Our Simple DIY Home Solar Power System
This basic off-grid solar power system is simple to install and can be easily expanded…
By Greg Seaman,
Eartheasy.com Posted Jul 18, 2012
Our basic solar powered energy system provides more electricity than we expected, it has been very reliable and maintenance-free, and it is almost entirely hidden from view. A solar panel on the roof with a few wires leading to a small battery bank powers my laptop, and a radio mounted on a tree for receiving the wireless broadband signal. The system also provides enough energy to charge several small power tools, run our home sound system and, amazingly, power a full-size chest refrigerator year round.
Our simple home solar power system is comprised of four basic components: a solar panel, a charge controller, two 6-volt golf cart batteries and a small inverter. My son and I were able to install the system in a few hours, and there have been no maintenance issues other than checking the fluid level in the batteries every few months. The cost of this complete solar system, in today’s pricing for the components, was less than $1000.
The cost of this complete solar system, in today’s pricing for the components, was less than $1000.
We have already enjoyed about three years of trouble-free use from this system. The refrigerator has not been off for over two years, which is pretty impressive considering we live in the Pacific Northwest where the short winter daylight hours provide minimal solar exposure for the panel.
The basic components of this off grid solar power system are as follows:
1. Solar panel
We have a single solar panel mounted on the roof of our home: a 123 watt Sharp Photovoltaic Module, model 123UJF. The panel is equipped with a permanently attached junction box for ease of installation of wires and conduit. Two boards are lag screwed into the roof and the solar panel is bolted to the boards using wing nuts, so it’s easy to lift if maintenance is required. The panel surface is about 5” above the roof surface. The panel is hinged to the mounting board, which allows the panel to be tilted towards the sun, and to increase ventilation. We plan on adding a cog/string system to make it easier to tilt the solar panel towards the sun from the ground. Two wires run from the solar panel, one is the power line and the other is a ground line. The power line runs down the roof to the charge controller, where there is a fuse. A box on the porch which houses the charge controller, inverter and batteries. The ground wire runs beneath the house and is attached to a rod which is driven about two feet into the earth.
It should be noted that the panel guidelines state that the installation of PV modules requires a “great degree of skill and should only be performed by qualified licensed professionals, including licensed contractors and licensed electricians.”
We installed our system ourselves because our supplier, who is a licensed installer, gave us explicit directions and came by to inspect the installation after it was done. We suggest that you follow the recommendation as stated in the module instructions with regard to installation.
You may notice there is a shadow on the panel being installed in the picture above. This shadow crosses the panel in about 20 minutes, so there is a small loss of efficiency over the course of a day. But we live in a beautiful forested area and I value the tress more than 100% efficiency in solar gain. If there were a major solar loss I might top the tree, but our system provides for our needs and so we will live with the shadow, for now at least.
The cost of the solar panel in today’s pricing is about $425.
2. Charge Controller
We use a Trace C12 Charge Controller which automatically adjusts the amount of power running into the battery. The controller has a small LED light which indicates the state of charge so it’s easy to see when the batteries are fully charged or if they are becoming depleted. The light flashes either red or green, with multiple flashes indicating the status of charge at any given time. We can see that if the light is red we should reduce our power use, and if the light is green then we have the power needed to charge or run additional devices.
The cost of the Trace Charge Controller is about $90.
3. Battery Bank
Two 6-volt golf cart batteries are wired in series for a 12 volt system. Each battery is rated at 232 amp hours. The batteries are enclosed in a wooden chest with hinged lid, and the top panel of the chest is removed to provide plenty of ventilation. The battery posts and connections are kept clean, and periodically checked to ensure good connections.
The cost for the two batteries was about $400.
The final piece of the system is a small inverter which converts the 12 volt DC power into 120 volt AC power. This enables us to use standard electric devices without the need for adaptors. Inverters are available in a wide range of wattages for different size systems. Ours is a small inverter made by Nexxtech, rated at 300 watts, with a 500 watt surge capacity. It comes with two cables, red and black, with alligator clip ends for gripping to the battery posts. In choosing which size inverter to buy, we calculated how much power was available to our system and what devices we wanted to run. In calculating power needs, it is important to add the power requirements when two or more devices are running simultaneously.
Our Nexxtech 300 watt inverter cost about $30.
What this system provides:
An alternative energy system can be used to provide electric power to any number of electric devices, such as appliances, tools and computers. The bigger the system, obviously, the more power it will provide. To give you an idea of the capacity of a small system like ours, here is what we use our solar energy system to power:
This is a DC powered refrigerator, the same size as a conventional chest freezer (4’ wide). The refrigerator draws 40 watts of power and can be converted to a freezer by replacing the thermostat. Since the refrigerator is a DC model, it is wired directly to the battery, bypassing the inverter. So the refrigerator keeps running even if the inverter is turned off. Our refrigerator has been running continuously for over 2 years without any problems. Even during the dark days of winter, the unit has adequate power to keep running.
This is our Vers sound system which lets us use an iPod or direct cable from an iPhone or computer to deliver a rich sound while drawing relatively little power. We can run this sound system about 3 hours a day in winter, and as much as we want in summer.
Our solar system provides adequate power to run a laptop computer all day if necessary. We also run a router from our inverter so that multiple computers can be operated at the same time. In addition to the router, a small radio is installed on a tree about 300’ from our house which receives the wireless broadband and transmits the signal to the house.
Besides the laptop, we have a battery-powered driver-drill, which is a very useful tool. Our system recharges the battery for this tool in about 30 minutes.
These are the principle applications we use which are provided by the solar power system described above. However, you can use a wide variety of electric devices as needed. Today, we enjoy the benefits of our system without feeling a technological intrusion into our off-grid homestead and lifestyle. The refrigerator especially has made a big improvement in our day to day living, since storing food is so much easier. Over time we may expand our system by adding more batteries for storage, and eventually a second solar panel or small wind turbine.
Bringing electricity to rural locations is something of a balancing act since we don’t want our simple lifestyle changed by too many electrical gadgets. It does require some restraint to keep things simple, but the few electric amenities we now have are most appreciated!
Originally from Long Island, NY, Greg Seaman founded Eartheasy in 2000 out of concern for the environment and a desire to help others live more sustainably. As Editor, Greg combines his upbringing in the cities of New York, Boston and San Francisco with the contrast of 31 years of living ‘off-grid’ to give us a balanced perspective on sustainable living. Greg spends his free time gardening, working on his home and building a wooden sailboat with hand tools.
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