Reference no: EM133289889 , Length: word count:3300
Learning Outcome 1: Apply design aspects of wind and wind-solar hybrid systems.
Question 1: It has been proposed to design and install an off-grid wind plant to generate the electricity requirement of a load that has no access to the national electric power grid. The electrical load has the following components and behavior:
• Ten 18 W fluorescent lamps with electronic ballast used for 9 hours per day.
• Ten 60 W fan used for 8 hours each per day.
• Four 250 W refrigerators that runs 24 hours per day with compressor run 12 hours and off 12 hours.
• A 12 kW water pump that runs 6 hours at rated flow, 2 hours at ¾ flow, and 2 hours at 1/2 flow per day. Power supply 3-phase, 400 V, 50 Hz; Rated power 12 kW; Rated flow 2 m3s-1; Pump efficiency: at rated flow 85%, at ¾ flow 70%, at ½ flow 50%; Motor efficiency: at full load 93.1%, at ¾ load 92.4%, at ½ load 90.4%; Motor p. f.: at full load 68%, at ¾ load 66.2%, at ½ load 62.6%. Head may be assumed constant.
Recorded wind velocity data at 10 m at the site over a period of one year shows the distribution given in Table Q1-1.
Table Q1.1: Wind data distribution at 10m over a period of one year
|
v[ms-1]
|
hrs/yr
|
v [ms-1]
|
hrs/yr
|
v [ms-1]
|
hrs/yr
|
v [ms-1]
|
hrs/yr
|
|
0
|
30
|
5
|
1006
|
10
|
562
|
15
|
90
|
|
1
|
277
|
6
|
964
|
11
|
446
|
16
|
24
|
|
2
|
530
|
7
|
891
|
12
|
337
|
17
|
10
|
|
3
|
752
|
8
|
808
|
13
|
245
|
18
|
4
|
|
4
|
920
|
9
|
692
|
14
|
172
|
19
|
0
|
Total hours = 8,760
For multiple reasons, including the fact that the site is not obstructed by any surrounding infrastructure or tall trees, it has been proposed to consider VAWTs. Number of autonomous days is 4.
Battery specifications:
Nominal voltage = 24V Nominal capacity = 250 Ah Depth of discharge = 90% Discharge efficiency = 95%
Battery capacity may be expected to be 90% towards the end of its life.
(a) Calculate the daily energy and potential maximum power consumption of the load.
(b) AC-DC/charge controller and inverter efficiencies are 90% and 95%, respectively. Cable losses etc. account for 10%. Estimate the annual energy requirement from the wind generators.
(c) Graphically represent the wind velocity data distribution given in Table Q1.1 using a clearly labelled histogram.
(d) Calculate the average wind power density (WPD) at the site. Density of air is 1.225 kg/m3.
(e) Calculate the rotor size, blade height, power and speed rating of the wind turbine. Aspect ratio = h/R = 2, capacity factor= 0.3, tip speed ratio= 7. Rotor power coefficient, CP = 0.4, rotor to generator mechanical losses 10%, generator losses 10%. Number of operational hours per year is 8760 hrs.
(f) Provide a clearly labeled schematic diagram of this wind power system showing all the key components and their interconnections. In here, also include a sketch of the battery pack topology. Use black/red colors to show the dc lines and green/blue colors for ac lines.
(g) Calculate the inverter sizing and recommend a commercial inverter for this application
(h) Determine the total battery capacity required.
(f) Determine the battery pack topology (series and parallel connections) for this selection. Off-grid, single-phase, wind power inverter input voltage is 240 Vdc.
Question 2
In order to improve the reliability of the standalone power system, it has been also proposed to consider a wind-solar PV hybrid system instead of the purely wind power system as in Q1. This way, it is also expected to reduce the number of autonomous days to 2.
The solar PV sub-system will be using 12 Vdc, 110 Wp PV module. Panel generation factor at the site may be taken to be 3.52 watthours per day per Wp capacity.
PV module specifications: Pm = 440 Wp
Vm = 41.31 Vdc Im = 10.66 A
Voc = 49.95 Vdc Isc = 11.26 A
(a) Assuming that MPPT will be available, calculate the number of PV panels required if the load is to be served by a purely solar PV system. Total related system losses and panel derating effect may be taken to be 20%.
(b) With logical argument, suggest how you propose to downsize the wind turbine (in Q1) and solar PV capacity (in Q2(a)) to realize a meaningful hybrid system. Select a turbine-generator set available in the market with the capacity in the range 40-60% of the capacity of the generator in the wind only option.
(c) Redo the sizing of the battery bank and show the battery pack topology
(d) Provide a clearly labeled schematic diagram of this wind-solar PV hybrid power system showing all the key components and their interconnections. In here, also include a sketch of the solar panel and battery pack topology. Use black/red colors to show the dc lines and green/blue colors for ac lines. Select a suitable solar charger from the market.
(e) System control is important to keep a standalone micro-grid of the proposed nature stable. Using a flowchart, give an operating strategy for this purpose.
(f) In a standalone power system, power produced has to be balanced with the power consumption and storage to keep the system stability. Discuss 3 different methods that can be adopted in this proposed wind-solar PV hybrid system to ensure the power balance and hence stability.
(g) Clearly mention all the assumptions made in each section