The river provides indoors cooling

The Dutch are always finding new ways to use their water. In the city of Rotterdam, the river Maas is now used to cool the huge multi-function building De Rotterdam. Through the heat exchangers that are installed cooling is delivered throughout the year, actually covering the entire need with free cooling as long as the river temperature is below 9°C (48°F). When the temperature rises above that, screw compressor chillers cooled by the river water kick in. At a water temperature above 15°C (59°F), the free cooling is totally phased out.

Idea and Layout

The building De Rotterdam Vertical city was finished in late 2013 taking four years to complete. It is constructed as a "vertical city", hosting all the functions needed in a city; housing, offices, shops etc. This mixture of functions requires both heating and cooling to sustain a good indoor climate, and it uses water from the nearby river Maas for free cooling. The water that is used has a temperature that varies between 3-27°C over the year. Cold is centrally generated through three water-cooled compression chillers through a cold water inlet connected to the river New-Meuse. Cold to the homes is provided through a distribution set with a metered connection.

Figure 1. Scheme of cooling solution Vertical City by Eneco.

The river water is pumped through a coarse filtration system to prevent solids and fish in the river from getting sucked into the water pumping system. Thereafter the water is processed through an antifouling system that uses chlorine as the antifouling agent. The water continues through a second stage of filters before passing through a heat exchanger.

Problems during the early stage of the project occurred with small organisms, such as clams, that passed through the filter system. When settled, the organisms grew causing problems in the system. An environmental-friendly extra anti-fouling step is used to solve this: thermic shocks. This method is used to prevent small organisms and clams from growing inside the system. The small eggs of the clams can pass the filtering system and stay inside the heat exchanger system. When growing they obstruct the flow in the system. By periodically raising the temperature to a high degree in a short term, called thermic shock, the clams and other small organisms are unable to hold their grip on the inner surface of the system and are flushed out.

The system is also connected to electrically driven river water-cooled screw compressor chillers used when the river water temperature is too warm and supplementary cooling is needed. The river water chills the cooling medium that passes through the chillers which in its turn chills the water that is distributed to the buildings. The buildings are then cooled by different heat exchange systems that cool the air. The river water is returned to the river after passing through the chillers and heat exchanger. The water supplied to the building has a temperature of approximately 8-12°C while the returning warmed water has a temperature of approximately 16°C.

Apart from cooling, the entire energy system of the building also includes heating and electricity. The heating system is partly fuelled by district heating and the electricity partly has its origin in the net-power. Both heating and electricity are also provided by bio-fuel cogeneration. The building as such also has a good sustainability score: it is built 7 to 48 per cent better than the Energy Performance Building Directive (EPBD), depending on the function.

De Rotterdam is constructed as a city of its own and has a total floor space of 160,000 m2 realised on a very small footprint of only 5,500 m2. It’s the most densely built part of the Netherlands with a floor space index of 32. It consists of 240 apartments, 60,000 m2 of offices, 1,500 m2 for restaurants and cafés, 278 hotel rooms, cultural institutions, 5,000 m2 of shops, 2,500 m2 of fitness-area and 670 parking spots.

Impact

Figure 2. Masterplan cooling around Vertical City (or De Rotterdam). Contribution by the City of Rotterdam (a Celsius partner).

When the river temperature is below 9°C the buildings are cooled with free cooling only. When the river temperatures vary between 9-15°C a combination of free cooling supplemented with chillers are used while when the river temperature reaches above 15°C only river water-cooled chillers are used to cover the cooling demand of the buildings. According to the energy company, Eneco, the coefficient of performance, COP, varies from a COP of 5 when only the chillers are used and can reach up to a COP of 40 when only free cooling is used.

In the basement of De Rotterdam a large space is reserved for a cooling station, to have large compression chillers and distribution network equipment. All new buildings close to the vertical city will be connected to that. The overall demonstrator’s performance is summarized in the following table according to 5 evaluation criteria. It can be noticed that the assignment of all the scores is directly linked to the values calculated for the Key Performance Indicators, except for socio-economic benefits where a qualitative assessment is carried out based on this cluster’s indicators and on separate interviews.

Replication potential

Technical requirements

Important, of course, is that water is available close to the building. Since the water temperature is not very high, longer distances can be used because the thermal losses will still be small.

Stakeholders

External links:

Vertical City - A solution for sustainable living, Vertical City De Rotterdam, City of Rotterdam