Connecticut PV Incentive: What’s PTC and how does that affect My Rebate?

The Connecticut Clean Energy Fund (CCEF), has a state rebate program that is based on the design efficiency of your system.  Typically an installer will calculate how much electricity your PV system will produce and compare it with a similar system under ideal conditions.  Then they apply a design factor to calculate the dollars per watt price.  A more efficient system will help maximize your rebate. 

Ideal conditions to maximize your rebate:

ü      Include having an inverter that is 94% efficient or better.

ü      There can’t be any shading on the site

ü      Panels must face solar south (plus or minus 20 degrees), and they also have to be tilted at a 35º angle. 

The maximum rebate for residents in Connecticut is $15,000, with a maximum system size of 10 Watts.  A maximum rebate will provide residents with $1.75/watt (PTC rating) for the first 5 kW and $1.25/watt (PTC rating) for the next 5 kW.  Rebates are paid based on PTC values.

STC Vs PTC

ü      STC or “Factory Standard Test Conditions,” uses 1,000 watts per square meter solar irradiance, 1.5 Air Mass and 25 ºC cell temperature. 

ü      PTC or “Photovoltaic USA Test Conditions,” deals with more of a real life condition.  PTC rates output using a condition of 1,000 watts per square meter solar irradiance, 1.5 Air mass, and a 20ºC ambient temperature at 10 meters above ground level and a wind speed of 1 meter per second. 

PTC = Real Life Conditions

As you can see the PTC rates output more effectively than STC.  The ambient temperature is a better standard than the factory conditions because silicon solar cells average almost 20ºC above ambient temperature in the real world and an increase in temperature causes cell voltage to decrease. 

PTC Accounts for Temperature

Also cell voltage drops .08 volts/ºC in places that exceeds 25ºC, which shows that the STC rating is not as efficient as the PTC.  Unlike STC, PTC takes account for the fact that the sun is only close to perpendicular for a limited time at high noon.  PTC also recognizes that at other times of the day the sun hits the panels at different angles.  While taking all of these factors into consideration, PTC averages the solar panels yearly output.  The PTC rating tends to be lower than the STC rating since it takes more factors into account, which gives future consumers a better indication of how the solar panels will hold up.  So when buying a solar panels the higher the PTC rating the better.

                                    

Solar Panels Threatening To Collapse Your Roof? Not a Chance!

            Some of the most frequent questions are around the weight and loads that solar panels put on a roof.  This blog covers a few examples of what loads can be found under different climates.

Contrary to many beliefs solar panels are actually very lightweight.

Can My Roof Support Solar Panels?

On average solar panels weigh about 23 pounds and are distributed evenly across a roof.  The combined weight of a solar panel and the rack only puts 2-3 pounds of weight per square foot on a roof.  Most modern roofs are built to support much more weight than that.  There are some cases where a roof has been weakened by water damage and other similar problems.  This is no reason to worry being that before every solar panel installation a solar contractor evaluates the roof’s structure to make sure that it can hold the solar panels.  With some damaged roofs, structural work must be done before installing the panels. 

Upward Force?

In fact the biggest issue when dealing with solar panels is not weight, but rather the uplift.  The uplift is an upward force from wind going up and under panels.  With enough upward force solar panels can be dislodged from the roof or even worse, your roof can be pulled off along with the solar panels.  These are rare circumstances which do not occur frequently.  To prevent any damages the panel must be bolted down into the center of the rafters and not just on the shell of the roof.   The good part is that solar contractors are trained to install everything properly and keep their customers safety as their number one priority. 

Unirac, a solar racking company, has a calculator for standard systems which were used to find the total uplift from wind and down force from snow.  Here in Connecticut we have an average snow load at 35 psf, and an average uplift design wind load at -16.5 psf.  Since we have mild weather in Connecticut, we are able to use more of a variety of solar panels and racks as the weather is not extreme.  In places like Miami where there are 155 mph winds and an uplift of -37 psf, you would need to use a heavier rail, have more attachment points on the roof and consider marine grade solar panels.  Flush racks are the best type of mount for high winds compared to Tilt-Up racks.  Flush Racks keep the solar panels down on the roof and allow little space for wind to blow under whereas Tilt-Up racks allow wind to cause upward pressure upon solar panels.  In areas like Syracuse where there is a 55 psf snow load, your solar contractor, architect or engineer may need to account for additional support due to significant snowfall demands.  Since solar panels have a life span of over 30 years, choosing the right racking solution is important to long term success.  Contact PurePoint Energy for your renewable energy needs.  203.642.4105 / www.purepointenergy.com

Efficiency Boosted by Color

Whenever energy is generated, the efficiency of the solar panel is one of the most important factors.  If efficiency is low than output is also low. Researchers are constantly trying to figure out how to make solar panels more efficient.  There have been many breakthroughs in increasing the efficiency of solar panels.  Solar panel’s temperature and type of material have been of major concern, but color seems to be a major factor.

Dark Absorbs More

An objects color is based upon the wavelength that they reflect.  White objects reflect all wavelengths, where black objects absorbs these wavelengths.  For example, you will notice that a black car absorbs more heat in the summer than other color cars.  This may be an inconvenience when dealing with cars, but it can greatly boost efficiency in solar panels. Common solar panels tend to be silver or black.  Black silicon was implemented to panels, and were found to be very effective.

Past solar panels maxed out their efficiency by about 25%, while black silicon panels are able to max out at a higher level.

They absorbed more of the sun’s light therefore creating more energy.  The reason why black silicon panels are not common is because they have been very expensive in the past.  Recently researchers have claimed to have innovated a new way to make black silicon panels more cost effective, in hopes to increase the effectiveness of energy solutions worldwide.

Food Coloring = Higher Efficiency?
The Journal of Renewable and Sustainable Energy recently reported that many off-the-shelf dyes, medical dyes and food dyes can increase solar panel efficiency when mixed properly.  The dye is used to change and expand the color spectrum that the panel can absorb, which can increase efficiency by as much as 8%.  This low-tech innovation could help improve the effectiveness of solar panels immensely, while keeping prices low.

GreenSun Energy has developed new solar panels that can generate power with non-direct sunlight and use far less silicon than traditional panels.  Unlike traditional panels which are silver and black, GreenSun’s panels use bright colors which allow them to capture different parts of the sun’s spectrum. 

These bright colored panels have gotten up to 12% efficiency and rising. (Typical panels on the market are around 14% efficient!)

Also the panels are currently being produced for about half the price of traditional silicon based solar panels.