According to Stokvis Energy
Systems, solar thermal water heating
systems are highly efficient because
evacuated tube solar collectors are
designed to maximise the solar energy
absorbed while minimising heat loss
through radiation.

However, solar systems require
some form of storage and, says
Stokvis, this is not necessarily the
most efficient way to deliver hot water
when the primary heat source is from
a boiler.

One answer is a hybrid water
heating system using solar thermal
technology combined with a low
water content plate heat exchanger to
provide hot water instantaneously,
‘topping up’ water temperature without
the need for storage, other than
that required for the Solar input.