Integrate water and energy systems to deliver clean, reliable and affordable energy supplies

To combat climate change, efforts are being made worldwide to wean the energy system off fossil fuels and use cleaner, renewable sources of affordable and reliable energy. That involves a range of challenges.

Challenges in the transition to renewable sources

For example, the cost of producing renewable energy is falling but the availability of the materials needed required may become a limiting factor. And many of the renewable sources are not continuously available: wind and solar are not always available at the times and places where energy is needed. How are we going to match energy supply and demand in space and time? In addition, renewable energy sources primarily produce electricity, which is more difficult to store and transport than fossil energy carriers. Alternative renewable energy carriers are therefore needed. Renewable energy production is also more decentralised than fossil energy production, and this represents a challenge for energy infrastructure.

Multi-energy system

Designing a 100% renewable energy system requires an integrated system approach that links various sectors (energy[GS1] , the built environment, mobility, industry, water) which exchange a range of energy carriers between them (such as electricity, heat/water and gas, liquid or solid fuels). That results in a multi-energy system. The use of different energy carriers makes it easier to store energy, as does matching supply and demand in space and time.

Els van der Roest during the PhD ceremony in Delft on November 15.

Water and energy sectors closely linked

The role of the water sector in an integrated system design of this kind is extremely important for two reasons. For example, the water and energy sectors are already closely linked. Water is needed for the production, storage and transportation of energy and, conversely, energy is needed for the production, storage and transportation of water. But above all: the water sector has goals and challenges that are similar to the energy sector in the context of climate change. There is the increased risk of flooding and drought, potentially affecting the reliability, the security of supply and the safety of the water system. That is why Els van der Roest, who was a researcher at KWR until recently, focused her doctoral research at Delft University of Technology on the integration of energy and water systems in an urban environment. On 15 November, she successfully defended her thesis Energy and Water system integration in the urban environment in the presence of her supervisors Professor Ad van Wijk and Professor Jan-Peter van der Hoek.

System integration essential

Van der Roest argues in her thesis that system integration is essential for the transition to a clean, reliable and affordable energy system: “It makes it possible to design a clean, affordable and reliable water and energy system for a local area. For example on the basis of the Power to H3 concept, which includes not only the integration of different energy carriers such as electricity, heat and hydrogen, but also the seasonal storage of heat and hydrogen, the integration of residual heat sources, and combined energy and water elements. In existing neighbourhoods, the diversification of energy carriers helps to achieve a smooth and timely energy transition.” Van der Roest also believes seasonal heat storage will play an important role in the design of a multi-energy system: “It allows you to disconnect heat supply and demand, and that makes it easier to provide renewable heat throughout the year.” She also argues in favour of changing the regulations for new buildings to support the installation of blue-green roofs and solar PV systems, for example by imposing less stringent requirements for energy production on roofs that also serve other functions, such as absorbing peak rainfall (climate adaptation), local water treatment, biodiversity, cooling of the surroundings and a pleasant living environment.

In short, Van der Roest is in favour of the following approach to designing a water and energy system for a local area:

1. Maintain the connection with the central system but, as a local area, respect the limits of the current infrastructure as much as possible
2. Explicitly incorporate hybrid options (combinations of energy carriers) in the energy system in existing neighbourhoods
3. Include the subsurface as an essential component in neighbourhood design
4. Look for multiple values from both the energy and water perspectives
5. Initiate the combined design of both the energy and water systems for a local area as early as possible

Van der Roest has made major contributions to energy and circular systems research during her time as a researcher with KWR. Her former colleagues are carrying on that work with verve. Van der Roest recently joined the city authority of Utrecht to work on the realisation of the energy transition – and she will in all probability be regularly referring to the tenth proposition in her thesis: “Smiling more accelerates the energy transition.”

Els van der Roest received her PhD from TU Delft on November 15 with a dissertation entitled Energy and Water system integration in the urban environment.