Impact of Domestic Hot Water Systems on District Heating Temperatures (original) (raw)
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Heat Supply Systems of Renovated Residential Buildings
Since 2010 in Latvia energy efficiency improvement measures in residential buildings have been actively implemented with an aim to reduce heat energy consumption and heating costs in houses. The aim of the study is to find optimal solutions for reducing energy consumption and increasing energy efficiency indicators of heating and domestic hot water systems. In the framework of the study heat consumption analysis of the domestic hot water supply systems in residential buildings was carried out. The results showed that heat energy savings and home energy efficiency theoretically and optimistically predicted by the renovation project after three years of operation of renovated houses were not reached. It was concluded after a thorough analysis that the external enclosing construction insulation reached predicted energy savings. Energy efficiency of the heat supply system was low, thermal energy consumption was higher than expected. Central heating systems are hydraulically unstable because heat in apartments is regulated emotionally, exceeding the regulated operating mode. The domestic hot water supply systems low energy efficiency causes relatively large thermal energy losses in hot water distribution and in circulation pipelines. The project was implemented in 2014; after three heating seasons of operation data monitoring, fixation of project deficiency and correction of solutions were carried out. According to the operation data monitoring, this innovative system is the most functional and energy efficient, corresponding to installed requirements of the project. After the assembly was completed the system was tuned to work in calculation mode and put into operation. During operation while heat consumption regime is changing, the functional efficiency does not change. Apartment heating system heat output is automatically regulated according to the room temperature. Preparation of hot water is provided in every apartment`s boiler capacity (in local space heaters) with the combined heating system heat transmission at 70 ° C temperature. It provides hot water heating to 60°C close to the final user and prevents the growth of microorganisms in hot water distribution system pipelines of the end user.
System impact of energy efficient building refurbishment within a district heated region
Energy, 2016
The energy efficiency of the European building stock needs to be increased in order to fulfill the climate goals of the European Union. To be able to evaluate the impact of energy efficient refurbishment in matters of greenhouse gas emissions, it is necessary to apply a system perspective where not only the building but also the surrounding energy system is taken into consideration. This study examines the impact that energy efficient refurbishment of multi-family buildings has on the district heating and the electricity production. It also investigates the impact on electricity utilization and emissions of greenhouse gases. The results from the simulation of four energy efficiency building refurbishment packages were used to evaluate the impact on the district heating system. The packages were chosen to show the difference between refurbishment actions that increase the use of electricity when lowering the heat demand, and actions that lower the heat demand without increasing the electricity use. The energy system cost optimization modeling tool MODEST (Model for Optimization of Dynamic Energy Systems with Time-Dependent Components and Boundary Conditions) was used. When comparing two refurbishment packages with the same annual district heating use, this study shows that a package including changes in the building envelope decreases the greenhouse gas emissions more than a package including ventilation measures.
Energy, 2018
Flores et al. [14] also developed a model for the assessment of techno-economic impact of lowtemperature subnet in conventional district heating networks. The study explored the benefits of connecting newly built and/or refurbished old buildings (with lowered heat demand) to conventional (3 rd generation) district heating systems via low-temperature district heating system. Techno-economic analysis was used to estimate annual district heating operating costs and revenues achieved by the reduction in network return temperatures (and thus reduced network heat losses and primary fuel use). A numerical thermodynamic network model was developed by the authors in Matlab/Simulink environment, which was then solved by the software internal optimization algorithms. The model was applied on a Swedish district heating network, previously studied by Johansson et al. [15]. The studied system supplies 82GWh of heat on an annual level, of which 13% are distribution heat losses. Additionally, the study considered renovation of the existing building stock supplied by the network, and the impact of consequent heat demand reduction on district heating network operational parameters. However, since the focus of the study was on network and substation modelling, building heat demand and the reductions after the envelope renovations were not simulated but rather adopted from the bibliography. The authors concluded that due to assumed decrease (of 15%) in heat demand, caused by the building renovation measures, the number of operating hours for fossil-fueled peak load units decreased, which was considered beneficial (considering the marginal fuel costs and greenhouse gas emissions). However, it also increased the number of operating hours for the heat boiler used when the heat demand is too low for the base load unit. Finally, the authors concluded that due to the combination of savings and the additional revenue, the costs of heat supply relative to the total demand still decreased (despite the heat demand reductions). Tańczuk et al. [16] conducted a study on energy and economic optimization of repowering (substitution of heat production source) of coal-fired municipal district heating source. The authors developed a thermodynamic model of a repowered heat plant, which was supplemented by the economic model (the authors presented within the publication all the equations used for both models). In this particular study, the authors considered the substitution of a coal-fired heat source with a CHP (Combined Heat and Power) unit. The optimization algorithm was based on the configuration of existing heat plant in Opole, Poland, in which two coal-fired boilers were substituted with a gas turbine and waste heat recovery CHP system. The results of
Environmental impact of energy refurbishment of buildings within different district heating systems
Applied Energy, 2017
h i g h l i g h t s Energy refurbishment of a multi-family house within a district heating system. Changes in purchased energy, primary energy use and CO 2 emissions are analyzed. Four energy refurbishment packages and four district heating systems are included. Purchased energy savings are not correlated to the change in environmental impact. It is more important to reduce electricity use than heating demand.
District heating cost modelling
CERN European Organization for Nuclear Research - Zenodo, 2022
disclosed to third parties without the written consent of the RELaTED partners, except as mandated by the European Commission contract, for reviewing and dissemination purposes. All trademarks and other rights on third party products mentioned in this document are acknowledged and owned by the respective holders. The information contained in this document represents the views of RELaTED This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 768567 LIMITATIONS OF CURRENT DH NETWORKS DH systems were designed many decades ago. In most cases, they are designed and operated to distribute heat at about 80°C to consumers. Their capacity to reduce operational temperatures is related to radiator capacity to deliver sufficient heat to meet comfortable temperatures in buildings and to allow for the safe preparation of domestic hot water (DHW) preparation. DHW limits potential temperature reductions due to the need to avoid legionella-related issues. Depending on specific national regulations, storage temperatures in the range of 55-75ºC are prescribed. OVERALL RELATED CONCEPT RELaTED pursues the development of DH networks with service temperature levels as low as 40-50ºC. In many alternatives, traditional DHW preparation methods are substituted by "innovative methods". In these concepts, mains water is primarily heated by the DH, and then complemented by electric heaters/boosters up to the required temperature levels. In more advanced alternatives, heat pumps are used for such purposes.
Energy Procedia, 2014
With the adoption of the recast EPBD in 2010, EU Member States faced new tough challenges, moving towards new and retrofitted nearly-zero energy buildings by 2020 and the application of a cost-optimal methodology for setting minimum requirements for both the envelope and the technical systems. Attention often is focused on building envelope technologies however nowadays technical systems can be a powerful instrumental factor in achieving high levels of energy efficiency. Thermal systems producing heating and cooling have higher investment costs but it is possible to demonstrate that in a long term they are cost effective related with traditional high efficient technologies. Refurbishment and energy retrofitting in residential buildings is frequently approached with standard and traditional technologies preventing the penetration of different but already consolidated solutions. The paper shows the technical and economical comparison between three technical systems (gas boiler, ASHP and GSHP) as option to replace an oil boiler after a whole refurbishment of an apartment residential building in Milan, Italy. The retrofitting of the envelope was standard nevertheless the most innovative choice was on thermal system.
Sustainable Cities and Society, 2021
Renovation at district scale is a key strategy to reduce CO 2 emissions and energy consumptions by optimising the implementation of renewable energy sources and taking advantage of economies of scale. In this context, this paper focuses on assessing the positive impacts and difficulties after the energy rehabilitation of thermal envelopes in two buildings that belong to two different District Heating systems. The methodology is based on the comparative analysis of indoor temperatures data and energy consumption data of 17 monitored dwellings. The results showed a significant association between the improvement of envelopes and the increase of indoor temperatures in winter (β=0,644). Due to some technical and social barriers, the heating system was not regulated after the rehabilitation, so energy consumption was unnecessarily high, there were situations of indoor overheating in winter (maximum average indoor temperatures between 24-26 • C) and these issues produced dissatisfaction on neighbours. In order to avoid these negative consequences, some recommendations are provided, such as informing neighbours about expectations in each step of the long rehabilitation process, reconsidering payments to promote the envelope rehabilitation but maintaining a fixed cost to protect vulnerable groups, and promoting post-occupational studies that contribute to the viability and update of this kind of District Heating systems.