Solar Collection Question

Mike T., Swampeast MO

Yep, a 12 hour and few minute day on the summer solstice could find Cape Girardeau somewhere in Equador South America!

Length of day here on June 21 is 14 hours, 44 minutes.

Boulder, CO (close to the latitude from the other chart) has a day length of 15 hours, 1 minute on June 21.

Only 17 minutes or about 2% longer.

Mike T., Swampeast MO

I've searched and searched and can't seem to find the answer to these questions.

1) Insolation (both daily total and hourly average) are available from a nearby Agricultural Weater Reporting Station (Under "Weather Location" at the top, "Delta - Cape Girardeau County" is closest to me--about 10 miles away.)

By the definition they provide, the values should be the energy received per square meter on flat ground. Is this correct? The data (hourly and as the sun changes inclination through the year) seems to verify this. e.g. the closer to solar noon, the more energy; and the closer the sun to directly overhead at solar noon the more energy on a similarly clear day.

If correct then a collector of 1 square meter flat on the ground would have this much solar energy available, right?

Again if correct, it's the actual angle of the solar collector that's causing me problems.

See drawing named "Perfect Collection.jpg". Collector is at 45 degrees and sun is striking it perpendicularly. Am I correct that it is receiving the solar energy as striking the "this much solar" line? (Think only of solar noon.)

Now see the drawing named "Sun Too High.jpg". This seems fairly straight-forward as well. As the sun becomes higher and higher, the "this much solar" line gets shorter and shorter. This would [appear] to self-compensate for the less-than-ideal sun-to-collector angle.

Now see "Sun Too Low.jpg". Using the same logic as in the above, the "this much solar" line gets really long and it does not seem to self-compensate for the less-than-ideal angle.

If I use these methods to compute the actual amount of ground "seen" by a collector of a given aperature area, it seems to work fine as long as the sun angle is not lower than the collector angle. As the winter solstice nears, I get what appears to be a ridiculous amount of available energy. How do I compensate?

jp_2

flat on the ground

thats what i would think.

when sun is overhead, summer, you get the highest energy per sq meter, anything less,spring,fall,winter, is less energy per square meter.

Test:

use a flash light, it puts out constant light intensity.
when you shine on a piece of paper perpendicular you get the brightest light from the light beam.



as you tilt the paper at different angles, you still have the same brightness from the flash light but now your light spot on the paper is larger, with same flash light output the energy per square meter has to be less.

added:

your drawings look somewhat correct, as in "sun too low". you should find that the large area in red will have the same power as the solar collector perpendiclar to the suns rays.

one more added point here:
both areas will have the same watts, not watts per sq meter!

Simply Rad_2

Viessmann Solar!

Here is out of the Viessmann solar design manual.
I think this will help you.

Jeffrey

Uni R_3

Install sheet for a quality thermopile pyranometer

http://www.kippzonen.com/download/kipp_instrsheet_cmp22_1721.pdf

Simply Rad_2

Viessmann solar

Mike
Here, this is out of the Viessmann solar design manual.
I think this will help you. Viessmann really strives on education which comes lots of research.
Jeffrey

Mike T., Swampeast MO

I certainly have that manual and have studied it well. Still doesn't seem to help much however when it comes to attempting to use actual insolation data to estimate output on a short-term (say hourly) basis.

Do you have the attached document?

Can you make out the "Efficiency Equation" and "Incident Angle Modifier" notations at the bottom? They don't look like equations to me. Are they perhaps values for standardized equations for such computation? If so, I've seen at least two different "standard" efficiency equations and haven't yet found an "Incident Angle Modifier" equation. Can you or anyone provide?

Mike T., Swampeast MO

I printed that manual long ago and have studied numerous times. Unfortunately, it (like most others) is based on averages with regards to insolation as well as strictly conventional applications. For instance, it assumes that combined space heating/DHW applications do not work...

Very little help when I'm trying to estimate solar input on an hourly basis...

Do you have the attached certification document?

It's both helpful and confusing to me.

Do you understand the "Efficiency Equation" and "Incident Angle Modifier" at the bottom? Doesn't look like equations to me. Are these perhaps values to use in "standard" equations? I have seen at least two "standard" equations for efficiency and don't seem to find one for incident angle modification. Can you or anyone possibly provide?

Also seems odd that a collector specifically named as 2 square meters has 2 1/2 square meters of aperture area. In the way I'm attempting to compute, shouldn't I be using aperture area?

That agricultural reporting station reports daily insolation in megajoules per square meter per day--just like the left side of the chart. The "Clear" value of 23 MJ/sq.meter/day only seems to happen around the summer soltice. That's what makes me think that the insolation values are based on energy received on flat ground and that I must compensate for the collector angle where the collector is effectively working with the energy received by its shadow...

Again, such seems to work fine if the sun is higher--but not when it's lower. Around the winter solstice I get insanely high collection values like 150,000 btu/day for 2 x 2 meter (rated) panels at 45 degree inclination and the sun at 29 degrees.

Glen

insolation efficiency?

Looking up my info for your state - it would suggest that 4-5 kwh/sqM is an annual average for available insolation. Your orientation to due south, encroachment of shade due to buildings/trees and the efficacy of your collectors all factor in too. If you wish to track this as accurately as you did relative to the vitodens install - might need to develop your own criteria and measurement methods. And do you wish to fine tune for winter radiation angles or summer? BTW - which panels are you considering?

Mike T., Swampeast MO

Understand "test" perfectly. That's exactly what I'm asking. Are these insolation values based on the energy received in a square meter of flat ground or a square meter of energy if it were angled towards the sun?

Regarding "added", that's sort of what I was thinking. Should I calculate the "red area" as if the collector were perpendicular to the sun and then apply the incident angle modifier? While I'm unsure of the source I did find a rather impressive solar design website suggesting that evacuated tubes still maintain about 98% of their possible output when 20 degrees off of vertical perfection.

Do though explain your last sentence, "Both areas will have the same watts, not watts per sq meter!"

Mike T., Swampeast MO

"Develop your own criteria and measurement methods." That's EXACTLY what I'm trying to do. I'll do my best but it just seems odd that I can't find anything to make it MUCH easier. Then when I do come up with something I'll be savaged for it being merely site specific, e.g. useless...

Fortunately shade encroachment during the winter months will be negligible. A bit during summer mornings, but only because of a tree that I want to replace anyway...

As to radiation angle, I want maximum collection about 45 days on either side of the winter solstice. Looks like 50 degrees is about right, but I'm not sure yet.

Panels are Viessmann Vitosol 300.

Mike T., Swampeast MO

I forgot to attach the certification document and am not at the right computer. Will add as soon as I can.

jp_2

i could be wrong

but i think if you constantly correct for angle(s) you will get the same amount of energy year round minus the fact the days are shorter in winter. same energy per time then. so you'll still get x watts/sq m all the time, so to speak.

""Regarding "added", that's sort ...""
not sure what the incident angle modifier is? on thermomax's web site, incident angle correction is for panels not in optimum position when you need X output.

yes, i would say the red area is the flat ground w/sq m surface, so project up onto the panel to get its output, shouldn't need an incident correction if i'm understanding correctly.

last snetence:

lets say you recieve 100 w/sq m on your 1 sq meter panel. so you are getting 100 watts, that red area therefore is also getting 100 watts but maybe its 2.2 sq meters. thats what i was driving at.

Glen

AH -

self protection prior to vilification by the masses! :-) I seem to remember a "rule of thumb" back in the cobwebs somewhere, angle of latitude plus 22 deg for max winter insolation - but that might be for us canucks. For MO - that would put it at 58 - 62 deg inclination. And look at this site - http://www.retscreen.net/ang/home.php - but I think this site is focused on estimated savings - but its still worthwhile poking around its corners.
I too am putting in the H30 panel and plan to chart its performance via a few extra temp sensors and the flow meter built into the Divicon. A known flow with a known Delta T will give you the number I think. DWH preheat is my primary goal - we'll see if there is any residual for a heating panel in the office (book keeper is always cold).

Mike T., Swampeast MO

Here's the certification certificate I mentioned. Sorry for the error.

Mike T., Swampeast MO

self protection prior to vilification by the masses!

Not so much self-protection as awareness of what will happen...

Is there any real wonder why objective comparisons between space heating methods are nearly as rare as hen's teeth?

Mike T., Swampeast MO

Presuming that those insolation values are as collected on flat earth...

Here's my area specific theory:

Sunny winter days around here tend to be clear--glaringly clear. Summer days however are rarely clear--there is a nearly perpetual haze of humidity.

This sets up a situation somewhat contradictory to the conventional wisdom of "you have the least when you need it the most". The most available solar energy [seems] to be available when I need it the most.

While the most may be available then, a BIG part of the solar efficiency equation kicks in--difference in temperature between the air around the collectors and the fluid running through them. While the most may be avilable, you're loosing the most due to temperature difference--since, after all, it's cold in winter....

That's where I'm trying to use the solar energy to its best use regardless of the time of year. DHW preheat--I notice VERY often now that "preheat" is used instead of full domestic hot water heating--is not going to be the most efficient use in my system! DHW load is typically low during mid-day with the only exception being laundry day. With no DHW going out, you're not "pre-heating" you're HEATING!

When AT LEAST 25% of my heating days (say from mid-October - mid-march) can be satisfied with no more than 85F supply with a return at or near ambient indoor temp it sure seems to me that the best use of the solar is for space heating. The clincher is that I get decent passive solar gain such that my actual heat loss might be 40% of that expected via Manual-J on a sunny day when the mid-day temp exceeds 38F or so.

Uni R_3

Mike... re: the install directions

That link to a PDF that I posted up above shows how to set up a very high end model like they would use in any professional meteorological environment.

Those puppies are leveled perfectly flat! The sensor is in a small clear dome.

That said, you'd have to look at how it senses within the device. It is capturing the intensity in that little dome and expressing it as energy/m².

Mike T., Swampeast MO

I'll write the MO Department of Agriculture to find out what they're using.

Considering this is really related to growing row crops, it sure seems logical to me that it's the actual energy received by a square meter of flat earth.

Perhaps I'm naive but if you wanted to measure available solar radiation flat on the ground wouldn't it require little more than a simple device mounted perfectly flat that converts sunlight to electricity? Why would you want a hemispherical measuring device unless you were trying to measure insolation other than as received flat on the ground?

Larry Weingarten

I have an idea.

Mike, look up Zomeworks in New Mexico. See if you can get through to Steve Baer. He has a knack for taking the most difficult solar challenges and creating seemingly simple solutions. He WILL know ;~)

Yours, Larry

Glen

Vitosol

reacts nicely with UV - so bright sunlight is not required. Are you able to look at your daily UV index on an annual basis too? And yes there will be periods of time when your solar system is heating and not preheating dhw - which is why Viessmann Mfg Co Inc offers (developed?) the bivalent indirect. And there are several piping possibilities available to tie in the solar with your Vitodens - especially at your ultra cool supply temps. You might be surprised with the results. I have added just one solar system to an existing vitodens - but with LLH. You might have to phone either Waterloo or RI for their take on installation details without it.

jp_2

why hourly basis?

i understand what you are up to, but aren't averages good enough?

have you been here?

http://www.thermotechs.com/usdata.htm

gives solar out put for their collectors 10,20 and 30 tube. I understand they're the same collectors as veissmans.

i see solar space heating working on the extreme shoulder season and could work all year if you could afford all those tubes!

Solarstar

Hi Mike. I'm at 44 deg latitude.( 30 miles north of rochester N.Y.) I've set my panels at 55 deg for optimum spring and fall Btu's and then it helps to self limit the summer output simce my collecting area is oversized. I'm also off 25 deg to the east of true south.. I used to track my Sun hours(pump run times) for about 5 years. 85% of the hrs. were from March 15 to sept 30 . And the remaining 15% were after that in the winter. In other words very small amounts of btu's in the winter were the normal. On other hand I get alot of cloud and overcast blocking the sun and irritating me but i'm starting to get used to it. More to follow... Paul

CC.Rob_2

el sol

> Presuming that those insolation values _I_are_/I_

> as collected on _B_flat earth_/B_...

>

> Here's my

> _I_area specific_/I_ theory:

>

> Sunny winter days

> around here tend to be clear--_I_glaringly_/I_

> clear. Summer days however are rarely

> clear--there is a nearly perpetual haze of

> humidity.

>

> This sets up a situation somewhat

> contradictory to the conventional wisdom of "you

> have the least when you need it the most". The

> most available solar energy [seems] to be

> available when I need it the most.

>

> While the

> most may be available then, a BIG part of the

> solar efficiency equation kicks in--difference in

> temperature between the air around the collectors

> and the fluid running through them. While the

> most may be avilable, you're loosing the most due

> to temperature difference--since, after all, it's

> cold in winter....

>

> That's where I'm trying to

> use the solar energy to its best use regardless

> of the time of year. DHW preheat--I notice VERY

> often now that "preheat" is used instead of full

> domestic hot water heating--is not going to be

> the most efficient use in my system! DHW load is

> typically low during mid-day with the only

> exception being laundry day. With no DHW going

> out, you're not "pre-heating" you're

> HEATING!

>

> When AT LEAST 25% of my heating days

> (say from mid-October - mid-march) can be

> satisfied with no more than 85F supply with a

> return at or near ambient indoor temp it sure

> seems to me that the best use of the solar is for

> space heating. The clincher is that I get decent

> passive solar gain such that my actual heat loss

> _I_might_/I_ be 40% of that expected via Manual-J

> on a sunny day when the mid-day temp exceeds 38F

> or so.

CC.Rob_2

A.T.

Mike,

Following offered as background for what you're after. Illustrative purposes only. Certainly doable for your site with the right information.

Sounds like you want to compare seasonal, daily (or hourly) solar flux. We have an Eppley PSP pyranometer (very high end; often used to calibrate other pyranometers). It collects data at 10s intervals and outputs hourly averages.

You can use data for measured solar flux in conjunction with the solar flux calculated with no atmosphere. Done properly, this calculation also accounts for time (hour, day, year) and latitude.

Attached is a plot of solar flux for 2003 at a location at ~41.5 north latitude.

Pink is calculated solar flux with no atmosphere. Blue is measured daily total solar flux so it includes the effects of clouds, water vapor, etc. Two points here: 1) there is never (very rarely, actually) a day when you get more than about 75% of the possible flux; and 2) time of year trumps clarity of sky. Those clear winter days just don't deliver the flux that a even a moderately cloudy summer day does. So for here, anyway, the conventional wisdom holds. Earth spinning the way it does, I doubt it's any different where you are.

The top (nevermind the scale; I moved it up for clarity) shows atmospheric transmittance (AT), which is soradm/soradc and thus dimensionless with values 0-1. Basically just shows that there is not a huge amount of seasonality to this location's sunny and cloudy days (though in detail you can see the quasi-periodicity of fall and spring frontal passages). This would at least provide encouragement that even though seasonality dominates total flux, at least it's not an uphill climb against the clouds, too (i.e. still plenty of clear days in the winter -- it would be a different story if winters were also cloudier. Seattle, anyone?)

And I remember that run of sunless days in early April. Something like 4" of rain that week, most of it in two days. For here's that's pretty good.

Good luck. I think we're headed down similar paths for solar.

Mike T., Swampeast MO

Am interested in hourly information because in space heating mode the system will be working on the fly. Space heating mode is "all or nothing". It either meets the full system requirements or is allowed to heat until it's either used for space heating (until exhausted) or for DHW.

BUT, space heating mode can ONLY begin when the actual heat loss of the structure is less than the minimum modulation rate of the boiler--e.g. the burner has to cycle "off" before space heating can begin.

Using my three years of boiler datalogs, I'm identifying "candidate" days. These are days when the boiler is cycling during the hours from say 9 a.m. - 4 p.m. In general the outside temp will average at least 38F during these periods. In a typical winter these make up about 60% of the days when heating is required.

Of course solar intensity varies in these days--from completely overcast to completely sunny. My sizing goal for the panels is to provide 5-7 hours of space heating--depending on time of year--to at least 50% of these days in a typical winter.

When I compare operational datalogs of "candidate" days to the insolation data I notice that either the boiler has been cycling for most of the night (typically 1-2 hour "bursts") or it has been firing continually at or very near minimum modulation all night. In either case, the supply temp will hit it's maximum amount above target about an hour after solar insolation has picked up considerably--usually somewhere between 8:30 a.m. and 10:30 a.m. depending on how rapidly the outside temperature is increasing.

Actual target temperature will be 85F or below (and falling as the outside temp is rising) but the system supply temperature will be about 12-15F higher--the "buffer" provided by my gravity piping is fully charged...

Everything is in my favor. The "buffer" is fully charged. Target temperature is low and falling. Passive solar gain is increasing thus reducing the actual heat loss. The TRVs have reduced flow in the south-facing rooms to nearly nothing as merely the residual heat in the rads is sufficient to meet the loss. On really bright days the south-facing rooms will overshoot by 2-3F for a couple of hours--starting right around this time of day. Solar irradiation is rising rapidly.

On a "typical" day like this, the boiler will not fire--not even "pulse" for 20-40 minutes. ("Pulses" are firings that last only a few seconds at maximum input at 2-10 minute intervals.) Then when it does fire it typically pulses for at least another half hour. Pulses are triggered when the boiler temp drops below 70F but the actual system supply temperature I can measure is quite 5-10F below target--VERY frequently 72F.

If the outside temp rises above 45F or so, the boiler will pulse all day long. If it doesn't the pulses will be interrupted by one or two "bursts" when the boiler fires at minimum input for 1 - 2 hours. These "bursts" AGAIN charge the "buffer" in the gravity mains.

My goal is to virtually eliminate the "pulsing"--even on moderately cloudy days. On sunny but cooler (say averaging 42F) days, I want to eliminate the "bursts" as well. I'll do this by blending in just water heated via solar to prevent the boiler from firing. Even if such cannot meet target temp, the boiler still won't fire until the system temp drops about 10F below target. With system temp below target the house will attempt to cool, but again passive solar gain will operate in my favor as it has reduced the true temperature required in the system. Only when the solar input is utterly inadequate will the boiler have to fire.

See why I'm working with hourly insolation data? Not only do I have to identify "candidate days" (based on hourly daytime temp data and presumed heat loss), but I have to determine if the solar component has enough energy available to at least prevent the pulsing. I also have to estimate any "leftover" heat in the solar tank that while not sufficient in temp for DHW is sufficient to give the system a bit of a head start on some mornings... This will happen because the opposite sequence of events occurs in the afternoon. Passive solar drops off rapidly (increasing the heat load); outside temp falls nearly as quickly; target temperature increases and while the water temp in the solar tank may still be 80F or so, it won't be able to meet system demands. The solar tank will then sit all night but since it's well insulated and not very hot to begin with, loss will be minimal and it will still be adequate for the beginning of the next day should it prove to be a good candidate...

I'd originally hoped that 1 3-meter panel would be sufficient, but since I have to mount it on an adjacent structure with lines running about 30' underground plus 10' down to the ground, I'll have significantly more transmission loss. 2 x 2-meter panels [look] like they're going to work, but am still having problems estimating the possible input.

Mike T., Swampeast MO

Thank you and EVERYONE! Little by little, I'm getting there...

Mike T., Swampeast MO

I've talked with Viessmann numerous times.

The piping and control method I'm going to try is to my (and Viessmann's) knowledge unique. I'll be using the Comfortrol in a way nobody ever intended to provide the bulk of the control. It won't know what it's actually doing, but it won't care as to it, everything will seem "normal". I'll also attempt to use the Vitosolic 200 in a completely non-standard way to provide nearly all of the rest of the control. Why make custom when it's possible to use what's available--even if you're not doing so in the way they were originally intended to be used?

For reasons I can't divulge I'm not at liberty to elaborate on the piping and control. If everything works, it will be really sweet and amazingly simple. If it doesn't work as planned it will still provide solar DHW without any modification.

It [should] be adaptable to some systems using the LLH, provided they have true constant circulation on the secondary side and can operate at quite low temperatures during the daytime hours. Some slight daily daytime setback (the Vitodens way--e.g. setback of space temp via setback of the heating curve) could prove quite beneficial--particularly if the system doesn't use TRVs or FHVs.

Glen

comfortrol -

yes - if one looks carefully at the architecture - there are a few available inputs/outputs. One just has to look sideways at it for a day or two ...

Mike T., Swampeast MO

Didn't mention: www.thermotechs.com was very useful. Gave me the ability to estimate collection efficiency on an hourly basis. THANK YOU!

Of course the delta-t problem is interesting as well. To keep efficiency up I have to keep average temp in the header of the solar collector as low as possible.

Water surrounding the lower coil (providing the solar input) of the dual coil tank should be around 75F. Have to study the heat transfer ability of that coil carefully--thank heaven Viessmann provides GOOD data!--to see how high I can keep the flow rate (thus lowering average temp) without imparing the ability of the coil to transfer its' heat to the tank on a real-time basis.

In a perfect world, fluid will be entering the solar header at 75F or so, leaving at no more than 85F or so with all of the gain instantly transferred in the coil.

Solarstar

Mike ..2 banks of 30 tubes at 50 deg will probably still cook your solar tank in the summer unless you dump the heat since it has to go somewhere. My tank will easily approuch the 200 deg mark. So in my case I need more tank/reserve even with seven people in this house using water. So i'm considering more tank and maybee moving the panels up to 60 deg tilt and leave them year round. Mike ..I'm real interested in your low temp heating results since my radiant stuff is not all connected yet and I nedd to dump this extra heat in spring and fall in my floor but its in the works!! Paul

Constantin

Mike,

have you looked into the retscreen resources? IIRC, their excel-based tools will do everything you're looking for...

Mike T., Swampeast MO

Here's a chart for measured solar radiation here during the same year. Did my best to scale it so that the overall shape would be as similar as possible to your (3x as wide as tall for this part of the data area).

I don't know yet what instrumentation is being used for this day, but have written asking the question.

Peak winter seems to be a bit higher on average than yours (makes sense as you're about 200 miles north), but notice summer. The peaks are significantly lower. Could this be the result of our nearly perpetual haze of humidity in the summer months? Even on "clear" summer days around here the sky is rarely blue like it is in the winter. Instead it's usually an ugly grey.

With a collector angle optimized for early November and late February it sure [looks] like I can get some pretty decent collection at those times while maintaining fairly even overall collector efficiency. While outside temp is certainly lower around the optimal time, the fluid temp in the collector's header when it's supplying space heating should be at its lowest for the year as a whole--rather like solar DHW production in central FL.

Mike T., Swampeast MO

Here's a chart for measured solar radiation here during the same year. Did my best to scale it so that the overall shape would be as similar as possible to your (3x as wide as tall for this part of the data area).

I don't know yet what instrumentation is being used for this day, but have written asking the question.

Peak winter seems to be a bit higher on average than yours (makes sense as you're about 200 miles north), but notice summer. The peaks are significantly lower. Could this be the result of our nearly perpetual haze of humidity in the summer months? Even on "clear" summer days around here the sky is rarely blue like it is in the winter. Instead it's usually an ugly grey.

With a collector angle optimized for early November and late February it sure [looks] like I can get some pretty decent collection at those times while maintaining fairly even overall collector efficiency. While outside temp is certainly lower around the optimal time, the fluid temp in the collector's header when it's supplying space heating should be at its lowest for the year as a whole--rather like solar DHW production in central FL.

CC.Rob_2

daylight

[EDIT. Math error. Back to thinking board.]

Mike T., Swampeast MO

Sorry--made those LOD figures inclusive so they're probably about 1 minute shorter...

Bob Gagnon plumbing and heating

adjustable collector tilt

Mike, consider installing a collector mount that you can tilt it, not side to side every day, but up and down as the seasons change. I have my collectors mounted fixed at about 65 degrees to capture the maximum winter sun, for heating, but with the sun directly overhead in the summer, I collect way less energy than I should be. If I could tilt my collectors to about 45 degrees in the fall and spring I think I could use it for heating a lot more. The steep winter tilt also keeps the snow off the tubes. If you are going away for vacation you could tilt the collector away from the sun, and you might be able to run home before a hailstorm and tilt your collector down. Bob Gagnon

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

dr al

> Didn't mention: www.thermotechs.com was very

> useful. Gave me the ability to estimate

> collection efficiency on an hourly basis. THANK

> YOU!

>

> Of course the delta-t problem is

> interesting as well. To keep efficiency up I

> have to keep average temp in the header of the

> solar collector as low as possible.

>

> Water

> surrounding the lower coil (providing the solar

> input) of the dual coil tank should be around

> 75F. Have to study the heat transfer ability of

> that coil carefully--thank heaven Viessmann

> provides GOOD data!--to see how high I can keep

> the flow rate (thus lowering average temp)

> _I_without_/I_ imparing the ability of the coil

> to transfer its' heat to the tank on a real-time

> basis.

>

> In a perfect world, fluid will be

> entering the solar header at 75F or so, leaving

> at no more than 85F or so with all of the gain

> instantly transferred in the coil.



I started my trip 2 years ago and found that most couldn't give the actual estimated BTU due to solar variability. .

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 preferentioal. (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 (38*). THis is to supply DHW and hot water for radiant heat in the winter and futer ice melt for the side walk (and sumer heat sink)

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

No SUPRISE... I am heating a concrete slab and warm board. Both estimated to run @ 110 and 87 degrees respectivly will creat damand 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.

I'm looking for heating management system to control all three heating systems.

It would need to be active first on time, then on outside temp, then solar collectior temp, then on tank temps, then inside temp, ect.

Any ideas?

dr al

how much tank do you have? Im' putting my tubes on the wall this month @ 65* in Maryland.

jp_2

something totally different!

my design I'm working on is totally different.

first problem is the boiler will be oversized, smallest munchkin still too big. so I need a buffer.

the solar collectors will act as a priority boiler, whatever 'heat' is needed will come from the buffer/solar tank. the outlet of the buffer will have a motorized mixer so it can operate as if it were a modulating boiler.

we can't "hope" for constant weather thoughout the day, so the collectors will heat the buffer tank as high as possible, the mixer will give the temps required by the radiant, as in outdoor reset.

my idea is to use solar whenever possible, not just under modulation minimum levels. this includes DHW.

jp_2

can't count on sun

since it varies so much on weather, I think the only thing you can rely on is averages, daily or monthly averages.

hourly might work today, but not for the rest of the week.

let the solar do as much as it can do, then kick in the boiler.