Optimized energy efficiency in CIPP lining: Innovative approaches
Energy efficiency is a term that is not uniformly interpreted. A subjectively good definition can be found on Wikipedia: “Energy efficiency is the ratio of service, goods, or energy (output) to the energy supplied (input). Energy efficiency is understood as the rational use of energy. Through optimized processes, the quantitative and qualitative losses that occur during the conversion, transport, and storage of energy should be minimized in order to achieve a given (energy) benefit while reducing primary and final energy consumption.” Increasing energy efficiency, like energy conservation, is an essential element of the energy transition.”
The question therefore arises as to whether the same output can be achieved with less input using efficient technology.
There are various motivators for improving energy efficiency:
■ Reducing CO2 emissions
■ Economic efficiency
■ Sustainability
■ Limited resources
■ Laws, e.g., the Energy Efficiency Act
Per Aarsleff A/S has prepared so-called EPDs (Environmental Product Declarations) for the most common CIPP liner types in accordance with ISO 14025 and EN 15804 and had them externally verified. A general problem with these declarations arises from the high complexity and fluctuation of global production chains. The more flexibly goods are traded, the greater the price advantages for the end customer. However,
EPDs can only reflect flexible product flows to a very limited extent. The EPD is a static snapshot, subject to fictitious boundary conditions and definitions based on the best of our knowledge and belief. The electricity mix of the individual product components forces the CIPP liner manufacturer to make one off assumptions.
However, the electricity mix can vary in practice in the supply chain for e.g.
■ Resins
■ Glass fibers
■ Synthetic fibers
■ Films and coatings
Bluelight GmbH, an Aarsleff subsidiary, sells various Aarsleff CIPP liners. Table 1 compares the CO2 emissions per meter of different CIPP liners sold by Bluelight GmbH.
It is striking that even with a relatively long transport distance of 500 km from the factory to the construction site, the CO2 emissions from transport are minimal compared to the CO2 emissions from CIPP liner production, including the precursors in the factories. Furthermore, it is noticeable that for the PAA GF pipe liner, switching from a styrene-containing UP resin to a styrene-free VE resin almost doubles CO2
emissions. This results from the significantly more energy-intensive production of the styrene-free resin compared to the styrene-containing resin.
This example raises the question: How should sustainability be assessed and weighted in the sense of a holistic environmental assessment beyond CO2 consumption? A sole focus on low CO2 emissions can significantly dilute the perspective of a holistic sustainability approach. Label-free, relatively expensive styrene-free resins have a significantly higher carbon footprint during production than inexpensive styrene-containing resins classified as hazardous materials. How should such different environmental impacts be weighed against each other in practice?
The distribution (Figure 2) shows the energy consumption for CIPP lining from production to installation and curing. It was previously shown that transport accounts for only a very small proportion of energy consumption compared to production. Although the energy consumption for installation and curing is significantly higher than the energy consumption for transport, it is still significantly lower than the energy consumption for the entire CIPP liner production process. The greatest potential therefore lies in all approaches to optimizing increased energy efficiency in production, such as:
■ Use of recycled fibers
■ Electricity mix in production
■ Optimized production
■ Bio-resins?
CIPP liner manufacturers already have a natural and strong interest in such improvements, as more efficient material production also improves economics and thus competitiveness and company profitability.
Another very important feature of a holistic environmental assessment is the final product quality and thus the service life. To simplify matters, CO2 balances can assume that CIPP liners manufactured with different energy efficiencies have the same service life. However, the actual service life of a CIPP liner depends significantly on the achieved final quality.
The final quality, in turn, depends largely on:
■ Proper planning,
■ The right product selection,
■ Optimal quality production of materials,
■ Professional installation and proper curing.
If a product classified as energyefficient according to the EPD achieves poorer final properties due to lesser suitability or a defective manufacturing process from factory to curing, the entire renovation project will only achieve a fraction of the service life of a possibly much less energy-efficient product that was nevertheless excellently manufactured and installed. Thus, a seemingly much less energy-efficient product can still
generate significantly less CO2 emissions over its entire life cycle than a seemingly more energy-efficient product. Purely static considerations are inadequate for a complex and relatively error-prone technology such
as CIPP lining.
In the case of pipe lining, errors in planning or execution can lead to a significantly lower output Y from input B compared to input A, which can achieve a significantly higher 
output X with good planning and
execution (Image 3). Modern and energy-efficient curing concepts can be realized in the future through the use of electrically powered trucks and hydrogen-powered steam generators. This is an example from Olimb, a Norwegian subsidiary of Aarsleff A/S (Image 4). However, the investment costs for such a system are at least 50% higher than the comparable costs of conventional system technology. For companies, such an investment is not worthwhile in a procurement system geared solely towards maximum price competition. Furthermore, the green hydrogen required for this plant will not be available in Germany or Denmark in
the foreseeable future. Due to its special topography and size, Norway has almost unlimited renewable energy sources. Green hydrogen is already a reality in the greater Oslo area, but it is an absolute exception in the rest of Europe.
UV Light Curing
UV light curing has established itself as a sophisticated, fast, flexible, and efficient technology. Using this technology, CIPP liners can now be installed up to a nominal diameter of 2000 mm in sections up to 350 m long. The maximum total output of the UV gas discharge lamps is now an impressive 36 kW, generated by a 100 kVA Stage V generator. At maximum output, this generator consumes 55 kg of CO2 per hour using conventional diesel (2.65 kg CO2/liter, full load consumption 20.9 l/h).
Using HVO100, CO2 consumption is reduced to 11 kg CO2 per hour (approximately 80% savings compared to diesel). Added to this is the footprint of the construction site equipment and
stored materials (Figure 5).
LED Light Curing
Curing with LED light sources offers a simple, fast, flexible, lightweight, and efficient, yet significantly limited, technology.
The Bluelight LED system can cure the PAA-GF Liner Polyblue 450 UP to a nominal diameter of DN 600 mm in sections up to 125 m long with a very low total LED light source power of 1.5 kW. A small 6 kVA generator is sufficient for operation. Alternatively, this energy could easily be drawn from a conventional power outlet, taking power from 100% renewable power supply.
At maximum output, a 6-kVA generator consumes approximately 5 kg of CO2 per hour using conventional diesel (2.65 kg CO2/liter, full-load consumption approximately 2 l/h), which can be reduced to 1 kg of CO2 per hour when using HVO100 (approximately 80% savings compared to diesel). The curing technology can be accommodated in vehicle technology weighting less than 3.5 t (Figure 6). The highly efficient LED technology offers users the opportunity to significantly reduce the construction site setup for smaller and medium nominal diameters without compromising on final quality. Bluelight GmbH and affiliated partners demonstrate the process during exhibitions and at demo job sites.
