Photovoltaic Modules (PVs), Ch. 1-4

My name is Frank E. Orzechowski and I am an Engineering Consultant, here in Polk County, Florida. Over the last three years, several folks have contacted me about the application of photovoltaic (PV) modules for their home. I have come to realize, there is substantial misinformation and confusion pertaining to the use of this solar electric technology and its benefits. Upon request, I have produced a 16-part series providing the Homeowner with the basic information, necessary to determine whether it is practical to invest in this technology. It includes calculation tools the Homeowner can use, to obtain a, fairly accurate prediction of the cost of the required equipment, along with the length of time it will take to receive a total return on their investment. Below are chapters 1-4.  I will post four chapters each week for this series. 

Photovoltaic Modules (PVs)
Chapter 1–Introduction to Photovoltaic Modules for the Home
Chapter 2–PV Application #1
Chapter 3–PV Application #2
Chapter 4–PV Application #3
Chapter 5–Understanding the Electric Bill
Chapter 6–The PV Solar Array
Chapter 7–Solar Array Cost Calculation for Application #1
Chapter 8–Solar Array Cost Calculation for Application #2
Chapter 9–Solar Array Cost Calculation for Application #3
Chapter 10–Misconceptions Concerning Government Rebates & Credits
Chapter 11–Return On Investment (R.O.I.)
Chapter 12–R.O.I. Calculation for Application #1
Chapter 13–R.O.I. Calculation for Application #2
Chapter 14–R.O.I. Calculation for Application #3
Chapter 15–R.O.I. Summary
Chapter 16–Conclusion
We are all familiar with Solar Electric Technology. Our solar powered calculators and some lighted roadway signs are examples of products which utilize photovoltaic modules to generate electricity from the sun. These modules can be combined to form a solar array which, when properly installed on the Homeowner’s roof, can generate substantial DC electricity from the incident sunlight. At that point, the DC electricity can be stored in batteries for later use or converted into usable AC Electricity, via a DC-AC Inverter device. The AC electricity can then be used for home electric use and/or returned to the local electric utility group for credit. Although, there are different technologies involved in making various PV modules, this article will focus on the one which applies to residential electric generation.
There are three applications for Solar PV arrays the average Homeowner can consider.
Each has its advantages and disadvantages. In the next chapter, we will look at the first application.
Chapter 2–PV Application #1
The first application is to purchase an array, large enough to produce all of the Homeowner’s electric needs, thus allowing the home to be, completely disconnected from the electric utility grid. In order to do this, a bank of rechargeable batteries would be required to store the electricity. It would have to have sufficient storage capacity to power appliances during the night, until it could be recharged the next day.
Advantages: There are no more electric bills from the utility company. The Homeowner would no longer be subjected to temporary loss of service, due to storms or damaged utility equipment.
Disadvantages: The cost for the equipment is high, especially for the storage batteries. For the average 3BR-2B home, the battery bank would cost between $8,000 and $10,000 alone and would have to be replaced in 10 years or less. In addition, the array would require a large number of individual modules to meet the electric needs of the home. Should the array require maintenance, encounter malfunctions or function below specifications, the Homeowner would be without electricity unless, a backup generator was available. Most Backup Units have limited power capabilities.
In the next chapter we will look at the second application for a PV array.
Chapter 3–PV Application #2
The second application is to purchase an array large enough to produce all of the Homeowner’s needs, but without the battery bank. It would require a bidirectional meter, supplied by the electric utility. A bidirectional meter allows electricity to flow in two directions. When you are using electricity from the utility, it flows in the direction of the home. When the solar array is generating more electricity than the Homeowner is using, the excess electricity flows in the direction of the utility’s grid.
Advantages: Because the Homeowner remains connected to the electric utility, electricity will continue to be available, 24 hours a day, should the solar array stop producing the required output. If more electricity is generated by the solar array than used by the home during the daylight hours, the bidirectional meter will allow the excess electricity to be returned to the electric utility. In return, the electric utility will provide the Homeowner with electricity credits which can be used any time in the future. Think of this credit as “rollover minutes”, as applied to the telephone industry. Instead, we call them “rollover kilowatt-hours”. The main advantage is the Homeowner does not need the battery bank. The electric utility will serve as the source to return excess electricity. This eliminates the investment cost in a battery bank.
Disadvantages: Regardless of whether the Homeowner sends more electricity back to the utility than the home is using, the Homeowner will continue to receive a monthly electric bill, containing a customer service charge. This charge covers the utility’s cost of operation and service provision and will undoubtedly, increase over time.
In addition, it should be noted the utility is not responsible for the Homeowner’s solar equipment. The bidirectional meter is the only equipment they are responsible for at the home. Most Homeowners are unaware they will be required to sign a document called an “Interconnect Agreement”. For several electric utilities, this agreement requires the Homeowner to pay an interconnect fee and carry $1,000,000.00 of Homeowner’s Liability Insurance on the home. An array, capable of supplying enough power to meet the total needs of a typical 3BR-2B home, 24 hours per day, will incur this cost.
In the next chapter we will look at the third application for a PV array.
Chapter 4–PV Application #3
The third application is to purchase an array, just large enough to generate some of the electricity used by the homeowner, but not all. If the array is large enough, it can meet the daylight hour’s electrical needs and return any extra available electricity to the utility grid, during the peak sunlight hours of the day. Of course, this will continue to require permanent connection with the local electric utility. How big the array should be depends upon how much the Homeowner can afford, what percentage of the monthly electric usage needs to be recovered and what amount of electricity is desired to be sent back to the electric utility for future credit. Only the Homeowner can decide this.
Advantages: A smaller array costs less and takes up less roof space. This would allow more installation room for other forms of solar equipment such as solar panels for the home’s hot water tank or swimming pool heating applications. Most of the time, a smaller array will fall into the category where the electric utility’s “Interconnection Agreement” will not require any fees for installing their bidirectional meter or the supplemental homeowners insurance.
Disadvantages: The Homeowner will be required to pay the monthly customer service charge. Because the solar array contains less modules, less electricity is generated. This implies less “rollover kilowatt hours” credit is available. Although, the equipment cost is less, in the long run, as electricity costs more, the over all value of the system will decrease because it is generating a fraction of the home’s overall electric needs.
Now that the Homeowner has a general view of the available applications, let’s discuss how to determine which application is best for their home. To accomplish this, we need to first, understand some of the nomenclature of a typical electric bill. In the next chapter, we will learn how to use some important information from a typical electric bill.