One of the main challenges in the implementation of renewable energy is the mismatch between supply and demand. Energy storage has been identified as one of the solutions to the mismatch problem. Among various storage technologies, thermal energy storage (TES) is foreseen to have a significant role to achieve a low carbon energy systems because of the large share of thermal energy demand and its relatively low cost. However, integrating TES into energy systems requires careful design and implementation since otherwise potential financial and environmental savings may not be achieved. Computational-based design tools are ubiquitous in the design process of modern energy systems and can be broadly categorised into two methodologies: optimisation and simulation. In both cases, designing an energy system with storage technology is significantly more complicated than those without, mainly due to the coupling of variables between time steps. This thesis is concerned with two facets of the application of TES in energy systems. First, the role of TES in improving the performance of renewable-based domestic heating systems. Second, the implementation of optimisation and simulation tools in the design of energy systems with integrated TES. They are addressed by examining two case studies that illustrate the spatial and temporal variance of energy systems: a single dwelling heat pump system with a hot water tank, and a solar district heating system with a borehole thermal energy storage. In the single dwelling case study, the technical and financial benefits of TES installation in a heat pump system are illustrated by the optimisation model. A simulation model which utilises the optimisation results is developed to assess the accuracy of the optimisation results and the potential interaction between the two methodologies. The solar district heating case study is utilised to highlight the potential of a time decomposition technique, the multiple time grids method, in reducing the computational time in the operational optimisation of the system. Furthermore, the case study is also employed to illustrate the potential of installing a similar system in the UK. The latter study was performed by developing a validated simulation model of the solar district heating system. The findings of the analyses reported in this thesis exemplify the potential of TES in a domestic and community-level heating system in the UK. They also provide a basis for recommendations on the improved use of optimisation and simulation tools in the design process of energy systems.

<p>This is a report written for an examination project C-level, on the subject of energy. The examination project is a product of the FVB Sweden AB (district heating bureau). It started with a meeting with Stefan Jonsson FVB Sweden AB, were he explained the content of the project, and from this a presentation of the problem was made. The problem that needed to be solved was how they could control the valves in the system to provide heating to everyone in the system. The valves are often oversized so the pump in the heating plant would have to be enormous to be able to provide enough flow to be sufficient, if everyone in the system had there valves fully opened.</p><p> </p><p>I came up with two solutions to the problem, one was a wireless network that could keep track of the valves and the other solution was an extra sensor that was placed on the radiator. The purpose for that was to open the valve if the temperature dropped more than one degree inside. With the help of a program called IDA it was calculated that, if the temperature drop five degrees, they would have sixteen hours at the heating power plant to open the flow before the sensor open the valves.</p><p> </p><p>After careful consideration I came up with the conclusion that the wireless network must be the best solution. Mostly because you can monitor all the clients in the system from the heating power plant and that will make it easier to discover faults and temperature differences.</p><p>Wireless networks is already a well tested solution in form of wireless controlled electricity meters so it shouldn’t be to much of a problem connecting these sensors to it either.</p>

<p>This thesis presents a study of the cooling process of a solid block performed by a turbulent air flow channel. The study focuses on the turbulent flow and its influence in the heat transfer of the block.</p><p>The first part of the thesis is an analysis of the different turbulent model and their adaptation on the necessities of this study. Once the turbulent model has been confirmed it makes a study of the behavior of the cooling process by CFD (Computational Fluid Dynamics), and an analysis of the numerical accuracy of this computational study.</p><p>When the procedure of the study of the cooling process is defined it proposes some different variations in the initial solution to improve this process. The study concentrates in variations of the turbulence and the geometry of the studied block.</p><p>Finally, the different improving are discussed analyzing parameters as the heat transfer, pressure drop, time consuming or energy consuming.</p>

<p>This project has been developed at the company Gavlegardarna. The companyowns a large part of the buildings of Gävle and two of them are the objective ofthe project. Gavlegardana is highly concerned about the environment; for thisreason, they cooperate on the subject with the energy management from theirtechnical department.</p><p>Gävle is one of the Swedish cities where the DH (district heating) network isdistributed, arriving to most of the dwellings, industries and commercialbuildings. As DH uses environmentally friendly sources of energy,Gavlegardana is introducing it in its buildings.</p><p>Electrical radiators and boilers were installed in the buildings when the price ofelectricity was more affordable than nowadays. The price of the electricity canbe considered 1,23 SEK/kWh while the DH price is 0,45 SEK/kWh.</p><p>Consequently, this is another reason why the objective of the company at thepresent time is to replace electrical space heating systems by means of districtheating.</p><p>The energy balance of the buildings is analysed in order to study their currentenergy situation. This entails the consideration of heat gains and lossesinvolved. The heat gains of the building are the heat from solar radiation whicharrives at the building trough the windows, the heat internally generated (bypersons, lighting and other devices) and the heat supplied. The heat losses are composed by the transmission trough walls and windows, the infiltrations, the heat used for hot tap water and the ventilation losses.</p><p>An important part of the work required to calculate the energy balance hasconsisted of the collection and organization of all the data (areas, types ofmaterial, electrical devices, lighting, number of employees, opening hours...).This data comes from the drawings of the buildings provided by the companyand from the information gathered during the visits to the installation. In addition, the ventilation flows were measured in-situ using the tools provided by Theorells.</p><p>Gavle Energi, the DH distributor company, has been contacted in order to fixthe cost and other details related to the district heating connection. The heatexchanger models, selected from Palmat System AB, are TP20 for Building Aand TP10 for Building B. TP20 provides 100 kW of heating and 0,4 l/s of hot tap water and TP10 provides 50 kW and 0,31 l/s respectively. The capital cost is 187500 SEK which includes the heat exchangers and the connection cost.</p><p>As the secondary circuit is not currently installed because the existing system iscomposed by electrical radiators, the installation of the piping network in thebuilding has been designed. The radiators’ power is calculated taking intoaccount the need of heat in each room which is estimated as the transmissionlosses. This need of heat calculated is higher than the energy currently supplied which means that the thermal comfort is not achieved in all the rooms of the buildings.</p><p>In spite of using more energy for space heating, the change of heat sourceentails a lower energy cost per year. The selected radiators are from Epeconand the investment cost (including the installation) is 203671 SEK. The brand of the selected pipes is Broson and the investment cost of the total piping system is 66000 SEK.</p><p>The initial investment of the new installation is 457171 SEK, considering the DHconnection, heat exchangers, radiators and pipes. If the initial investment istotally paid in cash by the company the payback will be fulfilled in 6 years. Incase of borrowing the money from the bank (considering an interest rate of 5%), two possibilities can be considered: paying back the money in annual rates over 15 years or 30 years of maturity. The paybacks are 11 and 8 years respectively.</p><p>After designing the DH piping system in the buildings, estimating the total costs of the investment and studying the project’s feasibility by suggesting different payment options, some possible energy savings are recommended.</p><p> </p><p>The first of the options refers to the transmission losses trough the windowswhose values’ are considerably high. Using a glass with a lower U-value, theselosses can decrease until 66% (with triple glass windows). Consequently, thepower required for space heating can also be reduced until 26%.</p><p>Regarding the ventilation, rotating heat exchangers are currently used, whichentails the problem of smells mixture detected by the users of the buildings. By changing them with flat-plate heat exchangers, the problem is solved and the efficiency is increased from 66% to 85%. The new heat exchanger cost is340387 SEK and it has a payback of 10 years.</p>

This is a report written for an examination project C-level, on the subject of energy. The examination project is a product of the FVB Sweden AB (district heating bureau). It started with a meeting with Stefan Jonsson FVB Sweden AB, were he explained the content of the project, and from this a presentation of the problem was made. The problem that needed to be solved was how they could control the valves in the system to provide heating to everyone in the system. The valves are often oversized so the pump in the heating plant would have to be enormous to be able to provide enough flow to be sufficient, if everyone in the system had there valves fully opened.   I came up with two solutions to the problem, one was a wireless network that could keep track of the valves and the other solution was an extra sensor that was placed on the radiator. The purpose for that was to open the valve if the temperature dropped more than one degree inside. With the help of a program called IDA it was calculated that, if the temperature drop five degrees, they would have sixteen hours at the heating power plant to open the flow before the sensor open the valves.   After careful consideration I came up with the conclusion that the wireless network must be the best solution. Mostly because you can monitor all the clients in the system from the heating power plant and that will make it easier to discover faults and temperature differences. Wireless networks is already a well tested solution in form of wireless controlled electricity meters so it shouldn’t be to much of a problem connecting these sensors to it either.

This project has been developed at the company Gavlegardarna. The companyowns a large part of the buildings of Gävle and two of them are the objective ofthe project. Gavlegardana is highly concerned about the environment; for thisreason, they cooperate on the subject with the energy management from theirtechnical department. Gävle is one of the Swedish cities where the DH (district heating) network isdistributed, arriving to most of the dwellings, industries and commercialbuildings. As DH uses environmentally friendly sources of energy,Gavlegardana is introducing it in its buildings. Electrical radiators and boilers were installed in the buildings when the price ofelectricity was more affordable than nowadays. The price of the electricity canbe considered 1,23 SEK/kWh while the DH price is 0,45 SEK/kWh. Consequently, this is another reason why the objective of the company at thepresent time is to replace electrical space heating systems by means of districtheating. The energy balance of the buildings is analysed in order to study their currentenergy situation. This entails the consideration of heat gains and lossesinvolved. The heat gains of the building are the heat from solar radiation whicharrives at the building trough the windows, the heat internally generated (bypersons, lighting and other devices) and the heat supplied. The heat losses are composed by the transmission trough walls and windows, the infiltrations, the heat used for hot tap water and the ventilation losses. An important part of the work required to calculate the energy balance hasconsisted of the collection and organization of all the data (areas, types ofmaterial, electrical devices, lighting, number of employees, opening hours...).This data comes from the drawings of the buildings provided by the companyand from the information gathered during the visits to the installation. In addition, the ventilation flows were measured in-situ using the tools provided by Theorells. Gavle Energi, the DH distributor company, has been contacted in order to fixthe cost and other details related to the district heating connection. The heatexchanger models, selected from Palmat System AB, are TP20 for Building Aand TP10 for Building B. TP20 provides 100 kW of heating and 0,4 l/s of hot tap water and TP10 provides 50 kW and 0,31 l/s respectively. The capital cost is 187500 SEK which includes the heat exchangers and the connection cost. As the secondary circuit is not currently installed because the existing system iscomposed by electrical radiators, the installation of the piping network in thebuilding has been designed. The radiators’ power is calculated taking intoaccount the need of heat in each room which is estimated as the transmissionlosses. This need of heat calculated is higher than the energy currently supplied which means that the thermal comfort is not achieved in all the rooms of the buildings. In spite of using more energy for space heating, the change of heat sourceentails a lower energy cost per year. The selected radiators are from Epeconand the investment cost (including the installation) is 203671 SEK. The brand of the selected pipes is Broson and the investment cost of the total piping system is 66000 SEK. The initial investment of the new installation is 457171 SEK, considering the DHconnection, heat exchangers, radiators and pipes. If the initial investment istotally paid in cash by the company the payback will be fulfilled in 6 years. Incase of borrowing the money from the bank (considering an interest rate of 5%), two possibilities can be considered: paying back the money in annual rates over 15 years or 30 years of maturity. The paybacks are 11 and 8 years respectively. After designing the DH piping system in the buildings, estimating the total costs of the investment and studying the project’s feasibility by suggesting different payment options, some possible energy savings are recommended.   The first of the options refers to the transmission losses trough the windowswhose values’ are considerably high. Using a glass with a lower U-value, theselosses can decrease until 66% (with triple glass windows). Consequently, thepower required for space heating can also be reduced until 26%. Regarding the ventilation, rotating heat exchangers are currently used, whichentails the problem of smells mixture detected by the users of the buildings. By changing them with flat-plate heat exchangers, the problem is solved and the efficiency is increased from 66% to 85%. The new heat exchanger cost is340387 SEK and it has a payback of 10 years.

Thermal energy storage systems, precisely latent thermal energy storage (LTES), are systems capable of recovering and storing thermal energy from waste processes, including hot exhaust gases out of combustion engines, or even renewable sources of energy like solar energy. LTES rely on phase change materials (PCMs) to store a significant amount of thermal energy in a relatively small volume. With limited volume and at almost constant temperature, they are capable of storing a large amount of thermal energy, mainly latent energy. Studies of LTES systems have focused primarily on system and process optimization including transient behavior as well as field performance. A major drawback in the development of the use of PCM in LTES has been the low thermal conductivity characteristic of most PCMs. Thus, there is a need to enhance heat transfer using reliable techniques, with the goal of reducing the charging and discharging times of PCM in LTES systems. Some approaches that have been studied in the past include use of finned tubes, insertion of metal matrix into PCM, and microencapsulation of PCM. The performance of TES configurations in forced convection have been characterized using Reynolds numbers (Re), and Stefan numbers (Ste) of the heat transfer fluid (HTF) for different enhancement techniques. The goal of this study is to experimentally investigate the effectiveness of corrugated PCM panels with high surface-to-volume ratio in forced convection as a function of HTF mass flow rate, charging temperature, and flow direction through a corrugated TES unit. The PCM (octadecane) has been segmented using sealed corrugated panels containing several channels immersed in the HTF stream. With this approach, the author expects that the charging and discharging times will be substantially reduced due to the high surface-to-volume ratio of the PCM panel for heat transfer. Of the three conditions examined, the HTF direction influenced the charging and discharging times the most with significant reductions in these times observed when the HTF flow direction through the TES was upwards. Buoyancy effects, observed at high Stefan numbers, were important during the charging (melting) process and greatly influenced the temperature profiles along each channel. Results indicate that the devised TES is more effective than some other TES systems in the literature.

The main purpose of this research is to design a thermal energy conversion device, which is aimed to collect unused heat produced by nature. In order to achieve high-efficiency conversion, some novel devices will be studied to convert heat energy into mechanical power. A simple heat exchanger as well as heat engine device is proposed in this study. Dichloromethane is used as an important factor due to its physical properties. Finally, the concept of a tubular linear generator will be adopted to generate electric power. The feature of the proposed simple thermal energy conversion device is that we can use unused heat sources as input, such as solar energy and waste heat from car engines. Besides, the system is capable to work under the condition of low-temperature difference

This thesis presents a study of the cooling process of a solid block performed by a turbulent air flow channel. The study focuses on the turbulent flow and its influence in the heat transfer of the block. The first part of the thesis is an analysis of the different turbulent model and their adaptation on the necessities of this study. Once the turbulent model has been confirmed it makes a study of the behavior of the cooling process by CFD (Computational Fluid Dynamics), and an analysis of the numerical accuracy of this computational study. When the procedure of the study of the cooling process is defined it proposes some different variations in the initial solution to improve this process. The study concentrates in variations of the turbulence and the geometry of the studied block. Finally, the different improving are discussed analyzing parameters as the heat transfer, pressure drop, time consuming or energy consuming.

A city’s characteristics of mixed-use zoning, diverse built form, high-density development, and residual heat generation by urban processes, present potential for optimizing the thermal energy end-use of certain waste streams. A method was developed to identify sources of waste thermal energy and heat demand clusters in a mixed-use jurisdiction and design a preliminary primary network of a district heating system based on these waste heat sources. The method applies systems analysis, energy potential mapping (GIS spatial analysis) and network optimization (linear programming) techniques. The method is implemented using a case study of data for peninsular Halifax. Finally, the method and implementation’s influence on climate change (i.e. a reduction in GHG emissions) and energy security, two central themes of this research, are discussed.