Pv for s/h/w..... [RE-wrenches]

[Jeff Yago]

Although there are few technical reasons why solar pv could not be the
primary supplier of domestic hot water via DC heating elements,  having
designed and installed hundreds of solar thermal hot water systems
throughout the early 70's (up to 10,000 esq.. arrays on military bases and
some hospitals) I find it very hard to believe the economics will ever be
equal.

You start with the same energy input density per sq. ft. for both.
Therefore, the only differences is the efficiency losses and the cost
differences.  Solar thermal converts solar directly into heat of the fluid
to be heated.  Solar pv first converts to electricity, then to heat in
element, then element heats water,  each energy conversion has an efficiency
loss.

As for costs, I find it hard to believe a low tech copper pipe pressed into
an aluminum fin covered by a sheet of glass or fiberglass will ever cost
more than the complex technology required to manufacturer a solar pv module.

Of course, if the battery bank is charged and there are no other electrical
loads, the hot water tank makes a good place to "dump" the un-used energy.
However, without the inverter, batteries, and charge controllers, what can
you do with the solar pv direct to hot water element once the hot water tank
is hot?

As for me, I see no reason why both solar processes cannot work side by side
on the same home, with each doing what it is best designed to do in the most
cost effective way.

Jeff Yago
Dunimis Technology Inc.

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