How Home Solar Photovoltaic PV Works
How Home Solar Photovoltaic (PV) Works
Interested in a small solar photovoltaic (PV) project for your home, cottage or camp ground? Here’s a quick overview of how it works and how to setup your own small solar PV system.
Solar PV vs Solar Thermal
Solar Photovoltaic systems use sunlight to produce electricity. You can then use that electricity to power your electrical devices. Solar Thermal systems use sunlight to heat water. This hot water is then used for hot water in your home and call also be used to produce heat for your home. On a larger scale, you can also use a solar thermal collector to produce steam to run a generator to make electricity… but these systems are not seen in “home use”.
Solar PV Components
The basic components of a solar PV system include: solar panel, inverter, wiring and fuses and a storage device. If the storage device is the electrical grid, you don’t need to add much else, other than a disconnect switch. If your storage device is batteries, you need to add those batteries and a charge controller.
Design A Small Solar PV System
Let’s build a very small, very simple system for an off-grid cottage/camp. This system will power a few lights (CFL or LED) and a small stereo for the weekend, after charging up during the week.
First, consider the load that you will power – lights and stereo. Add up the total watts of the light bulbs and the small stereo. Consider how many lights are likely to be ON at one time. Next consider how many hours the lights and stereo will be on, during the weekend. Let’s say we will have 3 lights on, for 6 hours each, during Friday, Saturday and Sunday. Our CFL lights are 9 watts each. Thus power for the lights is 9 x 3 x 6 x 3 = 486 watt hours for the 3 day weekend (324 watts hours for 2 days only). Next the stereo – let’s say you are using a car stereo system for you music. Let’s also say the average car stereo has an RMS wattage of 25 watts. You have the stereo running for an average of 8 hours per day for 3 days. Stereo load = 25 x 8 x3 = 600 watt hours. Your total load for the weekend is therefore 486 + 600 = 1,086 watt hours.
We need to produce at least 1,086 watt hours of power during the 4 days you are not using the system.
If we assume that your location gets an average of 4 hours of sunlight per day and you have 4 days to produce power, then you have a total of 16 hours of sunlight to work with. Dividing the power we need (1,086) by the hours we have (16) we find that we need to produce (1,086/16) 68 watts of power per hour.
We need an 85 watt solar panel to produce our 68 watts of power per hour, due to the losses created in our inverter, controller and batteries. This a a 20% loss in efficiency and is fairly average for a small PV system.
Small System Components
This system will start with an 85 watt Solar Panel. You can also use a combination of solar panels that add up to 85 watts.
The wire runs from the rooftop mounted panel, down to the Charge Controller. The charge controller monitors your battery charge and allows the solar panel to charge up the battery if needed. If the battery is fully charged, the charge controller disconnects the solar panel. Solar systems use a very simple and inexpensive charge controller. You can find a small charge controller of this system, for $30. Don’t get a charge controller used for WIND TURBINES, as they use Dump Loads and more circuitry that costs money…and your solar systems doesn’t use these features.
Next we have the battery. Use a deep discharge battery that is made for marine or solar use. A deep discharge battery can be drained of power and still be recharged. A standard car battery will not last very long if you keep discharging it.
Next, we connect the Inverter. Our stereo draws 25 watts but we will connect it directly to the battery as it operates at 12 volts DC. Our 3 lights only draw 27 watts We can therefore get by with a very small and inexpensive 100 watt inverter. You can likely find one of these small inverters on sale for $20.
The lights can be plugged into the inverter. As mentioned above, we’ll wire the stereo directly to the battery. I like to add and on/off switch into this circuit as some stereos might draw power even when turned off. And of course, you need to added fuses. Add a DC fuse to the line from the solar panel to the charge controller. Add another DC fuse to the stereo (there may be one in the stereo already). And add regular household fuses to your lights.
Next Steps
That’s your basic small solar PV system design. Need more power? Add more panels and more batteries. If you plan to expand in stages, you may want to start with a larger charge controller and inverter, so you don’t need to replace these items as you expand. Enjoy.
Similar Posts:
Filed under: solar
