Energy producing noise barriers in Lerum, Sweden
The Swedish Municipality of Lerum is situated in the expansive Gothenburg region and is divided by major thoroughfares for both road and rail traffic. Noise is one of the greatest environmental problems in Lerum.
Lerum aims to be Sweden’s leading green municipality by the year 2025, or sooner. In addition to tackling noise pollution, the municipality aims to invest in energy-saving and renewable energy technology in order to cut its emissions of greenhouse gases.
In a unique and innovative approach, the Municipality of Lerum will build a 400m noise barrier with sun energy production for district heating system. The project is co-funded by the LIFE+ programme by the European Commission.
Project partners are: the Municipality of Lerum, SP Technical institute of Sweden, Lerum Fjärrvärme AB and the Swedish Transport Administration.
You can find a more detailed description of the project on www.noisun.eu and in Pan European Networks: Science & Technology, issue 05, December 2012.
Deciding the best location for the facility is a major challenge. The project has made an analysis of a number of different places in the Municipality of Lerum, in order to choose the most suitable location for the facility.
The very centre of Lerum has been chosen since there are many advantages compared to the other investigated areas in the area. The noise disturbance is larger and the number of people exposed to noise is greater at the current location. A solar collector facility can be made larger at this site than in the other proposed sites and thus produce more renewable energy. In Lerum there is an accumulator tank at the district heating plant, which greatly facilitates the implementation, hence the energy can be stored and the heat be taken care of. A measure to reduce noise in Lerum will have a greater impact, both in terms of reduced costs of noise nuisance and in terms of increased property value.
Utilisation of the energy in the district heating system has also been addressed. Calculations show that, the solar collector facility should be connected to the district heating network flow line. The alternative; to use a separate line to the accumulator tank is considerably more expensive and will cause heat losses during transport.
The project will focus on a solution where the solar collector facility is connected to the district heating network flow line and the existing accumulator tank is used.
Managing the instantaneous power to the district heating network is a big challenge, when the boiler doesn’t need to produce as much energy e.g. a Sunday afternoon during the summer.
The peak power capacity of the solar collectors is higher than the minimum demand in the district heating net. This means that in some periods during the summer, the solar facility will produce more energy than can be handled in the district heating network. To solve this, we have discussed various solutions, such as different inclination of the solar collectors, absorption cooling, water or air cooling.
We have found that the solar collectors should be placed in a 60˚ angle and also have a water cooling system for emergency cooling to handle the periods with excess capacity.
In the planning of the solar collector noise barrier there are various safety regulations to handle, mainly due to the short distance to the railway and the local road. A few examples of the requirements are; distance to high-voltage parts, distance to tracks and to the local road. The barrier will be placed as close to the tracks as permitted in order to get the best noise reduction. Thanks to the 60˚ inclination of the solar collectors, the barrier can be high enough while the safety distance to the high-voltage parts is managed. To meet the safety requirements for the local road, a crash barrier likely will be needed.
Geotechnical field surveys have been carried out on the stretch for the solar collector noise barrier. The survey is made in order to determine soil sequence, soil type, piling possibility, earth resistance and groundwater levels. The results of the survey will provide the basis for selection of technical solutions in the project.
The stretch varies in elevation, which means that the barrier needs to be levelled in steps, to find both an appealing and a cost-effective solution.
A design proposal will be developed, including the levelling and the side towards the local road. The side towards the local road is preferably designed with trellis and vegetation in maintenance free and cost-effective solution.
In order to build the facility, a building permit must be applied for and granted. Drawings of the facility will be produced and, together with the design proposal constitute the basis for the application.