How does solar energy work?
As we have outlined here there are two key ways in which solar energy can be used in your home.
Solar thermal applications use the heat in sunlight to heat water or other fluids. A solar hot water service is the classic example of this. In simple terms, the heat energy in the sun passes into the water, the water heats up and hot water is nice to shower under.
The second major use of solar energy that has increased in usage only recently in US homes is solar electricity. Solar electricity is created by the photovoltaic affect.
The photovoltaic affect is the physical property that the irradiation in sunlight can stimulate the flow of electrons in a semiconductor material
But how does this meet the electricity needs of my house?
Firstly the sunlight shines on "solar panels", usually mounted and this creates DC (direct current) electricity. Each solar panel is usually a string of 60-72 solar cells string together in series on your roof. In the case of a system using a string inverter then the DC power will flow down to the inverter at which point the inverter will convert this electricity into AC (alternating current) power in the same voltage as is used in your house.
The inverter will then feed AC power to your circuit board and this power is available to service any electrical loads within your property. If the loads in your house are greater than the power that is being supplied by the inverter then your loads may be partly met by solar power and partly by the use of grid power. With gird connect solar power systems you have the option at any time to use either solar power, grid power, or a combination of both.
In some instances you may be generating more solar power than your total electrical loads require and in this case your solar electricity will flow back out to the grid through your meter. Usually your utility meter needs to be changed so that it can keep a separate record of what electricity you export to the grid and what you consume from the grid.
How do I power my house at night if I have solar power?
Electricity is instantaneous and we all know that the sun doesn't shine at night. What this means is that in a grid connect system you need to rely on grid power to service your electrical loads at night. In states with a 1:1 net metering policy for every kwh (kilowatt hours is a unit of measure for electricity) that you export during the day, you get a credit from your utility for the purchase of one kwh of electricity at night. This way, in states with a 1:1 "net metering policy" if you install a solar energy system that produces the same number of kwh's as you buy from your utility each year then you can get to a zero utility bill.
Battery Storage may be a game changer
Some states do not have 1 for 1 net metering policy. In these states often consumers with solar systems are paid only a fraction of the retail price for excess solar power that they export to the public utility grid during the day. In these states the availability of cheaper battery storage solutions which allow home owners with solar panels installed on their houses to store their excess daytime solar power for night time use, may make solar energy much more attractive. The announcement in 2015 of a cheap solar battery storage solution by Tesla has created a lot of excitement amongst home-owners in states that do not have a good net metering policy.