Opinions on Hot water sources wanted

[AHNC]

Don't even think about that -- you would be very disappointed. Electric heating elements CANNOT be powered by solar panels. Well, in theory they can, but you would need so many solar panels that it is very cost ineffective. We live off-the-grid and know first hand all about living with solar PV panels, and what can and cannot (or should or should not) be powered by them. A grid-tied PV system can offset your electric use, but if you are using inefficient electric appliances, PV won't make a big dent unless you have a lot of solar panels. In winter time you can expect about 1/5 of their rated output. We have 3000+ watts of solar panels and on a rainy day like today their average output was 100-200 watts. PV makes most sense when you are very energy efficient.

We use a Rheem tankless water heater (RTG-84DVP) and have been very happy so far.

Marcus

P.S. Our tankless heater vents to through the wall, and the metal vent pipe also doubles as the air intake pipe. (it's a pipe within a pipe). It keeps operating down to about 1/4 gpm but needs about 1/2 gpm to turn on. The only problem we have it that it gets confused sometimes with preheated water -- it doesn't fire up if the incoming water is too close to its preset temp of 120*. Example: if our preheated water is 110* and the tankless heater doesn't fire up, I may get fluctuating too hot and too cold water in the shower. There are ways to fix that and it's an unusual problem for the manufacturer, so I can't fault them too much.

You have discovered the weakness of solar/tankless combos. What I do on these systems is put a 3-way valve between the solar storage tank and the tankless. The valve is driven by a sensor in the top of the storage tank. When the tank water is sufficiently hot the water by-passes the tankless and goes direct to the tempering valve and the tap. When the tank temp drops to a point, which with your experience you will have no trouble determining, The 3-way will direct the water to the tankless to be heated. The formula to push around is GPM X Delta T X 500 = BTU. Caleffi makes a 3-way valve for that. I always used the Bonomi 3-way with their small elec actuator. Bonomi has the lowest turning torque ball valve I've ever seen. Therefore you can drive them with a $mall(er) actuator. The important point in selecting a tankless to work in these type systems is to get a unit which can fire at low flow and low btu input

 

[muddstopper]

Just a guess, but I doubt the system you described can be bought as a functional, off the shelf system for anywhere near the numbers you provide, nor have I seen anyone describe a DIY on demand system. As for comparing to "off the shelf" solar HW, most numbers I've seen are cost prohibitive without rebates/tax credits.
If I am wrong, please provide a link to your system, as I'd like to buy one, otherwise can't say I see any meaningful contribution to the discussion. Just my opinion, others may disagree.

I have propane, on demand -Tagaki for over 6 years and happy . Wanted to do solar and have the Tagaki as backup, but solar quote was $4k after rebates and only did main part of the house due to length of runs. Actually we have 3 TK Jr at the house and another at the cottage.

David Sent from my iPad using TractorByNet

The Op asked about methods to heat hot water. He listed,
My options are:

Traditional electric hot water heater (40-50 gallon)
High efficiency gas water heater (40-50 gallon)
Tankless gas water heater (8.0 gpm or better) (with or without a small electric to avoid cold slugs through the line)
Hybrid electric heat pump water heater.

I suggested he also consider solar, to which you replied in your opinion my suggestion doesnt add any meaninful contibution to this discussion. You also went on to say that off the shelf solar water heating equipment is cost prohibitive and on this we will disagree. Factory solar water heating kits are available on the market, you said yourself that you have looked into them so I am not going to waste my time looking up websites to confirm whether or not they exsist. I have done little comparison shopping for these type of off the shelf solar water heating systems so I will agree with you that their cost is probably pretty high. And since I havent ran the numbers on their cost of purchase and installation I also cant creditability argue cost effectiviness of installation and operating expenses between all the different kinds of water heating systems currently available. I seriously doubt that you can give a creditable argument against the solar water heating method either.

Now as to my numbers not being anywhere in the range of the $100 I suggested for the cost of a solar collector water heating system, well maynot exactly $100 but well within that range. As someone that looks for bargains and treasures in others discarded materials as well as having a diy mentality. A solar water heating collector can easily be built using commonly discarded building materials which are usually free. What is needed is basic. I use aluminum building flashing, painted flatblack, to help collect the heat from the free sun. With just a little frabication using 2x4s I can fashion a frame. I bend groves in the flashing so that the copper pipe, which I usually have to purchase, lays down in the flashing. I soilder the pipe together to form a ladder shaped cross section for the water to flow thru while being heated. I then encase the frame, containing the flashing and pipes with a clear piece of plexiglass. To the tubing I connect a popoff valve because the water will get hot enought to actually need to vent. From there I run the same cpvc pipe you would use for any hotwater heater, to a discared hotwater heating tank I can pickup most anywhere, usually for free. I take the old hot water heater and cut out the bottom and install coils of copper pipe to act as a heat exchanger and then reweld the bottom back to the tank. I attach my fresh water supply to the coil of pipe inside the tank and then into my regular hotwater heater. My fresh water is completely seperated from the solar heated water stored inside the tank. While I keep the electricity connected to my factory electric heater, I set the thermostat down so that it will only operate in the event that there isnt enough hot water being generated by the solar collector. I can get 130-140 degree hot water (in Jan) from just two 2ftx4ft collectors and that hot water is stored inside the modified hot water heater. This is generally enought that my electric water heater never turns on. My next build calls for more collectors and a larger storage system for whole house heat.

I guess if i counted my time, which isnt much more than what it would take to just connect a new hotwater heater in the first place, I probably do spend a little more that the $100 I first suggested. Reguardless, once the solar system is in place operating cost is virtually zero. So whether or not my contribution to this thread has any meaning, thats up to the other readers to decide. As to whether a solar water heating system can be designed, built, and operated cheaper than any other off the shelf water heating system, To this we are in total disagreement. If you know of a system that cost less than or maybe even a little more than $100 and has less than zero operating cost, you are indeed keeping a very big secret. As to whether my system will pass any building codes, who knows, (and in my case, dont care). My fresh water is kept seperate from the solar heated water so possibility of contamination wouldnt be anymore than it would be if a mouse got in the house and pee'd on the pipes.

 

[dave1949]

As a data reference point, my 4.2 kW grid-tied solar system is providing all of my electricity, including about 100 KW per month for a Rheem/Marathon 55 gal elec. water heater. Granted, we are power misers, and the usage for family will be higher. Our total elec. usage is running around 400 kW per month. AC would be a necessity for the OP, and that would be a big use of power that I don't have.

According to the solar modeling site, Phil., PA is the nearest data location for the OP's town, but he should have very similar solar results as I have here.

I sort of feel like an architect should be asking a client, "What is your energy plan?" if he is going to maximize his value. The home energy scene is changing rapidly. It is probable that a home built today will be expected to be very efficient with a low total energy footprint if it is to maintain its full market value.

Without going overboard, you don't want to build an energy dinosaur.

 

[lutt]

Another note on tankless is that your water has to be pretty much lime free.or you will need a good water softener.I do 30 days straight of keeping up machinery,electrical,diesel,hydraulic,and potable/wash water systems. When I am home on days,the less I have to keep up gives more more time to enjoy my hobbies. LUTT

 

[muddstopper]

As a data reference point, my 4.2 kW grid-tied solar system is providing all of my electricity, including about 100 KW per month for a Rheem/Marathon 55 gal elec. water heater. Granted, we are power misers, and the usage for family will be higher. Our total elec. usage is running around 400 kW per month. AC would be a necessity for the OP, and that would be a big use of power that I don't have.

According to the solar modeling site, Phil., PA is the nearest data location for the OP's town, but he should have very similar solar results as I have here.

I sort of feel like an architect should be asking a client, "What is your energy plan?" if he is going to maximize his value. The home energy scene is changing rapidly. It is probable that a home built today will be expected to be very efficient with a low total energy footprint if it is to maintain its full market value.

Without going overboard, you don't want to build an energy dinosaur.

We use about 1200kw a month. The cost of enough solar panels to provide this much elec is pretty high. We are in the process of designing our retirement home. The site where we will build will have full view of the South so we can incorporate some solar panels for electrical production. My main power supply will be hydro which is much more dependable than solar. My current plans are to use 4 of the modified automobile alternators, each with its own pelton wheel to generate ac power that will be converted to dc for charging the battery bank. We will be doing the net metering, letting the power company store our extra power generation for times when we have higher electrical demands than we can generate. I consider ourself lucky in that we have a sufficient water source, both in total head as well as volume to power the 4 alternators. With net metering, the battery bank is just for times when there are power outages with the power company. We will be the last home on the grid so if power goes out, we will most likely also be in the dark. The battery bank should prevent that from happening and the hydro generation should allow use to operate for several days before putting any real strain on the batteries.

While hydro is probably the cheapest alternative to using the grid, it does pose its own special problems. One is distance from the generation site to the use site. Cant move a creek so one must run wires. Voltage drop over long distances can be overcome. Hydro is constant power 24/7 which is an advantage over PV. PV can be placed close to the house, but PV doesnt do much at nite, or rainy days. PV panels can be damaged in storms and are not easy to fix. Neither is cheap, a 400w alternator is about $300, the pelton wheel another $200. The 400ft or so of Pipe I need will probably also cost about $400. The extra wire needed about $1000. This means I will have about $2200 in a 1.2kw system, not taking into account the net efficiency of the system and not including the batteries which are about $300 each. Still, this size system should pretty much eliminate my power bill saving me $130 a month. Payback is a little over a year, depending on the total number of batteries I choose to use and of course there are still the inverters and converters needed to tie it into the grid. These extra cost could push payback to about 3 years.

I do need someone to check my math. The way i have it figured, each alternator will generate400w and I believe thats per second. If thats the case, 400w x's 60 sec x 60min = 1440,000w per hour or 1440kwh. Multiply that by 24hr = 34,560,000total watts perday. This sounds pretty high to me so I am not sure if I am figureing it correctly. If I am doing the math right I should be able to use less than the 4 alternators I have planned, and still have excess electricity for my total needs. Someone correct me if I am wrong.

 

[dave1949]

mudstopper - The 400 watts is the instantaneous power produced, if it does that for an hour, you will have produced 400 watt-hours. So, per alternator, it would be 400 watts X 24 hours = 9,600 watt hours per day X 30 days per month = 288,000 watt-hours, or 288 kilowatt-hours per month per alternator.

1200 kWh per month / 288 kWh per alternator = 4.16 alternators needed (not allowing for any losses)

You are fortunate to have the hydro resource, go for it. Even if it produces only half your needs, that's a considerable amount.

 

[tkappeler]

Since I am the OP, I will try to respond to some of the points that have come up recently in this thread.

The original question I was asking about is the best method to provide hot water given some constraints. I am interested in solar, but I can't consider it now, so I did not list it in the list of possible choices. There are several factors that come into play that can be easily overlooked as the conversations progress:

1) Aesthetics comes into play. We are building a new home. A lot of consideration has gone into the look of the home. As much as I like to tinker and build things, we do care about not upsetting the look of the home and panels do not fit that bill.

2) We have no desire to be totally off-the-grid. The home is going to be very tight and energy efficient. R26 walls, R42 ceilings, care in blocking drafts, etc. In fact, I am kind of angry that we have to adhere to IECC 2009 for energy efficiency. If I was not doing a lot of the work myself, IECC requirements would easily add 25K to the price of the home. I find it absurd that I am forced to adhere to certain energy standards. I am paying the energy bill, I should be able to say how much I want to tolerate and pay. Don't get me wrong, I would rather keep the money in my pocket instead of the utilities, but it should be my choice. I don't like being told that 50% of my permanent lighting needs to be LED or CFL or what temperature range the thermostat should be at during inspection.

3) Initial Cost. It's easy to say "only a $1000" here and "only $1,800". When you add up all of the pieces to make a system effective, the initial outlay has to factor into the construction loan and and value of that. The costs do not automatically increase the assessed value and therefore the LTV ratio.

4) Payback. Given steep initial costs and decreasing home values, there is little evidence of the payback or value to future buyers. I am not saying there is no payback, only that there does not seem to documentation on how much solar impacts (pos or neg) resale value. It is obvious that there are very passionate and knowledgeable people here regarding solar, however; there is little evidence that the next buyer will care as much as the initial installer and therefore the payback may not be there. Maybe it's a regional thing, but overall, the mid-atlantic is pretty wasteful and I would venture that most people would simply say "meh" to two identical homes that would be on the market except one had solar.

 

[dave1949]

OP - "but it should be my choice"

Unfortunately, you are making choices for everybody when you choose energy. You are not paying the full cost of those choices, they are being socialized to the rest of society. Society has a vested interest in your choices regarding energy use. That vested interest appears in the form of regulations.

One thing you may have noticed about TBN, if you ask for opinions, you will get a wide range of answers. Sometimes, people learn or hear about something that's not on their radar, or they may find they have a view of something that doesn't square with other's experiences. Maybe you get a nugget of info you squirrel away for later use. Whatever you get back in the way of answers, please look at it as friendly offerings.

 

[tkappeler]

OP - "but it should be my choice"

Unfortunately, you are making choices for everybody when you choose energy. You are not paying the full cost of those choices, they are being socialized to the rest of society. Society has a vested interest in your choices regarding energy use. That vested interest appears in the form of regulations.

One thing you may have noticed about TBN, if you ask for opinions, you will get a wide range of answers. Sometimes, people learn or hear about something that's not on their radar, or they may find they have a view of something that doesn't square with other's experiences. Maybe you get a nugget of info you squirrel away for later use. Whatever you get back in the way of answers, please look at it as friendly offerings.

I do place great weight on the information provided by TBN members or I would not have asked. I also have a thick skin too . Nor am I trying to diminish the benefits of alternative energy. The 25K or so of increased costs to the price of a new home would pay for a lot of energy given the difference between on OK system and a great system, especially when you amortize that 25K over 30 years as part of the mortgage. I would simply suggest that I will make the energy savings that I view are cost effective. The green drive cannot be an all or nothing venture. Some is better than nothing and I can only make the choices I can because of a cost/benefit analysis, available funds, timing, etc.

 

[dave1949]

I do place great weight on the information provided by TBN members or I would not have asked. I also have a thick skin too . Nor am I trying to diminish the benefits of alternative energy. The 25K or so of increased costs to the price of a new home would pay for a lot of energy given the difference between on OK system and a great system, especially when you amortize that 25K over 30 years as part of the mortgage. I would simply suggest that I will make the energy savings that I view are cost effective. The green drive cannot be an all or nothing venture. Some is better than nothing and I can only make the choices I can because of a cost/benefit analysis, available funds, timing, etc.

Yes, I should have mentioned the necessity for a thick skin here :laughing:

I hear ya, that is the challenge of green energy. I don't know what all the code requires you to do to meet energy efficiency standards, but the R-26 walls and R-42 ceilings are not onerous or unrealistic. I would say those are minimal standards actually. What is onerous is the permitting and compliance process. It's easy to conflate the two.

I will not add any more stress to your life, building a home may be the second-leading cause of divorce :laughing: