Multi media web site and e-learning Platform October 06-2009 Rome SOLAR THERMAL : BASIC PRINCIPLE,...

Multi media web site and e-learning PlatformOctober 06-2009 Rome

SOLAR THERMAL : BASIC PRINCIPLE, MARKET,

BARRIERS AND EUROPEAN STANDARD

V.S.SHARMA

e-mail: [email protected]

Research Centre Trisaia, ItalyResearch Centre Trisaia, Italy

Solar thermal:basic principle, market, barriers and european standard

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• There is no doubt that the use of new kinds of energy - more durable and less damaging to the environment than burning fossils - will gradually grow in the future. Such progressive change will be driven by (1) the likely inability of fossils to sustain the full extent of the future energetic demand, growing roughly at the rate of +2.5 %/year world-wide, without large price increases due to progressive scarcity introduced by the demand, and (2) the growing evidence for the triggering of a major climatic change, primarily due to continued use of fossils.

• There are apriori only two types of primary energy sources which have both the energetic potentials and the durability sufficient to match mankind’s future needs: (1) Nuclear energy (fission and fusion) and (2) Sun-derived energy. The pro and cons of the first are well known whereas for the latter, a very substantial and renovated effort toward the realisation of demonstrative, large scale systems with innovative characteristics, are needed.


3

TRADITIONAL CLASSIFICATION OF RENEWABLES

Solar energy can be used either directly (heat, PV, etc.) or indirectly,through its effects on generating wind, rain (hydro-) or vegetation growth (biomass).

DIRECT INDIRECT

HYDRO BIOMASS OTHERSWINDSOLAR PV

THERMO

CHEMICAL

BIO

CHEMICAL

HIGH TEMP.

(> 300 °C)

MED. TEMP.

(100 °C – 300 °C)

SOLAR THERMAL

LOW TEMP.

(< 100 °C)


4

The modern Active Solar Systems market began as a consequence of the

oil crisis in the 1970’s.• Many companies were created World-wide to manufacture, sell and

install a series of new products, principally for heating water in private houses, public buildings and swimming pools. This enthusiastic and dynamic commercial activity was backed up by government sponsored research and development projects

• Great hopes were built on a steadily growing market. However, by the mid-1980s the situation changed, oil prices started to fall and the public fear of a conventional energy shortage slowly died out.

• The solar industry suffered badly and the majority of the newly formed companies disappeared. Those that manage to survive improved their products, re-organised production methods and introduced quality controls in order to satisfy more exacting customer demands.

•

arriers and european standard


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• Until now and with the exception of conventional hydro- and traditional wood-burning (mainly in developing countries), sun-related energies have represented only a very tiny fraction of fossil derived energies.

• In order to reverse this situation, solar energy must become more cost-competitive and more responsive to the actual demands of the market.

• We believe that such a goal can be achieved only with the development of a number of new technologies, which are an absolutely crucial premise to a more widespread use of solar energy.

• It is in this context, that all important aspects both technical and economic that could help solar thermal technology to reach its potential, are outlined in the present communication. A brief discussion about the European level quality mark (based on the European standards for solar thermal collectors and solar water heating system) accepted by all subsidy schemes, i.e. “Solar Keymark”, will also be a part of this presentation.


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The use of energy in the form of heat is one of the largest items in the energy budget. Under ordinary but favourable conditions, direct solar light has a peak power density of about 0.1 Watt cm2 , sufficient to produce warm water or house heating.

In Europe, for instance, it accounts for around 50% of total energy consumption: around 630 million toe, of which 383 in low-temperature heat and 247 in medium and high-temperature heat.

Today, low-temperature (<100oC) thermal solar technologies are reliable and mature for the market. World-wide, they help to meet heating needs with the installation of several million square metres of solar collectors per year. These technologies can play a very important role in advanced energy saving projects, especially in new buildings and structures.


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SOLAR COLLECTORS

Solar thermal:basi principle, market, barriers and european standard

The conventional collector is the core element of a solar system for DHW or space heating

Low temperature panels supply the carrier fluid at a temperature usually lesser than 80 °C

Differently from concentrating collectors, conventional solar panels work with both direct and diffused irradiation, thus producing hot water in cloudy days also

Two large families:

Unglazed collectors Glazed collectors

v


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GLAZED COLLECTORSWORKING PRINCIPLE: THE PANELS TUBES, IN WHICH THE CARRIER FLUID FLOWS, ARE IN THIS CASE PROTECTED BY A SINGLE OR MULTIPLE TRANSPARENT COVERING, MADE OF GLASS OR PLASTIC, THUS IMPROVING THE PERFORMANCES THANKS TO THE GREENHOUSE EFFECT

Most common type:

flat plate collector


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UNGLAZED COLLECTORSWorking principle: the water, flowing into the panels tubes, is instantly heated by the sunbeams and then sent to a storage tank or even directly to the final user

LOW COST EASY TO INSTALLSURROUNDINGAIR TEMPERATURE > 20 °CREQUIRED TEMPERATURE FOR WATER < 50 °CSUMMER USES (CAMPING, HOTELS, SWIMMING POOL, ETC.)


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GLAZED COLLECTOR BASIC PRINCIPLE

A glazed collector acts basically as a greenhouse:

Absorber

Infr

ared

Radia

tion

Solar

Spec

trum

Covering

The incident solar radiation is for the most part transmitted through the cover (the transmittance of a single glass cover is over 90%) and then trapped by the absorber.

The absorber plate warms up and emits in its turn radiant energy, but in the infrared spectrum, regarding which glass proves to be nearly opaque (greenhouse effect).


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TUBULAR COLLECTORS


An advanced type of glazed collector:

Tubular collector

In this type of collector, the absorber strip is located in a pressure proof glass tube.

The heat transfer fluid flows through the absorber directly in a U-tube or in counter-current in a tube-in-tube system.

In case superior performances are required, the air, between the glass tube and the absorber inside it, is aspirated (evacuated tubular collector).


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SOLAR SYSTEMS FAMILIES: FACTORY MADE

“FACTORY MADE” SYSTEMS”

Pre-assembled by the manufacturer

Natural circulation (thermosyphon)

Single family

Total area typically 4 m²


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ENERGY LOSSES IN A GLAZED COLLECTOR

• given by (1 - )

• possible reduction is limited

• at least 1520% for a flat plate glazed collector

• roughly proportional to T

• increases dramatically when difference in temperature is high

• explains the use of ETC in severe climates

typically when T is around 80 °C thermal loss is equal to absorbed

irradiation (stagnation point)

Energy supplied to the fluid

Solar irradiation on collector area

Optical loss

Thermal loss


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OPEN AND CLOSED LOOP SYSTEMS Open loop system for non-

freezing warm climates (danger of freezing is not present (Greece, Israel)

Carrier fluid in the collectors is the same of the user

Simplicity and economy are this system's advantages.

Greater efficiency because there is not the additional loss due to heat exchanger

Closed loop systems for continental climates (from Italy going to North:

an anti-freeze solution is added to the carrier fluid which is different from the stone that goes to the consumer

Greater cost and volume

no build-up of scaling in the collector.


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INTEGRATED COLLECTOR STORAGEThe ICS system, also called batch water heater, is a not much widespread type of passive system. The water is produced and stored inside the collector.

main remarks

suitable only for mild climates where there is no risk of freezing

efficient heat transfer to the water

superior simplicity, compactness, and economics

unfavourable heat loss coefficient

profitable storage only in the very short term

typically used as a pre-heater to an existing gas or electric water heater


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THERMOSYPHON SYSTEM circulation of the carrier

fluid is provided solely by the heating of the same, which implies a reduction in its density thus generating a convective flow towards the top (passive systems with no moving parts)

natural circulation of the carrier fluid must be facilitate by placing the storage tank in a higher position than the collector

are usually characterised by a limited size (2 - 4 m²) and commercialised as "factory made" systems

generally back-up is electric and integrated in the storage tank


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FORCED CIRCULATION SYSTEM

1. Collector - 2. Storage Tank - 3. Heat exchanger - 4. Control Unit - 5. Expansion Vessel - 6. Back-up Heater - 7. User

• circulation of the carrier fluid is provided through a pump run by a differential thermostat when T between the fluid out from the collectors and the water in the tank is 510 °C

• are mostly utilised when the positioning of the tank over the collectors is not possible or the length of the piping is excessive for achieving a natural circulation of the carrier fluid

• normally are intended for multi-family houses and commercialised as "custom built" systems

• the back-up can be a gas or oil heater with an additional tank in series


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COMPONENTS OF A PLANT A plant for low temperature heat application using solar energy is comprises of:

1) system for collection and transfomation of energy

2) Storage tank

3) Hydraulic circuit

4) System for integration

cold water

Auxilliary heater

Mixer

Thermosyphon Radiator

70 °C

20 °C

Heat exchanger

shower

Differential exchange of control and regulation

Flat plate orevacuated tubularcollectors

Stratified distributor


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SOLAR SYSTEMS FAMILIES: CUSTOM BUILT

“Custom Built” Systems

Assembled with properly chosen components

Forced circulation (pumped)

Collective users

Total area usually > 10 m²


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SOLAR THERMAL TECHNOGY IN EUROPE

The solar thermal market in the EU and Switzerland showed a strong performance in 2008: It grew by 60% to 3,3 GWth of new capacity (4,75 mil m2 of collector area). While the biggest push clearly came from the German market which more than doubled, demand for solar thermal technology grew strongly also in smaller markets. While in comparison the Austrian growth rate of 24% seems almost modest, newly installed capacity per capita now reached 29 kWth per 1 000 - beaten only by Cyprus’ 61 kWth per 1 000 capita.At the individual country level, Germany continues to have the biggest capacity of 1,5 GWth (2,1 mil m2 of collector area).

Spain with over 300 MWth (434 000m2) newly installed capacity is the second in the EU in 2008.

In Italy, too, compared to 2007, the market increased by 28% resulting into newly installed capacity (421 000m2 of solar thermal collectors).

French solar thermal market increased by 18% to 272 MWth (388 000m2).

In 2008, the newly installed capacity, in Austria, increased to 243 MWth (ca. 350 000 m2), 24% more than in 2007.


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SOLAR THERMAL: TECHNICAL STATUS

• Systems for heating Domestic Hot Water and swimming pool heating have been on the market for the past 20 years and the systems are mature.

• System design, sizing and maintenance issues have now been resolved for larger scale systems for heating Domestic Hot Water (DHW). Although large scale systems have been installed in most European countries, in many countries, larger systems are not widespread yet.

• Space heating is being used in Austria and is starting to be implemented by self build groups. However, in the majority of countries there is a low level of use of space heating, primarily due to the less favourable economics. District heating has been demonstrated successfully in Denmark and Sweden.

• Cooling and industrial process heating applications are being developed. Both of these applications have been experimented successfully in Southern Europe.

n standard


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SOLAR THERMAL (MARKET BARRIER)

INFORMATION PRICE DISTORTION

ENVIRONMENTAL BENEFITS


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INFORMATIONImportance of this barrier varies from country to country, depending ( as would be expected) on the promotion of the technology within the individual country.

In general, information sources are available for decision makers to enable them to reach a decision to invest in solar water heating.

However, there is also a lack of public awareness of the technology, which should be addressed by information campaigns for the general public and professionals.

There appears to be a high level of knowledge about solar systems in Denmark, the Netherlands and Sweden.

In some countries, information dissemination is needed to combat a reputation for low quality which had spread in the early days.


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PRICE DISTORTIONActive solar systems have to compete with conventional energies for which the environmental costs are not fully reflected in overall energy costs. Conventional energy therefore appears to be cheap compared with active solar heating.

Because a simple economic comparison doesn’t reflect environmental advantages of using active solar in comparison to cheap conventional fuels, an introduction of measures such as CO2 taxes would help to even

out this imbalance. Countries such as Sweden, Denmark, and the Netherlands are addressing the issue.

In several EU countries, the selling of solar heating systems involves high Active solar systems have to compete with conventional energies for which the environmental costs are not fully reflected in overall energy costs. Conventional energy therefore appears to be cheap compared with active solar heating.

Because a simple economic comparison doesn’t reflect environmental advantages of using active solar in comparison to cheap conventional fuels, an introduction of measures such as CO2 taxes would help to even

out this imbalance. Countries such as Sweden, Denmark, and the Netherlands are addressing the issue.

In several EU countries, the selling of solar heating systems involves high marketing costs per system due to the small size of the market and the lack of awareness amongst the general population. High marketing costs contribute to the overall system prices and as a result the economics of the solar heating systems be unattractive. marketing costs per system due to the small size of the market and the lack of awareness amongst the general population. High marketing costs contribute to the overall system prices and as a result the economics of the solar heating systems be unattractive.


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ENVIRONMENTAL BENEFITS

Solar thermal heating produces no emissions during operation but some

very small levels of emissions are produced during the manufacture and

installation of components and systems.


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LEVEL OF EMISSION

Parameter Value

Emission-CO2 (kg/TJ) 0 Emission-SO2 (kg/TJ) 0Emission-NOx (kg/TJ) 0Emission-particulate (kg/TJ) 0

Emission during construction-(CO2 kg/TJ) 3580-10502 Emission during construction-(NOx kg/TJ) 12 – 35

Emission during construction-(particulate kg/TJ) 0.8 – 2.4


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SOLAR THERMAL (EU COMPETITIVENESS)

The European manufacturers of solar systems and materials are producing internationally

competitive products.

The imports from non-EU countries are limited, mainly from Israel, Australia, Japan and Canada,

while there is an export trend to non EU countries.

Solar thermal market in Europe and the Mediterranean countries represents potential

World market.

Principal exporters in the world are Japan and Australia. Greece is the largest exporter of

collectors within the EU.


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SOLAR THERMAL (EU COMPETITIVENESS)

The industrialised countries should act as examples for the economically developing “sun-belt” countries, where active solar systems could play a much more important role. These countries are more important destinations for the technology than ‘well developed’ energy economies. This could have a major impact on the realisation of the world-wide active solar potential.

The current market for active solar systems appears to be particularly suited to SMEs. There are about 150 manufacturers of solar collectors in Europe. With further development of market larger companies may become interested in technology.


29

SOLAR THERMAL: CURRENT R&DR&D involvement differs in the

different EU countries. Countries -Strong involvement and financial funding of government and private companies - Involvement mainly by private companies - No involvement

Austria, Finland, Germany, Greece, Netherlands, Italy and the UK have governmental programs to promote solar thermal heating in all steps of development up to deployment, whereas in Denmark mainly the companies are involved in R&D funding. Some EU countries are leading a JOULE/THERMIE project for development of various components and equipment for solar air conditioning. iple, market, barriers and european standard


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SOLAR THERMAL – FUTURE POTENTIAL

Solar energy is available in all EU countries and the quantity of heat that can be collected with the current technology can contribute significantly to the total energy consumption. Even in a country like Greece, with relatively well established

solar water heating market, still there exist a large unexplored potential.

World deployment of solar heating systems is expected to increase up to 100 million m2 or an energy contribution of 50

TWh/year (4.3 M.toe) by 2010 whereas the expected deployment in Europe by 2010 is 20

million m2 collector area, i.e. nearly 10 TWh/year or 0.9M.toe).


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Solar Thermal – Future Potential

The more expensive systems, which have taken an increasing share of the market in Northern Europe since the late 1980’s,

employ larger collector areas and/more sophisticated evacuated collector.

For climate related reasons, the prices of the larger and more sophisticated systems used in Northern Europe will never fall as low as those used in the South, but it is nevertheless expected that the prices of systems for use in Northern Europe will

continue to fall during the coming decade.


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SOLAR THERMAL – FUTURE R&D

The future R&D needs can be divided into two groups

- FUTURE R&D NEEDS FOR MARKET PULL

- FUTURE R&D NEEDS FOR TECHNOLOGY

PUSH


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AREA MEASURESHOUSEHOLD DOMESTIC AND SWIMMING POOL SYSTEM

promotion of technology

EU-wide implementation of standards

Training and certification of installers and system designers

Implementation of third party financing

EU-wide promotion of self-built groups

FUTURE R&D NEEDS FOR MARKET PULL


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AREA MEASURESLARGE SCALE SYSTEMS

promotion in the tourist and multiple-family house sector, together with promotion of use in combination with biomass district heating scheme

Demonstration

(including installations implementing the Guarantee of Solar Results scheme)



35


AREA MEASURES

SPACE HEATING/ COOLING

INDUSTRIAL USES

Demonstration

Demonstration


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FUTURE R&D NEEDS FOR TECHNOLOGY PUSH

Following R & D needs for technology push are necessary in all areas.

TECHNICAL AND ECONOMIC OPTIMISATION OF SYSTEMS

COST REDUCTION (ESPECIALLY FOR SPACE HEATING SYSTEMS)

DEVELOPMENT OF DESIGN ASSISTANCE SERVICES

BESIDE THE ABOVE-MENTIONED GENERAL R&D NEEDS, IT IS NECESSARY TO DEVELOP NEW TECHNOLOGIES FOR COOLING SYSTEMS.


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STANDARDS AND CERTIFICAFOR SOLAR THERMAL

Ensuring a high quality solar thermal products is important for the industry. Standard test methods exist to check

durability, safety and performance. These procedures are specified in European Standards (EN). The Solar

Keymark certifies that a solar thermal collector or a factory-made system complies with the relevant European

Standard.


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SOLAR KEYMARK (Development and dissemination of

standards and certification)Network co-operation about implementing the EN Standards and Establishing the CEN/CENELEC Keymark for Solar Thermal Products (European Solar Industry Federation (ESIF) Proposal no: AL/2000/144.

European Standards were published in 2000 for solar thermal collectors (EN 12975) and factory-manufactured systems (EN 12976). A draft standard exists for custom built systems (ENV 12977). These standards specify how a product should be tested to assess its durability, safety and performance. Results from an accredited test laboratory are often required by financial incentive schemes to ensure good quality products. And increasingly a Solar Keymark certificate is requested to attest to the compliance of a solar thermal product with the relevant EN standard.

Further information on the solar thermal EN standards is available on the Solar Keymark website, http/www.solarkeymark.org le, market, barriers and european standard


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“QUALITY ASSURANCE” IN SOLAR THERMAL

The “Quality assurance” corresponds

SOLAR COLLECTORSSOLAR COLLECTORS

Factory Made Factory Made SOLAR SYSTEMSSOLAR SYSTEMS

Custom BuiltCustom BuiltSOLAR SYSTEMSSOLAR SYSTEMS

Standard EN 12975

Standard EN 12976

Standard ENV 12977


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TEST SEQUENCE FOR SOLAR COLLECTORS

Standard EN 12975:

• Internal pressure• High-temperature resistance• Exposure test (dry stagnation)• External and Internal thermal shock• Rain penetration• Internal pressure (retest)• Mechanical load• Thermal performance (efficiency test in steady-state and

transient condition, time constant, thermal capacity, Incident Angle Modifier, pressure drop)

• Impact resistance (optional)


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EN 12975: QUALIFICATION TEST

High-temperature resistance - Exposure test (stagnazione a secco) - External and Internal thermal shocks

• High level of solar irradiance (> 1000 W/m²) without water;

• Exposure of collector to the ambient conditions without water until at least 30 days with minimum level of solar energy (14 MJ/m²);

• Resistance to external and internal thermal shock.

The aim of these tests is to check the resistance of the collector to :


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EN 12975: QUALIFICATION TEST – RAIN PENETRATION

The objective of this test is to assess the extent to which glazed collectors are resistant to rain penetration.Apparatus: Closed box with artificial rain generation

Test procedure:• Exposure of the collector to controlled rain

(T<30°C) for a period of 4 hour, with the simultaneous heating of the collector through hot water re-circulation (T>50°C).

Results:• No vapour condensation • Collector weight difference before and after

the test < 5 g/m²


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EN 12975: QUALIFICATION TEST – MECHANICAL LOAD

The objective of this test is to assess the extent to which the transparent cover and the mountings of the collector are able to resist at positive and negative pressure loads due to the effect of snow and wind.

Apparatus: a system with uniformly distributed set of suction cups, each connected to air compressed pistons.

Test procedure:• Positive pressure over the

collector cover • Negative pressure

generated by the means of a uplifting strength

Range of applied pressure:• 100 – 1000 Pa with a step of

100 Pa


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EN 12975: QUALIFICATION TEST – MECHANICAL LOAD

………………….Collector

cover fixtures

Stiff frame

Stiff frame

Mountingfixtures

Air piston

SV

SP

Suction CupSteloSSt

P1 P2 P3 Pn

F = Fi

N

F = Fi

N


45

EN 12975: QUALIFICATION TEST: IMPACT RESISTANCE

Scope: to simulate the effect of hails on collector glazingScheme used: system at verticle impact

Articolazione del test:• A series of 10 contacts

realised using a steel sphere weighing 150 gm falling from a distance in the range 20 cm to 2 m with inter spacing of 20 cm.


TEST FORESEEN AS PER NORMS FOR THE SYSTEMS

Standard EN 12976:• outdoor characterization based on daily performance and energy

performance prediction on yearly basis.

Serbatoioacquacalda

Serbatoioacquafredda

Serbatoiodi

accumuloTi

Tf

P

Collettore

Scarico del

draw -off

Scarico per il precondizionamento

Sistema sotto test

Valvola dimiscelazione

Sistema diacquisizioneSistema di

acquisizione

• Solarimetro;• Sens . Tamb

• Anemometro


• Anemometro

Pompa dimiscelazione

Serbatoioacquacalda

Serbatoioacquafredda

Serbatoiodi

accumuloTiTi

TfTf

PP

Collettore

Scarico del

draw -off

Scarico per il precondizionamento

Sistema sotto test

Valvola dimiscelazione

Sistema diacquisizione

Data acquisition system


• Anemometro


• Anemometro

Pompa dimiscelazione

Sensori ambientali


47

SYSTEM TEST FACILITIES

The plant allows the simultaneous performance characterization of two SDHW systems arranged in parallel. The equipment consists of a control system that adjusts water temperatures and flow rates at the inlet of solar systems.

The adjustments are accomplished through digital PID, provided by self-tuning and controlled through a PLC.

A fully automatic data acquisition system controls the different sections of the plant and collects thermo-hydraulic and meteorological data.


48

ARTICULATION OF TEST

1 – Determination of daily thermal performanceThe test comprises of at least six days testing, each sub-divided into following three phases: Pre-condition of system Exposition of Solar radiation Evening Draw-off

icioutip

iiV TTVcQQ ,3

Vi

ii QV

QVf

3

1)(

2 – Determination of losses during the nightTest foresee: Pre-conditioning of system (Ti > 60°C) Night exposure Final temperature evaluation attained by the system

anf

anispS TT

TT

t

VcU ln

3 – Draw-off file with initial mixing Test foresee: Pre-conditioning of system (T initial > 60°C) System draw-off with release of water at a temperature of 30°C less than that of pre-conditioning.


49

PERFORMANCE BASED ON LONGER DURATION

(DAY BY DAY METHOD)The method makes it possible, through an iterative process extended over 365 days/year, to know the energy stored by the system, anually.

A l g o r i t m o u t i l i z z a t o : P a s s o 1 : I n i z i a l i z z a z i o n e ( g i o r n o # 1 ) 1 . )( 1,1,101 caTH TTHQ

2 . 1

0

11, )(V

s dVVfQQ

3 . C

QQTT s

ce1,1

1,1,

4 .

C

tUTTCQ S

aneL exp11,1,1,

5 . C

QQQTT Ls

cs

1,1

1,2,

P a s s o 2 : C i c l o i t e r a t i v o P e r i = 2 : 3 6 5 s t e p 1 , i n i z i o c i c l o :

1 . )()( ,,01,, iciaTiHicisi TTHTTCQ

2 . iV

iis dVVfQQ0

, )(

3 . C

QQTT isi

icie,

,,

4 .

C

tUTTCQ S

ianieiL exp1,,,

5 . C

QQQTT iLisi

icis,,

,1,

F i n e c i c l o .

A l g o r i t m o u t i l i z z a t o : P a s s o 1 : I n i z i a l i z z a z i o n e ( g i o r n o # 1 ) 1 . )( 1,1,101 caTH TTHQ

2 . 1

0

11, )(V

s dVVfQQ

3 . C

QQTT s

ce1,1

1,1,

4 .

C

tUTTCQ S

aneL exp11,1,1,

5 . C

QQQTT Ls

cs

1,1

1,2,

P a s s o 2 : C i c l o i t e r a t i v o P e r i = 2 : 3 6 5 s t e p 1 , i n i z i o c i c l o :

1 . )()( ,,01,, iciaTiHicisi TTHTTCQ

2 . iV

iis dVVfQQ0

, )(

3 . C

QQTT isi

icie,

,,

4 .

C

tUTTCQ S

ianieiL exp1,,,

5 . C

QQQTT iLisi

icis,,

,1,

F i n e c i c l o .

daily energy stored by the system + eventual residual energy stored during previous day;

Energy contained in volume of water effectively used by the consumer;

temperature reached by the system at the end of draw-off ;

Amount of energy lost during night; temperature recorded for the system on

the successive day.

I dati cosi ottenuti consentono di stimare:

365

1 0

365

1, )(

i

V

ii

ieannua

i

dVVfQQQ

annuac

annua

HA

Q


50

EN 12976: THERMAL PERFORMANCE OF SOLAR SYSTEMS

CHARACTERISATION OF DAILY PERFORMANCE: CONSISTS OF THE EVALUATION OF ENERGY STORED BY THE SYSTEM UNDER DIFFERENT CLIMATIC CONDITIONS AND VARIOUS TEMPERATURE FOR SYSTEM LOADING.

THE ENERGY Q STORED BY SYSTEM IS CORRELATED TO THE ENERGY H INCIDENT ON THE COLLECTOR SURFACE AND DIFFERENCE BETWEEN TAMB AND TC, AS PER THE FOLLOWING RELATION:

)(0 caTH TTHQ

0 5 10 15 20 25 30-20

-10

0

10

20

30

40

50

60

70

Radiazione giornaliera (MJ/m²)

Qua

ntità

di e

nerg

ia s

pilla

ta (

MJ)

Ta-Tc= -20Ta-Tc= -10Ta-Tc= 0 Ta-Tc= 10


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SOLAR ENERGY LABORATORYSolar Collector and Overall System Test Laboratory at ENEA Research Centre Trisaia

The Laboratory performs:• efficiency tests both on

glazed and unglazed solar collectors according to European (EN 12975) and international (ISO 9806-1 and 3) standards;

• qualification tests (Internal pressure, Internal and External thermal shock, etc.) according the same standards.Furthermore the Laboratory is able to asses the daily and annual

performance of solar domestic hot water systems according to EN 12976 and ISO 9459/2 standards.

External area of Laboratory

Collector test facilities

System test facilities


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CONCLUSIONS The European Union and its Member States have committed

themselves to achieving a 20% share of renewable energies in Europe's final energy consumption by 2020.

Since heat accounts for 49% of final energy demand in the EU, targets will not be reached without a significant contribution from the renewable heating sector. Solar thermal systems will be needed to provide a substantial share of the low temperature heat.

In order to provide the European Union and its Member States with substantiated information on the solar thermal contribution to the 20% renewable energy target and its long-term potential, detailed study needs to be conducted to examine both the technical and economic potential of solar thermal technologies, for different applications, including industrial heat requirements and cooling.


53

Acknowledgements

Author of this paper would like to express his sincere thanks to Ing. G. Braccio, Ing. Domenico Marano and Dott. Vincenzo Sabatelli for their valuable cooperation.


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THANKS

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