Linear concentrating solar collectors for solar medium-

temperature process heat: an exotic niche market has turned into

a wide range of offers for commercial and private customers – and

there is no end in sight to the technical developments.

Solar thermal power plant Puerto Errado 2 (under construction) in the south-eastern Spanish region of Murcia with Fresnel collectors from Novatec. The plant will have an installed capacity of 30 MWel. Photo: Novatec Solar

Solar process heat is becoming sexy

700 kW solar cooling of a stadium in Qatar with a two-stage absorption chiller Photo: Industrial Solar

Solar thermal ProceSS heat collectorS

Sun & Wind Energy 9/201170

Sun & Wind Energy 9/2011

The Intersolar had already shown: the solar medium-temperature heating market is on the move. In just two years, not only the number of

commercial suppliers of tracked process heat collec-tors increased about five-fold. Compared to the previ-ous market overview (see S&WE 8/2009, page 52), a remarkable variety of products has developed as well. The question then was primarily “Trough or Fresnel?”; in the meantime, individual manufacturers are now introducing entirely new technical concepts while others are looking towards more northerly regions to seek out new markets.

The overview of the technical parameters of the compared systems (see table, page 74) demonstrates the high diversification of products. The only similar-ity (even here, there is an exception) is that the prima-ry mirror of all these linear concentrating systems tracks the sun on one axis – either collectively as a trough mirror, or as a slightly bent Fresnel strip.

As before, there are systems that are designed for large-scale ground mounting installations: for ex-ample, the Novatec Fresnel collectors are joined to-gether in solar thermal power plants to a resulting to-tal length of 1,000 m (see S&WE 9/2009, page 48). But meanwhile, on the other end of the scale, sever-al products are offered whose collector arrays will easily fit onto a building roof.

A limiting factor may not only be the surface area but also the length of the plant. With some products, the minimum length of a collector row is 30 m or more. Compared to the merely 4.5 m long trough sys-tem from NEP, this is quite bulky. Regarding the main-ly targeted roofs of commercial or public buildings, this will rarely pose a problem but for single family homes it can already be different. For one project, only two segments of the NEP collector were joined together to form a system with only 2.4 m2 aperture area. The Dr. Vetter principle is favourable for geo-metrical limitations, a principle in which the troughs contain U-tubes and are mainly arranged in parallel.

As a rule, however, the “usual length” (see table) will be authoritative. This is partly because of the fixed costs for the control unit, which should be ap-portioned among a large number of modules, and al-so because of fixed losses at the collector end due to obliquely reflected light unable to reach the receiver. Such losses at the ends of rows can, in the worst case and at 20 m length, cost more than 10 % of the gross heat yield.

Things are also on the move regarding materials and construction. A number of composite structures have been added to the repertoire of classical con-cepts for glass, aluminium and stainless steel. Dr. Vetter employs a copper absorber and SRB Energy amazes with a double-sided absorbing flat plate col-lector with an ultra-high vacuum.

Despite great differences in technological means – in the end, the purpose of all plants is to generate process heat at a given temperature. Almost all col-lectors can deliver 250 °C, which is sufficient for many industrial process heat applications and the operation of an absorption chiller. The industrial

Solar thermal ProceSS heat collectorS

plant can even achieve 400 °C and thus easily meets requirements of distillation processes in the chemical industry.

A gauge for the utilisation of solar supply is the optical efficiency as based on direct irradiation. For its determination, the system status with the temper-ature of the heat carrier is set equal to the ambient temperature, in actual operation only true at the be-ginning of the morning heating phase, but it helps avoid any distortion caused by differing temperature levels, amongst other things. Here, almost all collec-tors achieve between 66 and 72 %. Novatec is the only provider to make a statement about the degrada-tion of the reflectors during operation, which, how-ever, only costs about three percentage points after 25 years with this product.

A second measure is the thermal power at 1,000 W/m² of direct irradiation at defined tempera-ture conditions. The greater spread of 440 to 680 Wth/m2 is also due to differing heat losses at the receiver. For the third measure, the maximum annu-al efficiency, only three companies provided any in-formation. They are between 42 and 44 %. The rea-son for the reluctance in imparting this highly prac-tical characteristic is the complexity of the calcula-tion involved, which can quickly lead to distortions – in addition to the problem of measured versus cal-culated values.

Looking at this data, what about the question “Trough or Fresnel?”

Soltigua – Fresnel and trough

Soltigua offers both designs. This begs for a system comparison of trough and Fresnel collectors, since the company’s internally consistent measurement methodology and technology rules out any distor-tions.

As expected, the trough collector gets more us-able heat out of the same aperture area. The differ-ence is even 20 %, which is twice as pronounced as two Mirroxx and NEP Solar designs featured in S&WE 8/2009, page 52, which, however, came from differ-ent suppliers and also differ greatly in several techni-cal aspects. The gap between “trough” and “Fresnel” in the area-related thermal collector performance cat-egory is evident when looking at the current data. However, the required ground area for a cross-system comparison is not proportional to the collector area: trough collectors require an even spacing in between to avoid mutual shading, in contrast to Fresnel sys-tems.

Francesco Orioli from Soltigua advises to decide based on the availability of the footprint: “Ultimately, as the Fresnel systems’ costs are similar to the costs of parabolic trough systems, the choice between the two systems is essentially an issue of space availabil-ity: with enough space, the parabolic trough is more convenient, while the Fresnel is more suitable for lim-ited space, particularly in rooftop installations.”

However, the investor can determine the actual purchase price only after a well-defined system has been calculated for a given location – Soltigua, like most competitors, refuses to indicate a price.

From a geometrical perspective, the two Soltigua models are not unusual: their forms resemble the re-spective competitor products that have been on the market for a longer time. The low height of the Fres-nel collector “FTM” does call for attention, however. With 3.59 m, it is not even half as high as the Novatec model and also significantly lower than the Industrial Solar product, which has grown by half a metre – compared to the Mirroxx predecessor from 2009 – to a height of 4.50 m.

It is fitting, then, that Soltigua also designed the Fresnel system for optional rooftop installations, in contrast to Novatec. Whenever the local building codes contain a height limitation, the authorisation of a towering system may fail because of just that. On

The PTM collectors are also explicitly designed for installation on building roofs or canopies. Photo: Soltigua

6 of 12 rows with NEP Poly-Trough 1200B trough collectors on the roof of a shopping centre in Newcastle, to the north of Sydney – DNI = 1,693 kWh/(m²a). According to the simulation, the plant is to annually provide 213 MWhth at a temperature level of 170 °C with a total aperture area of 346 m². Photo: NEP Solar

Sun & Wind Energy 9/201172

Helioakmi S.A. , NEA ZOI 19300 ASPROPYRGOS, ATTIKI - GREECE

Tel.: (+30) 210 55 95 624 - 210 55 95 625 - 210 55 95 626, Fax: (+30) 210 55 95 723

In te rne t : www.he l ioakmi .g r • e -ma i l : megasun@hel ioakmi .g rNo 1 under the sun

INTERNATIONAL RECOGNITION

World leader in Solar Water Heaters30 years before the others discover the power of the sunThirty years of manufacturing Solar Water Heaters,means thirty years of innovating in the field, andintroducing new technologies.Three decades of continuous development, combinedwith vast experience and extensive research, haveestablished MEGASUN products as leaders in most worldmarkets.Thousands of MEGASUN Solar Water Heaters are successfully in use in most countries of the world–from Athens to America and from Africa to Australia,to all Asia and Europe – providing continuous andabundant hot water.Today HELIOAKMI not only represent highly specializedtechnology and the experience of thirty years, but highquality systems which meet the highest demands.The solar water heaters are offered in both closed andopen circuit, in a range varying from 120 to 300 liters.The forced circulation systems are offered from 150liters up to 1000 liters, and they are offered ascomplete units or separately. Each systems consists of: • a storage tank with 1 or 2 heat exchangers (coils) • Collector(s) of 2,10m or 2,60m• Support base of the collector for flat roof or tiled roof• A carton box which includes all the connection

accessories, the differential thermostat, the pump, theexpansion pot, the antifreeze liquid, valves… etc.

Instantaneous efficiency curve of collector

Rend.= 0,767 - 0,37

1. Solar collectors2. Storage tank (boiler)3. Hydraulic kit4. Expansion pot5. Differential Thermostat

KATAX21*29,7_eng0108 11-01-2008 11:26 ™ÂÏ›‰·1

Sun & Wind Energy 9/201174

Solar thermal ProceSS heat collectorS

the other hand, the Soltigua trough collector“PTM” is 2.57 m high, almost one metre higher than the NEP Solar product. Of course, other important optimisa-tion factors weigh in when dimensioning the system.

The following description of the various process heat collectors on the market highlights the charac-teristics of the products.

Industrial Solar – 400 °C with Fresnel collectors

The Fresnel collector from Industrial Solar GmbH from Freiburg, Germany, is one of the two models that were already represented in the S&WE market survey two years ago – at that time, the original spin-off of the Fraunhofer ISE was still called Mirroxx. The first pro-totype is from 2005 and accordingly not much has changed. The collector modules have become both narrower and higher by half a metre compared to

2009, and the optical efficiency at 900 W/m² of DNI is now specified at 62.4 % instead of 62 %.

In contrast to NEP, Novatec and Soltigua, Industrial employ third-party receivers and Schott PTR 70 vacuum absorber tubes that are about 4 m in length, just as the collector modules are.

Industrial Director Tobias Schwind sees an appli-cation in conventional process heat and “direct steam generation, air conditioning and medium-sized power plants”.

Novatec Solar – Fresnel system for solar power plants

The Fresnel collectors of Novatec Solar GmbH from Karlsruhe, Germany (called Novatec Biosol AG until ABB acquired a 35 % stake in the company in March of this year) became known thanks to a Spanish 1.4 MW solar power plant, that is currently being ex-panded by the Puerto Errado 2 power plant which is about 20 times the size. The company also hopes for customers who will use the collectors for air- conditioning buildings with absorption chillers, as a source of process steam or for water desalination.

The maximum temperature was 270 °C in 2009; now it is 285 °C. The prototype of the new „Supernova“ collector has just gone into operation and is able to pro-vide overheated steam at a temperature of 450 °C.

Unchanged, however, is the philosophy of a trim, inexpensive system. The absorber tube is not placed inside an evacuated glass envelope but is surround-ed by a receiver housing insulated on top with miner-al wool. The primary mirrors are manufactured fully automatically and, like the supporting structure, are made of standard components.

PTM trough collector from Soltigua Photo: Alexander Morhart

Market overview trough and Fresnel collectors

Manufacturer Product name TypeLength of the smallest unit [m]

Usual length [m]

Width [m]

Maximum height [m]

Aperture width [m] 18

Net aperture area [m²]

Peak output [W/m²] 11

Primary reflector material

Secondary mirror material

Receiver materialReceiver supplier

Receiver diameter [cm]

TrackingOptical efficiency based on direct irradiation [%] 5

Working effi-ciency [%] 13

Maximum operating temperature of heat carrier [°C]

Special technical features

Dr. Vetter 9 IT.collectparabolic trough

2.16per control unit up to 200

0.56 n/a 0.50 1.00635 1;3;12 680 2;4;12

glass fibre reinforced polyamide

n/aglass tube 1.8 mm; copper absorber 0.2 mm

Narva 5.6 single-axis 63 up to 68 16 n/a 250 weight per module 14.5 kg

Industrial Solar LF-11 Fresnel 32.5 65.0 7.0 approx. 4.5 5.5 176 n/a clear glass aluminium n/aSchott - PTR 70

7.0 single-axis 66.3 17 44 (optimal location)

400

heat carrier heat transfer oil, water, superheat steam, up to 120 bar; max operational wind load up to 100 km/h

NEP SolarPolyTrough 1200B

parabolic trough

4.5 25 1.2 1.63 1.2 57.6 590sandwich structure of aluminium/ foamed plastic/aluminium

n/a stainless steel NEP 2.8single-axis; step motor, chain drive

68.5 1 43,9 2;19 220shipping in ISO compliant containers; installation onto roofs without lifting equipment

Novatec Solar Nova-1 Fresnel 44.8 224 to 985.6 16.56approx. 8.20

n/a 513.60 541 14 glass mirror, steel sheet aluminium n/a Novatec 6.2 single-axis 67 1;20 n/a 285fully automatic manufacture of primary reflectors; cleaning robot

Seler Industry 10 n/aparabolic trough

n/a n/a 1.3 1.0 n/a 2.6 n/aPET/aluminium/nitro-cellulose varnish

PET/aluminium/ nitrocellulose varnish

n/a n/a n/a n/a n/a n/a n/a n/a

Smirro Smirro 300parabolic trough

30.00 n/a 1.14 n/a n/a 3.4 about 440 8 n/a n/a stainless steel n/a n/a single-axis up to 70 8 n/a 250 °C on-site assembly possible

Soltigua

PTMparabolic trough

6.54 starting 19.70 2.40 2.57 2.40 n/a 627 2;7;15 aluminium n/a stainless steel Soltigua n/a single-axis 72 42 2; 21 250 (thermal oil) 110 (water)

max. operational wind load up to 93 km/h

FTM Fresnel 6.78 starting 19.30 5.24 3.59 3.75 n/a 502 2;7;15 aluminium n/a stainless steel Soltigua n/asingle-axis; multi mirror drive

60 n/a250 (thermal oil)110 (water)

no light sensors required for tracking

1 based on experimental results; T inlet not specified; 2 calculated/simulated; 3 with transparent level covering; 4 with covering, with double-sided Tinox-coated round absorber plate; 5 ratio of heat performance of individual collector and incident direct irradiation intensity of 1,000 W/m², if temperature of heat carrier (T inlet = T outlet) = ambient temperature (T ambi-ent); 7 solar position: longitudinal angle = 0°; transversal angle = 20°; 8 method of data collection and conditions not specified; 9 performance data with reservation as Solar Keymark certification not yet completed; 10 product is to be launched on the market at the beginning of 2012; 11 at 1,000 W/m² of direct irradiation; T inlet = 160 °C; T outlet = 180 °C; T ambient = 30 °C; 12 T outlet = 200 °C; 13 at T inlet = 160 °C; T outlet = 180 °C; 14 at 900 W/m² of DNI; T inlet = 100 °C; T outlet = 270 °C; 15 at 900 W/m² of DNI; T inlet = 180 °C; T outlet = 200 °C; 16 with covering depending on transmission; without covering a few percentage points more; 17 at 900 W/m² of DNI; 18 location: Seville [Spain]; 19 location: Mina Escondida [Chile]; 20 after 25 years; 21 at T inlet = 90 °C; T outlet = 100 °C; location: Seville [Spain]

Data source: company data and own calculations based on this information

SMEThermal 2012Solar Thermal Materials, Equipment and Technology Conference07 February 2012, Berlin, Germany

Conference management: Solarpraxis AGAnja Kleppek, Phone: + 49 (0) 30 | 726 296-305anja.kleppek@solarpraxis.de

Contact for sponsors: SUN & WIND ENERGYChristiane Diekmann, Phone: +49 (0) 521 | 595 547cd@sunwindenergy.com

Partner

www.solarpraxis.com

Gold Sponsors Silver Sponsorin cooperation Programm Advisors

Manufacturer Product name TypeLength of the smallest unit [m]

Usual length [m]

Width [m]

Maximum height [m]

Aperture width [m] 18

Net aperture area [m²]

Peak output [W/m²] 11

Primary reflector material

Secondary mirror material

Receiver materialReceiver supplier

Receiver diameter [cm]

TrackingOptical efficiency based on direct irradiation [%] 5

Working effi-ciency [%] 13

Maximum operating temperature of heat carrier [°C]

Special technical features

Dr. Vetter 9 IT.collectparabolic trough

2.16per control unit up to 200

0.56 n/a 0.50 1.00635 1;3;12 680 2;4;12

glass fibre reinforced polyamide

n/aglass tube 1.8 mm; copper absorber 0.2 mm

Narva 5.6 single-axis 63 up to 68 16 n/a 250 weight per module 14.5 kg

Industrial Solar LF-11 Fresnel 32.5 65.0 7.0 approx. 4.5 5.5 176 n/a clear glass aluminium n/aSchott - PTR 70

7.0 single-axis 66.3 17 44 (optimal location)

400

heat carrier heat transfer oil, water, superheat steam, up to 120 bar; max operational wind load up to 100 km/h

NEP SolarPolyTrough 1200B

parabolic trough

4.5 25 1.2 1.63 1.2 57.6 590sandwich structure of aluminium/ foamed plastic/aluminium

n/a stainless steel NEP 2.8single-axis; step motor, chain drive

68.5 1 43,9 2;19 220shipping in ISO compliant containers; installation onto roofs without lifting equipment

Novatec Solar Nova-1 Fresnel 44.8 224 to 985.6 16.56approx. 8.20

n/a 513.60 541 14 glass mirror, steel sheet aluminium n/a Novatec 6.2 single-axis 67 1;20 n/a 285fully automatic manufacture of primary reflectors; cleaning robot

Seler Industry 10 n/aparabolic trough

n/a n/a 1.3 1.0 n/a 2.6 n/aPET/aluminium/nitro-cellulose varnish

PET/aluminium/ nitrocellulose varnish

n/a n/a n/a n/a n/a n/a n/a n/a

Smirro Smirro 300parabolic trough

30.00 n/a 1.14 n/a n/a 3.4 about 440 8 n/a n/a stainless steel n/a n/a single-axis up to 70 8 n/a 250 °C on-site assembly possible

Soltigua

PTMparabolic trough

6.54 starting 19.70 2.40 2.57 2.40 n/a 627 2;7;15 aluminium n/a stainless steel Soltigua n/a single-axis 72 42 2; 21 250 (thermal oil) 110 (water)

max. operational wind load up to 93 km/h

FTM Fresnel 6.78 starting 19.30 5.24 3.59 3.75 n/a 502 2;7;15 aluminium n/a stainless steel Soltigua n/asingle-axis; multi mirror drive

60 n/a250 (thermal oil)110 (water)

no light sensors required for tracking

NEP Solar – irradiation directly onto the absorber

The Australian-Swiss company NEP Solar have ap-plied the same design strategy to the trough collec-tor. For CEO Johan Dreyer, having a vacuum around the absorber pipe is out of the question along with placing a cover over the primary mirror, as is done by

Dr. Vetter: “The use of clear glass or acrylic covers is not suited to our design. In cases where the receiver tube is located above the rim of the parabola, the in-coming and reflected light has to pass through the cover. This results in losses.”

For the time being, Dreyer is willing to accept a lower temperature level of 220 °C. His colleague Florian Pithan hopes that this level can be increased

Sun & Wind Energy 9/201176

Solar thermal ProceSS heat collectorS

in the future with a more effective coating: „A hot pipe at 400 °C loses far more heat to a 25 °C warm en-vironment than a 220 °C hot pipe does. We are work-ing with a highly absorbent coating for the receiver tubes, and affordable coatings are not durable at higher temperatures. However, there are interesting current developments on the market that we are ob-serving, of course.”

The maximum annual efficiency of the current version in Seville is by 1.4 percentage points lower than that of the Soltigua collector. With 48.6 %, the

NEP system at the Chilean location Mina Escondida with its intense direct irradiation level surpasses all other plants.

Dr. Vetter – the slightly different collector

Dr. Vetter GmbH in Baden-Baden, Germany, had only manufactured medical data measurement and control systems up to mid-2010. Regarding the parabolic trough collector “IT.collect”, some things are different than one would expect from established suppliers.

The merely 56 cm wide troughs, which the com-pany manufactures cost-effectively using fibre glass reinforced recycled plastic and Miro mirror film from Alanod, are not lined up behind each other, but in-stalled next to each other and mounted on oblique ro-tating axes facing south. This is made possible by the fact that a U-shaped pipe is in the line of focus in-stead of a simple absorber pipe.

The rounded absorber plate is made of copper coated with Tinox on one or both sides. The trough can be delivered with a flat cover made of glass, acryl-ic glass or film. The optical efficiency with a cover is 63.5 % to 68 % according to the company – without cover, a few percentage points more. More exact statements could be made once the Solar Keymark certification was completed.

Managing Director Michael Fleck-Vetter sees the main area of application “in the process heat extrac-

SRB Energy UHV Collector Photo: SRB Energy

Exploded drawing of the parabolic trough collector from Dr. Vetter. The transparent cover is not included in the standard version. Graphic: Dr. Vetter GmbH

SRB Energy – the entirely different collectorThose who passed the SRB Energy booth at the Intersolar fair were startled for a moment because the system exhibited was neither a conven-tional trough collector nor a pure flat plate collector. The “SRB Energy UHV Collector” consists of a flat plate collector with an ultra-high vacuum (UHV), which is mounted on two wing-shaped aluminium mirrors in a way that incident sunlight is first reflected to the centre, then upwards and finally to the lower absorber surface of the flat plate collector. The upper absorber surface receives both direct and diffuse solar irradia-tion – just like any traditional flat plate collector.

Utilising a highly selective coating, an ultra-high vacuum and double-sided irradiation, 220 °C hot heat transfer fluid can be drawn from this collector. Although the system is not tracked in the standard version, it is to reach an optical efficiency of 63 %.

SRB Energy is a joint project of the former CERN physicist Cristoforo Benvenuti and the Spanish automotive supplier Segura with offices in Valencia and Geneva. Although the company praises the suitability of the collector for more northerly regions with their high share of diffuse irradiation, they also do not reject the southern markets: an 800 kW plant for industrial solar cooling is to be delivered to Spain as soon as September.

. Product name: SRB Energy UHV Collector. Length of the smallest availablecollector unit: 3.40 m. Width: 1.66 m. Max. height: 1.240 m at 35°. Aperture width: 5.64 m². Net aperture area: 4.95 m². Output at 1,000 W/m² of direct irridation: 505 W/m². Primary reflector material: aluminium. Receiver: SRB flat plate high vacuum collector. Tracking: no trackingSR

B c

olle

ctor

– te

chni

cal d

ata

Sun & Wind Energy 9/2011 77

tion process, for example for garden centres, farms and laundries.” Of the surveyed sup-pliers, they were the only ones to give a price: without mounting, the collector is available for 499 €/m² of aperture area, plus € 2,499 for the tracking system that can align up to 100 m² of ground mounting collectors to the sun. This results in 523.99 €/m² for 100 m².

Smirro – jacket tubes without a vacuum

Smirro GmbH, located in southwestern Ger-many, has only recently separated from the PV supplier Solera. For the trough collector Smirro 300, they use mirrors made of ano-dised aluminium. The receiver is enclosed in an air-filled glass tube.

Seler Industry – undercutting prices as of 2012?The French film manufacturer Seler Industry SAS also plans a trough collector for early 2012. The technical information on the project is still vague but for Jean Pierre Bontems from Seler, the goal is “to be 30 to 50 % cheaper than our competitors in terms of structure, mirrors, installation and mainte-nance”.

Schott – CSP power plants bigger and hotter

While collector suppliers new to the market tend to cater to the medium temperature range and smaller plants, Schott AG from Mainz, Germany – the global market leader for receivers – sees a tendency in solar ther-mal electricity generation (CSP) towards high temperatures and larger collectors.

Schott Spokeswoman Christina Rettig hopes this will increase the overall efficiency by more than five percentage points. “We have designed a receiver for larger solar col-lectors – longer and larger in diameter. First, it is easier to focus sunlight onto a larger pipe. Second, wider tubes allow for a greater volume flow of heat transfer medium, which leads to an overall greater amount of heat.” To a certain extent, Rettig does not refer to the individual collector when she speaks of slim design strategy, but to the entire sys-tem: “If it is possible to capture more sun-light with a single collector, the power plant makes do with a lower overall number – fewer collectors, lower space requirements and shorter construction times.”

The Schott spokeswoman also intends to overcome the 400 °C limit of the heat carrier.

“Future solar arrays could either directly evap-orate water or use molten salt as a heat carri-er. Temperatures above 500 degrees Celsius would be possible.” Field tests at Schott are already underway for both systems. “For mol-ten salt, salt with the lowest possible melting point needs to be developed so it does not ‘freeze’ overnight in the solar array.”

For Christina Rettig, the most important markets currently are the USA and Spain, where the installation of 4.8 GW was planned according to the latest National Action Plan by 2020. “In the first phase of the ‘National Solar Mission’, CSP plants totalling a capacity of 500 MW are to be installed in India by 2013. The Moroccan government plans to invest € 8 billion in renewable energy by 2020. Among other things, several CSP projects are put out to tender. On top of that, South Africa is in the process of defining feed-in tariffs.”

Alexander Morhart

Further information: Dr. Vetter: www.itcollect.deIndustrial Solar: www.industrial-solar.de/cms/enNEP Solar: www.newenergypartners.comNovatec Solar: www.novatecsolar.comSchott: www.schott.com/english/index.html Seler Industry: www.selerindustry.com Smirro GmbH: www.smirro.comSoltigua: www.soltigua.comSRB Energy: www.srbenergy.nl

Literature:Buttinger, Frank: Entwicklung eines konzentrierenden Vakuum-Flachkollektors zur Prozesswärmeerzeugung. Diss., München 2009Häberle, A.; Zahler, C.; Luginsland, F. u. a.: Fresnel- Prozesswärmekollektor zur solaren Kälteerzeugung. Freiburg 2007Burkholder, F.; Kutscher, C.: Heat Loss Testing of Schott’s 2008 PTR 70 Parabolic Trough Receiver. Golden 2009. (= Technical Report NREL/TP-550-45633)Benvenuti, Cristoforo: Vacuum for thermal insulation: The SRB solar panel as an example. O. O. (Geneva), o. J.

Trough collector from Dr. Vetter. The focal line is inside the parabolic trough, so that a large proportion of the total diffuse irradiation is directed onto the absorber. Photo: Dr. Vetter GmbH

TYFOCOR® BRANDSenvironmentally friendly & biodegradable

www.tyfo.de • info@tyfo.de since

mor

e tha

n 30

year

s

TYFOROP - Your Specialist for Heat Transfer Fluids - Solar Fluids for all Thermal Installations

ChromeCoat A/S

Bla

ck Is

Bea

utIf

ul

LEADERS IN HIGHLY SELECTIVE COATING FOR SOLAR ABSORBER FINS

Danmarksvej 8 DK-4681 Herfølge · Denmark

Phone: +45 56 27 66 50Fax: +45 56 27 66 24

info@chromecoat.dkwww.chromecoat.dk

BlackSelectBest over-all efficiency

Best durability

Best corrosion resistance

Best thermal stability