You're thinking of the wrong technology. You don't use solar PV or solar hot water thermal, you use a concentrating steam boiler setup, like used at a few CA commercial solar utility generating stations. An array of tracking reflectors concentrating the energy on a single central collector-boiler. For your application there are no transmission and conversion losses since you directly generate the steam you need above the plant that is using it. You do not bother trying to store any of the energy for night use, you simply ramp the oil / gas fired boilers back up for the evening. 30% energy savings using existing roof space. Think tax credits too...
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 heat potential?
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 alternatives.
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 requirements.
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.
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 this thread.
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
Are you comparing the labor intensive old style deep hole or large trench array, or the newer much better and much less labor intensive trenched vertical coil installation?
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."
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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 installation labor.
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.
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