Generation Switch


Many people who have solar panels fitted to their houses wish to make the best use of all the energy generated.  This is especially so if there is no export meter and the exported energy is ‘deemed’ to be 50% of the generated energy. 


Designs and Projects

Most generation meters have a flashing LED which flashes 1000 times for each kWh generated.  By sensing the flashes and checking the flash rate it is possible to use this information to switch on electrical loads to use up any excess power.

The first circuit is a simple circuit in which a control can be preset to any desired generation rate and a switch is turned on whenever the preset rate is exceeded.

Circuit Diagram

Circuit Description

Bill of materials

Strip-board Layout



The second circuit follows on from the first.  Whilst a reasonable guess can be made at a normal base-load for the house (say 500W) and the simple circuit can be used to switch on a 3kW immersion heater whenever the generation exceeds 3.5kW, the circuit has no knowledge of temporary loads – such as a kettle – which would cause some generated energy to be diverted to the temporary load and the immersion would be running on imported power.  This second circuit incorporates a reset input which turns off the switch whenever imported power is detected.

Circuit Description


I hope to be experimenting with a remote control switch system which can turn on the load at a point remote from the Generation Switch circuit.  This would allow the Generation Switch circuit to be shut away – perhaps next to the import and export meters – and the load, such as an immersion, remotely controlled by an RF link.  I have looked at developing this system but in the limited time available so far have not found a suitable remote controlled power switch – one in which the remote control is operated by a simple single contact switch.

The next stage of the design takes a step back and looks at producing a generation switch from an entirely different angle.  Why are we checking how much is being generated by the panels, when really we need to look at how much spare power is being exported?  We should be able to measure the exported power and turn on loads to reduce this to a minimum.  This is a longer term project with some results during August 2012.