CASE STUDY SYSTEM 1
Small Stand-Alone Power System
A typical hybrid photovoltaic & diesel small family home system
System design brief
This is a typical remote small country home for a couple with modest energy needs. This small home would use bottled LP gas for heating and cooking applications. The home would also use a solar hot water system for all hot water requirements. A range of appliances would be used in the home such as a washing machine, a television, notebook computer, various kitchen appliances, power tools, and lights. No kettle was included in the load demand as this would be heated on the gas stove top. The average daily energy use was calculated to be 2280 Wh/day using the information supplied by the client. No significant seasonal load was identified in the load assessment. The client will use a small diesel generator as a backup power source that will supplement power from the solar array during periods of low solar energy. The generator will also be available to supplement water heating during these periods although this extra load is not considered as part of the load assessment. (see Energy Calculation Worksheet)
System Sizing
In preparing the system design in 2000 the method used was as outlined within the then draft Standard AS4509.2. In 2002 the AS4509.2 Standard was published. The installation of the system complied with part 3. (See System Sizing Worksheet)
System Installation and Specifications
This system was installed in 2001 and is comprised of the following major components:
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Photovoltaic Modules
The system has an array of 8 BP Solar BP585, 85 Watt PV Modules on an adjustable tilt array stand. The peak output from the array is 680 watts. By adjusting the tilt of the array the output can be maximised depending on the season. For summer this would mean an angle of approximately 30° and in winter an angle of approx. 45°.
The array frame and footings have been designed to appropriate wind loading design codes. |
Photovoltaic Regulator
The Trace C40 charge controller with DVM digital display monitors the battery bank voltage to determine the battery state of charge. It is rated to 40 A at 12, 24 or 48 Vdc.
In the PV charge control mode the controller uses a 3 stage regulation and an automatic (or manual) battery equalisation. The mode is indicated by the colour of the LED (normally green or blinking green).
The installed optional display provides the following information:- PV array current, battery voltage and PV array power. |
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Diesel Generator
The system has a backup 5kVA diesel genset which is manually started. The operator decides when to start the gen set. One condition is low battery voltage. The other condition is when large loads are expected, i.e. welding.
The engine is a Robin DY41D and the generator is a 5kVA unit from Modra Engineering |
Inverter
The inverter changes the DC electricity from the battery bank and solar array to AC electricity for use with standard appliances such as televisions, VCRs, refrigerators, electric drills, other power tools and kitchen appliances. The inverter is a Selectronic SA31 Sine Wave Inverter that has a continous rating of 2200W. This inverter incorporates energy management features.
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Battery Charger
The battery charger takes the 240V AC output from the diesel generator and converts it to a DC voltage to charge the 24V battery bank. The battery charger uses two paralleled Interacter ICS 24/25 chargers giving a maximum charging current of 50 Amps.
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Battery Bank
The battery bank has 4 x 6V SSR700-6, Century Yuasa ENERSUN flooded lead acid batteries connected in series which produces a 24Vdc battery bank with a total rated capacity of 700Ah at the C100 rate. These batteries were chosen to provide approx. 10kWhr of usable storage at a maximum depth of discharge of 60%. This is equivalent to four days of average energy use for this system. These batteries require their electrolyte to be regularly checked and topped up as required with distilled water. |
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DC Switchboard
This box houses the DC circuit breakers. It allows each DC component to be isolated.
For the purposes of the display this box also houses meters that allow the user to see where energy is being supplied from and where it is going. The user can see the battery voltage and current, as well as the PV, inverter and diesel generator current. |
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AC Switchboard
The 240 Vac wiring has been done to relevant Australian Standards (i.e. AS 3000). The switchboard has a safety switch (earth leakage detector), mains isolator switch, a circuit breaker for power points and a circuit breaker for the lights.
The control system is housed in this box along with the standard AC switch board. The small dial at the top is the hour run meter for the diesel which helps to let the user know when maintenance is due. The large knob in the centre switches the system between diesel and inverter. It is not possible to run both at the same time. Also housed in this box is the control for the inverter, allowing the user to make use of the available settings on the inverter. The other instruments are timer controls for the purposes of the display.
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This system is fully monitored for display and educational purposes. This adds to the total system cost and would normally not be done.
Current and historical performance data can be found here.
Cabling
The system uses cabling appropriate for the current capacity of components.
Battery cabling - uses 32 mm2 cable
Inverter Cabling - uses 25 mm2 cable |
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Automated data acquisition systems monitor the performance of this RE display system. A current snapshot of weather conditions and power flows in system 1 at the display is shown in the dials below (these dials are updated every 10 minutes - hit refresh). More detailed system performance data can be displayed and downloaded - click here.
Current conditions at the RISE Outdoor Test Area
Current System 1 Power Flows (updated every 10 minutes)
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System costs
The following table contains the costs of the various system components as at January 2002. These costs are based on the recommended retail prices of the equipment (or similar) from the Western Australian suppliers. All prices include GST.
| Unit |
Est. 2002 cost per unit |
Total component cost |
| 8 BP Solar 75 Watt panels (BP585) |
$1,100 |
$8,800 |
| D56E 5.6kVA Robin Diesel Generator, (2002 equivalent to installed unit) |
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$5,197 |
| Trace C40 Charge Controller, 24V 40 A, with optional display panel |
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$385 |
| Array Frame, Hardware and Foundation |
$850 |
$1,700 |
| Selectronics SA31 Sine Wave Inverter 2.2kW |
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$4,200 |
| Interacter Battery Charger ICS 24/25 |
$1,078 |
$2,156 |
| 4 x 6V Century Yuasa Enersun Solar Energy Batteries |
$979 |
$3916 |
| DC & AC Switchboards, Cabling and Miscellaneous Equipment |
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$2,000 |
Total System Cost |
$28,354 |
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