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Solar Thermal is Dead (82 Posts)
Solar Thermal is DeadInteresting Solar Thermal vs, Solar PV argument. Thoughts?
try itSound like a lot of theory. Years ago I built a PV water heater. My thinking was to avoid batteries and inverters. The hot water is the energy storage. I rigged up an open compressor and drove it with a DC motor directly from the PV cells.
The real issue in America is how important it is NOT to save less than a dollar a day.
Martin Holladay admits...... his title is intentionally provocative. He's a smart and caring guy who does far more than just theorize. Still, the argument is made with assumptions. He assumes heat pumps are now all grown up. The info I've seen both in terms of measured performance and field experience suggests something more like a youngster who isn't all that coordinated.
He assumes conventional solar design which ignores the newer "simple solar" ideas out there which have few, if any moving parts and little to corrode or even maintain. Steve Baer summed it up nicely years ago when a black painted trash can was "raced" against a fancy solar system and won. There is room in the marketplace for solar that is designed to catch the low grade heat. The ideas exist. With elegant design, we can do much better.
Mark Twain put it best: "The reports of my death are greatly exaggerated."
The author forgot to mention a few things...Like the fact that PV cells degrade over time, possibly as much as 10% per year... And that in some locales, you are not allowed to sell back more energy than you've historically used over a long period of time.
An attention getter for sure, but if the base ASHP unit is located within the dwelling, then the energy it is using is NOT free. Someone paid for it...
As for me, I've not seen ANY appreciable degradation of performance from the ST systems I've been watching over the years.
And, when talking base efficiencies, PV is what, 12 to 15% efficient on a GOOD day, and ST is 60 to 80 % efficient? I just don't see how they can make the claim that PV and ASHP's make more sense.
TIME, will tell...
Heres a link to the article on degradation.
MEIt's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.This post was edited by an admin on March 26, 2012 10:49 PM.
if you have net meteringthen PV could easily beat thermal, unless you happen to have a huge summer thermal load. PV can slurp up more and more easy summer watts, and you use them up in the winter.
that's not an end of the road winner for the grid in the end (unless summer peak load continues to be the driver at least, as PV hits that peak perfectly), but it's an economic reality for the short to medium term at least.NRT.Rob
Overpriced Solar Thermal is Dying for SureI think we have to concede the argument that spending $10k to displace $50/month in gas for DHW is not a great investment.
I've posted this before, but I'm trying to generate more interest in simple SHW. We haven't seen much buy-in from domestic water heater manufacturers in pursuing low cost goals, so maybe we are the guys to brainstorm and test. Here's a system that has no pump and no failure modes: http://www.youtube.com/watch?v=Q5rKLsJl3cY
And although I don't think homemade equipment belong in a viable business plan, there is much to be learned from Gary Reysa, the retired Boeing engineer.
http://www.builditsolar.com/Experimental/PEXColDHW/Overview.htmSuperinsulated Passive solar house, Buderus in floor backup heat by Mark Eatherton, 3KW grid-tied PV system, various solar thermal experiments
Solar hot water is not done based on simple economics....Never has been, never will be. It is done because it is the RIGHT thing to do for the environment, and the future occupants of Mother Earth..
With gas prices continuing to go down, the economics might never make sense in our lifetime.
When compared against other alternatives (LP, oil, electricity) the numbers do look better, but still won't pay for the installation costs within the theoretical lifetime of the system.
Speaking of theoretical life times of system, I remember an ASHRAE number of around 25 years, and many systems that were installed back in the 70's are STILL cranking out good btu's. Maybe THOSE numbers need to be reviewed and adjusted. In any case, people rarely use an economic analysis to make their decision as to wether or not to do solar thermal.
Food for thought.
MEIt's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
40 year life is possible
There are two domestic hot water solar systems on my street. They were both installed in the late 70's. They are glycol systems. One system is not working, said to be a pump issue(.?)
The other system functions perfectly. 34 years on.
No doubt in my mind, the later system has paid for itself, long ago, even with inflation adjustments.
compellingWith silicon as cheap as it is this idea does apear to make some economic sense, wires are clearly easier to run than pipes etc. etc. For starters I'm skeptical about the pricing given for both systems (too low) I think BOS (ballence of system) costs are being overlooked. Are we also factoring incentives?
Regardless of the actual local costs (the disclaimer was appreciated) there was a very important omision that Rob also points to.
Gallons of hot water produced and Kw generated can be easiliy interchanged mathematically but they are very different in terms of how they are actualy utilized.
A PV array in a given local can be expected to produce a certain amount of electricity just as a thermal system will produce a certain number of "gallons". Seems fair to say but really it's missing something. Though we might wish to do so, we can not consider the grid as a no loss battery. Net metering has not changed the fundamental problem of energy storage as it relates to solar energy. The thermal example is solar energy converted to useful work, the PV example assumes no loss in the process of becoming "used". It's missleading to count every electron a PV system generates as useful work. Did the local grid need or use all the power that was "returned" to it . Sure the grid can integrate some renewables but not too much, the intermittent nature of sunlight (clouds and night) is one of the realities that some of the jazzed up PV folks seem to be ignoring in the quest for an "electric utopia" http://taxshine.com/Utopia.html
I'm not saying the idea presented here is bunk, I kind of like it, but if we took the net metering out of it and looked at PV vs. Thermal gallons to gallons I think the economics would fall apart.This post was edited by an admin on April 13, 2012 12:34 AM.
I agreethat net metering in its current form will have to change for larger scale adoption of solar.
however if you use heat pumps tied to PV even on straight efficiency you're getting close on cost per delivered watt. plus that opens up solar to doing cooling loads, so you have more potential load to offset, especially in the summer where the need for "Heat" is really not that great once DHW is taken care of.
I think thermal solar will be relegated to those with relatively high domestic loads only in the not too distant future here.NRT.Rob
PV vs Solar ThermalWhy debate it?? We need combo PV-T panels and we need them now. Cooling off a PV panel produces about 10% more electricity, this alone seems like a good reason to have a combination panel, but here in northern Massachusetts our heating and hot water bills account for about 70% of our energy dollar compared to 30% for electricity. We HAVE to use these panels along with radiant heating to harvest hot water at about 80 degrees; making the panels MUCH more efficient, and if we can cover a large portion of the heating load, the payback will be much quicker.
Thanks, Bob Gagnon
Combo PV-Termal panelsMany of us have been waiting decades for these. The Germans are close http://www.szna-usa.com/pvtherm.html
This Looks Like The AnswerTo much greater solar efficiency, I read in Solar Today about four years ago that they were starting to use PV-T panels in England, are they available in the US yet, SWEI? Thanks for posting this.
Thanks, Bob Gagnon
PV-ThermIs available in the US - click on the 'Contact' link -- and give Reinhard my regards.
Remember that from a thermal perspective, this is basically an unglazed flat plate collector. Still plenty of uses, but not much good for space heat other than in a few very mild climates. If you have a use (or a dump load) for low temperature heat in the summer, the PV output can significantly exceed that of a standard system.
the new array on my roofwill save me $2500 of power a year. 10% more is only another $250/year, and to get it, you're adding a speciality trade, and a mechanical system with some longevity and service issues that PV just doesn't have. And I've got a very large system (60 panels) so whatever is required to connect all those panels together on the roof is not an insignificant labor adder, I assume.
Of course you get the hot water too, and that's great, as long as you have something to do with it. Unfortunately you still get it during the day and mostly in the summer. so it's still not a space heat solver for most people, still just DHW in most cases.
the real question is what's the cost difference between PV and PVT? I suspect for what it will be for most people...a modest power generation boost and some thermal offset to a DHW load... it probably won't be worth it.
But if there is a good "snap together" kind of install assembly for this maybe it won't be so bad.NRT.Rob
The Achilles Heel of PVTNo one has figured out how to make a glazed PVT collector yet.
So until then we're better off just putting in two separate systems with collectors that do their assigned job well. As opposed to collectors trying to do two jobs poorly and expensively.
http://www.quora.com/Are-there-solar-panels-that-integrate-photovoltaic-and-thermal-systemsSuperinsulated Passive solar house, Buderus in floor backup heat by Mark Eatherton, 3KW grid-tied PV system, various solar thermal experiments
(mostly) agreedWith PV module prices where they currently are, PVT really is a tough sell. There are a few cases with limited collector space where it can make sense, especially if night sky cooling is involved.
you need a loadfor the thermal side of PVT. PV arrays can be fairly large so you need some place to use that thermal collection. i don't think it would make sense to cool the PV with thermal then run a dump to get rid of un-use-able thermal energy?
dump loadsCan make sense in some situations. If the PV output goes up 20% (they claim as much as 30%) in the hot months, the effect on net metering or REC revenue could be quite significant, especially with TOU metering.
Stagnation Temps may damage the PVI've never heard of anyone trying a glazed PVT collector yet.
Once the PV supplier hears about 350F stagnation temps, they say no thanks.
I'm guessing that it's usually because most PV cells have little narrow conductors that would fail under that kind of thermal stress. Not to mention their efficiency drops off badly all summer because they would be much hotter than an unglazed PVT panel.Superinsulated Passive solar house, Buderus in floor backup heat by Mark Eatherton, 3KW grid-tied PV system, various solar thermal experiments
Heat LoadIt seems that having all that extra heat to play around with would be a good thing?? Why not install PV-T on a building with a heated swimming pool, or a large domestic load like a school or skating rink, certainly finding a place that uses a lot of hot water year round shouldn't be that hard.
If we design these hot water system correctly, like a well designed hydronic system, the maintenance should be very minimal, maintenance that would have to be performed anyway, whether your heating with a boiler or the sun.
Most people say we can't get enough hot water from thermal collectors in the winter, are using them for domestic hot water only, once we lower our collection temps. to about 80 degrees for radiant heating, we greatly increase the amount of hot water we can harvest from the sun, just because most people who are doing solar thermal, use it for domestic hot water only, doesn't mean its the right way.
A 20% increase in electrical production for Rob would come out to $14,400. over 30 years, that seems like a small price to pay to hook a bunch of panels together, and installing a couple of tanks and a small radiant system. How much hot water for heating would one expect to collect over that same 30 year period, my guess is a lot.
When comparing fuel costs to solar collection remember that when we compare the cost of other fuels we don't include all the cost associated with that fuel. How much are we going to have to spend removing all the mercury from the water that comes from burning coal and carbon based fuels, how much do we spend guarding out nuclear power plants from terrorist, and how much are we going to spend transporting all the nuclear waste, and guarding it for the next 1,000 years, solar and wind look cheap when you take all that into consideration. Solar thermal is not dead, it is alive and well at my house, and it can get a lot better.
Thanks, Bob Gagnon
Hot RodI'm not sure you would need to dump if you have a big storage tank, I don't have to. Remember you have much greater heat losses through the tank and piping at higher temps. I have 120 evac tubes and a large box collector, tilted at about 65 degrees toward the low winter sun, so collection is automatically limited in the summer when the sun is directly overhead. I put a large coil in the tank to dump but its just been sitting there for the last decade.
Thanks, Bob Gagnon
Here is some food for thought. How about using a PVT panelto run a compressor. The compressor uses the water from the PVT panel as a medium for heating. Then the thermal energy would be stored at a high temp for extraction during the night.
ST works in winter?Up here in New York, average temperature during the day drops below 40F from December to March, does it mean Solar Thermal will be completely useless during those months to produce DHW?
According to this video: http://www.youtube.com/watch?v=aB8disMi3A8
With outside temperature of 30F, ST produced 17,413 BUT in one day, given the current rate of LP at $2/gal and 91,333BTU/gal (95% efficient gas boiler), that's equivalent to about 40 cents worth of heat in a day!This post was edited by an admin on May 5, 2013 9:11 PM.
Upstate New YorkI don't see shy it wouldn't work where you are, here in Massachusetts on the New Hampshire border we get temps down to below zero and Solar Thermal works great here. I get 100% of my domestic hot water and about 30% - 40% of my heating from my solar hot water panels.
Thanks, Bob Gagnon
ST for heatingMost ST systems are for producing DHW, what system did you use to produce heating as well?
My Solar HouseMost systems produce DHW, that's why they don't collect much energy in the winter, they're waiting around for water temps in the collector at about 130 degrees, but I harvest energy at about 75 degrees, and simply collect much more energy at the lower temps. I use the low temp solar energy for radiant heating. My collectors are tilted to the low winter sun, which also prevents snow from building up, and I have a HUGE storage tank with really big heat exchangers to make hay when the sun is shining. Trying to collect 130 degree water in the winter here is difficult, but collecting lots of 75 degree energy is a piece of cake.
Thanks, Bob Gagnon LEED AP
this is still ignoringthe fact that right now I am gobbling now massive amounts of solar energy that just isn't present in the winter.... way more than 10 or 20% more, more like double over the course of a day.... and banking it for later.
And I will use every single KWH I generate, no matter when I generate it. No "use it or lose it loss".
and I will double its effectiveness by using that KWH in a heat pump.
Solar thermal cannot compete for space heating. It can't even play the game for space cooling. That's just a fact.NRT.Rob
Collector tiltNRT_Rob, what is you collector tilt? If it is tilted at 45 degrees or less its great for domestic, but not so good for space heating, and you also probably have snow sticking on your panels too, I don't have that with a steep tilt. A collector tilted about 65 degrees will collect the maximum amount of energy in the winter, and less in the summer.
not that it really mattersI don't know why you're asking that bob. I"m PV. I don't have to worry about whether I'm pitched for winter or summer... I'm pitched for yearly ideal, about 23 degrees true south.
What I'm saying is right now, at this very moment, and over the whole last month, I am absolutely cranking out solar power. I have no heating or cooling demands during this period. if I were thermal, GOBS AND GOBS of power would be utterly wasted. But my panels generate it and send it back to the grid where I can make use of my credits later, when I do have heating demands. I won't bother saying "heating and cooling" because when I have cooling I also have solar so that is offset in real time.
I don't lose anything from my tank. I have no tank to get hot and stop my collection. I don't have to have a load in real time to use my power. I can double my collection power by using heat pump technology. I can cool with my solar energy.
PV wins. Thermal is dead.
I know how much my array cost and how much it collects. Do you know how much your system would cost for someone to install, and how much energy benefit you're getting? we could settle this with math, if so.NRT.Rob
Far from Deadjust needs to be applied properly. Unless the heat demand is year-round, ROI will suffer. PV has the advantage there for sure.
It doesn't cost much moreTo add a few more collectors and some radiant wall panels, to an existing solar domestic hot water system. Whats it going to cost you to put in more PV and install and maintain a heat pump? A zero energy home builder here tried that and it didn't work, it used too much electricity even though the roof was covered in PV panels. He ended up using wood to heat his house. The reason we have to heat our houses with solar is that in Massachusetts heating is 52% of our energy dollar, domestic hot water is 17%, together its more than double your electric bill. I get a lot of heating from my solar, all of my heating load in the spring and fall, and a good amount in the winter. Monday night is supposed to be 39 degrees out, we are still heating here. How much are you going to spend on heating and hot water in the next 40 years? How much is your oil or propane bill going to be 10 or 20 years from now, I'll still be collecting solar energy and heating 100% of my domestic hot water, and a good portion of my space heating. Solar is alive and well, but it's for people who can think outside the box, and are willing to go against the flow.
Tilt does matter with PV. If your collectors were tilted towards the low winter sun, you would collect more energy then, and less, then you are now collecting in the summer.
Thanks, Bob GagnonThis post was edited by an admin on May 10, 2013 12:58 PM.
but with PVI don't care WHEN I collect it. We have net metering. I just want best yearly collection. And we are, in fact, net zero... in fact I generate more electricity than I can use (darn it!).
I am going to spend zero dollars on oil or propane or electricity. For the next 30 years. That's why I can nail down how much energy I'm using... I measure my energy usage and all my usage is electric.
The entire point I'm making is that solar thermal only looks better in the instantaneous collection efficiency numbers. In terms of yearly energy you can put into use, I think almost any residential analysis will come down solidly in favor of PV these days. Because the efficiency difference cannot erase the massive amount of time most of us spend with less load than you have collection ability, and net metering solves that issue completely.
the real question most people care about though is cost for useful energy gained. $3.50/watt installed and each watt will generate about 1.3 KWH/year here in the northeast. Add a heat pump and double some, potentially very large, percentage of those watts to apply to heating and/or allow for cooling offset. In my case it's probably about 70% of my total usage is "doubled" in this way.
So what's a regular solar thermal array sized to do more than DHW cost these days, installed, before credits?
How many useful yearly BTUs would you expect to get from it?NRT.Rob
Why not both?Why does it have to be one or the other. We will soon have combination panels that harvest electricity an lots of 75 degree water, and super-insulated houses will stay warm for days, we will use our houses for storage. There are simple solutions to all the problems we now have with solar hot water. The cost of solar panels are getting less expensive too, as people buy more of them, you paid $3;50 watt a few years ago maybe? It's down to about $2.00 a watt now and the DOE expects it to be about a dollar a watt by 2020, solar thermal and pv will be more competitive with conventional fuels, as prices drop.
Thanks, Bob GagnonThis post was edited by an admin on May 10, 2013 8:52 PM.
it's "one"because one makes a lot more sense than the other. solar thermal has poorer economics for space heat. Unless you can do it damn near free.
if you can get solar PV in for $2/watt PRE TAX CREDIT, then the discussion is completely over (though here in maine it's not that cheap). taking up roof space for hot water panels past the DHW demand is then seriously a waste of time and money and at $2/watt I'm not even sure solar thermal for DHW makes much sense when you can do an electric water heater tied to PV. at $3.50/watt PV was already compelling for space heat. Heck, at $2/watt, and 0.15/kwh electricity, you're below a ten year payback on PV with no credits at all. If that's after credit then it's pretty much the same as my cost last year.
Seriously... name an installed price and a yearly expected BTU delivery for a solar thermal system. anything you want to run through polysun or any of the solar calculators out there. we can compare this very easily. I just can't do solar thermal collection calcs myself at this time.NRT.Rob
RobIt's easy to make excuses, to not do something, whats hard to do is spend your own money to see what really works. You mention tank losses as a big problem with solar. First you have similar losses with an electric water tank, but secondly the solar storage tank should be within the buildings thermal envelope to minimize those losses and those losses will contribute to the heating load for about 6 months out of the year where I live, so for six months I'm not really losing anything. Since I don't run my boiler at all, this works out great for me as it keeps my basement from freezing. Its not to complicated to add extra insulation to a tank to cut losses during the summer months, I have 8" of foam on my tank to do that. It cost a few bucks for the foam, but it will last indefinitely, lengthening the amount of cloudy days my tank will stay hot. You say we have to use solar thermal right away but that's what we have storage tanks for.
Thanks, Bob Gagnon
I have no ideawhat you are talking about with your "excuses" comment, but I'll assume you aren't trying to insult me, since I did, in fact, spend my own money to see what works. I'm net zero, remember?
If you have a storage tank that can allow you to shift your solar collection above and beyond your DHW needs from April through october into your heating season, then great. I'd love to see the specs on that tank.
Until then, I have about five or six months of solid, high output solar collection that you don't get to utilize like I do, because I went PV. If you want to wave your hands about collection efficiency, I'll simply point this out... http://solarelectricityhandbook.com/solar-irradiance.html
go ahead and see what you've got, month by month.
I just ran this for Augusta Maine. I have heating demands from November into April. But let's be nice: I'll let you use every KWH available from October through May (I have a very tight shop, most homes need more heat than i do) and just assume you don't lose any at all, you use it all. In Augusta, that's an average of 2.54 KWH/m2/day or about 210 KWH/m2 for the seven months. you're about 60% efficient and so that's 126 KWH/m2. You don't get to use any solar in any other month for space heat, only domestic, which we can agree is a tiny load compared to space heat, right?
I'm PV. Let's say I'm 10% efficient. so I only get 21 KWH for the same seven months you do... but, I can drive a heat pump which doubles it to 42 KWH/m2 applied to my heating. However, the OTHER five months a year give me about 723KW/m2 gross... ten percent and doubled gives me another 144KW/m2.
So I can run 186KW/m2 for heating with solar. with solar thermal you can only do your 126. I'm 50% higher by area, and that's still give YOU may in this comparison.... realistically we're being nice. Plus I can apply it to cooling, DHW and power and not just DHW or space heat, if my loads are too low.
this is by area though, the real question is cost. So, how much area does your system cover with panel, and how much would it cost retail before credits? We can do this with math Bob. it works.NRT.Rob
RobWhen people "Go by the book" they keep making the same mistakes that people have made in the past. We can greatly increase the amount of energy we harvest from the sun, for space heating, by making a few small changes, like a steep collector tilt, low temperature collection, and using two, large storage tanks with really big heat exchangers. I'm very happy with the way my system has been working, and expect it to payoff in 20 years or less, depending on fossil fuel price increases. My small storage tank is 200 gallons, and the big tank is 1500 gallons, the coils are made out of 5 coils of 1/2" X 60' soft copper. Thats the only specs I have on the tanks. I agree that if someone installs a conventional solar hot water system, by the book, they will not be happy. we have to change things and with these small changes I get 100% of my domestic hot water and about 40% of my heating load, I'm very happy with my system.
Thanks, Bob Gagnon LEED AP
that's greatthat you're happy with it. but you're an industry professional getting a 20 year payback. retail that's what, 30 years? non starter. No one in their right mind pursues a 30 year payback... there are endless other things you could do with that money with better economics and with better energy savings to consider.
PV is about a ten year payback in the northeast these days just on the federal credit, 15 without... and that's still a stretch for most people. My heat pump is a ten year payback or five if it saves me a boiler, with no credits at all... unless you're in a natural gas situation, of course, since it's so cheap these days.
So you just proved it makes no sense whatsoever to pursue solar thermal for space heat. I know your system is older and PV was more expensive when you did it. but things have changed. Why would you ever do thermal for space heat now, when PV is so much more effective at offsetting your energy use?
I socked away almost 4 million BTUs last month to use later when I need it. My heat pump will double that to 8 million+.NRT.Rob
This is one subforum...where I usually just lurk (yeah, I know, not like me). But I would like to second Bob's thoughts and comments. Specifically, my late father-in-law made a fairly decent living doing engineering for solar heated houses in southern and middle New England, and it turns out that they work remarkably well. As Bob noted, harvesting 75 degree F heat is not that hard to do; even getting up to 100 or so isn't that bad -- and at that point, with a decent amount of storage, a well-built house can make it through all but the worst winter conditions at normal interior temperatures (his most difficult problems were not the dead of winter, but, say February/March getting enough solar, and September/October, dumping heat).
He wasn't too enthusiastic about DHW solar, and I don't blame him -- there you are working with much higher temperatures, and you have storage and insulation and re-radiation issues.
And he didn't do anything with PV -- it wasn't available when he was active.
Anyone interested in his work and thoughts, I'll be happy to correspond with...Jamie
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
Active solar thermalof mostly modern design has been with us since at least 1939 http://mit.edu/solardecathlon/solar1.html
The true cost of energy has been carefully hidden from Americans for a long time. If our defense budget only covered defense...
Thanks, JamieYou are one of the few who can understand, and agree with me, regarding solar space heating. I am not a fan of solar DHW either, the pay off is way too long, but if you combine domestic in the summer with space heating in the winter, then I think we're onto something. My Dad was a Milkman but he too understood that we have to heat our homes with solar hot water, and not just our domestic, back in the early 70". But he knew nothing about low temperature efficiencies and Radiant Heating, if he were alive today he would be very excited about the possibilities of using this missing piece of the puzzle. I would be happy to see some of what your Father did, and his conclusions, could you post them here so everyone can see?
SWEI, you're right about the true cost of conventional fuels, I wonder what it cost to have our Military guard the waste from nuclear power plants for a thousand years, or to have fighter jets circling the plants for weeks after 9-11, I recently read that our govt pays the cost of insuring nuclear power plants, add that to the threat of release of radiation, nuclear seems pretty expensive. The same could be said for fossil fuels, how much wold oil and gas really cost if our govt didn't give the oil companies billions in subsidies, and what is going to be the cost of removing all the Mercury from the lakes, rivers and oceans?
Thanks, Bob GagnonThis post was edited by an admin on May 10, 2013 12:10 PM.
See what I can do...I've never posted a picture in all the years I've been on here! Have to figure out how...Jamie
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
how do you heat with 75° water ?how do you heat with 75° water ?
I suspect that if PV was any good businesses would be doing it. Industrial buildings are covered with huge empty roofs.
JumperI use radiant heat in my walls, floors and ceilings to heat my house and I use solar as supplemental heat. So any energy over room temperature helps heat my house. If I come home during a cold sunny winter day, my house might be 60 or 65 degrees instead of 50 degrees or so, it''s a lot more comfortable and warmer through out the house. I have a house I built during the 80's and it's leaky with 2X4 construction, if I had a super-insulated house 75 degrees would supply most of my heat, even on the coldest, sunny days.
Thanks, Bob Gagnon
here's an ideaCollect warm water with solar thermal; then use PV to drive heat pump to boost temperature of that solar heated warm water. When thermal collectors are working so are the PV.
NRT's arguments depend on somebody else subsidizing PV. In addition to installation subsidies, the electric company uses resources to accept his electricity when he wants and then provide him with electricity also when he wants it. Those resources are paid for by other customers. Clearly not sustainable.
you're stilllimited by the btu collection of the thermal in that case... all it does is improve the heat pump COP for a portion of its usage related to that number of BTUs. remember heat pumps do not create BTUs, they only move them. so your heat pump in that case isn't helping much.
without any subsidy right now PV has about a 15 year payback by itself here in maine. the net metering is an issue if it went large scale, but there are many, many ways to work with that. also:
1. PV collection is strong during peak electrical usage periods (summer cooling period, even here in maine). if/when the peak shifts to heating periods (winter nights) that may change but for now blunting the peak demand with solar production is a big win for the grid that greatly offsets any additional cost for handling net metering administration.
2. Thermal energy can easily be stored in tanks. there are ETS systems out there as well but I think tanks will be the big winner. right now I run a heat pump time shifted by using my lower level slab as a heat battery to maximize COP but could do it to maximize electrical economy just as easily to take advantage of any time of use metering solution anyone wants to dream up, and those schemes are in the works because the utilities know this is all coming. Smart meters exist right now in every home in Maine even though those TOU plans are still in their infancy here, they are ready to go.
Like it or not the grid is going to have to deal with intermittancy. What is clearly unsustainable is a long term focus on unsustainable energy sources, not the economics of renewable energy long term.NRT.Rob
Thermal energy storagehas been available for decades and it works. With all the fuss over next generation batteries, I'm somewhat surprised it isn't getting any press. We should see a healthy retrofit market as TOU metering becomes more widespread.
RobHave you taken into consideration the maintenance and replacement costs for the heat pump? When I Goggle it, most sites tell me the life of a heat pump is about 15 years, are you going to have a major repair bill just as your system is paid off? When I Goggle "Solar Space Heating Combo Systems" Wikipedia tells me that many countries in Europe have these combo systems in place to heat domestic hot water, and for space heating and cooling. In many countries 50% of the solar hot water systems are also combo heating/cooling systems, and in Germany, perhaps the world leader in Solar 25% of it's solar hot water systems provide space heating as well. It just makes sense to me that a simple hot water system added to a pv collector would have a much longer life with extremely little maintenance. Every article I read about solar hot water not being worth it, they are talking about solar domestic hot water only, including the article this thread is referring to. We keep doing things the same way as everyone before us, and everyone is afraid to think outside the box. Maybe solar thermal is dead in the town you live in, but here in Lowell, Massachusetts, it's alive and well, and now that I know there are thousands and thousands of these combo systems in Europe, I think I'm in pretty good company.
Thanks, Bob Gagnon LEED AP
sureI have seen a large number of solar thermal systems that didn't make it 15 years so I wouldn't get too snug in your assumptions there. but you misunderstand what I was saying with paybacks. the payback on PV itself is 15 years... it has a lifespan of 25+. That's pretty great.
the HEAT PUMP itself typically has a payback much faster than that (5 to 10 years), but it depends on what you compare it to... if we compare to natural gas in a heat only application, not so great. Compare to electric resistance doing heating and cooling, it's great. so pick your comparison. But if you want to compare it to the solar thermal system of a size you'd have to put in to offset the same amount of energy it does, then the heat pump doesn't need to talk about payback, it's cheaper up front and it will probably a similar level of service as the solar thermal system... i.e., not much. You need to save about 30 million BTUs/year to hang with the heat pump on that basis if you want to pencil out what that system looks like for my shop which is a heat load similar to many single family residences. I suspect you'll find that only the very smallest heat loads would shift that economic analysis.
I don't know what you're reading, but optimal economics for solar has to be for year round loads... that's DHW. Maybe if our energy was three times the cost it is now, like it is in europe, we'd see more space heat systems like that here too, especially in the past when PV was much more expensive than it is now so it would be the only solar option that really made sense. you get maximum production per square foot of panel you buy and per gallon of storage you buy (and thus, optimal return on investment) when you use everything you collect. You cannot do that by buying a lot of extra panel that is utterly useless for half the year.
HERE in america you will never pencil out a payback that makes any sense whatsoever for a solar thermal space heat system unless your labor or components are free, your subsidies are huge, or energy gets a lot more expensive than it is now. Plain, simple, fact. I will happily eat those words when you show me a payback less than 15 years on any solar thermal combo space heat/DHW system without subsidy, but you'll have to pardon me if I don't hold my breath while I wait, because quite simply I've looked at the numbers and I'm pretty sure that beast doesn't exist in the US and isn't going to anytime soon. If it does, it's certainly not the system in your house, which is awesome and great and cool and not going to save america very much energy because a 30 year payback is, one more time, a dead horse in this race. My hat is off to you for being willing to do it, of course. but I don't have many clients who would buy it. and I have a lot of green clients.
If you can do cooling, that would help a lot, but solar cooling is in two flavors, one is solar absorption chilling which is complicated and fantastically expensive here in the US, and one is night sky radiation which is limited in capacity, but might help. no evacuated tubes there, and I would love to see the performance of such systems in greater detail. Maybe that's your in, I don't know.
but right now, at today's pricing, PV is ready for prime time and dead simple to deploy. we hit the tipping point of grid parity a couple years ago and we're beating it now. significantly. moving into heating and cooling is as simple as deploying a heat pump and upsizing the array and pow, there you are.NRT.Rob
Two Things Wrong Here RobFirst, I said I figured my system has about a 20 year payback, so you rounded that up to 30. I don't know where you got that 30 year figure from.
The second thing I see is where you say Solar Thermal won't make any sense unless we see energy costs get a lot more expensive than it is now. Now I've been wrong before, but I'd bet my Evacuated Tubes against your PV Panels that in 20 years when my system is paid off, energy costs will be a lot higher. A good hot water solar panel should last a lot more than 15 years, I've seen only a few systems around, but a couple of my customers have systems over 30 years, and there is no reason to doubt that a good system should last many, many decades, just like a forced hot water system, they are very much the same. Domestic does have a year round load and that's great, but as you point out fossil fuels would have to be three times as expensive to make solar worthwhile. I have a domestic AND space heating together, not one or the other. It's interesting too that for our energy dollar here in Massachusetts, 17% is spent on domestic hot water and 52% is spent on heating, that's about three times as much. Wouldn't harvesting 3X the solar energy have the same effect on payback as having energy prices 3X higher?
yesyou said YOU have a 20 year payback. Are you going to sell that system to your customers at cost? No one but you, or another professional can install your system at your price. right? All my numbers so far have been installed retail. even IF your number is retail and not your cost every thing I've said still holds true, it's just less dramatically true.
Your analysis on chasing more energy is also not correct. Your price to collect 3x the solar is not 3x the cost. it's significantly more than 3x because you are trying to collect during time periods where the solar just ISN'T THERE. So your payback gets longer and longer because the cost to collect more of your load goes up and up faster than your collection does... because you are wasting more and more of the capability of every panel you add after your baseline DHW load is met at optimal summer tilt.
I agree that solar thermal SHOULD last a long time. Many do. but a lot of systems definitely don't... maine has a lot of abandoned solar systems that the local plumbers couldn't keep in service or didn't save enough to make it worthwhile. it's got moving parts and thermal stressed and maintenance requirements that PV doesn't have at all.
In 20 years energy probably will be more expensive. and I bet your solar thermal system against my PV that PV will be even cheaper then, solar thermal won't be as much cheaper, heat pumps will be significantly cheaper, and that there might even be something new in that time we have no knowledge of. But we're not talking about the system we'd put in, in 20 years. we're talking about today.
TODAY, if you want to do solar space heating, you should be looking at PV and a heat pump. That's all I'm trying to get through here. Solar thermal stops making sense after a DHW load is met... that's the only thing it can do more cost effectively than PV. Unless the very intriguing idea of solar cooling comes into play in a way I don't expect to see happen (but, like you, I've been wrong before.)NRT.Rob
solar coolingI have read this post for months now, listening to the bantering back and forth. All valid points.
Solar thermal will only become a mainstay, only if it's functionality is increased. If the function of solar cooling can be added to solar thermal, then the sky is the limit.
There are already many systems of these types throughout the world: http://solarthermalworld.org/solar_cooling?module=browse
I've been to the Oxford Garden install. Very well done.
If solar cooling component can be added to thermal on a grand scale, problem solved. Now the economics change.
It has a way to go, but it is going. Maybe some of you can make it more streamlined and user friendly.
solar energy storageWell with solar cooling much of the load occurs when sun shines, so that helps. You still want energy storage, and thermal is way cheaper and more durable than electric. You could use solar thermal to provide cooling for heat rejection part of PV powered refrigeration. But don't you think that such complicated schemes make more sense for large installations ? If energy becomes expensive enough solar will prevail. I suspect that a new generation of nuclear will render solar unpractical except for locations off the grid.
No Nukes!The waste by product of nuclear makes burning coal look green.
Thanks, Bob Gagnon
NO NUKES...new or old.
Cancer rates are high enough.
Yes I do agree solar cooling is only viable for large installs, but down the road with advancement in technology it may be come more applicable for residential also.
I'll believe in Nukeswhen they're insurable without government guarantees.
I remain hopeful.This post was edited by an admin on June 5, 2013 1:07 AM.
MORE NUKES!Radiation is natural. I'm vastly more concerned with the combustion byproducts associated with other forms of power generation and the soup of chemicals from a variety of other industries that make life modern. Granted, the current generation of technology is pathetic and wasteful, but there are superior concepts that have the potential to deliver truly clean energy.
Not in my backyardOr yours.
plutonium 238 and 239 are spent fuels from producing nuclear energy. When plutonium 238 breaks down over 90 years becomes uranium 238, it's half life of radiation will last 250 million year or so, Natural Uranium by it's self is very low in radiation.
Plutonium on the other hand is very radioactive, but during the fission process with uranium becomes highly dangerous and hazardous to all living creatures.
This from IAEA:
The radioactivity of all nuclear waste diminishes with time. All radioisotopes contained in the waste have a half-life—the time it takes for any radionuclide to lose half of its radioactivity—and eventually all radioactive waste decays into non-radioactive elements (i.e., stable isotopes). Certain radioactive elements (such as plutonium-239) in “spent” fuel will remain hazardous to humans and other creatures for hundreds or thousands of years. Other radioisotopes remain radioactive for millions of years (though most of these products have so little activity as a result of their long half-lives that their radiation is lost in the background level). Thus, these wastes must be shielded for centuries and isolated from the living environment for millennia. Since radioactive decay follows the half-life rule, the rate of decay is inversely proportional to the duration of decay. In other words, the radiation from a long-lived isotope like iodine-129 will be much less intense than that of a short-lived isotope like iodine-131. The two tables show some of the major radioisotopes, their half-lives, and their radiation yield as a proportion of the yield of fission of uranium-235.
The energy and the type of the ionizing radiation emitted by a radioactive substance are also important factors in determining its threat to humans. The chemical properties of the radioactive element will determine how mobile the substance is and how likely it is to spread into the environment and contaminate humans. This is further complicated by the fact that many radioisotopes do not decay immediately to a stable state but rather to radioactive decay products within a decay chain before ultimately reaching a stable state.
Not in my backyard, which is this whole planet. Cancer rates have exponentially grown since the first nuclear tests and directly coincide with the advancement of nuclear anything.
I would gladly livein the backyard of nuclear power plant.
"Cancer rates have
exponentially grown since the first nuclear tests and directly coincide
with the advancement of nuclear anything."
First of all,
What are you basing this on?
Enjoy your backyard thenhttp://www.americanscientist.org/issues/feature/2006/1/fallout-from-nuclear-weapons-tests-and-cancer-risks/1
It depends on the source of course. The corporations provide major funding for most studies through IAEA and Universities.
Did you read the articles you linked to?From http://www.americanscientist.org/issues/feature/2006/1/fallout-from-nuclear-weapons-tests-and-cancer-risks/1
"Cancer investigators who specialize in radiation effects have, over
the intervening decades, looked for another signature of nuclear
testing—an increase in cancer rates. And although it is
difficult to detect such a signal amid the large number of cancers
arising from "natural" or "unknown" causes, we
and others have found both direct and indirect evidence that
radioactive debris dispersed in the atmosphere from testing has
adversely affected public health."
----The issue is not whether radiation can cause cancer. Is it acceptable to release unnecessary radiation into the environment? Of course not. Nuclear weapons are bad, but does this mean nuclear power is bad?
---This article is actually on the nuclear power industry and it's relationship to cancer. The authors' conclusion was negative though; there wasn't sufficient evidence to support a link. Keep in mind that radiation is very easy to detect. No one has to stay up at night worrying about the unknown. If reactors were spewing it out we'd know about it right away.
This is a newspaper article discussing claims made by Dr. Sternglass. Wikipedia indicates his statistical research and conclusions are hyperbolic and generally not accepted.
there are 3 major issues with nuclear1- pollution from source extraction of uranium. not the hugest problem, but it's an issue.
2- safety. SWEI nailed this... when they can afford to privately insure, maybe it will make sense. with highly qualified and regulated insurers, of course.
3- storage. when we don't have a waste storage issue anymore, great. until then, even the best waste results I'm aware of stretch into timeframes longer than our country has even been a country. Seems unlikely we can ensure the safe storage of such waste. Maybe when we have a safe way to hurl it into the sun or something...
Hey, the sun. that's nuclear. it's in your backyard! Maybe we should stick with that ;)NRT.Rob
Safer nuclear powerwith no fuel shortage could have been widely available by now if had we actually wanted it back in the '50s and '60s http://en.wikipedia.org/wiki/Thorium-based_nuclear_power
woulda coulda shouldabut didn't.
"But even were its commercial viability established, given 2010's soaring greenhouse gas levels, thorium is one magic bullet that is years off target. Those who support renewables say they will have come so far in cost and efficiency terms by the time the technology is perfected and upscaled that thorium reactors will already be uneconomic. Indeed, if renewables had a fraction of nuclear's current subsidies they could already be light years ahead."NRT.Rob
If renewables had a fraction of nuclear's current subsidiesof course, but the 50+ year lead time is an even bigger challenge. Amazing progress has been and continues to be made on many fronts.
Base load is a tough nut to crack, though...
also the uranium enrichmentis often done at plants fueled by coal. The Paducah, Ky. enrichment plant recently closed, powered by one of the dirtiest coal power plants. One of the last US owned and operated plants.
Seems the movement is to multi-national ownership of enrichment plants now. One of the newest plant in the US is "essentially a French plant on US territory" according to World Nuclear Association
Now the taxpayer funded cleanup begins for the decommissioned Paducah plant site.
realisticallyNukes produced energy for 3 cents per therm fifty years ago. Were it not for bureaucrats having a good time, price would have gone down like other high tech products. Renewables, coal or gas can't approach 3 cents per therm.
Proliferation and waste problems are more bs from fools who don't understand atomic energy.
realisticallyThe short term dangers of high pressure live steam are staggering regardless of the energy source. 960 PSI is scary stuff, but some designs rely on even higher system pressures.
The real challenge with nuclear is time. Half lives of tens of thousands of years lie outside of our ability to comprehend, much less manage.
incorrectunless you ignore insurance, cleanup, and storage of waste.
as of now it is impossible to insure a nuclear reactor at any price. hard to think it'll be "3 cents" or whatever after all that is taken care of.
what's the cost for containment for thousands of years? oh right, we have no idea, because there is no such thing as reliable containment for thousands of years.NRT.Rob
Giant Corporations Lie!To make money, that's all they care about. They told us how cheap our electric bills would be with Nuclear, but ask the people in southern New Hampshire who have some of the highest rates in the country, they lied to get it approved, and they still make a profit anyway, and we pay the price. And like Net Rob says thats not even counting the insurance costs, security costs, or the cost of disposal. Nuclear is the MOST expensive energy we produce, but the Nuclear industry won't tell you that, they just want to make profits. There's a reason another plant hasn't been built in 35 years. The Nuclear industry told us there would be on average one major accident in a thousand years, well we've had three in what, the last 30 years. Nuclear is the dirtiest energy, and the most expensive, stop drinking the Nuclear Kool-Aid!
Thanks. Bob Gagnon
Tools That Don't Understand Nuclear WasteJumper is it total BS the the Nuclear Plant in Japan leaked 300 tons of highly radioactive cooling water a couple of days ago?? We don't have to fully understand Atomic Power to understand the risks, keep drinking the Nuclear Kool Aid.
Thanks, Some Plumber
is it total BS the the Nuclear Plant in Japan leaked 300 tons of highly radioactive cooling water a couple of days ago??Not only 300 tons of nuclear waste a few days ago, but probably 300 tonnes every day since the accident started.
Clean nuclear power: too cheap to meter. If so, why has the Price Anderson Act not been repealed?
specific numbersInstead of railing against corporations or plumbers' valuable evaluations of atomic energy; why not post some specific numbers. And please spare us the we don't discuss prices excuse. I saw some figures on a new apartment building in Venice,California. Solar thermal on roof projected to deliver 5000 therms each year with a budget of $250,000.00.
Fifty year payback in a sunny state with high gas prices. In US solar thermal looks pretty moribund.
while I agreeright now in america you cannot cost justify anything against natural gas. what is the value of that comparison?NRT.Rob
Jumpers RightWe don't need a bunch of stupid Plumbers voicing their opinion about Nuclear Energy or Giant Corporations, who do these Plumbers think they are anyway?? I also disagree Jumper, with trusting numbers instead of people. There was at presenter at SolarFest this year, Chris Wetherby from the Consortium for Advanced Residential Buildings, they built two similar homes, side by side, to see how solar thermal stacks up against mini splits and found out that the solar thermal beat the mini splits by using less energy, under actual heating conditions. Someone can easily make the numbers look however they want, I trust people who have actually done it and I value their feedback, but I am "Only a Plumber".
Thanks, Bob Gagnon Plumbing and Heating LEED AP
JumperThe problem is most solutions in this country (and world) come down to cost effect, not the correct healthy approach. No, solar thermal cannot compete with NG when it comes to dollars, not even close.
Nuclear almost never pays for itself: http://www.ucsusa.org/assets/images/np/np-cost-overruns.jpg. Then you have the costs that are not introduced into any ledger, such as the on going struggles in Japan.
When our culture values money over health, health of ourselves, loved ones and people unknown, we are in turn killing each other and ourselves. Money is a necessary cog in our society, but it can't be the dominating factor in our decision making about the future of our planet. It does not add up.
yes building owners like gas cosThe larger the monthly gas bill the happier they are. That's why they're not installing solar water heaters. Otherwise they'd love to pay GBC for a LEED badge. BTW, Bob, most plumbers avoid solar thermal because they have colleagues who have been hurt by its impracticality.
Maybe not...Here is a huge Solar thermal project....
Dead???Wow, 15 million investment,with an expected 5 year payback, and panels that may last 30 years or more, solar thermal isn't dead, it's just not real easy to do, so everyone makes excuses to not do it.
Thanks, Bob Gagnon
suspiciousI suspect that Duke financed this with ratepayer money to help meet renewable mandates.
Bob is correct that solar water heating is difficult anytime freezing is possible.
The video is also suspicious in that panels were ground level. Was that elevated tank for storage?