Public Defence of Master’s dissertation by P.J. Yekoladio€¦ · Conclusions & Recommendations With respect to T geo: Optimal operating conditions to increase almost linearly

P u b l i c D e f e n c e o f M a s t e r ’ s d i s s e r t a t i o n

b y

P . J . Y e k o l a d i o

S u p e r v i s o r s : P r o f T . B e l l o - O c h e n d eP r o f J . P . M e y e r

D e p a r t m e n t o f M e c h a n i c a l &A e r o n a u t i c a l E n g i n e e r i n gU n i v e r s i t y o f P r e t o r i a

THERMODYNAMIC OPTIMIZATION OF SUSTAINABLE ENERGY SYSTEM:

APPLICATION TO THE OPTIMAL DESIGN OF HEAT EXCHANGERS FOR

GEOTHERMAL POWER SYSTEMS

www.me.up.ac.za

Content

www.me.up.ac.za

Introduction

Research Methodology

Optimal geometry of coaxial HE

Thermodynamic performance of organic fluids

Optimized solution

Conclusions & Recommendations

Performance analysis of ORC

Introduction

Geothermal energy, an alternative energy source for electric power generation: Economic competitiveness Operational reliability Environmentally friendly nature

www.me.up.ac.za

Energy conversion systems

Drilling techniques

Reservoir stimulation

Resource exploration and extraction

Part1:Optimal geometry of

coaxial HE

Part 2:Thermodynamic

optimization of ORC

Current Research Activities

This Research

Thesis

Content

www.me.up.ac.za

Introduction




Optimized solution



Research methodology

www.me.up.ac.za

Sensitivity analysis

Energy & Exergy

analysisEntropy

Generation Minimization

analysis

Performance analysis

Irreversibility (or exergy loss)

analysis

Optimization model

Heat transfer & fluid flow

analysis

ScopeModel

validation

Research methodology

Flow chart of the simulation procedure

Optimization tool:Optimization tool:Engineering Equation Solver (EES)

www.me.up.ac.za

Content

www.me.up.ac.za

Introduction




Optimized solution




www.me.up.ac.za

Operating variables:11.

2.

3.

3

Variables to be optimized:

5.

4.

2 5

4


Objective functions: Heat transfer and fluid flow analysis

www.me.up.ac.za


Objective functions: Entropy Generation Minimization (EGM) analysis

www.me.up.ac.za


Optimized functions:

Optimal diameter ratio

www.me.up.ac.za

Pressure loss at lower extremity of well to be neglected for


Optimized functions:

Optimal geothermal mass flow rate

www.me.up.ac.za

Where

Where


Optimal geothermal mass flow rate

www.me.up.ac.za

(a) Variation in temperature gradient (b) Variation in geothermal resource temperature


Outer diameter of the heat exchanger

www.me.up.ac.za

(a) Variation in temperature gradient (b) Variation in geothermal resource temperature


Maximum First- and Second-law efficiency

www.me.up.ac.za

(a) Maximum First-law efficiency (b) Maximum Second-law efficiency

Content

www.me.up.ac.za

Introduction




Optimized solution



Organic binary fluids:

Dry: Isobutane & n-pentane

Wet: R152a

Isentropic: R123

www.me.up.ac.za



Effect of organic binary fluid’s properties on the ORC operating conditions

www.me.up.ac.za

(a) Effect of fluid’s boiling point temperature

(b) Effect of fluid’s vapour specific heat capacity

Content

www.me.up.ac.za

Introduction




Optimized solution




Organic Rakine Cycles (ORC)1. The Simple ORC

www.me.up.ac.za


2. The ORC with an internal heat exchanger (IHE)

www.me.up.ac.za


3. The ORC with an open feed organic heater (OFOH) or the “Regenerative ORC”

www.me.up.ac.za


4. The ORC with an OFOH & IHE or the “Regenerative ORC with an IHE”

www.me.up.ac.za


Energy analysis with respect to To: First-law efficiency

www.me.up.ac.za

(a) Tgeo = 110oC (b) Tgeo = 160oC


Exergy analysis with respect to To: Second-law efficiency

www.me.up.ac.za



Energy & Exergy analysis with respect to xin: First- & Second-law efficiency

www.me.up.ac.za



Performance analysis of the ORCs: Cycle net power output

www.me.up.ac.za



Irreversibility analysis of the ORCs: Overall plant exergy loss

www.me.up.ac.za



Sensitivity analysis of the ORCs: Variation with TE , TC & Tgeo

www.me.up.ac.za

Content

www.me.up.ac.za

Introduction




Optimized solution



Optimized solution

Optimal operating conditions

www.me.up.ac.za

(a) Optimal turbine Tin (b) Utilization ratio

Optimized solution

Energy and Exergy analysis with respect to To

www.me.up.ac.za

(a) Optimal first-law efficiency

(b) Optimal second-law efficiency

Optimized solution

Energy and Exergy analysis with respect to xin

www.me.up.ac.za

(a) First-law efficiency (b) Second-law efficiency

Optimized solution

Performance & Irreversibility analyses

www.me.up.ac.za

(a) Minimum overall plant irreversibility

(b) Maximum cycle power output

Content

www.me.up.ac.za

Introduction




Optimized solution




With respect to Tgeo: Optimal operating conditions to increase almost linearly. Maximum cycle power output to increase exponentially.

With respect to the organic binary fluids: Organic fluids with higher Tbp to be preferred for the basic type of ORCs;

e.g.: n-pentane. Organic fluids with lower Cpv more suitable for the regenerative ORCs;

e.g.: isobutane.

With respect to the ORCs configurations: Basic types of ORC to yield maximum cycle power output. The addition of an IHE and/or OFOH to improve significantly the

effectiveness of the conversion of the available geothermal energy into useful work.

Regenerative ORC to be preferred for high-grade geothermal heat. Regenerative ORC with an IHE to yield maximum thermal efficiency.

www.me.up.ac.za

www.me.up.ac.za

The end

Documents

Public Defence of Master’s dissertation by P.J. Yekoladio€¦ · Conclusions & Recommendations With respect to T geo: Optimal operating conditions to increase almost linearly