OPERATION OF THE SOLAR

HYBRID GAS TURBINE

SYSTEM AT MW SCALE

Guide:Suraj R By: Rosh Reji

INTRODUCTION

In a solar hybrid gas turbine the pressurized air is directly heated up

Significant cost reduction for solar electric power generation is

achieved

The first hybrid system at megawatt scale was commissioned in may

2012 at Abengoa’s Solucar platform near seville

A hybrid system at KW scale can be found on the European

research project Solgate

In this system solar energy is introduced into Brayton cycle

Solar heat can be directly fed into the gas turbine using a solugasreceiver placed on a tower without the losses in a heat exchanger

The special attractiveness of Solugas project is the successful

integration of solar receiver and gas turbine

Aerial view of Solugas demonstration plant

Technology Overview

Solar hybrid plants are operated in a thermodynamic

open cycle, known as Brayton cycle.

1->2: Fresh air is compressed, where its pressure and

temperature are raised.

2->A: The compressed air is heated in the solar receiver

using concentrated solar energy

A->3: The compressed air is heated in the combustion

chamber using Natural gas.

3->4: The hot air drives the turbine and expands until

atmospheric pressure, turbine drives generator,

producing electricity

4->1: The heat energy of exhaust gases from the turbine

can be recovered with a bottoming steam cycle or a

recuperator

Diagram of Mercury 50TM gas turbine installed in the Solugas

Facility description

Mercury 50 gas turbine is used in this system

High temperature receiver is used

This receiver can heat pressurized air up to 800 °C

It is made out of 170 fine nickel based alloy absorber

tubes

The absorber tubes are exposed to high concentration

of solar radiation, achieving in 5 m of radiated length a

temperature increase of more than 500 K

Several hundred sensors are used to monitor the plant

behaviour

Operation

The first task is to achieve an ideal focus of the heliostat

field on the receiver cavity

Receiver cavity is significantly smaller in aperture than in

other plants, just 2.7 m of diameter for a field of 69 units,

each of them with 121 m2 reflective area.

The cavity shape arrangement of the receiver is to

minimize convectional losses

Heliostats need to be controlled very accurately to avoid

spillage losses and very high concentration of radiation in

particular areas of the receiver

The plant can be fully operative in 30 minutes at a

desired receiver outlet temperature

The gas turbine itself can be started and running at full

load in even less time of approximately 10 minutes

Input data are mainly measured values like DNI-Direct

Normal Irradiance

Irradiance is the power of electro magnetic radiation

per unit area incident on a surface

A 360° dome camera on top of the tower helps to

predict changes on DNI

: Operation under transient periods keep electric output

constant

: Operation under transient periods keep electric output constant

: Operation under transient periods keep electric output

constant

operation under transient period keeps electric output constant

Sudden turbine shut-down and temperature rapid decrease

First day operation at 800 °C as receiver outlet temperature

Stable operation at 700 °C as receiver outlet temperature

Components performance and

modifications

During operation the components have been monitored

in order to obtain maximum information on their

performance and options for improvement

1. heliostats

Heliostats include an innovative tracking system using hydraulic

components for both, azimuth and elevation movement

During operation the heliostats as well as their control system have been

tuned

Its tuned so that the focusing to the aim point at the cavity entrance was

reached more accurately and tracking the sun has become easier, and

smoother

View of heliostat field

2.Receiver

The solar receiver absorber tubes are exposed to high

concentration ratios

Plant operation and control have been improved

even if thermal gradients between the in- and outlet of

the tubes are in the range of 500 K, solar flux distribution

has become more homogeneous on the absorber tubes

This reduces temperature difference between the

different regions of the receiver to a minimum

It also helps to reduce the maximum temperatures in

individual tubes

Still the metallic parts are bearing maximum

temperatures over 850 °C to keep the pressurized air

temperature at 800 °C.

First commercial solar power tower - PS10

Solugas receiver placed on tower

Design view of tubular receiver

3. Receiver insulation

thermal insulation is used to preserve hot temperatures

inside the cylindrical shaped arrangement of the

receiver

It minimizes thermal losses and the shape is optimized to

achieve maximum homogenous temperature

distribution

The insulation material is mainly made by a ceramic fiber

which is directly exposed to solar concentration and

temperatures

Poor insulation improved insulation

4.Gas turbine

The gas turbine Mercury TM 50 is successfully operating in the

different operation modes of the solar plant

Due to the adjustments the turbine is able to work in a wider

range of conditions than in the commercial configuration

It can work in a wide range of meteorological conditions ,

reaching from extremely high ambient temperatures to

colder temperature &from very less to high humidity

The turbine guarantee stable operation and ramp up

behavior under each condition

The turbine’s combustion chamber is prepared to admit

650 °C as maximum inlet temperature

Advantages

The concept of solar-hybrid gas turbine systems leads to the

following advantages:

High cost reduction potential due to the high conversion

efficiency

Low environmental impact due to low water consumption

Reduced land usage due to high conversion efficiency which

reduces collector area and land use

Guaranteed dispatchable power, independent on

meteorological conditions

The plant can be fully operative in 30 minutes at a desired

temperature receiver outlet temperature

conclusion

The solar energy is used to run a gas turbine

The gas turbine is coupled to a 4.6 MW generator

The heat of the exhaust gas from the turbine is used to

run a steam turbine

The steam turbine is coupled to 2 MW generator

The whole system has proven to perform correctly under

nominal and adverse conditions

Future work

Further improvements and modifications on

the operating system are foreseen to be

implemented during the ongoing operation of

the plant

References

Solugas – Operation experience of the first solar hybrid

gas turbine system at MW scale --SolarPACES 2013

Co-located gas turbine/solar thermal hybrid designs for

power production

www.sciencedirect.com

www.solugas.com