Feasibility Study of a Solar Power Tower in Algerian Sites

Asma Aichouba

Solar Equipements Development Unit UDES, EPST/CDER,

Bou Ismail, W. Tipaza, Algeria asmaichouba@gmail.com

Mustapha Merzouk Fundamental and Applied Physics Laboratory,

Saad Dahlab University, W. Blida, Algeria mus.merzouk@gmail.com

Abstract- A feasibility study on the establishment of a solar power plant of 10 MWe on various Algerian sites, especially adapted to the climatic conditions of Algeria, is presented. The simulation is conducted on an hourly basis considering the system 'field', and the system 'receiver'. The annual average production and average monthly production was estimated for different selected sites. Yields, annual energy production, and the cost per kWh are evaluated. The results are compared for the purpose of site classification.

Keywords - Solar, solar concentrator, solar power concentrations,

thermoelectric plants, solar power towers, feasibility, performance.

I. INTRODUCTION

As a result of the high demand of energy, environmental concerns, and anticipated future scarcity of fossil fuels, solar energy is considered as a good solution to energy and environmental challenges that the world faces. The production of electricity by means of solar thermoelectric conversion exists for over thirty years; the implementation of such plants requires a very strong sunshine and low humidity. They are particularly suited to areas that are in the Sunbelt such as South America, south-west of the United States, most of Africa, the Mediterranean countries, the Middle East, China, Australia and the desert plains of India and Pakistan, [1, 2, 3, 4].

The first concentrating solar power plant was carried out by Francia in the early sixties [5]. The Francia plant produces steam at 500 0 C using concave mirrors focus sunlight on a receiver at the top of a tower. However, due to low energy costs, these works are unheeded until the early 1980s (the second oil crisis).

From this period achievements for research/ development have increased [4, 5, 6, 7] i.e plants of Albuquerque (USA) with a capacity of 5 MW, Nio (Japan) 1 MW capacity [11]

N oureddine Said Centre of development of the renewable energies,

EPST/CDER BouzanSah, W. Algiers, Algeria.

saidnoureddine@cder.dz

Nachida Kasbadji Merzouk Solar Equipements Development Unit

UDES, EPST/CDER, Bou Ismail, W. Tipaza, Algeria

nkmerzouk@gmail.com

Eurelios (Sicily) with a capacity of 1 MW [10], SSPS ( Tabenas, Spain) with a capacity of 2.7 MW [10], SOLAR ONE (USA) with a capacity of 10 MW [7], THEMIS (France) with a capacity of 2.5 MW [13,14] , STEOR (USA) with a capacity of 1 MW [4] and CESA (Spain) with a capacity of 7 MW, [8].

Then nothing happened until in 1999, the date of commissioning of SOLAR TWO with a capacity of 10 MW [9]. Followed by three Spanish plants, SOLAR TRES ( 17 MW in 2007) [7, 9], PI0 (for 10 MW in 2008) [10, 11, 12] and P20 (20 MW in 2009) [15], then the German Central receiver in ruLICH (1.5 MW in 2010) [16, 17]. All these plants used heliostats with rectangular altazimutal tracking.

Since then, under the constraint of international commitments to limit emissions of greenhouse gases and the increase in the cost of energy, most countries have announced major concentrating solar power programs. In March 2011, Algeria announced the launch of a program for the installation of 22 GW by 2030, in which CSP is the main technology.

In this context, the purpose of this work focuses on the feasibility solar tower power plant at different sites in Algeria. Given the large differences between the Algerian climates we considered a site for each area, namely:

Algiers, for the north ; Bechar for the desert Tamanrasset, for the extreme south.

II. DESCRIPTION OF THE PLANT

The solar power plant chosen for this study is a central tower of 10 MWe using molten salt. It's quite similar technically to the U.S. SOLARTWO installed in Daggett in the Mojave Desert in California.

SOLAR TWO is a solar power tower; the result of the renovation of 'SOLAR ONE' operational from 1996 until 1999, the field was equipped with 1926 heliostats with a total area of 82.750 m2•

978-1-4673-6374-7/13/$31.00 ©2013 IEEE

Solar Two used molten salt, a combination of 60% sodium nitrate and 40% potassium nitrate, as an energy storage medium instead of oil or water as with Solar One. This helped in energy storage during brief interruptions in sunlight due to clouds. The molten salt also allowed the energy to be stored in large tanks for future use such as night time and ensured the continued operation of the turbine. The molten salt was able to keep hotter longer than the system used in Solar One, [6, 9]. Characteristics of the simulation plant are given in Table I.

TABLE I CHARACTERISTICS OF THE SIMULATED CENTRAL.

Heliostat area m' 39.1

Heliostats field Reflectance and soiling % 0.90 Image error rad 0.002

Tower Height Min : 30

m Max : 100

Coolant Molten salt % 60%NaOl 40% KN03

Receiver height m 5.33 External receiver Receiver diameter m 3.33

Number of panels / 24 Efficiency of the block % 42,5

Power block Inlet temperature °C 574 Outlet Temperature °C 290

III. METHODOLOGY AND ASSUMPTIONS

Performance simulation was performed using SAM 'Advistor System Model' (a model that performs the analysis of cost and performance). It has been designed to facilitate decision-making for those involved in the renewable energy industry.

However, before starting the simulation one has to input the plant conditions and meteorological data for each site. Adaptation which introduced changes the number of heliostats, the height of the tower and other characteristics of the plant. The data required for the simulation are shown in Table II.

TABLE 11 REQUIRED DATA FOR THE SIMULATION

Results of the Algiers Bechar Tamanrasset simulation

Number of heliostats 1573 1582 1582 Tower height m 53.33 45. 56 45. 56 Receiver height m 5.33 3.85 4.89 Receiver Diameter m 3.33 3.33 3.67 Reflective surface m' 61642.7 61995.4 61995.4 Altitude m 25 -- 1454

Latitude/ Longitude 36°72 / 31 °37 / 22°78 / 5 °52

3°25 2°13 Time lag h GMT+l GMT+l GMT+I

A. Assumption

1) Thermal analysis: Using SAM, we identify the different characteristics of the systems 'field of heliostats' and 'receiver' by using weather measured data on site or reconstructed from measured data. From these weather data, the software evaluates on an hourly basis the flow of energy reflected by the heliostat field (power incident to the receiver), the flow of

energy delivered to the power bloc (power output of the receiver), the optical efficiency, thermal efficiency, and the overall average yield for each site will also be determined.

2) Economical analysis: The economical analysis will allow us to estimate the levelized cost of electricity for each site. Costs used in the economical analysis are shown in Table III.

TABLE III BASIC DATA FOR ECONOMICAL STUDY.

Cost of land 1,400 DAlm2 Heliostat field cost 14,070 DAI m2 Power block 40,250 DA/kWe Total cost of the tower 128,364,000 DA Total cost of the receiver 51,020,000 DA Total cost of the plant 3,153,211,000 DA

B. Updated Cost of Electricity

The levelised cost of electricity, 'LEC', is the main indicator for the economical analysis of solar concentrating systems, the general equation for calculating the LEC is defined by:

Where:

LEe = CAinvs+CAO&M-CACOz

Enet (1)

CAinvs: Present value of the annual costs of investment.

CAO&M: Present value of the annual costs of operation and maintenance.

CAcm: Present value of the annual appropriations of emission reductionC02

Enet : Annual electrical energy production. The present value of annual cost for operation and

maintenance is given by:

CAO&M = 0.02 * CAinves (2)

IV. RESULTS AND DISCUSSION

A. Result of Thermal Analysis

The solar direct normal irradiance, the incident power to the receiver and the power output of the receiver are represented for the three sites considered in Figures 1, 2 and 3 respectively for Algiers, Bechar and Tamanrasset. The site Daggett was taken as a reference site for comparative studies.

600 ,-----------------r 20

1 = = � :��H J�i �ii§R�O) 1 3 5 7 9 11 13 15 17 19 21 23

lst "hours"

-annual DN! nW/m2n

-annual p.t.r "MW"

-annual p.f.r "MW"

Figure I. Direct average annual normal radiation; power to receiver; power from the receiver; for the site Algiers.

-annual DNI "W/ml"

-annualp.t.r"MW"

-annual p.f.r "MW" 1 3 5 7 9 11 13 15 17 19 21 23

1st "hours"

Figure 2. Direct average annual normal radiation; power to receiver; power from the receiver; for the Site Bechar.

Power to the receiver, power from the receiver, the receiver outputs and extreme power in production are shown

in Table IV.

-annual DNI "W/ml"

-annualp.t.r"MW"

-annuall).f·r"MW" 1 3 5 7 9 11 13 15 17 19 21 23

Tst "hours"

Figure 3. Direct average annual normal radiation; power to receiver; power from the receiver; for the site Tamanrasset.

Similarly, optical and thermal efficiencies (maximum and minimum) expected are shown in Table V for the three sites. The average annual total returns are shown in Table VI

TABLE IV POWER To THE RECEIVER AND POWER FROM THE RECEIVER FOR THE 3 SITES

MWh per day Power to receiver Power from receiver

Algiers July November July November

215.4 39.189 186. 5 32.84

Bechar March December March December 224.4 139 198.8 123.5

Tamanrasset June September June September 222.7 157.4 195.25 137.59

T ABLE V MAXIMUM AND MINIMUM AVERAGE EFFICIENCIES

Average optical efficiency Average thermal efficiency

Maximum efficiency Minimum efficiency Maximum efficiency Minimum efficiency

Algiers July November 38% 29%

Bechar March December

42% 36%

Tamanrasset .I un September 43% 34%

TABLE VI TOTAL EFFICIENCY

Maximum total Minimum total

efficiency efficiency

Algiers 15 % 4 % Bechar 15.4 % 11 %

Tamanrasset 17. 5 % 12.4 %

The analysis results can be deduced, in comparison with published data, the expected performances are correct.

In addition, we can see that the performance remains almost constant throughout the year in Tamanrasset and Bechar to a lesser degree.

B. Results of Economical Analysis

The results of the financial analysis are shown in Figures 4, 5 and 6. Figure 4 shows the Average annual solar irradiation estimated for the 3 sites. Figures 5 and 6; show respectively, the annual energy produced by the plant in each sites and the levelized electricity cost for the 4 sites, Tamanrasset, Daggett,

July November 84% 83%

March December 88,5% 88%

.I un September 88% 87%

Bechar and Algiers. The results allow us to see the average discounted cost is

similar for Tamanrasset, Bechar and the U.S. site of Daggett. As expected Tamanrasset is the best site.

3000 �------------------

2500

2000

1500

1000

500

Daggett Tamanrasset Bechar

Ii IRDA kWh!m'.year

Algiers

Figure 4. Average annual direct irradiation for the 4 sites.

25

20

15

10

tamanrasset Daggett Bechar

II E.a GW/yeor

Figure 5. Annual energy produced by the plant in each sites.

30

25

20

15

10

Tamanrasset

Figure 6.

Daggett Bechar Algiers

Ii l.E.C DA/kWh

Levelized electricity cost for the 4 sites.

V. CONCLUSION

Using the methodological conditions of the sites considered, the behavior of the solar SOLAR TWO type power plant was simulated in sites of Algiers, Bechar and Tamanrasset.

Energy production and discounted costs were estimated for the three sites and the Daggett as a reference site.

The results show that southern Algeria is very interesting with production levels and costs comparable to those of the reference site.

We must also underline the exceptional results for Tamanrasset.

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