Philly Spring Cleanup 2011: Are you participating?
The 4th Annual Philly Spring Cleanup is coming up on Saturday, April 2, 2011 (rain date, Saturday, April 9, 2011). Are you planning to participate? Did you organize a clean up in your neighborhood? We’re hoping to get some major clean up done in our neighborhood, and we’d love to hear about how you’re getting involved in yours.
Find out more about how you can help at the Streets Department website.
Solar 101: How the output of a solar system is calculated
If you are looking into solar and have reached the point of obtaining a Solar Estimate from an installer, you would have noticed that your system’s output is measured in kWh (kilowatt-hours). Or, kilo…what…’s this mean? Apart from being subjected to bad solar puns, kWh is a term that will no doubt cause some confusion for the first-time solar inquirer. If you have been studying up on solar, then you may be wondering how the output is actually calculated. As we said in our first Solar 101, Solar Panel Technologies – what’s the difference?, we’re here to de-bunk some one the lingo used in the industry (and the calculations behind it), to help you make informed decisions when looking into solar.
Before we get into the details of how the output of a solar system is calculated, let’s just refresh your memory of the basics. Below are some of the key terms and their definitions, relative to you – the solar inquirer.
- Watts – A term usually used to describe the size of an individual solar panel, it is a unit of electrical power that indicates the rate at which energy is produced.
- Kilowatts – One thousand watts
- Kilowatt Hours – The number of watts produced (or used) per hour. E.g. a solar panel that is 185W, will produce 185W in 1 hour (max), or 0.185kWh.
- DC – Direct Current, measured in Volts. This type of electricity is produced by the solar panels, but cannot be used in your home just yet.
- AC – Alternating Current, measured in Volts. The type of electricity is produced by a solar system’s inverter, which converts DC to AC, suitable for use in your home or business.
- Peak Sunlight Hours (PSH) – The sum of each sunlight hour’s rate of solar insolation, divided by the maximum rate of solar insolation. In other words, if we squashed all the sunlight hours in a day together, how many of the absolute best sunlight hours would it create? E.g. 10 sunlight hours may equal 4 peak sunlight hours.
- Pitch – The longitudinal angle of the solar panel in relation to the sun. 0 degrees would be mean a solar panel is laying flat, whereas a pitch of 39 degrees would mean it is facing directly at the sun.
- Azimuth – The latitudinal direction of the solar panel in relation to the sun. As the latitude of the sun at the equator is 0 degrees, solar panels in the northern hemisphere should face south, or 180 degrees.
A little confused? Not to worry. It is not until we apply these terms and measurements to a system, that they actually become easy to understand and relevant. So first, let’s get started on sizing a system!
Step 1. Calculate the System Size
Lets say you would like 20 x 200W solar panels. To calculate the system’s basic DC output, we simply multiply the number of panels by the panel size (W).
20 x 200W = 4000W / 4kW
This is typically how an installer will describe the size of the system to you. This output figure (4000W) is also the answer to a hypothetical question: How much energy could the system produce per hour, if it received the maximum amount of sunlight possible, as the optimal temperature? In other words, an unrealistic scenario. So how do we work out the DC output for a more realistic scenario?
Solar 101: Solar Panel Technologies Explained
Most people looking into solar power for the first time will inevitably be faced with certain terminology, which may be confusing, and sound like a new language. Like most new technology, learning the ins and outs can be intimidating, which is why we’re here to help clear the air (both literally and figuratively). This is the first in a series of Solar 101′s, designed to help you understand the finer points about solar, so that you can research solar power effectively and efficiently, and ask all the right questions when investigating solar power for your home or business. And maybe even impress people with all your solar know-how at your next BBQ.
Much of the new terminology most first-time solar inquirers will be faced with refers to the technology available on the market today. Terms such as Monocrystalline, Polycrystalline, and Thin Film, just to name a few, are different types of technology available to both residential and commercial consumers. Although many solar panels look the same, each type of technology offers vastly different advantages and disadvantages, all of which are considered when selecting the right panel for the job.
So, to help you determine which panel may be the best fit for you, here are some of the main points about the most commonly found technologies on the market today:
Monocrystalline
These solar panels are the most commonly installed solar technology, selected for their “all-round” good efficiencies. Their appearance is distinguished by blue or black solar cells, with white or black squares located at the corner of each cell, like a checkerboard. The solar cells are made from the semiconductor material, silicon, which for Monocrystalline cells, is cut from a single ingot of pure silicon – like cutting slices of bread from a loaf.
Advantages
- As Monocrystalline cells are made from pure silicon, it ensures a relatively high level of power efficiency.
- Due to the density of the crystals in each cell, it creates a very space efficient panel.
- As their production process is costlier and more involved, often only reputable and reliable manufacturers produce them
Disadvantages
- A slightly higher cost-per-watt may be seen, due to the manufacturing process
- Most Monocrystalline panels are significantly affected by shade
For Who
Residential applications, people with limited roof space, such as townhouses, and/ or wanting a high quality product.
Rating
Space Efficiency: ****
Power Effciency: *** 1/2
Polycrystalline
Characterized by an all-blue, crystalized appearance, Polycrystalline panels are typically less expensive compared to Monocrystalline panels. This can be attributed to a more cost-efficient production of polycrystalline cells. In this process, liquid silicon (less pure than in Monocrystalline) is poured into blocks that are subsequently sawed into plates. During solidification of the material, crystal structures of varying sizes are formed, at whose borders defects emerge. As a result of this crystal defect, the solar cell is less efficient than their Monocrystalline counterpart.
Advantages
- Lower production costs can result in lower cost-per-watt panels
- The relatively high density of crystals in the cells results in a fairly space-efficient panel
Disadvantages
- Lower production costs can attract less-reputable manufacturers
- Most Polycrystalline panels are heavily affected by shade
For Who
Residential applications, people with limited roof space, and/ or wanting a lower-cost product.
Rating
Space Efficiency: *** 1/2
Power Efficiency: ***
Thin Film / Amorphous
Quickly becoming one of the most commonly manufactured panels on the global market, Thin Film clearly differentiates itself from Mono and Polycrystalline on almost every level. Thin Film panels are usually one solid color (e.g. black, dark blue, dark red), due to their manufacturing process. Silicon is deposited on glass or metal, as opposed to being cut from an ingot of silicon. The layer thickness amounts to less than 1µm (thickness of a human hair: 50-100 µm), so the production costs are lower due to the low material costs. However, the space efficiency of thin film/ amorphous cells is much lower than that of the other two cell types. What Thin Film modules lack in space efficiency, they make up for in power efficiency; they are excellent performers in areas of shade and high heat.
Advantages
- As they are one large cell, they are less effected by shade, compared to other panels
- Usually have a low heat coefficient, resulting in higher performances in hotter temperatures
- Can be lower cost-per-watt than other panels
Disadvantages
- Very space-instensive
- Low space efficiency means more panels are required for desired output
For Who
Limited residential applications, commercial buildings, solar farms, areas of high shade and/or heat
Rating
Space Efficiency: *
Power Efficiency: *****
Buzz about the Crane Arts 81 kW system
81 kW solar power system on the Crane Arts Building - Philadelphia, PA
The launch of the 81 kW solar power system on the Crane Arts building in Kensington went off without a hitch last Thursday. Counsilman Bill Green, State Rep. Tony Payton Jr., and State Rep. Michael O’Brien were on hand to help Solar States flip the switch, so the system could officially start powering the building. We had such a great time celebrating this accomplishment, and getting to talk to community members, Crane Arts tenants and local government officials about the potential of solar in Philadelphia. Check out the video below to see the coverage that ABC News Philadelphia gave to the event.
