Europe has begun the transition to a new green energy supply for the industries and households of the future.

In line with the various climate agreements, a start has been made on dismantling energy supplies from fossil fuels such as gas, oil and coal.

Of course, this also means that alternative, preferably reusable, energy supplies must be found in a hurry in order to fill the vacuum. Investments are being made in wind and solar energy, geothermal energy, biogas, hydrogen, tides, hydropower, etc., but also in the consumption of LED lights, electric cars, etc. The currently still relatively small percentage share of this in the energy economy will have to increase very significantly in the coming decades.

Fortunately, there is plenty of development and study of the various energy systems, the returns are improving rapidly and the cost price is falling sharply. To make the right and affordable choices for the future, we will not only have to look at the current effectiveness, but also anticipate future developments. Effectiveness and efficiency on the one hand, but also availability, effects on spatial planning (and the encroachment on these) ultimately determine the success of the choices that must be made now.

For example, the vast majority of total energy consumption in Europe for households is devoted to heating (62.8%). Electricity consumption for appliances and lighting had in this overview a 14.5 % share. (see graph below)

At present this heat is almost entirely provided indirectly by burning natural gas and coal and partly by converting electricity into heat in the case of wind and solar energy. Combustion releases CO2 (but also soot and fine particles) which must be compulsorily reduced in the short term. The most logical step with regard to the heat supply is to switch to an energy source that can provide the heat directly without any emissions. Geothermal energy, which is inexhaustible, offers the opportunity to do this.

For the energy transition to be successful, the right choices will have to be made. Which choice is best depends on the following factors:

- Continuous availability

- Cost per energy unit (it must remain affordable!)

- Installation costs (and burden on the environment)

- Maintenance costs (and burden on the environment)

- Environmental impact (and burden on the environment)

- Expected development of production costs and efficiency.

- Required infrastructure changes (and burden on the environment)

- Required knowledge and manpower for installation and maintenance

An underexplored aspect of energy supply is heat. There are various incentive programs for electricity development (solar panels, wind turbines) but regarding heat supply no clear government policy has been developed. This is all the more remarkable when one realizes that heat supply has a more than 55% share in total energy consumption. The share of electricity supply for illustration purposes is "only" 20%. The heat supply is currently provided for the lion's share (80%) by natural gas supplemented by biomass (from waste incineration). The share of renewable "green" energy has fluctuated around a meager 5% for decades. 

Of the total heat demand in the Netherlands, 4% is currently supplied by heat networks, particularly in the larger cities. In the various climate plans it is emphasized that it is precisely here that large-scale expansion of these heat networks can yield considerable gains. 

Particularly in district heating systems that are heated by gas-fired central heating boilers, enormous gains can be made. In the Netherlands alone, this concerns 500,000 apartments. Heating by means of geothermal energy would be ideal for this and could give the share of renewable energy a substantial boost.

The share of electricity in total energy consumption in the Netherlands is 20%. The use of alternative green systems to supply this has grown in recent years from 5% to 12.5%. These are mainly systems that make use of wind or the sun. The disadvantage of these systems lies in the continuous availability, as these systems are currently highly dependent on the availability of wind and solar hours. Moreover, the frequency fluctuations in wind, and solar strength also result in frequency fluctuations in the power supplied. 

A number of solutions are currently available to overcome these production problems.

Efficiency improvement

The efficiency of wind and solar power generation is progressively improving as a result of technological advances. From the course of the curves of the last 25 years a reasonable estimate can be made of the expected future yields. 

Backup energy system

To ensure continuous, stable supply to the energy grid, current fossil fuel power plants currently function as standby supplies that will delay the desired decommissioning of these plants. Thus, there is a need to develop alternative energy sources that can ensure the stability and continuity of the power grid. Perhaps a mix of geothermal, biomass, tidal/hydropower energy can contribute to this. 

Energy distribution

By means of (temporary) storage of energy, availability and stability can be equalized. To apply this successfully, not only will the production capacity of wind and solar energy need to be increased, but the distribution system will also need to be updated. The most obvious carriers at present are batteries and hydrogen. 

Batteries are practical, but have a considerable environmental impact, which partly cancels out the green character of this alternative energy. However, it is expected that in the near future batteries will undergo major developments in terms of efficiency in technology, production and capacity.

Hydrogen (which can be produced using solar energy) has the advantage that storage and combustion are hardly harmful to the environment. Because hydrogen is easily transported, it can be imported from abroad. Hydrogen as an energy form, however, requires major network adaptations in production, storage, distribution and combustion/energy conversion (in power plants and households), which may again have an adverse environmental impact.

Geothermal energy makes use of the earth's heat. The heat in the earth's crust is inexhaustible and continuously present at any location. With the technology of the past, exploitation of geothermal heat was almost only possible in places where energy came to the earth's surface as in Iceland, for example. Two important developments have contributed to a much wider range of applications. First, with today's heat exchanger technology, small temperature differences can be efficiently converted into usable energy. Second, today it is easier to drill deeper into the earth's strata, making the installation of geothermal systems more economically viable. 

From the earth's core, cooling has been taking place since the earth came into being. This cooling takes shape through the formation of enormous plumes that move from the core through the earth to the outer edges of the globe over which it spreads. A never-ending process that will continue for billions of years. To illustrate, in some areas these plumes rise to the surface of the earth, as for example in Hawaii, Iceland and Yellowstone Park. 

The heat flow resulting from this process can be observed at any place in the world and moves through convective and conductive processes. Depending on the geological structure of the Earth's crust, the degree of heat flow varies but is "harvestable" almost anywhere in the world. 

This heat flow is also measurable, predictable and behaves through physical laws: the thermodynamic laws. By recording a number of measurable parameters at a location, it is therefore possible to determine the geothermal potential at that same location. These are mainly the permeability of the geological layers (the permeability) and the density (porosity) of the rock, but also the conductivity of this same rock, the heat flow (flux) and finally the thermal gradient. This is the rate of increase in temperature averaging 3 degrees per every 100 meters of depth.

‘'Old' European geothermal systems.

As mentioned, it is relatively easy to "tap into" geothermal energy in Europe. 

What is usually not realized is that application in Europe is mainly related to a single form of geothermal energy: the doublet. A form of geothermal energy in which two wells are drilled, one of which serves as a production well from which hot water is pumped up and the other serves to return this pumped water once it has transferred its heat to the surface. A system that in theory could generate large yields at relatively low cost. It seems a perfect system for extracting renewable and cheap energy. In theory, this is also correct and if everything goes according to plan, the developer of the source and the consumer of the energy will also be an absolute winner. Unfortunately, reality often proves to be inconsistent with theory. Drilling complications, blockages in the pump and return path, seismic problems such as tremors and cracks, disappointing water volumes and flow rates are just some of the common problems. 

The doublet system is a forced geothermal system. While it takes advantage of the presence of formation water flowing through permeable layers at great depths, by pumping it unnaturally forces the flow rate of this formation water through the geological layers by a significant factor. Not only does this cause stress fields in the pumping up and down area (under- versus overpressure), migration of fine particles through the permeable layers (aquifers) but moreover it can completely change the characteristics of these geological layers. 

Problems overcome by new technique!

Meanwhile, a completely new technique has been developed with which the above described objections and complications belong to the past. This technique concerns a system in which circulation is established in a single hole using the heat flow in the earth's strata and is not dependent on the presence of underground water flow. Due to the completely different design and installation of this technique, the problems that often occur with doublets have been overcome and a sustainable and reliable system is offered for the supply of, in principle, inexhaustible geothermal energy from the European soil.

Geothermal energy in Europe: the NotusPid single-hole system.

The NotusPid system is based on pure geothermal dynamics. It makes use of the flow of heat through the earth's crust. It is therefore also not dependent on the presence of underground water currents as with doublet technology. As a result, it can be applied virtually anywhere. Energy is thus literally at your feet. The area of application varies from shallow applications of 500 to 1000 meters in combination with heat pump technology, but can also be installed at medium and ultra-deep boreholes. The ideal application is of course entirely dependent on demand. 

The system can be designed to meet the exact demand. Whether in the middle of a city or in a remote location, we bring the energy to the front door. It is also possible to install multiple single-hole systems to create an energy field. Because the single-hole system functions autonomously, multiple systems can be installed at a small distance (depending on the depth). This allows for the activation of an energy field whereby large power outputs can be produced.

Advantages:

- Flexible (as needed, no under/over capacity)

- Continuous 24/7 production

- Simple, flexible installation (simple technology)

- Low maintenance costs (no clogging of filters)

- Low failure rate

- Very long lifetime of the sources (>50 years)

    (no sources falling dry (the existing formation water is circulated indefinitely))

Small-scale application

Shallow geothermal energy is ideal for providing heat and, if desired, cooling to a number of homes, apartment blocks or a block of apartments. Using heat pump technology, the application is virtually universal.

Large-scale application

By installing the system at greater depth (around 2500 meters) the yield will also increase significantly. At a depth of 2500 meters the temperature is so high that the use of heat pumps is no longer necessary. Ideal for residential areas, shopping malls and industrial applications.

Problems overcome by new technique!

Meanwhile, a completely new technique has been developed with which the objections of complications / malfunctions, high risks and uncertain continuity belong to the past. This technique concerns a 'closed' single-hole system without complications and with a long life span. This system overcomes all problems and offers a sustainable and reliable system for the supply of basically inexhaustible geothermal energy from the European soil.

The system

The single-hole system developed by NotusPid concerns a system that can be used both for hydrothermal geothermal energy (such as doublets) but also for petrothermal geothermal energy. So in non-aquiferous conditions.

The technology makes use of the data that firstly, heat convection takes place throughout the earth's crust as a result of a continuous flow of liquid rock from the earth's core, so-called 'plumes'. Second, the water saturation of the rock in the earth's crust is used. Based on physical thermodynamic processes, the heat is distributed over the earth's crust by convection, whereby porosity, permeability and conductivity of the rock play a far-reaching role.

The principle of operation

By drilling a large diameter borehole (to a predetermined depth, depending on the desired yield and temperature), a source is created with the desired ambient temperature (depending, of course, on the geothermal gradient). Due to the water saturation of the rock in the earth's crust, the drill column will automatically fill with water to about 10 meters below ground level where the formation pressure levels off with atmospheric pressure. The collection of the hot formation fluid takes place via an insulated pipe which will be installed down to the bottom of the borehole. The last section of this tube is a filtered open section. Through this tube the formation fluid is brought to the surface by means of a circulation pump. The fluid is passed through a heat exchanger where the temperature is transferred to another medium. The cooled fluid is returned through four tubes in the same hole.

The returned fluid (with a lower temperature than the extracted fluid) is brought back into the formation until the ambient temperature is between 5 - 10 % higher than the temperature of the returned fluid. Due to the temperature difference with the environment, a temperature difference ("temperature sink") is created at the "release" point that will generate induction of heat flow in the formation.

The fact that the returned fluid increasingly enters a higher ambient temperature results in heat exchange with the fluid present in the formation pores. This exchange increases with the increase of depth in a pear shape which is therefore also called the convection pear. The temperature difference created between the drill shaft on the one hand and the formation rock on the other initiates a heat flow which, through the permeability and interaction with the pore fluid, leads to exchange and heating of the returned fluid. It has been scientifically proven that within this process, an energy compaction is created which is higher by a factor of 4 to 5 at the drill shaft compared to the convection boundary area. The returned water also experiences heating by means of conduction.

Since convection takes place over a long vertical distance, geothermal energy is also generated over this same length. This is in contrast to doublet technology, in which energy is recovered over a relatively short horizontal section.

The above technology leads directly to 5 major advantages over the doublet and EGS technology:

Exclusion of operational risk (the system is not dependent on the creation of a water flow within an aquifer, natural or artificial)

Exclusion of tremors/cracks (because circulation is established within a single hole, there is no under/over pressure or in any other way the creation of a tension field which could lead to far-reaching instability within the formation)

No mineralization/ deposit problems. Because in principle almost the same water is recirculated, there is no supply of "fresh" water which can mean an accumulation of minerals, salts, etc.

Because no forced flow is induced within the formation, there is also no migration within the rock, which can clog the formation and drastically change the permeability, as has been regularly demonstrated in active doublets. Furthermore, no transport of fine particles and minerals takes place within the rock.  

By eliminating the production pump which has to provide over-capacity suction and an injection pump which has to return water at overpressure and replacing it with a simple circulation pump, the COP value can be improved.

How many times have we bumped at the same stone....

The single-hole system is therefore universal, multi-applicable, low maintenance, no "down-time" for replacing parts or re-power the well.

It is also predictable in terms of yield in both the short and long term, 

The lifespan is virtually unlimited.

It does not have all kinds of unpleasant side effects such as earthquakes, clogging of filters, changes in the subsoil, pollution by heavy metals.

It can be used for both very large and very small projects, tailor-made energy.

No complicated constructions to get rid of possible overcapacity. If there is no need for heat, simply switch it off. Just as simple as a light switch!

So why is it not widely applied? That is indeed the big question and the answer is both staggering and simple. In today's investment climate, people are totally focused on what the return is per euro invested. On paper, the big returns from doublets beckon. By applying even greater pumping power in the wells, the returns are great, this seems too good to be true,...and it is. 

Does the revenue model take into account that there are continuous problems with filters, that the permeability of the earth's strata changes due to the forced flow,...that millions are spent regenerating wells,...replacing equipment? 

It is time to replace the illusion with a workable alternative.

The solution lies in simplicity. Heating by a simple uncomplicated bore and ditto installation, apartment building by apartment building, factory hall by factory hall, gymnasium by gymnasium, the applications are endless, simple and cost effective