very conceptual solar thermal design

Kevin_in_Denver_2

Before any more money gets wasted on design, please read the NREL report on Zero Energy Homebuilding:

http://www.nrel.gov/docs/fy08osti/43188.pdf

It basically says that a solar thermal system is too complicated for new home construction.

In new construction, passive solar windows, PV, and superinsulation can be employed to eliminate the need for any active collection and storage system.

michael_34

very conceptual solar thermal design

This is for a 2200 sq. ft. house with radiant floor in slab (lower floor only 1200sq ft). There will also be a long covered concrete walk way with radiant tubing (~6x40). The customer is building this house in Ithaca, NY.
I have in the design 80 Sunda Evacuated tubes and three tanks for storage. The owner is not sure if he will use a backup boiler or Geothermo as backup.
My problem is I think 3 120 ga. tanks is to much storage. Can I use the floor as storage and the walkway for a heat dump in the summer? If I can, how much tank storage is needed then?
Thanks.
Michael

hot_rod

why not

hire Siggy, Radiant Engineering, or Cedar Mountain Solar to work up a design. They do solar / radiant all the time and have a lot of experience with state of the art working hybrid systems.

It may be the best money you spend

hr

michael_34

design

I worked for Cedar Mountain for almost 2 years and moved to New york. I was lowly installer then and now I'm also a lowly designer. Thanks for the input.
Michael

Ted_5

heating buffer tank

I would have one of those tanks be heating water only. The key to getting the most out of a buffer tank is the way you load it and unload it. You want the tank to get as hot as possible at the top (high temp zone) and return the coldest water at the bottem(cold zone) and be able to pull of the middle of the tank(warm zone) as the solar is keeping up or producing more then the demand. The buffer heat exchanger for the solar water should be on the bottem.

Ted

hot_rod

There is plenty

of free solar design software available. RET Screen could answer those questions and play all sorts of "what if" options for you. The new heliodyne polySun program could provide answers.

Determine what the output of that arrray is at that location, what operaring temperatures you require.

How much of that output can you use in the summer for DHW loads? Define that number, then the balance needs to go somewhere. Use it or lose it.

Possibly a night time re-radiant, possibly over charge the tanks, maybe an unused zone in the slab.

Any or all of these are options, but first you need to put some numbers down. A good load calc should be the first number. Next define their DHW wants and needs. Everything else could design around.

You will have an un-happy customer if relief valves pop off all summer long

hr

michael_34

Have you used the Heliodyne's Polysun program. Just heard about it a month ago. It would be great to hear some input before purchasing. What heat load calculator are people using. I've been using a test one by a local Cornell Univ. Professor.
Thanks for the help
Michael

Cedar Mountain Boaz

Michael !

Hi Michael! Good to see you're still in the business!

Best of luck,

Boaz

michael_34

Hey Boaz,
How's things there? Tell all hello.
Michael

michael_34

Hi Scott,
I totally agree with you. First you take the steps to make sure this place is tight.
The house I specify is under construction now. It's a south facing. bermed house with passive solar windows, R19 or better walls, with radiant floors (for heating and cooling).
The NREl house is not a clear justification for not using solar thermal collectors for DHW or space heating. From the angle of the collectors (27*) to 96sq ft of collectors for 200 gallons. I would have at least one more collector for the 200 gallons and the least tilt I would have would be 45*. At 27* your only going to collect summer sun, not spring or fall. Thanks for posting that, I will study it more.
Michael

Kal Row

not one cent has been saved with solar to date....

the heat exchanger design breaks the h20/co2 flue gas solution up, so that the h20 can condense (h20 condenses below 212 if alone, at 136 if in solution with co2) - the flue gas flow through the knight's Giannoni HX is too smooth (but it gives them a really good vent distance) - you don’t get a lot of condensation above 140 return water temps - unfortunately for the ultra, the design also eats up the pins sticking into the flow that break up the flue gas solution, as they have been getting a lot of eroded heat exchangers with a pile of aluminum sitting on the bottom – though I don’t know it’s that’s been happening at low temps or high temps, was the gas really high in sulfur dioxide? To be fair, there here are a lot of variables to this

for sure not with photovoltaic’s – maybe hydronic, a big maybe, people that have spent the fortune putting it in, have their egos come up with real creative math, that doesn’t mean we shouldn’t be doing it, we need to anyway, I am doing a solar house in brooklyn ny with inexpensive vac tubes and tanks from china – I back it up with a wall mount Lochinvar knight 210, and I intend to add in windmills to make it truly “carbon 0” - but I don’t think the payoff will be for quite awhile – a long while!!!

ps if it’s well insulated and pumped, there is no such thing as too much storage, on really clear days (what we pilots call “severe clear”), those arrays really cook, and will trip off the high limits, cause they would even flash anti-freeze into steam, unless you can supply an endless amount of relatively cool water no higher than 150 degrees, if you have that – and a really tight house, you can run radiant off the tanks through three cloudy days –
after all the money you spent, wouldn’t you feel stupid if the sun was shining and you array was off, because your tank was too hot??? – I have suggested that people build a house with a sub-basement sized covered pool, that is insulated and sealed to hold solar storage – hey, why just have water in the basement, when you can have “WATER..IN.. THE..BASEMENT”!!!

Bob Gagnon plumbing and heating

It doesn't have to be complicated

Harvest and use those low temperature BTU'S all heating season long. That will make solar hot water much morre efficient. You can have all the passive solar and foam insulation you can get, but you still need to take showers and heat your house at night and during cloudy weather.

Thanks, Bob Gagnon

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Bob Gagnon plumbing and heating

It Doesn't Have To Be That Complicated

Harvest and use those low temperature BTU'S all heating season long. It will make solar hot water a lot more efficient. You can insulate with foam and have all the passive solar you want, but you still need to take showers, and you will need heat in the cloudy weather, and at night.

Thanks, Bob Gagnon



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

steveex

Mr.Kal is that house your doing in brooklyn on east 4th street.

Kal Row

nope, in crown heights...

and am trying to get the apt bld next door to allow me to put vertical spiral windmills to make the whole job "carbon zero"