A Photovoltaic System is a system which uses Solar Modules interconnected into group or arrays and other components in order to convert light energy into electrical energy. A photovoltaic system consists of multiple components, including cells, mechanical and electrical connections, solar panels mountings and means of regulating and/or modifying the electrical output power and Inverters.
II- BRIEF HISTORY:
Solar PV Systems have been around for more than 160 years. Edmund Becquerel, a French physicist is credited with discovering the Photovoltaic Effect in 1839. Many of us remember them at the time of their most popular and foremost use; this was at the dawn of the satellite era. The need for reliable power for all of the new satellites, mostly in geosynchronous orbits, was solved by early types of PV Panels.
The installation of Solar Photovoltaic Systems as independent Generators in Puerto Rico commenced with the approval of Law No. 114 of 2007, later revised by law 221 of 2008 which mandated the Net Metering concept of electrical connection into the utility grid of Puerto Rico. Law 221 also requires that the installation of any Renewable Energy System must be Inspected and their installation must also be Certified by a Professional Electrical Engineer which also has to process a special additional license from the AAE stating his qualification as a Certified Renewable Energy Systems Engineer.
Another important piece of legislation was the approval of Law No. 248 of 2008 which established the Tax Credits as incentives for the promotion of the installation of Renewable Energy Systems in Puerto Rico. There are other laws which affect this industry as well.
The main advantage of Solar PV Systems is that, with very few exceptions, everyone has access to sunlight. This is in sharp contrast with the possible use of wind energy; good wind conditions for use as an energy source is only available at the coastlines and on very special locations where the topography and atmospheric conditions blend together in a favorable way.
The main disadvantages on Solar PV Systems are their high initial cost and the fact that they require significant areas in order to “harvest” a significant amount of energy. Nowadays, rooftops, especially on very large buildings, open areas in which farming is not their primary use and even on parking areas are being converted into large solar arrays.
This is a growing trend which is expected to continue for years to come. These cost however, can be significantly reduced when Incentives are used, read below.
Foremost is the fact that the energy produced is free and “inexhaustible”. It defers the use of burning fossil fuels, thus it is aptly named a Green Energy Source. PV systems require a minimal maintenance effort throughout their lifetime which can be above 25-30 yrs.
With the concerns on our dependency of imported oil, it’s unstable price and global warming “going solar” is a smart and sensible solution for all, It is recognized as such by the US Department of Energy and is also an indication that the individual of Legal entity which installs them as one which contributes to our overall weaning from fossil fuels and helps in lessening our overall impact into Global Warming.
Because of their high initial cost and because it has become a public policy to promote their installations, many governments , including the US Federal Agencies (especially the Department of Energy, DOE) and local governments provide means of alleviating the initial impact of these larges costs.
The main incentives are Tax Credits, these alleviate the tax burden of the User, if he has a rather large income; or they can be sold for cash in the trading markets.
There are also different programs that provide Grants or Cash Rebates for the installation of the same, the rebates usually pay for a significant fraction of the cost of the PV System.
In some states, the Utility Companies also provide special incentives for the installation of PV systems; these incentives vary from state to state.
VI- PHOTOVOLTAIC SYSTEMS IN THE U.S.A. AND PUERTO RICO:
Although not as aggressive as some of the programs in many European countries, the installation of PV Systems in the US and PR market are indeed profitable for the end users.
The main drawback is the large initial costs which must be paid at the time of the initial installation. But once these systems are installed they require minimal maintenance for their entire life which could exceed 25-30 years. Most of the solar modules carry a 20 year warranty. Thus if a viable location is found (and there are many solutions to this issue) the installation of PV Systems are nowadays a very cost worthy investment.
There are several programs that provide Grants and/or Rebates through the American Reconstruction and Recovery Program (ARRA). Even with the availability of these funds User of these systems can also receive Tax credits. Nevertheless, when these systems are installed they will provide the User free electrical energy for the life of the system.
Most of the installations of PV systems usually do not provide enough capacity for offsetting the entire electrical consumption of any installation but the bigger they are the better. If the system is large enough, then there may be excess energy that can be provided to the Utility Company that serves the electrical power to the User
In such cases, the Owner will receive cash payments (or Credits ) from the Utility Company. The amount paid back for this energy feed into the Utility Grid varies from state to state as well as in Puerto Rico. Careful life cycle cost analysis should be made in order to design and install the most cost effective system to any particular User. Since no two users are alike, there is no typical solution for all.
Each solution or installation of any PV System should “tailored” to the Client/Users needs, budget, Tax Credits/ Cash Incentives available, space available for the installations, avoidance of any shading problems by nearby structures or foliage (i.e. tall trees or buildings) are among many of the variables that need to be addressed by the professional that designs any particular system.
We have access to some of the best Photovoltaic Electrical Systems available in the market today on all types and of all sizes. Special financing arrangements can be made if so desired.
VII- SOLAR PV SYSTEMS CAN BE CONNECTED IN THREE BASIC WAYS
A.STAND -ALONE PV SYSTEMS:
A stand-alone system are not connected to any grid or utility power distribution system. Thus they need to be self sufficient for the load they serve. As mentioned before, satellites are the foremost example of them.
Here on earth, the typical applications are for providing power to remove installations where the availability of utility power would be too expensive or non-existent. Many communication systems use this type of service.
The main difference of a standalone installation and a grid tied installation is that these installations require a means of storing electrical energy, (see “Energy Storage” below)
Stand-alone systems are usually supplemented by other energy sources, such as a backup diesel fired generator and a battery storage system (see article below).
A hybrid system combines a PV System with other forms of energy generation. These can include Wind Generators, any other means of Renewable Energy Source and/or a backup generator (usually a diesel fired Gen-Set).
Many on these systems are found in islands where the conditions are favorable for both wind and solar energy systems.
These installations require devices for energy systems integration in order to allow each system to modulate or share the generated energy within their ever-changing capabilities and conditions as a function of the demand of the connected load.
C. GRID CONNECTED- NET METERED SYSTEMS:
A grid connected system is connected to a large independent grid (typically the public electricity grid) and may be able to feed power into the grid if the generating capacity is larger than the served load, or in the case of Solar Energy Farms, to supply their entire energy output to the grid.
The PV systems are usually connected to the grid under the new accepted laws which allow this connection (i.e., Net Metering) and which will compensate the User with a cash payback when they provide any excess energy into the grid.
The typical household type connections vary in size from 2 to 12 KW. Commercial type installations can be up to 10 GW while Solar Energy Farms can be much larger.
One of the typical goals in these installations is to have a “Net- Zero” power consumption, in such condition, the electrical installation is basically self sustaining and thus the utility serves as a means of storage of energy and as a backup power source when needed.
The cost of Solar PV Panels or Modules has been steadily decreasing throughout the years. The dollar cost per Watt in the 1970’s was in the range of well above $150/Watt. Nowadays the costs of large systems can be much lower than $10.00/Watt.
The cost of these panels and the Government incentives currently being provided in the USA mainland, Hawaii and Puerto Rico makes the installation of PV Systems much more affordable and attractive. Almost everybody has plenty of sunlight energy available, thus PV Systems and other solar based technologies have become available to all.
There are several technologies available in the construction of the solar modules in the present market, some of these are: Crystalline Silicon, Multicrystalline Silicon, Amorphous Silicon Thin Film, Monocrystalline Silicon, String Ribbon Crystalline Silicon, Cadmium Telluride and more.
There are many factors that need to be considered in the installation of Solar Modules. The avoidance of any possible shading caused by nearby building, large trees and even from other adjacent Solar Modules are of paramount importance. Another mayor consideration in tropical and subtropical areas that are subject to hurricanes is that the mounting scheme needs to be designed for the expected wind loads and uplift associated with these atmospheric events. Obviously other important factors are the orientation and tilt angle of the installation in order to optimize the sun rays received.
At the present moment, there is a large worldwide demand for Solar Modules. It is very important to consider the availability of the desired product with enough lead time in order to assure that the construction of any new Solar System can be performed in a timely manner.
There is no need to provide any type of energy storage in most PV installations, however, if a particular User has excess PV energy generating capacity and desires to be able to use this energy when the sunlight is no longer available (i.e., at night or on cloudy conditions) then there is a need to store such energy.
Although several technologies are available for energy storage, the use of special deep cycle solar system rated batteries is the most commonly used solution for this purpose. These batteries are designed to withstand continuous charge and discharge cycles while maintaining their rated storage capacity (there are several types of them).
Most of the batteries used at present are Lead Acid type. They can be ventilated, sealed, gel type, etc. Other batteries based on different technologies are available at premium costs; there include Nickel Cadmium and Lithium Ion type.
In order to implement batteries into a PV System, other additional equipment have to be installed, primarily is a Charge Controller. This device will maintain the batteries charged into optimal conditions (i.e., maximum power point tracking). It will also avoid excessive charging (this overheats the batteries) and monitors that adequate discharging of them, among other functions.
A group of batteries connected together in order to provide the voltage and capacity desired for any particular location is known as a battery bank.