Sustainable energy, right beneath your feet
The planet we live in contains a natural and inexhaustible resource. Groundwater! It is a natural and unlimited resource for more than quenching thirst. Using groundwater for energy purposes – heating or cooling – can make massive energy savings and reductions in CO2 emissions. Thus, geo-energy plants are an essential part of the green transition.
By Lars Hjortshøj Jacobsen, CEO, ATES A/S
Co writer: Rasmus Victor Fauerholdt, CEO, Ingenioerhuse A/S
There are generally two ways to produce cooling energy:
- mechanically, energy-intensive but available everywhere, and
- free cooling, depending on location and season.
Most cooling systems utilize outdoor air and mechanical cooling, providing a stable and known course. The drawback is energy-heavy consumption in the summer when cooling is most needed.
Another solution is to combine mechanical cooling with groundwater, as groundwater has a constant temperature all year suitable for cooling or heat storage. Thus, a seasonally independent and energy-efficient plant is available – even in summer when cooling is most needed.
ATES systems
Groundwater-based systems, also called Aquifer thermal energy systems (ATES), are typically applied to provide heating and cooling to buildings by storing and recovering thermal energy – achieved by extracting and injecting groundwater from aquifers using groundwater wells. Systems commonly operate in a seasonal mode. The groundwater extracted in summer is for cooling by transferring heat from the building to the groundwater through a heat exchanger. Subsequently, the heated groundwater is injected back into the aquifer, which creates storage of heated groundwater.
In wintertime, the flow direction reverses, and the heated groundwater is extracted and used for heating (often in combination with a heat pump).
An ATES system uses the subsurface as temporal storage to buffer seasonal heating and cooling demand variations. ATES can be a cost-effective technology to reduce primary energy consumption and the associated CO2 emissions when replacing traditional fossil fuel-dependent heating and cooling systems.
Significant reduction of energy consumption and emissions
ATES systems are essential for countries to achieve their targets for global climate protection by reducing greenhouse gas emissions, increasing the use of sustainable energy, and improving energy efficiency.
An ATES system can reduce the energy consumption used for cooling a building by up to 90%. If the energy from the cooling season is recovered and used in a heat pump, it is also possible to reduce greenhouse gas emissions, as the heat pump often replaces gas boilers.
In this context, about 40% of the global energy consumption is used by buildings – mainly for heating and cooling, and ATES systems are worth considering.
Therefore, the development of ATES systems is shown a lot of attention worldwide, especially in Europe, where the Netherlands is the leading country with more than 2500 deployed systems. The ATES systems can be applied worldwide if the climatic and geohydrological conditions are right.
Groundwater is for drinking water.
The ATES systems must be safe and do not pollute the aquifer. But, even though we use our groundwater for drinking water, we can implement the ATES system in a district energy system – utilizing groundwater as a green energy source for electrical heat pumps when heating or cooling buildings. We have successfully done it many times: The first ATES system was from the 1980s. Since then, 60-70 systems have been deployed – even in challenging areas.
Standardization of ATES systems
The plants must be standardized and lifted to a functional industrial level for ATES systems to succeed in Denmark. ATES A/S and Grundfos decided to cooperate to produce and store thermal energy in a highly efficient, sustainable, and standardized way.
The first standardized system was deployed in 2015 at a data center in Copenhagen, in an area with well fields for drinking water – and a polluted property nearby.
A standardized system must be serviced worldwide, requiring only standard components from international industrial suppliers such as Grundfos, Danfoss, Siemens, etc.
Since 2015, about ten standardized systems have been deployed in Denmark, hopefully more abroad within the next few years.
The greenest hotel in the world
Crown Plaza Copenhagen Towers was built in 2009 and awarded in 2010 as the world’s greenest hotel. The hotel uses a third of the energy compared to similar hotels. One of the reasons is the ATES system provides the hotel with sustainable energy from the underground.
The Crown Plaza Copenhagen Towers system consists of 2 heat pumps and four wells – two for cooling and two for heat recovery. It provides up to 4,2 MW of cooling and approximately 2 MW of heating. The groundwater circuit covers the cooling baseload and 80-90% of the cooling energy. The rest of the cooling is produced on the heat pumps.
Crown Plaza uses the stored heat (from the cooling process in the summer) as an energy source for the heat pumps in the winter. The heat pumps produce 70-80% of the hotel’s heat consumption.
The standardized Grundfos solution now replaces the system.
No waste in the waste
The newest ATES system is in Bjerringbro at the local district heating company: a 6 MW heat pump based on wastewater. The wastewater is relatively cold in the winter when district heating is needed, so they built an ATES system storing the energy from the wastewater discharged through the summer. The energy is recovered and mixed with the heat energy from the winter’s wastewater discharge — all utilized in a 6 MW heat pump.
The local district heating company is also involved in another project: an ATES system provides cooling in the summer for the city’s industry, reusing the stored heat via heat pumps for district heating in the winter.
Large potential
We have considerable worldwide potential to use groundwater as an energy source for cooling, heat pumps, or both. ATES systems are an option when planning district cooling, new buildings, or renovating them. ATES is for synergies: optimizing the energy system and minimizing energy consumption and CO2 emissions!
For further information please contact: Lars Hjortshøj Jacobsen, lhj@ates.dk
“Groundwater!” was published in Hot Cool, edition no. 3/2020. You can download the article here:
