On Apr 5, 11:42*am, Chris J Dixon wrote:
NT wrote:
On Apr 5, 10:02*am, "harryagain" wrote:
A while back,someone brought up the problem of switching stuff on
automatically only when the PV panel can meet the load. *ie as weather
conditions allow.

Answer is here, someone is making one.http://www.solarpowerportal.co.uk/ne..._embraces_ener...

So you can set this up and go out to work. When the PV output meets the set
level it will switch on (and off).
Prevents inadvertent use of non PVpower.

Its a strangely complex product for a very simple job.

Here is a much simpler solution, but look at the cost. You would
take quite a while to recover £190 plus Part P installation. The
calculation would also have to allow for the arrival of smart
meters.

http://chrisrudge.co.uk/immersion.htm

Both seem to have too simple an algorithm. They only look at
generation, not consumption.

The best arrangement should measure generation and consumption,
and only turn on specified equipment if there is sufficient
unused capacity.

Easily expressed, but not so easy to achieve in a manner that is
both compliant and cost-effective.

Chris


In the case of offgrid solar pv, the solution is rather simple:
monitor battery bank V and turn on a relay when V is high enough. High
enough means power to spare from the panels.

With grid tied pv, as you say it means monitoring production and
consumption, but its not too demanding a bit of circuit design.

But more to the point, why would one do it with a grid tied system,
when you're better off exporting electricity then using it when the
sun's gone down.


NT