Energy saving during silent hours

These days street lighting is taken for granted. It gives us a sense of security and we expect to have it near our houses and even along the main highways. The contributions by Enemalta, the ADT and the local councils to extend and maintain street lighting systems are paying off, because one can say that we have quite good standard of public lighting.

Yet few might have stopped to consider what the running of street lighting systems and the floodlighting of buildings and monuments implies in terms of energy consumption and its detrimental effects on the environment. Official figures for street lighting energy consumption are not available, but it is estimated that the total consumption is around 30GWh, which is equivalent to the annual consumption by about 5,000 Maltese households, each of which uses an average of 16 units daily.

Assuming that the cost of electricity is equivalent to the domestic rate including surcharge, that is around €0.14 per kWh, then the annual street lighting bill works out at €4.2 million. In real terms, it is even more than this amount, given that the current domestic rate quoted is subsidised.

Apart from direct cost, there is also the environmental cost in terms of annual gaseous emissions, which work out at around 27,000 tonnes of CO2, 70 tonnes of NOx, and 160 tonnes of SOx. Another issue is, of course, light pollution into the night sky.

A solution to partly offset these costs is to resort to street lighting dimming during the silent hours, say from midnight onwards. This applies mainly to our main highways, such as, for example, the road from Qormi to Rabat via Zebbuġ and the St Paul's Bay bypass, where traffic is quite light after midnight.

These days there is a variety of equipment that can be installed relatively easily to dim street lighting levels. Dimming can take place gradually over several minutes to allow an observer's eyes to adjust. In fact, dimming the intensity of street lighting by 40 per cent would hardly be discernable.

It is estimated that if street lighting had to be dimmed by 40 per cent from midnight onwards there would be an overall saving of 20 per cent in consumption, which implies annual savings of about €0.84 million. Gaseous emissions and light pollution would likewise be reduced. Moreover, it is claimed that the life expectancy of the lamps is extended when dimming is introduced, hence maintenance costs are also reduced.

State-of-the-art technology makes it possible to programme dimming remotely in such a way that it would not be resorted to in certain areas, and certain days such as on New Year's eve, when more traffic than usual is expected after midnight.

The same applies to certain floodlighting systems of public buildings and churches. In these cases the floodlighting systems could be switched off altogether after midnight when few would be around to appreciate them.

Dimming of street lighting and switching off floodlighting systems after predetermined times has been in use in many European countries for quite some time. These countries take energy conservation very seriously and most of them are also world leaders as far as tapping of renewable energy sources are concerned.

In Malta, we still have a long way to go, but recently there have been some tangible indications from Government that we are on the way. The use of renewable energy sources is highly recommended but one has to bear in mind that saving energy is by far cheaper than generating energy through renewable sources.

Mr Vella is former head of electricity at Enemalta Corporation.