When people think about renewable energy, solar panels and wind farms usually come to mind. A lake down the road probably does not. But Europe's lakes, rivers, reservoirs, and coastal waters could become a crucial source of thermal energy for heating and cooling in the future, according to new research from Lund University in Sweden. The researchers estimate that these bodies of water could provide the heating and cooling needs for about 18 percent of all European households. The findings suggest that a resource many people largely overlook could play a much larger role in Europe's move away from fossil fuels.
Water as a source of comfort
The idea hinges on existing technology: water-source heat pumps. These systems do not generate heat in the traditional sense. Rather, they harvest thermal energy that is stored in the water and transfer it to a building. In the winter, heat from an adjacent lake, river, or coastal water can be used to warm a building. During the summer months, the process can be reversed to cool a space by transferring heat from a building into the water. According to the study published in Nature Communications, millions of Europeans live close enough to suitable water bodies to benefit from this approach. Surface waters represent a vast and largely untapped energy resource, according to the researchers who wrote in the paper.
Why the research is gaining attention
Europe is facing a challenging task: trying to reduce carbon emissions while residents continue to struggle with high energy costs. At the same time, rising temperatures are making cooling increasingly necessary, even in parts of Europe where air conditioning has not traditionally been common. Researchers say surface water heating and cooling systems can help solve both problems. The study determined that there is a significant amount of accessible thermal energy in Europe's lakes, rivers, reservoirs, and coastal waters to meet a portion of residential energy demand. This potential is particularly high in some parts of Europe and in areas with many large bodies of water. They calculated that a significant share, almost one in five, of the heating and cooling demand in Europe could theoretically be met.
Not just in countries with a lot of lakes
Although Scandinavia is well-known for its many lakes and rivers, researchers point out that the technology can be implemented outside of northern Europe as well. Reservoirs, rivers, and coastal areas can serve as a heat source and sink. This means that areas that are densely populated and do not have many large, inland lakes could still benefit. Using data for the entire continent and modelling, the researchers were able to determine where the technology could be deployed and the approximate amount of energy that could be extracted. Their results show that there is much untapped potential across Europe.
The growing demand for cooling
The timing of the research is also important. Europe is warming more rapidly than the rest of the world, according to the European Environment Agency. Heatwaves are becoming more intense and more frequent, meaning the need for cooling is steadily growing. Experts agree that energy planning must take into account rising summer temperatures more often, not just cold winters. The key advantage of water-based thermal systems is that the same infrastructure can serve both needs.
Limitations and drawbacks
Researchers say that while the potential is there, wide-scale adoption will not happen immediately. The system will require significant investment and careful planning, as well as suitable geographical conditions. It is crucial that extracting or depositing heat does not damage aquatic ecosystems. Even with these caveats, however, the findings illuminate a resource that has received much less attention than other renewable options. As Europe continues to seek clean ways to heat and cool its buildings, the solution may not always lie in entirely new technology or distant energy projects. For a significant number of European homes, the answer might just be found in the lake, river, or strip of coastline nearby.
