Geothermal energy or geothermal heat is heat energy generated and stored in the earth. It results from the heat radiation from the inside of the earth, the result of natural nuclear decomposition processes at the core. The earth is thus a continuous source of heat.

The natural heat of the earth is sufficient to meet the global world demand for energy. If we take a shell of the earth's crust with a thickness of 6 km, it contains the equivalent to 50,000 x of the total natural gas and oil supply in the world.

In areas with volcanic activity, that heat is very close to the surface and has been used for a hundred years for electricity production and heat recovery. In the Netherlands, geothermal energy is mainly used for space heating in greenhouse horticulture (90%) and heating residential areas.

Geothermal energy is sustainable: it’s recovery does not lead to the depletion of stock. As a result, geothermal heat meets Dutch’ government's priority to reduce fossil fuel use such as natural gas and reduce the associated emissions of greenhouse gas such as CO2 (energy transition).

Depending on the depth from which heat is withdrawn from the soil and/or stored, different types of geothermal heat are mentioned:

• Ultra-deep geothermal – more than 4.000 meters, also known as EGS Enhanced Geothermal Systems and Hot Dry Rock. Use: collective application and generating electricity.

• Deep geothermal– 1.500 - 5000 meter. Use: collective applications such as residential areas and greenhouses.

• Mid-deep geothermal - 500 - 1.500 meter, also called HTO (Higher Temperature Storage).

• Soil energy or shallow geothermal - until 500 meter. Use: heat and cold recovery and storage, especially for heating and cooling of buildings. In practice, use is usually limited to about 200 meters. There are two types of systems:

• • Open soil energy systems, using geothermal water directly as a heat carrier. Water is pumped up, used as a source of heat or cold and then returned to the soil.
• • Closed soil energy systems where heat is exchanged with the surrounding soil using closed underground piping systems or buffers and heat exchanger. There is no direct contact with geothermal water.

This depends on the type of system:

• Hydrothermal systems: The heat comes up by drilling a geothermal reservoir. For geothermal production, two drilling are made, a production well and injection well. These wells together are called a doublet. At the final depth they have a mutual distance between 1200 and 2000m. Hot water is extracted from the production well. A heat exchanger draws heat from the pumpedup geothermal water and deliveres it to a heatgrid that provides homes, greenhouses or industry with heat. The cooled water is pumped back into the soil via the injection well. So the soil pressure remains the same. The production well and injection well can be changed seasonally, resulting in a "hot" and a "cold" source, and there may be a storage system. Different configurations are possible, which are commonly known under the collective name WKO systems (heat cold storage).

• Petrothermal systems: Through a borehole, by means of a borehole "Hydraulic fracturing" made gaps in the dry surface. Cold water is pumped into these artificial fractures and is heated by the rock. Through a second source, the warm water is pumped up to extract heat. Different names are usd for variaties of this technique, including Hot-Dry-Rock (HDR), Hot-Wet-Rock (HWR), Hot-Fractured-Rock (HFR) or Enhanced Geothermal System (EGS).

• By using Closed systems, heat is exchanged with the surrounding soil with an underground heat exchange system. There is no direct contact with groundwater. Cold or hot water is pumped through a closed pipeline system into the soil. If the liquid is colder than the surrounding soil, the liquid increases heat, the liquid is warmer than it cools in the bottom.

At this point, in Holland the most interesting are drills in the aquifer (layers with water, generally sandstone packages). These water-bearing layers are present in many parts of the Netherlands.

The benefits of using geothermal heat for nurseries can be particularly high:
- huge energy savings
- more certainty about the long-term energy costs – in comparison with use of fossil fuels
- long economical life of the plants for geothermal heat - a geothermal source produces decades; A CHP is technically written off after 10 years.
- delivery Security: Geothermal heat is not depending on fluctuations in weather.

In addition, the recovery of geothermal heat is technically a reliable, proven technique, making use of the experiences of the oil and gas industry.

These benefits are achieved in particular through the establishment of collective installations which generate heat together and share investments. The generated heat can be spread over affiliated farms through a distribution network.

In recent years several geothermal wells have been drilled for greenhouses. These wells evolve over time so well that heat is to deliver to third parties such as nearby greenhouses, swimming pools, schools and homes. This creates heat clusters where the basic heat demand is provided by the geothermal source. Heating grid Alternatively, a geothermal installation can be incorporated into a heating grid: a kind of heat ring where different parties enter heat on the pipeline network, for example, by residual heat, bio-mass or CHP and other parties withdraw heat. A covering renewable heat supply can be created for an area.

Horti-Cultura is involved in the development of these clusters and ensures that the heat from this source is also used as much as possible in the summer months, thus increasing the number of hours and the source is more efficient.

A heating grid is an infrastructure where various providers and customers of heat are connected. Through the distribution network, the heat is transported between the participants. This way a covering renewable heat supply system can be created for an area.

Other names used for a heating grid are heating network, district heating and cooling (DHC), heating ring, heat cluster and common carrier. The group of organizations involved in a heating network is also mentioned heat cooperation, heat alliance or heat collective.

A heating grid can be realized on various scales, for example local or provincial. Customers are heating and cooling of houses (district heating and cooling DHC), greenhouses and industry. The providers on a heating network can supply from different sources, for example: geothermal heat, residual heat, WKO (Warm Cold Storage), bio-mass.

Most of the energy we use comes from natural gas, coal and petroleum. These fossil fuels have the disadvantage that the use of these energy sources generates gas CO2 (carbon dioxide), which contributes to global warming. In addition, these sources are slowly depleted. In the future, we will increasingly need to use other energy sources that do not run out and do not pollute.

At present the best contenders to reduce CO2 emissions as quickly as possible seem to be residual heat, heat cold storage, geothermal energy and biomass.

Electricity generation and various industrial processes generate heat that can not be used on site. This residual heat can be used by another party as useful heat, for example, for heating homes, greenhouses or offices. Utilizing residual heat can be financially interesting and makes the energy chain more efficient and leads to CO2 reduction.

Power plants, waste incinerators and industry are the major suppliers of residual heat. If residual heat is used collectively, a heat grid is the way to distribute it. Customers of residual heat are mainly utility buildings, housing and greenhouse horticulture.

Thermal storage is used to heat and cool buildings. It is a broad concept that refers to various forms of underground energy generation and energy storage. In the Netherlands, UTES is mainly used in utility buildings, greenhouse horticulture, housing and data centres.

There are roughly two types of storage systems for underground energy storage. In a so-called Open system, groundwater is pumped (extraction source) and re-infiltrated after exchanging thermal energy (infiltration source). The second variety is called a closed system and serves purely for storage of already generated heat. A liquid is pumped around without contacting groundwater. The storage takes place in a pipe system or buffer. Open and closed systems vary in capacity and efficiency. In general, open systems are used for large scale applications and are (thus) more efficient.

Increasingly, biomass is being used for the production of renewable energy, especially heat. This application is significantly promoted by grant schemes. In addition, there are more and more new applications in the production of bioplastics, cosmetics and so on. Biomass differs from wood and wood / GFT waste to manure and animal oils and fats. Examples:
- Cape of wood from production forests
- Remains of trees remaining after cutting / thinning of forests
- Waste and residual flows released after industrial processing, such as wood sawdust
- Cultivation of crops like cane, corn, oilseed, rapeseed and grass like miscanthu - Residues of crops such as straw and stems not suitable for food production
- Waste and residual flows released after industrial processing after use or consumption of agricultural products (sewage sludge, GFT waste, animal manure, textile)

Use biomass for the generation of heat, possibly in combination with or thanks to the generation of electricity, can be done in the following ways:
1. Direct combustion of biomass:
A. Heat-power coupling (CHP) for the generation of heat and electricity;
B. Boilers for heat and / or steam production for heat and / or electricity;
C. Wood stoves;
D. Waste incineration plant (AVI) - combustion of biogenic fraction of waste stream

2. Biomass fermentation with biogas production:
A. CHP with heat and electricity generation;
B. As fuel in boilers for heat and / or steam production;
C. Upgrading to green gas for further distribution;

3. Gasification of biomass with combustible product syngas;

4. Fuel (think of wood pellets) for power stations by bending and drifting, producing large-scale electricity and aiming to use the residual heat.

Biomass thus has a wide variety of energy applications, where wood stoves, pellet kettle cvs, wood pellet boilers, manure digesters and bio-oil wkk plants are a few examples. (Text based on “Nationaal Warmtenet Trendrapport 2017”)

Energy storage makes it possible to collect excess thermal energy for later use - hours, days or many months later. This is a broad concept, indicating different forms and techniques of energy storage. It is considered to be an important means of balancing supply and demand for thermal energy, both on a small scale and on a large scale in, for example, a heating network. In the Netherlands it is mainly used for utility buildings, greenhouse horticulture, housing and data centers.

Examples of heat storage are:
- peak shaving: dealing with peak moments in energy consumption, preventing occasional high and expensive gas usage. For example due to large temperature differences between the inside and outside)
- backup, for example, in case of failure or maintenance of main heating installation.
- seasonal use of thermal energy, for example, difference between summer and winter.

The term "thermal energy storage" is often used in conjunction with terms such as heat storage, heat buffer, soil energy, WKO (heat cold storage), high temperature storage (HTO) storage, seasonal energy storage system (STES) and shallow geothermal energy. This is because of the use of terms for the many possibilities of energy sources and storage media.

The heat can be generated from various sources, such as solar energy, CHP, soil heat, (ultra) deep geothermal heat, residual heat and heat from biomass.

Thermal energy storage media include: overground buffer tanks, closed underground piping systems or buffers, and ground storage itself in acquifers (watering layers) or underground rock that can be utilized by humans by means of geothermal installations.

Open and closed systemens soil energy thermal energy

There are roughly two types of storage systems for underground storage. In a so-called open system, groundwater is pumped (extraction source) and re-infiltrated after use (infiltration source). It is a system where heat and cold are stored in a watering layer in the earth (acquifer). In this layer, groundwater sources are drilled. The groundwater is pumped and used in the summer to cool and to heat in winter. A heat exchanger ensures the groundwater temperature transfer. In addition, a heat pump is used almost always to increase the temperature for the delivery system in the building.

The second variety is called a closed system and serves purely for storage of already generated heat. A liquid is pumped around without contacting groundwater. The storage takes place in a pipe system or buffer.

Open and closed systems vary in capacity and efficiency. In general, open systems are used for large scale applications and are (thus) more efficient.

The main part of your heating system is the burner-boiler combination. Not only can we advise you about buying a new boiler, we also have a lot of experience in renovating, modifying, extending and maintenance of boiler houses. For example, the fitting of a geothermal plant into an existing installation.

A CHP plant can be a good addition to your boiler. A combined heat and power coupling plant is a large generator that generates electrical energy and heat. If more heat is generated than needed for your own use, then residual heat can be stored in a buffer tank and electricity can be sold to the grid.

Temporarily too much or too little capacity: heat storage

In order to make the most efficient use of your heating system, it is necessary to design and to use them as optimally as possible. The collection of over- or under capacity is as an essential element. There are various methods to deal with this. n diverse methoden om daarmee om te gaan.

You can use a buffer tank, a storage tank for hot water, in which is stored too much generated heat for later use. This may be moments when the boiler and / or CHP produces no heat due to failure or maintenance, if it is not interesting to make electricity or to deal with peak energy consumption.

Heat can also be stored in the ground, at more than 500 meters depth (ground buffer).

Overcapacity can also be supplied to another party via a heat exchanger or - in the case of electricity – be offered on the APX. If there is (temporary) lack of capacity, you can consider buying in residual heat from biogas plants, power plants, factories, etc.

Optimizing return temperature
By additional cooling the flue gases of the CHPbelow the dew point you gain energy back which otherwise would disappear through the chimney. This can be realize by engineering the central heating systems in cascade-shape, or insert additional flue gas condenser and heatpump. Also possible is cooling delivered waste heat from biogas plants or external power via common carrier systems.
WKO greenhouse cooling, floor cooling
In some cases, there is a combination of greenhouse heating, and greenhouse cooling, for example in the cultivation of freesia- or alstroemeria. The soil can be cooled with a chiller and heat/ cooled energy ? can be transported through the canals. It is more energy efficient to store this heat, and to use at a time when it is needed.

CO2 and biogas
Reduce greenhouse gas emissions through the use of bioenergy. Learn more in the article Cows and greenhouses.

Heating systems

The distribution of generated and stored heat through the greenhouse complex takes place via main distribution lines and group distribution to the type of heating of your choice: pipe rail heating, vegetation heating, snow heating, monotrail heating, gable heating, table heating, lift heating, air heating.

A greenhouse is a always in motion. Good monitoring and maintenance are necessary to ensure optimum growth environment and efficient management. We can assist you, f.i with the following products:

Energie Scan HortiMedes

A complete energy scan of a greenhouse. In cooperation with the grower an extensive inventory is made. We use a checklist developed by us so that nothing will be overlooked. These data will be processed by us into a punctual reporting of possible measures and an estimate of the energy savings. Conducting a comprehensive Energy Scan is one of the specializations of Horti-Cultura. Read more on the Energy Scan page


Maintenance and Safety

Interactive maintenance and safety program for greenhouse heating and CO2 system. The grower can determine when carrying out maintenance and, if desired, spreading over the year. Convenient for CO2 dosing, heating and crop changing season.