Lee, you're always so spot on but this time I'm going to disagree - a
little. Efficiency of PV does matter. You have to buy the units, so
the more efficient they are the less space they will take to generate
the same amount of watts. Most people don't have unlimited space, so
space does make a difference.
It could also make a difference in purchase cost. Fewer panels mean
less mounting hardware and less electrical work. Also fewer units could
mean less overall cost for the PV units, themselves.
Peri
------ Original Message ------
From: "Lee Hart via EV" <ev@lists.evdl.org>
To: "Electric Vehicle Discussion List" <ev@lists.evdl.org>
Sent: 13-Jan-15 9:03:42 AM
Subject: Re: [EVDL] EV Demand Response - (solar-thermal-NOT)
Robert Bruninga via EV wrote:
Solar Thermal makes no sense anymore. Compare 70% efficiency (ONLY 5
months of the year) for a net of 29% to:
PV that is 18% year round AND when used to drive a Heatpump with a COP
of
2.5 gives a net "efficiency" of producing "45%" HEAT.
Or look at it this way. Every single day that your house is not using
100%
of every BTU available, you are losing solar energy that could be
generating electricity at full market rates!
I think the word you want is "return on investment"; not "efficiency".
Efficiency measures how much energy you get out divided by how much
energy YOU put in. When you're getting the energy for free (the sun),
it doesn't really matter what your conversion efficiency is. The energy
you didn't collect isn't costing you anything, and it isn't "lost" --
it's doing what it always does and is heating the environment.
Solar thermal makes sense if you want heat. It's really GOOD at making
heat!
Solar PV makes sense if you want electricity. It's not all that
efficient (10-15%); but that's still better than using some other
method (wind, thermal) that then needs a second conversion process to
give you electricity.
-- Ingenuity gets you through times of no money better than money
will get you through times of no ingenuity. -- Terry Pratchett
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, leeah...@earthlink.net
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