PV on noise barriers

PROGRESS IN PHOTOVOLTAICS: RESEARCH AND APPLICATIONS

Prog. Photovolt: Res. Appl. 2004; 12:485–495 (DOI: 10.1002/pip.566)

SHORT COMMUNICATION

PV on Noise BarriersThomas Nordmann* and Luzi ClavadetscherTNC Consulting AG, Erlenbach, Switzerland

PV on noise barriers has been around for 14 years. During this time considerable

progress has been achieved not only on the PV module technology, but also in the

construction of photovoltaic noise barriers (PVNB). The first plant was built in

Switzerland in 1989; at present there are numerous plants with a total documented

power of about 850 kWp in operation in Europe. This paper gives a short overview

on the progress and state of the art of PVNB in Europe. Copyright # 2004 John

Wiley & Sons, Ltd.

key words: bifacial; dissemination; grid-connected; large grid-connected PV systems;

module integration; performance; supporting structures; PV noise barriers

WHY PV ON NOISE BARRIERS?

In some European countries noise protection measures along motorway and railway systems in built-

up areas are now required by legislation. In these countries the requirements have now been identified

and the noise protection structures are planned or already under construction. Using these noise

barriers as substructures for PV modules or to integrate the PV modules into the noise barrier system has many

advantages.

Double use of land resources

The strip of land along a rail or road infrastructure in a built-up area, can be utilised for noise protection and also

for the placement of PV modules to produce electric energy.

High potential

There is a high potential for photovoltaic noise barriers, especially in densely populated and industrialised

areas, which also have a high usage of electric energy. In recent studies the potential to produce electric energy

along motorways and railways in Europe has been quantified.

Bulk prefabrication

Mechanical and electrical prefabrication of photovoltaic subsystems or complete photovoltaic noise barriers has

been employed in most of the grid connected PV plants built along transport infrastructure in the past 14 years.

Copyright # 2004 John Wiley & Sons, Ltd. Received 1 April 2004

* Correspondence to: Thomas Nordmann, TNC Consulting AG, Erlenbach, Switzerland.yE-mail: [email protected]

Special Issue

Public ownership

A highway project, including noise protection, is usually a public project, and the additional PV plant can be

included in the finance plan, the planning and building process as a whole.

Easy access

The transport routes can be used for the construction and maintenance of the PVNB systems. Appropriate trans-

port vehicles are already available for general road or rail maintenance.

Potential

In a European study carried out by seven partners from six countries (Figure 1) the energy potential of PVNB

was quantified.1–3. Existing as well as planned road and rail systems were considered. The theoretical potential,

technical potential and short-term potential were calculated for the participating countries. The technical poten-

tial represents the existing and the planned road and rail noise barriers within the next five years. The generating

capacity was calculated considering the topology of the transport system as well as the meteorological data for

the relevant region.

The technical potential for the six countries is a generating capacity of 800 MWp generating 680 GW h of

electrical energy per year (Table I). Because of the different stages in the planning and realisation of noise

protection measures in Great Britain, Italy and France, only existing noise barriers were considered. A realistic

potential for these countries would be considerably higher.

Figure 1. Geographical distribution of the generating capacity and the electrical energy generated

486 T. NORDMANN AND L. CLAVADETSCHER

Copyright # 2004 John Wiley & Sons, Ltd. Prog. Photovolt: Res. Appl. 2004; 12:485–495

EXAMPLES

The first PV plant on a noise barrier was built in Switzerland in 1989.4 Others followed in Austria, Germany and

the Netherlands.

The average size of the PVNB in these examples is 77 kWp. The largest plant is that in the Netherlands

(220 kWp) built in 1998. Over the years there has been a significant reduction in the overall cost this type of

Table I. Technical potential of the generating capacity and the electrical energy generated along the road and rail systems of

the six countries investigated

Technical potential Switzerland Germany Netherlands Great Britain Italy France Total

Noise barriers (km)

Along motorways 303�8 1525�0 475�9 204�0 50�7 352�2 2911�7Along railroads 94�7 600�0 444�6 16�5 7�0 139�0 1302�1

Generating capacity (MWp)


Total 73�4 388�3 197�0 41�9 10�9 89�7 801�3Electrical energy generated (GW h/yr)


Total Energy yield 67�0 329�9 157�3 32�0 11�5 85�1 682�8

Figure 2. Geographical distribution of the generating capacity and the electrical energy generated

PV ON NOISE BARRIERS 487


plant from 16 to 7 s/Wp. This mainly due a fall in the price of the PV modules, but also because of the experi-

ence gained from previous projects in terms of planning and construction and a higher level of integration. The

energy produced by a PV plant along a motorway depends, as it does with all PV applications, mainly on the

efficiency of the PV module, the geographical location of the plant and the orientation of the PV array.

100 kWp Domat/Ems A13, Switzerland

Built in 1989 this 100 kWp plant (Figures 3 and 4) still delivers 1000 kW h/kWp per year to the local grid4. It is

highly visible and has had quite an educational effect. The glass surface of the modules has never been cleaned,

but no significant degradation of the array efficiency has been observed. This is remarkable since the modules

are so near a motorway.

The plant operated without any major interruptions for 10 years. During the 11th and 12th years there were a

series of major interruptions and some minor but important components of the inverter unit had to be replaced.

The time between failure and repair appeared to be rather long. Since May 2002 the plant has been back in full

operation.

100 kWp Giebenach A2, Switzerland

This 100 kWp plant (Figure 5) was built in 1995 and on average produces 850 kW h/kWp. The modules face

away from the motorway, and it was therefore possible to use a wider and consequently shorter area for the

PV array.

220 kWp PVNB 220 A9, Netherlands

This large 220 kWp plant (Figure 6) near Amsterdam on the A9 comprises 2160 100 W modules, each with a

100 W micro-inverter.7 Initial intensive monitoring of all inverters was necessary, and owing to malfunctioning

some units had to be replaced. Now the plant performs as expected.

This plant demonstrates that it is possible to obtain full system modularity, while maintaining reliability and

efficiency. At the time of construction the inverter technology was relatively new and showed some technical

problems, but these could be solved effectively.

Figure 3. Domat/Ems A13 plant, Switzerland



75 kW Alpha A1, Switzerland

This 75 kWp plant (Figure 7) has 24 mini-inverters. Unfortunately there is some shading of the lower row of

modules during the summer months.

DESIGN COMPETITION

In 1996 a competition for noise barrier designers, PV suppliers and PV installers was hold in Germany and

Switzerland, resulting in the construction of three 10 kWp PVNB plants in Germany and three 10 kWp PVNB

plants in Switzerland.6,8 All the plants are a unique combination of noise protection and PV technology. The six

innovative prototypes are showpieces and living examples of PVNB along road and rail routes. All the plants

were initially monitored for two years. Table III and IV show annual yield, irradiation and mean module

Figure 4. Monitored data over 13 years of operation, Domat/Ems PV plant

Figure 5. Giebenach A2 plant, Switzerland



temperature for each plant during the monitoring period. The variation in the module temperature is due to the

difference in construction of the arrays.

The three Ammersee plants are on the A96 motorway near Munich and are easily accessible from the layby.

9 kWp Fabrisolar, Germany

The Ammersee Fabrisolar plant (Figure 8) employs so-called cassette technology and one single inverter. This

PVNB uses a combination of sound reflection and sound absorption.

Figure 6. PVNB on the A9, Netherlands

Figure 7. Alpha A1 plant, Switzerland



9 kWp Zueblin, Germany

The Ammersee Zueblin plant (Figure 9) employs shingle technology and multiple micro-inverters. Its operation

is based on a combination of sound reflection and sound absorption.

10 kWp DLW Metecno, Germany

The Ammersee DLW Metecno plant (Figure 10) employs zigzag technology and one single inverter. This is a

sound-reflective PVNB plant.

This R&D project was carried out by TNC as part of the international design competition. As all the plants

are located in the same parking and rest area on a motorway near Munich it allows for a side-by-side compar-

ison of the designs. The Fabrisolar design in Figure 8 utilises a new type of layout with a relatively compact

design. The Zueblin design in Figure 9 could also to be used in a retrofit situation. The DLW Metecno design in

Figure 10 is aesthetically and functionally the most attractive design and shows that a noise barrier can be opti-

cally transparent. The sound-reducing capability of this barrier is based on reflection rather than absorption.

Two of the Swiss plants are located at different points on motorways, and one plant on the railway in the

Zurich region.

Table IV. Three 10 kWp pilot plants in Switzerland

System power Yield Irradiation

Plant Installed Type (kWp) (kW h/kWp) Monitored (kW h/m2) T Module (�C)

Aubrugg 1997 Bifacial 8�27 681 1998–2001 1202 26�5Wallisellen 1998 Zigzag 9�65 497 1999–2001 872 43�9Bruettisellen 2000 Cassettes 8�2 446 2000–2001 730 34�8

Table III. Three 10 kWp pilot plants in Germany

System power Yield following installation) Irradiation

Plant Installed Type (kWp) (kW h/kWp) (kW h/m2) Tmodule (�C)

Fabrisolar 1998 Cassettes 8�77 751 1162 40�9Zueblin 1998 Shingles 9�13 814 1219 43�9DLW Metecno 1998 Zigzag 10�08 794 1032 27�0

Table II. Overview of some large documented PVNB plants in Europe

System power Yielda Monitored Irradiation

Country Plant Installed Costs s/Wp (kWp) (kW h/kWp) (kW h/m2) Reference

Switzerland Domat/Ems A13 1989 16�27 103 1211 1997 1522 5

Switzerland Magadino SBB 1992 13�50 103 935 1999 1473 5

Austria SeewalSwitzerlandn A1 1992 13�50 40

Germany Rellingen A23 1992 30

Switzerland Giebenach A2 1995 12�08 104 969 1997 1152 5

Germany Saarbrucken A6 1995 8�00 (9�40) 60

Netherlands Utrecht A27 1995 10�50 55

Germany Ammersee A96b 1997 28 6

Switzerland Zurichb 1998 26 6

Netherlands PVNB 220 A9 1998 10�61 220 795 1999 1047 7

Switzerland Alpha A1 2000 > 7�0 75 805 2001 1176 5

aMaximum annual yield achieved by the plant over the period monitored.bDetailed information is given in Tables III and IV.



8 kWp Wallisellen, Switzerland

The Zurich Wallisellen plant (Figure 11) uses zigzag technology and 45 mini-inverters. This PVNB is based on

a combination of sound reflection and sound absorption.

8 kWp Bruettisellen, Switzerland

The Zurich Bruettisellen plant (Figure 12) uses vertical cassette technology and one single inverter. It is also

based on a combination of sound reflection and sound absorption.

Figure 8. Ammersee Fabrisolar plant with cassette technology

Figure 9. Ammersee Zueblin plant with shingle technology (left-hand side of the picture)



8 kWp Aubrugg, Switzerland

The 8 kWp Aubrugg plant (Figure 13) is located near Zurich, on a north–south motorway flyover and is the

world’s first PVNB bifacial plant.9 The modules are ASE bifacial prototypes and act as sound reflecting ele-

ments. One side is exposed to the morning sun and the other to afternoon sun. In theory the annual yield should

be equal to or higher than the yield of a south-facing array. Owing to the cell design and manufacturing process

the back surface has a slightly lower efficiency. The annual performance is therefore somewhat lower than

might be expected for a fully symmetric bifacial array.

The three sister plants in Figures 11, 12 and 13 are the corresponding three R&D projects of the international

design competition. The plants are built and operated in Switzerland. The Wallisellen plant in Figure 11 is the

Figure 10. Ammersee DLW Metecno plant with zigzag technology

Figure 11. Zurich Wallisellen plant with zigzag technology



first PVNB application along a railway line. Possible electromagnetic interference between the railway and the

inverter was studied and proved to be no issue. The Bruettisellen plant in Figure 12 is the first PVNB application

using thin-film module technology. The Aubrugg plant in Figure 12 is the worlds first PV plant using bifacial

prototype cells on a north–south motorway. For a proper interaction of the inverter with the bifacial modules

adjustment of maximum power point tracking behaviour of the inverter was necessary. Bifacial PV technology

was used because it may expand the potential of PV on noise barriers substantially.

CONCLUSIONS

Energy potential

With a technical potential of 680 GW h per year, PV on noise barriers in central Europe could be an interesting

contributor to the growing green energy market. Existing or future legislation on sound protection from

Figure 12. Zurich Bruettisellen plant with vertical cassette technology

Figure 13. Bifacial Zurich Aubrugg plant with bifacial technology



motorways and railways in individual countries could create volume and thereby enable cost reduction. PV on

noise barriers does not require special land resources and the costs for mounting structures can be shared

between the PV system and the barrier. Various PVNB technologies have already been implemented and tested.

Particularly the use of bifacial modules may enhance the potential of PVNB.

Design considerations

The glass surface of a PV module can only be applied for sound reflection. In situations where absorption of

sound is required a cassette or a zigzag model has to be applied, enabling a combination of sound reflection and

sound absorption. Because PV current cells operate most efficiently at lower temperatures great care should be

taken in the design of sound absorption cassettes to allow sufficient cooling of the PV modules. In layered or

zigzag arrangements the positioning of modules has to be such that (partial) shading is avoided at all times.

Contamination from vehicles on the motorway can have a negative impact on performance if the modules

are mounted too low and near the surface of the road.

Cooperation

Successful use of PVNB requires a close cooperation between sound and PV experts, as well as of the road

authorities and the financiers of the PV system. To achieve cost reductions for the PV part of the project inte-

grated systems are to be preferred to retrofit systems. With fully integrated PVNB systems a clear understanding

of the cost substitution should be aimed for. In an ideal situation the noise barrier and the PV plant should be

planned and realised at the same time as a single project.

REFERENCES

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results for Europe, results for Switzerland. December 1999, available from: www.tnc.ch.

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PV on noise barriers