Marine Source Heat Pumps (MSHP) - Harnessing the power of the sea forcleaner, sustainable heating and cooling

Heat pumps are becoming increasingly prevalent in the UK as businesses and public sector entities seek to move away from traditional fossil fuel heating sources and decarbonise. One underutilised source of energy for heat pumps is the sea.

1. What makes the sea a viable source of energy?

The UK is surrounded by water and has an enormous amount of renewable heat just off its shores. Seawater maintains a much steadier temperature than air throughout the year, typically ranging from 6 to 15°C depending on the season and location. This consistency makes it a reliable, year-round source of heat energy. Unlike air-source systems, which see fluctuating air temperatures, marine source heat pumps draw from this stable thermal reservoir. For coastal towns, ports, and islands, the sea is a natural resource that can reduce reliance on fossil fuels while providing systems with highly efficient heating and cooling performance.

2. How does a marine source heat pump capture heat from seawater?

Marine source heat pumps operate on a simple principle: they extract heat from seawater, upgrade it using a heat pump and deliver it to a building’s heating system. In practical terms, seawater is pumped through an intake pipe or a submersible pump filter assembly, passing through various filters before reaching a heat exchanger. Thermal energy is transferred into a separate, closed-loop system. A refrigerant cycle within the heat pump then raises the temperature to an appropriate level for space heating or hot water. The cooled seawater is then returned to the sea through a discharge outlet a few degrees cooler, ensuring minimal environmental impact.

3. Where in the UK are marine source heat pumps already being used?

Although marine source heat pumps are still a relatively new technology, several projects around the UK demonstrate their effectiveness:

● Queen’s Quay in Glasgow, for example, has a district heating network that uses water-source heat pumps drawing from the River Clyde to provide heat to 1,400 homes and businesses.

● Shoreham Harbour in Sussex has a 300kW marine source heat pump system that supplies a local business centre.

● Tate Liverpool is installing a 750kW marine source heat pump system that provides heating and cooling to the refurbished art gallery. These projects demonstrate that the UK’s coastline, from the far north to the south coast, already offers proven examples of how seawater can power sustainable heating.

4. What are the key benefits for coastal communities and developers?

For coastal communities, marine source heat pumps can provide stable, low-carbon heating at lower cost than air source heat pumps. The consistent temperature of seawater enables these systems to achieve a Coefficient of Performance (CoP) of around 3–4, meaning that for every unit of electricity used, three to four units of heat are delivered. Developers and local authorities also recognise the benefits in terms of energy security and sustainability. By using a nearby natural heat source, projects can meet increasingly strict energy efficiency and carbon reduction targets. For coastal regeneration schemes or island networks, this technology can be incorporated into wider district heating systems to help communities transition away from fossil fuels.

5. What environmental and technical challenges need to be managed?

Seawater poses specific design and maintenance challenges. Salt can corrode equipment, while marine organisms such as algae and barnacles can accumulate on pipework in a process known as biofouling. To address these issues, systems employ specialist coatings, filters and materials, such as titanium, to ensure long-term reliability. Environmental considerations are equally important. Water abstraction and discharge must comply with permits issued by the Environment Agency (EA) or the Marine Management Organisation (MMO). Designers must also ensure that discharge temperatures do not disturb marine ecosystems or cause thermal shock to fish and other sea life. While installation costs may be higher than for air-source systems, the long-term savings and stability often offset the initial investment, particularly for larger sites.

6. Is a marine source heat pump the right choice for your project?

Marine source systems are best suited to buildings close to the sea, a dock or tidal rivers, where access to the water is feasible. The ideal location is within a dock that maintains a relatively steady water level. If the site is suitable, this technology can provide clean, efficient heating with low operating costs and minimal emissions.

Frequently Asked Questions About Marine Source Heat Pumps in the UK

What is a marine source heat pump (MSHP)?

A marine source heat pump (MSHP) is a low-carbon heating and cooling system that extracts renewable heat from seawater, tidal rivers or docks and upgrades it for use in buildings. In the UK, MSHPs are increasingly used to reduce reliance on gas and oil heating.

Why is seawater a reliable heat source in the UK?

UK coastal waters maintain relatively stable temperatures throughout the year, typically between 6°C and 15°C. This consistency allows marine source heat pumps to operate efficiently year-round, including during colder winter months.

How do marine source heat pumps work?

Marine source heat pumps abstract seawater through an intake system and pass it through a heat exchanger. Heat energy is transferred to a closed refrigerant circuit, upgraded for heating or hot water, and the cooled seawater is discharged back to the sea in line with UK regulations.

Where are marine source heat pumps already used in the UK?

Marine source heat pumps are already operating successfully across the UK, including district heating at Queen’s Quay in Glasgow, a commercial installation at Shoreham Harbour, and the marine heat pump system at Tate Liverpool.

Which buildings in the UK are suitable for marine source heat pumps?

Marine source heat pumps are best suited to buildings located close to the sea, tidal rivers, docks or harbours. Typical UK applications include coastal housing, public sector buildings, commercial developments and district heating networks.

What are the benefits of marine source heat pumps for UK developments?

Marine source heat pumps typically achieve CoP values of 3 to 4, offering high efficiency, lower carbon emissions and reduced exposure to volatile gas prices. They also help UK developments meet net-zero and sustainability targets.

Are marine source heat pumps environmentally sustainable?

Yes. Marine source heat pumps provide renewable, low-carbon heating and cooling. Systems are designed so seawater is returned only a few degrees cooler, ensuring minimal environmental impact when correctly permitted and managed.

What UK permits are required for marine source heat pumps?

Installations require permits from the Environment Agency (EA) or the Marine Management Organisation (MMO). These permits regulate abstraction volumes, discharge temperatures and environmental protection for marine ecosystems.

What technical challenges do marine source heat pumps face in the UK?

Key challenges include saltwater corrosion and biofouling. These are addressed through corrosion-resistant materials such as titanium, specialist coatings, filtration systems and planned maintenance regimes.

Are marine source heat pumps cost-effective in the UK?

While upfront costs can be higher than air source heat pumps, marine source systems often deliver lower long-term operating costs. For large UK buildings and district heating schemes, efficiency and durability can offset initial investment.

Is a marine source heat pump right for my UK project?

A marine source heat pump may be suitable if your site is close to seawater, docks or tidal rivers and can accommodate intake and discharge infrastructure. For UK coastal and regeneration projects, MSHPs offer a future-proof heating solution.