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Utility Grid Tie Considerations
First off, insure that your battery grid tie is a safe power module. This is crucial, your charger should be certified by an independent
testing laboratory such as UL, ETL, CSA, etc., and
stamped accordingly. This is your assurance that it
be safe, will meet the manufacturer’s specifications,
and will be approved in an electrical inspection. There
are different design and rating standards for various
geographical regions for code compliance.
These also vary from one country to another.
Grid Tie are designed to interact with the utility and sell power back to the utility when there is a surplus. Two distinct styles are available: - those that have no battery storage and feed power directly into the grid
- those that function like a standard battery based alternative energy system - basically a home size battery backup system - When there is excess power it is sold back to the utility.
You can truly become your own power company and not only a user of power, but a provider as well. There are multiple layers of bureaucracy that surround this issue, scroll down to get a primer!
You can purchase a fully certified grid intertie inverter system that is compliant with world wide accepted standards, plug it into your house and become a power provider. This is not Science-Fiction, or a product from Popular Mechanics. These are certified products that are available, off the shelf for people just like you to use!
A grid tie is simply a DC - AC power inverter that meets the specifications of the electrical grid. Click here for more on DC - AC power inverters
National standards for utility interconnection
of PV systems are being
adopted by many local utilities. The
most important of these standards
focuses on inverters. Traditionally,
inverters simply converted the DC
electricity generated by PV modules
to the AC electricity we use in our
homes. More recently, inverters have
evolved into remarkably sophisticated
devices to manage and condition
power. Many new inverters contain
all the protective relays, disconnects,
and other components necessary to
meet the most stringent national
standards. Two of these standards are
particularly relevant:
Institute of Electrical and Electronic Engineers, P929:
Recommended Practice for Utility Interface of Photovoltaic Systems.
Institute of Electrical and Electronic Engineers, Inc., New York, NY (1998).
Underwriters Laboratories, UL Subject 1741:
Standard for Static Inverters and Charge Controllers
for Use in Photovoltaic Power Systems (First Edition).
Underwriters Laboratories, Inc., Northbrook, IL (December 1997).
You don’t need to fully understand
these standards, but your PV provider
and utility should. It is your obligation
to make sure that your PV
provider uses equipment that complies
with the relevant standards,
however, so be sure to discuss this
issue. ALL BD BATTERIES INVERTERS SOLD ARE COMPLIANT WITH THESE STANDARDS.
If you live where a homeowners association
must approve a solar electric
system, you or your PV provider may
need to submit your plans. You’ll
need approval before you begin
installing your PV system. However,
some state laws stipulate that you
have the right to install a solar
electric system on your home.
You will probably need to obtain permits
from your city or county building
department. These include a building
permit, an electrical permit, or both.
Typically, your PV provider will take
care of this, rolling the price of the
permits into the overall system price.
However, in some cases, your PV
provider may not know how much
time or money will be involved in
“pulling” a permit. If so, this task
may be priced on a time-and-materials
basis, particularly if additional
drawings or calculations must be
provided to the permitting agency.
In any case, make sure the permitting
costs and responsibilities are
addressed at the start with your PV
provider before installation begins.
Code requirements for PV systems
vary somewhat from one jurisdiction
to the next, but most are based on
the National Electrical Code (NEC).
Article 690 in the NEC spells out
requirements for designing and
installing safe, reliable, code-compliant
PV systems. Because most local
requirements are based on the NEC,
your building inspector is likely to
rely on Article 690 for guidance in
determining whether your PV system
has been properly designed and
installed. If you are one of the first
people in your community to install
a grid-connected PV system, your
local building department may not
have experience in approving one
of these systems. If this is the case,
you and your PV provider can speed
the process by working closely with
building officials to bring them up
to speed on the technology.
What should you know about
insurance?
For grid-connected PV systems, your
electric utility will require that you
enter into an interconnection agreement
(see also the next section).
Usually, these agreements set forth the
minimum insurance requirements to
keep in force. If you are buying a PV
system for your home, your standard
homeowner’s insurance policy is
usually adequate to meet the utility’s
requirements.
How do you get an
interconnection agreement?
Connecting your PV system to the
utility grid will require an interconnection
agreement and a purchase
and sale agreement. Federal law and
some state public utility commission
regulations require utilities to supply
you with an interconnection agreement.
Some utilities have developed simplified, standardized interconnection
agreements for small-scale PV
systems.
The interconnection agreement specifies
the terms and conditions under
which your system will be connected
to the utility grid. These include your
obligation to obtain permits and insurance,
maintain the system in good
working order, and operate it safely.
The purchase and sale agreement specifies
the metering arrangements, the
payment for any excess generation,
and any other related issues.
The language in these contracts
should be simple, straightforward,
and easy to understand. If you are
unclear about your obligations under
these agreements, contact the utility
or your electrical service provider for
clarification.
Some utilities offer customers with
PV systems the option to net meter
the excess power generated by the
PV system. As noted, this means that
when the PV system generates more
power than the household can use,
the utility pays the full retail price
for this power in an even swap as the
electric meter spins backward, and
your PV power goes into the grid.
Net metering allows eligible customers
with PV systems to connect
to the grid with their existing single
meter. Almost all standard utility
meters can measure the flow of
energy in either direction. The meter
spins forward when electricity is
flowing from the utility into the
building and spins backward when
power is flowing from the building
to the utility.
For example, in one utility program,
customers are billed monthly for the
“net” energy consumed. If the customer’s
net consumption is negative
in any month (i.e., the PV system
produces more energy than the customer
uses), the balance is credited
to subsequent months. Once a year,
on the anniversary of the effective
date of the interconnection agreement,
the utility pays the customer
for any negative balance at its wholesale
or “avoided cost” for energy,
which may be quite small, perhaps
less than 2 cents per kilowatt-hour.
Net metering allows customers to get
more value from the energy they
generate. It also simplifies both the
metering process (by eliminating the
need for a second meter) and the
accounting process (by eliminating
the need for monthly payments from
your utility). Be sure to ask your
utility about its policy regarding
net metering.
Under the federal Public Utility
Regulatory Policies Act (PURPA), utilities
must allow you to interconnect
your PV system. They must also buy
any excess electricity you generate,
beyond what you use in your home or
business. If your utility does not offer
net metering, it will probably require
you to use two meters: one to measure
the flow of electricity into the building,
the other to measure the flow of
electricity out of the building. If net
metering is not available, the utility
will pay you only a wholesale rate for
your excess electricity. This provides a
strong incentive to use all the electricity
you generate so that it offsets electricity
you would otherwise have to
purchase at the higher retail rate. This
may be a factor in how you optimize
the system size, because you may want
to limit generating excess electricity.
Such a “dual metering” arrangement is
the norm for industrial customers who
generate their own power.
After your new PV system is
installed, it must be inspected and
“signed off” by the local permitting
agency (usually a building or electrical
inspector) and most likely by
the electric utility with which you
entered into an interconnection
agreement. Inspectors may require
your PV provider to make corrections
(which is fairly common in the construction
business). A copy of the
building permit showing the final
inspection sign-off may be required
to qualify for a solar rebate program.
Is the lowest price the “best
deal”?
It might not be. You generally get
what you pay for, and it's possible
that a low price could be a sign of
of a poor product. Companies that produce quality products,
in order to stay in business must charge
enough for their products and
a fair profit margin. Therefore, price
should not be the only consideration,
and quality should probably
rank high on the list.
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