Solar 101: Is my roof right for solar?
1.8 kW solar power system, Philadelphia PA
If you’re looking into solar, you’ve probably concluded that you’re going to need a South facing roof. You may also be thinking that your heavily pitched roof just won’t cut it for solar. But, don’t give up on the Solar dream just yet!
You may be surprised to know that many solar systems are not installed on a perfectly South facing roof. Nor are they mounted on a 39 degree roof. Although these attributes would make for an extremely efficient solar system, you should not discount yourself from the solar market just because your roof does not fit this criteria.
As we mentioned in our previous Solar 101, How the output of a solar system is calculated, orientation (north, south) and pitch (angle of your roof) are factors that influence the performance of your system – but just how much?
Orientation
The orientation of your system is the direction that it faces (e.g. South, West, East), which determines the time of day in which your system is directly facing the sun. If your system is installed on an East facing roof, your system will pick up all the morning sun, some of the afternoon sun, and be relatively ineffective in the ladder part of the day. However, if your system faces South, it is able to generate electricity all day, with it’s peak at around 12-2pm, depending on the time of year. But, does this mean that your East (or West) facing roof is not suitable for solar? Let’s find out, using an example:
System Size: 5kW (DC)
Pitch: 30 degrees
Daily kWh (AC) South facing: 18.21
Daily kWh (AC) East facing: 15.32
Daily kWh (AC) West facing: 14.60
As you can see, although a South facing is more efficient (thus, the more preferred orientation for solar), it is not by as much as you may think. So, if your South facing roof is not suitable for solar (shade, obstructions, little space), your East and West facing roofs are still great alternatives!
Pitch
The pitch of your system refers to its longitudinal angle. For example, if your system is pitched at 0 degrees, it would be laying flat; if it was pitched at 39 degrees, it would be directly facing the sun during summer. As most residential systems are installed on a pre-existing roof, the pitch of the system cannot be altered; it is equal to that of your roof. So is the pitch of your roof right for solar? Let’s find out, using another example:
System Size: 5kW (DC)
Orientation: South
Daily kWh (AC) 0 degree pitch: 15.70
Daily kWh (AC) 20 degree pitch: 17.92
Daily kWh (AC) 39 degree pitch: 18.31
Like with orientation, we can see that even the typically less-desireable roofs are still solar-friendly.
So before you count yourself out of the Solar game, allow a Solar professional to assess your roof first – you may be surprised at the results!
Data obtained from http://rredc.nrel.gov/solar/calculators/PVWATTS/version1. Location: Philadelphia.
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.
Sustainable 19125 Housing & Energy Fair
Last Saturday, we attended a Green Housing and Energy Fair, hosted by the New Kensington Development Corporation (NKDC) and Sustainable 19125. We were really excited to participate, since we’re just down the road in Northern Liberties we’re always looking for opportunities to get involved in the community and speak to our neighbors.
The Fair was held at Kensington High School for the Creative and Performing Arts, which was a perfect venue; Kensington CAPA is the first school in the region to be awarded platinum status under LEED certification. Hopefully this will become less of a rarity and more of the “norm” someday.
There was a great turn out and we really enjoyed talking to everyone who was interested about solar. For a few more pictures of the event (we were too busy talking to take more pictures!), check out the Sustainable 19125 blog.
Thanks again to the NKDC and Sustainable 19125 for inviting us to participate – we’re hoping there are many more events like this to come.
Did you stop by? Let us know what you thought of the event in the comments.
Launch of one of the largest solar systems in Philadelphia
For the last few months, we’ve been working on one of our biggest projects yet – designing and installing an 81 kW solar power system on the roof of the Crane Arts building in Philly’s Fishtown neighborhood. The system stands to be one of Philly’s largest solar installation to date.
Solar States has kindly organized the Flip the Switch Gala, held at the Crane Arts building on February 24 from 6-9 pm, to celebrate the launch of the system. Mayor Michael Nutter and State Representatives Tony Payton Jr. and Michael O’Brien will be on hand, among friends and neighbors, to show support for this major step for Philly’s sustainability. If you’re interested in attending the event, you can RSVP online.
Helio Power Systems is so proud to be a part of this project and we truly hope that this helps to shine a light on Philly’s potential for solar power.
Energy Consumption Over a Lifetime: What it looks like
It seems like everywhere you look these days there’s a new, green version of just about every product. With complete over saturation in the eco-friendly market, it’s easy to let “green washing” lead consumers to discount the need to be more vigilant about the impact that lifestyle has on our environment. It may be even easier to forget about your impact, because it’s relatively abstract - you can’t always visualize what the effect of throwing out five pounds of trash per week adds up to. Take a look at the info-graphic below, thanks to Well Home, to get a better idea of how your consumption adds up over time.
(click image to enlarge)
Does this graphic change the way you view your consumption?
8 Energy Saving Tips for Home
When we work with our clients to provide an initial estimate for solar power, we always take care to discuss current energy usage and household energy habits; with the average U.S. family spending about $1,900 a year on utility bills, this is an essential step. While you can absolutely reduce or eliminate your electricity bill by installing solar, you can see even greater savings by employing some very simple energy saving tips around the home. Check a couple of these energy savings tips off your list and you’ll see a decrease in usage and an increase in savings in no time.
- If you haven’t already, switch to Compact Fluorescent lightbulbs with the ENERGY STAR label. Switching to these energy efficient bulbs can decrease your lighting electricity usage by 50-75%.
- Purchase a lighting timer, for as little as $7, and program your lights to go on or off at a specific time – ensure that your lights aren’t in use when you don’t need them, without having to remember to turn them off.
- Turn off the computer and monitor in your home office when not in use.
- Try to plug home appliances, like TVs and DVD players, into a power strip, turning off the power strip when not in use. Even if these appliances are on standby mode, they are still using energy (and costing you money!)
- Install better insulation and seal drafty windows and doors – especially if you have an older home. Only 20% of homes built before 1980 are considered well insulated. You could be loosing up to 33% of hot or cold (depending on the season) air due to insulation and drafts caused by unsealed cracks.
- On average, 47% of your utility cost comes from heating and cooling. To combat this expense, install a digital, programable thermostat, so you can control the temperature of your heat and air conditioning more carefully.
- Hot water heating makes up approximately 12% of your utility bill – decrease your energy usage by installing an ENERGY STAR rated washer and dryer and dishwasher and consider switching to solar hot water.
- Only run dishwashers and washer/dryers on full loads – waiting to do a full load, as opposed to running several half loads, will save lots of energy.
Follow these simple steps as closely as you can, and you’ll be well on your way to reducing your environmental impact and keeping your money out of the hands of utility providers.
Coming soon!
Check back soon for blog posts on everything solar!