Keywords

3.1 Introduction

It is universally acknowledged that two of the key technological and economic challenges of the 21st century are energy and environment [1]. Consequently, considerable efforts are being made to effect a gradual transition from systems based on fossil fuels to those based on renewable energy (RE). Electricity generation from solar energy is currently one of the main research areas in the field of renewable energy. In the case of Algeria; the newly adopted version of the National Renewable Energy Program offers the country the possibility to integrate 27% of renewable energy in the national energy mix. Preservation of fossil re-sources; diversification of electricity production and contribution to sustainable development are among challenges that face the country nowadays [2]. It is recognized that solar-thermal energy can play a useful role in generating electrical power despite concerns regarding cost as the thermal source is accessible and ubiquitous [3]. The use of linear Fresnel solar power plant for electricity production, or heat supply is one of the most attractive solutions for developing countries with high sunshine because of the accessible level of technology involved [4].

In this study, our main purpose is to describe Fresnel concentrator solar plant characteristics, through defining its different performances, so that influence of changing location and climatic conditions can be seen on plant cost-effectiveness and productivity for each location i.e. Hassi R’mel, Beni-Abbes, El Oued, and Tamanrasset for Central, West, East and South of Algeria respectively.

3.2 Plant Description

The solar power plant chosen for this study is a 5 MW electric Fresnel concentrator plant which is technically similar to the German Novatec solar plant set up in Calasparra site in Spain (same make and model) (Fig. 3.1).

Fig. 3.1
figure 1

Power plant layout

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The design parameters of the power plant are shown in Table 3.1 (Novatec solar) [5].

Table 3.1 Power plant characteristics
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3.3 Specification

In this section, we have drawn up a specification in which plant characteristics, namely Direct Normal Irradiance (DNI), solar field surface, block number, have been defined (it should be noted that a block contains reflecting mirrors, absorber tube, and steam separator). We have also defined the block surface, block panels’ number, absorber surface, and finally thermal power losses in the absorber.

  • A. Sizing calculation

The generator output power is equal to: Pg = 5 MWelectric.

In order to supply a small city of 5000 inhabitants, whose daily consumption is 5 kWh per family of electricity, each family is composed of 5 persons.

  • B. Distribution of powers per activity

Polyclinic = 0.2 MW, factory = 1 MW, Administration = 0.5 MW, other = 0.3 MW. The sum is 2 MW, so it remains 3 MW for inhabitants: this is the peak power needed by these places.

Therefore, inhabitants number = 1000 houses, or: x = 1000 * 5 = 5000 people

So, the consumption of the city is 5 MWe, it is distributed as follows:

  • Polyclinic = 0.2 MW

  • Factory = 1 MW

  • Administration = 0.5 MW

  • Inhabitants = 3 MW

  • Others = 0.3 MW

The solar multiple is taken as equal to 1.6 which corresponds to 1.5 h of storage.

The selected locations are:

  • West → Beni-Abbes

  • Center → Hassi R’Mel

  • East → El Oued

  • South → Tamanrasset

Table 3.2 represents site meteorological data.

Table 3.2 Site meteorological data [6]
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  • C. Calculation of plant characteristics

  • DNIavg calculation (direct normal irradiance)

$${\text{DNI}}_{{{\text{avg}}}} = \frac{{{\text{DNI}}_{{{\text{annual}}}} {\mkern 1mu} }}{{{\text{ Insolation period }}}} = \frac{{2236}}{{3200}} = 0.698\;{\text{kW/m}}^{2} \times 10^{3}$$

= 698.7 W/m2 for Beni-Abbes and the same calculation is done for the other locations.

  • Calculation of power

$$\left. \begin{aligned} {\text{Generator}}\,{\text{efficiency = 9}} . 5 {\text{\% }} \hfill \\ {\text{Turbine efficience = 38\% }} \hfill \\ {\text{Parasitics efficiency = 98\% }} \hfill \\ \end{aligned} \right\}{\text{we}}\,{\text{will}}\,{\text{obtain}}$$
$$\eta_{\text{bloc}} = 0.95*0.38*0.98 = 0.35 = 35\%$$
$$p_{1} = \frac{{p_{\text{g}} }}{{\eta_{\text{bloc}} }} = \frac{5}{0.35} = 14.28\;{\text{MW}}_{\text{thermal}}$$

P = P1 + P2 = SM * P1, with SM is the solar multiple = 1.6

P = 1.6 * 14.28 = 22.84 MWthermal

So: P2 = 22.84 − 14.28 = 8.56 MWthermal

All efficiencies and powers are shown in Table 3.3.

Table 3.3 Efficiencies and power [5]
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  • Calculation of field surface for each location

If receiver efficiency = 85% we will obtain: Optical efficiency = 45%

So, global efficiency is obtained:

$$\eta_{\text{global}} = 0.85*0.45 = 0.38 = {\mathbf{38}}\%$$

\(\eta_{\text{global}} = \frac{p}{{A*{\text{DNI}}}} \Rightarrow A = \frac{P}{{n_{g} *{\text{DNI}}}} = \frac{{22.84 \times 10^{3} }}{0.38*0.698} = 86,000\;{\text{m}}^{2}\)

For Beni-Abbes, and the same calculation is done for the other locations.

“A” represents field surface.

  • Calculation of block number and surface of each block

The size of (Novatec) plant solar field is S = 21,571 m2

This plant contains 2 blocks, each block has a power of 0.7 MW electric

\(\frac{A}{S} = \frac{{86{,}000}}{{21{,}571}} = 3.98\) is the number of block for a power of 0.7 MW electric

\(3.98*2 = 8\,{\text{blocks}}\) is the number of block for a power of 1.4 MW electric

“A” is the block surface.

The surface of a block is given by:

\(A = \frac{{86{,}000}}{8} = 10{,}750\,{\text{m}}^{2}\) for Beni-Abbes and the same calculation is done for the other locations.

  • Calculation of actual absorber surface

Absorber unit surface is: L * D

L represents unit length = 44.8 m, D represents receiver diameter = 0.6 m

Aabs; unit = 44.8 * 0.6 = 26.88 m2

Each block contains a unit whose surface is 513.6 m2

$${\text{Unit Number}} = \frac{\text{Block surface}}{\text{Unit surface}}$$
$$\frac{{10,750}}{{513.6}} = 21\,{\text{units}}$$

 

So: Aabs actual = Number of units multiplied by unit absorber surface.

= 21 * 26.88 = 564.48 m2 is the absorber surface in a 0.7 MW block.

Total surface of absorbers is calculated by multiplying the result of block number by the actual absorber surface.

STotal = 8 * 564.48 = 4515.8 m2 for Beni-Abbes and the same calculation is done for the other locations.

  • Calculation of lost power

Ploss = UL * Aabs actual * ΔT

We have: Tin = 140 °C, Toutput = 270 °C, UL = 5 W/m2 °C

Ploss = 5 * 4515.8 * 130 = 2.93 * 106 W for Beni-Abbes and the same calculation is done for the other locations. Final results are shown in Table 3.4

Table 3.4 Plant characteristics in each site
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3.4 Results Analysis

As a comparison, we want to check the results found in the first part, then validate them through drawing up specifications in which different plant performances are defined, while using a global calculation method. These performances have been calculated, through using a DNI calculated on the basis of annual normal irradiation ratio to sunshine hours. We propose to verify hereafter these results with those found by SAM simulation software [7]. Simulation of energy performance is carried out in another study using a SAM simulation software, as well as the techno-economic study [8]. A comparative study is made while taking a representative day of the year (21st June, the longest/hottest), we took the DNI values, and then recalculate the power output to adjust the results for each site.

The results are shown in Table 3.5.

Table 3.5 Comparative study
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M1 shown in the table depicts the first calculation method (the global method set forth in the specifications). According, this comparative study aiming at the verification of the results obtained in the global method with those calculated by SAM simulation software, we notice that the output power varies from 4.74 to 5.43 MW, so we can see that there is a slight difference between powers calculated by both methods, and according to the calculations show a difference of less than 8%. The results found by the global method used for the cases studied here are quite satisfactory.

3.5 Conclusion

The study we carried out on Linear Fresnel Concentrator Solar Power Plant allowed us to understand the operating system of this type of plant, as well as the parameters affecting its operation and performances. We have also noticed that the blocking and shadowing effects between mirrors and the cosine effect represent a great obstacle for the power plant cost-effectiveness and productivity. According to this study, we were able to notice the importance of a good choice of the power plant site, as each site is characterized by its direct radiation, ambient temperature, sunshine hours, wind speed, latitude, height above sea level, and other factors which play a key role in the power plant cost-effectiveness and productivity. This is clearly shown in the results obtained according to which the plant different parameters and characteristics vary when it is shifted in different sites.

According to the results obtained for the plant different characteristics in the 4 sites, we can see that Algeria has great opportunities to choose this kind technology i.e. linear Fresnel concentrator solar power plant.

Finally, we can conclude that, among the above-mentioned sites, the most suitable on performance basis is Tamanrasset followed by Beni-Abbes, then El Oued, and finally Hassi R’mel.