Solar Power World

Important Physical Characteristics for the Utility Power PV Industry: Strength, Physical Characteristics and Electrical

Strength: Strength measures the resistance of a material to failure, given by the applied stress (shear, tensile or compression). Strength is a measure of a material’s ability to withstand stretching or compressing under load. On the other hand the toughness indicates how much energy a material can absorb before rupture. Increasing strength, tensile or compression, usually decreases toughness and vice versa. Whereas steels often have high strength, they exhibit low toughness which means they dent easily and are difficult to drill or penetrate. Thermosets and thermoplastics, or composites, exhibit average strength but high toughness meaning they can withstand sudden impacts and maintain their shape. Today’s composites have improved dramatically in that they can now be designed for both high strength and toughness via additives and fiber reinforcements.

Physcial Characteristics:

Some considerations to take into account before selection:

1. Custom size or shape necessary: Knowing your equipment dimensionality will establish the enclosure size and if a custom size or shape will be needed.
2. Special requirements for Utility Power PVows or depth:  For example a useful feature can be a clear lid/Utility Power PVow which lets end users see internal readouts without drilling access holes.
3. Aesthetics –Will the enclosure need to be colored to meet specific needs, keep in mind both composite and metal materials offer these capabilities.
4. Mounting of enclosure: A pad or rooftop area or will it mount to a pole, wall, or h-frame?
5. Field modifications-Many enclosures need some field modification to allow for inputs and outputs. Some enclosures are easier to modify than others. Certain materials are more easily drilled to add lines.
6. Weight-Lightweight materials are easier to lift and work with, especially when the enclosed components are of significant weight or when the enclosure will be wall- or pole-mounted.

Electrical : Like the physical, there is concern regarding the protection offered for the installed components as well as protection of the enclosure itself. An enclosure that breaks down over time can no longer perform the duties for which it was specified.

Therefore, the following characteristics are important:

1. Electrical conductivity
2. Thermal conductivity
3. Grounding
4. Arc resistance

Material Selection and Utility

Material Selection: If you have the opportunity to select the material, ensure you have investigated the material and that it is the most appropriate for the type of environment. Every application has its unique demands, and elements of this list do not follow a precise order. Indeed, many of the capabilities are considered to be inherent in certain material choices. An errant or over-estimated material choice, however, can have many repercussions in the life cycle of a product. It makes good sense to specify a product that qualifies in almost every category, insuring satisfactory results without regard for the type of installation.

Why Choose Composites: It Provides The Longest Life and Maximum Reliability

• Life cycle costing of composites-In spite of a higher prime cost compared to traditional materials like steel, aluminum, the  use of composites; by virtue of negligible maintenance, minimal recurring cost requiring no replacement (due to deterioration in service) translates in a lower overall cost over the life span of the product
• Composites (FRP) enclosures were developed as an answer to corroding stainless steel enclosures in marine environments
• Inherent safety as composite enclosures are not conductive
• Composites are less likely to be affected by temperature due to material stability
• Painting of carbon steels increases cost and risk of failure due to failure at or near pentrating  and mounting locations.
• Lighter weight reduces installation headaches

• Modifications of composites are easy

Additional Benefit of Composites: Extensive History of Success Permits New Kind of Warranty

If you choose composites for your Utility Power PV application you need to know that all composite materials are not the same. So how do you know which to choose—one with a warranty.  Since a company who typically offers a warranty has invested tremendously in their product to ensure their product will perform as promised.

For example, in the mid-1950s and 1960s there were driving forces that led to the interest and investment in composite materials in the United States. During this time the Stahlin brothers, who founded our company also invested in composites. However, as with any new product, there were demands from our customers to develop materials that would last longer in the field. Stahlin wanted to meet the demand and worked hard to continually improve the material used for our enclosures.

Naturally, when your composite material has been used in harsh environments for as long as ours, your company also gains from this experience. So with a long history of very low failure rates for our material behind us, in 2010, we had the confidence to offer an extended warranty.  Our warranty now states that our product will be free of failure due to manufacturer defects for a full decade.

Material Utility: This addresses the consideration for machining, cutting, sawing, drilling and modifying the material of choice. User preference plays a significant part in this selection and material familiarity overrides practicality in many instances. Below are a few items to keep in mind for both no-metallic and steel modifications.

Modifications of Composite Enclosures: Knowledge Makes it Easy

Composites offer the benefits of part integration and minimization along with substantial savings in weight. Along with that advantage is a reduction in the requirements for machining operations that need to be performed to complete an assembly. However, all drilling and cutting operations cannot be avoided completely in all cases. There are several types of machining operations that can easily be performed on composites, including: turning, drilling, routing, trimming, sanding, and milling. Most of these operations are similar to metal removal techniques but there are some differences that need to be addressed in order to make clean, high quality holes and cutouts in composites.

Delaminating of the outer surface and glass fibers directly below the surface are the main failure modes noticed when holes or cutouts are drilled or cutout improperly. Most times excessive edge chipping around the perimeter of the cutout or hole is due to improper tools used and methods applied.  A little planning and understanding of the proper methods to machining composites up front can make all the difference in the final outcome of the operation. Factory-option modification is also a highly desirable alternative for many end-users because it enables the manufacturer to use its skill in providing enclosure modifications and shipping to the customer ready-to-use.

Stainless Modifications: Keep in Mind the Type of Tools Used

If modifications such as custom sizes or shapes are required, both mild and stainless steel are good candidates. Both are fabricated from a flat sheet of metal, making them easier to form to custom specifications in the fabrication process. Mild steel is a viable option—with the correct metal-working tool, holes can easily be added in the field. Stainless steel, due to its hardness, is very difficult to cut and far more challenging to modify on-site.  The elements of chrome and nickel provide stainless steel great corrosion resistance to oxidation. But also, stainless steel can be contaminated by using carbon steel power tools and other tooling equipment. Skilled shops with proper quality control programs and knowledgeable craftsman can prevent stainless steel contamination.

Conclusion: Best Practices for Enclosure Selection

Specifiers for enclosures for Utility Power PV applications must carefully evaluate all factors to ensure an enclosure made of any material type will withstand its environment. The process for proper material and enclosure selection begins with a detailed consideration of the Utility Power PV application. Each Utility Power PV environment is unique and all possible applications should be identified for the intended enclosure application. So start with a simple list of your needs and ask plenty of questions because failure of your enclosure can’t be an option when everyone is relying on the Utility Power PV Industry to help reduce our dependence on fossil fuels and reduce CO2 emissions.