On 30/04/2019 11:34, Tim Lamb wrote:
In message , John
Rumm writes
On 30/04/2019 08:15, wrote:

How realistic are the manufacturers claims for energy produced by
their solar pv panels. If they claim 2kw howlikel is this to be
true/realistic ?

Its likely to be a true reflection of the maximum power delivery of
the panel when in full midday sun in the summer.

In peak summer you might get a load factor as hight as 20% in the uk.
In the winter it will be down in low single digits. Averaged across
the year its usually estimated to around the range of 10% - 12%. Also
peak delivery never aligns with peak demand.

Hmm.. My grazing tenant is considering solar PV panels for an unattended
cattle watering set up.
12V bilge pumps seem readily available and adequate for the head and
flow required. Lead acid battery not a problem but...
how much panel do you need for Hertfordshire sunshine May to October?

It might be OK over that period with something like a 300W PV panel to
guard against several cloudy days in succession. The main worry will be
people nicking it - even the batteries grow legs sometimes

Hot weather conveniently requires more water which, last summer, was
around 600litres/day at a head of around 5m.

My mathmatical capabilities do not stretch to this sort of problem:-)

mgh = 600kg x 10ms^-2 x 5m = 3000kJ needed each day

Roughly 8h daylight and 3600s in an hour = 29000s so in theory a 100W
panel would just be able to keep up if it was sunny every day but allow
at least twice that and you will need a charge controller too.

Every time I have tried to do solar powered irrigation (but on a
slightly smaller scale) lugging a heavy SLA battery out to the field and
taking the old one away to recharge has won hands down. Solar panels
are a bit cheaper now but I doubt if it is truly worthwhile. OTOH if he
has a solar panel just lying around it would extend the period between
having to manhandle to battery and recharge it at home.

I only needed a 3m head of water and 100L delivered daily.

--
Regards,
Martin Brown