TEO, TEA and TED – types of aquathermia

Aquathermia is another term for thermal energy from water. There are three types of aquathermia, using different types of water:

• thermal energy from surface water (TEO in its Dutch acronym), such as a river, canal, lake or ocean. The temperature of the water in ditches and canals is about 7 degrees in winter. The sun heats the water to around 25 degrees in summer. This heat from the water is used to heat or cool houses.
• thermal energy from waste water (TEA in Dutch). The heat from wastewater (sewage) is used to heat houses. This is also called riothermia.
• thermal energy from drinking water (TED in Dutch). The heat released when producing drinking water can also be used to heat houses.
   

How does aquathermia work?

Aquathermia can be used with or without heat storage.

• Aquathermia with heat storage
  In the summer months you extract heat from the surface water (TEO) with a heat exchanger. This heat is stored in the ground in a heat and cold storage system (ATES, or Aquifer Thermal Energy Storage). In the colder (winter) months you pump up the warm water from the ground. A heat exchanger takes the heat out of the water and releases it to a heat pump. The central heat pump heats the water in the heat network to the desired temperature for heating and hot tap water. Multiple homes are connected to the heat network.
  - You can also work with one heat pump per building instead of a central heat pump.
  - A heat network is not needed if you heat one building.
  - In the summer you can cool with the winter cold. The cold from the water is then stored underground in the winter for use in the warm summer months. 
• Aquathermia without heat storage
  The heat from the water is transferred through a heat exchanger for use in the home directly, perhaps through a heat network. A heat pump brings the water to the right temperature.

TEA and TED work just like TEO, the difference being that the heat is extracted from wastewater or drinking water pipes rather than surface water.
 

Made-to-measure

An aquathermia project is always made-to-measure. The financial and technical feasibility depends on the degree of insulation of buildings, heat and cold demand, the proximity of water sources, and the options for heat storage.
Each project involves many different parties such as the source owner (regional water authorities, Rijkswaterstaat [the Directorate General for Public Works and Water Management], drinking water companies), the network manager, the heat company, the financier, the housing corporation, the builder, the municipality and the province. Large-scale heat supply with aquathermia always requires a public-private partnership.
 

Sustainable heat source

Aquathermia water sources are heated directly or indirectly by the sun and the environment. If 80% of the electricity used by the heat pump comes from renewable sources by 2030, as agreed in the Climate Agreement, the CO₂ emissions from aquathermia will be very limited.
 

The Impact of cooling surface water

Cooling surface water in summer can affect water quality positively by reducing the risk of microbiological contaminants, such as blue-green algae. The flow in the water arising from aquathermia is also good for water quality.
Research into further ecological effects is underway. In most cases no ecological impact on the water system is expected. But there may be ecological impacts locally, where the discharged water is colder than the receiving water. These will be included in the permit requirements.
 

Green Deal Aquathermia

The Green Deal Aquathermie (in Dutch) was signed in May 2019. Parties to the Green Deal undertook mutual agreements on the use of aquathermia for the built environment. The aim is to map out the value and application of aquathermia to accelerate the heat transition. The Netwerk Aquathermie (Aquathermia Network) carries out the Green Deal Aquathermia through knowledge development and knowledge sharing.

The Green Deal Aquathermie ended in May 2022. There are over 60 parties involved and the network continues to grow. In 2023, the Aquathermie Network will continue to develop aquathermal energy. The NAT team is committed to creating a level playing field, responsible application and standardization of aquathermal energy. To ensure continuation of activities and stimulate market development, we are seeking collaboration with the vereniging Bodemenergie Nederland, the Nationaal Programma Lokale Warmtetransitie (NPLW) and the Nederlandse Vereniging Duurzame Energie (NVDE).
 

Knowledge and practice

Even more knowledge is needed in areas such as governance and the impact on the ecology of the water, to be able to use aquathermia on a large scale for heating and cooling buildings. Netwerk Aquathermie (NAT) is working with a research agenda for this, from which many questions have been addressed in the WarmingUp heat collective. Among other things, NAT also collects and publishes the current status of aquathermia projects (TEO, TEA and TED) on a digital map.