, always paying attention to interesting stuff, shared this article by . I have long been fascinated by this cool design with it's world record solar power efficiency record. When others talk about efficiency it's usually figures from the labs or controlled environments. In the real world, this system is already at 32-34% true solar-to-grid electricity conversion, generating 0.5 MW/ha. That's pretty cool. And it's kinda steampunkish too.
What, wait, Ripasso who?
Ripasso Energy is a Swedish company located in Gothenburg. The company was founded by Gunnar Larsson, former CEO of Kockums, merited submarine manufacturer in Malmö. To those who know anything about submarines, the connection to fuel-free energy is pretty clear - the Sterling engine.
The Stirling engine
Invented and patented by Robert Stirling in 1816, the Stirling engine was a simple yet ingenious heat engine that still fascinates us and finds it's uses today. The engine is powered by heat, or rather a temperature difference. Just like steam engines the Stirling engine is sometimes referred to as an external combustion engine, in contrast to the ICE, the internal combustion engine. For about a century the Stirling engine made duty primarily as a domestic engine, but was finally replaced by electric engines as countries were electrified.
How the system works
The Ripasso design, the Ripasso CSP, consists of one or more reflecting dishes, each 12 m in diameter with a total area of 104 m2. The system automatically tracks the sun and concentrate all that sunlight at a tiny 10 cm2 (1.55 square inches) spot on the Stirling power converter, the Ripasso SPC, which generates the electricity and feeds it onto the grid. While the overall design is all very well made, Ripasso are not the only ones that have tried this. So, what's so special about Ripasso's solution?
What Ripasso did that was so clever
Now, while a Stirling engine is rather simple in its basic design, operating one efficiently can be rather complex and difficult. There are different design variations and there is pressure, various types of gas, heat exchangers, control systems and a lot more to consider. The biggest catch is, in order to generate electric power, you either need a gear box or you have to lock the engine to a fixed speed, else the generator will not match the grid frequency. Either way you reduce efficiency, but this is where Ripasso excel with a clever solution. They have thoroughly optimized the engine and generator to work perfectly together, and for optimal efficiency they run the power converter on it's own, optimal frequency, feeding the grid through an inverter. This is key to their world record solar power efficiency record.
Will they make it?
As fascinating as technology gets, the interesting question is, can Ripasso make it "big" with their Ripasso CSP system? Ripasso claim their CSP is competitive and have "negligible degradation and 25+ years system lifetime" with "long service intervals" - and they have four years of operation at the pilot plant in South Africa to back it up. It's not like Ripasso are running short of competition, but they do have a product with an edge, and there ought to be a not too small niche for them. After four successful years, the time has come to scale up.
Dish: 12 m (39.4 feet) diameter, reflecting area 104 m2 (1,120 square feet), 95% spectral reflectivity, ~100 kW with 1 kW/m2 and 0.1 mrad tracking accuracy
Power converter: 30kWe @ 2300 rpm, >40% engine efficiency, 200 bar max engine gas pressure, 720°C max sun receiver/heater temperature
Although I work at Consat, a company that deliver solutions for the Ripasso CSP, I have not been personally involved this project.
#ripasso #solarpower #renewableenergy #engineering #csp