On July 2019, we will be making a 1 kilowatt solar power project to power a 4 hectare farm located in a mountainous forested land where power from the grid is not available. The project is part of the 2 Kilowatt Power goal we are going to achieve. The entire farm will be powered by a 1 kilowatt solar power and a 1 kilowatt hydro power. The project would require four solar panels, power bank, a homemade Pelton wheel, charge controllers, an off grid, pure sine, power inverter, dc breakers, connectors and cables. I will only feature here the solar power installation.
Like in the previous post about a 4 kilowatt uninterruptible power supply project, the setup is a 48 volt direct current system. So four batteries (12 volt each) are connected in series to form 48 volt bank. Each battery has 200AH energy storage capacity. A 48 volt MPPT charge controller to charge the battery bank, four solar panels (250 watts each) connected in series as the source of power, and a 3 kilowatt pure sine wave power inverter with 48 volt dc input and 220 volts ac/60 hertz output to run a load, are the primary connections of the circuitry. Below image shows a block diagram of both solar and hydro power of the project.
Solar panels of monocrystalline type would be used in the project. Each rated 250 watts with up to 40 % efficiency at full sunlight and proper ventilation. We may cut down some trees for this project to avoid shading. A small shading on the solar panels can drop the power output of the entire array to 80-95 %. The advantage of higher dc operating voltage over the lower one is it requires smaller cable size to reach a certain power output. The higher the voltage, the lower the current in the circuit, so the smaller and colder the cable is.
Deep cycle lead-acid batteries are to be used to create a power bank. Each battery has 12 volts and 200 AH energy storage capacity. They are also connected in series to form a 48 volt bank.
The charge controller must be MPPT (Maximum Power Point Tracker) and can handle 48 volts and 30 amperes to charge the power bank. The image below shows an example of a MPPT charge controller. Depending on the manufacturers, some charge controllers show different looks. Usually it has terminals for solar or any dc source, batteries, and controlled output, led indicators for charging and battery level, work mode preset button and control keys.
DC switches sometimes called isolators or dc breakers should be connected in between solar panels and charge controller, between charge controller and batteries, and between batteries and power inverter. Most dc switches comes with built in protection fuses and high voltage bypass and dc blocking capacitors. Fuses will protect the circuit from overloading and bypass capacitors will protect switch contacts from high voltage sparks. The switches should be 30 ampere at least. they can be single pole or double pole type. Depending on the manufacturer, sometimes dc switch comes with a reset button.
Battery and inverter input cables should have a minimum ampacity of 30 amperes. The best terminal lugs are made of copper for better conductivity and produce less heat compare to terminal lugs made of zinc, antimony or steel alloys. Provide also cable color coding for the circuitry. Usually in direct current circuity, red is used to indicate postive terminals of batteries, input terminals of dc devices and dc cables. Black is the best color to indicate negative of direct current circuits. But for solar panel cables, like the MC4 cables, both positive and negative are of color black. Only the MC4 terminals and connectors will indicate the polarity of the circuits. You may even use a polarity tracker or a multitester to indicate the polarity.
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A pure sine wave power inverter should be used in the circuit. Pure sine wave inverters provide the same alternating current wave form like from the mains power supply. It has working frequency of 50 to 60 hertz which most appliances or lighting devices run at. There is also another type of inverters that provide modified sine wave alternating current. They are much cheaper but not recommended to power on most loads. Modified sine wave can destroy induction motors like from the electric fans, ceiling fans and ac motor pumps. It produces humming sounds in most devices that run from converted ac input to dc output circuits. It can damage also some dc circuit as well. There are also three types of inverter according to output connectivity. We have the off-grid inverter where its output is independent from the grid power source, the grid-tied inverter which the output can be synchronized with the mains voltage and frequency and the hybrid off-grid and grid tied inverter which can work independently or grid tied. On this project, since access to power from the mains is not available, we are going to install an off-grid type of inverter. An off-grid inverter has fixed dc voltage input and an independent 110 or 220 volt/ 50 to 60 Hertz output. This project would use 48 vdc to 220v ac conversion inverter.
The AC output would be transmitted through THHN 8.0 mm2 cables. The solar station is made up of steel angular bars, 2 inches diameter Galvanized Iron pipes as columns, concrete flooring up to 30 centimeters thick, a rear wall that can be made of plaster or concrete, conduits and an entrance cap for distributing AC power to the loads. A 3/4 LB connector and entrance cap is mounted at the upper center of the rear wall. The roof can be a corrugated or any type witch 30 degrees angle slope.
The image below shows the entire circuit diagram of solar power project.
All dc switches and power inverter should be at "OFF" mode before installing and operating the solar power circuitry. You must follow a switching sequence to start or stop a solar power operation.
Starting a solar power generation:
1. Turn on dc switch connected between the charge controller and batteries.
2. Turn on dc switch connected between the charge controller and solar panels.
3. Turn on dc switch connected between the batteries and the power inverter.
4. Switch on the power inverter switch.
5. Connect the loads. It is better also to test the output with multitester before plugging a load.
Stopping a solar power generation:
Switch off all the switches by reversing the above steps.
The solar power, along with the hydro power project, is expected to power a station house with interior lighting, water heater, radio and television receivers, farm perimeter and block lighting, internet modem with wireless LTE connection, laptops and mobile devices.
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