Solar Thermal Tech Mag November 2015

8/20/2019 Solar Thermal Tech Mag November 2015

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Solar thermal inventions to drop by 40% this year, again!

Enough Inventions?

As we are already into the Q4, it is unlikely that the title will be wrong by significant margin.

Last year we saw the drop of almost 33% and this will continue to drop this year as well!

Interestingly this trend looks like the bell curve.

"The Bell Curve represents what statisticians call a “normal distribution.” A normaldistribution is a sample with an arithmetic average and an equal distribution above and

below average like the curve below."

2007 to 2015 are remarkable years in Solar thermal Industry. China was the leader in this

period and contributed more solar thermal patents than rest of the world. Second spot was

held by Germany with its public companies given solar thermal a respectable space to

develop. This data is not dissecting a particular application of solar heat, so you might have

thought that why isn't the Spain (A CSP nation) placed in top two? Not far below! Spain and

Japan tied in the third slot.

More we look at the dropping curve, the harder it is to justify the trend, when under

construction/announced capacity of solar thermal power is a wee ahead of installed/

operating capacity. The top countries mentioned above were placed in reverse order in last

two years of trend. No company/organization from China appeared in the top 10 list of

applicants in these two years. Also, most of the leading organizations halved their invention

protecting activity from previous year. But the question remains :

Where's it going? And why?

At Desk

Find more on disruptiveenergy.net [email protected]

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Target market for 2014 and 2015

Leave that unimproved curve behind and lets get some insight on popular destination for securing commercial interest in

solar thermal industry. Interest for rights in more than 150 countries is grown by 4% and stands at 29%. United states

remains the most weighed market for commercial solar thermal power plants, it was there at the top of bell curve and still

is growing there. Pie chart gives nice insight into where inventors wants to pitch their ideas. The countries mentioned in

the 'Other' had trouble keeping up their value in the eye of an applicant in 2015, as in 2014 Brazil, Chile, Canada and

Morocco were there, not yet in 2015. Though, 'Others' case is not significant in this comparison and that can be ignored,

because, all of important ideas has been protected in their territory, when we saw world-wide tag.

"Being top market for solar thermal energy, US doesn't have a single native company/organization in top league of entities

securing their commercial interest in their own playground."

In the upcoming few years that world-wide tag will translate into the more solar power plants and solar heat based

applicants in countries like India, Brazil, African countries, Middle-East countries and of course in the target markets like

US, EU, China, Australia. Those years also, will decide whether we need to improve Solar thermal technology ans what

pace ?

Dalavi J. K.CESolar Thermal Techmaghttps://in.linkedin.com/in/jagdishdalavi

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KOREAN MODULE

WITH PANELS

MPORTANT:

isruptive Energy and Solar Thermal tech-mag are sole properties of Jagdish Dalavi. Disruptive Energy does not own,invented or partnered for technologies

described here. None of the articles and illustrations are copied as in its original publication from owner of such a technology, a free to retrieve information

nder their certain terms and conditions is included in this digital publication. Disruptive Energy makes every effort to ensure, but cannot and does not

uarantee, and makes no warranties as to, the accuracy, accessibility, integrity and timeliness of this information. Disruptive Energy assumes no liability or

esponsibility for any errors or omissions in the content of this publication and further disclaims any liability of any nature for any loss howsoever caused in

onnection with using this publication. Disruptive Energy may make changes to these materials at any time without notice. Disruptive Energy acknowledges

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SOLAR AIR

HEATING/COOLING

HELIOSTAT MIRROR

PLASMA TREATMENT

MAKE IT LIGHT!


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“ “ The system is able to switch automatically between modes basedThe system is able to switch automatically between modes based

on the sensed conditions in order to achieve the heating or coolingon the sensed conditions in order to achieve the heating or cooling effect desired. The manner in which this can be achieved using effect desired. The manner in which this can be achieved using

temperature sensors, a controller programmable by a user to settemperature sensors, a controller programmable by a user to set

one or more desired building interior temperatures, and fan andone or more desired building interior temperatures, and fan and

damper controllers.” damper controllers.”

SOLAR AIR HEATING/COOLING


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The limited sun-facingsurfaces in condensed livingareas leads to a need forincreased efficiency and spatialeconomy of systems that usesolar energy, for example those

used for heated, cooled ventilation, water, photovoltaic(PV) or wind energy generation.Grace from New Zealand hascome up with this interestingthought. Solar air heating andcooling systems have been usedfor ventilating buildings butalso in commercial settings, forexample, for drying produce.The one system from Canada

draws air through an unglazedsun-facing perforatedaluminium wall intocommercial, industrial orapartment buildings. This typeof solar air heater comes underthe category of transpired solarair collector, with wideapplications such as dryingcrops, manufacturing andassembly plants where there are

high ventilation requirements,stratified ceiling heat, and oftennegative pressure in buildings. A hybrid version has includedthe use of photovoltaic capacityin front of solar air heaters

which was found to enhance theperformance of PVs by reducingover-heating.

Some systems are used inmore residential settings likethe glazed insulated flat platesingle-pass panels and come in various rectangular sizes thatcan be interlocked to form alarger area and a longerchannel of air. These systemscan bring in either fresh air

and/or recirculate warm staleair.

Other examples of solarheating/cooling systems includedo-it-yourself systems that use,for example, drink cansarranged end to end lined up inrows or snaking pipes withinglazed insulated framesmounted on walls, roofs and insome cases windows.

Another excellent design is theuninsulated glazed type like

SolarVenti that supplies air to a

panel through many hundreds ofsmall holes on the backside of

the panel with internal PVcapacity to run a fan.

Some people from Europepreferred an idea of a solar airheater combined with a heatrecovery system having counterflow air along channel

separations runningperpendicular to the front wall.The system uses fresh air,reclaimed air from the buildingor the stored heat from airpassing under the building.Inefficiencies in this systemoccur where air flow isrestricted and where air is indirect contact with parts of thesystem that are difficult to

www.disurptiveenergy.net SOLAR THERMAL Tech-Mag l PAGE I 15e construction of the SolarVenti panels with the front made of a polycarbonate platenctions as an insulation itself. The high quality of both construction and material givese panel its unique characteristics - to be extremely efficient and ultra-light at the same

me.


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clean.Financial benefits result

when solar energy uses can becombined, especially when onecan enhance the performance ofthe other. For example, heat

storage in the form of Phase-Change Materials (PCMs) canresult in a more evendistribution of heated or cooledair in a solar air ventilationsystem. This helps to supplysolar heated air later in the day when more is typically needed.It can also help to prevent anyPV panels present in the systemfrom over-heating. Bearing allthis in mind, it is desirable for

any solar air ventilation systemthat channels air to be adaptivefor use in combination withother solar energy uses.

For example, anexperimental study conductedon double pass solar air heater with thermal energy storage inthe form of PCMs and publishedin the Journal of King SaudUniversity and Engineering

Sciences found that PCMs gavea clear boost of heat energy inthe time after 4 pm for threehours.

We know a flat plate,unidirectional solar air heaterdesigned to store PCMs.However this system does notprovide flexibility enabling it tobe used in a number of modessuch as for heating in the winter

and cooling in the summer.

Canadian Way One Canadian designdescribes the use of ahoneycomb structure as aneffective means to trap heatbetween a solar collector plateand a transparent wall toimprove thermal efficiency.Tests were carried out as to the

effectiveness of bonding thehoneycomb-like structure to the

underneath of the transparent wall in order to direct radiationto the absorbing element and toprevent air flow being directedtowards the front transparent wall. In this design, the air flow

passes through an absorbentcollector element having aporous opaque material with, inmost cases, air being in contact with the honey-comb structure.The internal components of thecollector are liable to beingsoiled from air flow, whichaffects transparency andtherefore efficiency, and thedesign makes the collectordifficult to clean.

Solar energy is harnessed ona grand scale in the form ofsolar chimney power plants.Large greenhouse roofedcollectors, located at the base ofa chimney, generate electricityby means of an updraft orconvection (chimney effect).This airflow drives windturbines inside or at the base of

the chimney. For example, atower in Jinshawan inMongolia, with collection areaintended to cover over 200hectares, absorbs heat from thehot sand under glass covers.Using the greenhouse effect, hotair flows up the chimney andgenerates power by turning theturbine inside the chimney.Some even tried air flow via a

trombe wall to a turbine usingsolar chimney effect as a meansof heating, cooling and ventilating.

The similarity in all types ofsolar air heaters is that theycapture solar insolation via anabsorbing medium and thenheat air. They have wide usepotential for drying crops, glass

houses, desalination plants,commercial, industrial,

residential settings, etc. Thechallenge is to increaseefficiency, both for the shortterm and long term duration.Solar air heaters may measure well in efficiency in the short

term, but clog up fromcontinuous air flow renderingthem inefficient in the not solong term. For example, thearea above the absorber may be warmer than the area below theabsorber.

Therefore, air passingbetween the transparent front wall and the absorber plate would maximize the uptake ofheat in the short term, but mayquickly diminish thetransmission of heat and thusefficiency through soiling of theunderside of the glazing.

Collector efficiency ofsolar air heaters depends alsoon the rate of fan flow. A

reduction of air flow leads tomaximizing air temperature riseat the outlet but this is at theexpense of solar air heatingsystem efficiency. The desirableair flow depends on such factorsas the outside air temperaturedifferential, efficiency of solarair heaters to extract heat fromthe absorber, impeded air flow within the solar air heater, other

means to preheat/precool theair on entry such as by heatrecovery, etc. Most solar airheaters fall within the range of40 to 70% efficiency.

Experiments have beencarried out on the efficiency ofsingle versus double passarrangements using the sameair source. It was found thatefficiency increases with air

mass flow rate. Efficiency alsoincreases when it is a double

SOLAR THERMAL Tech-Mag l PAGE I 6


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pass system. The maximumefficiency difference betweenthe single and double pass airheater was 59.62% and63.74%, respectively for airmass flow rate of 0.038 kg/s.

These factors can be considered when designing improved solarair heating technology.

One solar air heating system which endeavors to maximizeefficiency by using cut segmentsof a pipe bent inwards to form afin to create turbulence in thechannel inside the pipe.However, this system results inthe flow inside the pipe beinginterrupted and pressurized as a

result. The interruption to theflow restricts the volume of airpassing through the pipe andtherefore the amount of air thatcan be heated. These fins mayalso be very difficult to clean.

Economic efficiency can beachieved by a roof-integratedsolar air heating system. Aneconomic analysis found that aroof-integrated system to be

efficient and economically viable and this was backed byan experiment to drypineapples. It is thereforedesirable for a solar air heatingsystem to be designed in amanner that enables it to beable to be roof-integrated orintegrated into any part of abuilding.

Another study was carriedout on a hybrid thermal energystorage system using phasechange materials for managingsimultaneously the storage ofheat from solar and electric

energy. The results were a 32%reduction in electricalconsumption for space heating.This is significant when oneconsiders that the stored heat was released during peakperiods when 90% of electricityis consumed.

New setup of solar airheating and cooling

system

The collector has upperair channels and lower airchannels separated from oneanother (See FIG1). The upperand lower air channels are keptparallel to each other. Upper airchannels receive solar energy, which heats the air therein.Lower air channels are shielded

from solar radiation by theupper air channels. Thecollector is made in such waythat lower air channels are inthermal communication withthe upper air channels, i.e. heatcan transfer between the airpassing through the twochannels.

The upper and lower endsof both the channels connect toopenings through which air mayflow to enter or exit thechannels.

Connected to the upperopening of upper air channels isan air exhaust duct and aninterior air duct B. Exhaust ductand interior air duct B are bothconnected to an intermediateduct via a duct junction,although this intermediate ductis optional. Exhaust duct opensto the atmosphere, for examplethrough cowl that can be usedto decrease the back-flow down

the exhaust duct. The other endof interior duct B is connectedto the building interior via anopening Y. A fan F2, ispositioned to drive air along theduct in the direction of thebuilding interior. Flow controlaction is done by dampers D1and D2, they can selectivelyblock the air exhaust duct andinterior air duct respectively.

Connected to the loweropening of upper air channels isan air entry duct and anotherinterior air duct C. Air entryduct and interior air duct C maybe both connected to a commonduct via a duct junction. Entryduct is connected to the outsideair, for example in the soffit ofthe building. Interior duct C isconnected to the building

interior via opening Z. OpeningsZ and Y may be located indifferent rooms of the building.Flow control is done bydampers D4 and D3, are able toselectively block the flow of airalong the interior air duct C andthe entry duct, respectively.

The upper end of the lowerair channel is connected to thebuilding interior via opening X

and interior air duct A. A fan F1is able to drive air along duct A



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in the direction of the collector.The lower end of the lower airchannel is connected to a panelair exhaust duct, which isconnected to the outside air.The panel exhaust duct has an

opening in the underside of thecollector. An air duct E can connect

interior air duct B and interiorair duct C.

We will discuss the

operation of this solar airheating and cooling system.Several modes of operation willbe described.

Winter solar heatingmode

FIG. 2 is an illustration ofthis mode. In this mode, fan F2is on while fan F1 is off.Dampers D2 and D3 are open

(i.e. they allow air to pass) while dampers D1 and D4 areclosed. Fan F2 draws outside airthrough entry duct and throughthe upper channels of thecollector. Solar radiationincident on the collector causesthe air to be heated whilepassing through the collector.The fan then drives air into thebuilding interior through ducts

B and E and their respective

openings.

In this mode, the systemacts as a positive pressureheating/ventilation (PPV)system, driving solar heated air

into the building interior. Thishas advantages of many existingPPV systems in which warm,stale air in the roof space isdriven into the building interiorbecause these suffer from therisk of smoke from fires in theroof space being driven into theinterior. In this present system,only fresh, exterior air is drivento the interior.

Winter reclaimed heatmode FIG. 3 is an illustration ofthis mode. In this mode, bothfans F2 and F1 are on. DampersD2 and D3 are open whiledampers D1 and D4 are closed.

Fan F2 draws fresh air from theexterior through the collector where it is heated by the sunand driven inside, in the same

manner as the ‘winter solarheating’ mode. Additionally,preheated airfrom the buildinginterior is drawninto interior duct A by fan F1. Thisair is driventhrough thelower channel of

the collector

where its heat is transferred tothe fresh air passing throughthe upper channels of thecollector.

In this mode, system acts asa balanced pressure ventilation

system. The heat in thepreheated air passing throughthe collector adds to the heatingof the fresh air in the upperchannels of the collector, thusreducing heat energy lossesfrom the building interior.Operating in this mode, thesystem is able to conserve heatin the building while stillproviding fresh air ventilationeven if the sun is not shining.

Summer solar coolingmode FIG. 4 is an illustration ofthis mode. In this mode, bothfans F2 and F1 are off. DampersD1 and D4 are open, while

dampers D2 andD3 are closed.The sun heats the

air in the upperchannel. Thiscauses the air to warm and rise,drawing airupwards throughthe system. Air inthe building

interior is drawn up through theducts B and C, through theupper channel and to theoutside air through exhaustduct and cowl. This mode takes



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advantage of passive solarheating in the manner of a solarchimney to draw warm air outof the building interior, creatinga negative pressure. This causesfresh, cool air to be drawn into

the building (for examplethrough windows and doors),causing the building to becooled and ventilated.

The system does notdepend, on trickle venting from within the building. Modernbuildings are increasingly wellinsulated and do not allowoutside air to penetrate when itis closed up. When this is thecase, damper D3 can open,

allowing the solar air heater tocool down with outside freshair. Air would either escape outof the system, for example, via acowl, a vent built into a duct atthe top of a roof window orunder some type of roof ridgecover. The option to draw airfrom another source may notonly be helpful to cool down thesolar collector when it is starved

of air from within the dwellingbut also allows other ways ofcooling in the building tocontinue (like heat pump).

Summer heater coolingmode FIG. 5 is an illustration ofthis mode. In this mode, both

fans F2 and F1 are off. DampersD1 and D3 are open, whiledampers D2 and D4 are closed.The sun heats the air in theupper channels. This causes theair to warm and rise, drawing

air upwards through the system.Fresh outside air is drawn upthrough entry duct, through theupper channel and to theoutside air through exhaustduct and cowl. This mode againtakes advantage of passive solarheating in the manner of a solarchimney, but this time drawscool fresh air through thecollector. This mode may beuseful to cool the solar air

heater, particularly if the houseis unoccupied and the system isnot operating in full. Cooling ofthe solar air heater may bedesired if other components, forexample photovoltaic cells, areused in conjunction with thesolar air heating system andthose components need to beprevented from overheating.

Summer non-solarcooling mode FIG.6 is an illustration of thismode. In this mode, both fansF2 and F1 are on. Dampers D2and D3 are open, whiledampers D1 and D4 are closed.Fan F2 draws fresh air in fromthe outside through entry duct

and the upper channels incollector, and into the buildinginterior through ducts B and E.Meanwhile, fan F1 draws pre-cooled stale air in the buildinginterior into duct A and through

the lower channels of thecollector. The heat of theoutside air is transferred incollector (which also acts as aheat exchanger) to the pre-cooled air in the lowerchannels, thus cooling theoutside air that is pushed intothe building interior. The effectof the system in this mode is tocool the building interior bycooling incoming fresh air using

the heat difference with theexiting pre-cooled air.

The system is able toswitch automatically betweenmodes based on the sensedconditions in order to achievethe heating or cooling effectdesired. The manner in whichthis can be achieved usingtemperature sensors, a

controller programmable by auser to set one or more desiredbuilding interior temperatures,and fan and damper controllers.

So what is the new this

article has got in this system?

Yes! It is to at leastprovide the public with auseful choice.



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“The heliostat is a simple plane support structure, coated with a

highly-reflective optical material and mounted on a tracking

pedestal. The required qualities of a state-of-the-art heliostat are

lightweight, low-cost, structurally rigid, environmentally durable,

with a highly reflective surface. In improved designs, a very slightcurvature in the heliostat mirror is introduced to enhance the

focusing quality.”

HELIOSTAT

MIRROR

David66 (Own work) [GFDL (http://www.gnu.org/copyl!t/!dl.ht"l) or ## B$%&' . (http://crativco""on*.org/licn**/+y%*a/.),- via iki"dia #o""on*


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Heliostats are the ones which directs a solar radiationonto the receiver in CSP plant.They are plenty in number andmust be designed for high-yield.

Heliostats focus reflectedsolar radiation onto a receiverof high-specific heat material. Aheliostat is basically a flat plate with a highly reflective surfaceto efficiently reflect most of thesolar radiation incident upon itonto the receiver. The heliostatmust be capable of tracking thesun across the sky and pointingthe reflective surface in theappropriate direction to

maintain the sun's reflectedradiation on the receiver. Theheliostat is a simple planesupport structure, coated with ahighly-reflective optical materialand mounted on a trackingpedestal. The required qualitiesof a state-of-the-art heliostat arelightweight, low-cost,structurally rigid,environmentally durable, with a

highly reflective surface. Inimproved designs, a very slightcurvature in the heliostat mirroris introduced to enhance thefocusing quality.

Heliostat from L'GardeOn this October L'Garde

made its new heliostat ideapublic worldwide. We arelooking at their effort in this

new heliostat and what itoffers?

First take a look at itsbasic core elements in FIG.1.The typical design for aheliostat include a lightweightbase with top and bottomsurfaces attached to metalsheets. A rigid foam is used asthe lightweight base. The metalsheet is highly polished to

provide the reflective surface orattached to a mirror film. The

mirror film include layers ofmaterial, a backing layer and anouter metallic or reflective layer. A moisture barrier is appliedand enclose the heliostat to sealthe terminal ends and space

between the respective layers.

The base is used toprovide the support structurefor the heliostat and its shape.The lightweight base has a rigidfoam. Rigid foams can haveexpanded polystyrene (EPS),polyurethane foam, epoxy foam,and carbon-reinforced foam.

Adhesives are used to

bond the metal sheets to thefoam support structure, theadhesive is impervious to the weather and performs over alarge temperature range. Adhesives have choice such asepoxy silicone, urethane,polystyrene and polyester basedadhesives in required formats.

Thin metal sheets cover

surfaces of the base. The thinmetal sheets are made fromstainless steel, aluminum, ortitanium. The thin metal sheetitself provide polished surfaceor we can include a film tocreate the mirror surface. Thethin reflective film may beeliminated if the top metalsheet used is a mirror-finishsurface like mirror.

A reflective mirror filmis made of a thin polymericmaterial coated on the outer

surface with a thin layer ofreflective material, such as a

metal.

The reflective mirror film

backing is typically made of

materials like thin polyimide,

polyester (PET), polypropylene(OPP), polyethylene (PE),

polyvinyl (PVC), nylon (BON),

and polycarbonate (PC) film. In

order to make the thin film

reflective, a thin layer of silver or

aluminum coating is deposited

on one surface.

For added protection

against the environment, amoisture barrier rubber paint isapplied all around the edges.This moisture barrier cover theterminal ends to preventseparation of the layers. Choiceof materials for moisture barrierinclude polyurethanes. acrylics,ethylene acrylic, nitrile, styrenebutadiene, silicones, neoprenes,and epoxy.

RMS Slope errorThey are using here very

low-cost, lightweight materials while still maintaining anextremely accurate surfacequality. There analytical modelsindicated that RMS slope errorson the order of 0.15 milli-radian were achievable with thisdesign. Two 1m by 1m in area

and 4 inch thick prototypeconcentrators have been builtand measured for surfacequality. This prototype heliostat

sub-mirror facet was measuredusing precise photogrammetry



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for RMS slope error.

Rapid ProductionThis production method

include the use of inch by inchattachment, such as by bonding,

of the mirror film to thestainless steel sheet usingTeflon-coated rollers to applypressure on the mirror film forstronger initial adhesion, and vacuum-bagging to assureexcellent adhesion andprevention and elimination ofbubbling. The fabrication isautomated using a roll-to-rollmethod in that thethin metal sheets are

dispensed from a rollerand applied ontoeither surface of thebase using a thirdroller. Adhesiveapplication is alsoautomated by the useof jet nozzles. As thebase with the thinmetal sheets alreadybonded moves on a

conveyor belt to thenext section of theassembly line, themirror film is appliedto one of the metalsheets. This step is notnecessary if one of thetwo metal sheets usedis already a reflectivemirror.

This heliostat designinclude some innovativesupport structures for thereflective panel that can reducesystem cost and weight overother available in the markettoday.

Heliostat DesignFigures 2A(top

perspective) and 2B(side cross-

sectional) illustrates supportstructure with three distinct

parts joined to form a unit.These illustrations are for ideaonly, you can understand that. Asupport structure with threedistinct parts include, two wingsections and a central section.

Two symmetric identical wingsand a centerpiece are providedon which the wings aremounted. The centerpiece ismounted on suitable structure,known as a pedestal. The wingsand centerpiece are coupled toeach other. External frame canbe used to wedge parts together,or just hinged.

The wings can beslightly curved in someheliostats. Curvature providesmore accurate focusing of therays onto the receiver.

You are free to mountreflective surface over the wingsalone or over the wings as wellas over the centerpiece. In sucha situation the reflective

surfaces are mounted over the

wings alone. The centerpiecesection of the support structureis therefore exposed along thetop surface. This configurationallows the formation of twoseparate surfaces.

A slight curvature of thesupported surface in the wing- wing direction is done by thecenterpiece's shape. Thegeometry centerpiece orientsthe wings in a slight convergentmanner. As illustrated in theside elevation views, the profileof the centerpiece support

structure is tapered suchthat a top length of the

centerpiece is less thanits bottom length. Figureshows a centerpieceincluding a precisionsurface and supportstructure. As seen in Fig.2C, the bottom surfaceof the support structurehas a wing-wing lengthof X, while a top surfaceof the support structure

toward the reflectivesurface has a length Y.Here, X is greater than Y.The exterior edges of thecenterpiece abut thesupport structure of the wings are configured toorient the wings at adesired angle relative tothe centerpiece section.The support structures

of the wings are generallyrectangular in wing-wing cross-section. The surface structurehas the reflective precisionsurface. The surface structurehas a wing-wing length of Z.The surface structure length Z isequal to or less than the topsurface length Y of the supportstructure adjacent the surfacestructure. The length Z is less

than Y for tapered profiles toprevent the surface structures



15/30

from interfering in the angledsetup.

By controlling wing- wing curvature by thecenterpiece shape alone, the

fabrication of a high number ofstructural units with different wing-wing curvatures is madeeconomical. Specifically, the wing sections may be uniformlymade and a wing-wingcurvature can be achieved bysimply exchanging differentcenterpieces of greater or lesstapering profiles. The shape ofthe centerpiece is determined

by the distance of the heliostatstructure from the receiver, withless curvature required as thedistance between heliostat andreceiver increases. A lesser wing-wing curvature can beachieved with less taper, or amore rectangular shapedsupport structure.

Let's take example, amiddle section of a tri-sectionalsetup, is interchangeable in thesense that there may be

typically several such

alternative mid-sections pre-fabricated, and on any of thesethe same wings can be mountedon the two sides. Due to theslight differences of thegeometries of the center

elements, the pair of wings endup forming a near concavemirror, this concavity dependson the central element used.The need for mirror concavity isa function of location in theheliostat field; mirrors nearerthe receiver have to be moreconcave than those fartheraway. So, center pieces ofcertain shapes will end up being

used in certain continuousregions within the field, makingthe mirrors there have identicalshapes but somewhat differentshapes from mirrors in otherareas of the heliostat field.

The constructionconcept of different centerpieces used across the fieldhelps in eliminating the needfor geometric tuning by nuts,screws, etc. By using a set ofslightly different prefabricated

center pieces instead, nothing

needs to be adjusted on theconstruction site. Simply, theright type of centerpiece has tobe used. This is faster andsimpler if well managed byaverage Joe.

Figure 3 shows us thesupport structure with amultiple precision surfaces toform a larger heliostat.Precision surfaces include theirown support structure. Eachsurface supported by the thisstructure is constituted by amultiple panels which aremounted on a larger support

structure. To facilitate the

mounting of the panels ontheir support, the largersupport has one primarysupport aligned in the wing- wing direction and secondarysupport in the perpendiculardirection from the wing- wingdirection.

Mainly, we have aprimary support in a wing-

wing direction. A secondsupport is included inperpendicular to the firstdirection. The second supporthave rails such that panels areretained between two adjacentrails.

Rail section isrecognizable from Figure 4 which is configured to retain a

panel in place. The rail crosssections have flanges for thepanels to be slid betweenadjacent pairs of the parallelrails. The rail bottom terminalend has a stopper such that thefirst panel rests against thestopper. The next panel thenrests on the first panel, and thepanels are stacked on top ofeach other and held in place in

the forward and rearwarddirection by the flanges of the



16/30

rails.The rails are mounted

on the primary support by arapid lock mechanism. Thismechanism between rails and

primary support has protrusionplus hole system, so fastenerscan firmly attach the secondaryrails to the primary support.

The rail has two planar, parallelsurfaces coupled by a gussetplate.

The wings of theprimary support are trusses of

triangular cross section. Thelateral struts on one face of thetruss wings are removable topermit nested stowage andshipping. We have here aprismatic wing construction with removable battens anddiagonals. Cable links, if usedare fantastic in this type oftruss, which can be easily andrapidly engaged at their finallocations and robustly held

there by pretensioning.

Heliostat is not thecomponent in CSP plant, that

we want to replace in less than10 years. Hence, there is lot ofthought gone into this versionto make it cost effective andeasy to operate, also quick intransport and install.

www.disurptiveenergy.net SOLAR THERMAL Tech-Mag l PAGE I

OFFER ON THE NEXT PAGE IS ASLO AVAILABLE TOOFFER ON THE NEXT PAGE IS ASLO AVAILABLE TOSOLAR HEAT !se "SH" in p#$%e &' "PV" in %&de.

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18/30

“This solar thermal collector panel is originated in South Korea

and has a module with multiple thermal collector panels. The

USPs conveyed are a vacuum thermal collector panel made of

glass efficiently at a minimum loss and transfers it to a heating

medium, a large-scaled solar thermal collector module having

multiple vacuum thermal collector panels inside it. ”

KOREANKOREAN

MODULE WITH PANELS


19/30

There are thousands ofdesigns available today of solarthermal collector, still peoplefind new ones regularly!

This solar thermalcollector panel is originated in

South Korea and has a module with multiple thermal collectorpanels. The USPs conveyed area vacuum thermal collectorpanel made of glass efficientlyat a minimum loss and transfersit to a heating medium, a large-scaled solar thermal collectormodule having multiple vacuumthermal collector panels insideit.

We Have Them ! A key technology forharnessing solar thermal energyis thermal collection, heatstorage, and system control.Because of solar thermal energyhas a low energy density and a

big variation with seasons andtime of the day, thermalcollection and storage is a basictechnology, and thus, it's thepress point for new designs.

FIG. 1, the old solarcollector panel has a metal case

with a transmission glass

covering the top of the metalcase. The glass window istransparent and allows solarradiation through and into thesolar thermal collector panel.Inside the panel, an insulation

and a thermal collector plateare stacked. The collector plateis where solar thermal energy iscollected. The insulation isprovided between the collectorplate and the metal case toprevent heat transfer.

Also, a absorber plate joined with a heating medium pipethrough which a heating fluidflows is placed between thethermal collector plate and the

insulation.Still, this solar thermal

collector panel has a problem with a loss of thermal energy.

A loss of energy due to (a)reflection on the surface of thetransmission glass occurs, (b)

convection of an air layer itselfinside at the collector plate. It'shuge! yes, an amount of lostenergy is equivalent to about23% of the total incoming solarthermal energy only due to thepresence of the air layer inside

the collector panel.

Also, because the insulationcannot perform a perfectinsulation function, a loss ofenergy occurs due to leaks ofthermal energy collected by thecollector plate though the

insulation and the metal case byconduction. Above design was a very

simple collector, that can bedared in very hot regions only.

An improved one, thereis a solar thermal collectorproduct with a vacuum inside,but a large amount of heatgenerates from surfaces of topglass flat plates, as a result, theupper glasses of the thermal

collector are prone to stress dueto a temperature difference, and when the glasses are damaged,the overall thermal collectorneeds to be replaced,unfortunately, damage to acertain part results in a loss ofoverall function.

Also, due to a vacuuminside, a thick front surfacetransmission glass is used to

resist an atmospheric pressureload against the internal vacuum, and for this reason,there are disadvantages of aheavy weight, high materialcosts, and an increase inabsorption loss of the frontsurface transmission glassitself.

Korean CraftFIG. 2, shows a structure of

a plurality of plate-type vacuum thermal collectorpanels mounted and arranged.,

The vacuum thermalcollector module includes a caseof a metal having a generallyopen top and an insulationprovided at an inner surface ofthe case to prevent heat

transfer.

www.disurptiveenergy.net SOLAR THERMAL Tech-Mag l PAGE I 17


20/30

Here, multiple vacuumthermal collector panels arearranged adjacent to each otherin a horizontal direction withinthe case. Set in requirednumber of collector panels in ahorizontal direction and we areready to achieve a large scale.

Also, when a portion ofcollector panels belonging to

the module is broken ordamaged, only a correspondingcollector panel needs to bereplaced, and thus, it is easy tomaintain and repair and costsinvolved in maintenance andrepair reduce. Plus, becauseeach collector panel isindependently formed, eventhough a certain collector panelloses its function, a function of

other collector panel ismaintained, so an overallfunction of the collector moduleis performed without a bigproblem. Great !! Now concentrate oncollector panel, in FIGS. 2 & 3.

the plate-type collector panelhas a structure of supporting anexternal atmospheric pressureload in a vacuum (10−3 torr)state inside, and the plate-typecollector panel includes a toptransmission glass to allowtransmission of radiation, abottom support plate to providesupport, and a side support

spacer interposed between thetwo to maintain a space, andallows an internal space tomaintain in a vacuum state

≤10−3 torr.

The top glass is a boric acidglass or a low metal glasshaving a high solartransmissivity. A boric acid glassis a result by adding boronoxide (B2O3) to a general glass

composition and has a lowerthermal expansion rate than ageneral glass, so, is used inapplications under severetemperature variation, like, adischarge tube, a combustiontube, a laboratory equipment,

etc. The top cover may becoated with a metal, aninorganic material, and anorganic material on the surfaceto increase light transmissivityand reduce reflectivity. Thebottom and side support platesmay be made of a glass or ametal.

The top, the lower support

plate, and the side supportspace are joined and vacuum-sealed by brazing or glass-metalbonding to maintain a vacuuminside. To maintain a degree of vacuum, a non-diffusion gettermay be coated on the edges ofthe top aperture or may becoated as a thin film at a properlocation.

We have here, is a thermal

absorber plate to absorb heatfrom the sun and a HTF (HeatTransfer Fluid) circulation pipe within the vacuum space. Theabsorber plate is coated with ametal, an inorganic material,and an organic material toincrease light transmissivity andreduce reflectivity. The thermalabsorber plate and the pipe areconnected to each other by

brazing joining or close bondingto transfer heat absorbed by the



21/30

thermal absorber plate to thepipe. Brazing is a process that joins both basic materials to be joined by adding a filler metalat temperature lower than amelting point of the both basic

materials, in process the basicmaterials are joined withoutdamage. The absorber plate and thepipe are mounted in theinternal space in a vacuum, aloss of collected energy causedby convection is prevented. The absorber plate can becoated with a film for increasinga solar thermal absorption rateand preventing reflection on an

upper surface. The reflectionpreventing film is a film thatserves to absorb solar radiantheat, generate heat, andprevent reflection of sunlight.Popular choice would be blackchrome plating and a blacktitanium coating (titaniumdioxide thin film). Thisfacilitates absorption of solarradiant heat and heat transfer

by using a metal having a highdensity and a black color.

Besides, graphite powder maybe additionally coated.

A pipe adapter is formedin the plate-type collecting

panel and has a through-hole

through which the pipe passes.It supports the pipe. The pipeadapter is made from a metal.

FIG. 2 , It's provided with a spacer. The spacer passesthrough an opening formed inthe absorber plate within the

internal space of the collectorpanel, and is mounted inbetween the top glass cover andthe lower plate to act as supportto the top glass and the lowerplate. Spacer is must, when the

vacuum collector panelincreases in scale and resist anexternal atmospheric pressureload effectively when thecollector panel creates a vacuum inside.

Material for the spacer like,glass, metals with ceramic,organic and inorganic materials,are accepted.

Design The Best FIG.4,the multipleround-type vacuumthermalcollectorpanels areused andindependently arrangedadjacent to each other in ahorizontal direction within the

case.

A side support spacer placedbetween the top glass and thelower plate to maintain a space.the top glass and the lower

plate are joined and vacuum-sealed by theside supportspacer.

Obviously,the difference

here is the top glass and thelower plate are rounded at anarbitrary R (radius) to have ashape of a convex center. This isto resist an atmospheric

pressure load caused by aninternal vacuum effectively.

The round-type collectorpanel shown in FIG. 5 has astructure including two roundstructures with a convex center,and multiple round structuresmay be continuously formed. In

this design, an inner spacer isused at a point where a spacebetween the top glass and thelower plate is minimum.

FIG.6 A small and importantmodification of the side supportspacer of the collector panel.

The previous side supportspacers have a shape of a squaremember. Side support spacershere having a curved orcorrugated shape.

That is, the side supportspacers are made of a metal in ashape of a plate having both

ends joined to the top glass andthe lower support plate, andhave a curved shape. Thecurved shape may be a singlecurved shape or a corrugatedshape of multiple curves. This isto allow the curved shape of theside support plate to absorbstress or warpage caused by atemperature difference betweenthe top glass and the lowersupport plate.

Well, only cost ofmanufacturing aside, this hasmany advantages overconventional solar thermalcollectors. Key would be thereal data backing up theseclaims from developer, we mayfind the same in upcoming days.



22/30

“Solar collectors of lightweight construction often have the

disadvantage that their structure has insufficient self-supporting

properties. Here, investments goes into a large number of supports

required, even though the solar collectors can be only quite small

in size.”

MAKE IT LIGHT !

Z22 (Own work) [CC BY-SA 3.0 ("#$$%r&'&%o**on+.or,$%&n+&+$y-+'$3.0)/ ' 1k*&' Co**on+


23/30

They build, and we know itas German Engineering. ThisGerman design of solar collectorand its segments which trailsback to 2009, is still improvingin 2015. Interesting point is, a

company has shown positivesigns for US market with thisimproved one design.

Solar collectors are oftenused in the form of parabolic-trough concentrators in most of

the power plants. If not; still

this thing isn't anything other

than parabolic-trough here!

Weight and CostsLarge-scale power plants

can have a number of seriallyarranged solar collectors withtrough-shaped reflectors which will direct the sunlight onto atubular absorber. For orientingthe solar collectorscorresponding to the solarradiation, common process is torotate the trough-shapedreflectors about their

longitudinal axis. Parabolic-

trough structure is expensive! Every time investor think

of these costs, he couldn't stop

thinking of daylight robbery,

that too in the name of

daylight !

Concentrating structuremust withstand its promise atthe end of its life-cycle and

ought to be standing tall at timeof farewell, as it had seenthrough worst of environmentaldisasters. In order to reduce theapparatus-related expenditure when using this approach, withthe help of a drive unit, thesereflectors are rotatedsimultaneously.

Constructions having alength of up to 120 m are to berotated by drive. The trough-shaped reflectors must have ahigh torsional stiffness so thatthe deviation of the rotationalangle during rotation of thereflectors cannot exceed aminimum tolerance.

For above said reason,collectors were often built fromsteel constructions with mirrorsmounted on them in theconventional way. With the steel

density of order 7000+ kg/m3

results in a massive weight ofthe solar collectors. Again,

complex support structures were required, and the weightresulted in high costs fortransportation. The reflectorshad to be built on site fromindividual components, thus

causing an assembly chaos atthe installation site.Solar collectors of

lightweight construction oftenhave the disadvantage that theirstructure has insufficient self-supporting properties. Here,investments goes into a largenumber of supports required,even though the solar collectorscan be only quite small in size.

A German company has

tried here to provide a segment

of a solar collector which is light-

weighted design, high torsional

stiffness and self-supporting

structure, while also the

assembly work on site kept small.

Main focus is to provide a

solar collector having a light-

weighted design and a self-

supporting structure.

Structure BasicsFIG. 1, represents one

segment of a solar collector.This segment has twolongitudinal sides those playimportant part in the finalassembly. The top side of thesegment is curved, the uppersurface is provided with areflective layer.

On longitudinal sides, anumber of such segments canbe connected to each other toform a row of segments.

The segment has a flange by which this segment can beconnected to an oppositesegment of identical design toform a complete trough curve.

FIG. 2, the segment in



24/30

sectional view. Segment includea core structure enclosed by ashell.

Core structure consists oftwo cores made of foamedmaterial, and of ribs made of a

fiber material. These ribs can beproduced by wood. Best, theribs are made of Australian pinesince this type of wood has aparticularly high stiffness.

The ribs are each provided with a cover made of a fibermaterial. Two of the ribs arearranged on the longitudinalsides of segment so that the ribsenclose the cores of foamed

material. The third rib withcover is arranged between thecores of foamed material.

The rib cover made of fibermaterial increases the stabilityof the ribs. Shell enclosing thecore structure can have multiplelayers of fiber material.

Shell consists of a top shelland a bottom shell, each ofthem made of a layer of fiber

material. The shell covers thecore structure. In this design,the top shell extends around thetop edges, while the bottomshell extends around the bottomedges formed between thelongitudinal sides and thebottom side. Again, we can havemultiple shell layers of a fibermaterial.

These two shell halves

helps in the bonding connectionof the segment to a further

segment via the respectivelongitudinal sides. This willgenerate a stable structure fromthe respective shells of thesegments. In this manner, therecan be formed solar collectors

which have a self-supportingstructure and further have ahigh torsional stiffness andbreakage resistance.

FIG.3 The region aroundthe longitudinal sides of asegment is shown in enlargedsectional view.

As said earlier the top shellhave three layers a,b,c while thebottom shell also have three

layers d,e,f. These all layersconsist of a glass fiber material.These can be applied in theform of glass fiber mats. Thelayers 'c' and 'f' facing toward

core structure consist of a glassfiber with multi-axially orientedfibers, whereas the outer layersa,b,d, and 'e' consist of a glassfiber with unidirectional fibers. Another important part of the

system is reinforcement stripsthat are provided to reinforcethe edges of the core structure. Also said reinforcement stripscan consist of a fiber material.

Fiber everywhere!

When producing thesegment, the ribs will first bebonded to the shell with anepoxy resin adhesive. Theindividual layers of the bottom

shell will also be bonded withan epoxy resin adhesive. Thecore structure will be arrangedon the bottom shell. In case it isintended to use reinforcement



25/30

strips, these can be inserted andalso bonded prior to theplacement of the core structure.Then, the individual layers ofthe top shell will be applied andbonded. By the use of a fiber

material with an epoxy resinadhesive, will beadvantageously soaked by theepoxy resin adhesive, so that a very good connection will beeffected between the individuallayers. The substance-to-substance bond between theindividual layers is of such agood quality that the shellconsisting of the individuallayers can be considered as

forming one integral piece.Uneven spots and any

recesses caused by thereinforcement strips can befilled by the adhesive material.

FIG.4 two mutually bondedsegments are illustrated inpartial sectional view. The twosegments are bonded to eachother via the longitudinal side.

In this manner, the shells ofthe mutually bonded segmentsare combined to a supportstructure shaped as double T.

The high stability of a solarcollector with multiplesegments is achieved, while thesolar collector is given anadvantageous self-supportingstructure as a result of thebonded shell.

Due to the materials usedfor the segments, it is madepossible to assemble theinventive segments into a solar

collector of low weight and highstability.

The segments can bereinforced by further layers offiber material which are locatedin regions of elevatedmechanical stress. For instance,the flange can be reinforced by

added layers.FIG. 5 a solar collector isdepicted in sectional view. InFIG. 6, a solar collector isdepicted in perspective viewand is presented in a stronglypivoted position.

The solar collector is madeof a multiple interconnectedsegments as said before. Withthe help of the flanges of thesegments, two rows of segments

are assembled into a parabolictrough. A solar collector canconsist of 24 segments.

The flanges are enclosed byan U-profile, carefully, the sizeof the flanges can be kept smalland the torsional stiffness of thesolar collector can be improved.Said U-profile can have multiplemutually bonded fiber materiallayers. The two rows of

segments and the U-profile canbe bonded to each other.

At the respective ends ofsolar collector, supports arearranged on which the solarcollector is mounted withrotational degree of freedom viaattachment metal plates. We

can repeat as many collectorsas those are arranged behindeach other in a row andconnected to each other. Thesecollectors can be rotated by acommon drive unit for adjustingthe solar collectors to thealtitude of the sun.

In the focus of the parabolictroughs formed by thesegments, a regular absorber

tube is placed by supportstructure.

On the bottom side of solarcollector, a frameworkconstruction is made forimproving the torsional stiffnessof solar collector. With the aidof fastening means, frameworkconstruction can be attached tothe surface formed by thebottom sides of the segments.

Bolting to the ribs is best way toattach framework structure to



26/30

segment. The frameworkconstruction is furtherconnected to U-profile andattachment metal plate. Theframework construction is alsoconnected to the support

structure of absorber tube. Now, we have obtained a very highstability and torsional stiffnessof the solar collector. Thetorsional stiffness in this designis so high that, in a row of a

multiple solar collectors of alength of 120m, a rotationalmotion will cause a rotarydeviation of the solar collectorsof just 5 milliradians.

The framework construction

is preferably made of a stablematerial, e.g. steel.These innovative segments

allow for the production of verylight-weighted solar collectorshaving a self-supporting

structure and also a very hightorsional stiffness. One canthink of segments bonded toform a row of segments atfactory, so that, at theinstallation site, these segments

merely have to be connected toa further row of segments viathe flanges. The solar collectorsof the invention can have alength of up to 12 m and anaperture of 4.60 m.



27/30

NEM Energy fromNetherlands made its method

for treating an outer surface ofa heat transfer fluid tube publicthis October.

This innovation limitsitself only for treating an outersurface of a heat transfer fluidtube. To benefit of thermalindustry the tube is for areceiver of a solar thermalpower plant. In solar thermalpower plants, solar fields aremade out of heliostats arrangedaround a tower receiver. Solarradiation is concentrated andreflected from the heliostats to areceiving area of the towerreceiver. In this receiving area,heat transfer fluid tubes arearranged in such a way, thatideally almost all of the solarradiation reflected from theheliostats is used for heating the

heat transfer fluid, flowing in

the tubes. In a heat exchangerthe heated fluid transfers the

heat to a working fluid of athermal power generationsystem. The heat transfer fluidcan be for example molten saltor water/steam. All, this is very well known practice.

In reality the receivingarea also has the physicalcharacteristic, that the radiationis not completely absorbed andthus the remainder of theincident radiation is reflectedoff the heat transfer fluid tubes.That leads to the fact, that thereceiving area has an elevatedtemperature (because of thebalance between absorption ofradiation energy and cooling bythe flowing medium) and thusthe receiving area also emitsradiation energy, as a functionof its own temperature and

emissivity characteristic.

The more efficient thereceiver area is absorbing theprojected solar radiation comingfrom the solar field, the smallerthe solar field can be for arequired output power of thetotal power plant. And since thesolar field is about 45% of thetotal power plant costs, this cangive a substantial cost saving.

Today the absorption ofthe receiver area is enhanced byapplying a coating to theoutside surface of the heattransfer fluid tubes. A typicalcommercially available coatingis Pyromark, as known from"Solar Selective Coatings forConcentration", AdvancedMaterials & Processes, January212. This coating increases the

absorption coefficient of the



28/30

heat transfer fluid tubes up to95%, which is very close to aphysical black body. Thus 95%of the incident radiation isabsorbed and only 5% isreflected. But the problem ofthis coating is that the coating

degrades by the hightemperature of the receiver areaduring operating conditions.Experiences from the past showthat after a few years, theabsorption coefficient hasdecreased to less than 90%.

In physics, a perfectblack body means that this bodyhas the capability to completelyabsorb the incident radiation, soit has an absorption coefficient

of 100%. This characteristic canalso be approximated byapplying a special geometry ofthe heat transfer fluid tubes inthe receiving area. In the heattransfer fluid tubes the incidentradiation is absorbed, and thereflected radiation is reflectedrandomly within the receiverarea and thus back to other heattransfer fluid tubes of thereceiver area. So the reflected

radiation is not lost, butabsorbed in a second instance,or even after more instances,depending on how often theradiation is reflected within thereceiver area.

Another way how to


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%all effect thrster. The electric field in a plasma do!le layer isso effecti$e at accelerating ions that electric fields are sed in iondri$es.

&orce'http'www.ircotec.com

Plasma &praying Process


29/30

achieve a physical black body istold by one research in US. It isknown to improve theabsorption of the heat transferfluid tubes for linearconcentrating solar thermal

power plants with an extraabsorber layer, this absorberlayer is generated by cold gassputtering. Thus by applyingsuitable method parameters, anincreased surface roughness canbe achieved by means of poresin the surface region of theabsorber layer.

NEM has aim to providean improved method for such a

black body-like surface of a heattransfer fluid tube.

They achieved their aim with the method having thesteps of providing a heattransfer fluid tube and treatingthe outer surface of this heattransfer fluid tube with ahydrogen plasma jet, so that aporosity in the range of a nano-

scale is created in a thin layer ofthat outer surface.

It is known from plasmatechnology, that a metallicsurface becomes porous, whenintensive hydrogen plasma isshot at such a surface. Applyingthis knowledge to this methodfor treating an outer surface ofheat transfer fluid tube, a

porous crust of approximatelyone micrometer thickness andporosity in the nano-scale rangecan be achieved in a thin layeron the outer surface of the tube.Interestingly, when treating thesurface of the heat transfer fluidtube with a hydrogen plasma jet, having an energy level withan Ion flux above 10e24 /m2s1, acrust with a layer thickness of

about around one micrometerand a nanometer structure

smaller than 50nm can becreated. For an incident solarradiation, the absorptioncharacteristics of such a treatedporous surface is very close tothe characteristic of a perfect

black body.

Typically, the heattransfer fluid tubes are made ofchrome-steel alloy, or especiallyfor higher heat transfer fluidtemperatures stainless steel ornickel alloy. And in case of usingnickel alloy as material for theheat transfer fluid tubes, theporous and thus high absorptionthin layer can be achieved

immediately on the basematerial of the tube.

Here, the surface of theheat transfer fluid tube is firstcoated with an extra layer of ahigh absorbing material, otherthan the material of the heattransfer fluid tube. Such a highabsorption material can be e.g.tungsten. Afterwards the

surface of this extra and thinlayer is treated with thehydrogen plasma jet. Because ofthe corrosion and high-temperature resilience oftungsten, the nano-structure

will not deteriorate byatmospheric conditions andhigh temperature duringoperating conditions.

Applying this treatmentto the heat transfer fluid tubesfor a receiver of a solar thermalpower plant leads to a constantabsorbing layer at the outersurface of the tube with anefficiency very close to 100%.

This means that the size of thesolar field can be at least 5%smaller, resulting in aconsiderable cost saving.

There is much moregoing like these type of 100%black body experiments all overthe world and solar industrystanding to be most benefitedfrom hereon.



30/30

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Solar Thermal Tech Mag November 2015