Roofing Systems to Environment and Sustainability

 

General Overview

Sika has developed solutions which can  help ensure that the roof creates minimal impact on the environment whilst meeting the functional requirements of clients, specifiers, contractors and nature. Roofing membranes/ products are not only manufactured in an ISO 14001:2000  accredited production facility they have a low embodied energy and long life expectancies.

The following important environmental and  sustainability aspects are always taken into account in Sika roofing systems:

• Recycling
• Embodied Energy
• Durability
• Sun light reflectivity

Recycling

Sika has proactively recycled factory waste  back into production since 1960. Wherever  possible, higher quantities of production and  post-consumer membrane are recycled into  new products, such as Roof Protection Sheets and Walkway Pads.  Today walkway pads, manufactured in Europe  since 2000, provide tough, durable solution  for pedestrian access on exposed roofs and at the same time they are produced from almost 100% recycled material. The only non-recycled product being less than 1% carbon black that is added for colour consistency. Sika recyclate is also sourced from existing membrane roofs when they are removed  to enable the client to thermally upgrade the building, a common practice in Western Europe. This process is managed through the company’s involvement with the Roof Collect  scheme operated by Vynyl 2010.

Embodied Energy

Embodied energy is the measurement of the  amount of energy required to produce a tonne or square metre of a product, it can also be used to measure the carbon embodied within a product. Generally the lower the embodied energy and carbon levels, the better a product is for the environment. All Sika roofing membranes have low embodied energy, contributing less to global warming than many alternative roofing technologies.

Sun Reflectivity

The benefits of solar reflective materials and colours are well known and understood in warm climates around the world. With urban density increasing, the “heat island” (Albedo) affect is impacting on cities at an ever-increasing rate. A significant contribution to reducing the  Albedo affect can be made by simply replacing dark roof surfaces with a lighter colour, ideally white – Sika roofing systems include solutions which allow the reflection of  up to 83% of the heat in sunlight.

Ronnen Levinson & Hashem Akbari’s December 2007 report “Potential Energy Savings and Environmental Benefits of Cool Roofs on Commercial Buildings” demonstrated that by changing from a relatively low solar reflectivity light grey membrane, to a higher reflectivity white membrane, large energy cost savings could be made. Therefore significantly reducing emissions of carbon dioxide (CO2), nitrogen dioxide (NO2), sulphur dioxide (SO2) and mercury (Hg).

Durability

Long service life is a key element of sustainability, the longer something lasts the less damage it should do to the environment in use. Sika roofing systems has been tested for aging and life expectancy by different institutes and organizations with outstanding results. As an example the British Board of Agrément (BBA) certifies a standard 1.2mm thick Sarnafil G/S membrane to have a life expectancy “in excess of 35 years”.

Cost effective and favourable technology solutions for high-head Francis Turbines

For high head turbines there is often a choice between Francis and Pelton. The main advantages of Francis turbines are that the dimensions will be smaller and the speed higher. Due to this the cost will be lower, both for the electro-mechanical equipment and for the powerhouse civil works. By further utilizing the most efficient solutions available, the construction of modern high-head Francis turbines give a more easy to use and less maintenance demanding result than previously.

This presented technology has been used in a several of the world’s high-head Francis turbines. It traces its roots back to the 1950s, when already Francis turbines with heads above 400 m were routinely delivered. One example is Holen 3 in Norway with a rated net head of 610 m and a maximum gross head of 660 m. In Asia, it has recently been used in more than a dozen high head Francis turbine projects in China. Recently, it was also being used for the Nam Theun 2 project in the Republic of Laos, which will have 4 of 247 MW Francis turbines at a rated head of 350 m. This paper gives an introduction to several important solutions of the high head Francis turbine design. It includes some of the important design details on runners, guide bearings, shaft seal, shaft couplings, guide vane friction device and the principle of equalized loads utilized on stationary part embedment. Implementation of these design features will have positive impact on construction cost, maintenance program and the general operation of the turbine. Following are descriptions of each design solution with its listed advantages for making the turbine more reliable, stabile and flexible to operate.

Most recent, several  features are being incorporated in the Nam Theun 2, High-head Francis turbines. It uses a X-Blade runner but without splitter vanes, vertical shaft guide bearing with fixed pads, non-contact seal and guide vane friction device. And the bottom cover is together with the draft tube cone not embedded, making them available to be dismantled downwards and sideways with good access for runner inspection and