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Heat Pump System in Existing Building Stock

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "G: Energy and Buildings".

Deadline for manuscript submissions: closed (31 December 2023) | Viewed by 14065

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Dr. Marek Miara

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Guest Editor

Business Developer Heat Pumps, Division Thermal Systems and Building Technologies, Fraunhofer Institute for Solar Energy Systems ISE, 79110 Freiburg, Germany
Interests: heat pumps; energy transition; natural refrigerants; efficiency of heat pumps; multi family buildings; existing building stock

Special Issue Information

Dear Colleagues,

It is our pleasure to invite you to submit a paper for publication in a Special Issue of Energies on the topic of "Heat Pump System in Existing Building Stock".

The common view that heat pumps are only suitable for new buildings or for buildings that have undergone extensive energetical refurbishment can be considerecd disproved in many respects today.

This view is particularly inappropriate because it is crucial that existing buildings achieve climate neutrality in the future. Most residential spaces are still heated with fossil fuels to this day. In the next two to three decades, these homes will also have to be completely supplied by CO₂-free heating. Alongside CO₂-free district heating, the heat pump is a key technology that will be used here.

The more studies, scenarios, and forecasts describe an important or even decisive role of heat pumps in decarbonizing the building sector, the more often the following questions arise: How can heat pumps be used in existing buildings? Do all existing buildings need to be extensively retrofitted first? Are heat pumps able to guarantee the high flow temperatures required? Can heat pumps in existing buildings achieve reasonable efficiency values? Is the operation of heat pumps in existing buildings ecologically beneficial?

Various research results have clearly shown that heat pumps can provide necessary heat even in unrefurbished or only slightly refurbished existing buildings, while being efficient enough to achieve clear ecological advantages over fossil-fuelled boilers.

The goal of this Special Issue on “Heat Pump System in Existing Building Stock” is to provide well-founded answers to these and other questions, counter prejudices, and create a good basis for future decision making in this area.

Dr. Marek Miara
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

heat pumps
existing building stock
retrofitting
energy and buildings
energy transition
CO₂ goals

Published Papers (7 papers)

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Research

33 pages, 12773 KiB

Open AccessArticle

Using Artificial Neural Networks to Gather Intelligence on a Fully Operational Heat Pump System in an Existing Building Cluster

by Fredrik Skaug Fadnes, Reyhaneh Banihabib and Mohsen Assadi

Energies 2023, 16(9), 3875; https://0-doi-org.brum.beds.ac.uk/10.3390/en16093875 - 03 May 2023

Viewed by 1642

Abstract

The use of heat pumps for heating and cooling of buildings is increasing, offering an efficient and eco-friendly thermal energy supply. However, their complexity and system integration require attention to detail, and minor design or operational errors can significantly impact a project’s success. Therefore, it is essential to have a thorough understanding of the system’s intricacies and demands, specifically detailed system knowledge and precise models. In this article, we propose a method using artificial neural networks to develop heat pump models from measured data. The investigation focuses on an operational heat pump plant for heating and cooling a cluster of municipal buildings in Stavanger, Norway. The work showcases that the network configurations can provide process insights and knowledge when detailed system information is unavailable. Model A predicts the heat pump response to temperature setpoint and inlet conditions. Except for some challenges during low-demand cooling mode, the model predicts outlet temperatures with Mean Absolute Percentage Error (MAPE) between 2 and 5% and energy production and consumption with MAPE below 10%. Summarizing the five-minute interval predictions, the model predicts the hourly energy production and consumption with MAPE at 3% or less. Model B predicts energy consumption and coefficient of performance (COP) from measured inlet and outlet conditions with MAPE below 5%. The model may serve as a tool to develop system-specific compressor maps for part-load conditions and for real-time performance monitoring. Full article

(This article belongs to the Special Issue Heat Pump System in Existing Building Stock)

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22 pages, 3415 KiB

Open AccessArticle

Integration of Back-Up Heaters in Retrofit Heat Pump Systems: Which to Choose, Where to Place, and How to Control?

by Fabian Wüllhorst, Christian Vering, Laura Maier and Dirk Müller

Energies 2022, 15(19), 7134; https://0-doi-org.brum.beds.ac.uk/10.3390/en15197134 - 28 Sep 2022

Cited by 2 | Viewed by 1597

Abstract

Back-up heaters are essential for sustainable retrofit heat pump systems to achieve low capital costs and high system temperatures. Despite its importance, current literature focuses primarily on single aspects of the interaction between the back-up heater and the heat pump system. Furthermore, influences of varying scenarios are typically not considered. This paper simultaneously investigates the impact of 18 different scenarios on the optimal answer to the questions: Which back-up heater to choose, where to place it, and how to control it? A scenario consists of boundary conditions for weather, building envelope, radiator sizing, operational envelope, and the electricity-to-gas price/emission ratio, respectively. Using annual dynamic Modelica simulations, we evaluate and assess all interdependencies based on a full factorial design. We analyze final energy consumption, thermal comfort, and back-up heater as objectives. For gas-fired back-up heaters, the optimal placement and control align with current state-of-the-art recommendations. However, for electric back-up heaters, current guideline recommendations yield up to 30% higher operational costs and emissions compared to our findings. Consequently, future studies should develop optimal design rules for sustainable retrofit heat pump systems. Full article

(This article belongs to the Special Issue Heat Pump System in Existing Building Stock)

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29 pages, 3028 KiB

Open AccessArticle

Analysis of the Operation Characteristics of a Hybrid Heat Pump in an Existing Multifamily House Based on Field Test Data and Simulation

by Daniel Neubert, Christian Glück, Julian Schnitzius, Armin Marko, Jeannette Wapler, Constanze Bongs and Clemens Felsmann

Energies 2022, 15(15), 5611; https://0-doi-org.brum.beds.ac.uk/10.3390/en15155611 - 02 Aug 2022

Cited by 4 | Viewed by 1884

Abstract

Unrenovated multifamily houses in Germany are mostly heated by fossil heat generators; therefore, measures are required for CO₂ emission reduction. The use of air–water heat pumps is restricted by high required flow temperatures and heat output but can be mitigated by hybrid heat pumps. To limit additional operation costs by the heat pump, a new operation strategy is introduced in this study, which allows to maintain a target CO₂ emission. The operation strategy is applied in a field trial in a small unrenovated multifamily house built in 1964. A thermohydraulic simulation model is verified and is used in full-year simulations to apply improvement measures and compare the new control strategy with existing optimizing strategies. The results show that the control onto target emissions is possible and limits additional costs but can also result in higher CO₂ mitigation costs, making it less favorable. The hybrid heat pump reduces the direct fossil CO₂ emissions by 61% (in total by 22%); thus, it is a relevant solution for multifamily houses, especially within a further decarbonized electrical grid. Full article

(This article belongs to the Special Issue Heat Pump System in Existing Building Stock)

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25 pages, 1031 KiB

Open AccessArticle

Supporting Multi-Attribute, Non-Compensating Selection of the Right Heat Pump Device for a Residential Building, Considering the Limited Availability of the Necessary Resources

by Grzegorz Ginda, Natalia Iwaszczuk and Marek Dudek

Energies 2022, 15(15), 5478; https://0-doi-org.brum.beds.ac.uk/10.3390/en15155478 - 28 Jul 2022

Cited by 1 | Viewed by 1190

Abstract

Reliable and comprehensive choice of a suitable domestic heat pump for a common dwelling house is discussed in the paper. The application of common and freely available market information about possible heat pump options is considered in this regard. The intangibility, imperfect nature, and overload of available information, as well as a common issue amongst interested homeowners—scarce critical resource availability, e.g., financial means—are also dealt with. A specific, universal multistage decision support procedure is proposed in the paper to help a houseowner to make an informed heat pump choice. At first, a concept of a pairwise comparison and a notion of dominance under imperfect information are utilized to build a kind of option hierarchy. A particular heat pump device is then recommended by means of exploring consecutive option hierarchy levels and an actual houseowner’s critical resource capacity in a non-commensurable manner. It seems that this joint application of common imperfect information about available options and critical resource availability, as well as the ideas of option dominance and non-commensurability, make the approach an interesting way for a casual homeowner to make an informed heat pump device choice. A sample analysis is also applied to show the merits and the usefulness of the approach in the paper. Full article

(This article belongs to the Special Issue Heat Pump System in Existing Building Stock)

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29 pages, 12120 KiB

Open AccessFeature PaperArticle

Large Air-to-Water Heat Pumps for Fuel-Boiler Substitution in Non-Retrofitted Multi-Family Buildings—Energy Performance, CO₂ Savings, and Lessons Learned in Actual Conditions of Use

by Omar Montero, Pauline Brischoux, Simon Callegari, Carolina Fraga, Matthias Rüetschi, Edouard Vionnet, Nicole Calame, Fabrice Rognon, Martin Patel and Pierre Hollmuller

Energies 2022, 15(14), 5033; https://0-doi-org.brum.beds.ac.uk/10.3390/en15145033 - 10 Jul 2022

Cited by 6 | Viewed by 2499

Abstract

The use of air source heat pumps (ASHP) in the specific context of existing multi-family buildings (MFB) represents an important challenge, especially in terms of performance and technical constraints in real conditions of use. This study concerns the actual performance of two non-retrofitted MFB (4047 and 7563 m²), whose original fossil heat supply was replaced by a centralized monovalent (2 × 156 kW) and hybrid (6 × 34 kW) ASHP system for space heating and domestic hot water. Based on a detailed monitoring campaign covering two years of operation, it can be concluded that both systems are able to supply the required temperature and cover the entire heat demand. By closely following up these pilot projects, constraints linked to integration and operation were identified. Optimization measures allowed us to increase the COP of the monovalent system (from 1.3 up to 3.4, with an optimized SPF of 2.3) and to raise the HP share of the hybrid system (from 50% to 67%, with an optimized SPF of 2.3). Both systems offer major progress in terms of CO₂ savings (92% and 68%) and increased renewable energy share (75% and 43%), considering the hourly CO₂ content of the Swiss electricity mix. Full article

(This article belongs to the Special Issue Heat Pump System in Existing Building Stock)

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16 pages, 5739 KiB

Open AccessArticle

Exergy Efficiency and COP Improvement of a CO₂ Transcritical Heat Pump System by Replacing an Expansion Valve with a Tesla Turbine

by Abbas Aghagoli, Mikhail Sorin and Mohammed Khennich

Energies 2022, 15(14), 4973; https://0-doi-org.brum.beds.ac.uk/10.3390/en15144973 - 07 Jul 2022

Cited by 1 | Viewed by 1892

Abstract

The heat pump system has been widely used in residential and commercial applications due to its attractive advantages of high energy efficiency, reliability, and environmental impact. The massive exergy loss during the isenthalpic process in the expansion valve is a major drawback of the heat pump system. Therefore, the Tesla turbine exergy analysis in terms of transiting exergy efficiency is investigated and integrated with the transcritical heat pump system. The aim is to investigate the factors that reduce exergy losses and increase the coefficient of performance and exergy efficiency. The contribution of this paper is twofold. First, a three-dimensional numerical analysis of the supercritical CO₂ flow simulation in the Tesla turbine in three different geometries is carried out. Second, the effect of the Tesla turbine on the coefficient of performance and exergy efficiency of the heat pump system is investigated. The effect of the rotor speed and disk spacing on the Tesla turbine power, exergy loss, and transiting exergy efficiency is investigated. The results showed that at a lower disk spacing, the turbine produces higher specific power and transiting exergy efficiency. In addition, the coefficient of performance (COP) and exergy efficiency improvement in the heat pump system combined with the Tesla turbine are 9.8% and 28.9% higher than in the conventional transcritical heat pump system, respectively. Full article

(This article belongs to the Special Issue Heat Pump System in Existing Building Stock)

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30 pages, 8864 KiB

Open AccessArticle

Compact Decentral Façade-Integrated Air-to-Air Heat Pumps for Serial Renovation of Multi-Apartment Buildings

by Fabian Ochs, William Monteleone, Georgios Dermentzis, Dietmar Siegele and Christoph Speer

Energies 2022, 15(13), 4679; https://0-doi-org.brum.beds.ac.uk/10.3390/en15134679 - 26 Jun 2022

Cited by 5 | Viewed by 1933

Abstract

To address the huge market of renovation of multi-apartment buildings, minimal-invasive decentral serial-renovation solutions are required. One major challenge in the design of decentral heat pumps is to find the optimal balance between, on one hand, compactness and pleasant design, and on the other hand, efficiency and minimal sound emissions. A comprehensive holistic design and optimization process for the development of decentral heat pumps, from the component level, to the system level, and up to the building level, is developed. A novel façade-integrated speed-controlled exhaust air to supply air heat pump combined with a mechanical ventilation system with heat recovery and recirculation air was developed and simulated in a reference flat. Compared to a traditional supply air heat pump without recirculation, it shows only slight performance improvement, but allows significantly better thermal comfort and control, independently from the hygienic air flow rate and from the heating and cooling loads. Detailed measurement and simulation results are presented for several functional models with heating power of around 1 kW up to 2.5 kW. The design was optimized by means of CFD simulations to allow for low pressure drop, homogeneous flow, and low sound emissions. Moreover, mock-ups of innovative façade-integrated heat pump outdoor units are presented. Full article

(This article belongs to the Special Issue Heat Pump System in Existing Building Stock)

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