How to Power Your Home for Free - eBook

8/9/2019 How to Power Your Home for Free - eBook

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Yoni Levywww.RunGreenPower.com2010

How To PowerYour Home For

Free?

By Yoni Levy

2010


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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


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Chapter 1:

Turning Sunlight Into Electricity!

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.

S
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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!


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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


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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


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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


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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.



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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 pollutionfrom 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:
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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.


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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 ofphotons, or particles of solar energy. Photons containvarious amounts of energy, corresponding to the different wavelengths of the


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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 cella built-in electric fieldprovide 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.
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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.


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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%.


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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.

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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 conversionand

switchingconversion.

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 theinput voltage and the output voltage increases. For example, if we want to
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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


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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.



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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


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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


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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 thestationary 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.


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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.


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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 maximumcharge, 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 25C. 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


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energy from being extracted from the battery. When the voltage of the

battery reaches the minimum limit of 1.85 Volts per cell at 25C, 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.



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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, thebatteries should have enough capacity to store the additional energy


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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.


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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 ofthe

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, reliabilityis 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.)


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This is known as the maximum number of daysof 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.



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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).


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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


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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:


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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 forwardwhen


34/41


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 intothe building, the other to

measure the flow of electricity out ofthe building.

If net metering is not available, the utility will pay you only a wholesalerate

for your excess electricity.


35/41


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 toqualify 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.


36/41


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 otherwords, 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 systemthe 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.



37/41


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,


38/41


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-houror less than half the retail ratefor 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,


39/41


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.



40/41


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 tothis one:

What sort of power is it?

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

Mains is 230 Volts AC (117 Volts in the USA), while solar panels generateabout 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 importantdifferences are that the voltage of an AC source can be changed by using atransformer, whilst DC can't. On the other hand DC can charge a batterywhilst AC can't. That's why mains is always AC and car electrical systems arealways 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 mainsusing a "synchronous inverter", and sell the extra power to the electricitycompany. 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 incomingmains.

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


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

Don't ask me, I do self-contained systems remember? Have a look at my linkspage 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 youcan get the mains. You might need power for a caravan or boat, or a holidayhome overseas.

Maybe your garage is the other side of the main road and you can't bury acable. 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 areproducing it can come from the battery. If you do it right, during the day thebattery 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 youmight not need mains. Truck accessory people and the like sell them. Have alook at my recommended products and links for more information. If youreally 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 beingconnected to the solar panels, a stand-alone inverter is connected to thebattery. 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, thereprobably won't be the right amount of power, and the battery won't last verylong. To understand more, let me show you how to design a solar powersystem.

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