 15500 rpm, taking system constraints into account. Two approaches are considered here: the homogeneous approach and the heterogeneous approach. In the homogeneous approach, the concentration of ammonia is constant across the compressor and the process medium is treated as a single entity. In the heterogeneous approach, an assumption is made: only the vapour is compressed whereas the liquid exchanges heat with the vapour leading to partial evaporation. The model developed is updated. The experimental and model results are then validated and conclusions are drawn.

This study aims to assess the role and need of (seasonal) thermal energy storage in the next generation renewable, and sustainable central heating systems for the built environment in the Netherlands. Specifically, the neighbourhood "Karwijhof" in the city Nagele which is transitioning to a collective renewable district heating network incorporating 24 users. The emphasis of this study lies on the technology for storing thermal energy and two different heat collection technologies. The storage of heat is done using an underground seasonal thermal energy storage (USTES), in this case an underground sensible heat storage tank using water as storage medium. The system relies on a small scale district heating network (DHN) for the distribution of heat. For this research two heat collection technologies are considered resulting in two systems to be compared, both incorporating the USTES as main system component. The first system relies on heat collection by solar thermal collectors, the second on an air-water heat pump. Both systems are modelled in the Matlab-Simulink software environment and back tested on historic (publicly available) weather data provided by the Royal Dutch meteorological institute (KNMI). Different system sizes are tested on their key performance indicators through an iterative process. System sizes depend on the capacity of the main components which include: volume of the USTES, surface area of the solar thermal collectors, and air-water heat pump capacity. Key performance indicators include the levelised cost of heat (LCOH) and the seasonal coefficient of performance of the system which gives an indication on the autonomy of the system. To increase the autonomy of the systems a photo-voltaic (PV) array is considered for both systems to offset the electricity use. However, the systems are allowed to exchange electricity with the grid translating into the goal of "zero on the meter" autonomy. The model results show a mismatch between heat demand and generation. Demand peaks during winter from December-March while generation peaks during the summer months May-August. The USTES is needed to overcome this mismatch and ensure access to heat throughout the year. The results show that both systems can ensure heat throughout the year for the users considered during this study. However, systems cannot compete with traditional natural gas heating systems based on the LCOH. This is partly due to the high cost of the district heating network. The systems including a PV array show a LCOH that can compete with the traditional natural gas HR-boiler but are constraint by the rooftop area available during this study leading to a non competitive LCOH. Though, even with enough rooftop area for a PV array the systems cannot pay them self back relative to the base scenario due to the financing costs. During the study no subsidies were taken into account. Subsidies will be needed to make the renewable energy systems presented in this study financially more attractive in the short term. When considering the environmental benefits it can be argued that the systems are already competitive to the traditional natural gas heating systems. Further studies should focus on efficiency gains in the district heating network and the control mechanism of the air-water heat pump. It is expected that the LCOH of systems as proposed in this study will decline in the future as a result of cost reductions and/or efficiency increases of the system components. Also, a lower LCOH is deemed achievable for neighbourhoods with simpler district heating networks (i.e. less meters of DHN piping per user).

The global energy demand is growing, while climate change is demanding a sustainable way of generating this energy. Ocean Thermal Energy Conversion (OTEC) can be a part of the solution for this problem. OTEC generates electricity by using the temperature difference between the surface water of the ocean and the water at 1000 meters depth as a driving force. As this temperature difference is present all year round, there is no need for energy storage, which is the case for wind- and solar energy. An OTEC system utilizes an Organic Rankine Cycle (ORC), which uses ammonia as a working fluid. A lot of research is conducted on this cycle, all assuming steady-state. However, as the system is constantly changing its state, either by a changing temperature difference or by variations in the operating conditions of components, more research is required to investigate the impact of these changes. Therefore, a dynamic model has been developed. In order to cope with these changes and to ensure the optimal power output at all times, a control strategy is developed and implemented on the model. As the system has been developed with the use of a control system as a boundary condition, a model is adapted which prioritises computational time over accuracy, but, according to literature, is still accurate enough for the small transients. This model has been implemented for the OTEC cycle and improved from normal dynamic models by including pressure drops and storage tanks. Allseas, in cooperation with the TU Delft, has built an experimental set-up of an OTEC cycle. Experiments conducted on this set-up were used to compare the model with reality, both steady-state and dynamically. It has been proven that the steady-state values matched the experiments within 1%, and the  dynamics matched the experiments almost perfectly. As a next step, the system has been scaled to match the desired 3MW output. With this scaled model, realistic scenarios were simulated to check the response on larger transients. The scenarios consists of a start-up and shutdown of the system, a changing inlet temperature, pumps being shut off and a number of heat exchangers that are decoupled from the system, for example when a number of heat exchangers need maintenance.  The outcome proved that, from a dynamic perspective, the influence of a seawater temperature change was negligible. As the temperature changes per second are very small, the net output scales linearly with the temperature difference. A start-up and shutdown of the system was successfully simulated, which is the largest possible transient in the system. The influence of pumps that are stopped and heat exchangers being turned off for maintenance have been simulated, which showed just a slight decrease in net output. It also showed that the system, when running at the nominal conditions of the pump and turbine curve, was not running at an optimum. Therefore, a control strategy was developed by conducting a sensitivity analysis and, after using an optimisation to find the optimum point, the resulting control strategy was implemented. This new strategy resulted in an increase of 15% in the net output, compared to the nominal conditions. This proves that an OTEC cycle could greatly benefit from using a dynamic model to predict its dynamic performance and the implementation of a control system.

Buildings contribute to 30% of global CO₂ emissions and consume 40% of the global energy supply (Yang et al., 2014). Heating and cooling requirements of the buildings form the major part of the energy consumption in buildings (Culha et al., 2015). Thus to solve this problem, one of the solutions currently being
looked at is to recover heat from the sewage. Cities have large sewage flows and in the winter the sewage is warmer than ambient and in the summer it is colder than the ambient, thus making it a good heat source and sink respectively. This work involves the integration of waste water heat exchanger with heat pump
to form a Waste Water Source Heat Pump (WWSHP). This system was further integrated with Aquifer Thermal Energy Storage (ATES) system. The WWSHP system was modeled in Matlab and the aquifer was modeled in COMSOL. COMSOL Live-link Matlab feature was used to integrate the two models.
Polymers were chosen as heat exchanger material due to their low cost, low weight (lower CO₂ emissions during transportation), flexibility, non corrosive nature and low energy requirement in manufacturing (Hussain et al., 2017). Two systems were proposed to support the heating and cooling demands of the concert venue and convention centre of the Rotterdam, the ’Doelen’. The objective of this work was to illustrate the potential of polymer sewage heat exchangers. The first system was called the WWSHP system. In this system, heat was recovered from the sewage in the winter through polymer heat exchangers and was upgraded in a heat pump for use in the heating network of the ’Doelen’. The heat pump was a reversible one, thus, in the summer, heat was extracted from the cooling network of the ’Doelen’ and rejected to the sewage through the same polymer heat exchangers. To obtain more heat in the winter, a second system was proposed. This system was called WWSHP + ATES system. In this system, heat was extracted from the sewage and an aquifer. This extracted heat was upgraded in a heat pump for supply to the ’Doelen’. In the summer, the heat extracted from the ’Doelen’ along with the heat recovered from the sewage were used to refill the warm well of the aquifer to maintain thermal balance. The scope of the work also included optimizing the dimensions, material and cost of the waste water heat exchanger. In both the systems, the summer and the winter models were different, hence they were simulated separately. The heat recovery model was built based on a sewage channel near the ’Doelen’. The sewage channel data and the sewage flow and temperature data were provided by the Gemeente of Rotterdam. The waste wa-ter heat exchanger was chosen to be a multi row tube polymer heat exchanger. Various polymer options were available, among which the option with the highest thermal conductivity, High Density Poly-ethylene (HDPE) was chosen. Among six combinations of standard HDPE tube lengths and diameters, tube length of 30 m and tube inner diameter of 29 mm were found to be the most optimum in terms of economics and heat recovery. Based on the optimized tube dimensions, heat delivered by the system to the ’Doelen’ per unit cost was compared for different materials and the results confirmed that HDPE with a cost of 0.54 €/kg was the best choice. Thus, using the optimized combination of tube dimensions and HDPE as tube material, 374 MWh of heat was recovered from the sewage in the winter and 486 MWh of heat was supplied to the heating network of the ’Doelen’ through the heat pump. In the summer, 23 MWh was removed from the ’Doelen’ by the heat pump and 26 MWh was rejected to the sewage using the same HDPE heat exchangers. Among the different polymer and filler combinations, PE (Polyethylene) with 30% graphite filler was foundto be the best choice. Using PE with 30% graphite resulted in 32% higher heat recovery from the sewage in the winter and 15% higher heat rejection to the sewage in the summer when compared to HDPE with no fillers. Thermal enhancement of polymer tubes, although increased the amount of heat exchanged with the sewage in the winter and the summer, it reduced the system economic performance (kWh/€) in the winter.

The WWSHP + ATES system supplied 1244 MWh of heat to the ’Doelen’ in the winter and removed 388 MWh of heat from the ’Doelen’ in summer. Furthermore, thermal enhancement of polymers of the waste water heat exchangers reduced the performance (kWh/€) of the WWSHP+ATES system in both the summer and the winter. WWSHP + ATES system proved to be capable of handling higher heating and cooling demand than the WWSHP system. The costs of heat exchangers and electricity were also much higher for this option, thus making it less economical. For instance, the WWSHP model supplied 66 kWh to the ’Doelen’ per € spent, as opposed to the WWSHP + ATES system which supplied only 34 kWh/€. Thus, only high heating and cooling requirements would justify the use of WWSHP + ATES system.

Steel plants are one of the largest sources of waste heat. Waste heat recovery throughout the steelmaking process is not a new phenomenon. One of the sources of waste heat is found in the coke plant. Cokes are an essential part of steel production. During the coking process hot cokes are cooled down. Most coke plants in the world traditionally use water, so called wet quenching. In this process, all the heat put into the cokes is dispersed to the environment as steam. This waste heat source has huge potential. The goal of this study is to find a method to utilise this waste heat and to evaluate this method’s technical and economic feasibilities.
The chief issue that must be tackled in a design is the fact that the steam generated during a quench is close to atmospheric pressure. Another issue to be solved is that of the solid particles suspended in the steam. Several potential designs were produced to use the steam from a quench to recover the waste heat. Based on several criteria, the design using the Synext engine was found to be the superior one and was developed further.
This design is divided into three sections, capture, cleaning and storage. A water wall and capture valve are used to capture the steam. An impaction and a cyclone separator are used to rid the steam of the solid particles to the extent that their detrimental effect to the Synext engine is minimised. The sepa-rators’ dimensions are derived based on the steam input and Synext engine requirements. The steam is then stored in a storage vessel.
A Simulink model of the design is composed to simulate the process and evaluate its efficiency and technical feasibility. The model’s findings show that the outputs for certain cases require unreasonable dimensions for the design. The economic analysis showed the designs costs make it an unlucrative investment.

This thesis project aims to enable Bluerise to create a 3 [MW] plant for their OTEC system. The current model and lab setup used to create insight into the systems working mechanisms are based on a Kalina cycle configuration. This method uses a working fluid mixture of water and ammonia. After evaporation, the liquid and vapor are separated and the heated liquid is used in a recuperator to retain (some of) the heat and increase the efficiency of the system. The first 3 [MW] test plant that is planned to be built will be using an ORC configuration. This method solely uses ammonia as a working fluid and doesn’t use a recuperator to retain heat. Understanding the effects of liquid separation and re-circulation are important aspects while using this configuration. The working method of the current OTEC off-design model and lab setup will have to be altered to accommodate the ORC configuration. An extensive study on both available literature, the current OTEC off-design model and OTEC Demo lab setup lead to conclude that a gear pump will be implemented to drive the liquid re-circulation from the separator back to the evaporator. Parallel to the gear pump, a one-way valve is installed into the cycle so natural re-circulation experiments can also be conducted. From literature, a hypothesis is made on what the effect on the evaporator heat transfer rate could be by changing the re-circulation rate. The re-circulation rate must not be too high, because increased amounts of vapor bubbles increase fluid mixing and thus heat transfer. The re-circulation rate also must not be too low, because dry-out in the evaporator will occur, reducing the heat transfer rate. The OTEC off-design model that currently exists at Bluerise B.V. is used and expanded upon to accommodate the ORC configuration. The evaporator is changed in more detail, adding a heat transfer correlation and the possibility to calculate the evaporator pressure drop through two phase pressure drop correlations. After implementing the gear pump liquid re-circulation technique, the OTEC Demo can be used to create experimental data. From experiments, it is found that the re-circulation rate does not significantly change the evaporator heat transfer rate between 1.2 to 2.9 re-circulation rate. This is a remarkable result but can be explained by the low flow velocities in the evaporator, which indicate that the heat transfer process in the evaporator is mostly driven by pool boiling heat transfer mechanisms over flow boiling heat transfer mechanisms. Knowing that the re-circulation rate does not affect the evaporator heat transfer rate, liquid re-circulation can also happen naturally, by the liquid column driving force in the separator. Using this technique, a comparison with the Kalina cycle configuration using pure ammonia is made. The evaporator performance is higher in the Kalina cycle configuration, but the ORC configuration net power output is slightly higher. The main reason for this phenomenon is a lower required pumping power for the ORC configuration. The OTEC off-design model in ORC configuration is validated to the experimental data collected. The two phase heat transfer correlations used show to be very mass flux dependent, and applicable to flow boiling evaporative heat transfer. The correlations proposed by Taboas and Han et al. have the best fit to the experimental data. The correlation proposed by Taboas is used to validate the full cycle model. This two phase heat transfer correlation has a consistent negative deviation from the experimental data, causing the full cycle model to be conservative in the cycle performance it calculates. Finally, a scaling analysis is made in support of the efforts by Bluerise to create a 3 [MW] OTEC plant. Using the geometries supplied by Bluerise it is concluded that a 3 [MW] net power output could be achieved, but it heavily depends on the water side pump power needed and the turbine efficiency, which are not investigated in the current research.

Nowadays, large scale district heating networks (DHNs) in the Netherlands do not reach their potential as a renewable heat supplier, as the thermal energy is often produced by fossil-fueled installations. By 2030, the share of DHNs in the total thermal energy supply will increase and the thermal energy will mainly be supplied by renewable sources. The transformation toward renewable heat supplied DHNs is accompanied with a decrease in flexibility. Seasonal thermal energy storage (STES) systems are to a certain extend able to bring back flexibility.
The research question has been answered in four steps. First, the seasonal thermal energy storage technique with the highest potential for implementation in a large scale district heating network has been studied. Secondly, the most relevant characteristics of the STES were analyzed and used to create a model in Matlab of the thermal performance. Thirdly, the desired dimensions of the STES and its impact on a DHN were determined. A Matlab model was used to analyze the performance of the STES. This model also determined the optimal strategy to supply the thermal energy to the DHN. Finally, an analysis provided the economic performance of the optimal STES. Throughout the thesis, the district heating network of Utrecht is evaluated as a reference. This research confirms that it is economically and technically feasible to implement STES systems in an existing large scale DHNs. The most suitable STES technique is high temperature aquifer thermal energy storage (HT-ATES), as the investment cost and the required surface area are relatively low. The results show that multiple suitable locations are identified for HT-ATES in the DHN of Utrecht. A decentralized HT-ATES operating in a 'Total Coverage Winter' mode promises to have the best economical performance and can be economically competitive with other heat sources in the DHN. These results are based on the current prospect of the characteristics of the DHN of Utrecht (price of surplus heat, available sources, desired thermal power, supply temperature). The economic performance of the HT-ATES depends strongly on the specification of the DHN. A higher economic performance can be achieved with different characteristics for the DHN. The HT-ATES is expected to have a lower LCOH if either the storage volume is increased, the supply temperature is decreased or the thermal power is optimized with the stored volume. When these adjustments are satisfied the HT-ATES can out perform the current gas peak boilers (14 €/GJ).

In some countries, drying processes use up to 20% of the total energy consumption. Within the agriculture sector, drying of food and flowering products is a necessary step in production. A lot of companies make use of hot air dryers where the heat is gained by burning natural gas. A novel method is to use a heat pump assisted drying systems instead. Heat pump assisted drying realises a better product quality due to the ability of humidity and climate control of the drying medium: air. Additionally, there are possibilities for energy savings up to 50%. This thesis project is mentioned as the first step for an initiative to introduce heat pump drying into the horticulture sector. The project started almost 1 year ago and is still far from finished. Main goal was to get a good understanding of the product drying behaviour, drying capacities and the system requirements and footprints. Conclusions should determine whether there is a possibil-ity for market implementation or not. The results in this report are promising. Heat pump drying is a trending research topic in science, where new developments on predicting the dynamic drying behaviour of agricultural products show up every month. This study involves a computational model, where the dynamic process of drying flower bulbs is simulated. This model is validated by measurements on existing drying in-stallations. Building this model resulted in a good understanding about the flower bulb characteris-tics and the necessary drying capacities. Additionally, Heat pump drying systems are evaluated and a dynamically modelled. When both models are the drying process of FB’s can be optimized. The first protype of the HP drying system that will be used in further research will be shortly discussed. Conclusion of this report is that heat pump drying is a promising technique for drying of FB’s. The combination of technical advantages with energy savings, could lead to better product quality and lower production costs. The business case is strengthened by future perspectives where energy efficiency and reduction of CO2 emissions will more and more important due to climate change.

TechnipFMC is pushing innovations to reduce the emissions of ethylene plants separations. This development is also driven by customer demands. They face increasingly strict legislation on \ce{CO2} emissions. Separation in distillation columns is one of the major energy intensive unit operations in an ethylene plant, and increasing their efficiency directly improves the overall plant efficiency. This work is commissioned by TechnipFMC, which is part of the HEADLINES consortium for heat integrated distillation column development. The plate-packed heat-integrated distillation column (pp-HIDiC) is a promising new distillation column design that could replace current ethane/ethylene fractionators (\splitter{}). A numeric model and calculation tool is needed to aid the design of a pp-HIDiC for the \splitter{} as proposed in the work by \textcite{bruinsma2012}. A numeric modelling procedure for this type of column was developed in this work. This modelling procedure was then implemented in Python. A rate-based modelling methodology was applied to describe the continuous heat- and mass transfer on the internal column structures. The aim of the model is to find column dimensioning and duties, which followed from the model's balance equations. A designer should be able to input the column dimensions and flow rates, and run the model to retrieve mole fractions, heat transfer and temperatures along the column. Heat- and mass transfer correlations were needed, despite there being no special correlations for the proposed setup. Generic structured packing correlations were used from literature as a modelling approximation. The performance of different available thermodynamic packages for Python was compared. Diffusivity and viscosity correlations were implemented to aid in mass transfer calculations. A Python Newton solver was chosen to solve the model equations, using CoolProp to perform thermodynamic calculations. Due to the choice of model variables, convergence of the equations remained an issue. In the system of equations, column temperatures cannot follow from the equilibrium relation on the vapour-liquid interface, as they do not depend on each other strongly enough. It is not possible to find condenser and reboiler duties as an output of this model while specifying boil-up and reflux ratios. The model needs to be changed so that these variables are fixed by the user, and the reflux ratios are a model result instead. A model's thermodynamic calculation packages should be robust. Additionally, a well-documented interface with the used programming language and validated data is needed. This could require the use of commercial thermodynamic software, or validated process simulators. The model designer is then less hindered by programming environment related issues. A model that is purely based on theory and inapplicable correlations cannot be the only basis of design decisions. The used heat and mass transfer correlations are not made for the studied geometry, so their usage introduces inaccuracies in the model results. Applicable correlations from experiment are recommended to characterise pressure drop, heat transfer between HIDiC compartments, heat transfer coefficients, and vapour and liquid mass transfer coefficients on the packing surface. Further experiments can also aid in better understanding of the wetting, flooding and liquid distribution of various pp-HIDiC geometries. Beside characterising one packing geometry, it will be beneficial to experiment on different viable geometries that are specifically suitable for a pp-HIDiC. Too few alternative designs have been tested so far. Investigating more geometries can help to find the most promising designs more quickly. After that, models and experiments can then complement each other to develop the most promising geometries and accelerate the column development.