Source: www.going-electric.org

Many studies by various consulting companies provide forecasts for the sales of Electric Vehicle (EV), especially electric cars, in the coming decades.

Most forecasts include Battery Electric Vehicles (BEVs), Plug-in Hybrid Electric Vehicles (PHEVs) and Fuel Cell Electric Vehicles (FCEV). The most pessimistic ones predict that, by 2020, the sales of electric cars will reach 3% of all new cars, while the most optimistic predict around 15%. As shown in the graph below, studies usually forecast that EV sales will increase in a linear fashion for decades.

Going-Electric makes no prediction regarding electric car sales in 2020, because it will largely depend on the incentives that public authorities will provide to electric car manufacturers and consumers during the introduction period – which is largely unpredictable and subject to frequent changes.

On the other hand, Going-Electric confidently predicts that the sales curve will not be linear: sometimes after 2020, it will rapidly rise to a near 100%, as per the dotted curves below.

We believe that electric car sales will increase sharply sometimes between 2020 and 2030 for the following reasons:

• High production volumes and technological improvements will sufficiently reduce EV purchase price to make them competitive against Internal Combustion Vehicles (ICVs).
   
• In 10 or 20 years time, the price of oil will most probably be much higher than today, deterring consumers from using ICVs.
   
• Once EVs are accepted by consumers, public authorities are likely to restrain the use of ICVs within city limits in order to reduce urban pollution and noise and offset the cost ICV externalities (such as health effects and building renovation). This will be a strong incentive for purchasing electric cars.

So if the number of EVs sold in 2020 is anyone’s guess, it is very likely that electric cars will become the norm sometimes between 2030 and 2040. In order to remain competitive, car manufacturers must now start concentrating all efforts towards this technological shift.

Batteries

Technically, a battery is any device that can store energy.  But what we typically refer to when we think “battery” is an electrochemical device that converts chemical energy into electricity through a galvanic cell.  A galvanic cell is a device consisting of two electrodes of different metals that we call anode and cathode, and an electrolyte chemical (usually acid) solution.  When we connect two or more of these galvanic cells in a series connection we call this a battery.  For example, the left side of the graphic below shows a single cell of a multi-cell battery connected in series inside of a casing.

PV System Batteries

In a stand-alone off-grid system, batteries store energy created by the Solar PV panels to use later at night where utility grid power or other energy source power is not available.  In an off-grid PV system, batteries are typically the second most expensive component of the system.   Therefore, the type and care of off-grid PV System batteries is critically important to the long-term cost-effective operation of the system.

A battery’s capacity for holding energy is rated in amp-hours, 1 amp of current delivered for 1 hour = 1 amp-hour.

Also, battery capacity is typically listed in amp hours at a given voltage.  For example, a battery rated at 100 amp hours (20 hour reference) will deliver 5 amp hours for 20 hours before being discharged.  Note that manufacturer’s typically rate storage batteries using a 20-hour rate.

Another way to rate batteries is by their charge “cycles”, where a “cycle” is one complete discharge and recharge of the battery.   These ratings apply to batteries as either “shallow” cycle or “deep” cycle.   Shallow-cycle batteries, such as those used in automobiles, are designed to deliver several hundred amperes of current for just a few seconds, i.e., a high charge, in order to turn the starter to start the car.  Once started, the car’s alternator takes over and the battery is quickly recharged.   Shallow charge batteries, therefore, are used in applications where a large charging current is needed for a very short time.

Conversely,” deep-cycle” batteries are designed for long-term energy storage where only a few amperes of current are need for hundreds of hours between charges.   This is typically what is required for an off-grid PV system and, therefore, deep-cycle batteries are best suited for stand-alone PV power systems.

Keep in mind that these two types of batteries are designed for different applications and should never be interchanged.

Also keep in mind that battery cycle of a battery depends the depth of discharge for a given battery, where this can have a major affect on the lifetime of the battery.  Depth of discharge (DOD), also called “state of charge” of a battery is a measure of how much a battery is discharged (DOD) or how much energy remains in the battery (State of Charge).  It is important to remember that batteries should never be discharged beyond their rated DOD.  Discharging a battery below its DOD rating can cause damage to a battery which will affect its life time.  This can also lead to over-charging a battery to bring it back up to full charge, which can cause boiling of the electrolyte and further damaging the battery.

The following is a list of basic rules to follow to help you extend the life of your batteries in your Off-Grid PV System.

1. Always install and/or replace batteries in sets as batteries like to be together in the same group.  If you have 8 batteries in your system, avoid replacing just one or two batteries.  Try to install them all at the same time, and replace them all at the same time.  (However, it is also a good practice to rotate two batteries at a time in your set with fresh batteries as long as you rotate through the entire battery array at even time intervals).
2. Always check your battery connections; avoid battery post corrosion.
3. Try to keep the battery enclosure temperature somewhere between 50-90°F.  This will help extend the life of the battery as well as its efficiency.
4. Once they are installed, try to avoid moving or disturbing your batteries as much as possible.
5. Use a hydrometer to test the electrolyte level of each and every battery cell at least 2-3 times each year.   Recording these levels readings can help with changing trends to determine when to replace your batteries.

Roofers and Solar Installers don’t always talk the same language when it comes to explaining roof angle.  Solar Installers are always told to install panels at an angle – given in degrees (usually based on latitude position).  Roofers, on the other hand, use construction terms to define a roof angle. A  roofer describe this angle as “pitch”. For example a “5:12 Pitch”  means for every 12” of run there is a 5’ rise.  A Solar Installer can easily find the pitch of an existing roof  using a simple L-Square and a small level.

Hold the level against the L-Square and make sure the bubble is level. The “run” should be at the 12” mark. Check the rise. In this case we can see that there is 5 inches or rise for the 12 inches of run.  As you can see, we have created a triangle between the L-Square and the roof.

Since the purpose of this article is to get to the answer, we will avoid deep trigonometric functions and other math terms that make grown men weep – or slip into a coma while standing on a ladder. All we are looking for is angle “a”, as shown in the right triangle below.

We are looking for angle (a)

Now, your calculator must have an inverse tangent function. Sometimes these are labeled atan, arctan, or tan^-1 button. Often you must hit the 2^nd function key of the tan button to get the inverse function. Also, make sure your calculator is set up to give answers in degrees instead of radians.

To calculate the angle of a 5:12 roof enter;

tan^-1 (5/12) = 22.619 degrees

This works with any roof rise. For example;

tan^-1 (1/12) =    4.763  degrees

tan^-1 (2/12) =    9.462  degrees

tan^-1 (3/12) =   14.036 degrees

tan^-1 (4/12) =   18.434 degrees

tan^-1 (5/12) =   22.619 degrees

tan^-1 (6/12) =   26.565 degrees

tan^-1 (7/12) =   30.256 degrees

tan^-1 (8/12) =   33.690 degrees

tan^-1 (9/12) =   36.869 degrees

tan^-1 (10/12) = 39.805 degrees

tan^-1 (11/12) = 42.510 degrees

tan^-1 (12/12) = 45         degrees

Tom Cawley – PV Installation Instructor

Up to now, there existed only one option for any kind of acknowledgement of entry level knowledge of Solar Photovoltaic basics. This option was the NABCEP Entry-Level Certificate of Knowledge.

Today, this no longer holds true. Thanks to the Electronics Technician Association (ETA), you now have another option. Today you can now earn an “ACCREDITED CERTIFICATION” as an Entry-Level Solar PV Installer. ETA is a worldwide and highly respected entity that has provided over 100,000 technical certifications in the fields of electronics, fiber optics and others since 1978. ETA is accredited by the International Accreditation Council (ICAC) which audits ETA’s certification programs on a 5 year schedule. This assures quality solar training by qualified instructors because in order to offer an ETA certification not only does the course and materials need to be reviewed and approved, but the instructor must also be certified to teach the material and to proctor the exam. The ICAC audits make sure this happens. Then, to make sure the certification competencies are complete, ETA certification requires a hands-on component where each student must complete specific skills tasks, in addition to passing a written exam, in order to earn the Entry Level Installer Certification.

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