# Solar Links?



## velvetfoot (Oct 5, 2007)

Anyone have some solar energy links for basic knowledge on the subject?
I'm thinking about those for evaluating a house for suitability. 
Thanks.


----------



## Rhone (Oct 5, 2007)

I spent a month researching sites and there isn't just a simple site that gives the basics.  

Are you looking at how to tell if solar is even practical where you are as I know how to do a solar analyses yourself.  You have to physically go to the location you plan on putting the collectors and velvetfoot I seen your roof that place is scary!  If you just want to know some of the finer details like what to expect, what's required, flat plate vs. evac tube, will it work with my current heating system I can give those as well.  I went through all that when I studied if solar was applicable for me (and had to do the solar analyses as my neighbors trees are on the South side).  

Are you looking more at how to do your own solar analyses or looking at more evac vs. flat panel, some of the gotcha's of the installation, rebates, expectations as you already know your house is well suited?  The gotcha that put a temporary hold on my solar installation was they last around 30 years and my roof was on its last legs.  I would've had to take the panels off to replace the roof shortly afterward so, my first step a new roof which drained my funds from getting solar this year.


----------



## velvetfoot (Oct 5, 2007)

Really just to see if it would be practical.
For instance, do they HAVE to point directly south, or what is the loss if not?
Then, there's the slope.
Then PV or Heat (which sounds like what you want).
I have no idea of the life of these things either.
I have to get more of an exact idea of the actual house orientation -compass I guess with some magnetic vs true north correction factor I suppose.
I have no idea where this will take me-probably nowhere.
I've thought about it more in the 70's and 80's, but don't have any idea what's current.
But, I'm thinking there will be more/better incentives coming down the pike.

Yeah that roof...
I haven't been on it yet, despite the recent purchase of a 40' ladder.
I'm thinking Hogwidz' suggestion of a chicken ladder is wise.

I've just now briefly looked at wind, but I've got tall trees around me.
Gee, I wonder how the turbine at the top of a 100' tower gets serviced?
Probably scarier than my roof, lol.


----------



## Rhone (Oct 5, 2007)

Solar panels don't have to point due south, they can be off by up to 15 degrees and only lose 5%, but even if your house is 30 degrees off solar south you lose only 15%.  It's always best to have them go in the same direction as your house (perpendicular or parrallel), you don't want them at some strange angle on your roof it will will look like crap.  To figure out where solar south is (don't use a compass you're looking for solar south not magnetic) put a pole/stake in the ground and level it vertically.  Then go to http://aa.usno.navy.mil/data/docs/RS_OneDay.html  and change it to New York and your location.  Then click the Get Data button and write down when it says "Sun Transit".  That's the time you need to be around this stick at that time and mark its shadow.  That will be exactly solar south.  You get 80-90% of your solar energy between 9-3.  All I'm going to say about PV is to convert sunlight into electricity is about 12% efficient.  If one of the PV cells becomes blocked, efficiency is reduced 50% as that blocked cell becomes a resistor the others have to overcome.  I got a quote for $26,000 to put them on my house and estimated it would reduce my electric bill $9-$11 a month.  Unless for some other reasons, PV is probably not a good investment for most.  The best position, take your lattitude and add 15 degrees for best orientation winter or subtract 15 degrees for best position for summer.  Or, somewhere in between for best Spring & Fall performance.

With solar for hot water & heating there's 2 types.  Evacuated tubes and flat panel.  The flat panels are more efficient per unit, half the cost, and last about twice as long and come in black, or black chrome.  Black chrome lets you get hotter water.  In winter time, when they get covered in snow flat panels allow some heat to escape which melts the snow on them.  Each unit is normally 32 square feet (4x8), and can heat water to about 110-120F at most in winter and sometimes up to 180F in summer.  They work best for either domestic hot water, or to heat a house with radiant floor heating.  They can't heat water hot enough to run through say, someone's current baseboards.  They work on the principle a tub full of hot water has more energy than a kettle full of steaming.  Two 4x8 panels should provide most of ones hot water needs for a family of 2 and should cost around $3,500 for a 2 panel system parts only (not including pipe not installation).  

The other type is evacuated tubes, which are more efficient "per square foot" but that's how they get you they don't have a lot of sq ft.  Each evacuated tube has only 1.0 sq ft collection area and you need 30 of them to net the same energy as a 4x8 flat panel, even compensating for efficiency which is really expensive.  They report being able to "heat" while overcast which, they don't provide hardly anything if the sun isn't out.  Since they're evacuated, no heat escapes out the tubes which has proven to be a problem for some as without heat loss snow won't melt off them.  You also depend heavily on the seals not failing, they're expected to last 20 years.  The one thing they excel at, because they're evacuated they can heat water to hotter temps and will work with forced hot water baseboard systems.  

They're usually not something one can install themselves.  I don't know how much an evac tube system weighs, but each flat panel weighs around 120 lbs empty, not something one can usually haul up a ladder.  Since they last 20-35 years, best not to put them on an old roof.  What makes the most sense is to get the solar hot water system.  NY state offers by far the best solar incentives than anywhere else in the country.  A solar domestic water system should handle 90-100% of your hot water in summer and 20-30% in winter, one should expect a 2 panel system to be around 60-70% yearly.  It's cheap to add another panel, and may be the wiser choice particularly in NY with their crazy incentives.  

It's usually not practical to retrofit a heating system for solar.  A solar house normally has a 2' well insulated thick slab to store the heat and a water tank for domestic hot water use and have radiant floor heating to best take advantage of the solars "a tub full of hot water has a lot more energy than than a kettle full of steaming".  Not to say you can't retrofit, but usually you need to have radiant floor heating and daisy chain storage tanks together (or get a big one).  Most of the models use glycol to prevent freezing, some use a drainback system where that empties at night.


----------



## KeithO (Oct 6, 2007)

http://www.builditsolar.com/

Best bet: Passive solar (no collectors, just proper insulation and thermal mass)
Floors made from at least 8" concrete to store heat.  Best heat retention is black painted water tanks, better than anything else
Good South exposure is a must.
No tall obstructions to the south (especially pines and other evergreens)
For Photovoltiac, nothing that could cast a shadow ANYWHERE on the solar array at any time the sun shines is permissible.  Just a leaf will cause a huge loss from the whole array.
80% of glazing on the south side, 20% on the rest of the house, mostly east and as little possible on the North.
Significant roof overhang on the south side - lets in low winter sun, blocks high summer sun to reduce the heat load when you don't want it.
Windows that open high on the south side and low on the north side to provide natural cooling in summer and use the house as a chimney.

An excellent book that covers all the theory and possibilities is by Edward Mazria  titled "The Passive Solar Energy Book" ISBN 0-87857-238-4


----------



## Burn-1 (Oct 6, 2007)

Velvet I have beat it like a dead horse in the Green Room but tomorrow, (Saturday, October 6) is the national Green Buildings Open House from 10-4, (generally some times may vary). Here are a couple links showing what homes are available for tours in your neck of the woods.

NY Capital Region Green Buildings Open House Locations

MA Berkshires Green Buildings Open House locations

By the looks of it there are several homes and buildings near you. NY has some of the best incentives and rebates for both solar hot water and solar electric installations but as noted your mileage may vary depending on your needs, budget, etc. You can usually ask questions and get hard cost figures from most people and see first-hand what is involved with the whole process. This should be better than any website you might be able to find.


----------



## cbrodsky (Oct 6, 2007)

Rhonemas gave a great summary... in NY State, the incentives are awesome.  We put in a three panel solar hot water system w/120 gallon tank and it's awesome.  I'm still getting 120-140 degree water when the sun is out, and 120 gallons of hot water goes a long time if we get a cloudy day or two.  Electric backup makes sure you're never hurting for hot water, and you can also use it to preheat into an oil furnace if you have one that runs during the winter.

You also don't need to be very picky about sun exposure for hot water as you do with PV.  Our installation is far from ideal - west facing, rather than south, and not ideal angle, but it works great.

If you are using heating oil for hot water, it's a no-brainer at these prices to go to solar hot water.  You'll also do well compared to electric.  On natural gas, you won't save buckets, but it'll help, and then who knows where the natural gas prices are going.

If I had perfect sun exposure, I'd do PV as well, but I have way too many tall trees to make it work for me.  Then again, if I cut those trees, my A/C bill would probably go from $20/month to $200/month in the summer so no real gain there 

-Colin


----------



## rhetoric (Oct 7, 2007)

So tell me more about your installation, Colin.  And the incentives!  Did you DIY or purchase a system?  Tell me more.  Inquiring minds want to know! I'm a NYer too, and I have a BIG southern exposure and a house w/ 7 long-shower-takers.


----------



## cbrodsky (Oct 7, 2007)

rhetoric said:
			
		

> So tell me more about your installation, Colin.  And the incentives!  Did you DIY or purchase a system?  Tell me more.  Inquiring minds want to know! I'm a NYer too, and I have a BIG southern exposure and a house w/ 7 long-shower-takers.



Through the end of next year, you get back 30% or up to $2000 from the Federal government - this comes as a straight credit on your tax return - not a deduction, so it's just like having the government write you a check for it.  Then on top of that, NY State also gives you a 25% rebate - I forget the cap but it's much higher - enough that you won't have to worry about it.

Our installation faces somehwere between west and southwest at a ~30 degree angle.  It typically doesn't see sun until ~10-noon depending on the time of year, and the sun is blocked by trees between ~4-6PM depending on time of year.  My point here is it is far from 100% southern exposure, and that's no problem.  It does help to get good afternoon exposure rather than morning if you have to pick one or the other.

The system uses three 4x8 foot flat plate collectors.  I was thinking vac tube, but supplier said they are not worth the trouble - almost every install he's seen with them ends up with one to two that have broken seals, at which point the efficiency benefit is lost again.  He said a common cause is that the surfaces won't get warm enough to melt snow (because they're so efficient at focusing all heat internally) at which point a homeowner tries to rake off the snow and pops a tube or two.

We use an indirect open loop system.  This means the high pressure house water supply stays in the storage tank - it never goes to the roof.  The storage tank is 120 gallons and looks like a big water heater.  In fact, it is, because it has a backup electric element at the top in case we have a long cloudy period before we fire up the main boiler.  When the boiler is on, we shut down the electric heater and route the output of the solar tank through the main boiler when it's not getting the water to full temp in the winter.  A tube comes from the bottom of that tank and goes into a small 20 gallon tank that contains a heat exchanger.  The other end of that heat exchanger returns to the top of the main storage tank.  The water in this smaller 20 gallon tank is circulated up to the roof only when the panels are warmer than the current water temperature in the bottom of the solar storage tank.  This means even on a marginal day, while you might not make 140 degree water, you might take that 55 degree groundwater and heat it up to 80 on the roof, for example, which means your non-solar heater doesn't work as hard.

I was convinced to go with this "drainback" configuration over an closed loop for many reasons.  Closed loop systems are charged with a non-toxic glycol that sits in the system year round including the roof panels.  This must be maintained and replaced every few years, and that is not a cheap job.  It's also more complicated as you have to get all air out - the drainback system is easy for any homeowner to top-off if needed because you only fill it to the top of the basement tank.  Additionally, as it breaks down, it becomes acidic and is the main cause of failure with these systems.  You also give up some heat transfer efficiency - plain water is better and in theory, you can use less total panel area to get the same results.  In the summer, closed loops can also be a potential problem where fluid overheats in the roof and then you have to circulate to the storage tank to keep it from boiling/breaking down.  But that also has a limit because you can't overheat your storage tank - so you may need a provision to potentially flush hot water down the drain and bring in cool water to keep the glycol from overheating on the roof.  Or, you degrade it much much faster.  A drainback/open-loop system just shuts off and the water comes back to the basement.  (including during a power outage, so no risk of water freezing on your roof)  Believe it or not, it really does get that hot in July/Aug.  We regularly hit 180 degrees in our storage tank at which point I had it programmed to shut down.

The drainback/open-loop system has one main disadvantage - you need a strong pump to get the water up to the roof from the basement - esp. if you have a two-story house.  Our pump is about 150 watts.  A closed-loop pump has the weight of the water coming down from the roof filling the pipes, so it only needs enough power to overcome friction in the lines.  That being said, over the entire year, I have used about $5 worth of electricity to run it - it's such a small amount of power compared to the heat you generate that I don't think it's an issue unless maybe if you live off grid.  You also need to be able to install your system in a way that allows a steady slope on all pipes going to the roof so that it will drain all water out of the roof when it's not running.  This protects you against freezing.  Alternatively, you could use a glycol blend, but then you give up most of the advantages of the drainback system.

The system cost about $8,500 installed before rebates - which is about $4,900 after rebates.  Aside from all the solar equipment and installation, we had them wire in a new electrical circuit for the backup electric heater that may not be needed if swapping out an existing electric unit.  We also have them add a themostatic mixing valve which the builder did not have installed - that required a tangle of copper plumbing work around the boiler.  As to DIY, the way I see it, it's not often you get labor at 50% off (tax credits) so it's one of only two jobs I've ever contracted.  Class-A chimney was the other!

Many people opt to go with a 80 gallon storage tank and two panels - that is a more typical configuration pitched up here as it costs less.  This would have saved us in the neighborhood of $1500 if I recall correctly.  But that third panel and larger tank increases capacity 50% for maybe 20% more expense.

Anyway, hope this helps - compared to solar PV, your ROI is much better and although our installer does both kinds of systems (including just finishing largest residential PV in NY State) he still tells homeowners that they should do thermal first, even though he'll make way more money on a PV install.

-Colin


----------



## cbrodsky (Oct 7, 2007)

rhetoric said:
			
		

> So tell me more about your installation, Colin.  And the incentives!  Did you DIY or purchase a system?  Tell me more.  Inquiring minds want to know! I'm a NYer too, and I have a BIG southern exposure and a house w/ 7 long-shower-takers.



Oh, the other question I didn't get to - how well it works.

We've had the boiler shut down since mid April.  I have had two times that the electric had to run - once in August when we had unusually cool cloudy weather for many days - the last day of that run I needed electric to get the top of the tank up to 120.  And in September, I had a couple days where it was needed.  Right now, it's still providing all the hot water we need but it's been sunny.  I expect that I have another month tops before I will be relying quite a bit on the electric to supplement - instead of reaching 180 on a sunny day, I reach 120-130.  This won't go as far through a cloudy period - a time of year where the large 120 gallons of storage is a big help.  And as the outside temperatures drop, it'll get harder to reach 120 purely off solar.

So at that point, we will likely be starting to turn on the furnace for backup heat, in which case I'll have the tankless coil finish off the water, and I'll turn off the electric element.  But much of the savings I get comes from not having to run the boiler 24x7 to provide water.  Tankless coils are incredibly wasteful to run unless you already have the system on for heat, so that is where a lot of the savings comes from in our case.  On the other hand, someone with a stand-alone natural gas water heater will have a much longer payback period because their system is much cheaper to operate.

Let me know if you have other questions...

-Colin


----------



## rhetoric (Oct 7, 2007)

Schwew!  That was an answer!  Thanks for taking the time and trouble.  I have natural gas water/forced air, so spending 5K for a water heater seems a bit steep.  For now I'm going to start w/ a DIY thermal collector for the lower level of the split (which the woodstove heat doesn't sink down to!). 

Who was your dealer?


----------



## cbrodsky (Oct 8, 2007)

rhetoric said:
			
		

> Schwew!  That was an answer!  Thanks for taking the time and trouble.  I have natural gas water/forced air, so spending 5K for a water heater seems a bit steep.  For now I'm going to start w/ a DIY thermal collector for the lower level of the split (which the woodstove heat doesn't sink down to!).
> 
> Who was your dealer?



You would probably need a long time to come out ahead if you have gas -* assuming* - gas prices stay where they are.  At current oil prices, it's a no-brainer, and for many parts of the country, it's a much smarter move than electric.  Take a look at the usage portion of your gas bill in the summer months and that's what you should eliminate for much of the year as the hot water use is probably the bulk of it.  We have friends on gas and it wasn't all that much.  Once you've paid to have that gas line put in, it's probably smart to use it - have you seen the new system Honda has to fuel a natural gas civic from your home supply?  Super clean car - I would guess NY will offer outstanding incentives for that as well.

We had all of our work done by a local firm that handled all the purchasing as well.  One thing you'll find is that the cost of the parts is not trivial - online, the panels can be around $1K each before rebate.  To get the tax credits, you will need to have it as part of a comprehensive functioning system.

-Colin


----------



## velvetfoot (Oct 8, 2007)

Wow, great info.


----------



## cbrodsky (Oct 8, 2007)

At some point, I would like to get a webpage up with more details/photos - there isn't enough practical info out on the web of real user installs and there is a lot of misperception on how they do with clouds or in a northen climate.  I think there is no better way to find out more about them than see real case studies.

Also thinking of purchasing a hobo datalogger system to measure the production over a year as that would be an interesting set of data.

-Colin


----------



## KeithO (Oct 9, 2007)

Velvetfoot:   The long and the short of it is that the passive and active aspects are not mutually exclusive, one can do both.   But, doing either properly is better done with a new construction with an optimized design and site.   I could do a retrofit at my home, but my recovery would be compromised by the fact that the system would not be optimized, and its generally not something that the average Joe is actually prepared to spend money on when I need to re-sell.

On the other hand, if I buy some land in a place where I want to put down roots, I can think about what I want to do from the time that I pick the site all the way through the design / layout, material choices etc.  And I'm not designing the home for "market appeal", but rather to be as energy efficient as possible, to allow me to have a little fun on what will most likely be a meagre pension.  Bang for the buck, particularly in rural areas where utility connections can cost a fortune, would be photovoltiac.  

One can do many things, but living without electricity is not exactly one I would choose.   A co-generation system using a small IC engine for both heat and electricity (extracting heat from the coolant and exhaust gas) is pretty neat with the only gotcha being that you probably have to "roll your own" unless you're loaded.  At some point in the future this concept will be a lot more common.  The Germans are already doing reforming in basements (Hydrogen from NG) and then powering several homes with a fuel cell.   This is the "ultra high Tech" aproach that is still years out for the mainstream.


----------

