Continuing on from my last article on solar water heating and being green, this article will be the first article about generating your own electrical power. There are a few ways to generate your own power, for example: wind, thermal transfer/steam generator, wave energy, hydro and photovoltaic (PV).  However some of the choices are only economical for businesses or a group of homes who may want to share a system. Also wind, hydro or waves power are only available to those in the limited locations.  For the most home owners, PV is the best choice.  It’s silent and can be in most cases blended in with your home roof so that it is barely noticeable.  In Hawaii where the sun shines at least 300 days a year and with a PV system facing the optimal direction, you can get at least five hours per day of good electrical production.

Generating your own home electrical power makes a lot sense.  Hawaii has one of the highest utility cost in the United States due to its location and with oil prices rising, the cost will continue to escalate (since 1990, on average electric prices have gone up by 6.6% per year per U.S. Energy Administration).  If you pay a lot taxes, this can help you save money and use some of what you normally pay to Uncle Sam.  With the Federal tax credit of 35% and the State tax credit of 35% (There is a cap of $5,000 per year per system), most systems can be paid for in 7-8 years.   There are even better incentives for businesses but I won’t be covering that in this article.  For a complete list of other incentives for Hawaii go to:  http://www.dsireusa.org/incentives/homeowner.cfm?state=HI&re=1&ee=1

Reducing our dependency on fossil fuels and saving the environment for our kids are also great benefits from using a PV System.  By using a single PV System instead of using commercial fossil fuel generation, 20,000 lbs of Carbon Dioxide, 60 lbs of Sulfur Dioxide and 25 lbs of Nitrogen Oxides can be avoided per year.  This would be equivalent to planting over 1,500 trees or reducing your driving by 24,000 miles per year.

"Making electricity from the sun …. Cleaner than burning fossil fuel coal … total Awesomeness!” Quote from Jolene Akasaki a student at Punahou School.

So what makes up a PV System?  The main components are the PV panels, an inverter to convert the power coming out of the panels (direct current - DC) to the kind of power which our houses are wired for (alternating current – AC) and a control/monitoring system.  

PV System Diagram from BNP.Org

A typical PV panel currently produce 10 watts per square foot. The panel is approximately 3 feet by 5 feet in size and weighs between 40-50 pounds. A single panel can produce between 170 and 230 watts of power. An average home (assuming that it has a solar water heating system) needs about 20-30 panels which will take approximately 400-600 square feet of roof space.  Prices for PV panels have gone down 30% in the last couple of years because silicon prices are down due to lower demand by integrated circuit makers. Additionally, a PV system will increase the value of your home, and keep your roof and house cooler which make which will make it last longer. The PV panels have a warranty for 25 years but are expected to last far longer.

For an interactive explanation of a PV system click on the diagram below which will take you to the Sharp.com site.

The other two main components of the PV System are the inverter and the control panel. There are two main types of inverters: ones that handle a string of PV panels (i.e. 2,000-6,000 watts) or a micro-inverter which handles only one PV panel.  The larger inverter is the conventional method but micro-inverters can be more efficient but have not been proven since they are still relatively new.  The inverters are warranty for 10-15 years and therefore may need to be replaced before the PV panels.  However, like most technologies, inverters will be improved over time.

Lastly there is a control system which monitors the performance of the system.  These systems are usually connected back to a service which can alert you if anything is going wrong with your system and can provide you with a report of the amount of electricity you are producing.

Commonly now, PV Systems are tied in with the existing electrical system of the home and therefore connected to the commercial electrical utility provider.  There are no batteries to store power generated for use later in this type of on the grid system.  Only in totally separate off the grid systems (e.g. very rural or remote locations), are batteries required.  This on the grid type of system saves the owner from having expensive batteries which need to be maintained and replaced periodically.  In this kind of system, a method called Net Metering is used. The power company gives the home owner credit for their extra power which the home owner can draw upon when they need it (e.g. in the night when there is no sunlight for the PV System to generate electricity).  In other words, the power meter is running in reverse and the power company acts like the home owners battery.  This can be a win-win for the home owner who is getting credit for their excess power and for the power company who can use the excess power for other customers and possibly defer building additional power plants to cover peak power usage.

For the average PV system, the cost is about $30,000.  For a system of that cost, you would get a $9,000 Federal tax credit and $5,000 State credit which adds up to $14,000.  The remaining $16,000 needs to be paid back by your saving in electricity bill.  If your current bill is $200 per month and you assume a 5% increase in cost per year, the payback period is approximately 6-7 years.  Since the system is anticipated to last up 40 years, you should be saving money as well saving the environment for decades.  Even if you don't have the cash to pay for a PV System, the monthly payment for a home equity loan can be paid for with the savings from your utility payment.  This will extend your payback period but it will still be shorter than the life of the PV System. For quick analysis of your home situation go to http://sharpusa.cleanpowerestimator.com/sharpusa.htm and type in your monthly electric bill and zip code.

You can do yourself (http://www.builditsolar.com/Projects/PV/pv.htm#Tracking) but I suggest finding a reputable contractor who can give you the optimum return for your money and roof space.

I am currently having a system installed at my home by Green Path Technologies and I will be providing future articles on the installation and operations of my PV System. I also would like to acknowledge and thank Charles Chacko of the Photovoltaic Division of Commercial Roofing & Waterproofing Hawaii Inc. for his help on this article.