Home Energy Focus

Archive for March, 2010

When your alternative energy system generates electricity, you can’t use it directly to power your home. The power itself is too dirty and requires conditioning and possibly storage before it can be used. There are many components to your power system beyond just the generator and batteries. You need a charge controller and an inverter to make sure your system is running smoothly.

As the power enters your charge controller, it changes the characteristics of the electricity so that the charge doesn’t damage the batteries while it charges them. Sizing your charge controller (or charge controllers) is important for the efficiency of your system. If you have 200-watts of generating capacity and have a 2000-watt charge controller, you’re wasting capacity and may be losing efficiency. This issue is less critical on the inverter end as excess capacity there can always be used.

Your batteries themselves need to be considered when you’re designing your system. Batteries are fickle and can be very easily damaged with improper care. Many DIYers use car batteries for theri solar or wind power systems, however this may not be the best choice. These batteries are designed to be lightly discharged and then recharged again, however renewable energy systems need batteries which are less likely to be damaged when fully discharged.

Some important points to consider when determining which batteries are best for your system:

• Does my system include only solar, only wind or a combination of the two
• How long must the battery bank supply power to your house
• How much power can the charge controller and renewable sources supply
• Will the battery bank be discharged or fully charged for extended periods (cottage, summer home, RV, etc.)
• Do you ever want to expand your power system

Not all “deep-cycle” batteries are created equal.  Even though some batteries may be labeled as “deep-cycle” that doesn’t mean that they are suitable for solar power systems.  In another article, we’ll discuss different types of batteries and their uses for solar systems.

When you first think about building your home alternative energy system, you need to make a few decisions.  The first thing you need to know is how much power you consume on a regular basis.  There are several ways to figure this out, the easiest being, look at your electricity bill.

Electricity is sold by the kilowatt-hour.  One kilowatt hour is about the equivalent of running 4 desktop computers for one hour.  When you look at power generation systems, they come with several ratings.  The two important ones are power in watts and voltage in volts.  If the generation system that you are considering buying does not output 120V 60Hz power, then you will need some sort of inverter or transformer to make the power usable in your home.

Let’s back away from the technical talk for a minute and talk about wind turbines and solar panels.  When you look at wind turbines for you home, there are several things to consider.  First, does your area get a significant amount of wind?  This can be found through a quick search and the Department of Energy or the Ministry of Natural Resources (Canada) will have this information.

Next, you need to assess how much room you have to locate the turbine.  The closer it is to obstacles, the higher up the turbine needs to be to operate efficiently.  Any turbulence will strongly affect the power generation of the wind turbine.  This, of course, is also a function of the type of turbine.  Traditional horizontal axis wind turbines are less efficient in turbulence than vertical axis wind turbines (VAWTs).  VAWTs are actually quite well suited to urban and other turbulent environments.

If you are looking at a solar-based system, the average amount of sunlight that your area gets per year is available from groups such as ASHRAE and also the Department of Energy and Ministry of Natural Resources mentioned above.  The sun imparts about 1400 watts of power per square meter of area on the ground.  Obviously this is only when it is directly overhead and the light has the least atmosphere to travel through.  As the sun is lower on the horizon, the amount of energy that reaches the surface will decrease.

Solar panels are greatly affected by contamination such as rain, snow, ice or dirt.  It is important that for maximum generating capacity, the solar panels be kept very clean.  Remember, they are converting a relatively small amount of that 1400 watts to usable electricity and we want to squeeze every watt out of them that we can.

Other components you need to consider include storage and distribution systems which we’ll talk about in a later article.