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Unified thermodynamic model to calculate COP of diverse sorption heat pump cycles: Adsorption, absorption, resorption, and multistep crystalline reactions
Building Energy Research Center, Department of Building Science, Tsinghua University, Beijing, China; Oak Ridge National Laboratory, Building Equipment Research, Energy & Transportation Science Division, Oak Ridge, United States.
Oak Ridge National Laboratory, Building Equipment Research, Energy & Transportation Science Division, Oak Ridge, United States.
Lyle School of Civil Engineering, Purdue University, West Lafayette, United States.
Mälardalen University, School of Business, Society and Engineering, Future Energy Center. SaltX Technology AB, Stockholm, Sweden; Dalarna University, Borlänge, Sweden.ORCID iD: 0000-0002-1203-3016
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. Vol. 99, p. 382-392
Keywords [en]
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: urn:nbn:se:mdh:diva-42697DOI: 10.1016/j.ijrefrig.2018.12.021ISI: 000461334900038Scopus ID: 2-s2.0-85060929731OAI: oai:DiVA.org:mdh-42697DiVA, id: diva2:1289023
Available from: 2019-02-15 Created: 2019-02-15 Last updated: 2020-10-22Bibliographically approved
In thesis
1. Evaluation of Modular Thermally Driven Heat Pump Systems
Open this publication in new window or tab >>Evaluation of Modular Thermally Driven Heat Pump Systems
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
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:nbn:se:mdh:diva-49197 (URN)978-91-7485-472-5 (ISBN)
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

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