HOT|COOL NO. 1/2020 - "How to District Energize your City"

energy TEO concept In the summer the surface water is warmed up by the sun. In Dutch cities the warming up leads to excessively warm surface water. In extreme situations the temperature of the surface water rises to >25˚C. This has negative effects on the water quality and contributes to the urban heat island effect. TEO could be part of the solution to counter these effects. By extracting part of the heat from the surface water, the water cools down. This is in principle beneficial to the water system and the urban environment. The heat is stored in, for example in an Aquifer Thermal Energy Storage (ATES), and is distributed with a DH grid to the buildings in the area for heating when needed. Enhancing the temperature can be performed at different moments in the system, for example collectively before distributing in the grid or individually as the water enters each building. As there are no extensive DH grids in The Netherlands, DH is still limited. The options for implementation are still under consideration but currently are: • a low temperature (20-30˚C) DH grid and individual heat pumps (or per block of houses); • a medium temperature (40-50˚C) DH grid (boosted with a collective heat pump) and individual booster pumps only needed for tap water ** • a medium temperature (40-50˚C) DH grid with a collective heat pump to 70˚C, no individual heat pumps are needed. Research has also been completed on storing the heat in an ATES at a higher temperature (40-70˚C). The heat temperature is boosted during time of a sustainable electricity surplus and is stored at a higher temperature in the ATES. However, legislation in The Netherlands does not allow this method yet. The TEO principal can also be applied outside the urban environment or even with sea water. The latter has already been applied in Scheveningen in the past and is currently being investigated for implementation at the Wadden Islands. District heating grids The most cost valuable item in the aquathermal heat chain is the installation of the DH grid. The Danish District Heating Model with publicly owned companies could be the most appropriate for implementation in The Netherlands. However, theDutchheatingmarket is not regulated and there is currently an ongoing discussion on this matterfrom both public and commercial. Commercial companies want their investment payback time to be shorter in comparison with publicly owned companies. The return on investment period for creating DH grids highly effects a technique as aquathermal energy, in comparison to all-electric solutions without DH grids. Add to

A.J. (Arianne) de Vries Energy transition consultant

Rijkswaterstaat Water, Verkeer en Leefomgeving (WVL) Department of knowledge and innovation management R.P. (Reinier) Romijn MSc. Policy advisor Energy, water en spatial planning Dutch Water Authorities

that, the costs of a DH grid are for a large extent determined by the chosen configuration. The Ministry of Economic Affairs and Climate has not made this decision yet. The ATES is another expense. Not installing an ATES leads to a lower energy efficiency, but the development costs will decrease. Governance Although the concept is technically rather simple, in governance terms it is quite complex. This complexity rises from the fact that a large number of parties are involved in the heat chain form source to building and because there are many degrees of freedom in the Dutch energy transition, for example an individual household cannot be obliged to participate in a collective solution such as a DH grid. The fact that the use of aquathermal energy is a new technology that has not often been applied on a large scale makes project developers, government, investors and housing corporations uncertain on the financial aspects and the reliability of the system. The system cannot fail when the demand for heat is high. The concept will have to prove itself on a large scale, if it’s to become mainstream. Unique selling points Aquathermal energy has unique selling points, such as: local sustainable heat, it is available almost everywhere in The Netherlands, it can be developed quickly, has a relatively low electricity consumption, no uncertain drilling is required, it is scalable heat (1 – 10.000+ homes, the sources are quite reliable and the water authorities are fairly reliable as (semi) public administrations. In addition, it is a bonus for the Dutch that heat from water is used as a sustainable source for the heat demand in the energy transition. Finalizing Aquathermal energy is a unique source of heat. In The Netherlands, due to the high density of waterways, the source has a great potential to partly provide in the existing and future heat demand. To this end, a large number of parties, together with the water authorities, are committed to further develop this technique into usable concepts for large-scale projects as opportunity in the transition from natural gas to sustainable heating. The concept is technically not complex But there are complicating factors, such as the barely developed DH system. The Netherlands wants to use the water as an energy source for sustainable energy for heating and cooling and is curious how other countries manage this source.

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** Dutch legislation states that the water for use as tap water must be heated up to >65˚C at least once a week in order prevent legionella.

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