How To Power Your

2010 www.RunGreenPower.com Yoni Levy

How To Power
Your Home For
Free?

By Yoni Levy

2010


Table Of Content

Chapter 1: …………………………………………Turning Sunlight Into Electricity!

Chapter 2: …………….What exactly does green or sustainable living mean?

Chapter 3: …………………….What is a solar electric or photovoltaic system?

Chapter 4: ………………………………………………….What are PV solar panels?

Chapter 5: ………………….…………………………Solar Power – The Converters

Chapter 6: …………………….…………….……………..Solar Power - The battery

Chapter 7: ………………….……………How to size your photovoltaic system?

Chapter 8: ………………………….Before connecting a PV system to the grid

Chapter 9: ……………………How much will you save with your PV system?

Chapter 10: ………………………….FAQ Running Solar Power At Your Home


Chapter 1:

Turning Sunlight Into Electricity!

S
olar Cells convert light energy into electricity at the atomic level. It
was first discovered in 1839, the process of producing electric current
in a solid material with the aid of sunlight wasn't truly understood for
more than a hundred years.

Throughout the second half of the 20th century, the science has been refined
and process has been more fully explained. As a result the cost of these
devices has put them into the mainstream of modem energy producers. This
was caused in part by advances in technology, where PV conversion
efficiencies have been improved.

Solar Cell Materials The most important parts of a solar cell are the
semiconductor layers, this is where the electron current is created. There are
a number of different materials available for making these semiconducting
layers, and each has benefits and drawbacks. Unfortunately, there is no one
ideal material for all types of cells and applications.

In addition to the semiconducting materials, solar cells consist of a top
metallic grid or other electrical contact to collect electrons from the
semiconductor and transfer them to the external load, and a back contact
layer to complete the electrical circuit.


Then, on top of the complete cell is typically a glass cover or other type of
transparent encapsulant to seal the cell and keep weather out, and a
antireflective coating to keep the cell from reflecting the light back away from
the cell. A typical solar cell consists of a cover glass, a anti-reflective layer, a
front contact to allow the electrons to enter a circuit and a back contact to
allow them to complete the circuit, and the semiconductor layers where the
electrons begin to complete there voyages!

We tested 2 solar power kits for home, Check who is the best!


Chapter 2:

What exactly does green or sustainable living
mean?

What exactly, does green or sustainable living mean? Different people use
different definitions, but it all comes down to one fundamental concept: The
Earth's resources shouldn't be depleted faster than they can be replenished.

From that concept comes everything else, including caring for the
environment, animals and other living things, your health, your local
community, and communities around the world.

When you start to look at all the different kinds of resources — from fossil
fuels to forests, agricultural land to wildlife, and the ocean's depths to the air
that you breathe — it's easy to see how everything is interconnected and how
the actions that you take today can affect the future.

This chapter looks at the impact your lifestyle has on the Earth's resources
and then summarizes positive steps that you can take to protect and preserve
those resources — starting today.

Understanding the Impact of Your Choices Think about the concept of
sustainable living as being a lot like your family budget. If you spend more
than you make each month and neglect your bills as a result, the bill


collectors start calling, and if you keep going down the same path, you end
up owing so much that you can't possibly pay it back.

On the other hand, if you're careful with your monthly expenses (maybe even
saving a little), you're able to live within your means and keep everyone
happy, especially you. COPYRIGHTED MATERIAL The planet's no different.
Right now, its resources are being depleted far faster than they can be
replenished.

The call of the bill collectors is getting louder all the time, with the clear
implication that bankruptcy's down the road if something doesn't change.
Fossil fuels such as oil are becoming more difficult and more expensive to
bring out of the ground, and their reserves are dwindling.

Burning fossil fuels to provide energy for homes, vehicles, and industries
emits carbon dioxide and other greenhouse gases along with pollutants that
affect the health of the planet and its people.

Other resources are in trouble too, including water. In some parts of the
United States, drought conditions are becoming more common and more
widespread. Debates continue about where to find sources of water: to pipe it
in from other areas, to drill into underground aquifers, or even to build
desalination plants to take the salt out of seawater.

One possible effect of global warming is the further reduction of groundwater
sources. Decreasing the demand that people place on water sources is


essential in order to continue having enough water to go around. Thankfully,
it's not too late to turn the situation around — to make the changes that the
planet and its people need for a safe, healthy, prosperous, and
compassionate future.

Changes need to happen quickly, however: According to the United Nations,
some parts of the world are nearing the tipping point, after which the damage
will be irreparable.

A useful way to understand your impact on the environment is to measure
your ecological footprint, which is the land needed to support your
consumption of goods and resources. Think of it as a way of describing the
amount of land required to farm your food, mine your energy sources,
transport your goods and services, and hold your waste.

You make decisions every day that have an impact on the planet: choosing
between the car and local rapid transit, for example, or selecting local or
organic fresh food instead of packaged, processed food that has been
transported long distances.

Think about the impact that each individual decision has, and weigh the pros
and cons of your everyday actions. Carbon emissions are another measure of
your ecological footprint.

We have more about how carbon and other gases contribute to climate
change in for now, it's enough to know that carbon is released when many
substances — particularly fossil fuels such as oil, gas, and coal — are burned


by vehicles and planes; by the manufacturing processes of many consumer
goods; and by the heating, cooling, and electricity for your home.

The Earth Day Network, a network of environmental organizations and
projects, estimates that there are 4.5 biologically productive acres worldwide
per person. The average American's ecological footprint, however, is 24
acres, which means that a lot of people are using more resources than the
planet can afford.

Being Greener for the Good of People and the Planet You can measure your
own ecological footprint simply by visiting the Earth Day Network Web site at
www.earthday.net and entering some information about your lifestyle.

You're asked questions about _ The size and type of your home _ How often
you eat meat and processed foods _ How many miles you drive or take public
transportation each week _ How energy efficient your home and vehicle are _
How much waste you generate If you're only just starting a greener lifestyle,
reducing your ecological footprint may seem a little daunting.

You can reduce it significantly, though, and it won't take long. Use the
questions from the Earth Day Network to think about where you'd like to start
reducing your impact.



Chapter 3:

What is a solar electric or photovoltaic system?

Photovoltaic (PV) systems convert sunlight directly to electricity. They work
any time the sun is shining, but more electricity is produced when the
sunlight is more intense and strikes the PV modules directly (as when rays of
sunlight are perpendicular to the PV modules).

Unlike solar thermal systems for heating water, PV does not use the sun's
heat to make electricity. Instead, electrons freed by the interaction of sunlight
with semiconductor materials in PV cells are captured in an electric current.

PV allows you to produce electricity— without noise or air pollution—from a
clean, renewable resource. A PV system never runs out of fuel, and it won't
increase U.S. oil imports. Many PV system components are manufactured
right here in the United States.These characteristics could make PV
technology the U.S. energy source of choice for the 21st century.

The basic building block of PV technology is the solar "cell." Multiple PV cells
are connected to form a PV "module," the smallest PV component sold
commercially. Modules range in power output from about 10 watts to 300
watts. A PV system connected or "tied" to the utility grid has these
components:


• One or more PV modules, which are connected to an inverter

• The inverter, which converts the system's direct-current (DC) electricity to
alternating current (AC)

• Batteries (optional) to provide energy storage or backup power in case of a
power interruption or outage on the grid.

AC electricity is compatible with the utility grid. It powers our lights,
appliances, computers, and televisions.

Special appliances that run directly on DC power are available, but they can
be expensive.

Before you decide to buy a PV system, there are some things to consider:

First, PV produces power intermittently because it works only when the sun
is shining. This is not a problem for PV systems connected to the utility grid,
because any additional electricity required is automatically delivered to you by
your utility. In the case of non-grid, or stand-alone, PV systems, batteries can
be purchased to store energy for later use.

Second, if you live near existing power lines, PV-generated electricity is
usually more expensive than conventional utility-supplied electricity.

Although PV now costs less than 1% of what it did in the 1970s, the
amortized price over the life of the system is still about 25 cents per kilowatt-
hour. This is double to quadruple what most people pay for electricity from
their utilities. A solar rebate program and net metering can help make PV
more affordable, but they can't match today's price for utility electricity in
most cases.

Finally, unlike the electricity you purchase monthly from a utility, PV power
requires a high initial investment.


This means that buying a PV system is like paying years of electric bills up
front. Your monthly electric bills will go down, but the initial expense of PV
may be significant. By financing your PV system, you can spread the cost over
many years, and rebates can also lighten your financial load.



Chapter 4:

What are PV solar panels?

What do we mean by PV solar panels? The word itself helps to explain how
photovoltaic (PV) or solar electric technologies work. First used in about
1890, the word has two parts: photo, a stem derived from the Greek phos,
which means light, and volt, a measurement unit named for Alessandro Volta
(1745-1827), a pioneer in the study of electricity.

So, photovoltaics could literally be translated as light-electricity. And that's
just what photovoltaic materials and devices do; they convert light energy
to electricity, as Edmond Becquerel and others discovered in the 18th
Century.

When certain semiconducting materials, such as certain kinds of silicon, are
exposed to sunlight, they release small amounts of electricity. This process is
known as the photoelectric effect. The photoelectric effect refers to the
emission, or ejection, of electrons from the surface of a metal in response to
light. It is the basic physical process in which a solar electric or photovoltaic
(PV) cell converts sunlight to electricity.

Sunlight is made up of photons, or particles of solar energy. Photons contain
various amounts of energy, corresponding to the different wavelengths of the


solar spectrum. When photons strike a PV cell, they may be reflected or
absorbed, or they may pass right through.

Only the absorbed photons generate electricity. When this happens, the
energy of the photon is transferred to an electron in an atom of the PV cell
(which is actually a semiconductor).

With its newfound energy, the electron escapes from its normal position in an
atom of the semiconductor material and becomes part of the current in an
electrical circuit. By leaving its position, the electron causes a hole to form.
Special electrical properties of the PV cell—a built-in electric field—provide the
voltage needed to drive the current through an external load (such as a light
bulb).

A PV system is made up of different components. These include PV modules
(groups of PV cells), which are commonly called PV panels; one or more
batteries; a charge regulator or controller for a stand-alone system; an
inverter for a utility-grid-connected system and when alternating current
(ac) rather than direct current (dc) is required; wiring; and mounting
hardware or a framework.

There are four main types of solar energy technologies:

1. Photovoltaic (PV) systems, which convert sunlight directly to electricity
by means of PV cells made of semiconductor materials.


2. Concentrating solar power (CSP) systems, which concentrate the
sun's energy using reflective devices such as troughs or mirror panels to
produce heat that is then used to generate electricity.

3. Solar water heating systems, which contain a solar collector that faces
the sun and either heats water directly or heats a "working fluid" that, in turn,
is used to heat water.

4. Transpired solar collectors, or "solar walls," which use solar energy to
preheat ventilation air for a building.

A PV system that is designed, installed, and maintained well will operate for
more than 20 years. The basic PV module (interconnected, enclosed panel of
PV cells) has no moving parts and can last more than 30 years. The best way
to ensure and extend the life and effectiveness of your PV system is by
having it installed and maintained properly.

Experience has shown that most problems occur because of poor or sloppy
system installation. Failed connections, insufficient wire size, components not
rated for dc application, and so on, are the main culprits.

The next most common cause of problems is the failure of the electronic parts
in the balance of systems (BOS): the controller, inverter, and protection
components. Batteries fail quickly if they're used outside their operating
specification. For most applications (uses), batteries should be fully recharged
shortly after use.


In many PV systems, batteries are discharged AND recharged slowly, perhaps
over a period of days or weeks. Some batteries quickly fail under these
conditions. Be sure the batteries specified for your system are appropriate for
the application.

A 10% efficient PV system in most areas of the United States will generate
about 180 kilowatt-hours per square meter. A PV system rated at 1 kilowatt
will produce about 1800 kilowatt-hours a year. Most PV panels are
warranted to last 20 years or more (perhaps as many as 30 years) and to
degrade (lose efficiency) at a rate of less than 1% per year.

Under these conditions, a PV system could generate close to 36,000 kilowatt-
hours of electricity over 20 years and close to 54,000 kilowatt-hours over 30
years. This means that a PV system generates more than $10,000 worth of
electricity over 30 years.

What does energy conversion efficiency mean?

Energy conversion efficiency is an expression of the amount of energy
produced in proportion to the amount of energy consumed, or available to a
device. The sun produces a lot of energy in a wide light spectrum, but we
have so far learned to capture only small portions of that spectrum and
convert them to electricity using photovoltaics.

So, today's commercial PV systems are about 7% to 17% efficient, which
might seem low. And many PV systems degrade a little bit (lose efficiency)
each year upon prolonged exposure to sunlight. For comparison, a typical
fossil fuel generator has an efficiency of about 28%.


We're working on ways to convert more of the energy in sunlight to usable
energy and increase the efficiency of PV systems, however. Some
experimental PV cells now convert nearly 40% of the energy in light to
electricity. In solar thermal systems (like solar water-heating roof panels),
efficiency goes down as the solar heat is converted to a transfer medium such
as water. Also, some of the heat radiates away from the system before it can
be used.



Chapter 5:

Solar Power – The Converters

The regulator provides DC power at a specific voltage. Converters and
inverters are used to adjust the voltage to match the requirements of your
load.

DC/DC Converters

DC/DC converters transform a continuous voltage to another continuous
voltage of a different value. There are two conversion methods which can be
used to adapt the voltage from the batteries: linear conversion and
switching conversion.

Linear conversion lowers the voltage from the batteries by converting excess
energy to heat. This method is very simple but is obviously inefficient.

Switching conversion generally uses a magnetic component to temporarily
store the energy and transform it to another voltage. The resulting voltage
can be greater, less than, or the inverse (negative) of the input voltage.

The efficiency of a linear regulator decreases as the difference between the
input voltage and the output voltage increases. For example, if we want to


convert from 12 V to 6 V, the linear regulator will have an efficiency of only
50%. A standard switching regulator has an efficiency of at least 80%.

DC/AC Converter or Inverter

Inverters are used when your equipment requires AC power. Inverters chop
and invert the DC current to generate a square wave that is later filtered to
approximate a sine wave and eliminate undesired harmonics. Very few
inverters actually supply a pure sine wave as output.

Most models available on the market produce what is known as "modified
sine wave", as their voltage output is not a pure sinusoid. When it comes to
efficiency, modified sine wave inverters perform better than pure sinusoidal
inverters.

Be aware that not all the equipment will accept a modified sine wave as
voltage input. Most commonly, some laser printers will not work with a
modified sine wave inverter. Motors will work, but they may consume more
power than if they are fed with a pure sine wave.

In addition, DC power supplies tend to warm up more, and audio amplifiers
can emit a buzzing sound. Aside from the type of waveform, some important
features of inverters include:

• Reliability in the presence of surges.

Inverters have two power ratings: one for continuous power, and a higher
rating for peak power. They are capable of providing the peak power for a
very short amount of time, as when starting a motor. The inverter should also


be able to safely interrupt itself (with a circuit breaker or fuse) in the event of
a short circuit, or if the requested power is too high.

• Conversion efficiency. Inverters are most efficient when providing 50%
to 90% of their continuous power rating. You should select an inverter that
most closely matches your load requirements. The manufacturer usually
provides the performance of the inverter at 70% of its nominal power.

• Battery charging. Many inverters also incorporate the inverse function:
the possibility of charging batteries in the presence of an alternative source of
current (grid, generator, etc). This type of inverter is known as a charger/
inverter.

• Automatic fall-over. Some inverters can switch automatically between

different sources of power (grid, generator, solar) depending on what is
available. When using telecommunication equipment, it is best to avoid the
use of DC/ AC converters and feed them directly from a DC source. Most
communications equipment can accept a wide range of input voltage.



Chapter 6:

Solar Power - The battery

The battery "hosts" a certain reversible chemical reaction that stores electrical
energy that can later be retrieved when needed. Electrical energy is
transformed into chemical energy when the battery is being charged, and the
reverse happens when the battery is discharged.

A battery is formed by a set of elements or cells arranged in series. Leadacid
batteries consist of two submerged lead electrodes in an electrolytic solution
of water and sulfuric acid. A potential difference of about 2 volts takes place
between the electrodes, depending on the instantaneous value of the charge
state of the battery. The most common batteries in photovoltaic solar
applications have a nominal voltage of 12 or 24 volts. A 12 V battery
therefore contains 6 cells in series.

The battery serves two important purposes in a photovoltaic system: to
provide electrical energy to the system when energy is not supplied by the
array of solar panels, and to store excess energy generated by the panels
whenever that energy exceeds the load.

The battery experiences a cyclical process of charging and discharging,
depending on the presence or absence of sunlight. During the hours that
there is sun, the array of panels produces electrical energy. The energy that
is not consumed immediately it is used to charge the battery. During the


hours of absence of sun, any demand of electrical energy is supplied by the
battery, thereby discharging it.

These cycles of charge and discharge occur whenever the energy produced
by the panels does not match the energy required to support the load. When
there is sufficient sun and the load is light, the batteries will charge.
Obviously, the batteries will discharge at night whenever any amount of
power is required. The batteries will also discharge when the irradiance is
insufficient to cover the requirements of the load (due to the natural variation
of climatological conditions, clouds, dust, etc.

If the battery does not store enough energy to meet the demand during
periods without sun, the system will be exhausted and will be unavailable for
consumption. On the other hand, the oversizing the system (by adding far too
many panels and batteries) is expensive and inefficient. When designing a
stand-alone system we need to reach a compromise between the cost of
components and the availability of power from the system.

One way to do this is to estimate the required number of days of autonomy.
In the case of a telecommunications system, the number of days of autonomy
depends on its critical function within your network design. If the equipment
is going to serve as repeater and is part of the backbone of your network, you
will likely want to design your photovoltaic system with an autonomy of up to
5-7 days.

On the other hand, if the solar system is responsible for a providing energy to
client equipment you can probably reduce number of days of autonomy to
two or three. In areas with low irradiance, this value may need to be


increased even more. In any case, you will always have to find the proper
balance between cost and reliability. Types of batteries Many different battery
technologies exist, and are intended for use in a variety of different
applications. The most suitable type for photovoltaic applications is the
stationary battery, designed to have a fixed location and for scenarios where
the power consumption is more or less irregular.

"Stationary" batteries can accommodate deep discharge cycles, but they are
not designed to produce high currents in brief periods of time. Stationary
batteries can use an electrolyte that is alkaline (such as Nickel- Cadmium) or
acidic (such as Lead-Acid).

Stationary batteries based on Nickel-Cadmium are recommended for their
high reliability and resistance whenever possible. Unfortunately, they tend to
be much more expensive and difficult to obtain than sealed lead-acid
batteries.

In many cases when it is difficult to find local, good and cheap stationary
batteries (importing batteries is not cheap), you will be forced to use batteries
targeted to the automobile market.

Using car batteries Automobile batteries are not well suited for photovoltaic
applications as they are designed to provide a substantial current for just few
seconds (when starting then engine) rather than sustaining a low current for
long period of time.


This design characteristic of car batteries (also called traction batteries)
results in an shortened effective life when used in photovoltaic systems.
Traction batteries can be used in small applications where low cost is the
most important consideration, or when other batteries are not available.
Traction batteries are designed for vehicles and electric wheelbarrows.

They are cheaper than stationary batteries and can serve in a photovoltaic
installation, although they require very frequent maintenance. These batteries
should never be deeply discharged, because doing so will greatly reduce their
ability to hold a charge.

A truck battery should not discharged by more than 70% of its total capacity.
This means that you can only use a maximum of 30% of a lead-acid battery's
nominal capacity before it must be recharged.

You can extend the life of a lead-acid battery by using distilled water. By
using a densimeter or hydrometer, you can measure the density of the
battery's electrolyte.

A typical battery has specific gravity of 1.28. Adding distilled water and
lowering the density to 1.2 can help reduce the anode's corrosion, at a cost of
reducing the overall capacity of the battery.

If you adjust the density of battery electrolyte, you must use distilled water,
as tap water or well water will permanently damage the battery. States of
charge There are two special state of charge that can take place during the
cyclic charge and discharge of the battery. They should both be avoided in
order to preserve the useful life of the battery.


Overcharge Overcharge takes place when the battery arrives at the limit of its
capacity. If energy is applied to a battery beyond its point of maximum
charge, the electrolyte begins to break down. This produces bubbles of
oxygen and hydrogen, in a process is known as gasification.

This results in a loss of water, oxidation on the positive electrode, and in
extreme cases, a danger of explosion. On the other hand, the presence of gas

avoids the stratification of the acid. After several continuous cycles of charge
and discharge, the acid tends to concentrate itself at the bottom of the
battery thereby reducing the effective capacity.

The process of gasification agitates the electrolyte and avoids stratification.
Again, it is necessary to find a compromise between the advantages (avoiding
electrolyte stratification) and the disadvantages (losing water and production
of hydrogen). One solution is to allow a slight overcharge condition every so
often.

One typical method is to allow a voltage of 2.35 to 2.4 Volts for each element
of the battery every few days, at 25ºC. The regulator should ensure a
periodical and controlled overcharges. Overdischarge In the same way that
there is a upper limit, there is also a lower limit to a battery's state of charge.

Discharging beyond that limit will result in deterioration of the battery. When
the effective battery supply is exhausted, the regulator prevents any more


energy from being extracted from the battery. When the voltage of the
battery reaches the minimum limit of 1.85 Volts per cell at 25°C, the regulator
disconnects the load from the battery.

If the discharge of the battery is very deep and the battery remains
discharged for a long time, three effects take place: the formation of
crystallized sulfate on the battery plates, the loosening of the active material
on the battery plate, and plate buckling.

The process of forming stable sulfate crystals is called hard sulfation. This is
particularly negative as it generates big crystals that do not take part in any
chemical reaction and can make your battery unusable.



Chapter 7:

How to size your photovoltaic system?

When choosing equipment to meet your power needs, you will need to
determine the following, at a minimum:

• The number and type of solar panels required to capture enough solar
energy to support your load.

• The minimum capacity of the battery. The battery will need to store enough

energy to provide power at night and through days with little sun, and will

determine your number of days of autonomy.

• The characteristics of all other components (the regulator, wiring, etc.)

needed to support the amount of power generated and stored.

System sizing calculations are important, because unless the system
components are balanced, energy (and ultimately, money) is wasted.

For example, if we install more solar panels to produce more energy, the
batteries should have enough capacity to store the additional energy


produced. If the bank of batteries is too small and the load is not using the
energy as it is generated, then energy must be thrown away.

A regulator of a smaller amperage than needed, or one single cable that is
too small, can be a cause of failure (or even fire) and render the installation
unusable. Never forget that the ability of the photovoltaic energy to produce
and store electrical energy is limited.

Accidentally leaving on a light bulb during the day can easily drain your
reserves before nighttime, at which point no additional power will be
available.

The availability of "fuel" for photovoltaic systems (i.e. solar radiation) can be
difficult to predict. In fact, it is never possible to be absolutely sure that a
standalone system is going to be able to provide the necessary energy at any
particular moment.

Solar systems are designed for a certain consumption, and if the user exceeds
the planned limits the provision of energy will fail.

The design method that we propose consists of considering the energy
requirements, and based on them to calculate a system that works for the
maximum amount of time so it is as reliable as possible.


Of course, if more panels and batteries are installed, more energy will be able
to be collected and stored. This increase of reliability will also have an
increase in cost.

In some photovoltaic installations (such as the provision of energy for
telecommunications equipment on a network backbone) the reliability factor is
more important that the cost. In a client installation, low cost is likely going to
be a the most important factor.

Finding a balance between cost and reliability is not a easy task, but whatever
your situation, you should be able to determine what it is expected from your
design choices, and at what price.

The method we will use for sizing the system is known as the method of the
worst month.

We simply calculate the dimensions of the standalone system so it will work in
the month in which the demand for energy is greatest with respect to the
available solar energy. It is the worst month of the year, as this month with
have the largest ratio of demanded energy to available energy.

Using this method, reliability is taken into consideration by fixing the
maximum number of days that the system can work without receiving solar
radiation (that is, when all consumption is made solely at the expense of the
energy stored in the battery.)


This is known as the maximum number of days of autonomy (N), and
can be thought of as the number of consecutive cloudy days when the panels
do not collect any significant amount of energy.

When choosing N, it is necessary to know the climatology of the place, as well
as the economic and social relevance of the installation. Will it be used to
illuminate houses, a hospital, a factory, for a radio link, or for some other
application?

Remember that as N increases, so does the investment in equipment and
maintenance. It is also important to evaluate all possible logistical costs of
equipment replacement.

It is not the same to change a discharged battery from an installation in the
middle of a city versus one at the top a telecommunication tower that is
several hours or days of walking distance.

Fixing the value of N it is not an easy task as there are many factors involved,
and many of them cannot be evaluated easily. Your experience will play an
important role in this part of the system sizing. One commonly used value for
critical telecommunications equipment is N = 5, whereas for low cost client
equipment it is possible to reduce the autonomy to N = 3.



Chapter 8:

Before connecting a PV system to the grid

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.
However, if insurance coverage becomes an issue, contact one of the groups
listed in the Getting Help section.

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.

If your questions are not answered adequately, contact one of the groups in
the Getting Help section. National standards for utility interconnection of PV
systems are beingadopted 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 ofElectrical 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).
UnderwritersLaboratories, 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.

How do you get a netmetering agreement?

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.

What should you know about utility and inspection sign-off?

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.

What should you know about warranties?

Warranties are key to ensuring that your PV system will be repaired if
something should malfunction during the warranty period. PV systems eligible
for some solar rebate programs must carry a full (not "limited") two-year
warranty, in addition to any manufacturers' warranties on specific
components.


This warranty should cover all parts and labor, including the cost of removing
any defective component, shipping it to the manufacturer, and reinstalling the
component after it is repaired or replaced. The rebate program's two-year
warranty requirement supersedes any other warranty limitations. In other
words, even if the manufacturer's warranty on a particular component is less
than two years, the system vendor must provide you with a two-year
warranty.

Similarly, even if the manufacturer's warranty is a limited warranty that does
not include the cost of removing, shipping, and reinstalling defective
components, the system vendor must cover these costs if the retailer/vendor
also installed the system.

Be sure you know who is responsible for honoring the various warranties
associated with your system—the installer, the dealer, or the manufacturer.
The vendor should disclose the warranty responsibility of each party. Know
the financial arrangements, such as contractor's bonds, that ensure the
warranty will be honored. (A warranty does not guarantee that the company
will remain in business).

Find out whom to contact if there is a problem. Under some solar rebate
programs, vendors must provide documentation on system and component
warranty coverage and claims procedures. To avoid any later
misunderstandings, be sure to read the warranty carefully and review the
terms and conditions with your retailer/vendor.



Chapter 9:

How much will you save with your PV
system?

The value of your PV system's electricity depends on how much you pay for
electricity now and how much your utility will pay you for any excess power
that you generate.

If your utility offers net metering (and so pays the full retail price for your
excess electricity), you and your utility will pay the same price for each other's
electricity. You can use the calculation box on the next page to roughly
estimate how much electricity your PV system will produce and how much
that electricity will be worth. Actual energy production from your PV system
will vary by up to 20% from these figures, depending on your geographic
location, the angle and orientation of your system, the quality of the
components, and the quality of the installation.

Also, you may not get full retail value for excess electricity produced by your
system on an annual basis, even if your utility does offer net metering. Be
sure to discuss these issues with your PV provider.

Request a written estimate of the average annual energy production from the
PV system. However, even if an estimate is accurate for an average year,


actual electricity production will fluctuate from year to year because of natural
variations in weather and climate.

If your utility does not offer net metering, you can still use the calculation box
to determine the amount of electricity your system will produce.

However, this is not as straightforward, because the excess electricity will not
be worth as much as the electricity you actually use. You may earn only 2
cents per kilowatt-hour—or less than half the retail rate—for your excess
power. PV systems produce most of their electricity during the middle of the
day, when residential electric loads tend to be small. If your utility does not
offer net metering, you may want to size your system to avoid generating
electricity significantly beyond your actual needs.

How much does a PV system cost?

No single answer applies in everycase. But a solar rebate and other incentives
can always reduce the cost. Your price depends on a number of factors,
including whether your home is under construction and whether PV is
integrated into the roof or mounted on top of an existing roof. The price also
depends on the PV system rating, manufacturer, retailer, and installer.

The size of your system may be the most significant factor in any
measurement of costs versus benefits. Small, single-PV-panel systems with
built-in inverters that produce about 75 watts may cost around $900 installed,


or $12 per watt. These small systems offset only a small fraction of your
electricity bill.

A 2-kilowatt system that meets nearly all the needs of a very energy efficient
home could cost $16,000 to $20,000 installed, or $8 to $10 per watt. At the
high end, a 5-kilowatt system that completely meets the energy needs of
many conventional homes can cost $30,000 to $40,000 installed, or $6 to $8
per watt. These prices are rough estimates; your costs depend on your
system's configuration, your equipment options, and other factors. Your local
PV providers can give you more accurate estimates or bids.



Chapter 10:

FAQ Running Solar Power At Your Home

What can I do with the power?

Well, before you ask that question, you really need to know the answer to
this one:

What sort of power is it?

In case you didn't know, solar panels don't generate what we call "mains
electricity".

Mains is 230 Volts AC (117 Volts in the USA), while solar panels generate
about 12 Volts DC.

AC/DC – that's a heavy metal band isn't it?

Yes, but they're not the same without Bon Scott are they? AC stands for

Alternating Current and DC stands for Direct Current. The important
differences are that the voltage of an AC source can be changed by using a
transformer, whilst DC can't. On the other hand DC can charge a battery
whilst AC can't. That's why mains is always AC and car electrical systems are
always DC.

So I can't make solar power into mains with a transformer?

No, you need something called an "inverter". But you can charge a battery.

I'm on the mains. Can't I have solar power then?

Of course you can, don't worry. You can connect solar panels to the mains
using a "synchronous inverter", and sell the extra power to the electricity
company. The government may even give you a grant for doing it.

What's a synchronous inverter?

It's an electronic device that turns DC into AC and matches it to the incoming
mains.

Then, when there is extra power, it turns your meter backwards.


I'll have one, where do I get it?

Don't ask me, I do self-contained systems remember? Have a look at my links
page to find specialists who can tell you more. Ask me another question.

So what if I'm not on the mains?

You might not live in the middle of nowhere but that still doesn't mean you
can get the mains. You might need power for a caravan or boat, or a holiday
home overseas.

Maybe your garage is the other side of the main road and you can't bury a
cable. The questions are the same.

What if it's not sunny?

I reckon you know the answer by now. Charge a battery, that's what. Then,
when the sun's not shining or you need more power than the solar panels are
producing it can come from the battery. If you do it right, during the day the
battery will charge up again.

But I want mains, not battery power, don't I?

I don't know, do you? You can get a lot of 12 Volt appliances now, so you
might not need mains. Truck accessory people and the like sell them. Have a
look at my recommended products and links for more information. If you
really do need 230 Volts AC you can use an "inverter".

That's the thing that sells electricity isn't it?

That's a synchronous inverter, this is a bit different. Instead of being
connected to the solar panels, a stand-alone inverter is connected to the
battery. It does the same sort of thing except it generates its own "mains"
power. Solar power answers has a page all about inverters.

So, a solar panel, a car battery and one of these inverter things
then?

If you like, but it won't work very well or for very long. You see, there
probably won't be the right amount of power, and the battery won't last very
long. To understand more, let me show you how to design a solar power
system.


How To Power Your

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