St Mark's Bridge, Edinburgh
St Mark’s Bridge is a road and pedestrian bridge which crosses the Water of Leith, the main river flowing through Edinburgh. The name ‘St Mark’s’ derives from a small chapel which once stood just to the north east of today’s bridge. VolkerLaser, who specialise in bridge refurbishment and repair, were appointed to carry out major structural repairs to the 1950’s prestressed concrete bridge over a 24 week period.
A compact roadside compound was set up beside the bridge. Temporary power was required during the 24 week contract in order to power the safety lighting to allow the repair work to be carried out during the dark, winter months. Power was also needed for the drying room so that VolkerLaser operatives would have dry clothes each morning.
However, this contract posed significant challenges as the site is located just 10 metres away from local residents. It was crucial that any generator noise did not disturb those who live close to the bridge. There was also very limited space, so it was challenging to fit the temporary power solution within the space constraints of the site.
Mather+Stuart Power Solutions devised a hybrid temporary power solution for VolkerLaser that was able to power the lighting and drying room, without interrupting local residents. A 40kVA generator was supplied, along with a 3 hybrid unit plus distribution and cabling. This was fully connected and set up by an experienced electrician.
Working alongside the traditional generator, the hybrid unit automatically detects when the load is low and turns off the diesel generator, seamlessly transferring load to its internal stored energy. When a higher load is detected, the power is switched back on and the excess power capacity recharges the battery bank, offering significant fuel, cost and emission savings. The 40kVA generator was able to provide power in the day and the hybrid unit provided silent power at night time, powering essential circuits only. The hybrid option limited the evening load to 4kw continuous power over a 10-12 hour period.
Despite local residents living just 10 metres away from the site, reliable and uninterrupted power was supplied during the renovation works and the hybrid power solution ensured silent night time running. This ensured that VolkerLaser could carry out the works with maximum efficiency, whilst making huge savings on fuel and CO2 emissions, in line with VolkerLaser's sustainability principles.
“We had total peace of mind that we could leave the site in the evening, safe in the knowledge that the generator and hybrid unit would self-stop and start. This ensured that we had safety lighting overnight and dry clothes for our operatives each morning. Furthermore, there were no complaints from local residents about noise due to the silent night time running of the hybrid power solution.”
Jason Herring, Supervisor, VolkerLaser