Frenquently Asked Questions
General solar FAQ
Q) Do we have enough sun in our area for solar to make sense?
A) We do. In fact we have more solar energy available here than they do in Germany. Germany produces more solar energy than any other country
Q) What is the difference between solar thermal and PV?
A) Solar thermal systems use the heat of the sun to heat an antifreeze solution which is pumped from the collector out side back into a heat exchanger to heat water. A PV (photo voltaic) system. Uses the radiation from the sun to generate DC electrical current in the panels which is either stored in batteries or immediately converted to AC power with an inverter.
Solar thermal FAQ
Q) How much money will I save?
A) Hot water accounts for about 1/3 of the typical household electric bill. You will be able to make up to 80% of your hot water from the sun. This is a year round average. During the summer a properly sized system will make all the hot water you need and often it will have enough excess capacity to ride through rainy days without running out.
Q) How well does it work on cloudy days?
A) As long as the clouds are not very dark such as rain clouds, the system will still make a lot of hot water. A lot of radiation penetrates the clouds. Evacuated tube collectors are very effective at capturing every available bit of light.
Q) What happens when we have several rainy day in a row? Will I run out of hot water?
A) Every solar water heater is designed with a backup system. In most cases it will be an electric heating element in your storage tank. It will come on as needed to make sure you don't run out of hot water. You can also use a tank-less water heater (also called inline, or on demand) as a backup as well as a separate tank type gas water heater.
Q) What is the difference between the types of panels?
A) There are 3 main types. Mono crystalline, poly crystalline, and micro crystalline (also called thin film) The mono crystalline panels are generally the most efficient and most expensive. Poly crystalline are a close second in efficiency and price. The Cells in these two types of panels are cut from a solid bar of silicon. Thin film is less efficient, but often much cheaper. Thin film panels are more effective at collecting energy from diffused light and on cloudy days. They are also more tolerant of extreme high temperatures that are encountered on rooftops in the summer. These panels have a thin coating of micro crystalline silicon rather than cells. This manufacturing process is much cheaper because it uses much less silicon and does not require cutting of a silicon bar.
Q) Which type of panel is best for me?
A) This depends on a lot of factors. The thin film panels take more space and more mounting hardware for the amount of energy you get from them. This can sometimes limit the system capacity too much if you don't have lots of space for panels. Also the cost of the mounting hardware can offset some of the savings you get by using thin film over crystalline panels. Crystalline panels are more compact because of there higher efficiency. If you don't have enough space for a thin film system, crystalline panels may be your only choice. Crystalline panels are expected to have a longer life than thin film panels. They can utilize micro inverters which gives them a lot more design flexibility in grid tied systems. After we do a site survey and discuss your goals for the system we will determine which panel type is best for your needs.
Q) What is the difference between a central inverter and a micro inverter?
A) A central inverter is also called a string inverter. It uses several panels wired in series to achieve the required DC voltage to produce 240V AC power. The number of panels in the string is determined by the electrical specs of the panels. Typical strings are 12 or more panels. This means that the minimum number of panels you can have is one string and any additional panels have to be added in full strings. The downside to this is if your roof or ground mount location has room for 20 panels for example you might only be able to install 12. The other disadvantage is if one of those panels gets shaded by trees or buildings for part of the day it affects the output of all the panels in the string until all the panels are in full sun. The advantage of central inverters is their low cost compared to micro inverters. Also they can be used with off grid systems as well as grid tied systems.
Micro inverters are small inverters that mount right under the panels. Each inverter can convert the DC power from just one panel to AC. The advantage is there is no limit to how many or how few panels you can use. Also if one panel is shaded it does not affect the other panels at all since each one is like an individual generator. They are constantly working to maximize the output of each panel. The down side is they cost more than a central inverter. Also they can not be used for off grid systems. Using micro inverters is one way to minimize the initial investment to get started in solar because you can install as few as 1 panel and add additional panels whenever you like in any quantity that you like until you are out of space or until you make all the power you need.
Q) What is the difference between a grid tie system and an off grid system?
A) A grid tie system works with your electric utility company. When you are generating more power than you are using your meter will spin backwards which allows you to sell power during the day. Then at night when your panels are not generating you can buy the power back. This is refereed to as net metering (see net metering question and answer). The advantage is that grid tie systems do not have batteries so they are cheaper and have much less maintenance. The disadvantage is that they do not provide backup power during power outages. Off grid systems do not connect to an electric utility. They use batteries to store electricity so you can have power at night and can even help you ride through cloudy days. There is also another system type called a hybrid system or backup system. They use batteries to provide backup power during power outages, but as long as the batteries are charged it will sell any excess power to the grid like a grid tie system.
Q) What is net metering?
A) Net metering is the practice of taking the difference between your power produced and power consumed at the end of the month either charging you for power used or putting a credit on your account for excess power produced. In Indiana they will not actually pay you for excess power, but they will let you use the credit next time you don't generate enough. A good example of this is when you generate more than you need for several months through the summer then use the credit in the winter when solar output is lower.