Solar Thermal – Large Water Storge
The following link has an interesting solar thermal system using a large water storage system. I am located in the far north where we experience extreme cold and little sun light during the dead of winter. This system will not provide the necessary heating requirements for my location. Our heating season runs from September to June and we have excellent solar conditions during the shoulder seasons. I am interested in knowing if this system could be modified to work to reduce the need for a traditional boiler system during the shoulder seasons. Could this system be modified to be coupled with a boiler where when the solar system cannot provide the necessary heat the boiler heats the water storage tank. The boiler would operate at full capacity (peak performance) to heat the water before shutting down. Can this be done and is there any advantages to it.
The solar thermal system starts on page 40 of the presentation on this link.
http://www.riverdalenetzero.ca/PRESENTATIONS/Riverdale_NetZero_energy_home_–_presentation.pdf
Replies
I found the presentation in the link fairly lame to be frank. Anyone who refers to components like "top-up water heater" ... give me a break - what the H is that? For solar to work, you need sun. Period. You can't enhance something that you really don't have. Sure you can make small incremental increases in efficiency, but in the grand scheme of things for a given heat load, you will need a certain size collector area. There are no real 'short cuts' to getting there. Fancy technology costs money to boost efficiency ... maybe a few percent.
Remember, there is no real shortcut to gathering solar energy. Solar thermal ranges from 50-70% efficient. Houses in the far north will get those cold sunny winter days ... but cold means a high heat load.
You are talking about an active solar system, here. They have inherent inefficiencies that you can tweak a little here and there, but they ultimately have their limitations. Better off w/ passive solar. If your house doesn't do that, then your active system may be your only choice. There is a time and place for everything, only you can decide if it is right for yourself. Generally, though you can't get something like this for little effort/expense. There is no magical answers. Laws of thermo rule.
Mark,
Yes, you can install many collectors and a very large tank to reduce your fuel use in the shoulder seasons. The only problem is that the system will not be cost-effective. I wrote an article for Energy Design Update on the Riverdale net-zero house you cited, and have interviewed the designers and builders. Even they admit that their solar thermal system ended up being much more complicated than they originally hoped — and that the system was not cost-effective. If they had never built the solar thermal system, the house would have been cheaper to build and they could have heated the house by other means for less money.
Maybe I should back off and lend a softer perspective. My response was late at night and I was 'motivated'. No offense intended.
Large thermal storage tanks can really only work to store large quantities of energy. Large quantities of solar heat are available IF you have lots of solar insolation (i.e. clear, sunny skies) AND lots of collector area. This gives you lots of extra energy to store. Without that, you have a large storage tank and a little energy ... that translates to luke warm water in the tank ... which does you no good in your hot water coil in the air handling unit.
You can tweak and play w/ various components of the system. You could even run that storage through e.g. a heat pump, but you still have the laws of thermo to deal with and some serious limitations.
A lot of what I say depends on where you are located ...
Yes, you can couple it with a boiler ... I'm doing that on systems right now. When the storage temp drops, the boiler boosts the temp back to the usable value you need. This reduces the energy consumption of the boiler.
But like the other guy said ... lots of expense ... questionable return. Everything has a place, though, even active solar space heating. But generally you'd be hard pressed and there may be lots of other alternatives available to you that would serve you much better.
Where are you? What situation do you have? New const? Existing? Orientation of the building/windows?
Mark.... i designed and built a DOE demonstration project in 1976
it was a 28x40 Cape with 2x6 stud walls
the solar tank was a 10,000 gallon concrete storage tank in the basement
the collectors were 4x14 copper absorbers with double Kalwall covers (14 x 36 overall )
the heat was extracted by a water to air heat pump
worked fine...
the heat pump was very expensive to maintain so the owners took it out of the loop and installed a boiler and hot water baseboard... not conected to the solar
they continued to run the collectors which turned it into a big radiator in the basement
and it still had a heat exchanger in the tank to preheat their DHW
eventually a leak developed in the collector system and they turned it off
last year the wind ripped the top off one of the collectors so they had the roof reshingled and scrapped the collectors
lesson learned ( to me )
insulation is the best return for the money
don't use high tech... you can't pay the service calls
active solar HOT WATER systems are very expensive to install & maintain
solar collectors will otlast their covers ... unless you use GLASS... stay away from Kalwall
we have installed about 20 Active Solar Heating systems.... our house has a 10 x 36 array of Hot Air collectors... we had ONE collection day in the past two weeks
last nite it got to 2 deg outside........ insulation is better
Good points/example.
Your example contradicted your lessons learned. The covers outlasted the collector (the leak occurred first, you said).
no.... the leak was probably in the attic manifold system
Kalwall sucks as a cover systemi'd go single glazed low-iron glass or go hometwo years ago we replace a Kalwall cover system for another customer... 14 x 40.... $15,000 labor and matls.... covers only... his absorbers were same as the 1976 houseMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Mike,Have you ever built an Acorn Structures (Acton MA) house.They used to offer a solar system.They were bought by Deck House in the late 80s,,,,And I just read in the Globe last week that Deck House has closed their doors.Harry
Harry.... no.. we've remodeled a couple of Acorn and a couple of Deck Houses
also... didn't they have some history with New England Components ?i looked up Acorn and here's what I found on the first go-round....<<<<About Empyrean
Empyrean International enjoys a long and distinguished history of building quality homes for discerning families. Acorn Structures, founded in 1947 and Deck House, founded in 1959 merged in 1995, and in 2003 became Deck House LLC. The company began exporting homes internationally in 1990. The firm was renamed Empyrean International in 2005, the same year that the dwell homes
by Empyrean brand was developed.
In sixty years we have built more than 20,000 homes including 400 homes internationally – a trusted legacy of experience and quality. >>>>I always found them to be drafty , with bad glazing details... deck homes i really disliked... their claim to fame was that they were especially good for taking advantage of views... so they had their primary living spaces on the second floor ( the Deck )which means that everything in the house has to go up one flight of stairsthey were usually underinsulated and hard to heat... they did seem to shade their glazing so it was not subject to overheating in the summer
Edited 1/18/2009 7:51 am ET by MikeSmith
Harry... here's that news you described....
another one bites the dust
<<<<Prefab Home Builder In Receivership
Posted Jan 7th 2009 6:02PM by Deidre Woollard
Filed under: Real Estate DevelopmentsPrefab home builder Empyrean International, the builder of Deck Houses, Acorn Homes, and Dwell homes is the latest victim of the credit crunch.
The Massachusetts-based company closed in late October and two weeks ago, a court-ordered receiver took control of the company. The owner of Empyrean, Patrick Gilrane, blames the failure of Lehman Brothers as well as the weakening economy for the closure. He had hoped to restructure and reopen the company next year but the home builder has defaulted on a $7 million loan and has not paid its utility bills or taxes for months. The Boston Globe reports that the receiver, attorney Stewart Grossman plans to put the company up for sale once he puts its affairs in order. The company's roots go back to 1947 with the founding of Acorn Structures. Deck Houses and Acorn homes have crated entire neighborhoods. Over the last few years Empyrean has worked with Dwell magazine to create boxy modernist homes. Dwell plans to continue working on prefab homes with a different builder.Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Mike,My grandfather worked at Acorn for like 25 years.My dad worked there for like 35 years ( he retired in about 91 when they sold to Deck House). Naturally, I worked there on and off from the time I was able to push a broom.The founder, John Bemis, was a really nice fellow. You want to talk about glazing problems???? When I was a kid I would go in on Saturdays and package and prepare to ship replacement sash for customers with failed window seals.My understanding was that the then defunct window manufacturer- Wabash- had built the sash in a building that was " dripping with grease" from use by a previous tenant.Anyway, they did offer a roof top solar system. I built quite a few of them there for a few years. Eventually I was working for a builder in the area and had a chance to install one.I didn't get the "this thing is bulletproof" feeling.Apologies to the OP for the highjack.Thanks Mike,Harry
so.... was there a connection between them and New England Components ?
one of my friends , Fank DiMauro, was a designer for them ... i recollect they had a lot of similar glazing details
one thing i recollect is that some of the structural members were rabbetted so they would become part of the glazingMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Mike,I don't recall any connection w New England Components.I never saw (say from mid 70s on) any rabbited framing members to accept glass. Doesn't mean it never happened. They tried a lot of things through the years.One thing we did there that I feel contributed to their "glazing problems", was that we installed the windows in the plant (into the wall panels), then stacked the panels flat, and shipped them.Lot of stress on the glass.I built some very large fixed glass gable windows when I was there. It used to scare me to lay them down. You could see the glass flexing.I'm going to call my father later,,,, I'll run the NEC connection by him.Thanks, Harry
I too have been noodling about what to do with solar hot water in the summer. Most would suggest vertical collectors to prevent summer overheating. It seems like there must be a way to bank it and use it in the winter.
I have read about sending it into the ground if you have a ground source heat pump. Claims were made that it stayed "local" and helped the system in the winter. Hmmm.
If you got a GSHP, you won't need solar H20 collectors. Or more appropriately, you won't want them.
Then what would you do to bank energy from summer solar hot water?
Banking is unnecessary as the heat removed from the living space during the A/C cycle can be directed into a holding tank via the "desuperheater" procedure. There is more then enuff heat captured during that process to provide whatever hot water you need. The excess is then dumped back into the earth.
In the winter, there still seems to be an salvagable amount of heat the desuperheater can remove form the effluent to assist the storage tank. But that's gonna vary based upon sizing.
Save your roof space for PV.
I don't have a GSHP. I don't have AC either, don't need it. I need heat in the winter only. I do have some radiant slab but the roof is shaded in the winter by evergreen trees and the hill they grow on.
Electric overage rates here are up to $.23/ KWH so you're right, PV would work great in the summer when I don't need the power.
Then 30 Grand for an temporary heat sink is not what you need.
Maybe it's my imagination but I seem to recall reading something about a slab home in the soutwest that was built on a 4 ft. deep area of sand that acted as a "heat bank" for a solar hot water collector. Additionally, there was a separate area in the yard (much deeper than 4 ft. I think) that also had the same type of sand heat bank.
I think the sand contained lots of coiled up piping. In the late summer, they started diverting water from the solar collectors through the sand to heat it up for the winter.
If I'm not making this whole story up I think the whole system was intended to radiate up into the slab and then into the house. I also seem to recall there were some serious issues with controlling the heat in the house if you started the whole process too early in the heating season.
I don't know anything about the thermal properties of sand but I seemed to remember thinking maybe a deep, buried sand pit would make heat storage area. Store excess heat from the summer to, at worse, preheat your water that feeds to the water heater.
Just a brainstorm. I have no idea if such a thing has been tried or would work.
Sand is cheap where I live...wouldn't cost too much to try. Doubt if it would hurt.
Every year, someone builds an expensive solar thermal storage heat system to try to store summer heat for winter use. I've reported on several such houses -- most involve 10,000 gallons of water (or more) or several feet of sand surrounded by insulation. None of them have been shown to be worth the considerable investment. Several pilot projects have shown, surprisingly, that it may be cheaper to make hot water in winter with PV than with solar thermal -- because a PV system can get credit for summertime production, while solar thermal can't.Bottom line: it's not too hard to store thermal energy for three days. After three days, though, storage because expensive or impossible. Compared to German builders, American builders are obsessed with gadgets and technology (solar thermal, for example) and neglectful of their homes' envelopes. The moral of the story: we need more homes with 12" or 14" thick walls and triple-glazed windows, and fewer gadgets.
Just curious...the tankless water heater thread got me to thinking about this.
Couldn't a water supply line (like from a municipal source) be buried a foot or so below the frost line in zig zag fashion with pex or copper so as to "pre heat" the water, bringing it up to 60 degrees or thereabouts?
Where I'm at in middle tn our municipal water can be as cold as 43 degrees (so says the water company) in winter.
I'm thinking "poor man's geothermal preheating".
A pex or copper loop would be a pretty cheap investment...the only thing I can think of is perhaps there would be a significant enough drop in pressure to warrant a whole house pump? For many, that would probably kill the idea...even if it could work.
That's why it's at 43 degrees. Although I suspect errors in that number.
Where exactly (zip code) are you?
How deep are your footings in new construction?
Deep down, 100 ft or so, at around 45 degrees latitude, your ground water (in the Great Lakes area) should be about 55 degrees give or take. I suppose it could be lower as the source goes thru colder strata, such as within a foot of frost, but would think the 43 number should be higher.
How deep are the municipal lines?
That's why it's at 43 degrees. Although I suspect errors in that number.
I thought it sounded low too. I checked it the other day with a meat thermometer, letting tap water flow into the cup in which it was place for a couple of minutes. It read 47.
Where exactly (zip code) are you?
38555...Crossville, TN
How deep are your footings in new construction?
Everyone here, myself included, usually pours strip footings, at least a foot thick, about 16" deep. They then get covered when backfill is placed around the foundation.
Deep down, 100 ft or so, at around 45 degrees latitude, your ground water (in the Great Lakes area) should be about 55 degrees give or take. I suppose it could be lower as the source goes thru colder strata, such as within a foot of frost, but would think the 43 number should be higher.
How deep are the municipal lines?
I cannot be certain. My tap, placed by the city, is only about a foot deep or so. I think contributing to the water temp is that I'm only about a mile or so from the treatment plant.
So would the concept work if the water line is placed deeper? What if a loop was created by hanging it from the floor joists in an insulated crawlspace...would that act to preheat I wonder? Maybe a loop under the crawlspace but inside the footings? I would think the ground would be warmer there.
"What if a loop was created by hanging it from the floor joists in an insulated crawlspace...would that act to preheat I wonder?"
I would think your loop in a crawl space would have to be pretty big for this to work. The specific heat of air is low, so you would need a large amount of surface area to warm the water sufficiently.
If the water is just sitting in the lines between uses, I expect it would normalize, but when you're calling for something as low a one GPM, the flow through the pipes would be so fast that the water would be out the faucet (or in the WH) before it could really make a difference.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
I was definately only thinking about between uses.
Does anyone here have any experience with heat pump water heating/pre-heating?
It seems a shame to waste the heat that is removed from the inside air in the summertime.
I've often wondered if anyone has used that type of heat and sent it to their clothes dryer somehow.
I've also thought it'd be great if the refrigerator shared it's innerworkings with a heatpump. The idea is no more heat being thrown off from the refrigerator into the heated/cooled space. Maybe tie it back to the thermostat so that when the heat is on, refrigerator runs normally. When A/C is on, the heat from the fridge is taken outside...or to a hot water tank?
Just some crazy thoughts, that's all.
in cold climates , heat pump systems are expensive to install and expensive to maintain
super insulation and low tech solutions are much more effectiveMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Many years ago we had our AC guys relocate the compressor for a Sub Zero frige. The homeowner didn't want to hear it running. We build a shelf in the walk-in basement directly under the frige to keep the lines short.
I was also thinking about it from the standpoint of simplicity and integration, not only energy efficiency. (If it is more efficient) Just one unit that provides all of the heating a cooling needs in a house including dryer, referigerator, and maybe even oven?
Crazy thoughts--you and me both.
I've wondered similar things, but was thinking that you need domestic hot water the year around, so why not hook refrigerator coils and air conditioner coils to the water heater? (Put the coils in a tank leading to the water heater to pre-heat the incoming water--I think if you put them right in the actual water heater tank, they would eventually get too hot to remove any heat from fridge or the house). I was at least going to open the wall behind my fridge to the basement stairs, so the coils would get some coolness from the basement, but it seemed like a lot of work for little potential result.
The theory is great ... trouble is ... it gets complex fast. Dissipating e.g. your frig or A-C unit to a water tank that is hopefully around 120 degF ... you've created an environment that is way too hot for both. If you only use them when the water heater is cooler (which time wise is not very often), then the theory works. However, now you have to have a dual system condenser (i.e. one outside and one in your water heater for A-C). Also, you can't 'just' stick a refrigerant coil in a potable water tank ... a major no-no. You have to use a heat exchanger (HX). Imagine having to hook your frige into a remote coil. Complicated.
They do the refrigeration heat recovery strategy in grocery stores all the time. A different animal, different loads, etc. Bigger loads justify more complex and expensive systems. Large building also recover heat off primarily chilled water systems (for large space cooling applications). Instead of dissipating the heat to a condenser/cooling tower ... they recover at least some of that for thermal heating uses (domestic hot water).
The theory is great ... trouble is ... it gets complex fast.
That's what i was afraid of. Like I said, I would use the coils in a pre-heat tank rather than in the actual heater, but then, as you say, sticking a refrigerant coil in potable water is a no-no, so then you have to have some sort of heat exchanger, and on and on.... Maybe just run the supply water for the water heater water through a manifold that touches the back of the refrigerator/AC coils on its way to the water heater. Not very efficient though.
I knew a guy who ran his domestic water pipes alongside the heating pipes, so in winter it preheated the hot water going to sinks and tub/shower. Problem was, he ran the cold water lines that way too, so getting a nice cool glass of water was out of the question in the winter!
"I was at least going to open the wall behind my fridge to the basement stairs, so the coils would get some coolness from the basement, but it seemed like a lot of work for little potential result."
That's a great place for a passive air inlet if you are in a heating-dominated climate. If your fridge is on the exterior wall, the cold air coming from outside will be tempered when the fridge is running, which will also make the fridge run more efficiently.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
What if a loop was created by hanging it from the floor joists in an insulated crawlspace...would that act to preheat I wonder?
Uh ... no and yes. It would preheat ... using the paid for energy from your house to do it ... so not really an effective thing ... plus you end up w/ a bit of a radiant cooling floor ... cold floors ... and in the winter ... not good.
47 deg?! Wow. I too am surprised at that temp. I ain't no expert in ground water temps, but that seems really low. I've talked to well drillers in various situations and they tend to say 55 and above depending on location.
Clewless,In my mind, I've been kicking around an idea for the last couple years.It would be an an active solar system w a big tank of water to store heat,,,,, and,,,,, in the winter, the system would be supplemented by a small wind turbine to heat the stored water.No batterys, no inverters, no x fer switches, no reverse metering,,,, simply when the wind blew, the turbine would heat water.Ever hear of of anyone doing this??Thanks, Harry
I think that generally using solar/wind to create electricity to convert to thermal energy is not a very good use of that energy. Not sure I can explain to you why. I've been in the business so long ... I forgot the why part. This is the case w/ solar for sure ... use a thermal system for e.g. domestic hot water. Use a PV system for electrical uses. Area for area ... you will get more energy out of thermal systems, I think. Wind? Not sure. A little different animal.
If you don't want to use the electricity in an A/C environment, there are D/C products available ... including refrigerators.
One reason I've been kicking this idea around is I find myself living in a pretty windy area the past few years ( there are several large wind turbine farms in the area).I've also been thinking the heating load on the house is highest on cold windy days.I was also thinking instead of wind - electricity - heat, There is a possibility of wind - heat by mechanically heating the water.I'm sure the idea has already been analyzed by people wiser than me.Thanks, Harry
I still think the 47 is more a byproduct of my proximity to the treatment plant.
Where we live our municipal water comes into the house much colder in winter than it does in summer. Apparently the water gets chilled/heated in the water tower and the trip underground from the water tower to our house is not long enough to bring it back up/down to ground temp. While we're looking at ideas for solar water heat, I've toyed with simply running my water through a couple hundred feet of hose laid out in my sunny yard in summer, then into the water heater. I'm sure it wouldn't be terribly efficient but the cost would be minimal so it still might pay for itself. We're in a small town with no codes to comply with so I could do it myself. Anyone see any reason why this wouldn't work?
It may work, but I would question how good it would be for you to be drinking it--seems like a lot of chemicals would leach out of the hose--I know that many people drink out of a hose in the summer, but I would worry about day in and day out, unless the hose were special and made for potable water supply. I don't even like the taste of water from most hoses--I would think having the hose and water baking in the sun would not be a good thing.
On the other hand, I do know a guy who threw a black hose on his roof and ran water through it to heat his swimming pool--but then you aren't really drinking all that much swimming pool water.
I don't normally take my drinking water out of the hat water tap so not too worried about that.
That is called bi annual heat storage. Many people swear by it. Successful if done and controlled correctly. Great where you have excess energy to be able to store (like in the Southwest where there is lots of excess sun in the winter).