The first hot shower heated by the brand-new aquathermal installation at the Harbour of Vlieland took place on 31 March 2026!
This is the first of many fully clean, warm showers to come at our Dutch pilot site on the island of Vlieland. The project involves installing an aquathermal system to heat the water used in the showers offered by the Harbour of Vlieland to its visitors, and to heat the harbour facilities during winter. The system will also provide heat to a neighbouring house.
This pilot site is special, as it draws heat from salt water, making the work of technical partner EXTRAQT more challenging: materials need to prove their resistance over the long term.
Given the special context of the site, the system is optimised throughout the year: in the colder months, when harbour guests are rare, it mainly heats the building, while in spring and summer the heat is used to warm the shower water for the many visitors calling at the harbour.
Building an aquathermal system is an engineering endeavour that involves many experts. Let’s have a look at this process!
From signed contracts to removing the gas installation
Following a careful procurement process in autumn 2025, the first contracts were signed in December, and in January 2026 the old gas-based installation was removed. There was no turning back!
Laying the pipes
At the start of the year, excavation work began to lay the pipes connecting the low-temperature heating network to the three heat exchangers placed under the water at the quay. As the number of pipes to be laid was limited, the work progressed smoothly, with the pipes joined together using an automated heating process.
Designing sea-water-resistant heat exchangers
The heat exchangers were manufactured in Germany. Originally made of steel, they had to be redesigned once destined for sea water: drawing on its own experience, the Harbour of Vlieland knew just how damaging salt and sand can be to steel. As a result, most of the heat exchanger is now made of high-quality plastic.
Installing the buffers
While the heat exchangers were being produced, the piping and buffers were installed in the harbour's technical utility room. Four 1000-litre buffers and a 750-litre boiler now supply hot water for more than 1000 guests during the high season.
Smart software, smarter energy use
The Harbour of Vlieland developed its own software system in-house. It draws on a wide range of data — including weather forecasts, solar production, electricity consumption and harbour reservations — to forecast the number of showers and the amount of energy needed each day. Based on this forecast, a number of buffers are pre-heated whenever the sun is shining, ready for use the following morning (read here how this smart system works). This will make it possible to implement energy management strategies that optimise the use of locally produced renewable energy, contributing to the island's energy independence and resilience.
A race against the season
As the harbour season starts on 1 April, the aquathermal system had to be ready before that date. With work only beginning in January, this was a real challenge. On 31 March, the boiler was finally filled and put into operation — and at 23:45 that same evening, the first hot shower became a reality. Just in time!
Finishing the installation
In April, the heat pumps were installed and all the buffers became available to the system. All three heat exchangers were also placed in the water, and the software was connected to the technical system. Combined with the sunny weather, this gave more than enough hot water for the harbour guests.
Open day
On 9 April, Vlieland residents and harbour guests were invited to the launch event. Many took the opportunity to enjoy a detailed tour of the project and check out the technical installation.
