Our planning application for a 5.8 KW wind turbine to be mounted on a 12 metre mast was approved. We laid the cables and constructed the foundation. The rectifier and inverters were connected. The turbine was erected on Tuesday 13th January 2009 and commissioned on 15th.
The ground works took four days. On day 1 two holes were dug. The first was about 1 cubic metre for an anchor point for the turfer needed to raise
the tower. The main hole was 2.7 metres square and just over 1 metre deep: this now contains 9 cubic metres of concrete.
The holes were dug with this beautiful JCB. We still have over 10 cubic metres of spoil to get rid of.
On day 2 metal cages were placed in each hole and levelled, then 35 Newton concrete was poured. The cage had to be re-levelled when half the concrete had been poured. When all the concreted had been poured we checked again! We don’t want a “Leaning Tower at Wanstrow”.
If you like sums, 35 Newton concrete is strong enough to withstand a force of 35 Newtons on 1 square millimetre. The mast weighs about 1200 Kg, that is a force of 12000 Newtons. The turbine weighs another 150 Kg (1500 Newtons).
With the first 40 metres of trench dug on day 1, we are now pouring the concrete foundation. You can see twenty studs to which the tower will be bolted. The final trench will be 150 metres to the barn. The cable is rated for 17 amps wild AC at about 400 volts. There is a 25 metre copper tape in the bottom of the trench to act as an earth.
The cables are bedded in sand about 75 cms deep with a yellow warning tape on top of the sand. The studs were greased to prevent them becoming clogged with cement. The photograph above right shows the completed foundation with 20 studs, the earthing strip and the three phase cable enclosed in a plastic conduit.
By the end of the fourth day the ground works were complete and the turbine, mast and electrical controller were delivered. It needed the JCB and our David Brown to haul the bottom section of the mast up to the site. The bottom section is 8 metres long and weighs 800 Kg.