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Solar integrated heating systems: Applications in buildings and industries
Dalarna University, School of Information and Engineering, Energy Technology. Uppsala universitet, Byggteknik och byggd miljö.
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

“Heat is half” of the global final energy consumption, and the decarbonization of the heating sector is critical to achieving climate goals. This thesis employs a system modelling approach to evaluate renewable heating systems. The overarching goal is to reduce fossil fuel reliance by integrating renewable energy technologies, such as solar thermal, photovoltaics, photovoltaic thermal, heat pump, and thermal energy storage in different system concepts. Two primary sectors are addressed: buildings, with a focus on utilizing solar collectors and heat pumps for heating systems in multifamily houses by recovery of waste heat; and industries, utilizing solar collectors for steam generation below 200 °C. The work is centred around five primary research questions, addressing the technical and economic feasibility of the mentioned technologies and their roles in decarbonization.

Two system arrangements were simulated to address the heating demands of buildings: a) Centralized heat pump that utilizes ventilation air as a heat source, serving three multifamily buildings, and b) A fifth generation district heating system that utilizes industrial waste heat as its source. The techno-economic performance of these systems was evaluated. The results suggest that the economic viability of such arrangements largely depends on critical factors that include the costs of heat pump sub-stations, prevailing electricity prices, and the cost of waste heat. Incorporating solar air heating collectors and optimizing flow controls enhance both component and system energy efficiency. Moreover, integrating photovoltaic systems, up to a specific capacity, is advantageous as it offers reductions in heating costs.

For industrial steam generation, the importance of the solar fraction in technological comparisons is highlighted. Parabolic trough collector and heat pump for steam generation are compared for 34 locations in the European Union, using solar fraction as an indicator. The results highlight the economic competitiveness of both technologies for a wide range of boundary conditions. However, heating costs from solar thermal collectors increase at higher solar fractions, primarily due to the storage costs. This trend sets an economic limit on the maximum feasible solar fraction. As a result, hybrid systems combining solar thermal collectors with steam heat pumps offer a promising combination to achieve a high renewable fraction for industrial applications.

Concerns about CO2 emissions from the electricity grid, and its reliability in many countries, necessitate the exploration of alternative system concepts to meet a higher fraction of heating demand. One such novel energy system combines a parabolic trough collector, photovoltaic, and thermal energy storage (using water and sand as storage media) to reach a combined solar fraction of 90 %, while remaining cost-competitive with fossil fuels. The techno-economic performance of solar thermal collectors is system dependent, largely influenced by their integration within industrial systems. Two novel indicators are introduced to quantify the integration incompatibilities, offering insights into the dynamics for specific integration point. Using this method for a case study resulted in an optimized configuration, improving the overall system performance.

Collectively, the results are expected to be leveraged by relevant stakeholders to advance the cause of heating decarbonization in buildings and industries.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2023. , p. 137
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2316
Keywords [en]
Solar heating systems, Renewable heating systems, Decarbonization, Solar thermal, Techno-economic analysis, Thermal energy storage.
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:du-47224ISBN: 978-91-513-1914-8 (print)OAI: oai:DiVA.org:du-47224DiVA, id: diva2:1810204
Public defence
2023-11-23, 310, Dalarna university, Borlänge, 13:00 (English)
Opponent
Supervisors
Available from: 2023-11-07 Created: 2023-11-07 Last updated: 2023-11-07Bibliographically approved
List of papers
1. Techno-economic analysis of an exhaust air heat pump system assisted by unglazed transpired solar collectors in a Swedish residential cluster
Open this publication in new window or tab >>Techno-economic analysis of an exhaust air heat pump system assisted by unglazed transpired solar collectors in a Swedish residential cluster
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2021 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 224, p. 966-983Article in journal (Refereed) Published
Abstract [en]

Solar heating technologies hold a significant potential to supplement or replace the fossil fuel-driven heating systems in residential and industrial applications. This paper presents a techno-economic study aiming to assess the use of Unglazed Transpired Solar Collectors (UTSC) coupled with an energy system assisted by Exhaust Air Heat Pump (EAHP) in cold climates applied to a residential building cluster. The performance of the system and its components is assessed for different sizes of solar collector field. In addition, a rule-based algorithm is developed to manage the airflow into the UTSC, and a comparative analysis is carried out with conventional flow control. The existing EAHP assisted energy system of a multifamily building cluster in Sweden is modelled by using a simulation software TRNSYS, and the effects of the UTSCs integration on the performances of the energy system are evaluated. Results show that the integration of UTSCs has a small but positive impact on the overall system performance. Moreover, the developed control based on the variation of the collector airflow rate for UTSC is an effective control strategy to increase the seasonal performance factor of the overall system and to maximize the savings.

Keywords
Transpired solar collector, Exhaust air heat pump, Techno-economic analysis, Solar heat pump, System analysis
National Category
Energy Engineering
Identifiers
urn:nbn:se:du-37704 (URN)10.1016/j.solener.2021.06.026 (DOI)000681521300004 ()2-s2.0-85109203250 (Scopus ID)
Projects
Energy matchingEST project: Efficient Solar Roof Tops
Available from: 2021-07-08 Created: 2021-07-08 Last updated: 2023-11-07Bibliographically approved
2. Techno-economic assessment of a novel hybrid system of solar thermal and photovoltaic driven sand storage for sustainable industrial steam production
Open this publication in new window or tab >>Techno-economic assessment of a novel hybrid system of solar thermal and photovoltaic driven sand storage for sustainable industrial steam production
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2023 (English)In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 292, article id 117414Article in journal (Refereed) Published
Abstract [en]

Decarbonising industrial heat is a significant challenge due to various factors such as the slow transition to renewable technologies and insufficient awareness of their availability. The effectiveness of commercially available renewable heating systems is not well defined in terms of techno-economic boundaries. This study presents a techno-economic assessment of a novel system designed for steam production at a food and beverage plant. The proposed system is combines parabolic trough collectors with pressurized water thermal storage and photovoltaic-driven high-temperature sand storage. The technological components within the hybrid system complements each other both economically and practically, resulting in cost and land area savings. To evaluate the proposed system, simulations were performed using a model developed in TRNSYS and Python. The combined system exhibits better economic and land use performance than when these technologies are used individually. Specifically, the system has a high solar fraction of 90% while remaining competitive with the existing boiler fuel cost. The study emphasizes the importance of multi-technology approaches in developing practical solutions for industrial heat decarbonization. The findings can guide industries in a transition to sustainable heat sources and contribute to global efforts in mitigating climate change.

National Category
Energy Engineering
Identifiers
urn:nbn:se:du-46464 (URN)10.1016/j.enconman.2023.117414 (DOI)001039354600001 ()2-s2.0-85172667530 (Scopus ID)
Available from: 2023-07-17 Created: 2023-07-17 Last updated: 2023-11-07Bibliographically approved
3. Techno-economic analysis of a 5th generation district heating system using thermo-hydraulic model: A multi-objective analysis for a case study in heating dominated climate
Open this publication in new window or tab >>Techno-economic analysis of a 5th generation district heating system using thermo-hydraulic model: A multi-objective analysis for a case study in heating dominated climate
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2023 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 296, article id 113347Article in journal (Refereed) Published
Abstract [en]

A 5th generation district heating (5GDH) system consists of a low-temperature network used as a heat source for de-centralized heat pumps to serve heating demand. Until now, there is a lack of studies looking into the economic aspect of implementing the 5GDH concept. The performance characteristics, system dynamics, and economic feasibility of the 5GDH system are insufficiently investigated in cold climates. This paper aims to bridge the research gap by performing the techno-economic analysis of a 5GDH system using a case study based in Tallinn, Estonia. A detailed thermo-hydraulic simulation model is constructed in TRNSYS and Fluidit Heat. In addition, the uncertainty and sensitivities on the economic performance are analysed using Monte Carlo method implemented in Python. The study further analyses the effectiveness of using solar power technologies in reducing the cost of heating. For designed boundary conditions, the system can deliver heat at levelised cost of heating (LCOH) of 80 €/MWh. Integration of photovoltaic up to a limited capacity results in 1 % reduction when compared to the base case LCOH. The economic benefit of photovoltaic thermal is lower compared to photovoltaic. This study can provide a benchmark for the application of 5GDH systems in heating dominated regions.

Keywords
5GDHC; Techno-economic analysis; Monte Carlo analysis; PV; PVT
National Category
Energy Engineering
Identifiers
urn:nbn:se:du-46441 (URN)10.1016/j.enbuild.2023.113347 (DOI)001046454200001 ()2-s2.0-85164720487 (Scopus ID)
Available from: 2023-07-13 Created: 2023-07-13 Last updated: 2023-11-07Bibliographically approved
4. Techno-economic comparative analysis of solar thermal collectors and high-temperature heat pumps for industrial steam generation
Open this publication in new window or tab >>Techno-economic comparative analysis of solar thermal collectors and high-temperature heat pumps for industrial steam generation
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2023 (English)In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 277, article id 116623Article in journal (Refereed) Published
Abstract [en]

Industrial heat production is responsible for around 20% of total greenhouse gas emissions in Europe. To achieve the climate change goals defined in the Paris Climate Agreement, the EU commission has shifted its focus on sustainable means to generate heating. Moreover, global dependencies are leading to a re-organization of natural gas supplies. Therefore, there is a need for less vulnerable and less price-volatile solutions for heating. This paper focuses on two decarbonization technologies for industrial process heat supply: a) electricity-driven steam-generating high-temperature heat pumps (HTHP), a technology that is more efficient than fossil fuel boilers in generating steam, and b) solar parabolic trough collector (PTC), which can produce heat economically and at a minimal carbon footprint compared to other technologies. The main aim of this paper is to evaluate the levelized cost of heat (LCOH) of these technologies to fulfill a comparative techno-economic analysis. A maximum PTC collector's solar fraction limit (SFlimit) is defined to indicate when the LCOH for these two technologies is equal. This allows for distinguishing between the economic stronghold of each technology. The evaluation is carried out through the annual energy simulations using TRNSYS and Excel spreadsheets for HTHPs, while TRNSED and OCTAVE are used for the solar thermal part. Boundary conditions for European geographical constraints have been applied to establish use cases for the analysis. The result shows that the design of a PTC system with optimal SF can reach cost parity with HTHP for most of the analyzed locations. The developed methodology serves as a valuable guide to quickly determine a preferred lower carbon heat solution, thus easing the decision-making for industries

National Category
Energy Systems
Identifiers
urn:nbn:se:du-44979 (URN)10.1016/j.enconman.2022.116623 (DOI)000921273200001 ()2-s2.0-85145687377 (Scopus ID)
Available from: 2023-01-05 Created: 2023-01-05 Last updated: 2023-11-07Bibliographically approved
5. A novel method for assessing the techno-economicalcompatibility of solar thermal integrations
Open this publication in new window or tab >>A novel method for assessing the techno-economicalcompatibility of solar thermal integrations
2022 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

In this work we present a method to evaluate the compatibility of a solar thermal integration in an industrial process. We introduce two indicators to quantify in a comprehensive way all the financial and technicalboundaries influence on the design choices and on the costs of a solar thermal integration.Both the indicators are measures of the divergence of an integration from a fictive (yet technically possible)ideal case and from a “do-nothing” case. In this way, the incompatibilities of the integration are associated tothe consequences that the non-ideal factors have on both costs and performances. Moreover, the value of the indicators is normalized between a minimum and a maximum being the “do-nothing” and the ideal cases respectively.We then used these indicators on a real case scenario to compare the pros and cons of two different solarthermal integration approaches (hot water vs steam) to a beer brewery in southern Europe.The results show that retrofitting part of the existing appliance to be fed with hot water rather than steamenhances the compatibility of solar thermal with the brewery. Nevertheless, we measured no relevant improvement to the compatibility of solar thermal when designing a brewery from scratch with the same characteristics but were the solar thermal system could have been integrated “ad-hoc” rather than retrofitted

Keywords
solar thermal integration, compatibility, low pressure industries, brewery
National Category
Energy Engineering
Identifiers
urn:nbn:se:du-42956 (URN)
Conference
Eurosun 2022
Available from: 2022-10-28 Created: 2022-10-28 Last updated: 2023-11-07Bibliographically approved

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Citation style
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Output format
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