You need to first understand the Schlemburger method of earthing,as this is the way that you test earth resistance.With this method,a minimum of 2 earth spikes must be used.Secondly,single point earthing is a must on most residential TNC electrical connections.Thirdly,you must bond all the panels and then ground to the earth spike with 16mmsq earthing cable.Drpending on your lightning zone,you might be required to have an air termination rod and/or Type 1 lightning protection.