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Evaluation of Modular Thermally Driven Heat Pump Systems
Mälardalen University, School of Business, Society and Engineering, Future Energy Center. (Reesbe)ORCID iD: 0000-0002-1203-3016
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The building sector accounts for approximately 40% of primary energy use within the European Union, therefore reductions in the energy use intensity of this sector are critical in decreasing total energy usage. Given that the majority of energy used within the built environment is for space conditioning and domestic hot water preparation, prudence would suggest that decreasing primary energy used for these end purposes would have the biggest overall environmental impact. A significant portion of the energy demands in buildings throughout the year could potentially be met using solar energy technology for both heating and cooling. Additionally, improving the efficiency of current heating and cooling appliances can reduce environmental impacts during the transition from non-renewable to renewable sources of energy. However, in spite of favourable energy saving prospects, major energy efficiency improvements as well as solar heating and cooling technology are still somewhat underutilised. This is typically due to higher initial costs, and lack of knowledge of system implementation and expected performance.

 

The central premise of this thesis is that modular thermally (i.e., sorption) driven heat pumps can be integrated into heating and cooling systems to provide energy cost savings. These sorption modules, by virtue of their design, could be integrated directly into a solar thermal collector. With the resulting sorption integrated collectors, cost-effective pre-engineered solar heating and cooling system kits can be developed. Sorption modules could also be employed to improve the efficiency of natural gas driven boilers. These modules would effectively transform standard condensing boilers into high efficiency gas-driven heat pumps that, similar to electric heat pumps, make use of air or ground-source heat.

 

Based on the studies carried, sorption modules are promising for integration into heating and cooling systems for the built environment generating appreciable energy and cost-savings. Simulations yielded an annual solar fraction of 42% and potential cost savings of €386 per annum for a sorption integrated solar heating and cooling installation versus a state-of-the-art heating and cooling system. Additionally, a sorption integrated gas-fired condensing boiler yielded annual energy savings of up to 14.4% and corresponding annual energy cost savings of up to €196 compared to a standard condensing boiler.

 

A further evaluation method for sorption modules, saw the use of an artificial neural network (ANN) to characterise and predict the performance of the sorption module under various operating conditions. This generic, application agnostic model, could characterise sorption module performance within a ± 8% margin of error. This study thus culminates in the proposal of an overall systematic evaluation method for sorption modules that could be employed for various applications based on the analytical, experimental and simulation methods developed.

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2020.
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 316
Keywords [en]
sorption heat pump, sorption module, thermochemical energy storage, artificial neural network, built environment, solar energy, gas-driven heat pump, solar cooling, heating and cooling, renewable energy, energy efficiency, experimental, simulation, analytical
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-49197ISBN: 978-91-7485-472-5 (print)OAI: oai:DiVA.org:mdh-49197DiVA, id: diva2:1448651
Public defence
2020-09-08, Dalarna University, Borlänge, 09:15 (English)
Opponent
Supervisors
Available from: 2020-06-30 Created: 2020-06-29 Last updated: 2022-11-08Bibliographically approved
List of papers
1. Unified thermodynamic model to calculate COP of diverse sorption heat pump cycles: Adsorption, absorption, resorption, and multistep crystalline reactions
Open this publication in new window or tab >>Unified thermodynamic model to calculate COP of diverse sorption heat pump cycles: Adsorption, absorption, resorption, and multistep crystalline reactions
2019 (English)In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 99, p. 382-392Article in journal (Refereed) Published
Abstract [en]

A straightforward thermodynamic model is developed in this work to analyze the efficiency limit of diverse sorption systems. A method is presented to quantify the dead thermal mass of heat exchangers. Solid and liquid sorbents based on chemisorption or physical adsorption are accommodated. Four possible single-effect configurations are considered: basic absorption or adsorption (separate desorber, absorber, condenser, and evaporator); separate condenser/evaporator (two identical sorbent-containing reactors with a condenser and a separate direct expansion evaporator); combined condenser/evaporator (one salt-containing reactor with a combined condenser/evaporator module); and resorption (two sorbent-containing reactors, each with a different sorbent). The analytical model was verified against an empirical heat and mass transfer model derived from component experimental results. It was then used to evaluate and determine the optimal design for an ammoniate salt-based solid/gas sorption heat pump for a space heating application. The effects on system performance were evaluated with respect to different working pairs, dead thermal mass factors, and system operating temperatures. The effect of reactor dead mass as well as heat recovery on system performance was also studied for each configuration. Based on the analysis in this work, an ammonia resorption cycle using LiCl/NaBr as the working pair was found to be the most suitable single-effect cycle for space heating applications. The maximum cycle heating coefficient of performance for the design conditions was 1.50 with 50% heat recovery and 1.34 without heat recovery. 

Place, publisher, year, edition, pages
Elsevier Ltd, 2019
Keywords
Ammonia, Analytical, Dead thermal mass, Heat recovery, Resorption, Sorption heat pump, Adsorption, Evaporators, Heat pump systems, Lithium compounds, Mass transfer, Separation, Sorbents, Space heating, Thermodynamic properties, Waste heat, Waste heat utilization, Direct expansion evaporators, Heat and mass transfer models, Heating coefficients, Operating temperature, Sorption heat pumps, Thermal mass, Coefficient of performance
National Category
Energy Engineering
Identifiers
urn:nbn:se:mdh:diva-42697 (URN)10.1016/j.ijrefrig.2018.12.021 (DOI)000461334900038 ()2-s2.0-85060929731 (Scopus ID)
Available from: 2019-02-15 Created: 2019-02-15 Last updated: 2020-10-22Bibliographically approved
2. Experimental evaluation of a novel absorption heat pump module for solar cooling applications
Open this publication in new window or tab >>Experimental evaluation of a novel absorption heat pump module for solar cooling applications
2015 (English)In: Science and Technology for the Built Environment, ISSN 2374-4731, Vol. 21, no 3, p. 323-331Article in journal (Refereed) Published
Abstract [en]

Given the environmental benefits of utilizing free thermal energy sources, such as waste heat and solar energy for cooling purposes, many developments have come about in thermally driven cooling. However, there are still some barriers to the general commercialization and market penetration of such technologies that are associated with system and installation costs, complexity, and maintenance. In efforts to overcome these limitations, a novel absorption heat pump module has been developed and tested. The module comprises a fully encapsulated sorption tube containing hygroscopic salt sorbent and water as a refrigerant, sealed under vacuum, and within which there are no moving parts. The absorption module consists of two main components, one that alternately functions as an absorber or generator and other that alternates between the roles of evaporator and condenser. The module therefore operates cyclically between a cooling delivery phase and a regeneration phase. Each module has a significant energy storage capacity with cooling delivery phases ranging from 6–10 h in length with temperature lifts between 16◦C and 25◦C. The modules are optimized for integration directly into a solar thermal collector, for roof or fac¸ade installation, for daytime regeneration and night-time cooling delivery. Collector integrated modules would be completely modular maintenance-free absorption heat pumps with similar installation requirements to standard solar thermal collectors. This article describes the test method and performance characteristics of the individual absorption modules. 

National Category
Energy Engineering
Identifiers
urn:nbn:se:mdh:diva-28917 (URN)10.1080/10789669.2014.990336 (DOI)000362067900010 ()2-s2.0-84940377508 (Scopus ID)
Available from: 2015-09-11 Created: 2015-09-11 Last updated: 2020-10-22Bibliographically approved
3. Experimental Evaluation and Concept Demonstration of a Novel Modular Gas-Driven Sorption Heat Pump
Open this publication in new window or tab >>Experimental Evaluation and Concept Demonstration of a Novel Modular Gas-Driven Sorption Heat Pump
2017 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Gas-driven sorption heat pumps (GDSHPs) exhibit great possibilities in the reduction of energy use and environmental impact of heating systems that utilise natural gas. By utilising renewable thermal energy from the environment, that is, air, ground or water sources, significant reduction of primary energy use can be achieved. However, high cost, low coefficient of performance (COP) and large volume per unit thermal power produced have limited the proliferation of GDSHPs. In this work, exploiting the benefits of reversible chemical reactions in sorption systems, with no internal moving parts, noise, vibration, and a maintenance-free reactor design, two novel modular prototype sorption components were developed and evaluated experimentally. They were designed to operate as part of an intermittent cycle GDSHP to deliver heat directly to a load or to a stratified hot water store. Prototype 1 was an ammonia-salt basic sorption unit while prototype 2 was an ammonia-salt resorption unit both employing proprietary composite sorbent materials. Test results showed that the prototype 2 reactor produced a specific heating capacity of 46 W/litre at a temperature lift of 50°C yielding a COP of 1.38. Prototype 1 demonstrated higher heating capacity of 73 W/litre at a temperature lift of 70°C but exhibited lower COP of 1.10. Given its higher COP but lower temperature lift, prototype 2 could be employed in a GDSHP designed for moderate heating demands or where a ground source heat exchanger is employed as the low temperature heat source. In the case where a higher temperature lift is required, for example, for an air-source GDSHP unit then the prototype 1 design would be more applicable.

Keywords
Gas-driven sorption heat pump; sorption module; advanced sorption cycle; resorption; absorption
National Category
Engineering and Technology Energy Systems
Identifiers
urn:nbn:se:mdh:diva-49201 (URN)
Conference
12th IEA Heat Pump Conference
Available from: 2020-06-29 Created: 2020-06-29 Last updated: 2020-10-22Bibliographically approved
4. Techno-Economic Evaluation of Solar-Assisted Heating and Cooling Systems with Sorption Module Integrated Solar Collectors
Open this publication in new window or tab >>Techno-Economic Evaluation of Solar-Assisted Heating and Cooling Systems with Sorption Module Integrated Solar Collectors
2015 (English)In: INTERNATIONAL CONFERENCE ON SOLAR HEATING AND COOLING FOR BUILDINGS AND INDUSTRY, SHC 2014, 2015, Vol. 70, p. 409-417Conference paper, Published paper (Refereed)
National Category
Energy Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-26915 (URN)10.1016/j.egypro.2015.02.142 (DOI)000358196500051 ()2-s2.0-84994701956 (Scopus ID)
Conference
3rd International Conference on Solar Heating and Cooling for Buildings and Industry (SHC)
Available from: 2014-12-15 Created: 2014-12-15 Last updated: 2020-10-22Bibliographically approved
5. Study of optimal sizing for residential sorption heat pump system
Open this publication in new window or tab >>Study of optimal sizing for residential sorption heat pump system
2019 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 150, p. 421-432Article in journal (Refereed) Published
Abstract [en]

Gas-driven sorption heat pumps (GDSHP) show significant potential to reduce primary energy use, associated emissions and energy costs for space heating and domestic hot water production in residential applications. This study considered a bivalent heating system consisting of a sorption heat pump and a condensing boiler, and focuses on the optimal heating capacity of each of these components relative to each other. Two bivalent systems were considered: one based on a solid chemisorption cycle (GDSHPA), and one based on a resorption cycle (GDSHPB). Simulations of year-round space heating loads for two single-family houses, one in New York and the other Minnesota, were carried out and the seasonal gas coefficient of performance (SGCOP) calculated. The sorption heat pump's design heating capacity as a fraction of the bivalent system's total heating capacity was varied from 0 to 100%. Results show that SGCOP was effectively constant for sorption heat pump design capacity greater than 41% of the peak bivalent GDSHPA design capacity in Minnesota, and 32% for GDSHPB. In New York, these values were 42% and 34% for GDSHPA and GDSHPB respectively. The payback period was also evaluated based on postulated sorption heat pump component costs. The fastest payback was achieved with sorption heat pump design capacity between 22 and 44%.

Place, publisher, year, edition, pages
Elsevier Ltd, 2019
Keywords
Bivalent, Residential, Sizing, Sorption heat pump, Energy utilization, Gas emissions, Heat pump systems, Housing, Investments, Pumps, Sorption, Space heating, Condensing boilers, Domestic hot water, Residential application, Single-family house, Sorption heat pumps, Heating
National Category
Energy Engineering
Identifiers
urn:nbn:se:mdh:diva-43052 (URN)10.1016/j.applthermaleng.2018.12.151 (DOI)000462418200037 ()2-s2.0-85059855024 (Scopus ID)
Available from: 2019-04-10 Created: 2019-04-10 Last updated: 2020-10-22Bibliographically approved
6. Test Platform and Component Model for Modular Sorption Heat Pumps
Open this publication in new window or tab >>Test Platform and Component Model for Modular Sorption Heat Pumps
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Increasing the share of renewable sources of energy as well as the effective use of waste energy sources is critical to the reduction of primary energy use and its associated environmental impact in the built environment. Sorption heat pumps are employed in various heat-driven cooling and heat pumping applications. These heat pumps may be driven by solar energy, natural gas, biogas, geothermal energy or waste heat. Given that a plethora of heat sources and sorption materials can be exploited for different applications, various sorption heat pump modules have been developed. The sorption modules are pre-engineered sorption components for increased ease of sorption system development, improved cost effectiveness and reduced system complexity for various applications. However, in the design of sorption modules, component and system modelling and simulation are useful in the process of determining the optimal candidate of several possible sorption working couples for a given application. A test platform has been developed and a test strategy devised for the rapid characterisation of the transient behaviour of the sorption modules. In the present study, a modular sorption unit is evaluated experimentally in an automated test setup. Key performance indicators were derived, and the test data used as input to train a model based on artificial neural networks (ANN) in MATLAB. The study showed that the model could adequately predict the dynamic behaviour of the sorption module. Results showed that the dynamic behaviour of the module could be adequately mapped, with average relative errors between measured and simulation results of 3.7%, 4.2%, 0.4%, and 0.3% for heat transfer rates to and from the reactor, and the condenser-evaporator during charge and discharge respectively. Additionally, the ANN model, trained with data from test run sequence of 54 cycles, predicted both cooling and heating COPs within a reasonable margin of error (<± 8%) with the majority of predictions having an error of less than ± 4%.

Keywords
Sorption, Artificial Neural Network, Heat Pump, Sorption Module
National Category
Engineering and Technology
Identifiers
urn:nbn:se:mdh:diva-49196 (URN)
Available from: 2020-06-29 Created: 2020-06-29 Last updated: 2022-11-09Bibliographically approved

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