The new residential area in Ranagård in Halmstad, Sweden will profit from a 4th generation district heating system with a 3-pipe system. The third pipe is used to circulate the supply water when the heating demand is low, replacing the circulation in buildings. The circulation in the third pipe enables lower return temperatures and is therefore more energy efficient.The pilot testing measure has been implemented by Halmstadt Energy and Environment (HEM).

The residential area will be provided with low temperature district heating for approximately 500 houses and apartments. Ranagård is divided in three areas where area 1 will be supplied with 4th generation district heating, 4GDH-3P, and area 2 and 3 will be supplied with low temperature district heating, LTDH. Ranagård has a total maximum heat demand of about 3 MW. The first goal of the pilot measure was to test and compare advantages / disadvantages with the three-pipe system in terms of energy efficiency, construction, etc.

Additionally, the difference in construction design between the 3rd generation district heating and 4th generation has been investigated. Due to the difference in construction design between the 3rd generation district heating and 4th generation, a practical field test was conducted to determine the minimum amount of space needed between the pipes outer casing to be able to build a tree pip district heating grid.

HEM has also performed calculations tests to get the right dimensioning for sufficient flow with minimal energy losses. As a result of the field test, a “standard section” was formed with the measurements. Using these measurements ensures the fitting of casing joints and an easy assembling of the pipes. The test saves time and effort during the construction phase starts and will also reduce the amount of readjustments of the trench to be able to lay down the pipes correctly.

The third major challenge in this pilot was the design and dimensions of the downshift stations needed to build a low temperature district heating grid in a high-temperature and existing grid. In the Ranagård area, three sub-areas are being built to compare the different systems. One network for three-pipe systems and two networks for two-pipe systems with low temperature water.The networks in will be connected to the conventional district heating network in Halmstad by two technical buildings. In the technical building the supply temperature of the conventional network is lowered to the supply temperature in the LTDH and 4GDH-3P. The temperature is lowered by mixing the primary supply with the return of the LTDH and 4GDH-3P.

The advantages of a modern and energy-efficient district heating network are numerous. A network that allows energy to flow in and out depending on needs and that is designed so that the losses are as small as possible, of course is the best solution. With three pipe systems, energy losses are reduced. With low-temperature water, the network can both deliver and more easily receive surplus heat. The return temperature can be lowered, which makes the incineration plants more efficient. A more efficient incineration plant saves energy and reduces emissions. All in all, this creates a better environment but also a basis for more flexible business models. Even if the grids are static, the use and way of doing business with energy can become flexible and thereby be adapted to different customers and its changing needs.

The next step in the work, which has already begun at Ranagård, is to build the infrastructure clearly in the area with roads, water, sewage, fiber and district heating pipes. When the expansion of the infrastructure is completed, various contractors will develop the area. Single-family houses and multi-family houses will be constructed. During the work, the efforts and results will be evaluated.


Article prepared by Halmstadt Energy and Environment