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PhotovoltaicSystemsTraining

Session6 Off

grid

installations

http://www.leonardo-energy.org/training-pv-systems-design-

construction-operation-and-maintenance

JavierRelancio&LuisRecuero

GeneraliaGroup

October6th 2010


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PHOTOVOLTAICSYSTEM

Design,Execution,Operation&Maintenance

STANDALONEFACILITIES

JavierRelancio.GeneraliaGroup. 06/10/2010

www.generalia.es2

http://www.leonardo-energy.org/training-pv-systems-design-construction-operation-and-maintenance


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INDEX

Introduction

Elements. Storage System & Backup System

Trends: Hybrid Systems. Efficiency. Smart Grids

Applications. Examples

Design

Maintenance

3http://www.leonardo-energy.org/training-pv-systems-design-construction-operation-and-maintenance


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INDEX

Introduction




Design

Maintenance



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5

B a s ic t o p o l o g y

PV modules

PV regulator

Inverter

DC Consumption

AC Consumption



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Differences with a grid connected system

Designed for self-consumption

An electricity storage is required

Regulator / charger

Batteries

Inverters with capacity " to create a grid"

For facilities with consumptions in DC and output power below 2 kW, we may require modules

with particular characteristics:

If the consumptions are in DC 12 V, modules of 18 V

If they are in DC 24 V, modules of 30-32 V

NOTE: The modules of 12 V are more expensive, but it is possible to avoid their use by using

regulators with power maximizers. Only for powers over 2 kW

6

I n t r o d u c t i o n



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Criterion of winter production maximization VS annual production maximization

In the grid connected facilities, the objective is to obtain the maximum annual profitability of

the installation

In stand-alone facilities, the objective is to feed the demand for any day of the year. For it:

We have to design the installation for the " worse day of the year "

We will choose the modules tilt that maximizes the production in the above mentioned

month

7

I n t r o d u c t i o n

Sofia,Bulgaria Madrid,Spain

Ed(32) Ed (61) Ed(34) Ed (60)

Jan 1,65 1,79 2,66 2,96

Feb 2,25 2,34 3,05 3,19

Mar 2,75 2,63 4,32 4,23

Apr 3,42 3,01 4,1 3,63

May 3,61 2,95 4,63 3,75

Jun

3,79 2,97 4,78 3,69

Jul 4,06 3,23 4,91 3,85

Aug 3,95 3,37 4,79 4,08

Sep 3,48 3,28 4,38 4,14

Oct 2,68 2,74 3,54 3,63

Nov 1,71 1,84 2,66 2,9

Dec 1,3 1,41 2,15 2,39

Totalyear 1050 960 1400 1290

0

1

2

3

4

5

6

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Sofia,Bulgaria(32) Sofia,Bulgaria(61)

Madrid,Espaa

(34) Madrid,

Espaa

(60)

N o t e : we can use backup system for the worst production months


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INDEX

Introduction




Design

Maintenance



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Inverter

Lower range of powers than for grid connected facilities

Possibility of connection in parallel or series

Prepared for auxiliary inputs in parallel, in case of hybrid systems:

diesel, grid, modules

Manufacturers:

9

El e m e n t s

Manufacturer Power (per unit) System Power Observations

Xantrex 6 kW 36 kW

It integrates a battery charger It allows to inject surplus to the grid It allows different configuration modes for themanagement of the generation and the consumption

Victron 10 kVA100 kVA(90 kW)

It integrates a battery charger It allows different configuration modes for themanagement of the generation and the consumption

Ingeteam 15 kVA 120 kVA It integrates a battery charger It allows different configuration modes for themanagement of the generation and the consumption



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Regulator / Charger

It is used to:

... protect the batteries against overcharging

To avoid excessive discharges within a cycle

It is recommended to work with a oversizing of 125 %

Differences between regulator and charger

Charger: it is only used to charge the batteries

Regulator: it is used both for charging the batteries and

managing the loads in DC

10

El e m e n t s

NOTE : The chargers are not simple devices:

The battery charge stage depends on many factors and is difficult to determine

Multiple algorithms exist to optimize the battery charging and to increase its

lifetime



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Introduction

Batteries are used for storing the energy that is produced by the

modules during the day, for being consumed in the periods that

there is no solar irradiation

This storage takes place due to chemical reversible reactions

11

B a t t e r i e s

A battery is composed by the connection of several "cells in series

Between the electrodes there is a certain potential difference (Generally: 2V)

In photovoltaic applications we can generally find batteries of 12, 24 or 48 volts

Normally, the system is designed to store energy for several days of consumption

In case of several days of low irradiation: clouds, rain, etc

Three days can be a good recommendation, depending on each case



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Real capacity

12

B a t t e r i e s

Capacity

Electricity that can be obtained during a full discharge of a completely charged battery

The capacity, in Amperes - hours (A - h), is the current that the battery can supply,

multiplied by the number of hours in which the above mentioned current is delivered

Theoretically, a battery of 200 A - h might supply: 200A during an hour, 100A for two hours,1A for 200 hours and so on.

However, in the reality, the capacity of the battery will change according to the regime of

charge and discharge. (Generally, lower speed of discharge implies a bigger capacity)

For example: a battery which specifies a capacity of 100 A - h during 8 hours (C-8):

It might supply 12,5 A during 8 hours. C = 12.5 x 8 = 100 A - h

But it might provide 5.8 A during 20 hours. C ' = 5.8 x 20 = 116 A - h



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Depth of discharge

B a t t e r i e s

Percentage of the total capacity of the battery that can be used without need of rechargeand without damaging the battery.

As a general rule, the less depth of discharge is reached in every cycle, the longerthe battery lifetime will be

Classification:

Several manufacturers

Isofoton, Hoppecke, BAE, TABB, Tudor, etc

Lightcycle Deep

cycle

Designedforhighcurrentintheinitial

discharges

Constantchargesanddischarges

Depthsofdischargelowerthan20%

Designedforlongperiodsofutilizationwithout

beingrecharged

Theyaremorerobustandhavehigherenergetic

density

Depth

of

discharge

around

of

80

%'

Note: This classification is generally used for Lead-Acid batteries


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Type of batteries

B a t t e r i e s

For photovoltaic applications the most suitable batteries are the stationary ones, designed tohave a fixed emplacement and for the cases in which the consumption is more or lessirregular. The stationary batteries do not need to supply high currents during brief periods of

time, but they need to reach deep discharges

Lead Acid(deep cycle)

Lead Acid(light cycle)

Gel-Cell NiCad

Observations High commercialavailability

Sudden death couldhappen

They aremanufactured withlead antimony

High commercialavailability

Sudden death couldhappen

They are manufacturedwith lead - calcium

The acid is in gelstate

They need lessmaintenance

They can operate inany position

They are moreexpensive than leadbatteries

Better performancewith high temperature

They cost the doublethan Lead Acidbatteries

Discharge depth 40-80% 15-25% 15-25% 100%

Self discharge per month 5% 1-4% 2-3% 3-6%

Typical capacity (Ah/m3) 35,314 24,720 8,828 17,660

Capacity range (Ah/m3) 7,062 to 50,323 5,791 to 49,000 3,672 to 16,400 3,630 to 34,961

Typical capacity (Ah/Kg) 12.11 10.13 4.85 11.10

Capacity range (Ah/Kg) 4.18 to 26.65 2.42 to 20.26 2.20 to 13.87 2.64 to 20.90

Minimal temperature (oC) -6.6 -6.6 -18 -45


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The diesel generator as a backup (I)

The use of a diesel generator can allow us to avoid the oversizing of solar modules

and batteries.

The diesel generator would cover the periods of low irradiation or the situations of

extraordinary consumption

Nowadays, the energy generated by a diesel group can be more expensive than

the energy obtained from a photovoltaic solar system

It will depend on the price of the fuel in each country

NOTE : In the following slide we can find an example

15

D i e se l g e n e r a t o r



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16

N o t e s :

1. For this study we have considered that the price of the electricity from a Diesel Generator is, today, 0.35 perkWh (Including the costs that the logistics of the fuel supposes).

2. The study has considered a radiation of 1500 HSP3. In the graph we can find, in green, an estimation of the repercussion that would suppose the extra charges for

the emission of pollutant gases (Price of ton of CO2).4. The prices are in Euros

5. The word "hybrid" refers to a photovoltaic installation with a diesel generator as a backup.

0,20

0,40

0,60

0,80

1,00

1,20

1,40

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

PreciokWhhibrido PreciokWh GDiesel PreciokWh GDieselCO2

Price per kWh: Diesel generator VS Solar Facility

D i e se l g e n e r a t o r



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INDEX

Introduction




Design

Maintenance



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18

H y b r i d Sy s t e m : D ie se l - So l a r

PV modules

PV regulator

Inverter

DC

Consumption

ACConsumption

The chosen diesel generator must have

automatic starter:

Using its own electronic starter to

automatically switch on when an auxiliary

signal is received

Using an external electronic starter

specially designed for this function

The generator is connected to the AC BUS

The diesel generator is automatically switched on if

the batteries are under a certain level

The generator can produce energy exclusively to

supply the consumption or, also, to charge the batteries

The inverter has to be specially designed with

this function (AC/DC Converter)



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19

H y b r i d Sy s t e m : W i n d - So l a r

Thewindpotentialisdeterminedby:

Speedofthewind:thekineticenergyofthewind

increasesaccordingtothecubeofitsspeed

Windresourcesbecomeexploitablewhere

averageannualwindspeedsexceed45m/s

Alsoitisinfluenced,toalesserextent,bythe

characteristicsanddensityofthewind

This type of system is currently being studied on the R&D departments of manyinstitutions and companies.

Good correlation between the wind and the solar resource

Generally, the wind & solar systems are connected to the DC BUS (of the batteries)

There is not too much information about the wind resource

The guarantees for the wind system are lower than for the PV system

Average, three years

Description


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Windgenerator

20

H y b r i d Sy s t e m : W i n d - So l a r

PVmodules

PVregulator

Inverter

DC Consumption

AC Consumption

Windregulator

Topology

DC BUS



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21

Ef f i c i e n c y i n t h e c o n s u m p t i o n ( I )

The importance of reducing the consumption

Nowadays, we can find great evolutions in the consumption reduction of many

massive devices: electrical appliances, lighting, air conditioning, PCs, etc

Considering the high initial investment per kWp for an isolated solar system

and considering the dependency between this peak power and the consumption

every stand alone solar facility should begin by the

optimization of its consumption efficiency

Ex am p l e :

Electricity price: 0,40 per kWh

Fridge consumption A+ Class: 150 kWh/year

Fridge consumption G Class: 800 kWh/year

Saving: 260 per year

* If we reduce our energy consumption, installing a more efficientdevice, we will be able to reduce the price of our solar PV Facility

Source: IDAE


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22

Co n s u m p t i o n e f f i c i e n c y ( I I )

Examples

ElementLow

consumption

Ordinary

consumption

FridgeClass A

150 kWh/yearClass G

800 kWh/year

WashingMachine

Class A1.42 kWh

Class G6.9 kWh

Lighting 1 Incandescent100 W

LED10 W

Lighting 2Incandescent

100 WLow Consumption

18 W

PC(Desktop)

250 W 70 W

Energy

class

Energy

consumption Evaluation

LOW

MED

HIGH

Less efficient

More efficient


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23

Sm a r t Gr i d s ( I )

Global objective

To success:

Increase the integration of renewable

energies in the Global electric grid The need of dealing with an

intermittent & distributed generation

International governments commitment (such as the EU)

Minimize the environmental impact.

Reduce the CO2 emissions

Reduce the dependency from fossil fuels

Increase the use of Renewable Energies

Reduce costs & Increase the energy efficiency


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Sm a r t Gr i d s ( I I )

Improve the control & supervision of the generation

Intermittent generation profile of the Renewable Energies

Low forecast on the production

Improve the demand management

High peakvalley ratio

Low correlation with renewable production

Mechanisms towards the smart grids

Improve the international grid connection

Improve the electricity storage

New facilities to pump water and then produce energy

R&D for new in situ storage systems: hydrogen/ batteries

The electrical vehicle

Source: REE

Demand profile for anaverage day in Spain



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INDEX

Introduction




Design

Maintenance



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Zones distant from the grid

Zones currently supplied by diesel generators

Exceptionally, areas with instabilities from the grid

26

A p p l ic a t i o n A r e a s

Gr e a t p o t e n t i a l i n

A f r i ca n c o u n t r i e s

Especially, areas withhigh fuel prices

Source: World energy outlook 2009



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Single family houses

Public buildings: hospitals, schools, etc

Public lighting and traffic lights

Communication Stations

Water pumping

For human consumption

For agriculture

Desalination & Water sewerage

Industrial uses

27

A p p l i c a t i o n e x a m p l e s



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Great advantages to be fed with solar

energy:

There is no need for batteries

The construction of a high water tank

can be used as a energy storage

Therefore we do not need regulator

either

Neither inverters

Nowadays, we can find great quality

DC bombs

Installation with few elements:

We reduce the price of the installation

We reduce the possibilities of

breakdown

28

P a r t i c u l a r c a se :

W a t e r p u m p i n g f a c i l i t i e s



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Limits on the system

Maximum power output

It is limited by the inverters: nowadays


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INDEX

Introduction




Design

Maintenance



31/41

We begin by creating a table with all the consumptions we will find in the system

31

Sy s t em d e s i g n ( I )

Device Numberof

UnitsPeak

Power(W)Average

Power (W)Hours of

usage

(hperday)Consumed

energy

(Whperday)

Lamp 10 11 88* 8 880

PC 1 300 150 6 900

Fridge 1 1000 400 24 9600TV 1 90 90 8 720

TOTAL 1500W 728W 12.100 Whperday

The peak power will affect the inverter calculation

The daily energy consumption will affect:

The storage system

The solar modules

Study of consumptions

* Simultaneity ratio 80%



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According to the consumption study, we have to produce 12.100 Wh per day (average)

As we have explained previously, this production must be guaranteed even the worst

day of the year, in this case, in December

32

Sy s t e m d e s i g n ( I I )

Solar generator calculation

Madrid,Espaa

Ed*(34) Ed* (60)

Jan 2,66 2,96

Feb 3,05 3,19

Mar 4,32 4,23

Apr

4,1 3,63May 4,63 3,75

Jun 4,78 3,69

Jul 4,91 3,85

Aug 4,79 4,08

Sep 4,38 4,14

Oct 3,54 3,63

Nov 2,66 2,9

Dec

2,15 2,39Totalyear 1400 1290

We have to consider the losses in all the elements of the system:

modules, inverters, chargers, batteries and cables.

The battery losses can be estimated around 15 %

The whole system losses, can be estimated around 34 %

WLossesHSP

EnergyP demandedsolar 85,670.7

66,039,2

12100=

=

=

We could install, for example:

34 modules of 230 W = 7.820 Wp

*Ed: Average daily electricityproduction for 1kWp



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According to the consumption study, the batteries should supply 12.100 Wh/day (average)

In this example, the system will consider that the batteries have to be able to store energy

for two days without solar radiation

The batteries, then, should be able to store 24.200 Wh

For this example, we will choose Lead-Acid batteries, with a Cycle-Depth of 80%

In order to increase the battery life-time, we will consider a maximum dischargedepth around 60 %

We will consider the battery losses around 15%.

33

Sy s t em d e s i g n ( I I I )

Battery calculation

hACapacity hA =

=

=

12.19772485,06,0

212100

VoltageLossesdepthDischarge

daysnEnergydemand

Conclusion: 12 batteries of 2000 A-h (C-20)



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Now, we have to consider the peak power of the system

In this case, the maximum power would be 1500 Wp

However, usually we use a Simultaneity Ratio, because normally all the devices will

not be connected at the same time

Furthermore, the inverters are prepared to supply the double of their nominal output

power, during a certain period of time

34

Sy s t em d e s i g n ( I V )

Inverter calculation (I)

In this case, we will consider that thepeaks from the washing machine and

the fridge will not be longer than theseperiods



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We will reach a maximum output power of 1500 Wp, so the Nominal Output

Power should be higher than 750 Wp

Considering the average consumptions, and applying a Simultaneity Ratio of

80% for the lights, t h e n o m i n a l O u t p u t P o w e r o f t h e i n v e r t e r sh o u l d b e h ig h e r

t h a n 7 2 8 W p

35

Sy s t e m d e s i g n ( V )

Inverter calculation (II)

So, we will choose any inverter with a Nominal Output

Power higher than 750 Wp



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Demanded energy: 12.100 Wh

Solar modules peak power: 7.820 Wp

Batteries capacity: 2.000 A-h (C-20) x 24 V = 48.000 W-h

Inverter nominal output power: 750 1000 Wp

36

Sy s t em d e s i g n ( V I )

Conclusions

We have considered that the consumption is homogeneous during the year

If this was not the case (For example, if we had an air conditioning system) we

would have studied also the maximum demanding day

We could reduce the amount of batteries, by reducing their autonomy or increasing

their discharge depth and introducing a diesel generator as a backup for the periods

that the batteries cannot assume

Observations



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INDEX

Introduction




Design

Maintenance



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Periodical cleaning of the modules

Depending on the pollution of each area

Generally, once per year

Checking the cables and connections

Retightening the screws

Checking the structure

If it is not protected against open air (aluminum, galvanized steel, etc) it will

require a periodical antioxidant paint

Checking any shadowing effect

38

So l a r m o d u l e s m a i n t e n a n c e



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The battery is a dangerous element, due to its chemical and electrical properties

39

B a t t e r i e s m a in t e n a n c e ( I )

Main risks

The electrolyte is, generally, dilute acid: it may

produce burns if contacting the skin or the eyes

Electrocution risk

From 24 V, in wet environments

From 48 V, in dry environments

Risk of fire or explosion

The batteries produce hydrogen gas

An appropriate ventilation system is needed

Recommendations:

Use appropriate gloves and shoes

Use plastic handle tools Avoid wearing any metallic object

Avoid sparks and flames close to the

batteries



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40

B a t t e r i e s m a in t e n a n c e ( I I )

Main tasks

Checking that the room is well ventilated and protected against the sun light

Checking that the electrolyte level is between the manufacturer limits

Add only distilled water

Except for Gel type batteries

Protecting the connection terminals with antioxidant grease to avoid sulfurizing

Checking the tightness of the battery connections

Cleaning the battery covers and terminals


En d o f Se s s io n 6


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41

En d o f Se s s io n 6

http://www.leonardo-energy.org/training-pv-systems-design-

construction-operation-and-maintenance

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