This thesis deals with the process of wood drying. It is a method of removing excess water from wood. Drying can be divided into two basic types. The first type is natural drying. The material is dried without the presence of foreign energy source. This type depends only on climatic conditions and the amount of sunlight. Another type is artificial drying, where is pre-sent a foreign energy source, such as a biomass boiler. The second type is significantly faster than the first. The second type of drying uses a device called a wood dryer. There are a lot of types of wood dryers, the most widely used are kiln dryer, belt dryer, rotary drum dryer. In these devices, the thermal energy is transferred to the drying materials by the flowing warm drying medium (convection). The heat is transferred to the drying medium in a heat exchan-ger. Because the drying process is very energy demanding, it is appropriate to reduced the required energy. This can be done by regenerating heat and water. In the heat exchanger, part of the heat can be gained from the flowing exhaust medium. If a condensation of evaporated water in the exchanger occurs, the latent heat of the water is released. The gained heat is used to preheat the drying medium and thereby to reduce the required energy.

This report studies the importance of solar cooking when moving towards a more sustainable and egalitarian future. The problems regarding its implementation, in fact, technological, social and economic problems, are presented. A historic overview is offered as well as the theory behind the technology. After studying the current situation concerning cooking, different devices have been analysed and considered, from small ones suitable for households to bigger ones for institutions. Furthermore, several backup systems are also proposed aiming to obtain an ideal Integrated Solar Cooker (ISC). Possible hybrid systems have also been evaluated during the work. Furthermore, state-of-the-art technology in Thermal Energy Storage (TES) is also commented and taken into account for the most efficient combination of technologies. Several photovoltaic kitchens are mentioned in this report as well. Two main conclusions have been drawn: trying to solely rely on the sun is a mistake and the ideal and universal ISC does not exist. Other factors besides the income are determinant when choosing an energy source, therefore, a thorough investigation in every particular case is completely necessary for a successful implementation of an ISC. However, the countless devices available make the adoption of solar technology possible in every situation, helping to achieve some of the Sustainable Development Goals.

A feasibility study on upgrading an existing heat distribution network to a low-temperature distribution grid has been carried out during this project. The integration of a solar thermal system combined with a borehole thermal energy storage (BTES) for covering the space heating demand of the buildings as well as the application of CO2 heat pumps and water storage tanks for domestic hot water (DHW) production were investigated in order to apply more renewable energy sources. The energy analysis included several measures, such as modeling the energy demand of the buildings, finding a reasonable number of solar collectors to be installed and dimensioning a ground source heat pump (with the use of CoolPack and Engineering Equation Solver EES) and a geothermal storage (Earth Energy Designer Software EED) as well as CO2 heat pumps (CoolPack/EES). An economic analysis of all proposed measures has been carried out based on the Net Present Value (NPV) and Net Present Value Quotient (NPVQ). Initial costs, annual costs, annual savings as well as the payback time of the energy systems have been calculated. It is found that it is not feasible to invest in the proposed energy system for space heating because the payback time (28 years) of the system is longer than the lifetime of the solar thermal system. Furthermore, the solar gain from the solar collectors is not sufficient for recovering the ground temperature of the BTES with solar energy only which is why external sources would be needed for supplying the remaining energy needed to recover the ground temperature. Results show that an integration of CO2 heat pumps and water storage tanks for DHW production is very promising as the payback time for the investigated system is only 4 years which is why this part should be investigated further.

The use of an attached sunspace is one of the most popular passive solar heating techniques. One of the main drawbacks of the sunspace is getting over heated by the sun energy during the hot season of the year. Even in northern climates overheating could be problematic and there is a considerable cooling demand. Shading is one of the most efficient and cost effective strategies to avoid overheating due to the high irradiation especially in the summer. Another strategy is using ventilation system to remove the excess heat inside the sunspace. However this rejected energy can be captured and stored for future energy demands of the sunspace itself or nearby buildings. Therefore the Solar blind system has been considered here for the shielding purpose in order to reduce the cooling demand. By considering the PV/T panels as the solar blind, the blocked solar energy will be collected and stored for covering part of the heating demand and the domestic hot water supplies of the adjacent building.  From a modeling point of view, the sunspace can be considered as a small-scale closed greenhouse. In the closed greenhouse concept, available excess heat is indeed utilized in order to supply the heating demand of the greenhouse itself as well as neighboring buildings. The energy captured by PV/T collectors and the excess heat from the sunspace then will be stored in a thermal energy storage system to cover the daily and seasonal energy demand of the attached building. In the present study, a residential building with an attached sunspace with height, length and width of 3, 12 and 3.5 meters respectively has been assumed located in two different locations, Stockholm and Rome. Simulations have been run for the Solar blind system integrated with a short-term and a long-term TES systems during a year to investigate the influence of the sunspace equipped with a PV/T Solar blind on the thermal behavior of the adjacent building. The simulated results show that the Solar blind system can be an appropriate and effective solution for avoiding overheating problems in sunspace and simultaneously produce and store significant amount of thermal energy and electricity power which leads to saving considerable amount of money during a year.

Nowadays continuous increase of energy consumption increases the importance of replacing fossil fuels with renewable energy sources so the CO2 emissions can be reduced. To use the energy in a more efficient way is also favorable for this purpose. Thermal Energy Storage (TES) is a technology that can make use of waste heat, which means that it can help energy systems to reduce the CO2 emissions and improve the overall efficiency. In this technology an appropriate material is chosen to store the thermal energy so it can be stored for later use. The energy can be stored as sensible heat and latent heat. To achieve a high energy storage density it is convenient to use latent heat based TES. The materials used in this kind of storage system are called Phase Change Materials (PCM) and it is its ability of absorbing and releasing thermal energy during the phase change process that becomes very useful. In this thesis a simulation model for a system of thermal energy transportation has been developed. The background comes from district heating systems ability of using surplus heat from industrials and large scale power plants. The idea is to implement transportation of heat by trucks closer to the demand instead of distributing heat through very long pipes. The heat is then charged into containers that are integrated with PCM and heat exchangers. A mathematical model has been created in Matlab to simulate the system dynamics of the logistics of the thermal energy transport system. The model considers three main parameters: percentage content of PCM in the containers, annual heat demand and transport distance. How the system is affected when these three parameters varies is important to visualize. The simulation model is very useful for investigation of the economic and environmental capability of the proposed thermal energy transportation system. Simulations for different scenarios show some expected results. But there are also some findings that are more interesting, for instance how the variation of content of PCM gives irregular variation of how many truck the system requires, and its impact on the economic aspect. Results also show that cost for transporting the heat per unit of thermal energy can be much high for a small demands compared to larger demands.

The objective of this research is to evaluate the potential of thermal energy storage in supermarkets with CO2 refrigeration systems. Suitable energy storage techniques are investigated and the seasonal storage technology of boreholes is chosen to be the focus of the study. The calculations are done for five supermarket refrigeration systems with different combinations of heating systems and borehole thermal energy storage control strategies. The two heating systems analyzed are the ground source heat pump and the heat recovery from the supermarket’s refrigeration system. The simulation results show that the introduction of thermal energy storage in the scenarios with heat pump can reduce the annual total energy by 6.3%. It is also shown that increasing the number of boreholes can decrease the life cycle cost of the system. Moreover, it is established that a supermarket system with heat recovery consumes 8.1% less energy than the one using heat pump and adding thermal energy storage on the heat recovery system further improves the energy consumption by 3.7% but may become costly.

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The major challenge associated with renewable-energy systems especially solar, is the supply intermittency. One effective solution is to incorporate thermal energy storage components utilizing phase change materials (PCMs). These materials have the potential to store large amounts of energy in relatively small volumes and within nearly an isothermal storage process. The primary drawback of today’s PCMs is that their low thermal conductivity values critically limit their energy storage applications. Also, this grossly reduces the melting/ solidification rates, thus making the system response time to be too long. So, the application of heat transfer enhancement is very important. To improve the PCM storage performance, an efficient performing containment vessel (triplex-tube) along with applications of various heat transfer enhancement techniques was investigated. The techniques were; (i) dispersion of solid nanoparticles, (ii) incorporation of metal foam with nanoparticle dispersion, and (iii) insertion of longitudinal fins with nanoparticle dispersion. Validated simulation models were developed to examine the effects of implementing these techniques on the PCM phase-change rate during the energy storage and recovery modes. The results are presented with detailed model description, analysis, and conclusions. Results show that the use of nanoparticles with metal foam or fins is more efficient than using nanoparticles alone within the same volume usage. Also, employing metal foam or fins alone results in much better improvement for the same system volume.

This study investigates the feasibility and performance of a hybrid system integrating photovoltaic (PV) and solar thermal technologies for industrial process heat. By analyzing various parameters including cost, income, energy production, and system specifications, valuable insights are obtained. The study explores the potential of solar heating (SH) systems as a renewable thermal energy source for industrial processes, overcoming challenges of high costs and limited fossil fuel usage in industrial facilities through hybrid configurations. Data analysis includes cost analysis, income generation, energy balance, and system specifications such as temperature ranges, collector sizes, and efficiencies. While acknowledging limitations in simulation simplifications and the use of a single load profile, the study presents conclusions on the system's economic viability, technical capabilities, and potential applications. The findings highlight the importance of hybrid PV and solar thermal systems in enhancing energy efficiency and promoting renewable energy adoption in industrial process heating.