The Netherlands lives with water. The world-famous water management techniques have proven invaluable for a country with 26% of its territory below sea level and another 29% at risk of river flooding, as taken from PBL. And in the face of climate change, these systems will become even more urgent.
The Dutch waterworks have found their way to all landscapes, except for one. The city. There is the last landscape that still experiences a risk of regular flooding. Albeit not life-threatening, flooding in a city the size of The Hague will cause substantial damage and associated repair costs. But what if the city could create a massive water storage capacity, making it in essence a large sponge, while simultaneously reducing heat stress and energy demand.
Mainly designed on the well-proven principle of a water-water heat pump, some neat hypothetical additions can be added. The system boils down to a series of insulated underground water storage tanks and above-ground pipes. The pipe grid will run both through the building’s interior and as a trickling waterfall through the façade. The logic behind it is very simple. During summer, cold water from the tanks will be pumped through the building’s façade, cooling both the building and reducing the heat-island effect felt on the street by absorbing and transporting the sun’s heat away from the surface. This practice of transporting heat is very common in space applications and could also have large benefits in civil applications. By using this technology, the water will heat up, creating a buffer of thermal energy. Come winter, this thermal energy can be used to heat the connected building, reducing further need for gas or electric heating. In this way buildings will have a positive effect on the temperature of their surroundings as well as reduce their energy bill sustainably.
Besides the heat-island effect, cities of tomorrow (especially in the water country that is the Netherlands) will also have to deal with heavier rainfall. At the moment, cities scramble to create water retention capacities to store the water in such an event. Enter the system described before. By connecting the system to the storm sewer, a massive water retention capacity can be realized, for very little extra cost. Now the system has the added bonus of reducing nuisance from heavy rainfalls combined with limiting the effects of summer droughts.
According to the International Energy Agency (IEA) water has a minimum energy storage capacity of 2000 kWh/ton and is capable of storing this energy for up to a year. Given that thermal energy storage is well proven, yet bulky, underground applications should be well possible. In addition, cooling buildings by waterpipes through the roof has also been proven efficient back in the 1970s in New Delhi, India.
Where climate adaptation is now mainly seen as a necessary pain to keep the city livable in the face of climate change, implementing project Sponge will transform this into an opportunity. Creating revenue by tapping a new renewable energy source, while simultaneously installing all required climate adaptation measures with innovative green and blue technology.