A hybrid solar closed-cycle gas turbine combined heat and power plant concept to meet the continuous total energy needs of a small community

Bibliometric analysis of photovoltaic thermal (PV/T) system: From citation mapping to research agenda

Terrestrial Micro Renewable Energy Applications of Space Technology

There is a common interest in the distributed power generation: generally for the combined production of electrical and thermal energy and often, although not necessarily, in association with renew...

Binary liquid metal–organic Rankine cycle for small power distributed high efficiency systems

Solar energy can be economically converted into electrical energy for small and medium power outputs. A typical solar power plant consists of a parabolic dish, cavity receiver and gas turbine. To obtain high gas turbine efficiences, the working fluid used has to be heated to high temperatures. This necessitates the use of expensive high-quality materials for the tubes in the receiver. This expense must be kept to a minimum. The present paper demonstrates how this aim can be achieved by meeting the so-called Bammert Criterion.

Design criterion for tubed solar-heated cavity receivers

Conversion of solar energy into mechanical or electrical energy in small solar power plants (10–500 kW) requires new design criteria, especially with regard to turbomachinary. The cycles suitable for solar power production are affected by many variable such as kinds of working fluid, range of power and maximum cycle temperature determined by the type of collector. Also, the size of the plant will influence the selection of the various components of the plant, especially that of the turbomachinery. A study of a suitable thermodynamic cycle and working fluid is done for different ranges of power and temperature. The working fluids considered are steam, toluene, and refrigerant 113 for the Rankine cycle systems and air for gas turbine systems. For Rankine cycles, turbine selection is a problem in the small power range. This is mainly due to the fact, that for high efficiency the enthalpy drop should be as high as possible, and the mass flow rate of the working fluid through the turbine becomes very small. This, in turn, requires high rotational speed, multistaging and partial admission, especially if water is the working fluid. Toluene offers better design criteria for the turbine in the same temperature and power range (50–200 kW). For the very small range (10 kW) refrigerant 113 or similar should be used, otherwise severe design problems with the turbine will occur. In this power range, photovoltaics may also be considered. For high concentration systems with “Brayton cycles” (800–1000°C) only open-cycle gas turbine plants should be used.

Turbomachinery for small solar power plants

In the tubes of radiation heaters, which are under high thermal loads, apart from stresses caused by the pressure of the working medium also thermal stresses are produced. Owing to the nonuniform irradiation over the tube periphery, these thermal stresses have to be determined taking into account the radial and tangential temperature gradients in the tube wall. It is shown by the example of the pulverized-coal-fired heater of a closed-cycle gas turbine plant to what extent thermal stresses are caused, assuming linearly elastic behaviour of the tube material, and how the method of fixing the tube ends influences the total stress.

Karl Bammert

Papers

Turbomachinery for small solar power plants

The thermal load of tubes in radiation heaters