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Saturday, 20 December 2014

REMOTE AREA POWER SUPPLY SYSTEM


We have seen basics of remote area supply system in our previous post “Remote area power supply system” i.e. part 1, we will suggest first read previous post and then follow this post as this post is in continuation of previous post.

Optimization of the System 

The optimization of the system is to install some component for convenience and comfort for people living in this house, and also life of battery bank can be extended. However, because of the addition of new components, investment and maintain fee increase. 

The optimization can ensure that the system is enough efficient, convenient, and comfort to people, while it will not impact the normal usage of the system, if the system is not optimized. 

Transfer Switch and Generator Upgrade 

Transfer switch can allow the generator to supply electricity directly to the house by switching the power resource from battery bank to generator, and hence the generator will be supporting the house consumption and mean while the excess power of generator can recharge the battery bank. However, to place a transfer switch needs to enlarge the power capacity of the generator; otherwise the generator will not generate sufficient power to supply the house. Thus, the optimization for transfer switch will be with an upgrade of generator.

This report will select Eaton GREEN Automatic Transfer Switch to connect an upgraded generator and loads. This switch can monitor the power output of the power source, and will switch between generator and battery bank automatically, if ever the power output decreased. The operating voltage of the switch is 240 V AC with frequency of 50/60, which is fitted to the house.

Eaton GREEN Automatic Transfer Switch

Because of the addition of transfer switch, the generator can provide electricity directly to the loads, so that a larger power capacity generator is a must. The new generator is expected to supply electricity to the house and meanwhile have the battery bank recharged, and hence the power capacity will be not less than 6252.17 W (sum of peak demanding power and battery bank recharging power), which is determined by assuming that the battery bank can be recharged for one day consumption in less than 5 hours. 

This report selects YAMAHA Gentech 6.8kVA Electric/Recoil Start Petrol Generator for the optimized system, which has capacity of 6800 W in voltage of 230 V. The new generator will recharged the battery bank with no longer time than the previous system, after the battery bank energy is used out and the transfer switch turn on the new generator as power resource.
YAMAHA Gentech 6.8kVA Electric/Recoil Start Petrol Generator

Maximum Power Point Tracker for Solar Array

Maximum Power Point Tracker (MPPT) is a device to ensure the solar array is working at its maximum power. MPPT is also a kind of charge controller and current regulator to protect battery bank from unstable voltage and current. 

This report will select SMA Maximum Power Point Tracker for the solar array, which the 24 V model can bearing 1250 W input power from PV panel and maximum output of 1200 W. The efficiency of this MPPT is 98%, which is very high efficiency, and the energy loss due to MPPT can be neglected, because it is not deserved to purchase another PV panel to cover such little quantity of energy.


SMA Maximum Power Point Tracker

Water Heating Equipment 

As the report estimated previously, the daily hot water consumption is at least 169.8 L, and no excess electricity for water heating from solar array, battery bank and generator, a solar water heater is needed to provide people with hot water. The solar water heater will be installed independently. This report will select Bosch 250 L Electric Boosted Solar Hot Water System for the house.
Bosch 250 L Electric Boosted Solar Hot Water System

Analysis and Calculations

Analysis and Calculations for Options of Economic Evaluation

Assuming the daily consumption of a house is 4.5 kWh, and the yearly consumption is 1642.3 kWh, and hence the consumption in 25 years is 41062.5 kWh, which the evaluation will be based on.

Option A: Grid Connection

The initial investment is 40000, and the electric cost except connection fee is $ 0.25 per kWh.
Cost = [40000/1642.3]+0.25 = 1.22 $

Option B: Petrol Generator & Battery Bank

Model
Industry Rating KVA
Power Watts
Engine
Starting System
Frame
Tank LTS
Fuel LTS/HR
PB033
3.3
2600w
6hp Vanguard
Recoil
Scoop
4
1.8


            
             The performance Data of Powerlite 3.3 kVA Recoil Start Petrol Generator

Running hours = 4.5/3.3= 1.36 hrs
Consumption of fuels = 1.8 * 1.36 = 2.45 L
Assuming the petrol price is $ 1.4 per liter.
Fuel cost per KWh = 2.45 - 1.4/4.5 = 0.76 $ /KWh
Yearly fuel cost = 0.76 * 4.5 * 365 = 1248.3 $

Assuming the inflation rate and interest rate are 8% and 10% respectively in life cycle of 25 years.
Cost of fuel= P W F ( 8% ,10 % ,25)*1248.3=24803.7$

The price of the generator is 915 dollars. Assuming the life of generator is 5 years
Cost of engine = 3840.17$

The system is designed to operate with voltage of 24 V.
Amp hr of battery bank = 4500/24= 187.5 Ah

The battery bank is 6 batteries of Solar Block Sealed Gel Battery 12 V 130Ah connected in series, and two of the series connected in parallel, which can provide 24 V and 260 Ah energy for fitting the system and demanding of the house. 

The price of battery is 819.08 dollars, and hence the price of battery bank is 4914.18 dollars. Assuming that the batter life is 5 years
Cost of battery (after calculation) = 20632.6 $
Final cost per KWh = 1.2 $ / KWh

Option C: Petrol Generator & Battery Bank & PV Panel

The solar array designing is based on the statistics of solar radiation in Melbourne for inclined flat-plate. In order to reduce the size of the system, the solar array is designed according to the solar radiation data of January (summer).
Solar arry power = 4500/7.08 = 908 Watt

Thus, the solar array has to provide at least 908 watts of power, so that the report used Sanyo 230Watt Polycrystalline Solar Panel for economic evaluation. 4 of the panels are installed producing power of 920 watts with 24 V system voltages. 

Therefore, the cost of solar array is 1440 dollars (estimated by using the average price for commercial PV panels searched on websites.
Because of solar array, the cost on fuel is reduced. The fuel cost on each month of one year is estimated as following table shows.

Peak Sun Hour
Daily Energy Produced by PV Panel
Daily Energy Compensated by Petrol Gerator
Daily Cost of Fuel
Monthly Cost of Fuel
in h
in kW
in kW
in dollar
in dollar
7.1
4561.7
-61.7
0.0
-1.4
6.5
4203.9
296.1
0.2
6.8
5.7
3685.1
814.9
0.6
18.6
4.6
2969.6
1530.4
1.2
34.9
3.4
2218.2
2281.8
1.7
52.0
3.1
1967.8
2532.2
1.9
57.7
3.2
2057.2
2442.8
1.9
55.7
3.9
2522.3
1977.7
1.5
45.1
4.8
3076.9
1423.1
1.1
32.4
5.8
3703.0
797.0
0.6
18.2
6.3
4078.7
421.3
0.3
9.6
6.8
4347.0
153.0
0.1
3.5
Cost of Fuel in each Month of a Year
Thus, the total cost of fuel for one year is 334.5 dollar.
Cost of fuels for 25 years = 6646.12 $ 
final cost per KWh = 0.79 $ / KWh

Estimation for Aero Generator

The yearly average wind speed of Melbourne is 11.7 km/h, or 3.25m/s. Air Breeze Marine 24Volt 200Watt Wind Turbine, for example, has rated power of 200 W in wind speed of 12.5 m/s. 

Thus, the ratio of wind speed of Melbourne to rated wind speed is 0.26. Also, the aero generator has cut out wind speed of 49.2 m/s, and hence the ration of cut out wind speed to rated wind speed is 3.94. Based on the two ratios and Figure. A1, the aero generator has average output power only around 1% of its rated power. Such low average output power is not deserved to pay thousands of dollars. 
                                    Estimated of Expected Average Output Power for Aero Generator

Analysis and Calculations for Power Supply System

According to catalogue of appliances, the total power of the households is 7771 W, and the electric energy consumption is 5780 and 5980 kWh for summer and winter respectively. Since it is not likely that all of the appliances are running, and thus the report takes half of total power as peak power of the house, which is 3885.5 W.

Inverter

Inverter has a rated power that must be larger than the peak power of the house, and also the inverter decides the system voltage, which is 24V in this report. The report selected 8ZED 24 V 5000 W Power Inverter for the house, and its efficiency is 90%.

Battery Bank

The battery bank is designed to contain energy twice of the daily consumption of the house. In order to overcome the energy consumption in inverter, the battery bank has to provide more energy for daily use.
Energy for summer day = 5789/0.9 = 267.59 Ah
Energy for winter day = 5980/0.9 = 276.85 Ah

Because winter has larger energy consumption, the battery bank will be designed based on the daily consumption of 276.85 Ah. The energy contained in battery bank should be twice of 276.85 Ah for system voltage of 24 V (the daily depth of discharge is assumed as 0.5)
Minimum energy storage for battery bank = 276.85/0.5= 533.7 Ah

The report selects RayliteMIL17Sbattery bank for the system, which has an allowable discharge efficiency of 90%.
Battery Capacity = 600 * 0.9/276.85 = 1.95 days 
The battery bank can support the system running 1.95 days without recharge.

Battery Charger

The report selects Stunbury NG12/70G for the batter bank, which can recharge the battery bank by 70 A in less than 5 hours with system voltage of 24 V.
Recharging time = 600/70 = 4.29 hrs

Petrol Generator

The output power of petrol generator must satisfy the input power of battery charger. Output power of battery charger has to determined, and then the input power of the charger can be calculated by output power dividing the efficiency of charger.
Charger output power = 70 * 24 = 1680 W
Charger input power = 1680/ 0.9 = 1866.67 W
Thus, the report selects Honda 2kVA Domestic Generator Kitfor the power supply system.

Solar Array

Because the system will be over size in summer, if the solar array is designed based on the daily consumption of winter, the solar array will be designed according to data of summer. 
Peak sun hour of Melbourne in the month of January = 7.08 kwh//m2 day

The peak sun hour of summer (January) is 7.08, which means the number of hours needed at peak sun radiation condition to have an equal amount of energy from sun for one day.
Solar array minimum power = 5780/7.08= 816 W
This report selects Suntech 140W 12V Monocrystalline Solar Panel for the solar array Number of panels = 816/140 = 6 

The arrangement of the panels is that 2 series connected in parallel and each of the series consists of 3 panels, since the panel has operating voltage of 17.6 V and operating current of 7.95 A. The suggested arrangement can provide 35.2 V to fit the system voltage of 24 V.

Analysis and Calculations for Optimization

Household electric appliances in Australia normally work in 230 V and 50/60 Hz. The report selects Eaton GREEN Automatic Transfer Switch for the system.
Because of installation of transfer switch, the petrol generator is directly connected to the house, and hence a new generator that can supply the consuming of house and mean while recharge the battery bank is needed.
Generator minimum power output = 6252.17 W
The report decides YAMAHA Gentech 6.8kVA Electric/Recoil Start Petrol Generator to upgrade the system.

Maximum Power Point Tracker

Maximum Power Point Tracker (MPPT) is a device to ensure the solar array is working at its maximum power. MPPT is also a kind of charge controller and current regulator to protect battery bank from unstable voltage and current. 

This report will selectSMA Maximum Power Point Tracker for the solar array, which the 24 V model can bearing 1250 W input power from PV panel and maximum output of 1200 W. The efficiency of this MPPT is 98%, which is very high efficiency, and the energy loss due to MPPPT can be neglected, because it is not deserved to purchase another PV panel to cover such little quantity of energy. 

Water heating machine capacity 
Daily water consumption = 169.8 l
Therefore, the report selects Bosch 250 L Electric Boosted Solar Hot Water System as the water heating equipment for the house. 


Catalogue of Appliances and Final Optimized Electric Energy Consumption Estimation

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