Engineering, Research and Development Services, LLC.

So, you've been hearing in the news how great solar panels are and you wonder if they are right for your home, business or project. Obviously, you have many questions. Hopefully by clicking on the following links you can find some answers. Also, contact EnReDs with questions on your specific applications.

What are photovoltaics (solar panels) ?
a) How do solar panels work?
b) What technologies are available?
How reliable are solar panels?
Can I afford solar panel technology?

The following sections are an attempt to help you answer these questions.
What are photovoltaics (solar panels)?
In short, photovoltaic devices turn light into electricity. Typically these devices are made into panels in large numbers in such a way that they can catch sunlight. Thus photovoltaics are more commonly known as solar panels. These solar panels are then arranged into arrays to further increase the electrical power available. The photovoltaic arrays are then combined with batteries, the electrical grid or other energy storage devices to form a photovoltaic system. Solar cells were first developed in 1954 and since then have evolved substantially. Some important principles on how photovoltaics work and a brief overview of the technologies available will be presented in this section.

How do photovoltaics work?:

Photovoltaics turn light into electricity by using the same electroluminescent phenomenon as light emitting diodes (LEDs), but in the reverse direction. In fact, solar cells are also diodes that emit electrons when light interacts with them. Solar cells are made of special materials called semiconductors. The performance of the solar cell is directly dependent on the semiconductor materials used and how they are configured. The most common semiconductor used in solar cells is silicon, although there are many other semiconductor technologies available. A specific semiconductor material and configuration will make solar cells that will generate electricity only when specific colors of light hit the device. If the light that hits the solar cell is not of the right color, the light will either pass through the solar cells without being absorbed or it will be partially absorbed by the material and generate heat. Thus the conversion efficiency of a solar cell is defined by the portion of light colors it uses from all the light colors available from the sun. Thus the many photovoltaic technologies available in the market come from the effort of making solar cells that will use as much of the sun light colors as possible. The more complex and exotic the configuration and materials the greater the conversion efficiency and price of the technology. Because of their availability, efficiency, and technological maturity, the arguments in this article will only focus around monocrystalline silicon solar panels.

What solar panel technologies are available?

A chart compiled and published by the National Renewable Energy Laboratory (NREL) explains the state of the art of the many photovoltaic technologies. In this chart the purple technologies use more complex and exotic semiconductor materials. These are the technologies used to power satellites and in comparison to other technologies they are the costliest to produce. These solar cells have the greatest energy conversion potential. The blue technologies in the chart are the popular silicon based solar cells used in most residential and commercial applications. These technologies are very close to their ideal 30% theoretical maximum efficiency, which indicates that the technology is mature. The technologies in green are thin-film technologies. This means that they are designed to be printed, deposited or glued instead of being made out of a substrate carrier material. These solar cells are physically very versatile as some of them can be flexible, others can be integrated onto substrates such as roof tiles and other yet can be produced in very large quantities. However their low conversion efficiency means that they require larger amounts of real estate to produce as much power as silicon cells. The technologies in orange are for the most part in the research stage or have been developed with very specific applications in mind.

There are many available photovoltaic technologies to choose from ENREDS can help you choose the best one for your application.

How reliable are solar panels?

The sun, solar panels, inverters, installation, batteries and the maintenance of the photovoltaic system are all factors that determine its reliability. PV systems are an investment and as any investment you want to know whether you will get the maximum power possible out of the system. Hopefully, the following questions can help you in making choices that will deliver the maximum reliability from your system.

Is the PV system in a reliable location?
The first factor to consider is the sun. Not to say that the sun is not reliable, after all it rises every morning, but the question is how much of its power gets to the panels?. It might be that the PV system is going to be at the north pole where it only gets light from the sun half of the year. Or it could be that the city where the PV system is installed is too polluted. To have a reliable PV system the first question one has to answer is, "Is the PV system going to be installed in a reliable location?." There is no simple answer to this question. Thankfully, at ENREDS we have models that can provide an idea on how reliable the location of your project is. Take for example a typical household in Salt Lake City with a 5 kilowatt monocrystalline silicon PV array connected to the electrical grid. The figure below shows the calculated energy production for such an array through out the year based on NREL data. The graph shows that during the winter months the production of the PV system sharply decreases due to its location. An important implication of this graph is that an alternate source of energy might be required in the winter for residential heating purposes. However PV power is fully available in the summer when air conditioning systems are in full force, and it is during these hot months when solar panel can provide the largest savings.

Is the PV system reliable?
A second factor to consider is of course the photovoltaic system itself. Since for the most part PV systems don't have a lot of moving parts they have the potential to last for a long time. However, PV systems have to withstand extreme temperature and environmental stresses. How well the PV system will withstand these stresses is determined by the quality of the system, the maturity of the technology being used and the maintenance given. According to NREL testing data, a 5 kW system similar to the example above should suffer about 5% decay in efficiency every decade. Typically a reputable solar panel manufacturer standard guarantee should be for at least 5 years. There are hundreds of PV system manufacturers and installers. ENREDS can design PV array systems, provide guidance in selecting good quality photovoltaic systems and suggest contractors to install them. The following figure is the calculated yearly output of the example 5 kW system.

Can I afford PV technology?
This article will use three factors to determine how affordable a PV array system can be in light of our 5 kW example system. The first factor is the out of pocket initial cost of the system. The second factor is the energy savings the systems provides. And the third factor is the value added by the system to the real estate where it is installed. For the purposes of this discussion these three factors were calculated using NREL data.
There are several costs associated with installing a photovoltaic system. The following chart summarizes most of the linearized costs of energy (LCOE) associated with installing the ideal 5 kW example photovoltaic system. Given all these costs, the example 5 kW photovoltaic system would cost about $27,670 dollars to install based on 2012 prices. Most of the costs on this graph are subject to either stay the same or most likely go up, as is the labor, taxes, fees, etc... However, the one potential cost that is projected to go down is the cost of the solar panels.

From this graph one can observe that the cost of the solar panels themselves is about 40% of the total cost of the energy. The costs for these solar panels is projected to decrease as panel manufacturing capacity increases. The following graph is the historical and projected cost of the 5 kW example system.

While the cost of the solar panels is expected to decrease, the question of whether to wait to purchase a PV system until the prices go down arises. To answer this question consider that in order to save $2,000 one would have to wait five more years. Then, the next question is, how much money can be saved during those five years if the PV system is installed now? The figure bellow shows the projected cumulative utility cost calculated using NREL data.The cumulative utility cost is the price of all the energy used in a certain period of time if it were purchased from the power company. In five years this cumulative cost is ~$740. Furthermore, the projected instant value added to the real estate where the panels are installed is almost $11,000. Not counting the fact that in five years labor costs will go up and tax incentives will go away. Investing in a PV system now might be an intelligent move. An additional point of interest in the graph bellow is that in five years the PV system would have added about $60,000 of additional property value in addition to the energy savings. And, over 30 years the PV systems would have provided over $125,000 in energy savings and close to $100,000 in added property value.