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Article

Direct Steam Production in Focus: Solar Energy Stations

1,

2,

Noor Al-Bandar *

and Ahmed Hamza Osman

1

Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment,

Universiti Kebangsaan Malaysia, UKM, Bangi 43600, Selangor, Malaysia; p117813@siswa.ukm.edu.my

Department of Information Systems, Faculty of Computing and Information Technology in Rabigh, King Ab-

dulaziz University, 21911, Saudi Arabia; ahoahmad@kau.edu.sa

2

*

Correspondence: p117813@siswa.ukm.edu.my

Abstract: A modeling method was created to forecast the efficiency of a focusing solar energy facil-

ity using direct steam production (DSP) method. We developed a comprehensive DSP solar field

model for parabolic troughs (PTC) and linear Fourier collector in MATLAB. The predictions of the

model had been assessed against operational information from the first precommercial 10 MW DSP

solar power station, intended for a government initiative. The station efficiency was examined in

dual ways: “fixed” and “sliding” steam turbine intake flow.

Keywords: Focused solar energy; Straight Combustion Production; Capacity analysis; Modeling

1. Introduction

Results from government-funded studies indicate that DSP is a compelling technical

alternative for focusing solar power generation [1 ]. Utilizing water and steam for both the

solar field and the power block has various advantages over the existing CSP method that

use parabolic trough collectors with synthetic oil as the heat transfer fluid. The steam heat

threshold of around 399°C for contemporary artificial oils can be surpassed. An efficient

temperature of 450°C appears to be viable for next-generation receiving containers, hence

enhancing the potential for overall efficacy.

In addition, the elimination of oil and water radiators is feasible if water is immedi-

ately drained and heated in the solar field [2 ], leading to a more straightforward plant

architecture and reduced capital expenditures. The utilization of demineralized water is

considered environmentally benign: in contrast to oil, water is more economical, environ-

mentally friendly, and non-flammable.

In comparison to liquid salt, water is both more economical and less caustic. Among

DSP that related interest issues, the adhering to essential challenges are the the majority

pertinent [3-5 ]:

Citation: Al-Bandar, N. and Os-

man, A. H., Direct Steam Production

in Focus: Solar Energy Stations. 2026.

4. p. 2-8

Academic Editor: Asst. Prof. Wurod

Qasim Mohamed

Firstly, the equilibrium of the circular liquid within each tube is essential to enable

interior chilling of the exterior walls, hence eliminating areas of heat. The skeletal strength

of absorbers tubes and the links between enthusiasts and absorption tubes at extreme

pressure and high temperatures. Subsequently, implement station management systems,

especially during transitional phases of irradiation. Ultimately, connection with storage

facilities tailored to the unique properties of the dual-phase fluid water and steam occurs

in the evaporating portion, while the initial heating and overheating components can be

managed by traditional two tank hot salt storage methods.

The expertise and knowledge gained from the work were utilized in the Iraqi gov-

ernment's initiative to develop the inaugural precommercial DSP station. The system con-

sists of a parabolic trough solar sector linked to a heated steam The actress cycle operating

at 399°C and 70 bar, with a nominal output of electricity of 10 MW. This research proposes

the use of modeling for modeling a DSG plant that generates steam from superheated air.

Received: 5/1/2026

Revised: 10/2/2026

Accepted: 8/3/2026

Published: 12/3/2026

Submitted for possible open access

publication under the terms and

conditions of the Creative Commons

Attribution (CC BY) license

(https://creativecommons.org/license

s/by/4.0/).

https://doi.org/10.62909/ejeee.2026.001

Edison Journal for Electrical and Electronics Engineering

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The data collected from the government program has been utilized as a guide because to

the scarcity of details on current DSP deployments. Attention has been directed on pro-

ducing electricity via the steam turbine, with variations in inlet pressure management

over a 24-month duration.

2. Materials and Methods

2.1 Installation of DSP Station

Figure 1 illustrates the configuration utilized in the current investigation. This per-

tains to the government DSP solar energy station with an authorized capacity of 10 MW,

for which conceptual viability was evaluated in [6-8 ]. The PTC solar area has 8 parallel-

connected loops, each containing 9 solar arrays. A single loop of readers has 10 readers

designated for getting ready and evaporated, while the final two readers are allocated for

overheating. A separation device with an exit water rating of 0.9 is positioned between

the evaporator unit and the superheater in order to ensure adequate cooling of the ab-

sorber’s tubes in continuous operation. Recirculating and injecting valves are employed

to enhance management of the solar field exit heat. Table 1 delineates the design aspects

of the PTC [9 ]. Regarding the power block as illustrated in Table 2, the steam pressure and

temperature at the turbine inlet are established at 70 bar and 350°C, correspondingly. Due

to the plant's limited dimensions, a solitary steam obtaining range, with a pressure limit

of 3.1 bar to 6.1 bar, was included to supply a deaerator. The air-cooled condenser was

evaluated with a design maximum pressure for operation of 0.2 bar.

Table 1. Photovoltaic radiation characteristics

Table 2. Specifications for the energy unit.

A particular collector's total length (m)

99

Pressure and temperature at turbine inlet

Pressure and temperature at solar field inlet

Deaerator pressure (bar)

78bar-380°C

Each receiver's gross collectors’ size (m²)

Iron isolator tube's outside perimeter (m)

Iron absorbers tube with inner diameter (m)

The quantity of 90° angles

623

93bar-170°C

0.082

0.061

4

7.2

0.192

82/91

6.3

Condenser pressure (bar)

HP/LP Turbine isentropic efficiency (%)

Gross power (MW)

The degree of roughness of the isolator tube

Maximum refractive effectiveness

8.59*10^-4

0.901

15

Net power (MW)

6

Tension decreases in the sun radiation (bar)

Net electric efficiency (%)

24.1

Two distinct ways to operate for a steam turbine were evaluated: the first, termed

“sliding pressure,” entails an inverse variation of the turbine inlet pressure with the steam

flow rate, while the second, referred to as “throttle mode,” maintains an unchanged tur-

bine entry pressure equal to 70 bar, despite a steam flow rate entering the turbine that is

below the design specification. Additionally, steam from exhaust parameters were metic-

ulously computed, considering kinetic expenses as an effect of the emission volumetric

flow Figure 2. The emission waste graph is a causal relationship for an entropy differential

known as combustion waste (CW). When applied to the entropy at the expanding path

conclusion (EPC), it enables the accurate calculation of turbine power per mass unit (W)

as follows [10 ]:

(

)

( )

1

푊 = ℎ₁− ℎ_퐸푃퐶+ ꢀ푊

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900

800

700

600

500

400

300

200

100

0

50

100

150

200

250

300

Normal exhaust volume flow

Figure 1. Diagram of the simulated DSP station

Figure 2. Its standard daily brightness

Based on climate information from the Meteonorm database structure, a second gas-

fired engine is activated when the steam flow rate is less than one-third of the design value

to prevent power station closure throughout the evening. Because of reduced sinusoidal

expenses, Figure 3 exhibits a rise in solar irradiation throughout the summer, when PTC

may capture a sizable portion [11 ].

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

Figure 4. Illustration of the DSP station's hourly model-

Figure 3. Mean monthly sunlight in Iraq

ing process in Iraq [12 ]

2.2 Technique and parameters of the experiment

In the context of Iraq, a thorough modeling of the DSP solar field was developed for

both linear Fourier collections and parabola dips. The first method uses a custom algo-

rithm that calculates both the pressure drop and solar field steam generation based on

the required quality of steam and solar radiation. The latter makes it possible to incorpo-

rate sophisticated control techniques like narrowing and turning on the second boiler at

evening. Using an iterative method, the two programs collaborate to offer an initial esti-

mate of the solar field performance Figure 4.

To prevent a power station, collapse at nighttime, an auxiliary gas-fired boiler acti-

vates when the velocity of steam falls below one third of the intended level (8.5 kg/s),

therefore maintaining a minimum steam flow rate of 2.8 kg/s.

The referred to location is Madrid. The annual DNI for the location is 1625 kWh/m2,

based on meteorological data from the Meteonorm dataset. Figure 3 demonstrates a rise

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in solar radiation during the summer months, when PTC may capture a substantial por-

tion of the DNI, owing to reduced sinusoidal costs.

3. Results

A comprehensive model of the DSP solar field was developed for both parabolic

troughs and linear Diffraction collectors inside a combined Octave setting. In the previous

instance, a custom algorithm calculates the steam output as well as the drop of the solar

surface, contingent upon the solar rays and the required vapor grade. The last feature

permits the incorporation of complex control schemes, involving the activation of the aux-

iliary boiler at nighttime and refocus. Both projects cooperate to provide a preliminary

assessment of the sun's radiation efficiency via an iterative procedure Figure 4.

Temperature input and velocity equilibria were verified at each dx. The controlling

parameters are the liquid speed in the heater and the energy value in the evaporator/su-

perheater. The X-Steam utility facilitated the calculation of thermal characteristics of wa-

ter and steam under all conditions of heat, pressure, and steaming condition.

Furthermore, concentrated and dispersed pressure losses were calculated for both

one-phase and two-phase modules independently, as recommended by [13 ]. Concen-

trated losses consider four conventional 89° elbows, while dispersed effects are computed

at each differential segment, because they involve shearing loss across the whole length

of the module. In two-phase circulation, pressure losses are amplified by an amount de-

pendent upon steam reliability, as shown by [13 , 14 ]. The Matlab code produces results

for pressure and temperature at the solar field exit, which are displayed alongside the

steam rate of flow provided. The last parameter undergoes additional modification: if

pressure and temperature surpass the maximum flow rate thresholds, focusing is initi-

ated; conversely, if pressure and temperature fall below the lowest possible flow rate, the

second boiler turns on and use of fossil fuels is considered (refer to Figure 4). The reader

is directed to [15 ] for a comprehensive account of the formulas used in the solar field

model. This research excludes thermal power storing. Focusing has been disabled.

Yearly numerical simulations have been conducted to assess the efficiency of the DSP

plant during various turbine operational conditions. Outcomes are given by concentrating

on a representative both summer and winter workday to examine the intricacies of part-

load performance. Subsequently, data from one-year models are juxtaposed to assess the

influence of turbine operational modes on power production and solar-to-electric perfor-

mance.

3.1. Hourly Modeling Outcomes

Climatic circumstances regarding the outside temperature and DNI patterns are

shown in Figures 5a and 5b for the chosen days: one in winter, on November 15th, and

one in summer, June 15th. The minimum outside temperature is around 5°C in winter,

while the maximum temperature reaches 51°C during summer afternoons, coinciding

with a peak Direct Normal Irradiance (DNI) of 750 W/m². In November, the peak sun

radiation is restricted to 640 W/m². Figures 6a and 6b illustrates the total electrical power

and total electric performance of the DSP, calculated as the proportion of total power pro-

duction to solar heat input. Four patterns are shown throughout time to accommodate

winter and summer climates as well as throttle and sliding turbine settings.

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January

July

January

July

1200

1000

800

600

400

200

0

60

50

40

30

20

10

0

5

10

15

20

25

0

5

10

15

20

25

Time in Hours

Figure 5a. Temperature of the day

January July

Figure 5b. Sunlight exposure per day

January July

7

6

5

4

3

2

1

0

3

2.5

2

1.5

1

0.5

0

5

10

15

20

25

0

5

10

15

20

25

Time in Hours

Figure 6a. Gross energy usage per day

Figure 6b. Use of fossil fuels

Beginning from left to right, the total energy curves indicate that the intended power

point of 6 MWe was surpassed for 10 hours on June 15th. In November, the power pro-

duction is consistently below fifty percent of the rated amount throughout the day.

The causes for this are associated with the elevated sunlight and high visibility dur-

ing summer, contrasted with the diminished solar energy and suboptimal performance

during winter. The proportion of solar radiation captured decreases in winter due to its

cosine impact and reduced temperature outside.

The beneficial impact of the sliding setting on total energy performance, compared

to the accelerator setting, during midnight at minimal load usage results in a productivity

increase of up to 2%; during daytime hours, the enhancement in performance is below

2%. The decreased effectiveness of the accelerator state under partial load is attributable

to choking losses in the high-pressure turbine phase. The restriction diminishes the gen-

eral effectiveness of the HP turbine when the steam flow rate falls below the intended

threshold. In contrast, the sliding operation maintains a nearly constant total turbine out-

put at the design value, regardless of the steam flow rate Figure 7.

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100

90

80

70

60

50

40

30

20

10

0

Throttle

Sliding

1.1

1

0.9

0.8

0.7

0.6

0.5

0.4

1

3

5

7

9

11

13

Time in Hours

Figure 7. The total efficiency of an HP rotor

Figure 8. Median total energy production per month.

Concentrating on the sliding mode, it is noteworthy that on the chosen days, the per-

centage consistently remains below the design threshold (24%) during periods of intense

solar radiation and moderate temperatures. A greater quantity of solar energy is accessi-

ble at elevated ambient temperatures, hence diminishing the effectiveness of the ranked

cycle to around 24%. It is well recognized that heat dissipation to air in a dry cooling sys-

tem is crucial during hot weather. During winter, low temperatures combined with weak

steam output result in 24% at 12 hours. During nightfall, the plant's performance at mini-

mal load is only influenced by the outside temperature, which is three percent greater on

winter days.

3.2. Yearly Modeling Outcomes

Figure 8 illustrates the typical monthly total power generation for both turbine set-

tings. The sliding phase guarantees increased total energy production consistently during

every season, particularly during winter months when the plant works at partial load con-

tinuously. Figure 8 illustrates the total energy effectiveness of the DSP performances for

each hour of the entire year, correlated with DNI. Values of DNI below 360 W/m2 were

excluded owing to severe off-design situations. A second-degree quadratic was deter-

mined to be the optimal estimate for both blade speeds. A limit of 24.1% is attained for

accelerator setting.

Table 3. DSP operations on an annual basis.

Throttle mode

Sliding mode

Electricity Gross energy (MWh/day)

Gross energy performance on average (%)

Mean level at the turbine's intake (bar)

Annual usage of fossil fuels (kg/h)

53.1

18.2

73.8

501

53.6

19.1

74

504

The outcomes of the yearly experiments are encapsulated in Table 3. In comparison

to the accelerator setting, the sliding selection yields about 6% more total electrical power

annually, accompanied by an enhanced average total efficacy (19.7% against 21.3%). The

mean turbine intake pressure is around fifty percent of the intended amount, so indicating

that the DSP generator works at partial capacity for the majority of every year.

The sole drawback of sliding operation is a marginal increase in the use of fossil fuels

(+3.3%), attributed to the elevated entropy of the hot steam reaching the high-pressure

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turbine; the heated steam maintains the same temperature as in accelerator function but

operates at reduced pressure ranges. This disadvantage mostly manifests at nighttime.

5. Conclusions

A modeling approach using three distinct simulation platforms, including MATLAB,

has been employed to predict the performance of a 6MWe DSP solar power plant, devel-

oped under the INDITEP program. The coexistence of different codes allowed the user to

take the best from each programming language. Specifically, it is the most appropriate

platform for addressing transient irradiation intervals; it additionally excels in forecasting

energy unit performance under partial load while adeptly handling the specifics neces-

sary for DSP solar environment modeling. Annual models with a one-hour time increment

were conducted for two distinct operational modes of the HP steam turbine, namely "slid-

ing" and "acceleration" inlet temperature. The sliding mode yielded a 6% increase in net

power generation and a 10% enhancement in net power performance annually, as com-

parison to the throttle mode. The only disadvantage is a 3.1% increase in energy use.

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