Solar thermal is not expensive if it is installed when the house is
built (or included when remodeled). I have heard from people in the
field that adding it to building code would not only save a lot of
energy but also save cost for home owners once the rather trivial
investment was paid off.
Another alternative - similar to EV until recently - is to do it
yourself.
I bought a second hand system ("hot top" boiler with heat exchange
coil,
a drain-back solar panel and a super simple control board for the pump)
for about $400 and installed it myself - removed some of the roof tiles
to accommodate the 6x6ft panel, drilled holes through floor and roof to
connect pipes, even added a small drain-back container since the pipes
were running in a way that otherwise would prevent drain-back. As soon
as the sun started shining in the morning, the pump would come on and
start warming the water.
Oh, BTW, this was a "Luigjes" system in The Netherlands. The control
system consisted essentially of 2 comparators: one compared the temp in
the boiler with the temp in the panel. If the panel was warmer by a few
degrees, the pump was started. The other comparator was protection: if
the boiler temp reached max setting, the pump was stopped (and the
water
drained back).
Winter times (with freezing nights in The Netherlands) were no problem,
since there was never water in the outdoor system that could freeze.
The electronics was so simple and low-density that anybody with a
soldering iron could understands and fix it.
This system was running the tap water through the collector (which had
copper piping) as the additional heat exchanger coil was used to allow
another source of hot water (the furnace) to be used to provide
additional heating if needed, for this purpose it measured the temp in
the top of the boiler and added heat to keep the top at high temp -
hence the name Hot Top.
Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: cwa...@proxim.com Private: http://www.cvandewater.info
Skype: cor_van_de_water Tel: +1 408 383 7626
-----Original Message-----
From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Michael Ross
via EV
Sent: Sunday, January 11, 2015 4:08 PM
To: Peri Hartman; Electric Vehicle Discussion List
Subject: Re: [EVDL] EV Demand Response - (now Home solar)
A few years now, my business at NC State has been to test solar thermal
collectors for certification. We also offer installation training and
other CE classes for the industry: wind, PV, etc.
To summarize, I don't there is much future for residential solar
thermal.
It is easy and efficient to collect heat from the sun in water, most
collectors are 70% efficient, not much better, not much worse (except
if
they are total crap). The temperature of the fluid is not much use for
anything but offsetting costs of water or space heating by other means.
Simple as the collector is, the solar thermal system is far more
complicated than a PV system: you have an electrical and control
systems,
plumbing, holes in the roof, maybe a heat exchanger (for a glycol
circuit)
instead of regular hot tank for wash water, or you have a drainback
system
that empties the collector when it it is not sunny.
There is enough complication that the cost of installation is high, and
many households simply don't need enough hot water to get any payback.
Consider my home with just two people gone half the day; $20 to
insulate
the hot water tank is a much better value than $4k or $5k to get a
collector and system installed.
As PV gets more efficient and cost drops, it will be come much simpler
and
more cost effective to run the electric element in the hot tank.
Residential solar thermal is dying. Eventually, PV my be comparable to
the
various solar space heating options.
There is one nice simple solar thermal idea that gets oddly little
attention and that is solar air heating collectors. We worked with a
fellow in Florida who has a nice well thought out air collector's
system.
The front glass is a standard double pane picture window. All the
materials were chosen for ready availability and cost - typical
construction materials mostly. The system couldn't be simpler - it has
a
simple bimetallic thermostat that turns the fan on above 90F and off
below.
On Sun, Jan 11, 2015 at 3:43 PM, Peri Hartman via EV
<ev@lists.evdl.org>
wrote:
I think a combo of PV panels and solar collectors would generally be
the
best solution, assuming you have the sun exposure. Currently PVs are
not
very efficient. I don't have any numbers of solar collectors but I'm
pretty sure they can beat PVs several times over.
Since home heating doesn't require electricity, that could be done
more
effectively with collectors. The EV and home appliances could be
powered
by PVs, to the extent possible.
How much reduction in fossil fuel use would depend on how your power
is
generated and how you currently heat. In my case, home heating comes
from
natural gas (don't have any A/C) and almost all the electricity comes
from
hydro. Thus, the best way for me to reduce my carbon use (and reduce
fracking) is to switch my home heating to a solar collector system.
If
your case is, say, electricity from 50% coal and 50% nuke, where as
your
heating is natural gas and cooling is electricity, then you may be
better
of prioritizing the electricity generation before the heating.
Either way, the amount of area required to capture kWh-equivalents is
going to be smaller for heating than for generating electricity until
we
have better PV technology. So, don't overlook installing collectors.
Peri
------ Original Message ------
From: "Peter Eckhoff via EV" <ev@lists.evdl.org>
To: "Ben Goren" <b...@trumpetpower.com>; "Electric Vehicle Discussion
List" <ev@lists.evdl.org>
Sent: 11-Jan-15 10:21:19 AM
Subject: Re: [EVDL] EV Demand Response - (now Home solar)
When I took a Solar Energy course way back when, my instructor said
there
was a "rule of thumb" for solar thermal heating. He said to take the
square
footage of the heated **area** and divide by 3 to produce a storage
**volume** estimate. At the time, fist sized rocks were used to
store
the
heat. Of course insulation, angle of the collectors to due south,
etc.
mattered. The idea was to pump a liquid through the collectors to
the
storage volume and then have a separate (or 3-way valve) to direct
any heat
from the storage volume to pipes radiating heat under the
subflooring.
Recently, I ran a parameterized commercial solar energy program with
a
similar system and the system came back saying I needed a 600 gallon
tank
for optimum heating. In this case, a liquid is being used to store
the heat
instead of rocks or sand.
While not perfect, the idea is that PV will take care of local EV
driving
needs and the solar thermal will address a lot of winter heating
needs. The
more cloud cover and colder winter temperatures, the less energy it
will
provide.
On 1/10/2015 3:09 PM, Ben Goren via EV wrote:
On Jan 10, 2015, at 9:21 AM, tomw via EV <ev@lists.evdl.org> wrote:
His book, Solar Hot
Water Heating, describes (among other systems) using solar hot
water
collectors to heat a 2 ft thick layer of sand which is insulated
inside
the
house foundation with a concrete slab floor on top of it, giving
over
one
hundred of metric tons of thermal mass for radiant floor heating.
Water
is
circulated through the sand with PEX tubing, starting around mid
August
to
heat it up for the winter.
Similarly, the most effective method of cooling for locations such
as
Arizona where I am also uses the Earth as an heat sink...and, of
course,
also similarly only really make sense for new construction. But,
yes
--
done right, and you can live in arctic frigidity in the middle of
August
for pennies per day. If whoever built the building had the
foresight
to do
things right....
But the good news is that there's insane amounts of energy
available
from the Sun such that simply covering a suitable fraction (and
generally a
minority) of your roof space with generic PV panels results in a
net
surplus. And, if the grid is available to use as the equivalent of
a
battery, you can make an handsome profit that way if you've got
available
capital to invest. Most can still make a profit, though nowhere
near
so
handsome and with much more capital, going off the grid entirely.
b&
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--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *
Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."
To invent, you need a good imagination and a pile of junk.
Thomas A. Edison
<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>
A public-opinion poll is no substitute for thought.
*Warren Buffet*
Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google
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