Under the ground where you live, there is probably a kilometre-long culvert system. A central energy plant, for example, provides a full property portfolio with hot water to the various buildings. Transported in pipes that are located in a system of culverts, older systems are often poorly insulated with significant energy losses.
Before the 1970s, these pipes were often encased in an outer casing of asbestos cement, which was insulated with mineral wool or polyurethane foam (PUR). Heat losses in such systems can amount to 600 to 900 kWh per meter per year and if it becomes wet losses can be 10 times larger. Pipes installed after 1970 are double-walled, which is a significant improvement over the older pipes, but there is still a lot of heat that is lost on the way from the heating plant to the consumer.
Thick and square insulation
“We’ve developed a thick and effective insulation and can reduce energy loss in culverts in the order of 80 kWh per meter per year (6-10 W / m).
Distribution loss is about 70 percent lower compared to the conventional systems, “says Göran Olsson, who is CEO of Elgocell . “There are many old pipes and culverts that need to be rebuilt and our technology can contribute to this rapidly becoming a profitable investment. Well-insulated conduits are also of great interest for various energy companies. They are now looking to expand their district heating networks without unnecessary loss of energy in the ground between buildings or between communities.”
About 10 years ago, Elgocell developed along with a foam manufacturer a prototype for insulating pipes. The result was a product that in many respects is innovative. The insulation material is made up of thick foam made of expanded polystyrene (EPS), which is formed into square blocks. Together with the tubes, that consist of PEX (cross linked polyethylene), a complete culvert system is created.
“An EPS block is 2.4 meters long and placed into the dug pit where they are fixed with a special toothed piece of metal. The flexible PEX tubes are available in lengths of 50 or 100 meters. Supply and return pipes are rolled out, joined by a special connection and then placed in the cavity in the centre of the long line with EPS blocks. Then it’s time to put on the cap and refill the trench with sand and gravel,” says Olsson.
“In addition, the insulation is very efficient and we see several advantages with the installation where no heavy lifting is required and really need no special skills are needed to perform the work. The system has good properties in terms of durability and ability to retain the insulating properties.”
It has become common for farmers, forest owners, entrepreneurs and individuals to come together to form a local heating company. They assume responsibility for their own energy, and such small-scale plants are sometimes called “local heating plants.” The heat produced in a centrally located boiler and is shipped out to customers in a culvert system. Inside each building, there is a heat exchanger that transfers the energy to the heating system. The heat can be produced in different ways and wood chips and straw are common fuels, but in the future the bio-based heat could be combined with other renewable sources of energy, such as solar heating.
“In order not to lose valuable energy on the way to the properties it is important to reduce heat loss. The combination of bio-fuels, well-insulated pipes and low operating temperatures in the ground network, contributing to reduced environmental impact and affordability for small-scale heating plant”, says Olsson.
The article was published in November 2013