Is there an environmentally friendly and sustainable way to heat and cool buildings? The answer may be right under our feet. Aquifers, formations of porous rocks or materials such as sand and gravel, can be exploited as gigantic natural "batteries" thanks to a technology called Aquifer Thermal Energy Storage (ATES).
An energy treasure underground
Aquifers have the ability to store thermal energy due to the Earth's insulating properties. By exploiting these characteristics, it is possible to transfer thermal energy to buildings above ground without using natural gas or electricity from fossil fuels. This form of geothermal energy involves two separate wells, one hot and one cold, that connect the surface to the groundwater below.
During the winter, water is pumped from the hot well, which has a temperature around 15 degrees Celsius, and passed through a heat exchanger. Together with a heat pump, this process extracts heat from groundwater to heat indoor spaces. The now colder water is then fed into the second well, creating a reserve of cold water to be used during the summer to cool the buildings.
Because pumps and other equipment run on renewable energy, such as solar or wind, this hydrothermal system helps reduce the demand for fossil fuels and limit carbon emissions. A new paper published in Applied Energy (I link it here) he says that ATES could reduce the use of natural gas and electricity for heating and cooling by up to 40%.
Aquifers, technology is not for everyone…
Despite its many benefits, ATES technology is not yet widely adopted globally. Around 85% of ATES systems are located in the Netherlands, where the geology is favorable and there are strict national standards for energy efficiency. However, recent studies have shown that large areas of Germany and almost a third of the Spanish population live in areas suitable for ATES. And Italy is also in good shape, as you can see from this map. The "leaders" who could exploit this technology more than others are Piedmont, Emilia Romagna, Tuscany.
ATES technology is not suitable for all areas, of course, as it depends on a number of complex geological factors. These are very low enthalpy geothermal reservoirs. For example, a city built on solid rock would not have easy access to an aquifer, and even a city with access to an aquifer would need sufficient “hydraulic conductivity,” that is, an ease of flow of water through underground materials such as sand and gravel. ATES also presents obstacles, such as the high costs associated with the geological analysis of the aquifers, and the installation of drilling and pumping equipment.
…but where it can be done, it works
Once the wells and pumps are built, the system runs on free, abundant solar or wind energy. ATES takes up little surface space, leaving room for urban gardens and other open green areas that cities increasingly need. And these are not the only advantages that technology offers: first of all, a reduction in dependence on non-renewable energy resources and a lower impact on the environment. ATES is particularly suited to large buildings, such as hospitals or groups of buildings such as colleges, which may share a dedicated facility for wells and other equipment.
If you are willing to invest initially to improve climate resilience and become more sustainable, aquifer technology is an ideal option. With growing awareness of climate change and the need to reduce greenhouse gas emissions, ATES could become an increasingly popular solution for a sustainable energy future.
