S O L A R T H E R M A L

40 Sun & Wind Energy 2/2004

Powerful and efficient: Vacuum tubes for the world marketChinese companies are the world’s main manufacturers of vacuum tubes for solar thermal collectors.The leading companyin Europe is Thermomax from Northern Ireland.

Sales promotion in the provincial capital Jinan: Linuo Para-dimga exhibits its systems in a popular city centre square.

High-vacuum is the perfect insulator and vacuum tubes are theperfect heat accumulators in solar thermal collectors.High-tech production processes are therefore required to makesure that the vacuum is maintained.Chinese companies areworld leaders since 90% of the worldwide vacuum tube

production takes place in China. But there are also European compa-nies, rich in tradition, which specialize in vacuum tubes.

Mega market China

China is definitely the world’s largest solar thermal market1. For example, in 2003 China had an installed collector array of approx.10 mill.m2,while the whole of Europe2 only had an array of 1.4 mill.m2 .But there is conflicting information about the Chinese market seg-

ment:Some sources claim that 90% of the systems are small individual systems usually based on the thermo-siphon principle. Lorenz Hardegger (Onesystem, marketing partner of Tsinghua) estimates the per-centage of private operators at 70%, factories and hotels at approx. 20% and others such as greenhousesor drying plants at about 10%.The main markets are the suburbs of large cities like Shanghai and Beijingas well as medium-sized and small towns. Rural areas are only important in the south-east. The people inthe north and west of China are usually too poor to be able to afford a solar system.

Solar energy has possibilities where it can replace the normal electrical heating of domestic water.Wendelin Heinzelmann (Marketing Director of Linuo Paradigma) reports that,»measured in terms of purchas-ing power, electricity in China is about four times more expensive than in Europe – this and the poor in-frastructure are the reasons why solar technology has become a standard feature in China«.

The Chinese market is extremely fragmented. Even if viewed together, the largest companies still onlyhave a 25 % share in the installed collector array market.While there are approx.only ten vacuum tube man-ufacturers, the number of companies which produce collectors from the tubes is estimated to be at least2,000; but the true figure is most probably about 3,000. Many of the small regional suppliers are manufac-turer, dealer and fitter all rolled into one. »Marketing in China cannot be compared with the marketing in Eu-rope«, says Wendelin Heinzelmann. »If a customer wishes to purchase a solar system, he just travels to thestreet where all the manufacturers are located – the way it used to be in Europe.And then he enters one of themany shops which sell solar systems,or he goes to an exhibition where most of the companies are represented«.

Glass specialist: Linuo

Vacuum tubes have a two-thirds market share,and are therefore considerably more prevalent in China thanflat-plate collectors.While the flat-plate collectors are manufactured and marketed regionally by numeroussmall suppliers, tube collectors seem to be the responsibility of international operating companies.The Li-nuo group, which in addition to glass products also supplies chemical and pharmaceutical products, pro-duced nearly 15 mill. tubes in 2003 (approx. 2.5 mill. m2) and refers to itself as China’s largest manufactur-er. Independent sources estimate the actual sold collector array to be about 1 mill. m2. This large privateenterprise, founded in 1994 and based in Jinan, recorded an annual turnover last year of US$ 360 mill.witha workforce of 13,000. Linuo uses online absorption and emission measurements of the absorber coating

S O L A R T H E R M A L

Linuo Paradigma shop in Zaozuhuang: The shop owner sells between 300

and 500 systems annually.

Precision is necessarywhen fusing off the tubes.Photo: Thermomax

Just around the corner:In China solar systems are

sold in the street.Photos (6): Linuo Paradigma

41Sun & Wind Energy 2/2004

during tube production. Random, intensive qualitytesting of all the products is carried out before theyleave the factory.

Business tradition: Tsinghua

Tsinghua Solar is a Chinese manufacturer rich in tra-dition. Professor Yin Zhiqiang from the TsinghuaUniversity in Beijing introduced what is known asthe Sydney-tube principle to China more than 25years ago and also developed the Tsinghua-tube.In the meantime, the annual production capacityof the Beijing-based company has become 7 mill.tubes. A collector array of 380,000 m2 was sold lastyear according to company sources.

»95% of tube production in China is still based onProf.Yin’s patent,« says Lorenz Hardegger from One-system in Switzerland. Professor Yin, who is in his

seventies, still assists the Chinese group as head ofthe science and technology department.

Onesystem has taken on the task of marketingTsinghua-tubes and collectors outside China and hasrepresentatives with various distribution channel levels in Europe, the Middle East and South Ameri-ca.»Tsinghua is number one when it comes to usingstate-of-the-art automated process and productionstandards in accordance with international stan-dards.An after sales service includes »product track-ing«. This allows each delivered unit to be checkedduring its entire service life,« Hardegger continues.»This high standard is underlined by an ever increas-ing number of awards. For example, Prof. Yin wonthe World Technology Award for energy in 2003«.

The Beijing-based company produces closedloop heat-pipes and direct flow tank systems inwhich the solar circuit is separated from the do-mestic water circuit.Furthermore,there are also col-lectors with flat,coarse reflectors.Tsinghua productsare situated in the high-price segment. The maincustomers are well qualified people usually em-ployed in the public service.The marketing systemis based on exclusive agents, who are located ineach city and who each have between three and tendistributors.These distributors employ between fiveand 20 people who are quite often salesperson andfitter all in one.Tsinghua designs large systems in co-operation with engineers and technicians.

S O L A R T H E R M A L

42 Sun & Wind Energy 2/2004

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Heat-pipe according to the Sydney principle:The aluminium heat guide plate transfers theenergy from the inner glass tube with the ab-sorber coating to the copper heat-pipe tube.

Tube production process:Vacuum pumps draw vacu-um into the space between

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43Sun & Wind Energy 2/2004

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The Stapla product range includes various models of machine distinguished by their degree of automation. Solstar is the modestly priced version for stationary production of absorber strips. The RSK ultrasonic seam welding unit is used for continuous welding of copper absorber surfaces up to 6 metreslong. The fully-fledged solution for welding absorber panels with automatic loading and unloading is marketed as the RFL welding unit.

The climber: Himin

The third in the trio is even larger than Tsinghua:The Himin Solar Energy Group was established in1995 by Prof.Yin’s former student Huang Ming,whois today also Deputy of the National People’s Con-gress. This Beijing-based company with 3,300 em-ployees has experienced exceptional growth dur-ing the past two years and had an annual turnoverof US$ 59.7 mill. in 2003, selling 500,000 solar sys-tems. Himin also claims to be the largest Chinese,and therefore also the world’s largest, manufactur-er of solar collectors with an annual production of15 mill. tubes. Independent market studies esti-mate a double-figure market share.That would re-sult in an installed collector array of at least morethan 1 mill. m2.

Himin manufactures vacuum tubes with outsidediameters of between 47 and 58 mm in accordancewith a patent from Sydney University.The sputtered,multi-layered metal-aluminium nitride absorberlayer is designed to be stable up to temperatures of380 °C. The company uses inline measurements tocheck the quality. 2,208 exclusive nationwide mar-keting partners sell Himin products.

With German know-how:Linuo Paradigma

Shandong Linuo Paradigma, based in Jinan, has yetto achieve the sales figures of Himin. In 2001 Linuoand the German vacuum tube specialist Paradig-ma entered into a joint venture. The company sold250,000 m2 in 2003 and has therefore already be-come a leading supplier in the Chinese market in avery short space of time. Another German-Sinopartnership also plays a key role in the productionof collectors:Linuo supplies the tubes and Ritter So-lar from Germany the CPC reflectors. The productsare marketed directly in more than 1,000 mainlyfranchise shops. In Jinan the group also runs 20 ofits own sales shops.

The company endeavours to get ahead of itscompetitors with high quality and German technol-

ogy. In addition to the reasonably priced thermo-siphon tank collectors, which are quite common inChina, Linuo Paradigma is also trying to enter themarket with solar system solutions, and more re-cently also with solutions for retrofitting or replacingexisting large scale solar systems.Typical large sys-tems in China are unpressurised thermosiphon sys-tems. The advantages: low costs, no safety require-ments and low risk of freezing during frosts.The dis-advantages: corrosion, calcination and therefore reduced service life as well as high circulation losses.These disadvantages do not exist in a pressure-driven dual circuit system in which the heat is tapped via a heat exchanger.Moreover,higher temp-eratures can be generated and the hygienic condi-tions are superior.

While the parent company Linuo exports a greatnumber of tubes, Linuo Paradigma has only thisyear undertaken greater efforts to enter foreignmarkets.However, it already has marketing partnersin Australia, New Zealand,Thailand, Brazil, Uruguay,Iran, India, Korea and Turkey. The remaining Euro-pean market is the responsibility of Paradigma andits subsidiary Ritter Solar.

European pioneers: Thermomax

Compared with Chinese ones, the manufacturers of vacuum tube collectors in Europe are minute.Market leader in 2003 was the Northern Ireland-based company Thermomax3 with a collector arrayof 50,000 m2. The company, founded by Prof. Dr Faramarz Mahdjuri (inventor of the heat-pipe) in1981,employs 200 people.In 2003 it achieved an an-nual turnover of US$ 18.12 mill. While the Sydneyprinciple uses a glass Dewar placed over liquid filled tubes, Thermomax tubes have the absorberwith a drain inside the evacuated tubes. A glass-metal junction seals the system.

In recent years Thermomax has invested greatlyin quality assurance. An automatic camera precise-ly measures the penetration depth of the metal in-to the glass up to 0.01 mm – an important detail forthe capacity of the connection. Helium leakagetests at three different stages of the manufacturingprocess guarantee vacuum quality.The absorptionand emission of the absorber material is alsochecked via random testing. And researchers atThermomax have recently developed a solar simu-lator.»Heat-pipes from the British Isles are renownedthroughout the world for their unique protectivequalities,« Boris Bauer (Head of Research and De-velopment) points out a distinctive feature of theThermomax technology: In the event of stagnationat a maximum temperature of 130 °C, a bi-metal disc in the condenser of the Mazdon tubes closes,thereby preventing the return of the condensedfluid. When the temperature falls below the maxi-mum level, the disk retracts, allowing heat transferto recommence. This function is carried out by amemory metal spring in Memotron tubes (heat-pipes with wet connection).

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44 Sun & Wind Energy 2/2004

Sino-German co-opera-tion: The German FederalForeign Minister JoschkaFischer officially opened

the new Linuo Paradigmaproduction and adminis-

tration site in July. Fromright to left: Chocolate

producer Alfred T. Ritter(owner of Ritter Sport andParadigma), Xu Young Mei(Linuo Paradimga Export),

Han Yuqun (Governor ofShangdong Province),

Joschka Fischer (GermanForeign Minister), Carsten

Aschoff (CEO Linuo Para-digma)

High degree of automa-tion: The machine removes

the protective film of thereflector.

Photos (3): Ritter Solar

45Sun & Wind Energy 2/2004

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Made in Germany: Ritter Solar

The largest German manufacturer of vacuum tubecollectors is Ritter Solar. The company, founded in2000 and located near Stuttgart, is a subsidiary of Paradigma and employs 34 people. Ritter Solar purchases the tubes from Linuo and manufacturesthe tube register, the collector frames and theparabolical CPC reflectors. The main collector cus-tomer is Paradigma, even though the company alsosupplies other OEM customers. A collector array of33,000 m2 was produced in 20033.Ritter Solar is soonto introduce a sealed heat-pipe tank system to themarket due to the large demand in southern Eu-rope for thermosiphon systems.Marketing for south-ern Europe is carried out by Synergy based in Lo-drone, Italy, while marketing for northern Europe iscoordinated from Germany.

During incoming inspections Ritter Solar usesrandom testing to check the absorption and emis-sion of the absorber material.The quality of the vac-uum is inspected via k-value measurements of thetubes. Final inspection consists of extensive visualchecks and a pressure test of the tube register. Be-fore the collectors leave the factory they are cov-ered with a sun-protective film.This reduces the riskof fitters being burnt by hot parts when installingthe collectors under direct sunlight.

Ritter Solar does not have a temperature limit inthe event of stagnation. The tubes can heat up to295 °C.»We do not require a temperature limit,« saysBernd Clauss (Ritter Solar). »Since there are no met-al-glass connections, the materials can expand in-dependently without thermal stress occurring«.Even if the tubes are operated with anti-freeze,

hardly any crack problems arise with the fluid.Up tonow, this problem has only occurred with 0.09% ofthe approx.19,000 Ritter systems which have alreadybeen sold;and also only with the large systems whichwere not correctly evacuated. According to Clauss,»Oxidation of the anti-freeze only occurs when there is air in the system«.Therefore, it is extremely important that correct evacuation is carried out by

the fitter with the aid of aspecial flush pump duringinstallation.

Swiss quality:AMK Solac

The Swiss company AMKSolac, founded in 1989,al-so plays a role in the Euro-pean market. The CEOKurt Amrein states thatthe company produced acollector array of 15,000 m2

in 2003. The company’smain markets are Ger-many, Austria, the UnitedKingdom, Sweden, Spain,Hungary and the Czech

Republic. AMK is represented in these markets bymarketing partners. Tank systems are sold to cus-tomers in southern Europe and North Africa.

AMK Solac manufactures collectors according tothe Sydney principle and acquires the tubes fromChina.»Our supplier is not one of the big three in Chi-na«,says Kurt Amrein.AMK Solac carries out randomtesting of each delivery in order to check absorp-tion and emission.For important parameters such asthermal expansion, absorption and emission thereare tolerance ranges which have to be adhered to.Each and every collector which leaves the factoryreceives a serial number and all the production datais recorded on a quality control data sheet.

The company offers three systems: The OPCcollector has a parabolic CPC reflector. The systemis designed in a way that if stagnation occurs at ap-prox. 140 °C the medium evaporates completely,thus preventing a further increase in temperature.A flat, white reflector is used for the lower-pricedDRC collector. The sealed tank system functionswith heat-pipe tubes and uses a flat, coarse mirroras reflector. Y

Jens-Peter Meyer

1 Source: Paradigma2 Source: ESTIF3 Source: Sarasin study

Information:www.linuo.comwww.thsolar.comwww.himin.comwww.linuo-paradigma.comwww.thermomax-group.comwww.rittersolar.dewww.paradigma.dewww.amk-solac.com

S O L A R T H E R M A L

46 Sun & Wind Energy 2/2004

Sealed tank system from Switzerland:

AMK uses heat-pipes.Photo: AMK Solac

Production of the CPC reflector: Ritter Solar de-

velops the machines.

Pressure test: The imper-viousness of each collector

is checked via the leak detector at 10 bar excess

pressure.