PRACTICAL INFORMATION ABOUT SOLAR ENERGY
We all know that fossil fuels are limited in supply, but how long exactly will they last? Well, no matter what anybody claims, to be exact, no one can know for sure. Some kind of estimation is provided by so-called reserves-to-production ratio
. For example, it is currently considered that global R/P for oil is about 50 years. However, this number is being corrected every year because of two opposite trends. On one hand, we are constantly finding new reserves. On the other hand, world electricity usage keeps increasing too. If current trends continue, it will more than double by the middle of this century. So, we may be out of traditional energy sources sooner than we think. Early or later, their reserves of course will fall short of demand. This fact coupled with erosion of our energy security and generally rising electricity rates are probably the main reasons of increasing interest in solar energy. We realize we can rely on it because it is something that will always be there. Naturally, many homeowners are considering using sunlight both for financial reasons and to help the environment. Unfortunately, there is a lot of misunderstanding and hype
concerning solar energy.
Particularly, the way the advertised capacity of commercial photovoltaic (PV) systems is specified may be misleading
to the consumers (I'll discuss it here
). In addition to this, the manufacturers often use terminology that is confusing to most who do not have a technical background. As a result, making a decision on selecting and buying the right PV powered system can be challenging. For example, one may not realize that a nameplate rating of such a system does not really represent the wattage it would typically produce in your home. Usually it is just a potential peak DC power
the PV array can generate at some ideal sunlight and weather conditions called Standard Test Conditions (STC). In practice, your panels
will operate at STC very rarely. In addition to this, the actual AC output of the entire system will be 10 to 20% lower than its DC rating due to power losses in the inverter and wiring. Finally, for solar systems it is not only the wattage, but kilowatt-hours that matters. Let's consider a typical example
. Suppose you estimated that your home requires 5,000 watt power. One might think you would need therefore a 5-kW model. In reality, such a model may probably generate less than 20 kilowatt-hours of electricity over an entire day, which is less than 830 watt averaged over a 24-hour period.
Many consumers are under the impression that for a couple hundred dollars they can install a small panel that will provide all or most of energy for their home and even sell an excess of electricity back to the utility. The sunlight of course is free, but the equipment needed to capture it and convert it into a usable form is not. Right now in many states there are programs with free installation. Of course, the capital cost does not go away-- I understand the companies that install PV systems for free get federal and state incentives, so the costs are partially passed onto taxpayers. Then you will have to pay the solar company for the next 20-25 years for all electricity their system generates. Normally, they set the starting $/kWh slightly below your utility rate, so you do save, at least at the beginning. However, the fine print in the contract usually states that the saving is not guaranteed. So, just because something looks appealing or is advertised as a solution for all your energy needs, it does not mean that it is necessarily right for your application. In order to make an informed decision about investing in solar energy, you may want to know at least in general how it works, exactly how many kWh it can produce in your installation, and calculate the required amount of the panels you need. If you pay for the system you also want to determine how long it is expected to take to pay back the initial cost.
If you search the web for these subjects, you'll find literally millions of results. Why did I decide to make another website about it? I feel although most of solar energy facts and figures are already available on the web, they are so scattered that it is not always easy to quickly find what you are looking for. In addition, sometimes it can be hard to distinguish between advertising and objective material. With this in mind, this site is designed as a concise guide for anyone who wants quick practical
data. The information here is divided into two types: the scientific facts about solar energy and the data about the devices that capture sunlight and convert it into usable energy forms. This information is intended to give you realistic expectations of what you are getting and how much electricity the system can generate in your home.
REFERENCES AND ADDITIONAL INFORMATION:
Solar energy facts
FACTS AND FIGURES.
Near the equator the sunlight intensity at bright noon is about 1000W per square meter. Elsewhere this value is always lower. Find out how much sunlight you get in your geographical area, how many watts can be generated per unit area, and other practical facts about solar energy. Read more.
UNDERSTANDING SOLAR POWER PANELS.
Electric energy can be produced from incoming sunlight by PV cells. Each cell can generate less than 700 millivolts. To get usable voltage levels many cells are connected into panels. Discover how the panels are made, how they work, and what you need to know about their advertised characteristics. Read more.
PHOTOVOLTAIC SYSTEM WIRING.
A typical commercial PV module is rated under 300 watt. To produce higher power levels a number of modules have to be electrically interconnected into an array. This page provides formulas and diagrams for series and parallel connections, as well as NEC® 2014 requirements for code-compliant wiring. Read more.
Different panels will produce different output under the same conditions. For a given setup, the output wattage depends on the cells efficiency, which refers to a fraction of incoming sunlight they can convert to electricity. See efficiency data of the best solar panels and 2014 rating chart. Read more.
To install a PV system in your home you may need to obtain appropriate permits and pass the inspections after the work is done. See the list of main standards and codes that may be applicable to your setup and get tips for the system installation. Read more.
The required size of PV array depends on a number factors, such as your geographical location and orientation of your roof. Learn how to size your PV generator and calculate how many modules do you need for your home. Read more
: outlook and research.
Photovoltaic technology white paper
: status and trends.