Low temperature geothermal energy

Shallow geothermal energy is also called low grade geothermal energy and means little more than extracting geothermal heat from shallow formations. On average, the temperature of earth's strata goes up by 3°C every 100 meters of depth. So from a depth between 500 meters and 1500 meters, the temperature varies between 20 and 55°C.

Usually we start calculating from a depth of about 300 meters. The reason for this is that the temperatures at a depth of less than 300 meters are not really interesting and also the groundwater layers up to a depth of 300 meters are often used for drinking water extraction.

Heat pump

Shallow geothermal energy at this depth is usually applied indirectly i.e. in combination with a heat pump. Only in new buildings where the heat demand is sometimes lower than 35°C, such as some underfloor heating systems, can in principle the heat be supplied directly to the system. In practice, however, the heat demand is often higher and then the geothermal fluid must be increased to higher temperatures by means of a heat pump.

So, in summary, we can say:  

By shallow geothermal, then, we mean geothermal applications up to a depth of 1,500 meters.

These drillings can be done with relatively small and therefore cheaper drilling rigs.

Given the thermal gradient in Western Europe, a maximum ambient temperature of 45 °C is tapped here. 

Most heat networks require a temperature higher than 35-45 °C. It will then be necessary to install a heat pump after the heat exchanger to raise the temperature to the desired working temperature (in heat networks this is often between 60-80 °C.

Because the geothermal energy is not used directly but the intermediate step of a heat pump is necessary to obtain the desired operating temperature, we speak of indirect geothermal energy.

Advantages

The main advantage of this form of geothermal energy is that the costs of setting up such an application are relatively low.

• The drilling can be done with smaller (and therefore cheaper) drilling rigs.

• The installation can be done with high-quality plastics, which are considerably more economical than metal versions.  

An additional advantage is that in many countries, drilling to a depth of 500 meters is not considered mining. This makes the permit process much simpler and faster.

Legal aspects for geothermal installations

In most countries the installation of geothermal wells are bound by legal procedures. We takes as a clear example the situation in the Netherlands:

Water Act

This applies to depths less than 500 metres

• Permission and licence are granted by the provincial government

• The usual regulations for drinking water production must be complied with

• Additional aspects: energy balance, stakeholders and provincial restrictions

• There is no subsidy scheme (yet) for installations to a depth of 500 metres

Mining Act

Applicable to depths greater than 500 meters

• Competent authority: Ministry of Economic Affairs, implementation SSM

• Strike force in safety regulations, because of the prevention of oil and gas

• Ability to provide insight into safety risks and mitigating measures

• Qualifies for SDE+

Shallow (low grade) geothermal energy is therefore very useful and can be applied on a large scale.

Applications should be sought mainly in small-scale construction projects, apartment buildings, office buildings.

The application possibilities are enormous. 

The great advantage of the NotusPid system is that it can be installed virtually anywhere.

The enormous flexibility of the system allows objects that cannot or can barely be heated with fossil-free energy to still undergo the desired energy transition.