solar integration primer?

hr

while in Dallas recently the front page news had a story regarding the local utility offering "off peak' rates to residential customers.

They didn't indicate how much cheaper the KW rate would be after 6, but with the right $ amount could, and would it be wise to electrically heat a storage thru the evening hours and pull heat all day long without spinning the meter.

I have already seen some thermal storage packages in some of the trade mags. A salt based solution, perhaps?

I'm not sure how you could cool with thermal storage?

The article claims other electric providers are considering off peak rates for residential customers.

What say you, Perry.

<A HREF="http://www.heatinghelp.com/getListed.cfm?id=144&Step=30">To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"</A>

CC.Rob_2

need some reading

I'm trying to learn about how I might integrate solar into the existing DHW and space heating in my house. Anticipating that perhaps in the not too distant future there will be sufficient incentives to make the payback time reasonable. I have been reading the various solar-related threads here with interest, but I can't seem to find anything here or on the web that is a decent "here's how it can be done" guide to how solar is integrated into a "typical" home heating and DHW system.

For example, my house (of course!). One gas boiler, two heating zones of fin-tube using ODR that spend 2/3 or more of the heating season at supply temps <140F. Indirect water heater. Existing piping and pumping good to excellent in terms of potential for future integration.

There's plenty of info for sizing panels, loads, etc. but I'm unclear on exactly how it all hooks together, both in piping and control. Is there a primer somewhere?

Thanks.

ALH_4

solar

Viessmann has a solar design guide that might be helpful.

Generally, the most cost effective installation is domestic hot water pre-heat with an additional indirect tank. Space heating can also be accomplished but the ROI is less because of solar availability being low when the demand is highest in the winter. Storage is the most difficult problem to solve.

SDHW is as simple as a collector connected to the coil in an indirect tank with a control that determines when the collectors are hotter than the tank. The cold water inlet goes to the solar heated tank first and the outlet from the solar tank goes to the inlet of the boiler-fired indirect. Usually a Tekmar 155, a Grundfos 15-58, a 79gal tank and a 4'x8' flatplate is the most cost effective and simplest way to go.

CC.Rob_3

awesome

Thanks Andrew. That is exactly what I was looking for. Both the manual and your description.

Dave_4

Exactly what I've been studying and agonizing about for well over a year. Convention says that it (space heating/DHW integration) can't be done as it's just more practical to use solar only for DHW or DHW pre-heat.

Such "convention" however [seems] to have been developed before mod-cons.

All I can say is to begin the space heating process when your mod-con is forced to cycle off... In the case of a Vitodens 200 directly connected to a TRVd system even the energy required for DHW pre-heat can eliminate hundreds if not thousands of operational cycles per year. Nothing about the Vitodens 200 has amazed me more than its ability to act as an extremely efficient batch heater but nothing has aggravated me more than the fact that it's required to do so...

[Deleted User]

The more I think about it...

The less enamoured I am with solar thermal.

The problems are well documented. When you need it the most, you get it the least. When you need it the least, you get it the most, and if you are not prepared to deal with the excess, your mechanical package (glycols, collectors etc) pay the price due to thermal degradation and stagnation temepratures well in excess of 350 degrees F at the absorber.

My feelings are that eventually, someone will come up with a cost effective seasonal thermal storage method/media that will make it all worth while. But for the mean time, at least here in Colorado where the utiity is REQUIRED to buy back excess electrical production, I'm thinking PV solar makes more sense for the world as a whole. If during the summer months, the dwelling to which the array is attached can not use the electricity being produced by the PV system, it goes back into the grid, helping to offset the demand imparted to the grid from cooling loads. Kind of matching demand with availability if you will...

I realize that not all states are as fortunate as Colorado is, and the local utilities fought this proposition tooth and nail, and it was put up for a vote, and the voters approved it. I suspect that most Americans would approve it if put up for a vote.

Now, with that said, the one place that solar thermal DOES make sense, is in those situations where the demand for heated water is continuous. Places like laundry's, manufacturing processes, parts washers, breweries etc. Storage can be held to a minimum if demand outstrips availability, which in large commercial operations, it usually does.

But as it pertains to residential use, my money is being bet on PV panels. At most, a small solar thermal DHW pre heat system to give that warm fuzzy feeling when showering in the morning...

Not trying to be a green curmudgeon here, just trying to do what makes the most sense.

BTW, the preliminary numbers for my solar thermal ground storage project do not look very good. Could just be my soil conditions, but it doesn't impress me as something worth persuing much further. I'll let it run for a whole year just to have the necessary data required to make a logical decision, but the preliminary winter numbers don't look good...

ME

hr

I tend to agree, Mark

for a small to average size solar heat package I figure 20 grand or more, not counting the radiant portion. And in my area that might cover 30% of the heat load.

I've got one in progress now that will run in excess of 35 grand for an 8 panel radiant DHW.

Keeping in mind you still need a boiler sized to the design load for those weeks on no sun

And I still have the question of what to do with that solar capacity all summer long?

I'll sell SDHW all day long, but you need to be realistic when folks start shopping solar radiant heat systems.

Build a new house and face it south would be my best solar heat suggestion

Now for a DIYer that an find some used equipment and likes to tinker, that's another story. I'll bet I could sell hundreds of used panels at $150 each. I genrally have a waiting list.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

CC.Rob_3

I have been wondering the same thing

But in a different way. Points very well-taken.

I had been wondering about the pattern of our DHW use, which is showers after the sun goes down for some, and showers before the sun comes up for the others. Not a lot of solar recharge going to happen between major uses. And if we ever start to see variable electricity pricing according to peak use times, then even more DHW use will switch to off-peak (night). Dishwashing is already a nighttime event, but laundry would definitely go after-hours to avoid peak pricing.

Sorry to hear about the hole, Mark. Hey, in the oil business, dry holes outnumber productive ones by a pretty substantial margin. How about another test hole down the street?

[Deleted User]

The next test hole....

will be horizontal, from the inside of my basement, out. (SHHHhh don't EVEN mention this to my wife...)

I'm thinking if I can keep the heat in the top soil that I'd be better of conductivity/retention wise.

Boy, is THAT going to make a mess :-)

Am going to have to wait for her annual girls weekend in the hills before I pull this one off...

ME

[Deleted User]

Old Solar saying....

(Actually derived from sailors)

Red sky at night, solar delight.

Red sky in morning, solar take warning.

In other words, if you have a red sky at night, use as much DHW as you can to make sure you have exhausted the solar pre heat tank to make room for more energy. If the sky is red in the morning, postpone hot water usage to conserve what you have.

Relatively accurate most of the time around here...

ME

Spudwrench

PV solar vs. solar thermal

I hope this isn't a patently ignorant question, but does anyone use PV panels to charge batteries and run an electric boiler? (as supplemental heat...) I can see how inefficiencies in this process might "stack," but it might be a way of storing the sun's energy during the day to assist with the heating load at night. My hunch is that the size of PV panels needed to accomplish any meaningful amount of heating would be ridiculous...but I would be interested to hear the opinion of others who are better informed.

Nathan

jp_2

PV's what are the costs?

Mark,

have you run any numbers? what you say sounds peachy but....

if you have enough electricity to 'sell back' why connect to the grid in the first place? store that excess and use it at night. I've heard it requires a special $500.00 'sell back' meter.

what is the 'sell back price' for a kilowatt hour?

if you look through the Real Goods catalog, you can build up a 1000watt system for around $10,000.00, grid tied system.

if you are not using it, say you can sell back at 10 cents a kilowatt hour, you are now making 10 cents an hour with a $10,000.00 system, or maybe $1.00 per day. where does this make any sense?

i don't see where you are coming from on this?

you are much better off just to conserve.

ALH_4

efficiency

The main difference is in the efficiency of solar thermal panels compared to the efficiency of PV panels. Solar thermal panels are many times more efficient than PV panels at capturing the available solar energy. Storage is a problem either way, and I personally would rather have a big tank of water than a room full of batteries.

Creating enough storage to account for daily variations in solar availability is hard enough. Storing a summers-worth of heat for use all winter would require such a storage tank that it would be impractical...perhaps a small super-insulated lake. And the storage would be over such a long time that heat loss becomes a huge issue. Heat loss that resulted in 1°F per day temp drop would be a killer.

A much better investment is to super-insulate the home and plan for passive solar heating.

Just my take on the issue.

CC.Rob_2

shallow, eh?

Maybe check this out:

http://www.geology.udel.edu/wehmiller/GROUNDTEMPINTRO.html

It ain't Colorado (sites from the whole Atlantic coast), but there's some interesting data on the temp variability of shallow ground. Shaded sites vs. sunny sites, well-drained vs. poorly drained soils, etc. Also the magnitude of the variability. No full papers on this yet, but I understand they're in the works.

CC.Rob_2

cost, virtue, etc.

I think the point is that PV might be simpler all around. Depending on quantities and patterns of electricity and DHW use, PV might make more economic sense as well. If the average Joe wants a largely plug-n-play system without having to deal with the issues of water storage or battery storage, then going PV and selling back to the grid is perhaps simplest.

A colleague had a PV array installed about a decade ago. Can't recall how many kW, but it's a roof-full. He sells back about $20-40/mo. He estimates payback on the overall investment in about another decade. He knows he's not saving any money for about 20 years in total, but feels strongly that over the long-term, it's the right thing to do.

This thread has certainly given me pause, and cause to run the numbers PV vs SDHW and see which wins. Thanks for the discussion, all.

ALH_4

F-Chart

You might also try the demo version of F-Chart when comparing.

Tim P._2

Unless you have a huge PV array or a really small house, I don't think you will be selling back any energy to the utility company.

An easy computation would be to figure out how many kilowatts you would produce on an average day, multiply that by the utility co's rate and see how much you would save in a year.

I think the only way it would be worthwhile from a monetary sense is through incentive from the federal/state/local governments. The Town here put an incentive of $1000 to the first 5 people who installed slar systems. Couple that with state/fed grants as well as equipment subsidies from the local utility co, it's not that bad of a deal.

Are you going to make money? I doubt it. However, I think it is reasonable to believe it will pay for itself before it needs replacement. And of course there is the apparent benefit for the environment (I say apparent because I don't know if they kill small animals to create the photovoltaics) and reduced reliance on foreign fuel.

I think from a strict dollar standpoint, if you are not receiving or taking advantage of significant incentives, it is probably not going to be the best investment you could make.

Tim

CC.Rob_2

.

Ok, so my hours/days spent calculating just got reduced to minutes. Thanks!

jp_2

CC

think of the money your friend could have saved if he designed and built a system to provide just enough power for his needs? once again, $10,000 investment returns you about a dollar a day? how much fun is that?

i have a $400.00 system, off the grid and I have the power i need. if i need more, I'll buy a panel or two and another battery.

Ericjeeper

I was on HotRods list

I bought six panels from Bob, and I am very pleased with their function. Sure the sun does not shine every day. But on the coldest days in the winter. They are generally bright sunny days. As the lack of cloud cover is causing the colder temps.
Between the solar panels and my small home built woodboiler I have stopped my heating with fuel oil entirely.Screw their 2.50+ a gallon dino heat

Cosmo_3

;(

What a depressing thread...

I was hoping ME hit the big time!

Cosmo

Mike T., Swampeast MO

Mark:

I have to agree with you--mainly. Talk about "green curmudgeon"--that's what happened to me with the post about a certain former VP...

PV still has a problem of efficiency that's usually terrible compared to fluid transfer, but at least delta-t is to PV what head loss is to a gravity conversion system...

Passive solar design combined with an extremely efficient shell [still] seems to be the best use of solar by far. Even the dead man who built my house used passive solar--when the 80 acres he originally owned were developed his house remains ideally located to receive energy from the sun...

Where I won't agree however is the [supposed] impossibility of using solar energy via fluid transfer on a real-time basis for space heating.

Why? Because such supposition appears to be based on experience before modulating/condensing boilers driving a "wild" system with constant circulation of fluid that's ideally heated to just the level required to maintain the desired space temperature.

No such thing yet as boiler that can modulate down to less than 1/5 of its full output with 1/4 or 1/3 more common.

Since boilers are rightfully sized to allow the ability to raise temperature in all but the most extreme weather and considering that weather in much of the U.S. IS HIGHLY VARIABLE it only follows that even a well-sized mod-con will spend a significant part of its space heating season with a loss less than minimum modulation.

MAKE HAY WHILE THE SUN SHINES!!!!

If your well-sized mod-con driving a true constant circulation system is already forced to cycle because of the outside temperature AND PASSIVE SOLAR GAIN there's a damned good chance that the supply temperature required at the time is quite low. Lower in fact than the temp required for DHW "preheat" during a time when DHW probably isn't being used!!!

If your modulating/condensing boiler IS running constantly then I'll say it's impractical to collect enough solar energy to satisfy and it's best to use the solar for DHW heating.

The key here is control. I'm trying. I have my idea. There's no freaking reason it won't work even if the Germans say it won't. After all the Germans live in Germany--not the mid-Mississippi Valley...

Kevin_in_Denver_2

PV vs. Thermal

When you add the historical unreliability of solar thermal to this equation, then the choice becomes more obvious. Simply put, there are about six things that can fail in a thermal system, and only about two in a PV system. Most homeowners don't know when something fails, and the investment is worthless when it's down.

Recently developed web-based monitoring systems, however, could help the installers keep an eye on performance at low cost.

ScottMP

Once Again I come to the wall

for the Real Truth and have my eyes opened.

As a plumbing and heating contractor I have a few customers asking about solar. Looking to the future for my business and being a child of the seventies ( remember Earth Day ? ) I am interested in Solar. The numbers seem to say that for the N.E. I should be looking at small DHW solar systems that would supplement a traditional system. The Glycol seems to be the messy part, with the breakdown due to high heat, the real maintenance issue. Start to sell service contracts ? Is that what you say ? Could be !

Viessmann plates ( they seem to allways be the best ) are fairly expensive and a system to supplement an exsting DHW tank is quite the investment. Does that mean, only for the truley Green ?

The discussion of off peak use and production times is interesting. Would'nt use at night and storage during the day for re-charge at night work just fine ?

Scott

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Tim P._2

> system. The Glycol seems to be the messy part,

> with the breakdown due to high heat, the real

> maintenance issue. Start to sell service

> contracts ? Is that what you say ? Could be



Since the high temps were mentioned more than once, thought I'd add a comment.

It was recommended that when temps get too high (eg summer, no call for heat), the heat in the system be diverted into the earth.

Bury a coil of plastic in the earth, when the temps get to a certain point start circulating the water through the piping.

Prolongs the life of the panels at the expense of running a circulator for no useful reason. If you could get gravity flow to do the job, that'd be a home run.

Tim

Perry_3

Long Term Thermal Storage Capabilities

I have actually been playing with the idea of a solar heated house - off the grid house - for several years.

Built from scratch - designed for it - No $ limit.

Wiconsin is fairly cold as things go - and has 1/3 of the days cloud cover.

So how do you build a solar system that during the summer essentially captures and stores enough heat to run for the coldest 4 months of the winter? Phase change thermal storage.

I've come up with that I would need several rooms full of heavy and sturdy metal tanks (with sub "tubes" of other metals in them) with phase change metals in them (they are long term stable). Metal 1, melts/solidifies at 100 F, Metal 2 melts/solidifies at 120 F, Metal 3... at 140 F... metal 4 at 150 F... Metal 6 at 160 F... Metal 7 at 180 F. (or some such arrangment). Do I use 3, 4, or 6 metals...

The metals used would be low temperature solders (and you can get one alloy the is liquid at room temperature).

Not cheap - but would work.

I've been tinkering with tank and heating coil design ideas so that these things should last 100+ years with ease... (and that is not so easy). You would not want to deal with a leak).

Essentially - I would have about the same square ft of house just for superinsulated "heat" storage tanks.

To handle that "cold" weather... the tanks would be able to hold about 1.5 years worth of heat. All to be recharged in the summer.

The solar panel area would be very large as well.

This is more of a hobby of mine that I tinker with when I have time.

Give me another year or so and I may have a design that I think would be robust enough to work.

Perry

Dave_4

Have you investigated the ideas at

http://paccs.fugadeideas.org/tom/index.shtml

regarding "Passive Annual Heat Storage" (PAHS). The idea is that if you can keep a big enough area of dirt dry, you can store a lot of heat in it, apparently enough to do most of your heating and cooling. Basically you use gravity to channel air though tubes in one direction in the winter and the opposite in the summer to warm/cool your house via the stored heat in the dirt. You use plastic sheeting to create a big "umbrella" to keep the dirt around your house dry.

Ed_26

Primer

To your original question - Tom Lane's book: Lessons Learned, 1977 to today has piping & control schemes that may help you. Further, Retscreen program is available on the web (free) to further help design/size for a given location. Check them out.

Bob Gagnon plumbing and heating

Solar Hot Water- Domestic and Heating

Is the way to go. We need to shower and heat our homes, 2 essential activities. Heating bills are a lot higher in my area than electric bills. I would expect a properly designed solar heating system could last 50 to 100 years, like a forced hot water heating system. It is hard to sell these systems because it is not a done deal yet, we have to make these systems better, that's what makes it so exciting! I think we have to install this in our own houses first and iron out the few remaining problems. Collector prices are falling and fuel prices and tax incentives are rising so these systems are going to make more and more sense. Mark, don't give up, we need you, my big tank loses a lot of heat too. But maybe we don't need seasonal storage, maybe we just need to harvest and store enough heat to last a week in a super-insulated foam house. People are under-estimating these systems if they think you can only get domestic pre- heat. I get 100% of my domestic hot water and I heat my bed every night in the winter with my hot water system. Like Eric Jeeper I burn wood too, but I have been off the oil for 2 years now. Having too much hot water in the summer can be easily taken care of by using a large storage tank. You also could easily cover or tilt your collectors to a steep winter position and collect way less energy. You can also ramp up your hot water usage in the summer by using hot water to wash your clothes, cars and trucks.
Water is something we can work with, lets face it we are Plumbers. We won't be splitting atoms to create nuclear energy, and we won't be splitting hydrogen molecules for fuel cells either. But I bet we can make hot water work a lot better than it does now. A lot of people feel that PV and solar hot water are ahead of the renewable energy pack and I feel it is our duty to give this our best shot. America's energy consumption is like a runaway train- no one thing is going to stop it, we have to come at it from all angles. Solar hot water will be part of the solution. We had a Noreaster up here today, and I just checked my 1500 gallon storage tank and it is 92.3 degrees at the bottom and my smaller 200 gallon tank is 121 degrees. Well I'm going to take a steaming hot solar shower, and later on as I fall asleeep on my solar heated mattress, which will be about 75 degrees, I will think of you guys and hope more of you step up. Together we can do this. Bob Gagnon

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Ed_26

solar thermal

GO BOB!

CC.Rob_3

1500 gal

That's a tank interior about 8x5x5 ft. I have room for that....

dr al

finishing touches on my DHWS

this is slightly off the question of DHWS but I have one turning on in 2 months. THis is what I can offer to help "incorporate".

I started my trip 2 years ago and found that most suppliers had parts but couldn't or wouldn't give the actual estimated BTU due to solar variability. I did not look for many engineer/designers as they use selected products it seemed.

As a former scientist, I liked the numbers to add up. I would have thought there would be a base line most referred to. SO as it seemd I could guess just as good, this is what I've come up with.

I have built a well insulated not super insulated 1000 sqft addition with triple pane double argon windows that are directional for solar gain in the winter months. (I have almost 40% glass, most due south)

Additionally, A heatpump as a terciary back up when I did not have enough storage heat and the temp outside was preferential. (this way my collectors can work when conditions are less than ideal)

I have also gone with a manifold of 100 solar tubes @ 75 degress to accent the winter advantage and decrease the summer here in Maryland. THis is to supply DHW and hot water for radiant heat in the winter and future ice melt for the side walk (and sumer heat sink)

(incedentally, even though tpex or pex-al-pex rated @ 200 degrees @ 50 lbs, the manufaturer responded to me that a extream temps or high temps for extended times, they are unsure of performance. THERFORE, I SELECTED COPPER PIPE for both supply and return to the manifolds)

Two double coil solar tanks (expandable) with a in line electric tankless boiler for water back up.

No SUPRISE... The radiant heating ia a concrete slab (with 2" extruded polystyreen below) and warm board. Both estimated to run @ 110 and 87 degrees respectivly will create a demand for reseve supply. (due to the issue listed below I am planning to make both run @ 100 degrees)

this is where I come to full stop.

plenty of ideas but as it was stated earlier, lots of ideas but no one has 'THE BEST' heating management arrangement to give a guy like me assurance I hooked it up the best way.

Looking for the heat management system to control it all.

Pay back is imaginary, cost has been a issue, I was planning to spend 20k on solar only, it now estimated finished @ 25k. The increase has made my wife less than happy.

hr

control thoughts

I've just started looking into the controls this company offers. They are showing up a lot lately on the various Euro systems arriving over here.

http://www.resol.com/en/english.shtml

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

ADL

Not sur eif this will be suitable from a control standpoint but check out www.solarnetix.com. They sell control modules for Solar DHW systems.

Bob Gagnon plumbing and heating

1500 gallon tank

You are right CC Rob, my tank is about 8'x 8'x 4'. If you are getting ready to install a system, give me a call, I would be happy to let you know what did and didn't work for me. Bob Gagnon 978-853-4873

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

John Taylor_3

Bob Gagnon plumbing and heating - Solar heated Mattress

Saw your reply of March 2nd and wondered; is it a water bed or some other mattress heated by water?

Bob Gagnon plumbing and heating

Solar Heated Mattress

It is a conventional mattress with 96' of pex underneath. I used to heat it with my boiler, but when I went solar it was a good way to use my lower temp. solar BTU'S. Bob Gagnon

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

John Taylor_3

Solar Heated Mattress

I thought you were talking about a regular mattress. Now I'm really interested - 96 feet of pex - how is it arranged, sepentine? Is it fixed to anything to maintain it's shape? Or just laying between the mattress and box springs? Is it PEX-AL-PEX, what diameter? How did you integrate it into your system (tie it in)? Is it on a TRV with a remote sensor? Thanks - I know these are a lot of questions - it just seems like such a good idea.

Bob Gagnon plumbing and heating

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Bob Gagnon plumbing and heating

John

3/8" regular pex secured to my water bed frame, 6" on center. I replaced the water bed mattress with a regular one. I use primary-secondary piping with a probe thermostat under the mattress. I heat it to about 75 degrees in the winter and in the summer when my radiant cooling is running, it gets down to about 62 degrees with well water running through it. And you guessed right John, it is really comfortable, and a great way to save energy, you heat only the bed all night. Bob Gagnon

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"