Solar and Wind Power - Chalmers Publication Library...

35
Page 1 of 35 Solar and Wind Power Ingemar Mathiasson January 2016 Department for Energy and Environment Division of Electric Power Engineering Chalmers University of Technology

Transcript of Solar and Wind Power - Chalmers Publication Library...

Page 1: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 1 of 35

Solar and Wind Power Ingemar Mathiasson

January 2016

Department for Energy and Environment Division of Electric Power Engineering Chalmers University of Technology

Page 2: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 2 of 35

Content

1 INTRODUCTION ................................................................................................................................ 2

2 THE STUDY OBJECT ....................................................................................................................... 3

3 THE SIMULATION SYSTEM ............................................................................................................ 7

4 MODULE WIND_TURBINE .............................................................................................................. 9

5 SIMULATIONS ................................................................................................................................. 12

5.1 SOME BASIC PARAMETERS ........................................................................................................ 12 5.2 WIND SPEED .............................................................................................................................. 12 5.3 SOLAR POWER ........................................................................................................................... 13 5.4 ELECTRICAL LOAD ...................................................................................................................... 15 5.5 TESTS WITH VARYING ANGLE Β .................................................................................................. 16 5.6 TESTS WITH VARYING ANGLES Β AND Φ .................................................................................... 17 5.7 TESTS WITH VARYING NUMBER OF TURBINES............................................................................ 20 5.8 TESTS WITH VARYING AREA OF SOLAR CELLS ........................................................................... 21 5.9 TESTS WITH VARYING STORAGE CAPACITY ............................................................................... 23

6 CONCLUSION .................................................................................................................................. 33

6.1 TESTS WITH VARYING ANGLE Β AND FIXED ANGLE Φ = 45º ....................................................... 33 SEE SECTION 5.5. .................................................................................................................................... 33 THE OPTIMUM ANGLE Β IS 0º. TABLE XV SHOWS THE ANNUAL DECREASE OF SOLAR ENERGY FOR

VARYING VALUES OF ANGLE Β RELATIVE TO 0º. ....................................................................................... 33 6.2 TESTS WITH VARYING ANGLES Β AND Φ .................................................................................... 33 6.3 TESTS WITH VARYING NUMBER OF TURBINES............................................................................ 33 6.4 TESTS WITH VARYING AREA OF SOLAR CELLS ........................................................................... 33 6.5 TESTS WITH VARYING STORAGE CAPACITY ............................................................................... 34

7 REFERENCES .................................................................................................................................. 35

1 INTRODUCTION

This document deals with the analysis of a small electrical power system, aimed for use in a pivat household. The system has three main components:

Page 3: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 3 of 35

Wind power unit

Solar power unit

Energy storage unit

Extra auxiliaries to produce deficit energy

Electrical load

The system is connected to the utility grid to balance the power. This means that the utility grid can be used for importing power deficit and for exporting excess power. Section 2 describes the basic structure of the system. The study is based on simulations where solar radiation, wind speed and electrical load are generated stochastically under given prerequisites. The simulation system is briefly described in section 3. In this study wind power turbine “Skystream 3.7”, manufactured by Xzeres, USA, has been used for wind power production. This turbine can be regarded as a good example of powerful turbines for private usage. Some questions that have been investigated:

Appropriate alignment of solar panels in vertical respective horizontal direction

Impact of wind power as a part in the system

Impact of solar power as a part in the system

Impact of energy storage as a part in the system

Need of extra auxiliaries to produce deficit energy The study is consistently based on simulations corresponding a time period of one year (365 days). This means that the study is focused on the annual result for all cases studied.

2 THE STUDY OBJECT

The object to study is a small electrical power producing system with wind and power as power sources. The system is aimed for use in a pivat household. The solar power system is built up according to following specification:

Page 4: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 4 of 35

Photovoltaic solar cell panels

Total effective solar cell area: 50 m2 resp. 100 m2

Total efficiency for solar power system: 13.54 %

Solar cell material: Silicon The intention is to install the solar panels on a house roof according to Fig 2.1. The angle φ in this figure corresponds to the angle between the surface normal of the solar cell panels and direction to zenith.

Fig. 2.1. Installation of solar cell panels on a house roof.

Fig 2.2 illustrates the installation in the horizontal plane. The angle β corresponds to the angle between the surface normal of the solar cell panels and direction to south.

Page 5: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 5 of 35

Fig. 2.2. Installation of solar cell panels in in the horizontal plane.

The wind power system is built up according to following specification:

Wind power turbine: “Skystream 3.7”, manufactured by Xzeres, USA

Maximum power per turbine: 2.4 kW

Total efficiency for wind power system beyond the influence of Cp (see section 4): 80 %

Fig 2.3 shows an image of the wind power turbine “Skystream 3.7”. For more information regarding the wind power turbine see [5] and [6].

Page 6: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 6 of 35

Fig. 2.3. Image of the wind power turbine “Skystream 3.7”.

Page 7: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 7 of 35

3 THE SIMULATION SYSTEM

Fig 3.1 shows the main components in the power system.

Fig. 3.1. The main components in the power system.

Subsystems in the power system according to Fig 3.1: Wind Power: Wind power plant. Solar Power: Solar power plant. Utility grid: Power grid with facility to handle situations of energy deficit and energy surplus. Energy storage: Storage device with two purposes: 1) To store surplus energy. 2) To supply energy to the local grid to meet an energy deficit. Auxiliaries: Equipment to produce deficit energy. This can be regarded as a complement to the possibility of energy balance from the utility grid Electrical load: Active and reactive local electrical load. PE: Power electronics for electrical adaptation.

Page 8: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 8 of 35

The simulation system is built up by 9 modules according to Table I. The intention is to give a statistical basis for evaluation of the power system.

Table I. The modules in the simulation system.

System Modules Function

Wind_make Stochastic wind speed

Wind_turbine Electrical wind power

Extinction_make Stochastic extinction coefficients

Sun_intensity Solar irradiation

Sun_panel_generator Electrical solar power

Load_make Stochastic load

Connect_gen_load Handling of electrical power status as a result of power production and power

consumtion

Storage_distribution Handling of the process regarding energy storage and usage of utility grid

Power_evaluate Statistic evaluation of total simulation

The simulation flowchart is illustrated in Fig. 3.2. The loop is repeated “N” times. Evaluation of the simulation is presented in the form of statistical parameters.

Fig. 3.2. Simulation flowchart. The loop repeated “N” times.

The simulation system is described in [1] that deals about an autonomous power system consisting of wind power and solar power. More detailed information can also be find in [2] - [4]. Regarding module “Wind_turbine”: A special version has been used in this study. This version is described in section 4, below.

Page 9: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 9 of 35

4 MODULE WIND_TURBINE

The module has been adapted for wind turbine Skystream 3.7, manufactured by Xzeres, USA. The program module “Wind_turbine” simulates the function of a wind farm consisting of one or more wind turbines. The active generated power is calculated according to:

Equ. 1 Pw = 𝐂𝐩 × 𝛒 × 𝐀 × 𝐕𝟑×𝐏𝐟𝐰 ×𝐍𝐭

𝟐

Where:

Pw: Generated active wind power (W) Cp(V): Power coefficient

: Air density (kg/m3) A: Rotor sweeping area (m2) V: Wind speed (m/s) Pfw: Wind turbine efficiency excluding Cp: 80 %. This parameter includes

generator and power electronics Nt: Number of wind power turbines in the farm

The air density () is calculated according to:

Equ. 2 = 1.293

1+0.00367×Tair ×

Pair

1013

Where: Tair: Air temperature (°C) Pair: Air pressure (mbar) The rotor sweeping area (A) is calculated according to:

Equ. 3 A = 𝝅 × 𝐃𝟐

𝟒

Where: D: Rotor diameter

Power coefficient Cp(V) for “Skystream 3.7” has been measured up as presented in [5]. Fig 4.1 shows the connection between Cp and wind speed.

Page 10: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 10 of 35

Fig. 4.1. Power coefficient Cp vs wind speed. This curve is presented in [5].

In this study the curve according to Fig 4.1 has been adapted to a polynomial of degree 10. Fig 4.2 illustrates a comparison between measured and adapted values.

Page 11: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 11 of 35

Fig. 4.2. Power coefficient Cp vs wind speed. Measured and polynomial adapted values. Solid curve: Measured values. Dotted curve: Adapted values.

Some turbine related parameters in this study:

Rotor diameter: 3.72 m

Tair: 15 ºC

Pair: 1013 mbar

Maximum output power from turbine: 2.4 kW

Minimum wind speed for output power: 3.5 m/s

Maximum wind speed has been limited to 19 m/s. This due to lack of available measurement values concerning the parameter Cp

Wind power efficiency excluding Cp: 80 % but including generator and power electronics

Turbine height over ground: 10 m

0 2 4 6 8 10 12 14 16 18 20-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

Wind speed (m/s)

Cp

Power coefficient Cp vs wind speed. Measured and polynomial adapted values.

Page 12: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 12 of 35

5 SIMULATIONS

5.1 Some basic parameters

Time resolution: 10 minutes

Corresponding start time for simulation: 00.00, March 20

Corresponding simulation time 365 days

Number of repeating cycles for each simulation (parameter N according to Fig 3.2): 200

Location for power system: longitude = 11.968°, latitude = 57.710°. This corresponds to Göteborg, Sweden

5.2 Wind speed

The following Weibull parameters have been used:

A = 6.3

C = 1.9

Fig 5.1 and Fig 5.2 show examples of simulated wind speeds. Fig 5.1 illustrates the total time range, while Fig 5.2 illustrates a small part of the total range.

Fig. 5.1. Example of simulated wind speed for 365 days (8760 hours).

0 1000 2000 3000 4000 5000 6000 7000 8000 90000

2

4

6

8

10

12

14

16

18

20Wind Speed vs Time

Time (hour)

Win

d S

peed (

Mete

r per

sec)

Page 13: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 13 of 35

Fig. 5.2. Example of simulated wind speed. Part of the total time range.

5.3 Solar power

Cloudiness probability: 65 %.

Fig 5.3 and Fig 5.4 show examples of simulated solar powers. Fig 5.3 illustrates the total time range, while Fig 5.4 illustrates a small part of the total range.

4490 4500 4510 4520 4530 4540 4550 45600

2

4

6

8

10

12

14

16

Wind Speed vs Time

Time (hour)

Win

d S

peed (

Mete

r per

sec)

Page 14: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 14 of 35

Fig. 5.3. Example of simulated solar power for 365 days (8760 hours).

Fig. 5.4. Example of simulated solar power. Part of the total time range.

0 1000 2000 3000 4000 5000 6000 7000 8000 90000

1

2

3

4

5

6

7Solar Power vs Time

Time (hour)

Sola

r P

ow

er

(kW

)

2080 2100 2120 2140 2160 2180 22000

1

2

3

4

5

6

Solar Power vs Time

Time (hour)

Sola

r P

ow

er

(kW

)

Page 15: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 15 of 35

5.4 Electrical load

The following applies to the electrical load:

Type of load: Residential

Annual energy consumption: 10 000 kWh

Fig 5.5 and Fig 5.6 show examples of simulated solar powers. Fig 5.5 illustrates the total time range, while Fig 5.6 illustrates a small part of the total range.

Fig. 5.5. Example of simulated electrical load power for 365 days (8760 hours).

0 1000 2000 3000 4000 5000 6000 7000 8000 90000

0.5

1

1.5

2

2.5

3Electrical Load Power vs Time

Time (hour)

Local Load P

ow

er

(kW

)

Page 16: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 16 of 35

Fig. 5.6. Example of simulated electrical load power. Part of the total time range.

5.5 Tests with varying angle β

Simulations have been performed with varying angle β and fixed angle φ = 45 º. Angle β is the angle between surface normal of solar cell panels and direction to south. Angle φ is the angle between surface normal of solar cell panels and direction to zenith. Table II lists the simulation results.

Table II. Simulation results. φ = 45 º.

Angle relative to south (degrees)

Annual solar energy (kWh)

0 3746

22.5 3643

45 3322

90 2272

135 1145

180 617.9

3770 3780 3790 3800 3810 3820 3830 3840 3850 3860 3870

0.5

1

1.5

2

2.5

Electrical Load Power vs Time

Time (hour)

Local Load P

ow

er

(kW

)

Page 17: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 17 of 35

Fig. 5.7. Annual produced energy vs angle β. Angle φ is 45 º.

5.6 Tests with varying angles β and φ

Simulations have been performed with varying angles β and φ. Angle β is the angle between surface normal of solar cell panels and direction to south. Angle φ is the angle between surface normal of solar cell panels and direction to zenith. Table III and Table IV list the simulation results.

Table III. Simulation results. β = 0 º. Angle relative to zenith (degrees)

Annual solar energy (kWh)

35 3742

40 3767

45 3746

50 3717

0 20 40 60 80 100 120 140 160 180500

1000

1500

2000

2500

3000

3500

4000Annual produced energy vs angle to south. Angle rel zenith is 45 º

Angle to south (degrees)

Energ

y (

kW

h)

Page 18: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 18 of 35

Table IV. Simulation results. β = 5 º. Angle relative to zenith (degrees)

Annual solar energy (kWh)

35 3728

40 3746

45 3746

50 3714

Fig. 5.8. Annual produced energy vs angle φ. Angle β is 0 º.

35 40 45 503710

3720

3730

3740

3750

3760

3770Annual produced energy vs angle to zenith. Angle rel south is 0 º

Angle to zenith (degrees)

Energ

y (

kW

h)

Page 19: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 19 of 35

Fig. 5.9. Annual produced energy vs angle φ. Angle β is 5 º.

Fig. 5.10. Annual produced energy vs angle φ. Angle β is 0 resp 5 º.

35 40 45 503710

3715

3720

3725

3730

3735

3740

3745

3750Annual produced energy vs angle to zenith. Angle rel south is 5 º

Angle to zenith (degrees)

Energ

y (

kW

h)

35 40 45 503710

3720

3730

3740

3750

3760

3770Annual produced energy vs angle to zenith. Angle rel south is 0 º resp 5 º

Angle to zenith (degrees)

Energ

y (

kW

h)

5 º

0 º

Page 20: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 20 of 35

5.7 Tests with varying number of turbines

Simulations have been performed with varying number of turbines.

No energy storage

No solar power

Table V. Simulation results with varying values of wind turbines.

Storage capacity N = 0.

Number of

turbines

Exported energy (kWh)

Imported energy (kWh)

Exported - Imported

(kWh)

0 0 9994 -9994

1 344.3 7326 -6982

2 1831 6122 -4291

3 3899 5471 -1572

4 6199 5088 1111

5 8648 4788 3860

6 11400 4509 6891

7 13640 4393 9247

Fig 5.11 shows the difference between exported and imported energy vs number of turbines.

Fig. 5.11. Exported energy – Imported energy vs Number of Turbines.

0 1 2 3 4 5 6 7-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1x 10

4 Export - Import vs Number of Turbines

Number of Turbines

Energ

y (

kW

h)

Page 21: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 21 of 35

Fig 5.12 shows imported energy vs number of turbines.

Fig. 5.12. Imported energy vs number of Turbines.

5.8 Tests with varying area of solar cells

Simulations have been performed with varying area of solar cells.

No energy storage

Number of wind turbines = 4 Table VI. Simulation results with varying area of solar cells.

Solar cell area (m2)

Exported energy (kWh)

Imported energy (kWh)

Exported - Imported

(kWh)

0 6199 5088 1111

25 7345 4350 2995

50 9127 4087 5040

100 12360 3968 8392

200 19520 3835 15685

400 33850 3680 30170

0 1 2 3 4 5 6 74000

5000

6000

7000

8000

9000

10000Imported energy vs Number of Turbines

Number of Turbines

Energ

y (

kW

h)

Page 22: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 22 of 35

Fig 5.13 shows the difference between exported energy and imported energy vs solar cell area.

Fig. 5.13. Exported energy – Imported energy vs Solar cell area.

Fig 5.14 shows imported energy vs solar cell area.

0 50 100 150 200 250 300 350 4000

0.5

1

1.5

2

2.5

3

3.5x 10

4 Exported energy – Imported energy vs Solar cell area.

Solar cell area (m2)

Energ

y (

kW

h)

Page 23: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 23 of 35

Fig. 5.14. Imported energy vs Solar cell area.

5.9 Tests with varying storage capacity

Simulations have been performed with varying storage capacity.

Number of wind power turbines = 4

Solar cell area = 100 m2

Angle β: 0 º

Angle φ = 40 º

A parameter “N” is defined according to:

Equ. 4. Storage capacity(N) = N × 𝐀𝐧𝐧𝐮𝐚𝐥 𝐜𝐨𝐧𝐬𝐮𝐦𝐞𝐝 𝐞𝐧𝐞𝐫𝐠𝐲

𝟑𝟔𝟓

Where “Annual consumed energy” = 10 000 kWh Table VII shows simulation results with varying storage capacity and storage initiation = 0.5 × N. Min storage = 0.5 × N. “Storage initiation” corresponds to the value at simulation start. “Min storage” corresponds to the minimum accepted storage value.

0 50 100 150 200 250 300 350 4003600

3800

4000

4200

4400

4600

4800

5000

5200Imported energy vs Solar cell area

Solar cell area (m2)

Energ

y (

kW

h)

Page 24: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 24 of 35

Table VII. Simulation results with varying storage capacity. Storage initiation = 0.5 × N. Min storage = 0.5 × N.

Storage capacity

(N)

Exported energy (kWh)

Imported energy (kWh)

Exported - Imported

(kWh)

0 12360 3968 8392

0.5 11370 2850 8520

1 10800 2343 8457

2 10450 1709 8741

4 9531 1088 8443

8 9154 677.2 8477

16 8763 332.2 8431

32 8183 140.0 8043

64 7553 30.80 7522

128 6464 19.41 6445

Fig 5.15 shows imported energy vs storage capacity. Storage initiation = 0.5 × N. Min storage = 0.5 × N.

Fig. 5.15. Imported energy vs Storage capacity. Storage initiation = 0.5 × N.

Min storage = 0.5 × N.

0 20 40 60 80 100 120 1400

500

1000

1500

2000

2500

3000

3500

4000Imported energy vs Storage capacity. Storage init = 0.5 × N. Min storage = 0.5 × N.

Storage capacity (N)

Energ

y (

kW

h)

Page 25: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 25 of 35

Table VIII shows simulation results with varying storage capacity and storage initiation = N. Min storage = 0.5 × N. “Storage initiation” corresponds to the value at simulation start. “Min storage” corresponds to the minimum accepted storage value.

Table VIII. Simulation results with varying storage capacity. Storage init = N. Min storage = 0.5 × N.

Storage capacity

(N)

Exported energy (kWh)

Imported energy (kWh)

Exported - Imported

(kWh)

0 12360 3968 8392

0.5 11330 2859 8471

1 10860 2329 8531

2 10480 1706 8774

4 9584 1073 8511

8 9267 653.7 8613

16 9016 312.1 8704

32 8707 117.5 8590

64 8621 7.2 8614

128 8628 0 8628

Fig 5.16 shows imported energy vs storage capacity. Storage initiation = N. Min storage = 0.5 × N.

Fig. 5.16. Imported energy vs Storage capacity. Storage initiation = N. Min storage = 0.5 × N.

0 20 40 60 80 100 120 1400

500

1000

1500

2000

2500

3000

3500

4000Imported energy vs Storage capacity. Storage init = N. Min storage = 0.5 × N.

Storage capacity (N)

Energ

y (

kW

h)

Page 26: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 26 of 35

Fig 5.17 illustrates imported energy vs storage capacity for storage initiations N resp. 0.5. The difference is only marginal and can be neglected.

Fig. 5.17. Imported energy vs Storage capacity. Storage initiation = N resp. 0.5. Min storage =

0.5 × N. Red curve: Storage initiation = 0.5.

Table IX shows simulation results with varying storage capacity and storage initiation = N. Min storage = 0. “Storage initiation” corresponds to the value at simulation start. “Min storage” corresponds to the minimum accepted storage value. In addition to the information in Table VII and Table VIII, Table IX also presents statistics based on 200 simulations regarding storage level “mean”, “min” and standard deviation.

0 20 40 60 80 100 1200

100

200

300

400

500

600

700

800

900

1000Imported energy vs Storage capacity. Storage init = N and 0.5. Min storage = 0.5 × N.

Storage capacity (N)

Energ

y (

kW

h)

Page 27: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 27 of 35

Table IX. Simulation results with varying storage capacity. Storage initiation = N. Min storage = 0.

Storage capacity

(N)

Exported energy (kWh)

Imported energy (kWh)

Exported - Imported

(kWh)

Storage level

Mean (%)

Storage level

Min (%)

Storage level Std. dev (%)

0 12360 3968 8392 - - -

0.5 10810 2305 8505 55.9 0 3.9

1 10260 1770 8490 61.6 0 3.7

2 9584 1067 8517 67.0 0 4.1

4 9398 601.9 8796 74.7 0 4.3

8 8948 319.2 8629 80.3 0 4.9

16 8818 96.0 8722 86.8 0 5.4

32 8569 4.5 8564 91.7 0 4.6

64 8629 0 8629 95.7 23.0 2.8

128 8853 0 8853 98.1 64.7 1.2

Fig. 5.18 shows imported energy vs storage capacity for the information according to Table IX.

Fig. 5.18. Imported energy vs Storage capacity. Storage init = N. Min storage = 0.

4 10 20 30 40 50 600

100

200

300

400

500

600

700

Storage capacity (N)

Energ

y (

kW

h)

Imported energy vs Storage capacity. Storage init = N.

Page 28: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 28 of 35

Table X to Table XIV show the probability for need of “Extra auxiliaries” (if no connection to a utility grid is on hand) for different storage capacity as a function of accepted minimum storage level. Fig. 5.19 to Fig. 5.23 illustrate the corresponding information in graphs.

Table X. Simulation results with storage capacity N = 8.

Storage level Min (%)

P Extra auxiliaries (%)

5 94.5

10 97.0

15 98.0

20 98.5

25 99.5

30 100

35 100

Fig. 5.19. Probability for need of extra auxiliaries vs accepted minimum storage level. Storage

capacity N = 8.

5 10 15 20 25 30 3594

95

96

97

98

99

100

Storage level (%)

P (

%)

Probability for extra auxiliaries vs accepted minimum storage level. Storage capacity N = 8.

Page 29: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 29 of 35

Table XI. Simulation results with storage capacity N = 16.

Storage level Min (%)

P Extra auxiliaries (%)

5 44.2

10 47.2

20 59.8

30 70.4

40 81.9

50 92.0

60 99.5

65 100

Fig. 5.20. Probability for need of extra auxiliaries vs accepted minimum storage level. Storage

capacity N = 16.

0 10 20 30 40 50 60 7040

50

60

70

80

90

100Probability for extra auxiliaries vs accepted minimum storage level. Storage capacity N = 16.

Storage level (%)

P (

%)

Page 30: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 30 of 35

Table XII. Simulation results with storage capacity N = 32.

Storage level Min (%)

P Extra auxiliaries (%)

5 4.5

10 5.5

20 10.6

30 17.6

40 27.1

50 46.2

60 66.8

70 87.9

80 99.5

82 100

Fig. 5.21. Probability for need of extra auxiliaries vs accepted minimum storage level. Storage

capacity N = 32.

0 10 20 30 40 50 60 70 80 900

10

20

30

40

50

60

70

80

90

100Probability for extra auxiliaries vs accepted minimum storage level. Storage capacity N = 32.

Storage level (%)

P (

%)

Page 31: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 31 of 35

Table XIII. Simulation results with storage capacity N = 64.

Storage level Min (%)

P Extra auxiliaries (%)

5 0

10 0

20 0

30 1.0

40 2.0

50 4.0

60 16.1

70 30.2

80 62.3

90 99.5

91 100

Fig. 5.22. Probability for need of extra auxiliaries vs accepted minimum storage level. Storage

capacity N = 64.

0 10 20 30 40 50 60 70 80 90 1000

10

20

30

40

50

60

70

80

90

100Probability for extra auxiliaries vs accepted minimum storage level. Storage capacity N = 64.

Storage level (%)

P (

%)

Page 32: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 32 of 35

Table XIV. Simulation results with storage capacity N = 128.

Storage level Min (%)

P Extra auxiliaries (%)

5 0

10 0

20 0

30 0

40 0

50 0

60 0

70 0.5

75 4.5

80 9.5

85 24.1

90 54.3

95 98.0

95.73 100

Fig. 5.23. Probability for need of extra auxiliaries vs accepted minimum storage level. Storage

capacity N = 128.

0 10 20 30 40 50 60 70 80 90 1000

10

20

30

40

50

60

70

80

90

100Probability for extra auxiliaries vs accepted minimum storage level. Storage capacity N = 128.

Storage level (%)

P (

%)

Page 33: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 33 of 35

6 CONCLUSION

6.1 Tests with varying angle β and fixed angle φ = 45º

See section 5.5.

The optimum angle β is 0º. Table XV shows the annual decrease of solar energy for varying values of angle β relative to 0º.

Table XV. Annual decrease of solar energy.

Angle β relative to 0 º (degrees)

Annual decrease of solar energy (%)

22.5 3

45 11

90 39

135 69

180 84

As can be observed, the generated solar energy will be reduced only marginally (3 %), if the angle deviates 22.5° relative to the south.

6.2 Tests with varying angles β and φ

See section 5.6.

The conclusion, based on simulations, is that the optimal angle φ (surface normal angle relative to zenith) is located in the region 40º - 45º.

6.3 Tests with varying number of turbines

See section 5.7.

The study is in first hand focused on the total need to import energy (use of auxiliaries) as a function of wind turbines in function. Fig. 5.12 shows the annual imported energy vs number of wind turbines in function. As can be observed the curve fall down quickly in the region 0 to 3 turbines. It tends to flat out at about 4 turbines. This can be a hint regarding the optimal number of turbines in respect of cost. A first simple conclusion, based on simulations, is that the optimal number of wind turbines are about 4. This corresponds to a total maximum wind power of 4 × 2.4 kW = 9.6 kW. This will be used as a suitable starting point for the further power plant design, that includes solar power and energy storage.

6.4 Tests with varying area of solar cells

See section 5.8.

Page 34: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 34 of 35

The study is in first hand focused on the total need to import energy (use of auxiliaries) as a function of solar cell area in function. Fig. 5.14 shows the annual imported energy vs solar cell area in function. As can be observed the curve fall down quickly in the region 0 to 50 m2. It tends to flat out at about 100 m2. This can be a hint regarding the optimal solar cell area in respect of cost. A first simple conclusion, based on simulations, is that the optimal solar cell area is about 100 m2.

6.5 Tests with varying storage capacity

See section 5.9.

The study gives information regarding the connection between energy storage and the probability for need of extra auxiliaries (if no connection to a utility grid is on hand) in combination with accepted minimum storage level. Suppose, for example the following: - probability to need extra auxiliaries: 4 % - minimum accepted storage level: 50 % According to Table XIII, the storage capacity has to be at least N = 64. Suppose: - probability to need extra auxiliaries: 70 % - minimum accepted storage level: 30 % According to Table XI, the storage capacity has to be at least N = 16.

Page 35: Solar and Wind Power - Chalmers Publication Library (CPL)publications.lib.chalmers.se/records/fulltext/230515/... · 2016-01-13 · Wind power turbine: “Skystream 3.7”, manufactured

Page 35 of 35

7 REFERENCES

[1] Mathiasson I. “Simulation of Autonomous Electric Power Systems”. Chalmers University of Technology, Mars 2015.

[2] Mathiasson I. “Solar power. Statistical analysis of extinction coefficients”.

Chalmers University of Technology, June 2015. [3] Mathiasson I. “Wind power. Statistical analysis of wind speed”.

Chalmers University of Technology, January 2015. [4] Mathiasson I. “Modelling of an electrical load”.

Chalmers University of Technology, February 2015. [5] “Experimental Test Site for Small Wind Turbines of Narbonne. Test Report no. 15 version 4 of Mars, 25 2010. Skystream Grid Connected Wind Turbine”. Sud Eoliennes Technologie, Mars 2010. [6] “Marknadsöversikt små vindkraftverk i Sverige”. Svensk Vindkraftförening (SVIF), co-funded by Energimyndigheten.