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Positive Energy Districts can be defined as connected urban areas, or energy-efficient and flexible buildings, which emit zero greenhouse gases and manage surpluses of renewable energy production. Energy storage is crucial for providing flexibility and supporting renewable energy integration into the energy system. It can balance centralized and distributed energy generation, while contributing to energy security. Energy storage can respond to supplement demand, provide flexible generation, and complement grid development. Photovoltaics and wind turbines together with solar thermal systems and biomass are widely used to generate electricity and heating, respectively, coupled with energy system storage facilities for electricity (i.e., batteries) or heat storage using latent or sensible heat. Energy storage technologies are crucial in modern grids and able to avoid peak charges by ensuring the reliability and efficiency of energy supply, while supporting a growing transition to nondepletable power sources. This work aims to broaden the scientific and practical understanding of energy storage in urban areas in order to explore the flexibility potential in adopting feasible solutions at district scale where exploiting the space and resource-saving systems. The main objective is to present and critically discuss the available options for energy storage that can be used in urban areas to collect and distribute stored energy. The concerns regarding the installation and use of Energy Storage Systems are analyzed by referring to regulations, and technical and environmental requirements, as part of broader distribution systems, or as separate parts. Electricity, heat energy, and hydrogen are the most favorable types of storage. However, most of them need new regulations, technological improvement, and dissemination of knowledge to all people with the aim of better understanding the benefits provided. [ABSTRACT FROM AUTHOR]

Heat storage is an important part for heat integration between nonrepeatable batches. This article suggests a new approach in the design of heat storage exchange network for heat integration between nonrepeatable batches. This approach is built on the TRANSSHIPMENT method. The main idea is reusing the waste heat from stream segments that are designed to exchange heat with utilities. These extracted stream segments are added to every upcoming time slice as new energy streams. The possible heat exchange between extracted segments and existing streams in every Time Slice is based on the suggested algorithm which includes the main rules of the Pinch technology. All possible matches are potential heat storage units or subsystems. The efficiency of heat recovery increases if the schedule of nonrepeatable batches is repeated every day. That makes a great impact on the production costs. Otherwise, as it is in the given case study, the waste heat reduction is small and cannot support the investment for the solution. The reduction of hot utility in the presented case study is 43.5% and the reduction of cold utility is 12.1% in the start‐up period of the plant (58.94 hours). [ABSTRACT FROM AUTHOR]

Heat integration of repeatable batches with heat storage is a complex problem. This article suggests a new approach in the determination of possible heat storage for repeatable batch processes. This approach is based on the TRANSSHIPMENT method. The surplus heat and cold from streams and stream segments are added to the already designed heat exchanger networks for each time slice. These streams or stream segments from other time slices are supposed to match with streams or stream segments in a particular time slice. The heat content together with the changed supply and target temperatures of streams, and the minimal temperature difference for heat exchange are the main parameters used in the suggested method. The proposed technique creates a heat exchanger network between streams and potential heat storage at different times. The solution is a secondary network of heat storage units. The benefit in design of the solution is heat recovery for 11.51 kW per cycle of the analyzed case study. The annual heat recovery by cooling and heating separately is 4488.1 kW. As a result of suggested solution, the waste heat is minimized for approximately 13.5%. [ABSTRACT FROM AUTHOR]

Drying processes are one of the main consumers of heat energy in production. Any decreases in heat consumption during the drying process will considerably decrease production costs. This study analyzes the high consumption of heat in the drying of baker's yeast. The main task is to minimize the energy demand and lower the price of the final products with partial heat recovery. These changes will require system modifications. One of the most popular and effective methods that can be used in this case is heat process integration with Pinch Technology. In this study, a reference system was simulated with a mathematical model and analyzed for waste heat streams. This paper suggests the redesigning of a drying system for production of active dry yeast. Selected streams that satisfy conditions for heat process integration were involved in the evaluation for a better solution. Two different scenarios were proposed as possible solutions. The suggested solutions are retrofit designs of Heat Exchanger Networks. These Heat Exchanger Networks include already installed heat exchangers as well as new heat transfer units. The selection of better design was made with economic analysis of investment. The proposed scenarios of the analyzed sub-system give improvement in heat energy recovery. The best determined solution reduces the cost and thus has the highest profitability, but not the highest heat energy recovery. [ABSTRACT FROM AUTHOR]

The paper deals with the heat integration of a bioprocess plant which produces yeast and ethyl-alcohol. The referent plant is considered to be a multiproduct batch plant which operates in a semi-continuous mode. The design of a heat recovery system is performed by batch pinch analysis and by the use of the Time slice model. The results obtained by direct and indirect heat integration approaches are presented in the form of cost-optimal heat exchanger networks and evaluated by different thermodynamic and economic indicators. They signify that the heat recovery system without a heat storage opportunity can be considered to be a more profitable solution for the energy efficiency increase in a plant. [ABSTRACT FROM AUTHOR]

The decrease of natural reserves of non-renewable energy sources increases the energy prices. That initiates the fossil fuel replacement with renewable energy sources. The sun is an unlimited source of heat, but that is not enough used for industrial processes. The main reason is the complexity of heat integration between solar heating systems, process streams, and heat storage. Streams in batch processes and the solar heat delivery are time dependent. The intensity and the duration of insolation affect the capacity of the heat that can be used or stored. This study attempts to offer and approve solutions for thermal integration between solar thermal system and process streams. For that purpose is used Pinch technology for batch processes and solution algorithm is proposed. The analysis is based on a plant for ethanol production in the city of Bitola. The heat recovery is solved with design of Heat Exchanger Network. The rest of heat demand is supplied from the solar heating systems. The purpose of this paper is the possibility for maximal replacement of the required thermal energy from fossil fuel by solar heat. Three approaches are offered. They include the heat integration of a solar heating system with and without heat storage. Two options for thermal storage are suggested. The heat storage used the pressurized water and thermal oil as separated cases. The proposed solutions are adapted to the process schedule. The size of the equipment for the solutions does not depend only on the manufacturing process and its schedule, but also depends on possibilities for collecting thermal radiation from the sun. The geolocation of the plant and the used meteorological parameters for the day of the year have a substantial impact on the final decision. The proposed 18 solutions are designed for the three characteristic days – equinox, winter and summer solstices; for systems with evacuated tubes and parabolic concentrators. The economic analysis selected the most attractive solution – heat integration with evacuated tubes and heat storage with pressurized water at the winter solstice. This solution replaced approximately 35–40% of calculated heat demand delivered by the use of fuel oil. Image 1 • Integration of ethanol production plant with solar heating system. • Heat integration between fluctuating solar heat and process streams. • Analysis of cases for three referent days: equinox, winter and summer solstice. • The comparison based on collector types & area, heat storage and insolation. • Economic analysis selects the best proposed solution. [ABSTRACT FROM AUTHOR]

• Review of methods used for heat integration of Organic Rankine Cycle. • Integration of Organic Rankine Cycle with industrial waste heat. • Influence of working fluid selection, architecture and low temperature waste heat. • Problems in integration with continuous and batch industrial processes. Production systems represent a significant source of waste heat. The waste heat cannot be reused often. Many optimization methods can give a solution for waste heat recovery. However, the results do not depend only on the method. The low-temperature waste heat makes difficulties for its recovery within the processes. Organic Rankine Cycle units can be used for low-temperature heat transformation into electricity. Linking the Organic Rankine Cycle within the heat integrated system is not simple. This depends on the influence of a few important factors. The process parameters of the working medium, the physical and chemical characteristics of the working fluid, the continuity of heat supply, and the temperature level of waste heat are necessary conditions that must be included in optimization. The optimization method should determine the optimal operating point of the Organic Rankine Cycle. The displacement of the operating point leads to decrease in the effective transformation of heat into electricity. These problems are analyzed through a review of the methods and approaches used for the integration of Organic Rankine Cycle in thermal process systems. These include Pinch technology, Non-Linear Programming, Multiple Integer Linear Programming, Genetic Algorithm, Artificial Neural Network and many different approaches for polygeneration systems. All methods were compared and systematized in a general scheme for integration of an Organic Rankine Cycle with low-temperature industrial waste heat supply. This work also includes experience in implemented and designed projects of an integrated Organic Rankine Cycle. [ABSTRACT FROM AUTHOR]