All-aluminium absorbers: reference installation without corrosion

The reference system with twelve Fino collectors is installed on the facade. (Ph
The reference system with twelve Fino collectors is installed on the facade. (Ph

All-aluminium absorbers are splitting the solar thermal industry down the middle. Some see them as an important way to reduce costs; others just see an additional corrosion hazard.

Solar Technologie International GmbH (STI) is one of the companies in favour of aluminium and has now released the results of just over two years of monitoring a reference installation. STI equipped a four-party multi-family house with a 12 m² solar installation, which uses collectors with all-aluminium absorbers. Criticism of such systems is usually based on the fact that copper or brass filings can easily get into the solar circuit. These can then cause corrosion on the aluminium.

To prevent this, the company relies on a 2 to 2.5 m long safety pipe made of corrosion-resistant stainless steel, which is used for the collector connection. The safety pipe is not a standard product that can be easily replaced. This means that the technician is forced to install it as well.

In addition, all-aluminium absorbers can only be used in completely closed systems, according to René Fiedler, managing director of STI. Such systems also contain a small amount of oxygen when they are first put into operation, but once this has reacted, not much else happens. Of course, it is also important to only use heat transfer fluids that are approved for all-aluminium absorbers. An overview of approved heat transfer fluids available on the market can be found in Sun & Wind Energy edition xy/2013 p. xyz.

Fiedler estimates the cost savings at about 20% when aluminium is used. At this point in the discussion, proponents of copper pipe lattices usually argue that the price of the collectors only makes up a small portion of the price of the entire system. The rather low overall savings are therefore disproportionate to the risk of corrosion. STI is now attempting to invalidate the risk argument with its reference installation.

The installation mainly consists of standard components from partner companies. The solar station and isolating valves are from the company Meibes. The only component with more functionality than one would usually find in installations of this size is the XTDC control unit from Sorel. But even in this case, the rationale for using it has more to do with additional monitoring options than with different control behaviour.

Another company involved in the reference installation project is Tyforop Chemie GmbH, which provides the heat transfer medium. Tyforop has also regularly taken glycol samples for testing.

Everyone seems satisfied with the performance of the reference system. The solar coverage rate is over 45%; only 40% had been calculated. Fiedler is content: "We are now well past the pilot installation phase; the new absorber types have established themselves on the market and with our customers. Sales figures for these collectors are rising steadily. The manufacturers of other necessary system components have also adjusted to the new developments in collectors."

Jan Gesthuizen

Similar Entries

Excelsior Energy Capital (“Excelsior”), a renewable energy infrastructure fund focused on long-term investments in wind and solar power plants in North America, and Unico Solar Investors (“Unico Solar”), a wholly owned subsidiary of Unico Investment Group LLC that develops, owns and operates commercial and community solar installations, announced the completion of a 300-kilowatt solar energy system at Central Station, a new four-story, 125,000-square-foot office building. Developed by SteelWave and owned by Principal Real Estate Investors, the building is located at 285 Sobrante Way in Sunnyvale, California.

Installation with just one click (pict. IBC Solar)

IBC Solar, a leading full-service provider of SOLAR energy solutions, is expanding the proven TopFix 200 pitched roof mounting system with sophisticated components: From the new and height-adjustable G3 Vario outer clamp to the TopFix 200 Fast Click for the convenient installation of micro-inverters and the optimised Mammut Form S+ moulded sheet metal tile. All components are ideally tailored to the overall system and enable even faster and easier installation with maximum flexibility.

This installation will allow the farm in South Africa to lower the purchase of external energy, obtaining up to  80% of energy self-reliance as well as 70% energy self-consumption, that means 712 kWh of electricity produced daily vs. 895 kWh consumed (pict. Fimer)

All Electrical Distributors has chosen FIMER’s PVS-100-TL to help South African dairy farm run on 70% of its own energy.

Sometimes one and one add up to more than the mere addition of numbers. Structural Health Monitoring (SHM) of rotor blades is a complex and demanding task that requires very good hardware as well as professional data analysis in order to be able to make really precise and early statements about structural damage to the rotor blade. For this reason, two specialists have now joined forces to offer wind farm operators the best possible combination of forces on the market.