Suren Geruni

Radiophysics Research Institute,

49/4, Komitas Av., Yerevan, 375051, Armenia
Tel/Fax: (374 1) 23 46 31, iri@sci. am

Introduction. This paper presents two different approaches in the field of design of a small-scale Solar Power Station (SPS) for individual users. Produced output electric power can make up to 1 kW for one module. The given SPS will be made with an automatic Sun tracking system, quickly deployable and can be made as a mobile variant. The SPS structure is based on an offset type parabolic-cylindrical mirror concentrator and with a new thermo converter in its focal zone. The first converter is based on thermo-mechanical engine/actuator, the structure of which will be made with the use of special materials having Shape Memory Effect (SME).

And the second type is based on thermoelectric converter.

THERMO-MECHANICAL APPROACH

SPS will operate on the base of a cylindrical-parabolic rotary concentrator in the focal zone of which a thermal engine of a new type will be placed using "intellectual” materials — alloys with Shape Memory Effect (SME).

In technical solutions alloys based on Titanium and Nickel, known as Nitinol, are able to recover their specified original shape when heated [1]. This phenomenon is called Shape Memory Effect, and alloys having this Effect are called Shape Memory Alloys (SMA). One of SMA’s remarkable features is that mechanical work can be extracted even at a small temperature difference. For example, Ti-Ni alloy has a hysteresis loop width of 12^50°C in the temperature transformations range of -50°^100°C. Cu-Al-Ni alloy has hysteresis loop width of 15^20°C in the temperature transformations range of 120°^200°C. For the both alloys maximum strength generated reaches 400 MPa. That is, SMAs are suitable for the creation of actuators and devices capable of developing high forces and moments. Force elements may be made in the shape of springs, plates and rods operating in compression or tension. Here, the value of tensile or compressive deformation may achieve 10% and of the bending angle — 180°.

Thermal actuator based on SMA, the design project of which is developed, will work at the expense of heating with concentrated thermal energy of the Sun.

Thermal actuator will drive the rotor of an electric generator. The efficiency would presumably be 10% in the case of cascade performance of the thermo actuators.

It is expected to solve the problem of choosing and testing an alloy with special characteristics meeting specified power parameters of electric generator. Also it will be necessary to construct a mechanism of converting linear movement into rotational one with low friction loss.

Block-diagram of SPS (Fig.1) includes solar concentrator, thermal actuator with elements of SME alloys, mechanical converter, standard electric generator with its shaft rotation velocity of 1500 rev./min. and an output power of about 1 kW (220V, 50Hz) as well as the Sun tracking system, and the system of generator frequency stabilization and accumulators with voltage changers. The calculated concentrator surface area is 12 m2.

1. Solar Concentrator. 2. Thermal Engine of SME alloys. 3. Mechanical Converter 4. Electric Generator. 5. Unit of Generator Frequency Stabilization. 6. Casing of SME Thermal Actuators. 7. Cooler. 8. Sun Sensor. 9. Automatic Control Unit. 10. Electric Drives of Tracking. 11. Distribution Box/Controller. 12. AC & DC Inverters.

13. Accumulators. 14. User. 15. Common Electricity Supply Network.