This approach, we had the opportunity to test, or demonstrate, in the REWARDHeat project, funded by the EU Horizon 2020-programme.
grid. With no grid division, the DH plant's temperature should be much higher than 60 degrees to provide the last customer with 60 degrees DH. With this approach, many of the end users would never reach LTDH. Instead, Albertslund Utility will supply higher temperatures in the main pipes and then lower the temperatures with shunt valves to the end users. Even if the temperatures in the main pipes exceed 60 degrees, the temperature will be much lower than today. Albertslund Utility expects to have around 35 shunt valves in operation in a few years. The heat loss is bigger in the small pipes With the use of shunt valves, more end users will be supplied with LTDH – compared to a central lowering of the temperature. Thereby, the temperature is lowered in a greater part of the entire net. The shunt valves increase the overall efficiency and limit the overall heat loss in the grid. The heat loss in the main pipes is smaller compared to the heat loss of the smaller pipes supplying the end user with DH. In Albertslund, the heat meters are placed indoors by the end users. Therefore, all the heat loss in the grid is covered by the utility – or included in the heating price. Shunt valves improve the flexibility Probably the most important thing learned from the work with shunt valves is the flexibility obtained in the grid – flexibility concerning temperatures and flexibility regarding the pressure in the pipes. For example, if one housing area needs higher temperatures on a cold day, Albertslund Utility can increase the temperature in this area while keeping the temperature lower in other areas. The DH grid of Albertslund has been in operation for 60 years and is dimensioned as a 6-bar grid. When lowering the temperature, a given need for energy will result in a larger flow of water. It can be solved with larger pipes and/or with higher pressure. Traditionally, the DH pressure is created from the DH plant or with strategically placed booster pumps in the grid. However, according to the local circumstances, shunt valves can increase the pressure locally for each individual DH area. Therefore, Albertslund Utility can lower the temperature in the existing
rent a new DH unit from the utility. To participate in the service, house owners need sufficient radiator capacity and adjustable valves on the radiators. Catarina Nørgaard Marcus-Møller explains, “The question was how to move a step further towards LTDH in Albertslund. We came up with the idea, and with the help of shunt valves, to divide the grid into smaller islands or temperature zones. Thereby we can target our work towards smaller limited housing areas. We can lower the temperature stepwise in one single area without other areas having to wait for lower temperatures. With this approach, we had the opportunity to test, or demonstrate, the REWARDHeat project, funded by the EU Horizon 2020-programme.” An EU project showed the way In 2020, with the REWARDHeat project, Albertslund Utility installed a Grundfos iGrid-shunt at the end of a typical Danish street with one-family houses from the 1960s. The DH temperature was lowered step by step, with the return temperature from all 104 houses being monitored. Troubles were expected but never really occurred. In February 2021, the whole street was supplied with 60 degrees LTDH, even though the outside temperature was below zero. Five houses had needed consulting. In three houses, smaller adjustments were made without changing any components. In one house, a smaller component was changed. And in the fifth house, the heating unit was changed. The learnings from REWARDHeat and the street named Porsager strengthened the belief in fulfilling the strategy of lowering the temperature in all of Albertslund. Lowering the temperature by 20-30 degrees on a cold winter day in an ordinary Danish housing area was much easier than expected. Due to the REWARDHeat experience, the last two housing areas of Albertslund, heated by natural gas, were converted directly to LTDH areas in 2023. The use of shunt valves became permanent when the benefits became clear The work with shunt valves has changed in Albertslund. Initially, shunt valves were regarded as a temporary component in the grid, awaiting the lowering of the temperatures in the DH grid. Today, shunt valves have become a permanent part of the DH
16 HOTCOOL no.6 2024
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