A new solar district heating plant in Geneva, Switzerland, is basking in the limelight of Swiss politics, with environmental minister Simonetta Sommaruga personally attending the start-up of the system at the end of February 2021. The 816 m2 solar field consists of special high-vacuum flat panels supplying heat to Geneva’s district heating network at a temperature of 85 °C, even in winter.

The installation helps meet the objectives of Geneva canton’s Energy Master Plan 2020-2030, approved in early December 2020. The SDH system (operated by the SIG utility) was designed by Geneva-based TVP Solar to deliver 516 MWh a year, which corresponds to a specific annual yield of 632 kWh/m2. This is significantly higher than the typical Danish SDH plants which produce between 321 kWh/m2 to 500 kWh/m2 per year, the average being 409 kWh/m2, according to one IEA SHC publication.

The plant is one of several innovative clean energy systems SIG has implemented in the last years. The solar field, which was mounted onto a roof at SIG headquarters in Vernier’s Le Lignon district in Geneva canton, is equipped with 80 performance-tracking sensors.

A press release put the demonstration project’s budget at CHF 2 million, of which CHF 800,000 was spent on the solar field. “Including the CAPEX of the solar field, you get to a heat price of about 70 CHF/MWh over 20 years. That’s a very competitive proposition for zero-carbon heat in Switzerland. Across Geneva, clean biofuel energy costs 100 CHF/MWh,” noted Guglielmo Cioni, Vice President of Business Development at TVP Solar.

The distinctive characteristic of this particular SDH plant is its high output in wintertime. To reduce energy losses, especially during cold winter days, the absorbers are located inside an evacuated casing. “Another advantage of high vacuum insulation is that it takes very little time to ramp up the temperature in the morning. The solar field reaches the required 85 °C in just a few minutes, even if it is partially covered in snow,” Cioni said about his company’s experience of operating the plant during the first weeks after start-up.

TVP’s most important panel-related patent describes a new method for joining glass plates and metal frames to ensure a high enough vacuum inside the collectors. Thanks to the small size of the contact areas between the internal absorber and the metal frame, heat losses are reduced to a minimum, but enough heat is transferred to the casing for the snow to start melting.

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Source and full article: www.solarthermalworld.org
Image: SIG