SOLAR THERMAL STEAM TURBINE SYSTEM

ME 258ADNAN A. BEDRI

PROF. TIMOTHY MARBACH FALL 2012

INTRODUCTION

• A steam turbine is a device that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft.

• Its modern manifestation was invented by Sir Charles Parsons in 1884 whose first model was connected to a dynamo that generated 7.5kw of electricity.

Conti………

• The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency through the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible process.

Conti……

• Steam turbines are made in a variety of sizes ranging from small <0.75 kW (1< hp) units (rare) used as mechanical drives for pumps, compressors and other shaft driven equipment, to 1,500,000 kW (2,000,000 hp) turbines used to generate electricity.

Thermodynamics of steam turbines

Steam Turbine operates on basic principles of thermodynamics using the parts of Rankin cycle.

Superheated vapor enters the turbine, after it having exited the boiler at high T and P.

The high T/P steam is converted into kinetic energy using nozzle.

Conti.. Once the steam has

exited the nozzle it is moving at high velocity and sent to the blades of turbine to create force causing them to move.

A generator or other such device can be placed on the shaft and energy can now be stored or used.

Solar Steam Turbines

• The solar steam generated by these state of the art commercial solar thermal power plants does not exceed 380ºC(553k), which limits the conversion efficiency of the steam turbine connected downstream.

• This performance limitation can be overcome by raising the operability temperature of the receiver and thereby increasing the conversion efficiencies of the thermodynamic cycle:

In point-focusing system, precise solar concentration can be achieved .

Direct Solar Steam generator

• Some solar company like AREVA offers direct solar steam for :

Enhanced oil recovery Petrochemical refining Food processing and

dessalination.

Solar thermal power plant In order to reduce fossil fuel

consumption and carbon dioxide (CO2) emissions, promoting the utilization of renewable energy and improving the efficiency of energy utilization are important.

Solar thermal energy, the most abundant renewable energy source, has been used to generate electric power energy in limited regions where solar radiation energy is abundant.

Conti..

• A steam accumulator is incorporated as a heat storage device to store surplus steam produced during the day when solar radiation is large and to use the steam when solar radiation is low .

Solar steam turbine performance During start-up of the

power plant, it is assumed that the steam generator is first brought to full load with the steam produced being dumped to the condenser via the steam-bypass system

The steam-turbine is then progressively loaded, and the bypass valves closed.

Thermal power and turbine loads for a day with intermittent solar radiation.

Start-up and cool-down time

Turbine Internal Temperature

Medium Scale Solar thermal PP

aperture area- 100,000m^2Steam temperature - 543kVolume of steam accumulator- 4000m^3Minimum steam pressure - 0.98MpaCondenser outlet temperature – 306kTurbine inlet temperature -1573kGenerator operating Temperature – 873k

Conti… Concentration ratio 26 Optical efficiency 77% Adiabatic efficiency of turbine - 87.5% Adiabatic efficiency of compressor – 85% Generator efficiency 98% Annual total horizontal solar radiation energy

1764kwh/m2/yrMaximum net work output 12.4-22.4MWNet generated power 81-149Gwh/yr

References.[1].Economic evaluation of solar thermal hybrid H2O turbine power generation systems Takanobu Kosugi a,

Pyong Sik Pak b a Systems Analysis Group, Research Institute of Innovative Technology for the Earth, 9-2 Kizugawadai , Kizu-cho , Soraku-gun, Kyoto 619-0292 Japan

[2] Annual performance improvement for solar steam turbines throughnmthe use of temperature-maintaining modifications James Spelling a, , Markus Jo¨cker b, Andrew Martin a Department of Energy ⇑Technology, Royal Institute of Technology, SE-100 44 Stockholm, Sweden

b Siemens Industrial Turbomachinery AB, SE-612 83 Finspa˚ ng, Sweden[2] Lior N. Solar energy and the steam rankine cycle for driving and assisting heat pumps in heating and

cooling modes. Energy Conversion 1977;16(3):111–23.[3] Pilkington Solar International. Status report on solar thermal power plants. Cologne: Pilkington Solar

International, 1996.[4] Control concepts for direct steam generation in parabolic troughs Loreto Valenzuela a,*, Eduardo Zarza a, Manuel Berenguel b, Eduardo F. Camacho c a CIEMAT, Plataforma Solar de Almerıa, P.O. Box 22, Tabernas (Almerıa) E 04200,

Spain[5] Birnbaum, J., Eck, M., et al., 2008. A direct steam generation solar power plant with integrated thermal storage. In: Proceedings of the 14th Bienial Solar PACES Symposium. Las

Vegas, USA.[6]Trough integration into power plants—a study on the performance and economy of integrated solar

combined cycle systems