If you have been following the series on Solar PV, then you know that it
has covered power generation thus far. The idea is, in the most simple of
terms: Sun shines, appliances work. This is great, but most of us are not home
during the day to use 10KW UPS
. Is this power wasted? What happens at night
when American Idol airs and there is no sunlight? (I know you will see the
other parents in the school parking lot tomorrow morning; rest assured, you
will be in the loop). The real question is, 'How is this energy stored?'
and Solar PV 103 aims to answer just that.
Energy storage is no simple task. The goal is to answer the following: how
can we use energy available now to power something later on; it is like asking,
how can I cook breakfast, lunch and dinner now so that it will have that fresh
from the oven taste and temperature at meal time?
You probably know the most common way to store energy, batteries, but
there are actually many ways of doing so. One technique is the use of
flywheels. Sparing much of the technical detail, electricity is used to power a
motor which spins very heavy wheels. These wheels remain spinning until
electricity needed, at which point they transfer their spinning force to a
generator to re-create electricity. Another popular choice is the Fuel Cell.
This can get very technical as well, but the basic idea is that energy is used
to store Hydrogen. When the demand for electricity arises, the stored Hydrogen
is combined with Oxygen from air and with the use of a catalyst, a chemical
reaction takes place which produces electricity, heat and water, making it a
very clean solution (storing the Hydrogen is the tricky part).
Clearly these solutions are rather scientific, so what if there were other
ways? Some ideas start by asking the question, 'What will I need this energy
for?' and designing a specific solution for that need. Some buildings in New
York City, for example, take power at night when electricity is quite cheap and
create ice such that during the day, when electricity rates are very high, the
building is cooled by blowing air over these very large ice blocks. It is in
this way that energy available now may be used later.
But there is another idea: the "I'll scratch your back; you scratch
mine" approach. That is, I will give you my readily available power now in
exchange for yours when I need it. This is the crucial idea when thinking about 36v solar charge controller. All day as your system is pumping out electricity, it is
being sent back to the grid for use by other homes and offices that do not have
power sources of their own. The grid knows that you are doing it a favor and
issues you a credit (Your home or office is outfitted with an electric meter
that will actually spin backwards when you are supplying power). Therefore,
at night, when your solar array is dormant, you draw power from the grid
working against this credit. Solar installers have copious data on average
sunlight and can quite accurately size your system such that this day/night
issue, as well as seasonal effects will result in the near-elimination of your
electricity bill.
Of course, solar power does not have to be grid-tied, but going off grid
means additional costs for battery backup, battery maintenance, and the loss of
many financial incentives available to grid-tied systems (topics which will
be discussed in more advanced lessons later).
I hope you have enjoyed this lesson on energy storage; please keep an eye
out for Solar PV 104 - Racking.
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