An off-grid power system is a stand alone system - it operates completely on its own to supply all of your power needs. The cost of such a system can be less than bringing in power if you live in an area where it's expensive to bring in utilities. We chose an off-grid solar and wind power system for our own home because it would cost over $10,000 to bring power to our home.
An Off-Grid Renewable Energy System
An off-grid system consists of five basic components:
- A solar array, wind turbine or both to produce power
- A bank of deep cycle batteries to store energy for overnight and cloudy or calm days
- A charge controller to regulate and prevent overcharging fof the batteries
- An inverter to convert DC power to 110V or 220V AC household power
- A backup generator to recharge the batteries during extended cloudy or calm periods
The cost of an off-grid system depends on how much energy you use. To produce more energy you will need a larger solar array. A wind turbine can provide additional power.
Keeping the System Affordable - Using Less Energy
An off-grid system can be a costly investment. Costs can run anywhere from $15,000 to $60,000 or more, depending on what you want, but the fuel is free and there will be no utility bills after the initial outlay. You can cut down considerably on the size - and cost - of the system by figuring out how to use less power and still do all the things that you want. This is not as difficult as you might think. You can cut your energy needs substantially by simply shutting things off, such as the lights, the computer and the TV, when you are not using them. If you are not getting any benefits by leaving them on, why pay for the power?
To save money on the upfront costs of the system, figure out what you really need by doing a load analysis - a list of all appliances you will use and the amount of energy that they will require. This will show you not only how much energy your current lifestyle would require but also where you can save power.
Home heating is one of the big challenges in northern climates because of the large energy usage of most heating systems. One way to see huge savings on heating is with passive solar home design. In very cold climates you will need some source of heating fuel such as natural gas, propane or wood. It is simply not practical to use electric heating with an off-grid system because this uses a very large amount of energy at a time of year when you are producing very little. Propane or natural gas is also a good choice for a cookstove, clothes dryer and water heater which are large users of electricity and usually require a 240V system.
Storage Capacity and Maintenance
One of the challenges of living on an off-grid system is that it has a limited amount of storage capacity in its battery bank. The batteries can only store power for a few days - when your battery bank is full the extra power is lost unless you can use it immediately. This is a really good example of making hay when the sun shines - when you have lots of power it's time to do the laundry or the vacuuming or use the electric frying pan to cook supper. It would be great if you could store that energy over longer periods for the lean times but there is no such practical technology available for this yet. Supersizing your battery bank is generally too costly to be feasible. It is more economical to start your backup generator once in while when you need more power than is available.
Battery banks and backup generators both require regular maintenance and have a shorter lifetime (12-15 years) than the solar panels (35 years or more) and wind generator (20-25 years). The backup generator also requires fuel - gasoline, diesel, natural gas or propane.
Know More About Your House - Monitoring
One of the fascinating things about having your own power system is that you are always monitoring it and can see what you are producing and using. It almost becomes an obsession to check this and take pride in living within the limits of what you produce.
We have given many tours of our off-grid house to show people how it works. One of our meters shows the electric current that is going from our solar and wind system into the batteries. I show people the meter and then I will start our toaster. Instantly the meter goes from, let's say, +10 Amps (it's charging the batteries) down to -35 Amps (drawing from the batteries)! That's how much power the toaster is using. It's a quick and simple demonstration but also shows that you can see what is going on with your house - something you simply don't see in a regular grid powered home. I often tell people it's just like having a big toy.
Self-Sufficiency on a Clean, Renewable Resource - a Good Feeling
There is a real feeling of independence and accomplishment that comes with being self-sufficient. We live on an acreage and also have our own well, septic system and a wood stove for heating. We use propane for cooking, hot water and a small backup heater. This is our only utility expense. If the power goes out around us we don't even know it - our lights stay on! One of the things we love about our off-grid home is that almost everything we are doing is operated from clean and renewable energy. It gives one such a positive feeling.
Sources:
Energy Solutions Centre, Living Off-grid in the Yukon: Efficient renewable energy use and practices, National Resources Canada and the Energy Solutions Centre, April 2005.
RETScreen International, http://www.retscreen.net, "Clean Energy Project Analysis".
L. Zanasi, "Off-Grid Residential Energy Use Survey - Main Residences", Yukon Bureau of Statistics, Nov. 19, 2003.
Angelika Ortlepp - Angelika is a professional engineer specializing in renewable energy, passive solar design and technical writing.
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