Concept of a Dish-Stirling-System

Concept

Dish-Stirling systems typically have a capacity of 10 to 50 kW per unit and are best suited for decentralized solar electricity generation. Their parabolic concentrator continuously tracks the sun, reflecting the incoming parallel solar rays onto its focal point. The solar heat exchanger located at the concentrator focal point absorbs the concentrated solar radiation, thus heating the heat transfer medium (helium or hydrogen). A Stirling engine converts this heat into mechanical energy, which in turn is transformed into electricity by an electrical generator directly connected to the engine’s crankshaft.

Dish-Stirling Prototypes – Plataforma Solar at Almería / Spain

During the past few years we have been developing, constructing and testing various 10 to 50 kW unit prototypes.

Country Reference Unit in France

These prototypes have been installed as country reference units in Spain, France, Germany, Italy, and India. After thousands of hours of operation, it can today justly be called a mature technology.

Technology

The major components of a Dish-Stirling-System are the parabolic concentrator, the Stirling motor and the tracking system.

Concentrator – diameter 8.5 m

The concentrator is one of the key elements of a Dish-Stirling System. Our 10 kW system has an 8.5 m concentrator diameter. The concentrator consists of easily shippable sandwich facets made from fibreglass-reinforced plastics. Thin-glass mirrors glued to the surface guarantee a permanent high reflectivity of about 94%.

Stirling Engine V161 with Solar Receiver

The Stirling engine is based on a highly efficient thermodynamic cycle that transforms heat into mechanical energy. These are its most outstanding features:
While the Otto and diesel engines are internal combustion motors, the Stirling engine is based on an external heat source: It converts the heat of the sun into electricity at a working temperature of 650°C and an overall efficiency of 30 – 35%. The SOLO Stirling 161 energy conversion unit has a 10 kWel output.

Tracking of the system during a day

Continuous high-precision computerized solar tracking can be monitored, operated and diagnosed remotely from anywhere over the Internet.

Schlaich Bergermann und Partner have developed the complete system in cooperation with its partners.

Links
DLR: www.dlr.de/tt/institut/abteilungen/solarforschung
SOLO: www.stirling-engine.de
Klein + Stekl: www.klst.com

Costs

levelized electricity costs of Dish-Stirling Systems compared

As with all renewable power generation systems, the initial investment in the Dish-Stirling system is significant, however, operating costs are comparably low, because there is no fuel consumption.
The levelized electricity cost depends on the interest rates and depreciation time, as well as solar radiation at the site. In southern Europe, a levelized electricity cost of 0.20 €/kWh is expected, and at very favourable sites, 0.12 to 0.15 €/kWh or even lower, assuming large-scale series production of the units.

Visualization of a Dish-Stirling Farm

The Dish-Stirling units can be interconnected in a “farm” that can meet a demand of from 10 kW up to several MW. This makes them ideal for remote power supply, and an attractive alternative to today’s widespread use of environmentally damaging diesel engines.