What credits? It would not cover the cost or needs of our operation let
alone allow for selling credits. Many of our products save energy yet we
get no credit for anything by doing that either. That brings up another
point. Starting later this year (EPA regulations) we must use our boilers
to oxidize what would otherwise be a VOC emission so we could not go 100%
solar even if it was practical.
That brings up another government mandated folly. We are installing
$400,000 in equipment to do this. The EPA says the payback is in 10 years
if we run a full capacity 365/24. Fact is, we only need this particular
equipment days 6 hours a day to support the rest of the plant. But they
still base their figures on 365 because we "could" run 8760 hours a year
even thought they'd never issue a permit to do so or we could ever need it.
That 6hr/day could align nicely with the 2nd/3rd shift when you'd have
to run the fossil fuel boilers anyway. You'd still be cutting some 33%
of both your fuel consumption and your emissions. Again, you are the
only one saying 100% solar, I have consistently said ~33% solar. What
would 33% of your annual oil/gas consumption amount to in $? Probably a
hefty chunk of change towards building the daytime solar boiler.
We spent about 200,000 last year so the savings potential is $66,000. That
is assuming you get 33%. I'd guess we'd be closer to 20% considering
weather in New England. Sure, that would be a good savings, but what is the
equipment cost? You seem to have missed that question. Where does it get
installed and what has to be done to the infrastructure for it? What is the
Seems to me, if it was that simple and cost effective power plants around
the world would be using it.
Now if I have room for molten salt tanks, this may work
I don't know the equipment cost offhand, but tracking down info on the
existing commercial solar stem electric plants in CA would provide a
wealth of information. Given the relative simplicity of motorized
mirrors reflecting the sun onto a collector tower, and lack of exotic
technologies, it may be less than you'd think.
As for location, it goes on your existing roof. Indeed if you have A/C
units up there to keep your plant comfortable, the shade provided by the
reflector array could significantly reduce the A/C cost as well. The
solar energy that is absorbed by all roofs is not only wasted, in most
cases it is a negative as well.
If we put appropriate solar energy collection devices on our existing
rooftops we can make significant gains in reducing demand for other
fuels and energy at the points of consumption, reducing demand on energy
that must be transported like electricity, gas or oil, as well as
without requiring more land to site collectors.
The other hurdle we need to get past is the all too common idea that if
you can't replace 100% of your energy needs with RE it isn't worth
pursuing at all.
This is a critical point and one that causes me endless frustration.
When discussing air source heat pumps, the common objection raised is
that they can't typically satisfy 100 per cent of the home's space
heating demands and for some folks anything less than 100 per cent is
completely unacceptable. What they fail to understand is that you
don't have to satisfy all demand for it to be **cost-effective**; it's
a matter of determining the optimum solution that provides the
greatest **net benefit**. So who cares if you require backup or
auxiliary heat on the three or four coldest days of the year if, at
the end of the day, it has saved you more money than any of the other
We're not all engineers and we don't all hold advanced degrees in
economics, but if more of us understood (and embraced) the concept of
net present value, it would no doubt help us to make better choices.
That may be so, but when you compare the economic performance of a
high-efficiency air source heat pump to that of its geo-based
brethren, the former prevails nine times out of ten and ten times out
of ten if you apply the difference in their respective cost towards
measures that further reduce the home's space conditioning and DHW
Admittedly, that's a pretty bold claim but I've run hundreds of
different scenarios using various heat loss factors, weather data,
utility charges, install costs, discount rates, etc. and in my
experience you have to push the assumptions to the far extremes before
you can reverse the results. That said, I'm more than willing to be
proven wrong if someone can provide me with hard data and I certainly
wouldn't object to sharing mine.
According to the IGSHPA, vertical closed loops are typically more
expensive than their horizontal equivalents, as quoted below.
"Horizontal installations are simpler, requiring lower-cost equipment.
However, they require longer lengths of pipe due to seasonal
variations in soil temperature and moisture content. Since a
horizontal heat exchanger is laid out in trenches, a larger area is
usually required than for a vertical system. Where land is limited,
vertical installations or a compact Slinky horizontal installation can
be ideal. If regional soil conditions include extensive hard rock, a
vertical installation may be the only available choice. Vertical
installations tend to be more expensive due to the increased cost of
drilling versus trenching, but since the heat exchanger is buried
deeper than with a horizontal system, vertical systems are usually
more efficient and can get by with less total pipe."
Are you referring to something other than what is described above and,
if so, can you point me to some online references?
FWIW, I was told by a HVAC contractor based in Moncton, New Brunswick
that a typical 3-ton GSHP installation (new construction) runs in the
range of $25,000.00 for horizontal closed loop and $30,000.00 for
vertical (CDN). Does that more or less jive with your figures?
Yes, something quite different than the two earlier techniques. I'm not
sure of references, but for the trenched vertical coil method you cut a
fairly narrow (~6" wide) trench something around 8' deep with a big
ditch witch and then take the plastic tubing coil and stretch it out
sideways so the coils of tube overlap at modest intervals and place the
coil in the trench. You then back fill and you're done. Far less labor
intensive then drilling holes or digging a big grid of trenches to put
single tube runs in. What they found was that the soil was such a good
thermal mass that you didn't need to cover nearly as much physical area.
This newer installation method takes perhaps 2 hrs to instal vs. all
day. Otherwise, it's the same tubing and same equipment, just a lot less
Thanks for the clarification. I hadn't heard of this technique before
so I appreciate you taking the time to describe it to me.
From what I understand, the cost of a ground source heat pump is
typically two to three times that of a conventional air source system
so if, for argument sake, we peg the cost of our standard system at
$7.5K the equivalent GSHP would be $15K or more. Obviously, the exact
cost of either system would depend upon a host of factors, but for now
I'm going to assume the premium runs in the range of $7,500.00.
As a quick, back-of-the-envelope exercise, an average new home with a
space heating demand of 15,000 kWh/year, if equipped with an
air-source heat pump (8.5 HSPF/Zone 4) would use roughly 6,000
kWh/year. That same home heated by a GSHP (seasonal COP of 3.75)
might come in closer to 4,000 kWh/year. The difference of 2,000 kWh
at $0.12 per kWh works out to be $240.00 a year; we might reasonably
assume DHW and air conditioning savings kick in another $360.00, in
which case our combined savings total $600.00/year -- on the other
hand, an air source heat pump with a desuperheater might claw that
back to less than $400.00. Nonetheless, if we assume an incremental
savings of $600.00, the simple payback here is 12.5 years, with
various cash discount rates and utility rate assumptions moving the
exact position one or more years in either direction. If the
breakeven point, as in this example, is more than ten years, it's fair
to say your money would be better spent elsewhere; for a lot of
consumers, even a five year breakeven point is a dicey proposition.
Again, these are rough numbers and we can fine-tune them further, but
I wanted you to understand my base assumptions.
Interesting. How do you figure that would work out in North Texas (north
of Dallas) where there is a lot of A/C load in 100 degree weather and a
surprising amount of heating demand in the winter as well? Another non
monetary factor to consider is the lack of an outdoor unit with a
somewhat noisy fan, and the need to clean it regularly of dirt, pollen,
leaves, etc. This is of particular interest since I expect to replace
the full HVAC here, probably next year. I also expect to be here quite a
few years longer.
I can explore this in more detail later on when time permits, if you
so wish, but right now it's getting late and I'll soon have to call it
Anyway, in terms of operating performance, SEER ratings are suppose to
be reasonably representative of what we can be expect to encounter
over the course of the entire cooling season. However, if it is
helpful, EER is based on steady-state operation at a 95F ambient
temperature (not far from the 100F mark you mention). To get a rough
sense of how these two numbers compare, you can convert SEER to EER by
multiplying the former by either 0.9 (relatively low humidity) or 0.8
(high humidity). So, if we assume you live in a hot and humid area,
an ultra high efficiency heat pump with a 21 SEER rating would have an
EER of 16.8 and a high efficiency model with an 18 SEER rating would
have an EER of 14.4. To then convert EER to COP -- a more useful
measure when comparing these products to GSHPs -- take this second
number and divide it by 3.4. Thus, our 21 SEER unit would have a COP
in the range of 4.9 (@ 95F) and the 18 SEER version would clock in at
about 4.2. Again, this is a rough approximation, but the results seem
to be more or less in line with what we could expect from a typical
Your concerns related to noise are hard for me to address. The CAC in
my Toronto home is a two-stage high efficiency model and on the low
setting the outside compressor is surprisingly quiet (a light and not
unobjectionable hum). I don't ever recall it kicking on high so I
can't honestly tell you how loud it is when operating at full
capacity. I don't believe I had any issues with dirt, leaves or
pollen -- I may have washed down the outer cabinet with soap and water
once or twice but that's basically it.
A GSHP may very well prove your best choice given your particular
needs, utility costs, operating environment and so on -- I really
can't say. But I wouldn't automatically rule out a high-efficiency
air source heat pump without investigating this option further; these
products have really come a long way in recent years. Whatever you
ultimately decide, good luck!
You could modify the technique a bit for your area, by digging a 6' wide
trench to the ledge, laying the coil in horizontal and then back filling
and covering with another foot or two of dirt. Slight grade change, but
still no drilling or blasting.
You've again provided nice sounding fluff with no figures. Are we talking
$50,000 or $5,000,000 or $50,000,000? We certainly don't have the recources
that a utility company has. Just a WAG that cost would put it out of the
reach of most of us. This is not quite "off the shelf" equipment or
technology so the engineering alone can be tens of thousands of dollars.
No AC in the plant. The cost would put us out of business.
Payback. Unless the investment can show savings quickly, most buyers have
no interest. Many people move every few years and they are not interested
in 10 year paybacks. I'm surprised that more had not been done with solar
over the past 20+ years since the last oil shortage got things rolling.
There is also dumb zoning. A fellow in our town was told he had to take
down his wind turbine because it was too high.
Dumb zoning, I like that. That could describe so much more than
As for being surprised that more hasn't been done with solar over the
past 20 years, I'm new to the solar scene but I'm amazed at what has
been accomplished in just the past 10. And I'm thinking that the next
10 years are going to be amazing.
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