Increasing Building Efficiency Using Water-to-Water Heat Pumps: A Guide to Sea-Based Heat Pumps

Heat pumps are becoming an increasingly popular solution for heating and cooling, using the principle of moving heat from a generous source to a necessary sink in an efficient way [1]. Among the different types, water-to-water heat pumps stand out for their ability to extract heat from low temperature water sources and deliver it to higher temperature water streams, making them a versatile solution for residential, commercial and industrial applications [1] [2]. In particular, sea heat pumps, a category of renewable heating, use seawater to transfer heat to control the temperature of buildings, which demonstrates an innovative approach to harnessing natural resources [3] [4].

This article will discuss in detail the mechanics of water-to-water heat pumps, highlighting the seamless integration of water-to-water heat pumps into hydronic systems or with fan coil units, as well as the unique advantages of seawater-based systems [2]. By exploring the operational framework, key components, and diverse benefits including energy efficiency and environmental friendliness, readers will gain comprehensive insights into maximizing building performance with these systems [6] [7]. In addition, the real-world application, challenges and future prospects of water-to-water and marine heat pumps will be thoroughly discussed, providing a well-rounded guide to harnessing these technologies for sustainable building management. Understanding Marine Heat Pumps Understanding the efficiency and environmental benefits of marine heat pumps begins with recognizing their basic operating principles:

Efficiency factors:

1. Greater Efficiency than Air-to-Air Heat Pumps: Water-to-water (TPVV) heat pumps are generally more efficient than their air-source counterparts due to the higher density and thermal conductivity of water [8].
2. Stable Temperature Sources: The use of water sources such as the sea, which have relatively stable temperatures, improves the efficiency and performance of TPVV [8] [4].
3. Increasing Energy Efficiency: Sea heat pumps have an average energy efficiency improvement potential of 24.2%, making them a superior choice for renewable heating systems [4].

Ecological Advantages:

1. Operation No Emissions: Unlike conventional heating systems, sea heat pumps do not emit harmful gases or pollutants, which contributes to a cleaner environment [4].
2. Sustainable and Abundant: Harnessing the thermal energy of seawater, these pumps are renewable, abundant and economical solutions for heating and cooling [4].
3. Diversity in Application: Sea heat pumps are not only limited to residential buildings but also extend to commercial and industrial environments, showing their adaptability [4].

By harnessing the thermal energy of seawater, these pumps not only offer a sustainable alternative to traditional heating and cooling methods, but also pave the way for innovative applications in energy-efficient building management. Key Components of Heat Pumps from Mor Heat pumps are made with several key components, each of which plays an important role in the efficiency and functionality of the system:

1. Heat exchanger:
   • Function: Facilitates the transfer of thermal energy between seawater and the cold circuit without circulating corrosive seawater directly through the system [6].
   • Types: Uses corrosion-resistant materials to ensure durability and efficiency in transferring heat from seawater to the coolant [3] [10].
2. Compressor and Working Substance:
   • Compressor: Increases the pressure of the working substance, which relies on electricity, thereby increasing its temperature for efficient heat transfer [3] [10].
   • Active Substance: Absorbs, transports and releases heat through its circulation within the system, with its boiling points adjusted by pressure manipulation [3].
3. Control and Regulation Elements:
   • Regulating device: Regulates the flow of the working substance, using devices such as capillary tubes or expansion valves to maintain the balance of the system [9].
   • Pressure Controls and Controllers: Ensure the system operates within safe pressure ranges and manage the entire operation, including sensors and user interfaces for optimal performance [9] [10].

These components are necessary for the operation of the heat pump from the sea, ensuring efficient heat transfer and longevity of the system. How Sea Heat Pumps Work Sea heat pumps use the thermal energy of the ocean to efficiently heat buildings and neighborhoods. This process involves several key steps:

1. Thermal energy transfer: Seawater is sucked into the system's evaporator via the suction pipe, where its thermal energy is transferred to the refrigerant. This leads to evaporation of the coolant, turning it into a gas [4].
2. Compression and Heat Exchange: The gaseous coolant is then compressed, increasing its temperature. It flows through the condenser heat exchanger, where its thermal energy is transferred to the building's heating system. This step is crucial for effective heating of the target area [4].
3. Continuous Cycle for Heating and Cooling:
   • The high-pressure refrigerant gas, now in gaseous form, moves through the condenser where it releases heat and condenses into a liquid [3].
   • This high-pressure fluid passes through an expansion valve, reducing the pressure and temperature, preparing it to reabsorb heat in the evaporator [3].
   • This cycle provides a constant source of heating and cooling, with a system performance factor significantly higher during transitional seasons, saving energy [11].

By optimizing the coefficient of performance (COP), marine heat pumps show efficiency levels between 2 and 6, indicating their potential for reliable and highly efficient installations [3]. Advantages of Using Heat Pumps from the Sea Heat pumps from the sea offer a number of advantages that significantly contribute to energy efficiency and environmental sustainability:

• Energy Efficiency and Cost Savings:
  • The coefficient of performance (COP) values range between 2 and 6, which indicates a high energy conversion efficiency [3].
  • They can lead to energy savings of up to 50% compared to traditional heating systems, reducing operating costs, especially in district heating network scenarios [3] [10].
  • Long service life of 20-25 years with minimal maintenance requirements, ensuring long-term economy [10].
• Ecological Advantages:
  • They can reduce greenhouse gas emissions by up to 80% compared to fuel oil, contributing to cities' carbon neutrality goals [3] [13].
  • They operate without emissions, using renewable and abundant marine resources, and do not release waste heat into the environment [4] [10].
  • They help to alleviate the heat island effect of the city, improving outdoor comfort and resistance to heat waves [14].
• Operational and Installation Advantages:
  • They provide stable temperatures for heating, cooling and hot water supply, suitable for both new and existing buildings [4] [10].
  • They support energy independence by reducing dependence on external energy sources, exploiting a consistent energy source from the sea [3] [10].
  • They provide a closed system that is quiet in operation and improves indoor air quality, because it does not rely on combustion [10]. Actual Applications of Sea Heat Pumps Sea heat pumps have seen successful application in various global locations, demonstrating their versatility and efficiency. Notable cities using this technology include Biarritz, Sète, Leucate, Dieppe, Ajaccio, Propriano, Dunkirk, La Rochelle, Lorient, Marseille, Cannes, Fécamp, Barcelona and Boulogne-sur-Mer, showing a wide geographical and climatic range of application [13] . On islands, where traditional energy resources can be scarce or expensive, marine heat pumps offer a sustainable solution for heating and cooling needs, using the abundant local resource of seawater [13].
• Innovative Solutions: The Enerplage® system is an example of innovation in overcoming the challenges of taking seawater for heat pumps, using naturally filtered seawater with beach sand, thus reducing investment and maintenance costs [13].
• Pioneering Projects: The Massileo energy system in Marseille, France, connects a marine energy recovery station in the city's harbor with heat pumps that supply heat, cool air and hot water to the Îlot Allar eco-district. This system, powered by 75% renewable energy mainly from sea heat recovery, demonstrates the potential of sea heat pumps in urban environments [23]. The Alaska SeaLife Center project further illustrates the potential of marine heat pumps to significantly reduce energy costs and carbon emissions, with the expectation of increased efficiency as the system expands [18]. These examples highlight the practical applications and benefits of marine heat pumps in real-world environments, contributing to sustainability and decarbonisation efforts around the world. Challenges and Future Prospects Although water-to-water heat pumps, especially those using seawater, offer numerous advantages in energy efficiency and environmental sustainability, the industry faces several challenges with promising future prospects:
• Challenges in Industry:

1. Lack of Professional Trades: The complexity caused by heat pumps requires a higher level of skills among craftsmen, a resource that is currently in short supply [15].
2. Complexity of Refrigerant-Based Systems: Refrigerant-based systems add layers of complexity to hydrodynamics, requiring specialized training for proper installation and maintenance [15].
3. Need for Training and Retraining: The transition to installing monobloc air-water heat pumps requires significant efforts for retraining, whereby the duration of the apprenticeship can reach up to two and a half years [15].

• Opportunities and Prospects:

1. Market growth: The North American market for air-to-water heat pumps is projected to grow at a CAGR of 9.8%, reaching USD 227.4 million by 2025 [15].
2. Efficient Installation Teams: A collaborative approach involving plumbers, refrigeration technicians and electricians can simplify the installation process [15].
3. Policy support: Improved government policy support is essential to overcome initial cost barriers and promote wider adoption [16]. This juxtaposition of challenges with growth potential highlights the need for concerted efforts in training, policy-making and industry collaboration to take full advantage of water-to-water heat pumps. Conclusion Through this research on water-to-water heat pumps, with an emphasis on the pioneering use of seawater, we have explored in detail the mechanics, advantages, real-world applications, and current challenges and future prospects of these technologies. By researching the mechanisms of operation, key components, and environmental and energy benefits, we discovered the potential of water-to-water heat pumps to transform the way heating and cooling is done in buildings around the world. Real-world applications in cities and rural areas around the world demonstrate not only technological innovation, but practical application that improves sustainability and comfort. Despite challenges in terms of skilled labor and installation complexity, the water-to-water heat pump market shows promise, supported by growing interest, supportive policies and collaborative initiatives. Through the cooperation of industry, governments and experts, water-to-water heat pumps have the potential to become a key technology for achieving sustainability and energy efficiency goals in the future.

References:

[1] - https://www.pmengineer.com/articles/84610-water-to-water-heat-pumps
[2] - https://www.araner.com/blog/what-is-a-water-to-water-heat-pump
[3] - https://www.araner.com/blog/seawater-heat-pumps
[4] - https://www.araner.com/blog/renewable-heating-system-generate-heat-from-sea-water
[5] - https://www.kensaheatpumps.com/water-source-heat-pump/
[6] - https://www.kcaw.org/2014/08/22/heat-pumps-tap-oceans-thermal-energy-to-warm-buildings-neighborhoods/
[7] - https://www.wired.com/story/how-do-heat-pumps-work/
[8] - https://www.quora.com/Why-is-a-Water-Source-Heat-Pump-more-efficient-than-an-Air-Source-Heat-Pump
[9] - https://www.danfoss.com/en-us/service-and-support/case-stories/dcs/components-for-heat-pumps-introduction/
[10] - https://www.energy.gov/eere/amo/articles/industrial-heat-pumps-steam-and-fuel-savings
[11] - https://www.tandfonline.com/doi/pdf/10.1179/174602209X427060
[12] - https://www.rpsgroup.com/insights/consulting-uki/the-pros-and-cons-of-heat-pumps-what-you-need-to-know/
[13] - https://www.ecoplage.fr/en/challenges/marine-energy-building
[14] - https://www.frontiersin.org/articles/10.3389/fenrg.2022.913411
[15] - https://www.linkedin.com/pulse/navigating-future-air-water-heat-pumps-challenges-people-ridler
[16] - https://www.iea.org/reports/the-future-of-heat-pumps
[17] - https://www.anthesisgroup.com/insights/technologies-for-a-low-carbon-future-heat-pumps/
[18] - https://juneau.org/wp-content/uploads/2018/04/JCOSSeawaterHeatPumppresentationForumApril112013.pdf
[19] - https://www.worldpumps.com/content/news/nrel-research-details-the-benefits-of-heat-pumps/
[20] - https://www.csemag.com/articles/the-benefits-of-using-water-source-heat-pumps/
[21] - https://www.thermalearth.co.uk/water-source-heat-pumps
[22] - https://iea.blob.core.windows.net/assets/2cf6c5c5-54d5-4a17-bfbe-8924123eebcd/TheFutureofHeatPumps.pdf
[23] - https://ec.europa.eu/regional_policy/en/projects/france/sea-water-powered-heating-system-sets-sustainable-example-in-marseille-france
[24] - https://www.menerga-adria.com/blog/2019/10/18/8620/
[25] - https://www.youtube.com/watch?v=QykwWs3L1W8
[26] - https://www.coastalair-tech.com/article/everything-you-need-to-know-about-heat-pump-systems